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  • Other Sources  (76)
  • Nature Publishing Group  (43)
  • Public Library of Science  (23)
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  • 2015-2019  (76)
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  • 2015  (62)
  • 1
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    In situ observations of coral bleaching in the central Saudi Arabian Red Sea during the 2015/2016 global coral bleaching event (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (4). e0195814.
    Details
    Publication Date: 2021-02-08
    Description: Coral bleaching continues to be one of the most devastating and immediate impacts of climate change on coral reef ecosystems worldwide. In 2015, a major bleaching event was declared as the “3rd global coral bleaching event” by the United States National Oceanic and Atmospheric Administration, impacting a large number of reefs in every major ocean. The Red Sea was no exception, and we present herein in situ observations of the status of coral reefs in the central Saudi Arabian Red Sea from September 2015, following extended periods of high temperatures reaching upwards of 32.5C in our study area. We examined eleven reefs using line-intercept transects at three different depths, including all reefs that were surveyed during a previous bleaching event in 2010. Bleaching was most prevalent on inshore reefs (55.6% ± 14.6% of live coral cover exhibited bleaching) and on shallower transects (41% ± 10.2% of live corals surveyed at 5m depth) within reefs. Similar taxonomic groups (e.g., Agariciidae) were affected in 2015 and in 2010. Most interestingly, Acropora and Porites had similar bleaching rates (~30% each) and similar relative coral cover (~7% each) across all reefs in 2015. Coral genera with the highest levels of bleaching (〉60%) were also among the rarest (〈1% of coral cover) in 2015. While this bodes well for the relative retention of coral cover, it may ultimately lead to decreased species richness, often considered an important component of a healthy coral reef. The resultant long-term changes in these coral reef communities remain to be seen.
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  • 2
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    Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (5). e0197502.
    Details
    Publication Date: 2021-04-23
    Description: Ongoing acidification of the ocean through uptake of anthropogenic CO2 is known to affect marine biota and ecosystems with largely unknown consequences for marine food webs. Changes in food web structure have the potential to alter trophic transfer, partitioning, and biogeochemical cycling of elements in the ocean. Here we investigated the impact of realistic end-of-the-century CO2 concentrations on the development and partitioning of the carbon, nitrogen, phosphorus, and silica pools in a coastal pelagic ecosystem (Gullmar Fjord, Sweden). We covered the entire winter-to-summer plankton succession (100 days) in two sets of five pelagic mesocosms, with one set being CO2 enriched (~760 μatm pCO2) and the other one left at ambient CO2 concentrations. Elemental mass balances were calculated and we highlight important challenges and uncertainties we have faced in the closed mesocosm system. Our key observations under high CO2 were: (1) A significantly amplified transfer of carbon, nitrogen, and phosphorus from primary producers to higher trophic levels, during times of regenerated primary production. (2) A prolonged retention of all three elements in the pelagic food web that significantly reduced nitrogen and phosphorus sedimentation by about 11 and 9%, respectively. (3) A positive trend in carbon fixation (relative to nitrogen) that appeared in the particulate matter pool as well as the downward particle flux. This excess carbon counteracted a potential reduction in carbon sedimentation that could have been expected from patterns of nitrogen and phosphorus fluxes. Our findings highlight the potential for ocean acidification to alter partitioning and cycling of carbon and nutrients in the surface ocean but also show that impacts are temporarily variable and likely depending upon the structure of the plankton food web.
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  • 3
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    Effect of temperature on the accumulation of marine biogenic gels in the surface microlayer near the outlet of nuclear power plants and adjacent areas in the Daya Bay, China (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (6). e0198735.
    Details
    Publication Date: 2021-02-08
    Description: The surface microlayer (SML) in marine systems is often characterized by an enrichment of biogenic, gel-like particles, such as the polysaccharide-containing transparent exopolymer particles (TEP) and the protein-containing Coomassie stainable particles (CSP). This study investigated the distribution of TEP and CSP, in the SML and underlying water, as well as their bio-physical controlling factors in Daya Bay, an area impacted by warm discharge from two Nuclear power plants (Npp’s) and aquaculture during a research cruise in July 2014. The SML had higher proportions of cyanobacteria and of pico-size Chl a contrast to the underlayer water, particularly at the nearest outlet station characterized by higher temperature. Diatoms, dinoflagellates and chlorophyll a were depleted in the SML. Both CSP and TEP abundance and total area were enriched in the SML relative to the underlying water, with enrichment factors (EFs) of 1.5–3.4 for CSP numbers and 1.32–3.2 for TEP numbers. Although TEP and CSP showed highest concentration in the region where high productivity and high nutrient concertation were observed, EFs of gels and of dissolved organic carbon (DOC) and dissolved acidic polysaccharide (〉 1 kDa), exhibited higher values near the outlet of the Npp’s than in the adjacent waters. The positive relation between EF’s of gels and temperature and the enrichment of cyanobacteria in the SML may be indicative of future conditions in a warmer ocean, suggesting potential effects on adjusting phytoplankton community, biogenic element cycling and air-sea exchange processes
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  • 4
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    Increased fitness of a key appendicularian zooplankton species under warmer, acidified seawater conditions (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (1). e0190625.
    Details
    Publication Date: 2021-02-08
    Description: Ocean warming and acidification (OA) may alter the fitness of species in marine pelagic ecosystems through community effects or direct physiological impacts. We used the zooplanktonic appendicularian, Oikopleura dioica, to assess temperature and pH effects at mesocosm and microcosm scales. In mesocosms, both OA and warming positively impacted O. dioica abundance over successive generations. In microcosms, the positive impact of OA, was observed to result from increased fecundity. In contrast, increased pH, observed for example during phytoplankton blooms, reduced fecundity. Oocyte fertility and juvenile development were equivalent under all pH conditions, indicating that the positive effect of lower pH on O. dioica abundance was principally due to increased egg number. This effect was influenced by food quantity and quality, supporting possible improved digestion and assimilation at lowered pH. Higher temperature resulted in more rapid growth, faster maturation and earlier reproduction. Thus, increased temperature and reduced pH had significant positive impacts on O. dioica fitness through increased fecundity and shortened generation time, suggesting that predicted future ocean conditions may favour this zooplankton species. © 2018 Bouquet et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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  • 5
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    Growth performance and survival of larval Atlantic herring, under the combined effects of elevated temperatures and CO2 (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (1). e0191947.
