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  • Other Sources  (922)
  • Geozon Science Media  (760)
  • Inter Research  (89)
  • American Institute of Physics (AIP)
  • Copernicus
  • Oxford Univ. Press
  • 2020-2024  (36)
  • 2010-2014  (886)
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  • 1
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    Trophic ecology and coastal niche partitioning of two sympatric shark species in the Azores (mid-Atlantic) (2024)
    Inter Research
    Details
    Publication Date: 2024-04-15
    Description: The exploitation of marine resources has caused drastic declines of many large predatory fishes. Amongst these, sharks are of major conservation concern due to their high vulnerability to overfishing and their ecological role as top predators. The 2 protected and endangered shark species tope Galeorhinus galeus and smooth hammerhead Sphyrna zygaena use overlapping coastal areas around the globe as essential fish habitats, but data to assess their trophic ecology and niche partitioning are scarce. We provide the first comparative assessment of the trophic ecology, ontogenetic shifts, and niche partitioning of the co-occurring tope and juvenile smooth hammerhead around the Azores Islands, mid-north Atlantic, based on delta 13C, delta 15N, and delta 34S (CNS) stable isotope analysis of muscle tissue of the sharks and their putative prey species. Overall, isotopic niches of both species indicated a reliance on similar resources throughout the sampled sizes (tope: 35-190; smooth hammerhead 54-159 cm total length), with significant ontogenetic shifts. Topes displayed a gradual shift to higher trophic levels and a more generalist diet with increasing size (increasing delta 15N values and isotopic niche volumes, respectively), whereas smooth hammerhead diet shifted towards prey with lower delta 34S at a constant trophic level and a more specialized diet than tope of comparable body size (decreasing delta 34S and constant delta 15N and delta 13C values, respectively). Our results indicate contrasting ontogenetic shifts in delta 13C and delta 34S along with pronounced differences between niche overlap of life stages pointing to intra- and interspecific niche partitioning of habitat and prey.
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  • 2
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    Glimpsing the 2020 spring bloom in the Strait of Georgia (Canada) with autonomous ferry-based sensors (2024)
    Inter Research
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    Publication Date: 2024-07-02
    Description: Spatiotemporal observations are data rich and offer insights into links between ecological patterns and underlying processes. We present fine-scale autonomous observations from repeated ferry transects in the Strait of Georgia (British Columbia, Canada) during the 2020 spring bloom period using a FerryBox system (temperature, salinity, chlorophyll a fluorescence) and a digital inline holographic microscope. Despite instrument cleaning interruptions related to COVID-19 restrictions, 3 periods from late winter (February) to springtime (March and April) contained 14 days of high-quality holograms (〉70 000) capturing 〉10 500 identifiable micro- to mesoplankton using automatic object detection. The ferry set-up provided automatic data storage through Ocean Networks Canada, which also automatized data flagging and guaranteed remote access. The highest-quality holograms repeatedly covered the central and eastern Strait and showed aspects of bloom succession. Fast-growing diatoms (Skeletonema sp.) emerged first, followed by a diverse assemblage including Chaetoceros spp., Ditylum spp., and Eucampia spp., and by April, larger centric cells prevailed. The combined approach captured local suppression of chlorophyll a fluorescence and diatom concentrations in Fraser River plume waters during the freshet, suggesting fine-scale spatial patterns in seasonal planktonic community composition. This work is among the first of its kind to autonomously generate in situ imaging and physicochemical data with spatiotemporal resolution.
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  • 3
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    Body condition of larval roundherring, Gilchristella aestuaria (family Clupeidae), in relation to harmful algal blooms in a warm-temperate estuary (2023)
    Oxford Univ. Press
    Details
    Publication Date: 2024-02-07
    Description: Eutrophication-driven harmful algal blooms (HABs) can have secondary effects on larval fishes that rely on estuaries as nurseries. However, few studies worldwide have quantified these effects despite the global rise in eutrophication. This study presents a novel approach using biochemical body condition analyses to evaluate the impact of HABs on the growth and body condition of the larvae of an estuarine resident fish. Recurrent phytoplankton blooms of Heterosigma akashiwo occur in the warm-temperate Sundays Estuary on the southeast coast of South Africa. The response in body condition and assemblage structure on larval estuarine roundherring (Gilchristella aestuaria) was measured in conjunction with bloom conditions, water quality and zooplanktonic prey and predators. Larvae and early juveniles were sampled during varying intensity levels, duration and frequency of hypereutrophic blooms. This study demonstrated that extensive HABs could significantly impact larval roundherring, G. aestuaria, by decreasing larval nutritional condition and limiting their growth, resulting in poor grow-out into the juvenile phase. Poor condition and growth may likely affect recruitment success to adult populations, and since G. aestuaria is an important forage fish and zooplanktivore, poor recruitment will hold consequences for estuarine food webs.
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  • 4
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    Carbon budgets of copepod communities in the northern Humboldt Current System off Peru (2023)
    Inter Research
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    Publication Date: 2024-02-07
    Description: Abundance, biomass and respiration rates of dominant medium- to larger-sized copepod species (ML class) from the upwelling system off Peru (8.5-16°S) were determined along with their carbon ingestion and egestion rates. Small copepods (S class) were included for comparisons of community rates. Overall, abundance/biomass was highest in the upper 50 m and decreased with depth and thus also community ingestion and egestion. Ingestion of the ML class (0-50 m) in shelf regions (14-515 mg C m -2 d -1 ) was lower in the south compared to the north and central study areas, while their offshore ingestion (11-502 mg C m -2 d -1 ) was comparable across regions (8.5-16°S). Ingestion rates (0-50 m) of the S class were in a range similar to those of the ML class in shelf regions (100-417 mg C m -2 d -1 ) but were higher offshore (177-932 mg C m -2 d -1 ). Calanus chilensis and the S class contributed most to total ingestion in the north, while in the south, Centropages brachiatus had the highest community ingestion aside from the S class. Egestion varied from 3-155 mg C m -2 d -1 for the ML class and 30-280 mg C m -2 d -1 for the S class. The high community rates highlight the crucial role of both size classes for carbon budgets in the northern Humboldt Current System off Peru and indicate that the ML class may enhance passive vertical carbon flux, whereas the S class may support carbon remineralization rates in surface waters.
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  • 5
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    Oceanographic structuring of the mucous-mesh grazer community in the Humboldt Current off Peru (2023)
    Inter Research
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    Publication Date: 2024-03-25
    Description: The Humboldt Upwelling System (HUS) supports high levels of primary production and has the largest single-stock fishery worldwide. The high fish production is suggested to be related to high trophic transfer efficiency in the HUS. Mucous-mesh grazers (pelagic tunicates and gastropods) are mostly of low nutritious value and might reduce trophic transfer efficiency when they are locally abundant. Unfortunately, little is known about the spatial dynamics of mucous-mesh grazers from Peruvian waters, limiting our understanding of their potential ecological role(s). We provide a spatial assessment of mucous-mesh grazer abundance from the Peruvian shelf in austral summer 2018/2019 along six cross-shelf transects spanning from 8.5 to 16° S latitude. The community was dominated by appendicularians and doliolids. Salps occurred in high abundance but infrequently and pelagic gastropods were mostly restricted to the North. At low latitudes, the abundance of mucous-mesh grazers was higher than some key species of crustacean mesozooplankton. Transects in this region had stronger Ekman-transport, higher temperature, lower surface turbidity and a broader oxygenated upper water layer compared to higher-latitude transects. Small-scale lateral intrusions of upwelled water were potentially associated with high abundances of doliolids at specific stations. The high abundance and estimated ingestion rates of mucous-mesh grazers in the northern HUS suggest that a large flux of carbon from lower trophic levels is shunted to tunicates in recently upwelled water masses. The data provide important information on the ecology of mucous mesh grazers and stress the relevance to increase research effort on investigating their functioning in upwelling systems.
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  • 6
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    Developing an Observing Air–Sea Interactions Strategy (OASIS) for the global ocean (2023)
    Oxford Univ. Press
    Details
    Publication Date: 2024-04-08
    Description: The Observing Air–Sea Interactions Strategy (OASIS) is a new United Nations Decade of Ocean Science for Sustainable Development programme working to develop a practical, integrated approach for observing air–sea interactions globally for improved Earth system (including ecosystem) forecasts, CO2 uptake assessments called for by the Paris Agreement, and invaluable surface ocean information for decision makers. Our “Theory of Change” relies upon leveraged multi-disciplinary activities, partnerships, and capacity strengthening. Recommendations from 〉40 OceanObs’19 community papers and a series of workshops have been consolidated into three interlinked Grand Ideas for creating #1: a globally distributed network of mobile air–sea observing platforms built around an expanded array of long-term time-series stations; #2: a satellite network, with high spatial and temporal resolution, optimized for measuring air–sea fluxes; and #3: improved representation of air–sea coupling in a hierarchy of Earth system models. OASIS activities are organized across five Theme Teams: (1) Observing Network Design & Model Improvement; (2) Partnership & Capacity Strengthening; (3) UN Decade OASIS Actions; (4) Best Practices & Interoperability Experiments; and (5) Findable–Accessible–Interoperable–Reusable (FAIR) models, data, and OASIS products. Stakeholders, including researchers, are actively recruited to participate in Theme Teams to help promote a predicted, safe, clean, healthy, resilient, and productive ocean.
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  • 7
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    Combined effects of salinity and trematode infections on the filtration capacity, growth and condition of mussels (2022)
    Inter Research
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    Publication Date: 2024-02-07
    Description: The blue mussel (Mytilus species complex) is an important ecosystem engineer, and salinity can be a major abiotic driver of mussel functioning in coastal ecosystems. However, little is known about the interactive effects of abiotic drivers and trematode infection. This study investigated the combined effects of salinity and Himasthla elongata and Renicola roscovita metacercarial infections on the filtration capacity, growth, and condition of M. edulis from the Baltic Sea. In a laboratory experiment, groups of infected and uninfected mussels were exposed to a wide range of salinities (6−30, in steps of 3) for 1 mo. Shell growth was found to be positively correlated with salinity and optimal at 18−24 at the end of the experiment, imposed by constraints in shell calcification under lower salinities. Mussel shell growth was not affected by H. elongata infection. While salinity had only a minor effect on tissue dry weight, infected mussels had a significantly lower tissue dry weight than uninfected mussels. Most interestingly, the combination of salinity and trematode infections negatively affected the mussels’ condition indices at lower salinity levels (6 and 9), suggesting that trematode infections are more detrimental to mussels when combined with freshening. A significant positive effect of salinity on mussel filtration was found, with an initial optimum at salinity 18 shifting to 18−24 by the end of the experiment. These findings indicate that salinity and parasite infections act as synergistic stressors for mussels, and enhance the understanding of potential future ecosystem shifts under climate change-induced freshening in coastal waters.
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  • 8
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    Food fall-specific scavenging response to experimental medium-sized carcasses in the deep sea (2022)
    Inter Research
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    Publication Date: 2024-02-07
    Description: In the deep sea, benthic communities largely depend on organic material from the overlying water column for food. The remains of organisms on the seafloor (food falls) create areas of organic enrichment that attract scavengers. The scavenging rates and communities of food falls of medium-sized squid, fish and jellyfish (1-100 cm) are poorly known. To test our hypothesis that scavenging responses are specific for different food falls, we deployed camera landers baited with squid, jellyfish and fish for 9 to 25 h at 1360 to 1440 m in the southern Norwegian Sea. Image analysis of 8 deployments showed rapid food fall consumption (20.3 +/- 1.4 [SD] to 31.6 +/- 3.7 g h(-1)) by an amphipod-dominated scavenging community that was significantly different between the food fall types. Fish and squid carcasses were mostly attended by amphipods of the genus Eurythenes. Smaller unidentified amphipods dominated the jellyfish experiments together with brittle stars (cf. Ophiocten gracilis) and decapod shrimps (cf. Bythocaris spp.); the latter only occurred on jellyfish carcasses. The removal time for jellyfish (similar to 17 h) was almost twice as long as that for squid and fish (9-10 h). The maximum scavenger abundance was significantly higher on fish carcasses than on jellyfish and squid. The times at which abundances peaked were similar for jellyfish and fish (after 8-9 h) but significantly sooner for squid (3.00 +/- 0.35 h). Our results, although based on a small number of experiments, demonstrate differences in scavenging responses between food fall species, suggesting tight coupling between the diversity and ecology of benthic scavenging communities in the Norwegian Sea.
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  • 9
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    Diversity of taxon-specific traits of seasonally distinct unicellular eukaryotic assemblages in a eutrophic coastal area with marked plankton blooms (2022)
    Inter Research
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    Publication Date: 2024-02-07
    Description: In this work, we focused on the functional characterization of unicellular eukaryotic assemblages that had previously been taxonomically characterized by 18S rRNA gene amplicon sequencing in a eutrophic coastal site with marked plankton blooms. Biological traits of different functional groups were assigned to the retrieved operational taxonomic units (OTUs). The traits included size, trophic strategy, the presence of spines, mucilage production, colony formation, motility, spore formation, and potential harmfulness. Functional diversity indices were calculated and compared to analogous taxonomic diversity indices, indicating a strong positive coupling of richness and dominance and a negative coupling of evenness, even at a low taxonomic resolution (at the family/genus/species level). Biological trait trade-offs and co-occurrences of specific traits were evident during the succession of plankton blooms. The trophic strategy dominating in the assemblages frequently alternated between autotrophy, mixotrophy, and a few recorded cases of parasitism. Given that there was no indication of nutrient limitation, we suggest that biotic pressures force marine eukaryotes to exploit narrow niches by adopting specific strategies/traits that favour their survival. These traits act by increasing resource acquisition potential and via predator avoidance. This leads to a unique succession of blooms in the system, characterized by adaptations of the bloom taxa that are a direct response to the preceding assemblage.
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  • 10
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    Using the VEMCO Positioning System (VPS) to explore fine-scale movements of aquatic species: applications, analytical approaches and future directions (2022)
    Inter Research
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    Publication Date: 2024-02-07
    Description: Recent advancements in telemetry have redefined our ability to quantify the fine-scale movements of aquatic animals and derive a mechanistic understanding of movement behaviours. The VEMCO Positioning System (VPS) is a fine-scale commercial positioning system used to generate highly accurate semi-continuous animal tracks. To date, VPS has been used to study 86 species, spanning 25 taxonomic orders. It has provided fine-scale movement data for critical life stages, from tracking day-old turtle hatchlings on their first foray into the sea to adult fish returning to natal rivers to spawn. These high-resolution tracking data have improved our understanding of the movements of species across environmental gradients within rivers, estuaries and oceans, including species of conservation concern and commercial value. Existing VPS applications range from quantifying spatio-temporal aspects of animal space use and key aspects of ecology, such as rate of movement and resource use, to higher-order processes such as interactions among individuals and species. Analytical approaches have seen a move towards techniques that incorporate error frameworks such as autocorrelated kernel density estimators for home range calculations. VPS technology has the potential to bridge gaps in our fundamental understanding of fine-scale ecological and physiological processes for single and multi-species studies under natural conditions. Through a systematic review of the VPS literature, we focus on 4 principle topics: the diversity of species studied, current ecological and ecophysiological applications and data analysis techniques, and we highlight future frontiers of exploration.
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  • 11
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    Anisotropic velocity models for (3D) seismic imaging ofthe Lower Seve Nappe in Jämtland, Sweden (2022)
    Oxford Univ. Press
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    Publication Date: 2024-02-07
    Description: Strong anisotropy of seismic velocity in the Earth’scrust poses serious challenges for seismic imaging. Where in situ seismic properties are not available the anisotropy can be determined from velocity analysis of surface and borehole seismic profiles. This is well established for dense, long-offset reflection seismic data. However, it is unknown how applicable this approach is for sparse seismic reflection data with low fold and short offsets in anisotropic metamorphic rocks. Here we show that anisotropy parameters can be determined from a sparse 3D data set at the COSC-1 borehole site in the Swedish Caledonides and that the results agree well with the seismic anisotropy parameters determined from seismic laboratory measurements on core samples. Applying these anisotropy parameters during 3D seismic imaging improves the seismic image of the high amplitude reflections especially in the vicinity of the lower part of the borehole. Strong reflections in the resulting seismic data show good correlation with the borehole-derived lithology. Our results aid the interpretation and extrapolation of the seismic stratigraphy of the Lower Seve Nappe in Jämtland and other parts in the Caledonides.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 12
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    Oceanic drivers of juvenile sea turtle strandings in the UK (2022)
    Inter Research
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    Publication Date: 2024-02-07
    Description: Juvenile sea turtles can disperse thousands of kilometers from nesting beaches to oceanic development habitats, aided by ocean currents. In the North Atlantic, turtles dispersing from American beaches risk being advected out of warm nursery grounds in the North Atlantic Gyre into lethally cold Northern European waters (e.g. around the United Kingdom). We used an ocean model simulation to compare simulated numbers of turtles that were advected to cold waters around the UK with observed numbers of turtles reported in the same area over ~5 decades. Rates of virtual turtles predicted to encounter lethal temperatures (≤10 and 15°C, mean 19% ± 2.7) and reach the UK were consistently low (median 0.83%, lower quartile 0.67%, upper quartile 1.02%), whereas there was high inter-annual variability in the numbers of dead or critically ill turtles reported in the UK. Generalized additive models suggest inter-annual variability in the North Atlantic Oscillation (NAO) index to be a good indicator of annual numbers of turtle strandings reported in the UK. We demonstrate that NAO variability drives variability in the dispersion scenarios of juvenile turtles from key nesting regions into the North Atlantic. Coastal effects, such as the number of storms and mean sea surface temperatures in the UK were significant but weak predictors, with a weak effect on turtle strandings. Further understanding how changing environmental conditions such as NAO variability and storms affect the fate of juvenile turtles is vital for understanding the distribution and population dynamics of sea turtles.