    Details
    Publication Date: 2021-03-19
    Description: In the coming decades, environmental change like warming and acidification will affect life in the ocean. While data on single stressor effects on fish are accumulating rapidly, we still know relatively little about interactive effects of multiple drivers. Of particular concern in this context are the early life stages of fish, for which direct effects of increased CO2 on growth and development have been observed. Whether these effects are further modified by elevated temperature was investigated here for the larvae of Atlantic herring (Clupea harengus), a commercially important fish species. Over a period of 32 days, larval survival, growth in size and weight, and instantaneous growth rate were assessed in a crossed experimental design of two temperatures (10°C and 12°C) with two CO2 levels (400 μatm and 900 μatm CO2) at food levels mimicking natural levels using natural prey. Elevated temperature alone led to increased swimming activity, as well as decreased survival and instantaneous growth rate (Gi). The comparatively high sensitivity to elevated temperature in this study may have been influenced by low food levels offered to the larvae. Larval size, Gi and swimming activity were not affected by CO2, indicating tolerance of this species to projected "end of the century" CO2 levels. A synergistic effect of elevated temperature and CO2 was found for larval weight, where no effect of elevated CO2 concentrations was detected in the 12°C treatment, but a negative CO2 effect was found in the 10°C treatment. Contrasting CO2 effects were found for survival between the two temperatures. Under ambient CO2 conditions survival was increased at 12°C compared to 10°C. In general, CO2 effects were minor and considered negligible compared to the effect of temperature under these mimicked natural food conditions. These findings emphasize the need to include biotic factors such as energy supply via prey availability in future studies on interactive effects of multiple stressors. © 2018 Sswat et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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  • 6
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    Interannual changes in zooplankton echo subtropical and high latitude climate effects in the southern East China Sea (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (5). e0197382.
    Details
    Publication Date: 2021-02-08
    Description: Climate variability plays a central role in the dynamics of marine pelagic ecosystems shaping the structure and abundance changes of plankton communities, thereby affecting energy pathways and biogeochemical fluxes in the ocean. Here we have investigated complex interactions driven a climate-hydrology-plankton system in the southern East China Sea over the period 2000 to 2012. In particular, we aimed at quantifying the influence of climate phenomena playing out in tropical (El Nino 3.4) and middle-high latitudes (East Asia Winter Monsoon, EAWM, and Pacific Decadal Oscillation, PDO) on pelagic copepods. We found that the EAWM and El Nino 3.4 showed a non-stationary and non-linear relationship with local temperature variability. In the two cases, the strength of the relationship, as indexed by the wavelet coherence analysis, decreased along with the positive phase of the PDO. Likewise, the influence of EAWM and El Nino3.4 on copepods exhibited a non-stationary link that changed along with the PDO state. Indeed, copepods and EAWM were closely related during the positive phase, while the link copepods–El Nino 3.4 was stronger during the negative phase. Our results pointed out cascading effects from climate to plankton driven by the positive phase of the PDO through its effect on temperature conditions, and likely through a larger southward transport of nutrient-rich water masses to northern Taiwan and the Taiwan Strait. We suggest a chain of mechanisms whereby the PDO shapes interannual dynamics of pelagic copepods and highlight that these results have implications for integrative management measures, as pelagic copepods plays a prominent role in food web dynamics and for harvested fish in the East China Sea. © 2018 Molinero et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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  • 7
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    Long-term exposure to acidification disrupts reproduction in a marine invertebrate (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (2). e0192036.
    Details
    Publication Date: 2021-02-08
    Description: Climate change research is advancing to more complex and more comprehensive studies that include long-term experiments, multiple life-history stages, multi-population, and multi-trait approaches. We used a population of the barnacle Balanus improvisus known to be sensitive to short-term acidification to determine its potential for long-term acclimation to acidification. We reared laboratory-bred individuals (as singles or pairs), and field-collected assemblages of barnacles, at pH 8.1 and 7.5 ( 400 and 1600 ?atm pCO2 respectively) for up to 16 months. Acidification caused strong mortality and reduced growth rates. Acidification suppressed respiration rates and induced a higher feeding activity of barnacles after 6 months, but this suppression of respiration rate was absent after 15 months. Laboratory-bred barnacles developed mature gonads only when they were held in pairs, but nonetheless failed to produce fertilized embryos. Field-collected barnacles reared in the laboratory for 8 months at the same pH’s developed mature gonads, but only those in pH 8.1 produced viable embryos and larvae. Because survivors of long-term acidification were not capable of reproducing, this demonstrates that B. improvisus can only partially acclimate to long-term acidification. This represents a clear and significant bottleneck in the ontogeny of this barnacle population that may limit its potential to persist in a future ocean.
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  • 8
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    Anaerobic methane oxidation inducing carbonate precipitation at abiogenic methane seeps in the Tuscan archipelago (Italy) (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (12). e0207305.
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    Publication Date: 2021-02-08
    Description: Seepage of methane (CH4) on land and in the sea may significantly affect Earth's biogeochemical cycles. However processes of CH4 generation and consumption, both abiotic and microbial, are not always clear. We provide new geochemical and isotope data to evaluate if a recently discovered CH4 seepage from the shallow seafloor close to the Island of Elba (Tuscany) and two small islands nearby are derived from abiogenic or biogenic sources and whether carbonate encrusted vents are the result of microbial or abiotic processes. Emission of gas bubbles (predominantly CH4) from unlithified sands was observed at seven spots in an area of 100 m(2) at Pomonte (Island of Elba), with a total rate of 234 ml m(-2) d(-1). The measured carbon isotope values of CH4 of around -18 parts per thousand (VPDB) in combination with the measured delta H-2 value of -120 parts per thousand (VSMOW) and the inverse correlation of delta C-13-value with carbon number of hydrocarbon gases are characteristic for sites of CH4 formation through abiogenic processes, specifically abiogenic formation of CH4 via reduction of CO2 by H-2. The H-2 for methanogenesis likely derives from ophiolitic host rock within the Ligurian accretionary prism. The lack of hydrothermal activity allows CH4 gas to become decoupled from the stagnant aqueous phase. Hence no hyperalkaline fluid is currently released at the vent sites. Within the seep area a decrease in porewater sulphate concentrations by ca. 5 mmol/l relative to seawater and a concomitant increase in sulphide and dissolved inorganic carbon (DIC) indicate substantial activity of sulphate-dependent anaerobic oxidation of methane (AOM). In absence of any other dissimilatory pathway, the delta C-13-values between -17 and -5 parts per thousand in dissolved inorganic carbon and aragonite cements suggest that the inorganic carbon is largely derived from CH4. The formation of seep carbonates is thus microbially induced via anaerobic oxidation of abiotic CH4.
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  • 9
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    MAIA—A machine learning assisted image annotation method for environmental monitoring and exploration (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (11). e0207498.
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    Publication Date: 2021-02-08
    Description: Digital imaging has become one of the most important techniques in environmental monitoring and exploration. In the case of the marine environment, mobile platforms such as autonomous underwater vehicles (AUVs) are now equipped with high-resolution cameras to capture huge collections of images from the seabed. However, the timely evaluation of all these images presents a bottleneck problem as tens of thousands or more images can be collected during a single dive. This makes computational support for marine image analysis essential. Computer-aided analysis of environmental images (and marine images in particular) with machine learning algorithms is promising, but challenging and different to other imaging domains because training data and class labels cannot be collected as efficiently and comprehensively as in other areas. In this paper, we present Machine learning Assisted Image Annotation (MAIA), a new image annotation method for environmental monitoring and exploration that overcomes the obstacle of missing training data. The method uses a combination of autoencoder networks and Mask Region-based Convolutional Neural Network (Mask R-CNN), which allows human observers to annotate large image collections much faster than before. We evaluated the method with three marine image datasets featuring different types of background, imaging equipment and object classes. Using MAIA, we were able to annotate objects of interest with an average recall of 84.1% more than twice as fast as compared to “traditional” annotation methods, which are purely based on software-supported direct visual inspection and manual annotation. The speed gain increases proportionally with the size of a dataset. The MAIA approach represents a substantial improvement on the path to greater efficiency in the annotation of large benthic image collections.
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  • 10
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    Contrasting seasonal responses in dinitrogen fixation between shallow and deep-water colonies of the model coral Stylophora pistillata in the northern Red Sea (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (6). e0199022.
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    Publication Date: 2021-02-08
    Description: Tropical corals are often associated with dinitrogen (N-2)-fixing bacteria (diazotrophs), and seasonal changes in key environmental parameters, such as dissolved inorganic nitrogen (DIN) availability and seawater temperature, are known to affect N-2 fixation in coral-microbial holobionts. Despite, then, such potential for seasonal and depth-related changes in N-2 fixation in reef corals, such variation has not yet been investigated. Therefore, this study quantified seasonal (winter vs. summer) N-2 fixation rates associated with the reef-building coral Stylophora pistillata collected from depths of 5, 10 and 20 m in the northern Gulf of Aqaba (Red Sea). Findings revealed that corals from all depths exhibited the highest N-2 fixation rates during the oligotrophic summer season, when up to 11% of their photo-metabolic nitrogen demand (CPND) could be met by N-2 fixation. While N-2 fixation remained seasonally stable for deep corals (20 m), it significantly decreased for the shallow corals (5 and 10 m) during the DIN-enriched winter season, accounting for less than 2% of the corals' CPND. This contrasting seasonal response in N-2 fixation across corals of different depths could be driven by 1) release rates of coral-derived organic matter, 2) the community composition of the associated diazotrophs, and/or 3) nutrient acquisition by the Symbiodinium community.
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  • 11
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    Beached bachelors: An extensive study on the largest recorded sperm whale Physeter macrocephalus mortality event in the North Sea (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (8). e0201221.
    Details
    Publication Date: 2021-02-08
    Description: Between the 8th January and the 25th February 2016, the largest sperm whale Physeter macrocephalus mortality event ever recorded in the North Sea occurred with 30 sperm whales stranding in five countries within six weeks. All sperm whales were immature males. Groups were stratified by size, with the smaller animals stranding in the Netherlands, and the largest in England. The majority (n = 27) of the stranded animals were necropsied and/or sampled, allowing for an international and comprehensive investigation into this mortality event. The animals were in fair to good nutritional condition and, aside from the pathologies caused by stranding, did not exhibit significant evidence of disease or trauma. Infectious agents were found, including various parasite species, several bacterial and fungal pathogens and a novel alphaherpesvirus. In nine of the sperm whales a variety of marine litter was found. However, none of these findings were considered to have been the primary cause of the stranding event. Potential anthropogenic and environmental factors that may have caused the sperm whales to enter the North Sea were assessed. Once sperm whales enter the North Sea and head south, the water becomes progressively shallower (〈40 m), making this region a global hotspot for sperm whale strandings. We conclude that the reasons for sperm whales to enter the southern North Sea are the result of complex interactions of extrinsic environmental factors. As such, these large mortality events seldom have a single ultimate cause and it is only through multidisciplinary, collaborative approaches that potentially multifactorial large-scale stranding events can be effectively investigated.
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  • 12
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    Salinity reduction benefits European eel larvae: Insights at the morphological and molecular level (2018)
    Public Library of Science
    In:  PLoS ONE, 13 (6). e0198294.