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  • 13
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    GLODAPv2.2022: the latest version of the global interior ocean biogeochemical data product (2022)
    Copernicus
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    Publication Date: 2024-02-07
    Description: The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface-to-bottom ocean biogeochemical bottle data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of seawater samples. GLODAPv2.2022 is an update of the previous version, GLODAPv2.2021 (Lauvset et al., 2021). The major changes are as follows: data from 96 new cruises were added, data coverage was extended until 2021, and for the first time we performed secondary quality control on all sulphur hexafluoride (SF6) data. In addition, a number of changes were made to data included in GLODAPv2.2021. These changes affect specifically the SF6 data, which are now subjected to secondary quality control, and carbon data measured onboard the RV Knorr in the Indian Ocean in 1994–1995 which are now adjusted using CRM measurements made at the time. GLODAPv2.2022 includes measurements from almost 1.4 million water samples from the global oceans collected on 1085 cruises. The data for the now 13 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, CCl4, and SF6) have undergone extensive quality control with a focus on systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but converted to World Ocean Circulation Experiment (WOCE) exchange format and (ii) as a merged data product with adjustments applied to minimize bias. For the present annual update, adjustments for the 96 new cruises were derived by comparing those data with the data from the 989 quality controlled cruises in the GLODAPv2.2021 data product using crossover analysis. SF6 data from all cruises were evaluated by comparison with CFC-12 data measured on the same cruises. For nutrients and ocean carbon dioxide (CO2) chemistry comparisons to estimates based on empirical algorithms provided additional context for adjustment decisions. The adjustments that we applied are intended to remove potential biases from errors related to measurement, calibration, and data handling practices without removing known or likely time trends or variations in the variables evaluated. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 μmol kg-1 in dissolved inorganic carbon, 4 μmol kg-1 in total alkalinity, 0.01–0.02 in pH (depending on region), and 5 % in the halogenated transient tracers. The other variables included in the compilation, such as isotopic tracers and discrete CO2 fugacity (fCO2), were not subjected to bias comparison or adjustments.
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  • 14
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    Microbiota associated with echinoid eggs and the implications for maternal provisioning (2022)
    Inter Research
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    Publication Date: 2024-02-07
    Description: Mothers impact the survival and performance of their offspring through the resources they provision, and the degree of maternal investment in an individual offspring can be broadly estimated by egg size for organisms that lack parental care. Animals may also actively maintain symbiotic partnerships with microorganisms through the germ line, but whether microbes are a fundamental component of maternal provisioning is an untested hypothesis in evolutionary symbiosis. We present a preliminary test of this by comparing the egg-associated microbiota of ten sea urchin species with ecological factors known to influence egg size. We found that the microbiota associated with sea urchin eggs had a phylogenetic signal in both composition and richness, which varied between years but not between individuals or within a clutch. Moreover, we found a negative correlation between microbiome richness and taxonomic dominance, and that community diversity covaried with egg size and energetic content but not with pelagic larval duration or latitude. These data suggest that there are multiple parallels between the ecological factors that govern changes in egg size and microbiome composition and diversity, implying that microbial symbionts may be another constituent potentially provided by the mother.
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  • 15
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    Active ocean–continent transform margins: seismic investigation of the Cayman Trough-Swan Island ridge-transform intersection (2022)
    Oxford Univ. Press
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    Publication Date: 2024-02-07
    Description: The southern boundary of the Cayman Trough in the Caribbean is marked by the Swan Islands transform fault (SITF), which also represents the ocean-continent transition of the Honduras continental margin. This is one of the few places globally where a transform continental margin is currently active. The CAYSEIS experiment acquired an ∼165-km-long seismic refraction and gravity profile (P01) running across this transform margin, and along the ridge-axis of the Mid-Cayman Spreading Centre (MCSC) to the north. This profile reveals not only the crustal structure of an actively evolving transform continental margin, that juxtaposes Mesozoic-age continental crust to the south against zero-age ultraslow spread oceanic crust to the north, but also the nature of the crust and uppermost mantle beneath the ridge-transform intersection (RTI). The traveltimes of arrivals recorded by ocean-bottom seismographs (OBSs) deployed along-profile have been inverse and forward modelled, in combination with gravity modelling, to reveal an ∼25-km-thick continental crust that has been continuously thinned over a distance of ∼65 km to ∼10 km adjacent to the SITF, where it is juxtaposed against ∼3-4-km-thick oceanic crust. This thinning is primarily accommodated within the lower crust. Since Moho reflections are only sparsely observed, and, even then, only by a few OBSs located on the continental margin, the 7.5 km s-1 velocity contour is used as a proxy to locate the crust-mantle boundary along-profile. Along the MCSC, the crust-mantle boundary appears to be a transition zone, at least at the seismic wavelengths used for CAYSEIS data acquisition. Although the traveltime inversion only directly constrains the upper crust at the SITF, gravity modelling suggests that it is underlain by a higher density (〉3000 kg m-3) region spanning the width (∼15 km) of its bathymetric expression, that may reflect a broad region of metasomatism, mantle hydration or melt-depleted lithospheric mantle. At the MCSC ridge-axis to the north, the oceanic crust appears to be forming in zones, where each zone is defined by the volume of its magma supply. The ridge tip adjacent to the SITF is currently in a magma rich phase of accretion. However, there is no evidence for melt leakage into the transform zone. The width and crustal structure of the SITF suggests its motion is currently predominantly orthogonal to spreading. Comparison to CAYSEIS Profile P04, located to the west and running across-margin and through 10 Ma MCSC oceanic crust, suggests that, at about this time, motion along the SITF had a left-lateral transtensional component, that accounts for its apparently broad seabed appearance westwards.
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  • 16
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    Phytoplankton nutritional quality is altered by shifting Si:N ratios and selective grazing (2021)
    Oxford Univ. Press
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    Publication Date: 2024-02-07
    Description: Diatoms often dominate phytoplankton in temperate, polar and upwelling regions. Decreases in silicate availability or silicon to nitrogen (Si:N) ratios may induce silicon limitation in diatoms and lower their proportion within phytoplankton communities. The effects of such changes on the nutritional quality of phytoplankton are not well understood. To examine how changing Si:N ratios affect plankton nutritional value, we applied a range of Si:N ratios on a natural plankton community and manipulated grazing pressure to assess top-down effects of copepod selective grazing. Diatom proportion in phytoplankton increased with increasing Si:N ratios and so did phytoplankton nutritional quality in terms of major fatty acid concentrations, such as polyunsaturated fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids. However, stoichiometric quality (carbon to nitrogen and carbon to phosphorus ratios), DHA:EPA and omega 3:6 (omega 3:omega 6) ratios declined with increasing Si:N ratios, suggesting that proportions between essential compounds in copepod diet may be more favorable in lowered Si:N ratios. Copepods had a negative effect on DHA contents, DHA:EPA and omega 3:omega 6 ratios, indicating possible selective grazing on more nutritious plankton. Our findings show that declining silicate concentrations can affect stoichiometric and biochemical quality of phytoplankton, which copepods can also moderate by selective grazing.
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  • 17
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    Water Balance and Desiccation Tolerance of the Invasive South American Tomato Pinworm (2021)
    Oxford Univ. Press
    Details
    Publication Date: 2024-02-07
    Description: Temperature and dehydration stress are two major co-occurring environmental stressors threatening the physiology, biochemistry, and ecology of insects. As such, understanding adaptive responses to desiccation stress is critical for predicting climate change impacts, particularly its influence on insect invasions. Here, we assessed water balance and desiccation resistance of the invasive Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae), and infer how eco-physiology shapes its niche. We measured basal body water and lipid content, water loss rates (WLRs), and desiccation resistance in larvae (second to fourth instars) and adults. Body -water, -lipid, and WLRs significantly varied across life stages. Second instars recorded the lowest while fourth instars exhibited the highest body water and lipid content. Adult body water and lipid content were higher than second and third instars and lower than fourth instars while proportion of body water and lipid contents were highest in adults and second larval instars respectively. Water loss rates were significantly highest in fourth-instar larvae compared to other life stages, but differences among stages were less apparent at longer exposure durations (48 h). Desiccation resistance assays showed that second instars had greatest mortality while fourth-instar larvae and adults were the most desiccation tolerant. Our results show that T. absoluta fourth-instar larvae and adults are the most resilient developmental stages and potentially contribute most to the invasion success of the pest in arid environments. Incorporation of these species-specific eco-physiological traits in predictive models can help refine invasive species potential spread under changing climates.
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    Five centuries of cod catches in Eastern Canada (2021)
    Oxford Univ. Press
    Details
    Publication Date: 2024-02-07
    Description: The fishery for Northern Atlantic cod (Gadus morhua) off Newfoundland and Labrador, Eastern Canada, presents the most spectacular case of an exploited stock crashed in a few decades by an industrial bottom trawl fishery under a seemingly sophisticated management regime after half a millennium of sustainable fishing. The fishery, which had generated annual catches of 100000 to 200000 tonnes from the beginning of the 16th century to the 1950s, peaked in 1968 at 810000 tonnes, followed by a devastating collapse and closure 24 years later. Since then, stock recovery may have been hindered by premature openings, with vessels targeting the remains of the cod population. Previous research paid little attention towards using multicentury time series to inform sustainable catches and recovery plans. Here, we show that a simple stock assessment model can be used to model the cod population trajectory for the entire period from 1508 to 2019 for which catch estimates are available. The model suggests that if fishing effort and mortality had been stabilized in the 1980s, precautionary annual yields of about 200000 tonnes could have been sustained. Our analysis demonstrates the value of incorporating prior knowledge to counteract shifting baseline effects on reference points and contemporary perceptions of historical stock status.
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    Effects of nutrient enrichments on oligotrophic phytoplankton communities: a mesocosm experiment near Hawai‘i, USA (2021)
    Inter Research
    Details
    Publication Date: 2024-02-07
    Description: A large-volume mesocosm-based nutrient perturbation experiment was conducted off the island of Hawai‘I, USA, to investigate the response of surface ocean phytoplankton communities to nutrient addition of macronutrients, trace metals, and vitamins and to assess the feasibility of using mesocosms in the open ocean. Three free-drifting mesocosms (~60 m3) were deployed: one mesocosm served as a control (no nutrient amendments), a second (termed +P) was amended with nitrate (N), silicate (Si), phosphate (P) and a trace metal + vitamin mixture, and a third (termed -P) was amended with N, Si, and a trace metal + vitamin mixture but no P. These mesocosms were unreplicated due to logistical constraints and hence differences between treatments are qualitative. After 6 d, the largest response of the phytoplankton community was observed in the +P mesocosm where chlorophyll a (chl a) and 14C-based primary production were 2–3× greater than the -P mesocosm and 4–6× greater than the control. Comparison between mesocosm and ‘microcosm’ incubations (20 l) revealed differences in the magnitude and timing of production and marked differences in community structure with a reduced response of diatoms in microcosm treatments. Notably, we also observed pronounced declines in Prochlorococcus populations in all treatments: although these were greater in microcosms (up to 99%). Overall, this study confirmed the feasibility of deploying free-drifting mesocosms in the open ocean as a potentially powerful tool to investigate ecological impacts of nutrient perturbations and constitutes a valuable first step towards scaling plankton manipulation experiments.
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    High trophic plasticity in the mixotrophic Mastigias papua-Symbiodiniaceae holobiont: implications for the ecology of zooxanthellate jellyfishes (2021)
    Inter Research
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    Publication Date: 2024-02-07
    Description: The trophic ecology of mixotrophic, zooxanthellate jellyfishes potentially spans a wide spectrum between autotrophy and heterotrophy. However, their degree of trophic plasticity along this spectrum is not well known. To better characterize their trophic ecology, we sampled the zooxanthellate medusa Mastigias papua in contrasting environments and sizes in Palau (Micronesia). We characterized their trophic ecology using isotopic (bulk δ13C and δ15N), elemental (C:N ratios), and fatty acid compositions. The different trophic indicators were correlated or anti-correlated as expected (Pearson’s correlation coefficient, rP 〉 0.5 or 〈 -0.5 in 91.1% of cases, p 〈 0.05), indicating good agreement. The sampled M. papua were ordered in a trophic spectrum between autotrophy and heterotrophy (supported by decreasing δ13C, C:N, proportion of neutral lipid fatty acids (NLFA:TLFA), n-3:n-6 and increasing δ15N, eicosapentaenoic acid to docosahexaenoic acid ratio (EPA:DHA)). This trophic spectrum was mostly driven by sampling location with little influence of medusa size. Moreover, previous observations have shown that in a given location, the trophic ecology of M. papua can change over time. Thus, the positions on the trophic spectrum of the populations sampled here are not fixed, suggesting high trophic plasticity in M. papua. The heterotrophic end of the trophic spectrum was occupied by non-symbiotic M. papua, whereas the literature indicates that the autotrophic end of the spectrum corresponds to dominant autotrophy, where more than 100% of the carbon requirement is obtained by photosynthesis. Such high trophic plasticity has critical implications for the trophic ecology and blooming ability of zooxanthellate jellyfishes
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    Impaired larval development at low salinities could limit the spread of the non-native crab Hemigrapsus takanoi in the Baltic Sea (2021)
    Inter Research
    Details
    Publication Date: 2024-02-07
    Description: The Asian shore crab Hemigrapsus takanoi, native to the northwest Pacific Ocean, was recently discovered in Kiel Fjord (southwestern Baltic Sea). In laboratory experiments, we tested the salinity tolerance of H. takanoi across 8 levels (0 to 35) and across 3 life history stages (larvae, juveniles and adults) to assess its potential to invade the brackish Baltic Sea. Larval development at different salinities was monitored from hatching to the megalopa stage, while survival and feeding of juveniles and adults were assessed over 17 d. Larvae of H. takanoi were able to complete their development to megalopa at salinities 〉= 20 and the time needed after hatch to reach this stage did not differ between salinities of 20, 25, 30 and 35. At a salinity of 15, larvae still reached the last zoea stage (zoea V), but development to the megalopa stage was not completed. All juveniles and adults survived at salinities from 5 to 35. Feeding rates of juveniles increased with increasing salinity across the entire salinity range. However, feeding rates of adults reached their maximum between salinities of 15 and 35. Our results indicate that both juveniles and adults of H. takanoi are euryhaline and can tolerate a wide range of salinities, at least for the time period tested (2 wk). However, larval development was impaired at salinities lower than 20, which may prevent the spread of H. takanoi into the Baltic Proper.
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    Establishment of Host–Algal Endosymbioses: Genetic Response to Symbiont Versus Prey in a Sponge Host (2021)
    Oxford Univ. Press
    Details
    Publication Date: 2024-02-07
    Description: The freshwater sponge Ephydatia muelleri and its Chlorella-like algal partner is an emerging model for studying animal: algal endosymbiosis. The sponge host is a tractable laboratory organism, and the symbiotic algae are easily cultured. We took advantage of these traits to interrogate questions about mechanisms that govern the establishment of durable intracellular partnerships between hosts and symbionts in facultative symbioses. We modified a classical experimental approach to discern the phagocytotic mechanisms that might be co-opted to permit persistent infections, and identified genes differentially expressed in sponges early in the establishment of endosymbiosis. We exposed algal-free E. muelleri to live native algal symbionts and potential food items (bacteria and native heat-killed algae), and performed RNA-Seq to compare patterns of gene expression among treatments. We found a relatively small but interesting suite of genes that are differentially expressed in the host exposed to live algal symbionts, and a larger number of genes triggered by host exposure to heat-killed algae. The upregulated genes in sponges exposed to live algal symbionts were mostly involved in endocytosis, ion transport, metabolic processes, vesicle-mediated transport, and oxidation–reduction. One of the host genes, an ATP-Binding Cassette transporter that is downregulated in response to live algal symbionts, was further evaluated for its possible role in the establishment of the symbiosis. We discuss the gene expression profiles associated with host responses to living algal cells in the context of conditions necessary for long-term residency within host cells by phototrophic symbionts as well as the genetic responses to sponge phagocytosis and immune-driven pathways.
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    Marine sponges maintain stable bacterial communities between reef sites with different coral to algae cover ratios (2021)
    Oxford Univ. Press
    Details
    Publication Date: 2024-02-07
    Description: Marine sponges play a major ecological role in recycling resources on coral reef ecosystems. The cycling of resources may largely depend on the stability of the host-microbiome interactions and their susceptibility to altered environmental conditions. Given the current coral to algal phase shift on coral reefs, we investigated whether the sponge-associated bacterial communities of four sponge species, with either high or low microbial abundances (HMA and LMA), remain stable at two reefs sites with different coral to algae cover ratios. Additionally, we assessed the bacterial community composition of two of these sponge species before and after a reciprocal transplantation experiment between the sites. An overall stable bacterial community composition was maintained across the two sites in all sponge species, with a high degree of host-specificity. Furthermore, the core bacterial communities of the sponges remained stable also after a 21-day transplantation period, although a minor shift was observed in less abundant taxa (〈 1%). Our findings support the conclusion that host identity and HMA-LMA status are stronger traits in shaping bacterial community composition than habitat. Nevertheless, long-term microbial monitoring of sponges along with benthic biomass and water quality assessments are needed for identifying ecosystem tolerance ranges and tipping points in ongoing coral reef phase shifts.
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    Ecology of Moroteuthopsis longimana at the sub-Antarctic Prince Edward Islands, revealed through stable isotope analysis of squid beaks (2021)
    Inter Research
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    Publication Date: 2024-02-07
    Description: Understanding the underlying ecological factors that affect the distribution patterns of organisms is vital for their conservation. Cephalopods such as giant warty squids Moroteuthopsis longimana are important in the diets of marine predators, including grey-headed albatrosses Thalassarche chrysostoma, yet our understanding of their habitat and trophic ecology remains limited. We investigated the habitat and trophic niche utilised by M. longimana through the delta C-13 and delta N-15 profiles captured in their beaks. M. longimana beaks were collected around grey-headed albatross nests at the Prince Edward Islands during 2004 and 2013 (n = 40 beaks). The results showed distinctly Antarctic distributions (delta C-13 = -24.0 +/- 1.0 parts per thousand, mean +/- SD) for M. longimana, consistent with albatrosses foraging at the Southwest Indian Ridge, as opposed to broader foraging zones utilised by albatrosses from Iles Crozet and Iles Kerguelen. Slightly lower delta N-15 values (5.4 +/- 0.7 parts per thousand) were found compared to other islands in the Indian Sector of the Southern Ocean, which may indicate more crustaceans in the squid diets. Sequential sampling along the lateral walls of individual beaks (n = 4) revealed ontogenetic shifts in delta C-13 and delta N-15 values, but individual variation in these shifts requires further investigation.
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    MSY needs no epitaph—but it was abused (2021)
    Oxford Univ. Press
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    Publication Date: 2024-02-07
    Description: The maximum sustainable yield (MSY) concept is widely considered to be outdated and misleading. In response, fisheries scientists have developed models that often diverge radically from the first operational version of the concept. We show that the original MSY concept was deeply rooted in ecology and that going back to that version would be beneficial for fisheries, not least because the various substitutes have not served us well.
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    Use of food web knowledge in environmental conservation and management of living resources in the Baltic Sea (2021)
    Oxford Univ. Press
    Details
    Publication Date: 2024-02-07
    Description: Food webs are central entities mediating processes and external pressures in marine ecosystems. They are essential to understand and predict ecosystem dynamics and provision of ecosystem services. Paradoxically, utilization of food web knowledge in marine environmental conservation and resource management is limited. To better understand the use of knowledge and barriers to incorporation in management, we assess its application related to the management of eutrophication, chemical contamination, fish stocks, and non-indigenous species. We focus on the Baltic, a severely impacted, but also intensely studied and actively managed semi-enclosed sea. Our assessment shows food web processes playing a central role in all four areas, but application varies strongly, from formalized integration in management decisions, to support in selecting indicators and setting threshold values, to informal knowledge explaining ecosystem dynamics and management performance. Barriers for integration are complexity of involved ecological processes and that management frameworks are not designed to handle such information. We provide a categorization of the multi-faceted uses of food web knowledge and benefits of future incorporation in management, especially moving towards ecosystem-based approaches as guiding principle in present marine policies and directives. We close with perspectives on research needs to support this move considering global and regional change.
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    Partial migration of a maraena whitefish Coregonus maraena population from the River Elbe, Germany (2021)
    Inter Research
    Details
    Publication Date: 2024-02-07
    Description: The maraena whitefish Coregonus maraena is a threatened anadromous species in the North Sea, which in the past was decimated to near extinction. Since the late 1980s, several re-establishment programs have been implemented in rivers draining into the North Sea, but the scientific basis for sustainable conservation measures is often lacking, since little is known about the biology of this species. In this study, otolith microchemistry of fish ranging from 24.6 to 58.4 cm in total length (median 31.3 cm, SD 8.4 cm) was used to characterize the migration behavior of a reintroduced population of maraena whitefish from the River Elbe, Germany. Our analyses revealed the presence of 3 different migration patterns: (1) one-time migration into high-salinity habitat (North Sea) within the first year of life (29.6%), (2) multiple migrations between lowland high-salinity habitats starting in the first year of life (14.8%) and (3) permanent residency within low-salinity habitats, a pattern displayed by the majority (55.6%) of sampled individuals. Not only do these results reveal differential migration behavior, but they also indicate that permanent river residency is common in the River Elbe population of C. maraena. The role of the Elbe as both a feeding and a spawning habitat should thus be considered more explicitly in current conservation measures to support recovery of this species.
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    Activity of loggerhead turtles during the U-shaped dive: insights using angular velocity metrics (2021)
    Inter Research
    Details
    Publication Date: 2024-04-19
    Description: Understanding the behavioural ecology of endangered taxa can inform conservation strategies. The activity budgets of the loggerhead turtle Caretta caretta are still poorly understood because many tracking methods show only horizontal displacement and ignore dives and associated behaviours. However, time-depth recorders have enabled researchers to identify flat, U-shaped dives (or type 1a dives) and these are conventionally labelled as resting dives on the seabed because they involve no vertical displacement of the animal. Video- and acceleration-based studies have demonstrated this is not always true. Focusing on sea turtles nesting on the Cabo Verde archipelago, we describe a new metric derived from magnetometer data, absolute angular velocity, that integrates indices of angular rotation in the horizontal plane to infer activity. Using this metric, we evaluated the variation in putative resting behaviours during the bottom phase of type 1a dives for 5 individuals over 13 to 17 d at sea during a single inter-nesting interval (over 75 turtle d in total). We defined absolute resting within the bottom phase of type 1a dives as periods with no discernible acceleration or angular movement. Whilst absolute resting constituted a significant proportion of each turtle’s time budget for this 1a dive type, turtles allocated 16−38% of their bottom time to activity, with many dives being episodic, comprised of intermittent bouts of rest and rotational activity. This implies that previously considered resting behaviours are complex and need to be accounted for in energy budgets, particularly since energy budgets may impact conservation strategies. © The authors 2021. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are unrestricted. Authors and original publication must be credited
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    Growth and nutritional condition of anchovy larvae on the west and southeast coasts of South Africa (2020)
    Inter Research
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    Publication Date: 2023-02-08
    Description: Cape anchovy Engraulis encrasicolus is an ecologically and economically important pelagic fish species occurring along the coast of South Africa. A recent eastward shift in Cape anchovy distribution indicates that environmental conditions are becoming more favorable for the species on the east coast. This shift is particularly important in the sheltered Algoa Bay region, a nursery area for fish larvae. However, the relatively low productivity of the Agulhas Current Large Marine Ecosystem on the eastern coast of South Africa may result in an anchovy population in poorer nutritional condition and with slower growth rates than the west coast population. Using otolith and nucleic acid analyses, the growth rates of anchovy larvae from the western and southeastern coasts of South Africa were compared. The otolith analysis results indicated that, at any given age, individual growth rates for anchovy larvae were higher on the southeast coast than on the west coast. The RNA:DNA values also indicated that instantaneous growth rates of anchovy larvae were higher in Algoa Bay than on the west coast. At the time of sampling, chlorophyll and zooplankton productivity were higher at sampling sites in Algoa Bay than sites on the west coast, potentially due to favorable oceanographic features in the bay. As such, the results suggest that Algoa Bay is a suitable and potentially favorable nursery area for the early stages of anchovy, highlighting the importance of separate management of the southeast coast region in a changing world.
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    Ocean acidification impacts on biomass and fatty acid composition of a post-bloom marine plankton community (2020)
    Inter Research
    Details
    Publication Date: 2023-02-08
    Description: A mesocosm approach was used to investigate the effects of ocean acidification (OA) on a natural plankton community in coastal waters off Norway by manipulating CO2 partial pressure ( pCO2). Eight enclosures were deployed in the Raunefjord near Bergen. Treatment levels were ambient (~320 µatm) and elevated pCO2 (~2000 µatm), each in 4 replicate enclosures. The experiment lasted for 53 d in May-June 2015. To assess impacts of OA on the plankton community, phytoplankton and protozooplankton biomass and total seston fatty acid content were analyzed. In both treatments, the plankton community was dominated by the dinoflagellate Ceratium longipes. In the elevated pCO2 treatment, however, biomass of this species as well as that of other dinoflagellates was strongly negatively affected. At the end of the experiment, total dinoflagellate biomass was 4-fold higher in the control group than under elevated pCO2 conditions. In a size comparison of C. longipes, cell size in the high pCO2 treatment was significantly larger. The ratio of polyunsaturated fatty acids to saturated fatty acids of seston decreased at high pCO2. In particular, the concentration of docosahexaenoic acid (C 22:6n3c), essential for development and reproduction of metazoans, was less than half at high pCO2 compared to ambient pCO2. Thus, elevated pCO2 led to a deterioration in the quality and quantity of food in a natural plankton community, with potential consequences for the transfer of matter and energy to higher trophic levels
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    Decrease in diatom dominance at lower Si:N ratios alters plankton food webs (2020)
    Oxford Univ. Press
    Details
    Publication Date: 2023-02-08
    Description: Many coastal oceans experience not only increased loads of nutrients but also changes in the stoichiometry of nutrient supply. Excess supply of nitrogen and stable or decreased supply of silicon lower silicon to nitrogen (Si:N) ratios, which may decrease diatom proportion in phytoplankton. To examine how Si:N ratios affect plankton community composition and food web structure, we performed a mesocosm experiment where we manipulated Si:N ratios and copepod abundance in a Baltic Sea plankton community. In high Si:N treatments, diatoms dominated. Some of them were likely spared from grazing unexpectedly resulting in higher diatom biomass under high copepod grazing. With declining Si:N ratios, dinoflagellates became more abundant under low and picoplankton under high copepod grazing. This altered plankton food web structure: under high Si:N ratios, edible diatoms were directly accessible food for copepods, while under low Si:N ratios, microzooplankton and phago-mixotrophs (mixoplankton) were a more important food source for mesograzers. The response of copepods to changes in the phytoplankton community was complex and copepod density-dependent. We suggest that declining Si:N ratios favor microzoo- and mixoplankton leading to increased complexity of planktonic food webs. Consequences on higher trophic levels will, however, likely be moderated by edibility, nutritional value or toxicity of dominant phytoplankton species.
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    Taxon-specific prey response to the invasion of a pelagic invertebrate predator, revealed by comparison of pre- and post-invasion time series (2020)
    Oxford Univ. Press
    Details
    Publication Date: 2023-02-08
    Description: Quantification and attribution of the food web changes associated with the invasion of non-indigenous species in the marine realm often remain a challenge. One of the pelagic non-indigenous species of concern in the recent history of aquatic bioinvasions is the predatory cladoceran Cercopagis pengoi, which invaded the Baltic Sea in the early 1990s. While several studies have reported immediate declines in abundances of its potential prey, the long-term effects of C. pengoi on the food webs remain to be examined. Based on the long-term time series (1968–2018) in the Gulf of Riga (Baltic Sea), we found significant declines in abundance of the cladoceran Pleopis spp. and copepod Eurytemora affinis by 90 and 80%, respectively, are associated with the invasion of C. pengoi as well as significant alterations in seasonal abundance patterns of Pleopis spp., E. affinis and cladoceran Bosmina spp. The invasion of the non-indigenous predator has led to the changed prey abundance–temperature relationships. Special caution was taken in data preprocessing, to minimize the likelihood that observed changes in the zooplankton prey could be associated with factors other than the invasion of C. pengoi, such as temperature and storminess.
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    Zooplankton growth and survival differentially respond to interactive warming and acidification effects (2020)
    Oxford Univ. Press
    Details
    Publication Date: 2023-02-08
    Description: The copepod Acartia tonsa is a key component of a wide range of marine ecosystems, linking energy transfer from phytoplankton to higher trophic levels, and has a central role in productivity and biogeochemistry. The interaction of end-of-century global warming and ocean acidification scenarios with testing moderate temperature effects on a seminatural copepod community is needed to understand future community functioning. Here, we deployed a mesocosm experimental set-up with a full factorial design using two temperatures (13°C and 19°C) crossed with a pCO2 gradient ranging from ambient (550 μatm) to 3000 μatm. We used the natural bacteria, phyto- and microzooplankton species composition and biomass of the Kiel Bight and tested the response of A. tonsa development, carbon growth, mortality, size and condition. The tested traits were differently affected by the interaction of temperature and acidification. Ocean acidification increased development, carbon growth, size and mortality under the warming scenario of 19°C. At 13°C mortality rates decreased, while carbon growth, size and condition increased with acidification. We conclude from our experimental approach that a single species shows a variety of responses depending on the focal functional trait. Trait-specific mesozooplankton responses need to be further investigated and compared between geographical regions, seasons and taxonomic groups.
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    Stoichiometry of Fe, Mn and Co in the marine diazotroph Crocosphaera subtropica ATCC51142 in Fe- and P-limited continuous cultures (2020)
    Inter Research
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    Publication Date: 2023-02-08
    Description: We investigated trace element stoichiometries of the nitrogen-fixing marine cyanobacterium Crocosphaera subtropica ATCC51142 under steady-state growth conditions. We utilized exponentially fed batch cultures and varied iron (Fe) concentrations to establish nutrient limitation in C. subtropica growing at a constant growth rate (0.11 d -1 ). No statistical difference in cell density, chlorophyll a , particulate organic carbon (C), nitrogen (N) and phosphorus (P) were observed between consecutive days after Day 14, and cultures were assumed to be at steady state with respect to growth for the remaining 11 d of the experiment. Cultures were limited by P in the highest Fe treatment (41 nmol l -1 ) and by Fe in the 2 lower-concentration Fe treatments (1 and 5 nmol l -1 ). Cell size and in vivo fluorescence changed throughout the experiment in the 1 nmol l -1 Fe treatment, suggesting ongoing acclimation of C. subtropica to our lowest Fe supply. Nevertheless, Fe:C ratios were not significantly different between the Fe treatments, and we calculated an average (±SD) Fe:C ratio of 32 ± 14 µmol mol -1 for growth at 0.11 d -1 . Steady-state P-limited cells had lower P quotas, whilst Fe-limited cells had higher manganese (Mn) and cobalt (Co) quotas. We attribute the increase in Mn and Co quotas at low Fe to a competitive effect resulting from changes in the supply ratio of trace elements. Such an effect has implications for variability in elemental stoichiometry in marine phytoplankton, and potential consequences for trace metal uptake and cycling in marine systems.
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    Single-Cell Transcriptomics of Abedinium Reveals a New Early-Branching Dinoflagellate Lineage (2020)
    Oxford Univ. Press
    Details
    Publication Date: 2023-02-08
    Description: Dinoflagellates possess many cellular characteristics with unresolved evolutionary histories. These include nuclei with greatly expanded genomes and chromatin packaged using histone-like proteins and dinoflagellate-viral nucleoproteins instead of histones, highly reduced mitochondrial genomes with extensive RNA editing, a mix of photosynthetic and cryptic secondary plastids, and tertiary plastids. Resolving the evolutionary origin of these traits requires understanding their ancestral states and early intermediates. Several early-branching dinoflagellate lineages are good candidates for such reconstruction, however these cells tend to be delicate and environmentally sparse, complicating such analyses. Here, we employ transcriptome sequencing from manually isolated and microscopically documented cells to resolve the placement of two cells of one such genus, Abedinium, collected by remotely operated vehicle in deep waters off the coast of Monterey Bay, CA. One cell corresponds to the only described species, Abedinium dasypus, whereas the second cell is distinct and formally described as Abedinium folium, sp. nov. Abedinium has classically been assigned to the early-branching dinoflagellate subgroup Noctilucales, which is weakly supported by phylogenetic analyses of small subunit ribosomal RNA, the single characterized gene from any member of the order. However, an analysis based on 221 proteins from the transcriptome places Abedinium as a distinct lineage, separate from and basal to Noctilucales and the rest of the core dinoflagellates. The transcriptome also contains evidence of a cryptic plastid functioning in the biosynthesis of isoprenoids, iron–sulfur clusters, and heme, a mitochondrial genome with all three expected protein-coding genes (cob, cox1, and cox3), and the presence of some but not all dinoflagellate-specific chromatin packaging proteins.
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    Estimating stock status from relative abundance and resilience (2020)
    Oxford Univ. Press
    Details
    Publication Date: 2023-02-08
    Description: The Law of the Sea as well as regional and national laws and agreements require exploited populations or stocks to be managed so that they can produce maximum sustainable yields. However, exploitation level and stock status are unknown for most stocks because the data required for full stock assessments are missing. This study presents a new method (AMSY) that estimates relative population size when no catch data are available using time-series of catch-per-unit-effort or other relative abundance indices as the main input. AMSY predictions for relative stock size were not significantly different from the “true” values when compared with simulated data. Also, they were not significantly different from relative stock size estimated by data-rich models in 88% of the comparisons within 140 real stocks. Application of AMSY to 38 data-poor stocks showed the suitability of the method and led to the first assessments for 23 species. Given the lack of catch data as input, AMSY estimates of exploitation come with wide margins of uncertainty which may not be suitable for management. However, AMSY seems to be well suited for estimating productivity as well as relative stock size and may, therefore, aid in the management of data-poor stocks.
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    Climato-stratigraphic subdivision of the Pleistocene in Schleswig-Holstein, Germany and adjoining areas (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: In Schleswig-Holstein wurden in den zurückliegenden vier Jahrzehnten detaillierte Untersuchungen an Probenmaterial aus Aufschlüssen und Kernbohrungen durchgeführt. Analysen der Kiesfraktion und von ‚Leitgeschieben‘ aus glazialen Ablagerungen wurden für die Interpretation und Korrelation genutzt. Glazifluviatile Sedimente wurden TL- und OSL-datiert. Zusammen mit der stratigraphischen Information aus organischen Ablagerungen konnte eine neue klimatostratigraphische Tabelle des Pleistozäns für Schleswig-Holstein mit revidierter Gliederung des Mittel- und Oberpleistozäns erstellt werden. Die Pollensequenz der ältesten pleistozänen Warmzeit (Warmhörn-Thermomer) wird erstmals veröffentlicht. Das Unterpleistozän (Altpleistozän) und das untere Mittelpleistozän sind bei Lieth und bei Gorleben (Niedersachsen) in zwei kontinuierlichen Schichtfolgen vollständig dokumentiert, abgelagert in einem Wechsel von warmen und kalten Klimaphasen. Der oberste Abschnitt der Abfolge von Lieth und der unterste der Abfolge von Gorleben überlappen. Die kombinierte Abfolge bietet ein einzigartiges Referenzprofil für Korrelationen innerhalb Europas. Bisher wurden in Schleswig-Holstein nur drei Kaltzeiten mit Vergletscherungen nachgewiesen, Elster- und Saale-Kaltzeit im oberen Mittelpleistozän und die Weichsel-Kaltzeit im Oberpleistozän. Eine mögliche prä-elsterzeitliche Vergletscherung wird diskutiert. Die Holstein-Warmzeit wird mit MIS 9e korreliert. Das Saale umfasst einen unteren Abschnitt mit nicht-glaziären Kaltzeiten und mit Warmzeiten, der ‚Wacken-Warmzeit‘ (=Dömnitz) und der ‚Leck-Warmzeit‘, korreliert mit MIS 7e und MIS 7c, und einen glaziären oberen Abschnitt. Während des Weichsel gab es wahrscheinlich zwei Phasen mit Vergletscherung, die erste im frühen Mittelweichsel (‚Ellund-Phase‘, spätes MIS 4 oder/und frühes MIS 3), die zweite im oberen Weichsel (MIS 2). Die weichselzeitliche Vergletscherung Schleswig-Holsteins endet um 15 ka BP, als großflächige stagnierende Eisflächen und Toteismassen des Jungbaltischen Gletschervorstoßes (‘Mecklenburg-Phase’) schmolzen.