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    Publication Date: 2021-02-08
    Description: European eel (Anguilla anguilla) is a euryhaline species, that has adapted to cope with both, hyper- and hypo-osmotic environments. This study investigates the effect of salinity, from a morphological and molecular point of view on European eel larvae reared from 0 to 12 days post hatch (dph). Offspring reared in 36 practical salinity units (psu; control), were compared with larvae reared in six scenarios, where salinity was decreased on 0 or 3 dph and in rates of 1, 2 or 4 psu/day, towards iso-osmotic conditions. Results showed that several genes relating to osmoregulation (nkcc2α, nkcc2β, aqp1dup, aqpe), stress response (hsp70, hsp90), and thyroid metabolism (thrαA, thrαB, thrβB, dio1, dio2, dio3) were differentially expressed throughout larval development, while nkcc1α, nkcc2β, aqp3, aqp1dup, aqpe, hsp90, thrαA and dio3 showed lower expression in response to the salinity reduction. Moreover, larvae were able to keep energy metabolism related gene expression (atp6, cox1) at stable levels, irrespective of the salinity reduction. As such, when reducing salinity, an energy surplus associated to reduced osmoregulation demands and stress (lower nkcc, aqp and hsp expression), likely facilitated the observed increased survival, improved biometry and enhanced growth efficiency. Additionally, the salinity reduction decreased the amount of severe deformities such as spinal curvature and emaciation but also induced an edematous state of the larval heart, resulting in the most balanced mortality/deformity ratio when salinity was decreased on 3 dph and at 2 psu/day. However, the persistency of the pericardial edema and if or how it represents an obstacle in further larval development needs to be further clarified. In conclusion, this study clearly showed that salinity reduction regimes towards iso-osmotic conditions facilitated the European eel pre-leptocephalus development and revealed the existence of highly sensitive and regulated osmoregulation processes at such early life stage of this species.
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  • 13
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    Use of existing hydrographic infrastructure to forecast the environmental spawning conditions for Eastern Baltic cod (2018)
    Public Library of Science
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    Publication Date: 2022-04-26
    Description: The semi-enclosed nature and estuarine characteristics, together with its strongly alternating bathymetry, make the Baltic Sea prone to much stronger interannual variations in the abiotic environment, than other spawning habitats of Atlantic cod (Gadus morhua). Processes determining salinity and oxygen conditions in the basins are influenced both by long term gradual climate change, e.g. global warming, but also by short-term meteorological variations and events. Specifically one main factor influencing cod spawning conditions, the advection of highly saline and well-oxygenated water masses from the North Sea, is observed in irregular frequencies and causes strong interannual variations in stock productivity. This study investigates the possibility to use the available hydrographic process knowledge to predict the annual spawning conditions for Eastern Baltic cod in its most important spawning ground, the Bornholm Basin, only by salinity measurements from a specific location in the western Baltic. Such a prediction could serve as an environmental early warning indicator to inform stock assessment and management. Here we used a hydrodynamic model to hindcast hydrographic property fields for the last 40+ years. High and significant correlations were found for months early in the year between the 33m salinity level in the Arkona Basin and the oxygen-dependent cod spawning environment in the Bornholm Basin. Direct prediction of the Eastern Baltic cod egg survival in the Bornholm Basin based on salinity values in the Arkona Basin at the 33 m depth level is shown to be possible for eggs spawned by mid-age and young females, which currently predominate the stock structure. We recommend to routinely perform short-term predictions of the Eastern Baltic cod spawning environment, in order to generate environmental information highly relevant for stock dynamics. Our statistical approach offers the opportunity to make best use of permanently existing infrastructure in the western Baltic to timely provide scientific knowledge on the spawning conditions of Eastern Baltic cod. Furthermore it could be a tool to assist ecosystem-based fisheries management with a cost-effective implementation by including the short term predictions as a simple indicator in the annual assessments.
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  • 14
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    Multidrug efflux pumps: structure, function and regulation (2018)
    Nature Publishing Group
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    Publication Date: 2022-12-22
    Description: Infections arising from multidrug-resistant pathogenic bacteria are spreading rapidly throughout the world and threaten to become untreatable. The origins of resistance are numerous and complex, but one underlying factor is the capacity of bacteria to rapidly export drugs through the intrinsic activity of efflux pumps. In this Review, we describe recent advances that have increased our understanding of the structures and molecular mechanisms of multidrug efflux pumps in bacteria. Clinical and laboratory data indicate that efflux pumps function not only in the drug extrusion process but also in virulence and the adaptive responses that contribute to antimicrobial resistance during infection. The emerging picture of the structure, function and regulation of efflux pumps suggests opportunities for countering their activities.
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  • 15
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    Environmental development and local human impact in the Jeetzel valley (N Germany) since 10 ka BP as detected by geoarchaeological analyses in a coupled aeolian and lacustrine sediment archive at Soven (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: While archaeological records indicate an intensive Mesolithic occupation of dune areas situated along river valleys, relatively little knowledge exists about environmental interactions in the form of land-use strategies and their possible local impacts. The combination of geoarchaeological, chronological, geochemical and palaeoecological research methods and their application both on a Mesoltihic site situated on top of a dune and the adjacent palaeochannel sediments allows for a detailed reconstruction of the local environmental development around the Soven site in the Jeetzel valley (Northern Germany) since ~10.5 ka cal BP. Based on the results, we identified four phases that may be related to local human impact twice during the Mesolithic, the Neolithic and the Iron Ages and are discussed on the backdrop of the regional settlement history. Although nearby Mesolithic occupation is evident on archaeological grounds, the identification of synchronous impacts on the vegetation in the local environmental records remains tentative even in respect of the broad methodical spectrum applied. Vice versa, human impact is strongly indicated by palaeoecological and geochemical proxies during the Neolithic period, but cannot be connected to archaeological records in the area so far. A younger phase of human impact – probably consisting of seasonal livestock farming in the wetlands – is ascribed to the Iron Age economy and comprises local soil erosion, raised concentrations of phosphates and urease, and the facilitation of grazing related taxa.