    Description: research
    Keywords: 551 ; pleistocene ; schleswig-holstein ; pléistocène ; correlations ; climato-stratigraphic table
    Language: English
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    Driving mechanisms of Holocene lagoon development and barrier accretion in Northern Elis, Peloponnese, inferred from the sedimentary record of the Kotychi Lagoon (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-05-06
    Description: As part of the lagoon barrier accretions plain characterizing the NW coast of the Peloponnese, the Kotychi Lagoon is believed to have formed in the prograding delta of the Palaeo-Peneus River over 7000 years ago. Geochemical/sedimentological proxies-data (XRF, grain size, OC-, IC-, C/N-analysis) combined with Bayesian age-depth-modeling revealed that from 8500 to 8000 cal BP marine conditions were prevailing. Around 8000 cal BP, a short-lived sequence of coastline progradation and barrier accretion created lagoonal conditions. Thus, the first chronological control for the onset of lagoon formation in coastal Elis is presented. Pronounced lagoonal conditions developed approximately 6300 cal BP, simultaneously to the period of circum-Mediterranean lagoon formation. A rapidly varying sedimentary record indicates a phase of geomorphological instability between 5200 and 3500 cal BP terminating with the erosional unconformity of a river channel. This evolution reflects a two-phase development: (1) Early Holocene morphology was controlled by the postglacial sea level rise; (2) with receding of the ice sheets by mid-Holocene, the preeminent role of the eustatic signal was overwhelmed giving local and regional processes, such as human-induced soil erosion and climatic forcing an accentuated role. Thus, the evolution of the Elean coastline shows analogies to circum-Mediterranean lagoon formation.
    Description: research
    Keywords: 551.7 ; geochemistry ; lagoon ; sea level change ; Greece ; Holocene coastal evolution ; XRF
    Language: English
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  • 39
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    Climato-stratigraphic subdivision of the Pleistocene in Schleswig-Holstein, Germany and adjoining areas (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: In Schleswig-Holstein detailed petrographical and palynological studies were undertaken with samples from exposures and core drillings examined over the last four decades. Analyses of the gravel fraction and ‘indicator rocks’ of glacial deposits were used for stratigraphical interpretations and correlation. Glaciofluvial sediments were dated by TL and OSL. Combined with the stratigraphical information from organic deposits, a new climato-stratigraphic table of the Pleistocene for Schleswig-Holstein with a revised subdivision of the Middle and Late Pleistocene could be established. The pollen sequence of the oldest Pleistocene warm phase (Warmhörn-Thermomer) is published for the first time. The complete Early Pleistocene and lower Middle Pleistocene stratigraphical sequence is documented at Lieth and at Gorleben (Lower Saxony) in two continuous successions of organic beds developed during warm phases alternating with cold phase deposits. The uppermost part of the Lieth succession and the lowermost part of Gorleben overlap. The combined succession provides a unique reference for correlations through Europe. No more than three cold stages involving glaciation are demonstrated to exist currently in Schleswig-Holstein, the Elsterian and the Saalian in the upper Middle Pleistocene, and the Weichselian in the Late Pleistocene. A possible pre-Elsterian glaciation is discussed. The Holsteinian is correlated with MIS 9e. The Saalian includes a lower part with non-glacial cold phases and warm phases, the ‘Wacken-Warmzeit’ (=Dömnitz) and the ‘Leck-Warmzeit’ correlated with MIS 7e and MIS 7c respectively, and a glacial upper part. During the Weichselian probably two phases of glaciation existed, the first in the early Middle Weichselian (‘Ellund-Phase’; late MIS 4 or/and the early MIS 3), the second in the Upper Weichselian (MIS 2). The Weichselian glaciation of Schleswig-Holstein ends around 15 ka BP when huge stagnant and dead ice masses of the Young Baltic glacier advance (‘Mecklenburg-Phase’) melted.
    Description: research
    Keywords: 551 ; pleistocene ; schleswig-holstein ; pléistocène ; correlations ; climato-stratigraphic table
    Language: English
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    Ice Age geomorphological Ahorn Valley and Ailsbach River terrace evolution – and its importance for the cave use possibilities by cave bears, top predators (hyenas, wolves and lions) and humans (Neanderthals, Late Palaeolithics) in the Frankonian Karst (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: The Sophie’s Cave in Upper Franconia, Bavaria (South Germany) eroded into Upper Jurassic reef dolomite and is a perfect model including all three stages of cave development ranging from a 1. ponor cave, to 2. intermediate periodically flooded cave to 3. dry cave. The key position of the cave along the Ahorn Valley, a side valley of the larger Wiesent River Valley, allow a cave genesis and evolution reconstruction which started in the Pliocene. The main refill took place in the Quaternary with Middle to Late Pleistocene river terrace sediments, present as relict sediments. Seven valley genesis stages between Pliocene to final Late Pleistocene can be separated in elevations of 440 to 375 meters a.s.l. The lowering of the Ailsbach River in the Ahorn Valley is important to understand the accessibility of caves for Pleistocene animals and Palaeolithic humans in different valley positions and elevations during different times in Upper Franconia, and the natural erosive opening/closing of cave entrances towards drainage valleys.
    Description: research
    Keywords: 551 ; bavaria ; cave ; ice age ; Ahorn Valley ; Alsbach River ; terrace evolution ; bears ; humans ; Neanderthals ; Late Palaeolithics
    Language: English
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  • 41
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    Erwägungen zur Korrelation mittelpleistozäner Relikte des Rheingletschers mit der Nordschweizer Stratigraphie (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-05-06
    Description: In the glaciation history of Switzerland (Preusser, Graf, Keller, Krayss & Schlüchter 2011) is shown that two (possibly three) older glacials had happened before the well known glacials Würm = Birrfeld and Riss = Beringen. These are the Habsburg- and the Möhlin-Glacials. In this paper selected key regions in Southern Germany are analysed litho- and morphostratigraphically. This analysis enables us to find the two older glacials proved also at the Rhine Glacier. The period of the „Deckenschotter“-glaciations is followed by a time of striking fluvial erosion (MPR = Middle Pleistocene Reorganisation) in the region of Lake Constance. It is demonstrated that the glaciers of the subsequent Middle Pleistocene glacials exarated the overdeepened Lake Constance basin. The oldest of these „Becken-Glacials“ is named „Größtes Rheinisches Glazial“ (GRG) = Möhlin in the northern part of Switzerland. It corresponds to the Hosskirch introduced by Ellwanger (2003). In the northern Rhine Glacier region the most external glacial deposits belong to this glaciation. Earlier in the northwestern part these deposits are interpreted as Riss-Glacial, but in the northeast as Mindel-Glacial. The GRG evidently must be older than Riss, but younger than the „Younger Deckenschotter“. Therefore Mindel in the northeastern region would be a Becken-Glacial. In the northern part of Switzerland the Habsburg-Glacial nearly reached the extension of the Würm-Glacial. In the region of the Rhine Glacier references and/or indications of the Habsburg-Glacial could be found in a band width corresponding to the Würm, but outside it as well. In the northern region of the Rhine Glacier this vast glaciation has not been discovered up to now because the subsequent glacials Riss and Würm mainly destroyed its relics. To classify the „Greatest Rhine Glacial“ GRG as well as the Habsburg-Glacial chronologically interpolated interglacials with time marks can be applied: IG Unterpfauzenwald – GRG – IG Holstein – Habsburg – IG Meikirch – Riss – IG Eem. Accordingly a temporal classification for the glacials results as follows: (GRG) +350 ka BP (MIS 10), Habsburg +250 ka BP (MIS 8), Riss +150 ka BP (MIS 6).
    Description: research
    Keywords: 551.7 ; glacial deposits ; chronostratigraphy ; alpine foreland ; glacial drainage ; Rhine Glacier
    Language: German
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    Holotype skulls, stratigraphy, bone taphonomy and excavation history in the Zoolithen Cave and new theory about Esper’s “great deluge” (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-05-06
    Description: The Zoolithen Cave, in the Wiesent River Valley of Upper Franconia, Bavaria, South Germany, has a very long excavation history. The site is of international paleobiological importance as the Type site for five Pleistocene top predators (cave bear, Ice Age hyena, lion, wolf, dhole). This large cave system has developed in three elevations and preserves three fluvial sedimentary sequences including two speleothem genesis phases representing changing ponor, dry and wet stages from the Oligocene/Miocene (Neogene), over the Pliocene/Early Pleistocene to Late Pleistocene. The cave bear Ursus deningeri used the cave as den during the MIS 6–9 (Holsteinian interglacial-Saalian glacial). Single P4 tooth and skull shape analyses (“= cave bear clock”) date different cave bear species (U. spelaeus eremus/spelaeus, U. ingressus) within the Late Pleistocene (MIS 3–5d). Finally the bones of other Pleistocene megamammals were washed from two former cave entrances at elevations of about 455 m a.s.l. up to 30 meters deep into lower elevation cave parts, during the Last Glacial Maximum (Post-U. deningeri times or Postglacial), -historically believed to be the result of the “great deluge”. The young “river terrace dolomite gravels” which occur as relic sediments at elevations of about 455 a.s.l in several caves around Muggendorf cannot be explained by natural erosion/river terrace stratigraphy, and must relate to an uncertain glacial context. Finally Iron Age (La Tène) humans left secondary burials (human skulls and long bones with pottery and after-life food animal donations) only in the first deep vertical shaft (Aufzugsschacht) similar to the situation in the nearby Esper’s Cave.
    Description: research
    Keywords: 551.7 ; stratigraphy ; Holotype skulls ; bone taphonomy ; excavation history of the Zoolithen Cave ; new theory about Esper's "great deluge"
    Language: English
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    Ice-Rafted Erratics and Bergmounds from Pleistocene Outburst Floods, Rattlesnake Mountain, Washington, USA (2014)
    Geozon Science Media
    Details
    Publication Date: 2021-05-06
    Description: Exotic ice-rafted debris from the breakup of ice-dammed glacial lakes Missoula and Columbia is common in slackwater areas along the 1,100-km route for outburst floods in the northwestern US. A detailed analysis was performed at Rattlesnake Mountain, which lay beyond the limit of the former ice sheet, where an exceptionally high concentration of ice-rafted debris exists midway along the floods’ path. Here floodwaters temporarily rose to 380 m elevation (forming short-lived Lake Lewis) behind the first substantial hydraulic constriction for the outburst floods near Wallula Gap. Within the 60 km2 study area more than 2,100 erratic isolates and clusters, as well as bergmounds were recorded. Three quarters of erratic boulders are of an exotic granitic composition, which stand in stark contrast to dark Columbia River basalt, the sole bedrock in the region. Other exotics include Proterozoic quartzite and argillite as well as gneiss, diorite, schist and gabbro, all once in direct contact with the Cordilleran Ice Sheet to the north. Most ice-rafted debris is concentrated between 200 and 300 m elevation. Far fewer erratics and bergmounds lie above 300 m elevation because of the preponderance of less-than-maximum floods. Plus, larger deep-rooted icebergs were forced to ground farther away from the ancient shorelines of transient Lake Lewis. As floodwaters moved across the uneven surface of Rattlesnake Mountain, many erratic-bearing icebergs congregated into pre-existing gullies that trend crosswise to flood flow.
    Description: research
    Keywords: 551.7 ; ice-rafted debris ; erratic ; bergmound ; Missoula floods ; Wallula Gap ; Lake Lewis ; glacial Lake Missoula ; Wisconsin Glaciation ; Columbia River basalt
    Language: English
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    Pre-hatching seawater pCO2 affects development and survival of zoea stages of Arctic spider crab Hyas araneus (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 501 . pp. 127-139.
    Details
    Publication Date: 2018-12-31
    Description: Sensitivity of marine crustaceans to anthropogenic CO2 emissions and the associated acidification of the oceans may be less than that of other, especially lower, invertebrates. However, effects on critical transition phases or carry-over effects between life stages have not comprehensively been explored. Here we report the impact of elevated seawater PCO2 values (3100 µatm) on Hyas araneus during the last 2 weeks of their embryonic development (pre-hatching phase) and during development while in the consecutive zoea I and zoea II larval stages (post-hatching phase). We measured oxygen consumption, dry weight, developmental time and mortality in zoea I to assess changes in performance. Feeding rates and survival under starvation were investigated at different temperatures to detect differences in thermal sensitivities of zoea I and zoea II larvae depending on pre-hatch history. When embryos were pre-exposed to elevated PCO2 during maternal care, mortality increased about 60% under continued CO2 exposure during the zoea I phase. The larvae that moulted into zoea II, displayed a developmental delay by about 20 days compared to larvae exposed to control PCO2 during embryonic and zoeal phases. Elevated PCO2 caused a reduction in zoea I dry weight and feeding rates, while survival of the starved larvae was not affected by the seawater CO2 concentration. In conclusion, CO2 effects on egg masses under maternal care carried over to the first larval stages of crustaceans and reduced their survival and development to levels below those previously reported in studies exclusively focussing on acute PCO2 effects on the larval stages.
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    Strong asymmetrical inter-specific relationships in food web simulations (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 512 . pp. 89-98.
    Details
    Publication Date: 2018-06-25
    Description: In complex ecosystem models, relationships between species include a large number of direct interactions and indirect effects. In order to unveil some simple and better understandable relationships, it is useful to study the asymmetry of inter-specific effects. We present a simple approach for this based on stochastic food web simulations from previous studies. We refer to the Prince William Sound (Gulf of Alaska) marine ecosystem model for illustration. Real data were used to parameterize a dynamical food web model. Through simulations and sensitivity analysis, we determined the strength of the effects between all species. We calculated the asymmetry between the mutual effects species have on each other, and selected the top 5% most asymmetrical interactions. The set of these highly asymmetrical relationships is illustrated by a separate graph in which we calculated the positional importance of the species and correlated this to other independent properties such as population size and trophic position. Results suggest that halibut is the key species dominating this system of asymmetrical interactions, but sablefish and adult arrowtooth flounder also seem to be of high importance. Nearshore demersals display the highest number of connections in the graph of asymmetrical links, suggesting that this trophic group regulates the dynamics of many species in the food web. This approach identifies key interactions and most asymmetrical relationships, potentially increasing the efficiency of management efforts and aiding conservation efforts.
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  • 46
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    Nutritional situation for larval Atlantic herring (Clupea harengus L.) in two nursery areas in thewestern Baltic Sea (2014)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 71 (4). pp. 991-1000.
    Details
    Publication Date: 2019-09-24
    Description: The Greifswalder Bodden (GWB) is considered to be the most important spawning and nursery area for the western Baltic spring-spawning herring. However, the biotic and abiotic reasons for this are still unclear. Consequently, we investigated larval growth conditions in the GWB and in the Kiel Canal (KC), another nursery and spawning area of Baltic herring. We investigated prey quantity and quality [copepod abundance and essential fatty acid (EFA) concentration] as well as biochemically derived growth rates and fatty acid content of larval herring in spring 2011. A significant correlation between larval growth and larval EFA concentration could be observed in the GWB. The highest growth rates and EFA concentrations in the larval herring coincided with high food quality. Compensating effects of food quality on food quantity and vice versa could be observed in both the GWB and the KC. While larval growth rates in the KC were high early in the season, highest growth rates in the GWB were achieved late in the season. In conclusion, neither area was superior to the other, indicating similar growth conditions for larval herring within the region.
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  • 47
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    Simultaneous analysis of δ13C, δ15N and δ34S ratios uncovers food web relationships and the trophic importance of epiphytes in an eelgrass, Zostera marina community (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 497 . pp. 93-103.
    Details
    Publication Date: 2019-02-06
    Description: Simultaneous analysis of carbon, nitrogen and sulphur stable isotope ratios was applied in this pilot study to examine the food web of a Zostera marina L. system in the western Baltic Sea. Samples of three potential food sources: eelgrass, epiphytic algae and seston, as well as 69 consumer species were collected during the growing season of Z. marina from March to September 2011. The measured δ13C values of epiphytes (-14.1‰ ± 1.8 SD) were close to δ13C values of eelgrass (-11.6‰ ± 1.8 SD), impeding a clear distinction of those two carbon sources, whereas seston δ13C values (-20.9‰ ± 3.5 SD) were clearly different. This frequently encountered problem was solved by the additional use of δ34S, which resulted in easily distinguishable values for sediment and seawater derived sulphur. Values of primary producer δ34S ranged from 5.6‰ (± 2.3 SD) for Z. marina leaves to 14.2‰ (± 1.6 SD) for epiphytes and 11.9‰ (± 3.3 SD) for seston. The combination of δ34S and δ13C values made a separation of carbon sources possible and enabled the allocation of potential food sources to consumers and a description of their trophic relationships. The data of stable isotope ratio analysis of this eelgrass community strongly indicate a food web based on epiphyte and seston production. δ15N values show a food web consisting of large numbers of generalists and a high degree of omnivory amongst the consumer species analysed. This implies an occupation of every trophic position possible, which is supported by a continuous distribution of δ15N values. Previously described eelgrass food webs may have to be re-evaluated to include sulfur in order to provide a clear picture on primary carbon sources.
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    Changes in organic matter cycling in a plankton community exposed to warming under different light intensities (2014)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 36 (3). pp. 658-671.
    Details
    Publication Date: 2018-06-06
    Description: To investigate the combined effect of temperature and light availability on organic matter production and degradation during a winter/spring phytoplankton bloom in Kiel Bight, we conducted a mesocosm study applying two temperature regimes, ambient (T + 0) and plus 6°C (T + 6) and three irradiance levels. Rising temperature accelerated the onset of the phytoplankton bloom, while light intensity played only a minor role for the timing and bloom development. Maximum build-up of chlorophyll a and particulate organic carbon were ∼20% lower at T + 6 compared with T + 0, probably caused by a combination of elevated heterotrophic processes and enhanced sedimentation during the bloom. The latter is supported by increased TEP concentrations at T + 6 (TEP/POC 0.18 mol C/mol C) compared with T + 0 (0.11 mol C/mol C) during bloom conditions, which may have promoted cell aggregation and sinking. Dissolved organic carbon concentrations increased more rapidly at elevated temperature. For a warmer future ocean, we can hence expect two counteracting mechanisms controlling organic matter flow during phytoplankton blooms: (1) enhanced processing of organic matter via the microbial loop resulting in a faster recycling and (2) depending on the dominating phytoplankton species, enhanced TEP formation resulting in increased particle aggregation and thus export of carbon and nutrients.
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  • 49
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    Temporal variation in stable isotope composition (δ13C, δ15N and δ34S) of a temperate Zostera marina food web (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 505 . pp. 95-105.
    Details
    Publication Date: 2019-04-01
    Description: Simultaneous triple stable isotope analysis of carbon, nitrogen and sulphur was employed to study the temporal variation in the food web of a subtidal eelgrass Zostera marina bed in the western Baltic Sea. Samples of 3 potential food sources (eelgrass, epiphytes and seston) and consumer species were collected biweekly from March through September 2011. Temporal variation of stable isotope compositions was observed in primary producers and consumer species. However, variation between replicates, particularly omnivores, often exceeded variation over time. The high degree of omnivory among the generalist feeders in this eelgrass community allows for generalist feeders to flexibly switch food sources, thus enhancing food-web stability. As coastal systems are subject to seasonal changes, as well as alterations related to human disturbance and climate, these food webs may retain a certain resilience due to their plentiful omnivores.
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    Sink and swim: a status review of thecosome pteropod culture techniques (2014)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 36 (2). pp. 299-315.
    Details
    Publication Date: 2019-09-24
    Description: The widespread distribution of pteropods, their role in ocean food webs and their sensitivity to ocean acidification and warming has renewed scientific interest in this group of zooplankton. Unfortunately, their fragile shell, sensitivity to handling, unknowns surrounding buoyancy regulation and poorly described feeding mechanisms make thecosome pteropods notoriously difficult to maintain in the laboratory. The resultant high mortality rates and unnatural behaviours may confound experimental findings. The high mortality rate also discourages the use of periods of acclimation to experimental conditions and precludes vital long-term studies. Here we summarize the current status of culture methodology to provide a comprehensive basis for future experimental work and culture system development
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    High-frequency seismic radiation from Maule earthquake (Mw 8.8, 2010 February 27) inferred from high-resolution backprojection analysis (2014)
    Oxford Univ. Press
    In:  Geophysical Journal International, 199 (2). pp. 1058-1077.
    Details
    Publication Date: 2018-07-10
    Description: The Maule earthquake (2010 February 27, Mw 8.8, Chile) broke the subduction megathrust along a previously locked segment. Based on an international aftershock deployment, catalogues of precisely located aftershocks have become available. Using 23 well-located aftershocks, we calibrate the classic teleseismic backprojection procedure to map the high-frequency seismic radiation emitted during the earthquake. The calibration corrects traveltimes in a standard earth model both with a static term specific to each station, and a ‘dynamic’ term specific to each combination of grid point and station. The second term has been interpolated over the whole slipping area by kriging, and is about an order of magnitude smaller than the static term. This procedure ensures that the teleseismic images of rupture development are properly located with respect to aftershocks recorded with local networks and does not depend on accurate hypocentre location of the main shock. We track a bilateral rupture propagation lasting ∼160 s, with its dominant branch rupturing northeastwards at about 3 km s−1. The area of maximum energy emission is offset from the maximum coseismic slip but matches the zone where most plate interface aftershocks occur. Along dip, energy is preferentially released from two disconnected interface belts, and a distinct jump from the shallower belt to the deeper one is visible after about 20 s from the onset. However, both belts keep on being active until the end of the rupture. These belts approximately match the position of the interface aftershocks, which are split into two clusters of events at different depths, thus suggesting the existence of a repeated transition from stick-slip to creeping frictional regime.
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    High-pressure Reactive Melt Stagnation Recorded in Abyssal Pyroxenites from the Ultraslow-spreading Lena Trough, Arctic Ocean (2014)
    Oxford Univ. Press
    In:  Journal of Petrology, 55 (2). pp. 427-458.
    Details
    Publication Date: 2018-05-04
    Description: Pyroxenites are an essential component in petrological and geochemical models for melt formation at mid-ocean ridges and ocean islands. Despite their rarity, their origin has been widely discussed and various processes have been invoked for their formation. Here, we present a detailed study of the microtextures and major, minor and trace element compositions of relatively fresh pyroxenites and associated harzburgites from the ultraslow-spreading Lena Trough, Arctic Ocean. Microtextural and geochemical characteristics suggest an origin by magmatic assimilation–fractional crystallization with a high ratio of mass crystallized to mass assimilated. The major element compositions of pyroxenes suggest that this process occurred at high pressures (〉0·7 GPa), although interstitial plagioclase in two of the pyroxenites indicates that melt–rock reaction continued at lower pressures. The parental melt to the pyroxenites was most probably depleted mid-ocean ridge basalt similar to basalts from the North Lena Trough and westernmost Gakkel Ridge; basalts from the Central Lena Trough cannot have functioned as parental melts. The melt was generated close to the garnet–spinel facies transition by variable degrees of partial melting and reacted with the local refractory harzburgite. Pyroxenites from this study provide further evidence, together with plagioclase-bearing and vein-bearing peridotites, for significant melt stagnation below the Lena Trough that occurred over a range of depths, either continuously or stepwise. Comparison with abyssal pyroxenites reveals common characteristics, suggesting that, consistent with results of high-pressure crystallization experiments, they mark the onset of (reactive) crystallization of melts passing through the deeper parts of the mid-ocean ridge plumbing system.
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    Leaving misleading legacies behind in plankton ecosystem modelling (2014)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 36 (3). pp. 613-620.
    Details
    Publication Date: 2019-07-25
    Description: The value of mechanistic ecosystem modelling has long been appreciated, and in connection with trait-based approaches it has recently stimulated a more process-based understanding of adaptive capacities and trade-offs. Notwithstanding recent advances, even sophisticated state-of-the-art models of plankton ecosystems, some of which include hundreds of idealized species, do not accurately represent the great biodiversity of plankton, or the associated flexible adaptive response of plankton communities. We build on previous reviews to suggest that it may be necessary to discard some common assumptions and try new approaches in order to construct models that can make new and testable predictions about the ``adaptive capacity'' of plankton ecosystems. Major challenges remain unresolved for modelling interacting communities of producers and consumers. Rather than the common approach of mixing and matching existing model components, each laden with its own legacy assumptions, we suggest that a judicious combination of innovative, mechanistic approaches that combine traits and trade-offs will likely better address such challenges.
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    C-reactive protein and complement as acute phase reactants in common carp Cyprinus carpio during CyHV-3 infection (2014)
    Inter Research
    In:  Diseases of Aquatic Organisms, 109 (3). pp. 187-199.
    Details
    Publication Date: 2019-01-21
    Description: Cyprinid herpesvirus 3 (CyHV-3) is the aetiological agent of a highly virulent and lethal disease of common carp Cyprinus carpio and its ornamental koi varieties. However, specific knowledge about immune mechanisms behind the infection process is very limited. We aimed to evaluate the effect of the CyHV-3 infection on the profile of 2 major components of the common carp immune acute phase response: the C-reactive protein (CRP) and the complement system. Common carp were infected with CyHV-3 by bath immersion. Fish were sampled before the infection and at 6, 12, 24, 72, 120 and 336 h post-infection for serum and head kidney, liver, gill and spleen tissues. CRP levels and complement activity were determined from the serum, whereas CRP- and complement-related genes (crp1, crp2, c1rs, bf/c2, c3, masp2) expression profiles were analysed in the tissues by quantitative PCR. Both CRP levels and complement activity increased significantly up to 10- and 3-fold, respectively, in the serum of infected fish during the challenge. Analysis revealed distinct organ- and time-dependent expression profile patterns for all selected genes. These results suggest that CRP and complement behave as acute phase reactants to CyHV-3 infection in common carp with an organ- and time-dependent response.
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    Structure and deformation of the Kermadec forearc in response to subduction of the Pacific oceanic plate (2014)
    Oxford Univ. Press
    In:  Geophysical Journal International, 199 (2). pp. 1286-1302.
    Details
    Publication Date: 2018-07-10
    Description: The Tonga-Kermadec forearc is deforming in response to on-going subduction of the Pacific Plate beneath the Indo-Australian Plate. Previous research has focussed on the structural development of the forearc where large bathymetric features such as the Hikurangi Plateau and Louisville Ridge seamount chain are being subducted. Consequently, knowledge of the ‘background’ forearc in regions of normal plate convergence is limited. We report on an ∼250-km-long multichannel seismic reflection profile that was shot perpendicular to the Tonga-Kermadec trench at ∼28°S to determine the lateral and temporal variations in the structure, stratigraphy and deformation of the Kermadec forearc resulting solely from Pacific Plate subduction. Interpretation of the seismic profile, in conjunction with regional swath bathymetry data, shows that the Pacific Plate exhibits horst and graben structures that accommodate bending-induced extensional stresses, generated as the trenchward dip of the crust increases. Trench infill is also much thicker than expected at 1 km which, we propose, results from increased sediment flux into and along the trench. Pervasive normal faulting of the mid-trench slope most likely accommodates the majority of the observed forearc extension in response to basal subduction erosion, and a structural high is located between the mid- and upper-trench slopes. We interpret this high as representing a dense and most likely structurally robust region of crust lying beneath this region. Sediment of the upper-trench slope documents depositional hiatuses and on-going uplift of the arc. Strong along-arc currents appear to erode the Kermadec volcanic arc and distribute this sediment to the surrounding basins, while currents over the forearc redistribute deposits as sediment waves. Minor uplift of the transitional Kermadec forearc, observed just to the north of the profile, appears to relate to an underlying structural trend as well as subduction of the Louisville Ridge seamount chain 250 km to the north. Relative uplift of the Kermadec arc is observed from changes in the tilt of upper-trench slope deposits and extensional faulting of the basement immediately surrounding the Louisville Ridge.
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    Ocean acidification effects on calcifying macroalgae (2014)
    Inter Research
    In:  Aquatic Biology, 22 . pp. 261-279.
    Details
    Publication Date: 2015-01-19
    Description: Since the Industrial Revolution, the partial pressure of carbon dioxide (pCO2) has been increasing and global ocean surface waters have absorbed 30% of the anthropogenic CO2 released into the atmosphere. An increase in pCO2 in surface ocean waters causes an increase in bicarbonate ions (HCO3-) and protons (H+) and a decrease in carbonate ions (CO32-), thereby decreasing the pH and the saturation state of the seawater with respect to CO32-. These changes in ocean chemistry (termed ocean acidification) are expected to have negative impacts on marine calcifying organisms. Because calcifying marine primary producers are important to the carbon cycle and rocky shore habitat structure and stability, investigating how they will respond to future oceanic pCO2 levels is a relevant and important topic of research. Due to a recent strong increase in the number of studies investigating the responses of calcifying marine macroalgae to elevated pCO2, this review aims to present the state of knowledge on the response of calcifying macroalgae to ocean acidification alone and in combination with global and local stressors. We discuss the physiological responses of calcifying macroalgae to elevated pCO2 within the contexts biogeography, taxonomy, and calcification mechanisms. Generally, coralline algae that deposit high-Mg calcite are most susceptible to high pCO2, and polar species are particularly at risk. However, some dolomite-depositing species may be able to acclimate to high pCO2. Calcifiers generally show sensitivity to overgrowth and outcompetition by noncalcifying algae when grown under elevated CO2 conditions, and this trend could be amplified under conditions of high inorganic nutrients. However, it still remains unknown whether or not calcifiers will be able to adapt to their rapidly changing environments. We discuss the lack of research on this topic, and provide some suggestions for how this knowledge gap can be filled by future research.
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    Juvenile sea stars exposed to acidification decrease feeding and growth with no acclimation potential (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 509 . pp. 227-239.
    Details
    Publication Date: 2020-08-28
    Description: Ocean acidification has the potential to affect growth and calcification of benthic marine invertebrates, particularly during their early life history. We exposed field-collected juveniles of Asterias rubens from Kiel Fjord (western Baltic Sea) to 3 seawater CO2 partial pressure (pCO2) levels (ranging from around 650 to 3500 µatm) in a long-term (39 wk) and a short-term (6 wk) experiment. In both experiments, survival and calcification were not affected by elevated pCO2. However, feeding rates decreased strongly with increasing pCO2, while aerobic metabolism and NH4+ excretion were not significantly affected by CO2 exposure. Consequently, high pCO2 reduced the scope for growth in A. rubens. Growth rates decreased substantially with increasing pCO2 and were reduced even at pCO2 levels occurring in the habitat today (e.g. during upwelling events). Sea stars were not able to acclimate to higher pCO2, and growth performance did not recover during the long-term experiment. Therefore, the top-down control exerted by this keystone species may be diminished during periods of high environmental pCO2 that already occur occasionally and will be even higher in the future. However, some individuals were able to grow at high rates even at high pCO2, indicating potential for rapid adaption. The selection of adapted specimens of A. rubens in this seasonally acidified habitat may lead to higher CO2 tolerance in adult sea stars of this population compared to the juvenile stage. Future studies need to address the synergistic effects of multiple stressors such as acidification, warming and reduced salinity, which will simultaneously impact the performance of sea stars in this habitat.
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    Comparison of postseismic afterslip models with aftershock seismicity for three subduction-zone earthquakes: Nias 2005, Maule 2010 and Tohoku 2011 (2014)
    Oxford Univ. Press
    In:  Geophysical Journal International, 199 (2). pp. 784-799.
    Details
    Publication Date: 2018-07-10
    Description: We focus on the relation between seismic and total postseismic afterslip following the Maule Mw 8.8 earthquake on 2010 February 27 in central Chile. First, we calculate the cumulative slip released by aftershock seismicity. We do this by summing up the aftershock regions and slip estimated from scaling relations. Comparing the cumulative seismic slip with afterslip models we show that seismic slip of individual aftershocks exceeds locally the inverted afterslip model from geodetic constraints. As the afterslip model implicitly contains the displacements from the aftershocks, this reflects the tendency of afterslip models to smear out the actual slip pattern. However, it also suggests that locally slip for a number of the larger aftershocks exceeds the aseismic slip in spite of the fact that the total equivalent moment of the afterslip exceeds the cumulative moment of aftershocks by a large factor. This effect, seen weakly for the Maule 2010 and also for the Tohoku 2011 earthquake, can be explained by taking into account the uncertainties of the seismicity and afterslip models. In spite of uncertainties, the hypocentral region of the Nias 2005 earthquake is suggested to release a large fraction of moment almost purely seismically. Therefore, these aftershocks are not driven solely by the afterslip but instead their slip areas have probably been stressed by interseismic loading and the mainshock rupture. In a second step, we divide the megathrust of the Maule 2010 rupture into discrete cells and count the number of aftershocks that occur within 50 km of the centre of each cell as a function of time. We then compare this number to a time-dependent afterslip model by defining the ‘afterslip to aftershock ratio’ (ASAR) for each cell as the slope of the best fitting line when the afterslip at time t is plotted against aftershock count. Although we find a linear relation between afterslip and aftershocks for most cells, there is significant variability in ASAR in both the downdip and along-strike directions of the megathrust. We compare the spatial distribution of ASAR with the spatial distribution of seismic coupling, coseismic slip and Bouguer gravity anomaly, and in each case we find no significant correlation.
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    Impact of CO2 enrichment on organic matter dynamics during nutrient induced coastal phytoplankton blooms (2014)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 36 (3). pp. 641-657.
    Details
    Publication Date: 2019-09-23
    Description: A mesocosm experiment was conducted to investigate the impact of rising fCO2 on the build-up and decline of organic matter during coastal phytoplankton blooms. Five mesocosms (∼38 m³ each) were deployed in the Baltic Sea during spring (2009) and enriched with CO2 to yield a gradient of 355–862 µatm. Mesocosms were nutrient fertilized initially to induce phytoplankton bloom development. Changes in particulate and dissolved organic matter concentrations, including dissolved high-molecular weight (〉1 kDa) combined carbohydrates, dissolved free and combined amino acids as well as transparent exopolymer particles (TEP), were monitored over 21 days together with bacterial abundance, and hydrolytic extracellular enzyme activities. Overall, organic matter followed well-known bloom dynamics in all CO2 treatments alike. At high fCO2, higher ΔPOC:ΔPON during bloom rise, and higher TEP concentrations during bloom peak, suggested preferential accumulation of carbon-rich components. TEP concentration at bloom peak was significantly related to subsequent sedimentation of particulate organic matter. Bacterial abundance increased during the bloom and was highest at high fCO2. We conclude that increasing fCO2 supports production and exudation of carbon-rich components, enhancing particle aggregation and settling, but also providing substrate and attachment sites for bacteria. More labile organic carbon and higher bacterial abundance can increase rates of oxygen consumption and may intensify the already high risk of oxygen depletion in coastal seas in the future.