    Description: research
    Keywords: 551.7 ; aeolian sand ; pollen ; mesolithic ; iron age ; charcoal ; human impact ; OSL ; Neolithisation
    Language: English
    Type: article , Verlagsversion
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    CITATION GEO-LEO
  • 16
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    Periglaziäre, polygonal-verzweigte rinnenförmige Bildungen und glazitektonische Strukturen in Saale-Till am Elbe-Urstomtalrand bei Wedel (Schleswig-Holstein) (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: Remarkable polygenetical structures were observed at a refinery rehabilitation site in Wedel/Holstein. The polygonal shaped, channel-like structures are incised in mid-Saalian clayey, chalk-rich till. They are symmetrically semicircular shaped and filled with calcareous, silty sands that can be interpreted as sandy reworked till with aeolian components. The width reaches from approx. 0.3 to 1.5 metres, the depth up to approx. 0.8 metres. Horizontal cracks up to more than 10 meters in lengths, occurring as narrow belts of sand with reddish colour, are often centrally aligned in the channel-like structures. The present-day red colour is not natural but related to pollution. These belts reach down to the bottom of the channel like structures. At the lower site of the channel-like structures glacitectonic fissures with a width up to a few centimetres were to be traced into a depth of several metres to the basis of the excavat ion. The genesis of the channel-like structures is discussed. e. g. a possible relation with the pre-existing glacitectonic joints resp. the expected periglacial paleohydrogeological setting.
    Description: research
    Keywords: 551.7 ; periglacial channels ; Weichselian periglacial ; frost wedges ; glacitectonism ; paleohydrogeology ; talik ; Elbe spillway
    Language: German
    Type: article , Verlagsversion
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  • 17
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    Chronostratigraphy of the Hochterrassen in the lower Lech valley (Northern Alpine Foreland) (2015)
    Geozon Science Media
    Details
    Publication Date: 2021-05-06
    Description: Hochterrassen (High or Higher Terraces) are a prominent geomorphological feature of the Northern Alpine Foreland and have traditionally been attributed to the Rissian glaciation. However, distinct morphological sublevels observed for this feature have often raised the question of their age. This issue is exemplarily investigated here on the Langweider and Rainer Hochterrassen in the lower Lech valley using different relative and numerical dating techniques. The lowest sublevel, the Übergangsterrasse is only preserved in small patches at the western rim of the Rainer Hochterrasse and is most probably of early Würmian age. The sublevel of the Jüngere Hochterrasse is older than the Last Interglacial, as indicated by luminescence ages of overlying loess/palaeosol sequence and the development of a luvisol on top of the terrace gravel. This terrace is composed of stacked gravel units that represent at least two accumulation phases correlating with Marine Isotope Stage (MIS) 6 for the top gravel and MIS 7 to MIS 10 (or older) for the basal gravel. It is not yet clear, if the deposition of the basal gravel unit corresponds to one or more aggradation phases during the Middle Pleistocene. The highest sublevel, the Ältere Hochterrasse also shows a compositon of two stacked gravel units but so far, no numerical ages have been achieved for these units.
    Description: research
    Keywords: 551.7 ; northern alpine foreland ; middle pleistocene ; luminescence dating ; Hochterrassen ; fluvial terraces
    Language: English
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    Late Pleistocene spotted hyena den sites and specialized rhinoceros scavengers in the karstified Zechstein areas of the Thuringian Mountains (Central Germany) (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: Crocuta crocuta spelaea (Goldfuss 1823) cranial and postcranial remains of the Pößneck region in the Zechstein Karst region of the Thuringian Mountains (Central Germany) were excavated historically in the Wüste Scheuer Cavity at Döbritz. Nearby, at the Krölpa gypsum karst open air site, additionally a woolly rhinoceros, partially scavenged by Ice Age spotted hyenas, was found. The amount at Wüste Scheuer Cavity includes chew damaged Coelodonta antiquitatis remains and is classified herein as communal den type. At both den/scavenging sites, only a small amount of prey material of Late Pleistocene megafauna of rare M. primigenius, mainly C. antiquitatis, E. c. przewalskii, and fewer B. priscus and R. tarandus was accumulated. The dominance of woolly rhinoceros, bison and Przewalski horse bones are typical for hyena bone assemblages in European low mountain regions, where mammoth was nearly absent as a result of topography. In the Thuringian Karst Mountains nine Late Pleistocene Ice Age spotted hyena den sites are identified. Solely hyena dens are present in Zechstein open air gypsum and limestone karstic regions of Bad Köstritz, Krölpa and Fuchsluken Cavities near Saalfeld. In the Wüste Scheuer their remains overlap with Middle Palaeolithic Neanderthal human camp sites, similar as in the Ilsen Cave at Ranis and Lindenthal Cave in Gera, which demonstrates competition for prey and shelter cavities. At such cave sites, bone remains were historically misinterpreted as „solely of Neanderthal human kitchen rubbish” or even as “bone tools” (e.g. “bone scrapers” = woolly rhinoceros tibia bones chewed by hyenas).
    Description: research
    Keywords: 551.7 ; late pleistocene ; Ice Age spotted hyenas ; den types ; Thuringian Mountains ; Central Germany
    Language: English
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    Ein Uferprofil am Priesterbäker See: Slawenzeitlich-mittelalterliche Seespiegelschwankungen im Bereich der „Specker Seen“ (Mecklenburg) (2015)
    Geozon Science Media
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    Publication Date: 2021-03-29
    Description: Eine durch einen Bodenschurf aufgeschlossene Boden-Sediment-Folge einer alten Seeterrasse im Einzugsgebiet des Priesterbäker Sees zeigt deutliche Fazieswechsel im Uferbereich des Gewässers. Die Abfolge von liegenden humosen Sanden, welche einen ehemaligen Verlandungssaum nachzeichnen, limnischen Sanden mit Bodenbildung und hangenden Flugsanden belegt Änderungen in der Sedimentation, welche mit säkularen Grundwasser- bzw. Seespiegelschwankungen zu erklären sind. Mit Hilfe von geophysikalischen Datierungen lassen sich gegenüber dem heutigen Niveau höhere Wasserstände für den Priesterbäker See bzw. die so genannten „Specker Seen“ östlich der Müritz während des 7.–9. und 12.–14. Jahrhunderts ableiten.
    Description: research
    Keywords: 551 ; 554.3 ; seespiegelschwankungen ; mecklenburg ; Seeterrasse ; Priesterbäker See ; Slawenzeit
    Language: German
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    Weichselzeitliche Kryocalcite als Hinweise für Eisseen in der Hüttenbläserschachthöhle (Iserlohn/NRW) (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: C/O-stable isotope composition (VPDB) of speleothems from the Makkaronihalle of the Hüttenbläserschacht Cave in Iserlohn shows a clear separation between glacial and interglacial calcites. In contrast to normal speleothems (stalagmites, excentriques, crystals in cave ponds, draperies; δ18O: –4.0 to –6.1 ‰, δ13C: –4.9 to –10.9 ‰), rhombohedral crystal sinter and spherulitic speleoparticles are characterised by lower δ18O (–8.9 to –17.9 ‰) and higher δ13C values (+0.7 to –6.1 ‰). This suggests that these speleogenetic particles were formed in slowly freezing waterpools on ice during the transition from a stadial to an interstadial phase. Precise 230Th/U-dating shows younger Weichselian ages of 28.6 to 33.0 ka for these speleogenetic particles from north-west Germany. These formation periods indicate freezing conditions overlain by 34 m of hostrock and provide the minimum depth of permafrost penetration for the younger Weichselian in the area of the northern Sauerland (north-west Germany).
    Description: research
    Keywords: 551.7 ; permafrost ; Cryogenic calcites ; C/O isotopes ; Upper Weichselian ; ice caves ; north-western Germany
    Language: German
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  • 21
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    Spätsaalezeitliche und eemzeitliche Makrofaunen aus dem Kliffaufschluss Klein Klütz Höved (NW-Mecklenburg) (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: On the basis of the work done by Strahl et al. (1994), the mollusc specimens in the Late Saalian glacial and Eemian interglacial sediments from the cliff outcrop of Klein Klütz Höved (NW Mecklenburg) were re-examined and, in the process, a few vertebrates (fishes, micromammals) were also found. The mollusc specimens from the Late Saalian sand and mud alone comprise approximately 40 species among which terrestrial varieties, e.g. Succinella oblonga, Pupilla loessica, P. pratensis, Vallonia tenuilabris or Vertigo genesii, are clearly predominant as far as the number of individual specimens is concerned. Among the limnic varieties were also found the glacial index species Pisidium obtusale f. lapponicum and P. stewarti. It was also possible to prove the northern-most presence for Germany of the steppe lemming Lagurus lagurus in the Late Saalian. In the Eemian mud, the molluscs found were almost exclusively limnic. This about 20 species comprising fauna is characte-ristic of a river system with calmer areas, oxbow lakes and in-coming springs. These fluvial conditions were confirmed by the freshwater bivalves Pisidium amnicum, P. supinum, P. moitessierianum, P. ponderosum and Unio tumidus. For the first time in Mecklenburg-Western Pomerania, evidence was found of the spring snail Belgrandia germanica as an interglacial index species. The limnic-fluvial section of the Eemian is topped by a cryoturbate structures. Its sandy, gravelly pockets contain marine molluscs. The index species for the marine Eemian found in the southern Baltic region are Polititapes senescens and Bittium reticulatum.
    Description: research
    Keywords: 551.7 ; molluscs ; Saalian deposits ; limnic and marine Eemian facies ; Belgrandia germanica ; micromammals ; Lagurus lagurus ; Mecklenburg-Western Pomerania
    Language: German
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    Klima, Grundwassernutzung oder Waldbewirtschaftung? Ursachen tendenziell fallender Grundwasserstände am Beispiel Südwest-Usedoms (2015)
    Geozon Science Media
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    Publication Date: 2021-03-29
    Description: Tendenziell fallende Grundwasserstände können vielfältige Ursachen haben, z.B. die Änderung der klimatischen Bedingungen, Modifikationen der Landnutzung oder die Entnahme von Grundwasser. Am Beispiel Südwest-Usedoms wird dargestellt, wie mögliche Einflussfaktoren analysiert und quantifiziert werden können. Für das Untersuchungsgebiet zeigte sich, dass die über Jahrzehnte gesunkenen Grundwasserstände überwiegend aus der Kahlschlagbewirtschaftung des Waldes resultieren und damit weniger einen Trend als eine überjährliche Schwankung ausweisen.
    Description: research
    Keywords: 551 ; 554.3 ; forest ; Sickerwasser ; Grundwasser ; Grundwasserneubildung ; Wald ; Landschaftswasserhaushalt ; Trend ; Grundwasserentnahme ; geohydraulisches Modell ; Landscape water regime ; Groundwater ; Groundwater recharge ; percolate water ; Groundwater extraction ; Groundwater modelling ; Geohydraulic model ; Grundwasserströmung ; Modellierung
    Language: German
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    Bw horizon in Holocene slope deposits (Kratzeburg, NE Germany) – dating and pedological characteristics (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: A soil-sediment sequence in NE Germany has provided information about the duration and intensity of formation of a Bw horizon in Holocene slope deposits. With a combination of optically stimulated luminescence (OSL), 14C- and archaeological dating methods, colluvial layers taken from a former castle wall trench constructed during the Bronze Age were dated. With this chronology, the relative age of the postsedimentary Bw horizon formation within the colluvial sediments was derived, resulting in the first valid pedochronological data (maximum and minimum age) for a Holocene Bw horizon in NE Germany. The horizon was formed within 2400 years. Weathering and brunification have altered the Holocene parent material. However, the geochemical characteristics of the Holocene soil formation are weak compared to Bw horizons from the Late Glacial and the Late Glacial to Holocene. The results presented here enhance our understanding of soil formation processes in northern Germany, while highlighting the role of colluvial layers as sedimentological tracers of Holocene soil formation processes.