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    Function of the crystalline style and first detection of laminarinase activity in freshwater mussels of the genus Anodonta (2014)
    Oxford Univ. Press
    In:  Journal of Molluscan Studies, 80 (2). pp. 198-200.
    Details
    Publication Date: 2018-04-03
    Description: Knowledge of the digestive physiology of molluscs is essential for understanding their ecological niches, as well as for their conservation and aquaculture. Freshwater mussels are primarily filter feeders and the complex mechanism of filtration has been studied intensively (Ward et al., 1998; Urrutia et al., 2001; Garrido et al., 2012). However, less is known concerning the physiological mechanisms following ingestion, in particular how food particles are processed in the digestive tract. In bivalves, energy is mostly stored in the form of glycogen, which accounts for 5–14% of the dry weight in Anodonta cygnea (Gäde & Wilps, 1975). For the digestion of various carbohydrates, the crystalline style, a transparent rod composed in part of glycoside hydrolases, is known to be a key component of digestion in the stomach of many snails and marine bivalves. Previous studies (e.g. Alyakrinskaya, 2001) have shown the ability of crystalline style to break down starch in Pseudanodonta complanata and cellulose in Mytilus. Moreover, it has been suggested that crystalline style material not only releases digestive enzymes, but also provides an optimal digestion milieu by buffering ambient pH. Its physiological characteristics, including pH and dissolution, have been described by Hameed (1985) and Warren (1987). This study evaluates the ability of crystalline styles excised from Anodonta anatina to break down different carbohydrate sources and tests the buffering capacity of style material for providing optimal conditions for digestion.
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    No detectable effect of CO2 on elemental stoichiometry of Emiliania huxleyi in nutrient-limited, acclimated continuous cultures (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 507 . pp. 15-30.
    Details
    Publication Date: 2019-09-23
    Description: Effects of CO2 concentration on elemental composition of the coccolithophore Emiliania huxleyi were studied in phosphorus-limited, continuous cultures that were acclimated to experimental conditions for 30 d prior to the first sampling. We determined phytoplankton and bacterial cell numbers, nutrients, particulate components like organic carbon (POC), inorganic carbon (PIC), nitrogen (PN), organic phosphorus (POP), transparent exopolymer particles (TEP), as well as dissolved organic carbon (DOC) and nitrogen (DON), in addition to carbonate system parameters at CO2 levels of 180, 380 and 750 µatm. No significant difference between treatments was observed for any of the measured variables during repeated sampling over a 14 d period. We considered several factors that might lead to these results, i.e. light, nutrients, carbon overconsumption and transient versus steady-state growth. We suggest that the absence of a clear CO2 effect during this study does not necessarily imply the absence of an effect in nature. Instead, the sensitivity of the cell towards environmental stressors such as CO2 may vary depending on whether growth conditions are transient or sufficiently stable to allow for optimal allocation of energy and resources. We tested this idea on previously published data sets where PIC and POC divided by the corresponding cell abundance of E. huxleyi at various pCO2 levels and growth rates were available.
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    Richness-abundance relationships for zooplankton in ballast water: temperate versus Arctic comparisons (2014)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 71 (7). pp. 1876-1884.
    Details
    Publication Date: 2020-07-29
    Description: Species richness and abundance are two commonly measured parameters used to characterize invasion risk associated with transport vectors, especially those capable of transferring large species assemblages. Understanding the relationship between these two variables can further improve our ability to predict future invasions by identifying conditions where high-risk (i.e. species-rich or high abundance or both) and low-risk (i.e. species-poor and low abundance) introduction events are expected. While ballast water is one of the best characterized transport vectors of aquatic non-indigenous species, very few studies have assessed its magnitude at high latitudes. We assessed the arrival potential of zooplankton via ballast water in the Canadian Arctic by examining species richness, total abundance, and the relationship between the two parameters for zooplankton in ships from Europe destined for the Arctic, in comparison with the same parameters for ships bound for Atlantic Canada and the Great Lakes. In addition, we examined whether species richness and/or total abundance were influenced by temperature change and/or ballast water age for each shipping route. We found that species richness and total abundance for Arctic and Great Lakes ships were significantly lower than those for Atlantic ships. Differences in species richness and total abundance for ships utilizing different shipping routes were mostly related to ballast water age. A significant species richness–total abundance relationship for Arctic and Great Lakes ships suggests that these parameters decreased proportionately as ballast water aged. In contrast, the absence of such a relationship for Atlantic ships suggests that decreases in total abundance were accompanied by little to no reduction in species richness. Collectively, our results indicate that the arrival potential of zooplankton in ballast water of Arctic ships may be lower than or similar to that of Atlantic and Great Lakes ships, respectively.
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    Characteristics of juvenile survivors reveal spatio-temporal differences in early life stage survival of Baltic cod (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 511 . pp. 165-180.
    Details
    Publication Date: 2019-09-25
    Description: The spatio-temporal origin of surviving juvenile Baltic cod Gadus morhua was investigated by coupling age information from otolith microstructure analysis and hydrodynamic modeling, which allowed backtracking of drift routes in time and space. The suitability of hydrodynamic modeling for drift simulations of early life stages of Baltic cod up to the pelagic juvenile stage was validated by comparing model simulations with the catch distribution from a survey targeting pelagic juveniles, and mortality rates and hatch date distributions of pelagic and demersal juveniles were estimated. Hatch dates and hatch locations of juvenile survivors showed distinct patterns which did not agree well with the abundance and spatial distribution of eggs, suggesting marked spatio-temporal differences in larval survival. The good agreement of the spatio-temporal origin of survivors from this field investigation with previous modeling studies on the survival chances of early-stage larvae and with general spatio-temporal patterns of larval prey availability suggests that differences in survival are related to food availability during the early larval stage. Results are discussed in relation to the recruitment process of Baltic cod, in particular with respect to the critical period and match-mismatch hypotheses, and to possible implications for the placement of a Marine Protected Area which was established to ensure undisturbed spawning of Baltic cod.
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    Harvesting of drifting filamentous macroalgae in the Baltic Sea: an energy assessment (2014)
    American Institute of Physics (AIP)
    In:  Journal of Renewable and Sustainable Energy, 6 (1). Art.-Nr.: 013116.
    Details
    Publication Date: 2021-06-23
    Description: Eutrophication combined with climate change has caused ephemeral filamentous macroalgae to increase and drifts of seaweed cover large areas of some Baltic Sea sites during summer. In ongoing projects, these mass occurrences of drifting filamentous macroalgae are being harvested to mitigate eutrophication, with preliminary results indicating considerable nutrient reduction potential. In the present study, an energy assessment was made of biogas production from the retrieved biomass for a Baltic Sea pilot case. Use of different indicators revealed a positive energy balance. The energy requirements corresponded to about 30%–40% of the energy content in the end products. The net energy gain was 530–800 MJ primary energy per ton wet weight of algae for small-scale and large-scale scenarios, where 6 000 and 13 000 tonnes dwt were harvested, respectively. However, the exergy efficiency differed from the energy efficiency, emphasising the importance of taking energy quality into consideration when evaluating energy systems. An uncertainty analysis indicated parametric uncertainty of about 25%–40%, which we consider to be acceptable given the generally high sensitivity of the indicators to changes in input data, allocation method, and system design. Overall, our evaluation indicated that biogas production may be a viable handling strategy for retrieved biomass, while harvesting other types of macroalgae than red filamentous species considered here may render a better energy balance due to higher methane yields.
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    Interannual variations in Adriatic Sea zooplankton mirror shifts in circulation regimes in the Ionian Sea (2014)
    Inter Research
    In:  Climate Research, 61 (3). pp. 231-240.
    Details
    Publication Date: 2019-10-21
    Description: We investigated potential connections over the past 2 decades between mesoscale circulation regimes in the Ionian Sea and newly-observed species and the concurrent rise in sea temperature in the Adriatic Sea. Analyses of plankton samples from 1993 to 2011 in the southern Adriatic revealed marked changes in the non-crustacean zooplankton community. Eleven species were recorded for the first time in the Adriatic, while 3 species reappeared after years of absence. We found that pluriannual changes in the zooplankton community tracked the continuum of circulation regimes in the Northern Ionian Gyre (NIG). The occurrence of Atlantic/Western Mediterranean species coincided with anti-cyclonic circulation in the NIG, probably due to the advection of Modified Atlantic Water into the Adriatic, while the presence of Lessepsian species coincided with the cyclonic pattern, which governs the entry of Eastern Mediterranean waters. The impact has been that newcomers now make a significant contribution to the zooplankton community in the southern Adriatic and, in certain cases, have replaced native species. Our results provide new evidence of the influence of teleconnection processes between the North Atlantic and Eastern Mediterranean on the dynamics of water masses in the southern Adriatic. The synergistic effects of these processes, together with warmer Mediterranean waters, raise concerns over dramatic changes in the marine biodiversity of the Adriatic.
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    Last Interglacial paleosols with Argic horizons in Upper Austria and Central Russia (2013)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: The paleosols of the Last Interglacial are presented in many loess sequences of the European temperate zone by soils with Argic horizon, that are considered to be the pedological response to the bioclimatic conditions of that period. We studied micromorphological, physical/chemical (bulk chemical composition, texture and dithionite-extractable iron) and mineralogical characteristics of two profiles – an Eemian Luvisol in Upper Austria (Oberlaab) and a Mikulino Albeluvisol in Central Russia (Alexandrov Quarry near Kursk) to compare them with recent analogous soils and to make further paleoecological and chronological inferences. Both profiles showed a set of characteristics indicative for weathering of primary minerals, clay transformation illuviation and surface redoximorphic (stagnic) processes. Paleosols demonstrate more advanced development than the Holocene analogues manifested however in different pedogenetic characteristics. The Eemian Luvisol in Upper Austria is characterized by stronger clay illuviation manifested in higher clay content and abundance of illuvial clay pedofeatures in the Bt horizon. Mikulino Albeluvisol in Central Russia is more strongly affected by eluvial and stagnic processes evidenced by deeper and more intensive accumulation of bleached silty material and clay depletion. We suppose that the properties of parent material are responsible for these differences. Russian Albeluvisol is formed on the Dnepr loess poor in weatherable minerals and having limited capacity for buffering acidity and clay formation. The higher development status of the Last Interglacial paleosols compared to the Holocene soils having however same type pedogenesis implies longer soil formation period, that agree with some of the paleobotanical proxies and could include besides MIS 5e part of MIS 5d; the warmer and moister paleoclimate during MIS 5e could also account for more advanced paleosol development Several phases of clay illuviation interrupted by frost structuring and deformation are detected in the Eemian Bt horizon in Upper Austria. It suppose even longer development that could extend to the Early Würmian interstadials (late substages of MIS5).
    Description: research
    Keywords: 551 ; paleosol ; paleoclimate ; last interglacial ; Argic horizon
    Language: English
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    Paleopedological record along the loess-paleosol sequence in Oberlaab, Austria (2013)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: A detailed study of a loess-paleosol sequence in Oberlaab, Upper Austria, is presented with emphasis on macro- and micromorphological features, grain size distribution, rock magnetism properties, and weathering degree that allows correlation with other loess-paleosol sequences in neighboring areas, and interpretation of main pedogenic trends. The studied sequence comprises four paleosol complexes, which likely developed during four interglacial stages MIS 11, 9, 7 and 5e, and a modern soil. The oldest paleosol complex (OL5) represents three phases of soil formation, and distinct sedimentary events never reported in the area, with strong reductomorphic properties. The OL4 profile also results from three phases of pedogenesis with increased reductomorphic features in the deepest zone (affected by cryoturbation events). OL3 has abundant features related to gleyic/stagnic processes, but shows signs of clay illuviation. OL2 (Eemian soil) correlates with the MIS 5e. This paleosol shows higher degrees of clay illuviation and weathering, and fewer features related to reductomorphic processes. The modern soil is also polygenetic and constitutes a pedocomplex. Its lowermost part is formed by Würmian glacial deposits, where no well-developed soils are found; only reworked materials and pedosediments. Main pedogenic trends in the sequence are clearly differentiated. All of the paleosols were formed in humid environments, but differing in drainage conditions. The base, with OL5 and OL4 paleosols, was more affected by gleyic processes, while in the upper paleosols, especially OL2, clay illuviation is dominant. We interpret such differences to be caused by the topographic position. The basal paleosols were more affected by fluvioglacial processes due to their position on top of the terrace. The upper paleosols received increased amounts of sediment through fluvial, colluvial and aeolian (loess) input.
    Description: research
    Keywords: 551 ; loess ; paleosol ; pedogenesis ; middle pleistocene ; Oberlaab
    Language: English
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    Paudorf locus typicus (Lower Austria) revisited (2013)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: The more than 12 m thick loess-paleosol sequence in Paudorf, Lower Austria, has been known for decades as locus typicus of the “Paudorfer Bodenbildung” (Paudorf paleosol). The upper section of the outcrop contains an up to 1 m thick pedocomplex that developed during MIS 5. The differentiated sequence of loess-like sediment below, including a more than 2 m thick pedocomplex in its basal part, is an exceptional archive of landscape evolution from the Middle Pleistocene. Herein we present detailed paleopedological and sedimentological surveys, as well as first micromorphological observations to address the sequence in its entirety and the processes leading to its genesis. Furthermore, high resolution color and carbonate analyses, as well as detailed texture analyses, have resulted in a substantial database. The studies show that the loess sediments were subject to a polygenetic development under periglacial conditions reflected in eolian silt and fine sand accumulation, admixture of local material during (mostly solifluidal) redeposition and in situ processes. Horizons with signs of pedogenesis, particularly the two pedocomplexes, document longer phases of stability; the stages of development can be correlated to equivalent sequences and seen as paleoclimatic signals where chronological data are available. The upper pedocomplex is a Chernozem of the early last glacial (MIS 5c–[a?]), which developed in a solifluidal redeposited (MIS 5d) interglacial Cambisol (MIS 5e). Cryosols, typical for MIS 6 sequences, are present in the loess sediment below. The lower pedocomplex formed during several warm stages of varying intensities, with interruptions caused by colluvial processes and admixture of eolian sediment during colder stages.
    Description: research
    Keywords: 551 ; micromorphology ; loess ; lower austria ; paudorf ; middle pleistocene ; paleopedology ; landscape formation
    Language: English
    Type: article , Verlagsversion
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  • 69
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    Magnetic excursions recorded in the Middle to Upper Pleistocene loess/palaeosol sequence Wels-Aschet (Austria). (2013)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Die vorliegende Arbeit stellt die paläomagnetische Bearbeitung der Mittel- bis Oberpleistozänen Löss-/Paläoboden-Sequenz im Areal der ehemaligen Ziegelei Würzburger in Aschet bei Wels vor. Fünf intensiv entwickelte Paläoböden, bzw. Pedokomplexe wechseln mit dazwischen geschalteten Lößlehmlagen ab. Im Rahmen einer Aufbaggerung konnte ein Profil mit einer Mächtigkeit von über 12 m erschlossen werden. Für die magnetostratigraphischen Laboruntersuchungen im Paläomagnetiklabor der Montanuniversität Leoben wurden insgesamt 587 orientierte Proben entnommen, so dass eine beinahe lückenlose Beprobung vorliegt. Die Proben wurden mit magnetischen Wechselfeldern sowie thermisch abmagnetisiert. Zur Bestimmung der magnetischen Trägerminerale in den Sedimenten wurden Curiepunkt-Bestimmungen durchgeführt, die eine Hauptträgerphase mit einem Curie-Punkt bei ca. 580°C (Magnetit), sowie untergeordnete Anteile von Hämatit mit 670°C Curie-Punkt ergaben. Die magnetischen Parameter zeigen eine Folge von Bereichen mit intensiver Magnetitbildung in den Paläoböden, die dem relativ wärmeren Klima von Interglazialen zugeordnet werden können. Die Mehrzahl der Proben zeigen charakteristische Remanenzrichtungen im Bereich des normalen pleistozänen Erdmagnetfeldes. In einigen Profilabschnitten traten stark abweichende Remanenzrichtungen auf, die auf Exkursionen des Erdmagnetfeldes hinweisen. Die beobachteten Exkursionen im Profil Wels-Aschet werden aufgrund paläopedologischer-pedostratigraphischer Ergebnisse in das Zeitintervall von 570 ka (Emperor - Big Lost - Calabrian Ridge) bis 110 ka (Blake) gestellt. Die Brunhes/Matuyama-Grenze (776 ka) wurde nicht erreicht.
    Description: research
    Keywords: 551 ; pleistocene ; loess ; pléistocène ; chronostratigraphy ; palaeosol ; upper austria ; magnetic excursion ; rock magnetic properties
    Language: English
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  • 70
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    A stratigraphic concept for Middle Pleistocene Quaternary sequences in Upper Austria (2013)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Auf den mittelpleistozänen fluvioglazialen Terrassen der Traun-Enns-Platte in der Region um Wels (Oberösterreich) wurden drei Löss-/Paläobodensequenzen untersucht. Jedes dieser Profile ist für mittelpleistozäne Abfolgen im nordöstlichen Alpenvorland charakteristisch. Die Profile umfassen mächtige Pedokomplexe, welche eine Differenzierung und Einstufung von interglazialen Paläoböden erlauben. Die Löss-/Paläobodensequenz von Oberlaab ist auf der fluvioglazialen Terrasse des Mindel-Glazials im klassischen Sinne entwickelt (Jüngere Deckenschotter) und weist vier interglaziale Paläoböden auf. Diese Tatsache macht eine Einstufung der Jüngeren Deckenschotter mindestens in die fünftletzte Kaltzeit wahrscheinlich (MIS 12). Die Deckschichten auf den Günz-Deckenschottern im klassischen Sinn (Ältere Deckenschotter) beinhalten fünf Paläoböden. Beide Lokalitäten weisen eine sehr intensive Pedogenese in ihrem basalen Pedokomplex auf, die wesentlich ausgeprägter ist, als in den überlagernden Paläoböden. Die pedostratigraphischen Ergebnisse lassen eine Einstufung der Älteren Deckenschotter mindestens ins MIS 16 zu.
    Description: research
    Keywords: 551 ; loess ; quaternary stratigraphy ; Wels-Aschet ; Oberlaab ; landscape formation ; palaeosol
    Language: English
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  • 71
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    Grain size and mineralogical indicators of weathering in the Oberlaab loess-paleosol sequence, Upper Austria (2013)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Grain size analyses, bulk and clay mineralogical data were used to characterize weathering within the loess-paleosol-sequence of Oberlaab in Upper Austria. Soil horizons can be clearly identified by the calculation of weathering index Kd from granulometric parameters. The mineralogical composition of the bulk samples shows increasing weathering intensity from the top to the bottom. The weakest weathering stage 1 is not present in Oberlaab, because all samples are free of carbonate minerals. Weathering stage 2 can be found in the upper part of the profile, whereas stage 3 is mainly present in the lowermost horizons. The highest weathering stages 4 and 5 are not present in Oberlaab. The clay mineral distribution in the profile is dominated by the disappearance of primary chlorite in the upper part of the profile and the neoformation of vermiculites from illite by pedogenesis in the lower part. Two different types of mixed layer minerals were found in the pedocomplexes. An illite/chlorite mixed layer mineral occurs following the disappearance of chlorite and is present in the Eemian luvisol. The second mixed layer mineral consists of illite/vermiculite and is present in the whole profile. The weathering stages obtained from the clay mineral composition are slightly lower than that of bulk mineralogy, but reach as well stage 3 in the lower part of the profile.
    Description: research
    Keywords: 551 ; paleosols ; clay minerals ; vermiculite ; secondary chlorite ; weathering index Kd
    Language: English
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  • 72
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    Seasonal dynamics of early life stages of invasive and native ctenophores give clues to invasion and bloom potential in the Baltic Sea (2013)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 35 (3). pp. 582-594.
    Details
    Publication Date: 2018-06-06
    Description: Recently, both the invasive ctenophore Mnemiopsis leidyi and the arctic Mertensia ovum were discovered in the Baltic Sea but their range expansion remains unclear due to misidentification of their larval stages. Supported by molecular species verification we describe seasonal abundance and distribution of larvae and eggs of these two species. We show that their occurrence is significantly but inversely related to salinity. Mertensia ovum was present year round throughout the brackish Baltic Sea but also occurred in high-saline areas during cold seasons. Larvae of M. leidyi occurred throughout all seasons in high-saline areas but never extended further into the central Baltic. Highest ctenophore egg abundances were observed in high-saline areas during summer along with the first appearance of M. leidyi adults. The M. leidyi population peaked 2 months after the first occurrence of adults in high-saline areas, suggesting these areas as a source for lower saline regions. Low larvae abundances and a reduced transitional-to-adult ratio in the southern Baltic point to reduced or no active recruitment, suggesting that drift of animals from high-saline into lower saline regions sustains the M. leidyi population in the southern Baltic such as the Arkona and Bornholm basins.
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  • 73
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    Ability of invasive green crabs to handle prey in a recently colonized region (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 483 . pp. 221-229.
    Details
    Publication Date: 2018-06-25
    Description: During the past few decades, the green crab Carcinus maenas, a native to Europe, has invaded the North American Pacific coast. In this new habitat, C. maenas encounters North American periwinkles of the genus Littorina that differ from European Littorina spp. in size, shape and shell strength. We hypothesize that the ability to handle prey never encountered previously is a prerequisite for successful invasion of novel habitats. In a first approach to testing our hypothesis, we compared European (native) to Canadian (invaded) C. maenas in feeding trials with Littorina spp. from Europe as well as Canada. Canadian crabs had significantly larger crusher claws than European crabs of the same size. Prey handling by Baltic crabs, but not by North Sea crabs, significantly depended on shell morphometry and strength of European periwinkles. By contrast, neither European nor Canadian crabs were affected by shell characteristics of the relatively soft-shelled Canadian periwinkles. Baltic and Canadian crabs did not differ in terms of handling time for, and handling success of, different periwinkle species, but North Sea crabs needed more time for, and were less successful in, crushing periwinkles. We conclude that C. maenas exhibits plasticity in both claw morphometry and feeding behaviour that enables this predator to handle novel prey organisms, and contributes to its success as an invader.
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  • 74
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    Initial dominance in coccolitophore communities affects community structure but does not translate into community functioning (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 473 . pp. 67-77.
    Details
    Publication Date: 2018-06-25
    Description: Climate change has the potential to profoundly influence the community structure and function of marine ecosystems. Prior to testing the consequences of altered environmental conditions on ecosystem functioning, it is first necessary to better understand how the functioning of an ecosystem is affected by its structure. Using phytoplankton communities with 4 naturally co‑occurring coccolithophores including species of Emiliania, Gephyrocapsa, and Calcidiscus collected off the Azores, we experimentally tested whether varying initial dominance leads to different competitive outcomes and consequently affects community functioning, such as biomass and carbon accumulation. We manipulated initial community structure by creating 5 different dominance scenarios: (1) all species contributing evenly to total initial biomass, and (2–5) one of each species contributing 4× that of the remaining 3 species to total initial biomass. All 4 species were simultaneously grown in monocultures starting with the same total initial biomass as the communities. Monocultures differed significantly in total final biomass, particulate inorganic carbon, and particulate organic carbon content. Priority effects in the communities caused the initially dominant species to remain dominant during the stationary phase in 3 out of 4 cases. However, despite varying dominant species and different outcomes in the monocultures, community functioning was unaffected. We suggest that selective and facilitative effects are responsible for the equalization of community functioning. We conclude that monoculture experiments are not sufficient to predict whole-community responses, since species interactions can significantly alter the expected functional outcome.
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  • 75
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    How do cephalopods become available to seabirds: can fish gut contents from tuna fishing vessels be a major food source of deep-dwelling cephalopods? (2013)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 70 (1). pp. 46-49.
    Details
    Publication Date: 2019-09-23
    Description: Cephalopods are important prey for numerous seabird species. However, the physical mechanisms by which cephalopods (particularly species considered as deep-dwelling) become available to seabirds are poorly understood, and it has recently been suggested that the discarded stomachs of gutted fish captured by tuna longliners can be a major source of deep-dwelling species. Here, we identify some deep-dwelling cephalopods that appear in the diet of seabirds, review the current knowledge of their vertical distribution, and compare the stomach contents of commercially captured tuna with those of seabirds foraging in the same area. The limited available information leads us to conclude that tuna longliners are unlikely to be a major source of deep-dwelling cephalopods for seabirds. However, much more information is required on the ecology of seabird prey, particularly commercially unexploited cephalopod species, which may be obtained from scientific cruises devoted to cephalopod biological research. In addition multispecies/foodweb modelling studies may be required to explore potential interactions between seabirds, their predators and prey, and commercial fishing operations.
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  • 76
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    Optimal allocation backs Droop’s cell-quota model (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 473 . pp. 1-5.
    Details
    Publication Date: 2019-09-24
    Description: Droop’s cell-quota model is the most successful description of phytoplankton growth in laboratory cultures and is increasingly being introduced into the ecosystem components of biogeochemical models. Although the Droop model’s parameters can be easily interpreted in biological terms, it was nevertheless derived empirically and lacks a sound mechanistic foundation. Here we derive Droop’s model from a simple optimality condition which maximises net growth rate. Our approach links the maximum cell quota to the cost of nutrient acquisition and suggests that respiration is influenced more strongly by C fixation than by N assimilation.
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  • 77
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    Effects of ocean acidification on the calcification of otoliths of larval Atlantic cod Gadus morhua (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 477 . pp. 251-258.
    Details
    Publication Date: 2018-06-25
    Description: The growth and development of the aragonitic CaCO3 otoliths of teleost fish could be vulnerable to processes resulting from ocean acidification. The potential effects of an increase in atmospheric CO2 on the calcification of the otoliths were investigated by rearing Atlantic cod Gadus morhua L. larvae in 3 pCO2 concentrations—control (370 µatm), medium (1800 µatm) and high (4200 µatm)—from March to May 2010. Increased otolith growth was observed in 7 to 46 d post hatch (dph) cod larvae at elevated pCO2 concentrations. The sagittae and lapilli were usually largest in the high pCO2 treatment followed by the medium and control treatments. The greatest difference in mean otolith surface area (normalized to fish length) was for sagittae at 11 dph, with medium and high treatments being 46 and 43% larger than the control group, respectively. There was no significant pCO2 effect on the shape of the otoliths nor were there any trends in the fluctuating asymmetry, defined as the difference between the right and left sides, in relation to the increase in otolith growth from elevated pCO2.
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  • 78
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    Invasion success of the seaweed Gracilaria vermiculophylla correlates with low palatability (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 486 . pp. 93-103.
    Details
    Publication Date: 2018-06-25
    Description: Differences with respect to anti-herbivore defense were investigated in invasive and native populations of the seaweed Gracilaria vermiculophylla. Specimens from 6 native populations in East Asia and from 8 populations invasive in Europe and the Mexican Pacific coast were maintained under identical conditions and offered to herbivorous snails from both the native range (Littorina brevicula) and Europe (L. littorea) in no-choice feeding assays. L. brevicula consumed in total significantly larger amounts of G. vermiculophylla tissue than did L. littorea. Further, both snail species least consumed the seaweed specimens originating from either non-native populations or from populations native to the Korean East Sea/Sea of Japan. The Korean East Sea/Sea of Japan had previously been identified as putative donor region of all the invasive populations of G. vermiculophylla. Thus, populations in the donor region as well as non-native populations in different invaded realms feature an increased capacity to resist feeding pressure. Differences in nutrient content did not account for the observed patterns of consumption, as palatability and carbon to nitrogen (C:N) ratio were not significantly correlated. Thus, mechanical or chemical defenses or the content of feeding cues influenced the behavior of the snails. We suggest that low palatability contributed to the invasion success of the species.
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  • 79
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    Model prediction vs. reality--testing the predictions of a European eel (Anguilla anguilla) stock dynamics model against the in situ observation of silver eel escapement in compliance with the European eel regulation (2013)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 70 (2). pp. 309-318.
    Details
    Publication Date: 2019-09-23
    Description: A direct monitoring of European silver eel (Anguilla anguilla, L) escapement from rivers and estuaries has been proven to be challenging, and a Europe-wide documentation of escaping silver eel numbers therefore hardly seems realistic. To reinforce management decisions, policy-makers are thus widely reliant on the accuracy of escapement models. A 3-year programme of silver eel escapement monitoring was undertaken to compile model input data and revise an eel population model (German Eel Model II; GEM II) already used in the decision-making process of management authorities. By compiling necessary input data and analysing vital system-specific population characteristics, it was possible to compare the documented silver eel escapement with the modelled potential silver eel escapement. Resulting model predictions were close to actually monitored escapement numbers, which were distinctly lower than reference escapement values for the same freshwater system given in the implementation report of the German Eel Management Plans. Applying different commercial and recreational catch scenarios revealed the sensitivity of the model. The results show the potential of the GEM II and highlight the importance of high-quality input data to use model predictions as the basis for management measures.
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  • 80
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    Population genetics of the invasive ctenophore Mnemiopsis leidyi in Europe reveal source-sink dynamics and secondary dispersal to the Mediterranean Sea (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 485 . pp. 25-36.
    Details
    Publication Date: 2018-06-25
    Description: Repeated invasions of European waters by the ctenophore Mnemiopsis leidyi offer a unique opportunity to study population dynamics and dispersal in gelatinous zooplankton. Here we followed population establishment in two recently invaded areas, the North and Baltic Sea, and analysed changes in population structure during a 3-yr interval using 7 highly polymorphic microsatellites (representing 191 alleles). A second goal was to reconstruct routes of recent invasive range expansion into the Mediterranean Sea During the study period (2008-2010) populations in North Sea and Western Baltic Sea maintained their allelic composition with virtually unchanged levels of genetic diversity and between-population differentiation. This demonstrates that gene flow between the two regions was limited and indicates successful reproduction in both areas. In contrast, at the eastern distribution limit in the central Baltic (Bornholm Basin) the same measures fluctuated between years and genetic diversity decreased from 2008-2010. In concordance with prior ecological observations, this supports the view that here M. leidyi formed a sink population. In the area of recent range expansion (Mediterranean Sea) we observed high population differentiation for a holoplanktonic species. Among Mediterranean samples collected at sites in Spain, France and Israel pairwise differentiation was between Fst = 0.04-0.16. Despite such differentiation, Bayesian clustering and phylogeographic analysis support the hypothesis that all Mediterranean M. leidyi result from a secondary introduction originating in the Black Sea. Our study contributes to growing evidence that multiple invasions of the same species can vary in their degree of genetic diversity and demonstrates how genetic markers can help to resolve whether gelatinous plankton species form self-sustaining populations.
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  • 81
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    Community interactions dampen acidification effects in a coastal plankton system (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 486 . pp. 37-46.
    Details
    Publication Date: 2018-06-25
    Description: Changing seawater chemistry towards reduced pH as a result of increasing atmospheric carbon dioxide (CO2) is affecting oceanic organisms, particularly calcifying species. Responses of non-calcifying consumers are highly variable and mainly mediated through indirect ocean acidification effects induced by changing the biochemical content of their prey, as shown within single species and simple 2-trophic level systems. However, it can be expected that indirect CO2 impacts observed at the single species level are compensated at the ecosystem level by species richness and complex trophic interactions. A dampening of CO2-effects can be further expected for coastal communities adapted to strong natural fluctuations in pCO2, typical for productive coastal habitats. Here we show that a plankton community of the Kiel Fjord was tolerant to CO2 partial pressure (pCO2) levels projected for the end of this century (〈1400 µatm), and only subtle differences were observed at the extremely high value of 4000 µatm. We found similar phyto- and microzooplankton biomass and copepod abundance and egg production across all CO2 treatment levels. Stoichiometric phytoplankton food quality was minimally different at the highest pCO2 treatment, but was far from being potentially limiting for copepods. These results are in contrast to studies that include only a single species, which observe strong indirect CO2 effects for herbivores and suggest limitations of biological responses at the level of organism to community. Although this coastal plankton community was highly tolerant to high fluctuations in pCO2, increase in hypoxia and CO2 uptake by the ocean can aggravate acidification and may lead to pH changes outside the range presently experienced by coastal organisms.
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  • 82
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    Optimality-based model of phytoplankton growth and diazotrophy (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 489 . pp. 1-16.
    Details
    Publication Date: 2019-09-24
    Description: The notion that excess phosphorus (P) and high irradiance favour pelagic diazotrophy is difficult to reconcile with diazotroph behaviour in laboratory experiments and also with the observed distribution of N2-fixing Trichodesmium, e.g. in the relatively nitrogen (N)-rich North Atlantic Ocean. Nevertheless, this view currently provides the state-of-the-art framework to understand both past dynamics and future evolution of the oceanic fixed N inventory. In an attempt to provide a consistent theoretical underpinning for marine autotrophic N2 fixation we derive controls of diazotrophy from an optimality-based model that accounts for phytoplankton growth and N2 fixation. Our approach differs from existing work in that conditions favourable for diazotrophy are not prescribed but emerge, indirectly, from trade-offs among energy and cellular resource requirements for the acquisition of P, N, and carbon. Our model reproduces laboratory data for a range of ordinary phytoplankton species and Trichodesmium. The model predicts that (1) the optimal strategy for facultative diazotrophy is switching between N2 fixation and using dissolved inorganic nitrogen (DIN) at a threshold DIN concentration; (2) oligotrophy, especially in P and under high light, favours diazotrophy; (3) diazotrophy is compatible with DIN:DIP supply ratios well above Redfield proportions; and (4) communities of diazotrophs competing with ordinary phytoplankton decouple emerging ambient and supply DIN:DIP ratios. Our model predictions appear in line with major observed patterns of diazotrophy in the ocean. The predicted importance of oligotrophy in P extends the present view of N2 fixation beyond a simple control by excess P in the surface ocean.
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  • 83
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    Larval development of the barnacle Amphibalanus improvisus responds variably but robustly to near-future ocean acidification (2013)
    Oxford Univ. Press
    In:  ICES Journal of Marine Science, 70 (4). pp. 805-811.
    Details
    Publication Date: 2019-09-23
    Description: Increasing atmospheric CO2 decreases seawater pH in a phenomenon known as ocean acidification. In two separate experiments we found that larval development of the barnacle Amphibalanus (Balanus) improvisus was not significantly affected by the level of reduced pH that has been projected for the next 150 years. After 3 and 6 days of incubation, we found no consistent effects of reduced pH on developmental speed or larval size at pH 7.8 compared with the control pH of 8.1. After 10 days of incubation, there were no net changes in survival or overall development of larvae raised at pH 7.8 or 7.6 compared with the control pH of 8.0. In all cases, however, there was significant variation in responses between replicate batches (parental genotypes) of larvae, with some batches responding positively to reduced pH. Our results suggest that the non-calcifying larval stages of A. improvisus are generally tolerant to near-future levels of ocean acidification. This result is in line with findings for other barnacle species and suggests that barnacles do not show the greater sensitivity to ocean acidification in early life history reported for other invertebrate species. Substantial genetic variability in response to low pH may confer adaptive benefits under future ocean acidification.