    Description: research
    Keywords: 551.7 ; holocene ; ne germany ; dating ; Bw horizon ; Slope deposits ; soil formation
    Language: English
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    Holocene Vegetation and Land Use History in the Northern Vosges (France) (2015)
    Geozon Science Media
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    Publication Date: 2021-05-06
    Description: A radiocarbon-dated peat profile from Rond Pertuis supérieure mire in the uplands of the Northern Vosges is studied using palynological methods. The profile dates from the middle Atlantic period (4500–3100 B.C.) to recent times. During the middle of the Atlantic period an oak forest rich in pine covered the Northern Vosges. Fir and beech immigrated at the end of the Atlantic leading to the decline of oak and pine in the forest. This also marked the onset of decisive human influence on the development of the terrestrial vegetation. Five land use phases were detected, the first one at the end of the Neolithic period (~4000–2200 B.C.). Subsequently, continuous land use is evident from the Bronze Age (2200–800 B.C.) up to now. In the late Middle Ages (A.D. 900–1500) and the early Modern Era (since A.D. 1500), the woodlands were completely altered by human activities. During the 19th century modern forestry introduced spruce into the investigated area in the Northern Vosges. Spruce afforestation then accelerated in the middle of the 20th century.
    Description: research
    Keywords: 551.7 ; holocene ; pollen analysis ; france ; human impact ; Northern Vosges
    Language: English
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    A daily global mesoscale ocean eddy dataset from satellite altimetry (2015)
    Nature Publishing Group
    In:  Scientific Data, 2 (Art. Nr. 150028).
    Details
    Publication Date: 2017-10-24
    Description: Mesoscale ocean eddies are ubiquitous coherent rotating structures of water with radial scales on the order of 100 kilometers. Eddies play a key role in the transport and mixing of momentum and tracers across the World Ocean. We present a global daily mesoscale ocean eddy dataset that contains ~45 million mesoscale features and 3.3 million eddy trajectories that persist at least two days as identified in the AVISO dataset over a period of 1993–2014. This dataset, along with the open-source eddy identification software, extract eddies with any parameters (minimum size, lifetime, etc.), to study global eddy properties and dynamics, and to empirically estimate the impact eddies have on mass or heat transport. Furthermore, our open-source software may be used to identify mesoscale features in model simulations and compare them to observed features. Finally, this dataset can be used to study the interaction between mesoscale ocean eddies and other components of the Earth System.
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    Discovery of microbial natural products by activation of silent biosynthetic gene clusters (2015)
    Nature Publishing Group
    In:  Nature Reviews Microbiology, 13 (8). pp. 509-523.
    Details
    Publication Date: 2020-06-23
    Description: Microorganisms produce a wealth of structurally diverse specialized metabolites with a remarkable range of biological activities and a wide variety of applications in medicine and agriculture, such as the treatment of infectious diseases and cancer, and the prevention of crop damage. Genomics has revealed that many microorganisms have far greater potential to produce specialized metabolites than was thought from classic bioactivity screens; however, realizing this potential has been hampered by the fact that many specialized metabolite biosynthetic gene clusters (BGCs) are not expressed in laboratory cultures. In this Review, we discuss the strategies that have been developed in bacteria and fungi to identify and induce the expression of such silent BGCs, and we briefly summarize methods for the isolation and structural characterization of their metabolic products.
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    Littoral lichens as a novel source of potentially bioactive Actinobacteria (2015)
    Nature Publishing Group
    In:  Scientific Reports, 5 (1).
    Details
    Publication Date: 2017-12-21
    Description: Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens ( Lichina confinis and L. pygmaea ; from intertidal and subtidal zones) and one littoral lichen ( Roccella fuciformis ; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria.
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    Water column methanotrophy controlled by a rapid oceanographic switch (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (5). pp. 378-382.
    Details
    Publication Date: 2020-11-23
    Description: Large amounts of the greenhouse gas methane are released from the seabed to the water column1, where it may be consumed by aerobic methanotrophic bacteria2. The size and activity of methanotrophic communities, which determine the amount of methane consumed in the water column, are thought to be mainly controlled by nutrient and redox dynamics3–7. Here, we report repeated measurements of methanotrophic activity and community size at methane seeps west of Svalbard, and relate them to physical water mass properties and modelled ocean currents. We show that cold bottom water, which contained a large number of aerobic methanotrophs, was displaced by warmer water with a considerably smaller methanotrophic community within days. Ocean current simulations using a global ocean/sea-ice model suggest that this water mass exchange is consistent with short-term variations in the meandering West Spitsbergen Current. We conclude that the shift from an offshore to a nearshore position of the current can rapidly and severely reduce methanotrophic activity in the water column. Strong fluctuating currents are common at many methane seep systems globally, and we suggest that they affect methane oxidation in the water column at other sites, too.
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    Biological ramifications of climate-change-mediated oceanic multi-stressors (2015)
    Nature Publishing Group
    In:  Nature Climate Change, 5 (1). pp. 71-79.
    Details
    Publication Date: 2017-02-24
    Description: Climate change is altering oceanic conditions in a complex manner, and the concurrent amendment of multiple properties will modify environmental stress for primary producers. So far, global modelling studies have focused largely on how alteration of individual properties will affect marine life. Here, we use global modelling simulations in conjunction with rotated factor analysis to express model projections in terms of regional trends in concomitant changes to biologically influential multi-stressors. Factor analysis demonstrates that regionally distinct patterns of complex oceanic change are evident globally. Preliminary regional assessments using published evidence of phytoplankton responses to complex change reveal a wide range of future responses to interactive multi-stressors with 〈20–300% shifts in phytoplankton physiological rates, and many unexplored potential interactions. In a future ocean, provinces will encounter different permutations of change that will probably alter the dominance of key phytoplankton groups and modify regional productivity, ecosystem structure and biogeochemistry. Consideration of regionally distinct multi-stressor patterns can help guide laboratory and field studies as well as the interpretation of interactive multi-stressors in global models.
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    Lessons learned from ocean acidification research (2015)
    Nature Publishing Group
    In:  Nature Climate Change, 5 (1). pp. 12-14.
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    Publication Date: 2017-04-13
    Description: Reflection on the rapidly growing field of ocean acidification research highlights priorities for future research on the changing ocean.
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    Continental crust generated in oceanic arcs (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (4). pp. 321-327.