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  • 84
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    Constraining the characteristics of tsunami waves from deformable submarine slides (2013)
    Oxford Univ. Press
    In:  Geophysical Journal International, 194 (1). pp. 316-321.
    Details
    Publication Date: 2019-09-24
    Description: As a marine hazard, submarine slope failures have the potential to directly destroy offshore infrastructure, and, if a tsunami is generated, it also endangers the life of those who live and work at the coastline. The hazard and risk from tsunamis generated by submarine mass failure is difficult to quantify and evaluate due to the problems to constrain the characteristics of the triggered submarine landslide, which introduces unquantifiable uncertainty to hazard assessments based on numerical modelling. To lower the uncertainty, we present a method that determines material parameters for the slide body to constrain the generated tsunami waves. Our method employs the distribution of landslide run-out masses and their comparison with simulations. It assumes that the slide material can be approximated by bulk values during the slide motion. To demonstrate our method, we make use of Valdes slide run-out masses off the Chilean coast
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  • 85
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    Distribution and reproduction of the Arctic ctenophore Mertensia ovum in the Baltic Sea (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 491 . pp. 111-124.
    Details
    Publication Date: 2018-06-25
    Description: Species identification based on morphological characteristics has caused misidentifications and led to twisted views of abundances and roles of ctenophores. Based on extensive field studies from 2007 to 2010, the occurrence of the arctic ctenophore Mertensia ovum was genetically verified in the southern, central and northern Baltic Sea, and its egg production, distribution and abundance were studied in relation to physical factors. Genetic analyses indicate that M. ovum is by far the most abundant small ctenophore in the Baltic Sea. Specimens from a 20 yr old ctenophore collection were also genetically identified as M. ovum, contrary to their previous morphological identification as another ctenophore species, Pleurobrachia pileus. Thus, earlier reports on P. pileus in the Baltic Sea may actually refer to M. ovum. The abundance of M. ovum was regulated by both salinity and temperature, with highest abundances found in sea areas and water layers at temperatures 〈7°C, salinities 〉5.5 and oxygen levels 〉4 ml l-1. During summer, the highest abundances of ctenophores and their eggs were found near the halocline, while the distribution was more uniform throughout the water column during winter. Only ctenophores 〉3.5 mm (oral-aboral length) produced eggs in the experiments, with an average rate of 2.2 eggs ind.-1 d-1. Finally, comparison with published data from the 1980s (assuming that those data refer to M. ovum) indicates that the present-day ctenophore abundance is ~80% lower in the north and ~55% higher in the southern parts of the Baltic Sea, due to reasons yet to be established.
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    Effects of ocean acidification and global warming on reef bioerosion—lessons from a clionaid sponge (2013)
    Inter Research
    In:  Aquatic Biology, 19 (2). pp. 111-127.
    Details
    Publication Date: 2016-09-06
    Description: Coral reefs are under threat, exerted by a number of interacting effects inherent to the present climate change, including ocean acidification and global warming. Bioerosion drives reef degradation by recycling carbonate skeletal material and is an important but understudied factor in this context. Twelve different combinations of pCO2 and temperature were applied to elucidate the consequences of ocean acidification and global warming on the physiological response and bioerosion rates of the zooxanthellate sponge Cliona orientalis—one of the most abundant and effective bioeroders on the Great Barrier Reef, Australia. Our results confirm a significant amplification of the sponges’ bioerosion capacity with increasing pCO2, which is expressed by more carbonate being chemically dissolved by etching. The health of the sponges and their photosymbionts was not affected by changes in pCO2, in contrast to temperature, which had significant negative impacts at higher levels. However, we could not conclusively explain the relationship between temperature and bioerosion rates, which were slightly reduced at both colder as well as warmer temperatures than ambient. The present findings on the effects of ocean acidification on chemical bioerosion, however, will have significant implications for predicting future reef carbonate budgets, as sponges often contribute the lion’s share of internal bioerosion on coral reefs.
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    First evidence of reproductive success in a southern invader indicates possible community shifts among Arctic zooplankton (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 493 . pp. 291-296.
    Details
    Publication Date: 2015-07-24
    Description: Pelagic zooplankton were monitored from 2000 to 2012 at a permanent location near the Svalbard archipelago, at the boundary between the central Arctic Ocean and the Greenland Sea in the eastern Fram Strait. The temporal results reveal the first evidence of successful reproduction in Arctic waters by an Atlantic pelagic crustacean from temperate waters. The Atlantic hyperid amphipod Themisto compressa is shown to have expanded its range from more southerly and warmer waters from 2004 onwards. Successful reproductive activity by T. compressa in Arctic waters was confirmed in 2011, indicated by the presence of a complete temporal series of developmental stages including ovigerous females and recently hatched juveniles. The Arctic amphipod community is currently in transition and a continuing northward spread of southern invaders could cause a biodiversity shift from large Arctic to smaller Atlantic species.
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    Separation strategies for invertebrate dormant stages contained in sediment (2013)
    Inter Research
    In:  Aquatic Biology, 18 (3). pp. 209-215.
    Details
    Publication Date: 2015-01-15
    Description: To accurately assess community composition of invertebrates, both active and dormant life stages should be considered. Dormant stages are typically produced as a strategy to overcome inhospitable environmental conditions and can also facilitate species dispersal. While they often sink and accumulate in sediment of natural habitats forming ‘egg banks,’ dormant stages are also found in the sediments accumulated in ships’ ballast tanks. Recent studies have used 2 different methods to separate dormant stages from ballast sediment to assess invasion risk associated with ballast tanks: the colloidal silica sol Ludox HS 40 and sugar flotation (i.e. the Onbé-Marcus method). It has been assumed that the Ludox HS 40 method is most effective for separation but reduces dormant stage viability whereas sugar flotation has lower separation efficacy but higher resulting viability. We conducted a comparative assessment of the 2 methods by separating dormant stages from 160 ballast sediments and examining resulting abundance counts, hatching results, DNA extractions and PCR amplifications. We found no difference in the results between the methods. The financial cost of sugar flotation is lower than that of Ludox HS 40, and costs can be further reduced by using only 1 method instead of both due to lower labour costs, particularly for a large number of samples.
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    Geochemical evidence of oceanic iron fertilization by the Kasatochi volcanic eruption in 2008 and the potential impacts on Pacific sockeye salmon (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 488 . pp. 81-88.
    Details
    Publication Date: 2019-09-23
    Description: The Kasatochi volcanic eruption that occurred in the central Aleutian Islands in Alaska, USA, in August 2008 is thought to have induced a massive diatom bloom in the iron-limited waters of the Gulf of Alaska, which potentially affected the oceanic food web by increasing the abundance of zooplankton and sockeye salmon Oncorhynchus nerka in the northeast Pacific Ocean. We report the first seawater experiments involving volcanic ash ejected from the Kasatochi eruption, showing that the ash released 61 to 83 nmol Fe, 374 to 410 nmol NO3-, 5 to 6 nmol PO43- and 170 to 585 nmol SiO2 when it contacted seawater. Our study suggests that the amount of iron released from Kasatochi ash (an increase of 2.0 to 2.8 nM Fe) was indeed sufficient to cause the observed phytoplankton bloom in the northeastern Pacific Gyre, while the impact of macronutrient release was minimal. We further evaluated the multiple, interdependent processes in the oceanic food web related to the diatom bloom, involving the ocean survival of juvenile salmon that entered the northeast Pacific Ocean in the summer of 2008.
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    Heme b in marine phytoplankton and particulate material from the North Atlantic Ocean (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 483 . pp. 1-17.
    Details
    Publication Date: 2017-10-24
    Description: Concentrations of heme b, the ironcontaining prosthetic group of many hemoproteins, were measured in 6 species of marine phytoplankton (Dunaliella tertiolecta, Emiliania huxleyi, Thalassio - sira weissflogii, T. oceanica, Phaeodactylum tricor - nutum and Synechococcus sp. WH7803) that were subjected to variations in iron concentration. Changes in heme b in response to reduced light and nitrate were also ex amined for E. huxleyi and T. oceanica. Results from laboratory cultures were compared with heme b determined in particulate material in the North Atlantic. In cultures, heme b made up 18 ± 14% (SE) of the total iron pool. Reduced iron and nitrate concentrations resulted in a decreased intracellular heme b concentration, expressed as per mole carbon. Chlorophyll a (chl a) to heme b ratios in E. huxleyi and D. tertiolecta in creased in response to limited light and nutrient availability, but slightly decreased or did not change in the diatoms and the cyanophyte Synechococcus sp. WH7803. The heme b:particulate organic carbon (POC) and chl a:heme b ratios in the North Atlantic were within the range observed in phytoplankton cultures. In the surface mixed layer, decreases in heme b:POC ratios were linked to decreases in nutrient concentrations. Chl a:heme b ratios increased with depth and were thus primarily affected by light availability. Relative relationships between heme b, chl a and POC in the North Atlantic likely represented a change in the ability of cells to undertake cellular processes driven by chl a (light harvesting) and heme b (e.g. electron transport) according to ambient light and nutrient conditions.
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    Marine fungi may benefit from ocean acidification (2013)
    Inter Research
    In:  Aquatic Microbial Ecology, 69 (1). pp. 59-67.
    Details
    Publication Date: 2014-04-22
    Description: Recent studies have discussed the consequences of ocean acidification for bacterial processes and diversity. However, the decomposition of complex substrates in marine environments, a key part of the flow of energy in ecosystems, is largely mediated by marine fungi. Although marine fungi have frequently been reported to prefer low pH levels, this group has been neglected in ocean acidification research. We present the first investigation of direct pH effects on marine fungal abundance and community structure. In microcosm experiments repeated in 2 consecutive years, we incubated natural North Sea water for 4 wk at in situ seawater pH (8.10 and 8.26), pH 7.82 and pH 7.67. Fungal abundance was determined by colony forming unit (cfu) counts, and fungal community structure was investigated by the culture-independent fingerprint method Fungal Automated Ribosomal Intergenic Spacer Analysis (F-ARISA). Furthermore, pH at the study site was determined over a yearly cycle. Fungal cfu were on average 9 times higher at pH 7.82 and 34 times higher at pH 7.67 compared to in situ seawater pH, and we observed fungal community shifts predominantly at pH 7.67. Currently, surface seawater pH at Helgoland Roads remains 〉8.0 throughout the year; thus we cannot exclude that fungal responses may differ in regions regularly experiencing lower pH values. However, our results suggest that under realistic levels of ocean acidification, marine fungi will reach greater importance in marine biogeochemical cycles. The rise of this group of organisms will affect a variety of biotic interactions in the sea.
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    Zur Landschafts- und Gewässergeschichte der Müritz: Umweltgeschichtlich orientierte Bohrungen 2004-2006 zur Rekonstruktion der nacheiszeitlichen Entwicklung (2012)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Mit 113,5 km2 Wasserfläche und einem Einzugsgebiet von 1230 km2 ist die Müritz (62 m HN) der zweitgrösste See des nordmitteleuropäischen Tieflandes (Knapp et al. 1999). Sie war in den vergangenen Jahrzehnten bereits mehrfach das Ziel paläohydrologischer und landschaftsgenetischer Untersuchungen,
    Description: research
    Keywords: 551 ; VAG 000 ; UB 000 ; Geomorphologie {Geologie} ; Hydrosphäre der Festlandgewässer {Hydrologie} ; Müritz ; Geologie ; Hydrologie ; Gewässer ; eiszeit
    Language: German
    Type: monograph , publishedVersion , monograph
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    Halle-Exkursion 2010 des Geowissenschaftlichen Vereins Neubrandenburg e.V. (2012)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Die Herbstexkursion der Sammlergruppe führte 21 Mitglieder und Freunde des Geowissenschaftlichen Vereins Neubrandenburg vom 30. September bis 3. Oktober 2010 in die Geologie von Halle/Saale und Umgebung. Im Stadtgebiet selbst besichtigten wir neben den Baudenkmälern vor allem Zeugnisse der Salzsiedekunst, das Geiseltalmuseum sowie Aufschlüsse rhyolithischer Gesteine des halleschen Vulkanitkomplexes (HVK). Exkursionsziele in der nördlichen Umgebung waren Zeugnisse des historischen und aktuellen Bergbaus auf Steinkohle, Kupferschiefer und Hartgestein.
    Description: research
    Keywords: 551 ; 554.3 ; Exkursion ; Halle
    Language: German
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    Findling Trissow (2012)
    Geozon Science Media
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    Publication Date: 2021-03-29
    Description: Der große Findling von Trissow wird mittels petrographischer Untersuchungen und Vergleichen als granatführender Cordieritgneis aus der Sörmlandmulde bestimmt und beschrieben. Weitere Funde des Gesteins in der Umgebung im Zusammenhang mit typischem Stockholmgranit weisen für die Region ein mögliches gehäuftes Auftreten der Geschiebegemeinschaft aus der Sörmlandregion südlich Stockholms hin.
    Description: research
    Keywords: 551 ; 554.3 ; Findling ; Trissow
    Language: German
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    Der Neubrandenburger Maler Manfred Asmuss und das geologische Naturerbe (2012)
    Geozon Science Media
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    Publication Date: 2021-03-29
    Description: Die besondere Naturraumausstattung Mecklenburgs wird seit Jahrhunderten bis in die Gegenwart von zahlreichen Malern in Bildern dargestellt. Zu ihnen gehört auch Manfred Asmuss, Mitglied des Geowissenschaftlichen Vereins Neubrandenburg e.V.
    Description: research
    Keywords: 551 ; 554.3 ; Geologie ; Manfred Asmuss ; Malerei
    Language: German
    Type: article , Verlagsversion
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    Klassifikation und Aufbau ausgewählter Vorkommen glazilimnischer Sedimente nördlich der Pommerschen Eisrandlage im brandenburgischen Abschnitt der Erdgasfernleitung OPAL (2012)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Die Ostsee-Pipeline-Anbindungsleitung (OPAL) verläuft über 470 km von Lubmin bei Greifswald bis nach Olbernhau an der deutsch-tschechischen Grenze (vgl. Höhlschen 2011). 270 km der Leitung durchziehen von Nord nach Süd das östliche Brandenburg (Abb. 1). Die Pipeline mit einem Durchmesser von 1,40 m wurde im brandenburger Abschnitt zwischen April 2010 und April 2011 verlegt. Im Zuge des Leitungsbaus wurde ein nahezu kontinuierlicher Aufschluss von 2,5 bis 3,5 m Tiefe geschaffen, der einmalige Einblicke in die oberflächennah anstehenden Ablagerungen bot. Ein erster, zusammenfassender Überblick der Ergebnisse wurde für Brandenburg von Juschus et al. 2011 gegeben, für den nördlich angrenzenden Abschnitt Vorpommerns von Börner et al. 2011.
    Description: research
    Keywords: 551 ; 554.3 ; Sedimentologie ; OPAL
    Language: German
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    „Strukturelle Evolution“ der Staatlichen Geologie in Neubrandenburg – „Öffnung“ und „Schließung“ aus Verwaltungs-tektonischer Sicht (2012)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Rede des Leiters des Geologischen Dienstes von Mecklenburg-Vorpommern, Prof. Dr. habil. Ralf-Otto Niedermeyer, im Rahmen des Abschluss-Kolloquiums am 24. November 2009 anlässlich der Schließung der Außenstelle (Geologisches Regionalarchiv) Neubrandenburg des Landesamtes für Umwelt, Naturschutz und Geologie (LUNG) Mecklenburg-Vorpommern (MV) zum Jahresende 2009.
    Description: research
    Keywords: 551 ; 554.3 ; Rede
    Language: German
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    Steine am Stolper Turm (2012)
    Geozon Science Media
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    Publication Date: 2021-03-29
    Description: Der Turm zu Stolpe stellt das bedeutendste mittelalterliche Steinbauwerk des 12 Jh. in der nördlichen Uckermark dar. Es wurden zu seinem Bau neben dem Backstein sowohl vor Ort auffindbare Findlinge (skandinavische Geschiebe) als auch importierte und behauene Blöcke des quarzitisch gebundenen Sandsteins von Höör/Schweden verwendet. Offensichtlich als Ersatzmaßnahmen für den Höör-Sandstein im Außenbereich wurden vermutlich örtlich vorhandene, karbonatisch gebundene, tertiäre Sandsteine verbaut.
    Description: research
    Keywords: 551 ; 554.3 ; Mittelalter ; Stolper Turm ; Stolpe ; Uckermark ; Sandstein
    Language: German
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    Wenn ein großer Eisbrocken schmilzt (2012)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: Die Förderung von Kindern und Jugendlichen nimmt in der Arbeit des Geowissenschaftlichen Vereins Neubrandenburg einen besonderen Platz ein. Vereinsmitglieder besuchen Schulen und ergänzen den Unterricht mit Vorträgen oder Seminaren, bieten Führungen und Ausflüge in die Umgebung oder unterstützen die Lehrer bei der Ausrichtung von Projekttagen, z.B. zum Thema Eiszeit und Glaziale Serie.
    Description: research
    Keywords: 551 ; 554.3 ; eiszeit ; Bildung
    Language: German
    Type: article , publishedVersion
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    Einsatz von GPS-Loggern zur Erfassung und Analyse der Besucherströme in Großschutzgebieten (2012)
    Geozon Science Media
    Details
    Publication Date: 2021-03-29
    Description: In welcher Weise ist die GPS gestützte Protokollierung von Wegerouten der Touristen in Nationalparks sinnvoll und möglich? Wie können erhobene Daten kartographisch ausgewertet und aussagekräftig dargestellt werden? Und wie werden die Touristen am effizientesten für eine Teilnahme akquiriert?
    Description: research
    Keywords: 910 ; QF 000 ; Angewandte Geographie ; GPS Logger ; Schutzgebietsmanagement ; Tourismus ; Nationalpark, Kartographie
    Language: German
    Type: monograph , publishedVersion , monograph
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