    Details
    Publication Date: 2017-12-19
    Description: Thin oceanic crust is formed by decompression melting of the upper mantle at mid-ocean ridges, but the origin of the thick and buoyant continental crust is enigmatic. Juvenile continental crust may form from magmas erupted above intraoceanic subduction zones, where oceanic lithosphere subducts beneath other oceanic lithosphere. However, it is unclear why the subduction of dominantly basaltic oceanic crust would result in the formation of andesitic continental crust at the surface. Here we use geochemical and geophysical data to reconstruct the evolution of the Central American land bridge, which formed above an intra-oceanic subduction system over the past 70Myr. We find that the geochemical signature of erupted lavas evolved from basaltic to andesitic about 10Myr ago - coincident with the onset of subduction of more oceanic crust that originally formed above the Galápagos mantle plume. We also find that seismic P-waves travel through the crust at velocities intermediate between those typically observed for oceanic and continental crust. We develop a continentality index to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust globally. We conclude that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone - a process probably more common in the Archaean - can produce juvenile continental crust.
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    Evolution of extreme stomach pH in bilateria inferred from gastric alkalization mechanisms in basal deuterostomes (2015)
    Nature Publishing Group
    In:  Scientific Reports, 5 (10421).
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    Publication Date: 2017-12-19
    Description: The stomachs of most vertebrates operate at an acidic pH of 2 generated by the gastric H+/K+-ATPase located in parietal cells. The acidic pH in stomachs of vertebrates is believed to aid digestion and to protect against environmental pathogens. Little attention has been placed on whether acidic gastric pH regulation is a vertebrate character or a deuterostome ancestral trait. Here, we report alkaline conditions up to pH 10.5 in the larval digestive systems of ambulacraria (echinoderm + hemichordate), the closest relative of the chordate. Microelectrode measurements in combination with specific inhibitors for acid-base transporters and ion pumps demonstrated that the gastric alkalization machinery in sea urchin larvae is mainly based on direct H+ secretion from the stomach lumen and involves a conserved set of ion pumps and transporters. Hemichordate larvae additionally utilized HCO 3- transport pathways to generate even more alkaline digestive conditions. Molecular analyses in combination with acidification experiments supported these findings and identified genes coding for ion pumps energizing gastric alkalization. Given that insect larval guts were also reported to be alkaline, our discovery raises the hypothesis that the bilaterian ancestor utilized alkaline digestive system while the vertebrate lineage has evolved a strategy to strongly acidify their stomachs.
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    The effect of nutrients on carbon and nitrogen fixation by the UCYN-A–haptophyte symbiosis (2015)
    Nature Publishing Group
    In:  The ISME Journal, 9 (7). pp. 1635-1647.
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    Publication Date: 2015-07-16
    Description: Symbiotic relationships between phytoplankton and N-2-fixing microorganisms play a crucial role in marine ecosystems. The abundant and widespread unicellular cyanobacteria group A (UCYN-A) has recently been found to live symbiotically with a haptophyte. Here, we investigated the effect of nitrogen (N), phosphorus (P), iron (Fe) and Saharan dust additions on nitrogen (N-2) fixation and primary production by the UCYN-A-haptophyte association in the subtropical eastern North Atlantic Ocean using nifH expression analysis and stable isotope incubations combined with single-cell measurements. N-2 fixation by UCYN-A was stimulated by the addition of Fe and Saharan dust, although this was not reflected in the nifH expression. CO2 fixation by the haptophyte was stimulated by the addition of ammonium nitrate as well as Fe and Saharan dust. Intriguingly, the single-cell analysis using nanometer scale secondary ion mass spectrometry indicates that the increased CO2 fixation by the haptophyte in treatments without added fixed N is likely an indirect result of the positive effect of Fe and/or P on UCYN-A N-2 fixation and the transfer of N-2-derived N to the haptophyte. Our results reveal a direct linkage between the marine carbon and nitrogen cycles that is fuelled by the atmospheric deposition of dust. The comparison of single-cell rates suggests a tight coupling of nitrogen and carbon transfer that stays balanced even under changing nutrient regimes. However, it appears that the transfer of carbon from the haptophyte to UCYN-A requires a transfer of nitrogen from UCYN-A. This tight coupling indicates an obligate symbiosis of this globally important diazotrophic association.
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    Solar forcing synchronizes decadal North Atlantic climate variability (2015)
    Nature Publishing Group
    In:  Nature Communications, 6 (8268).
    Details
    Publication Date: 2017-04-12
    Description: Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth’s regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1–2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface.
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    Boundaries of the Peruvian oxygen minimum zone shaped by coherent mesoscale dynamics (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (12). pp. 937-940.
    Details
    Publication Date: 2017-02-20
    Description: Dissolved oxygen in sea water affects marine habitats and biogeochemical cycles. Oceanic zones with oxygen deficits represent 7% of the volume and 8% of the area of the oceans, and are thought to be expanding. One of the most pronounced lies in the region off Peru, where mesoscale activity in the form of fronts and eddies is strong. Here, we study the dynamics of the Peruvian oxygen minimum zone in a Lagrangian framework, using a coupled physical-biogeochemical numerical model and finite-size Lyapunov exponent fields, to evaluate the role of mesoscale activity. We find that, at depths between 380 and 600 m, mesoscale structures have two distinct roles. First, their mean positions and paths delimit and maintain the oxygen minimum zone boundaries. Second, their high-frequency fluctuations inject oxygen across the oxygen minimum zone boundaries and eddy fluxes are one order of magnitude higher than mean oxygen fluxes. We conclude that these eddy fluxes contribute to the ventilation of the Peruvian oxygen minimum zone.
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    Local adaptation constrains the distribution potential of heat-tolerant Symbiodinium from the Persian/Arabian Gulf (2015)
    Nature Publishing Group
    In:  The ISME Journal, 9 (12). pp. 2551-2560.
    Details
    Publication Date: 2021-04-23
    Description: The symbiotic association of corals and unicellular algae of the genus Symbiodinium in the southern Persian/Arabian Gulf (PAG) display an exceptional heat tolerance, enduring summer peak temperatures of up to 36 °C. As yet, it is not clear whether this resilience is related to the presence of specific symbiont types that are exclusively found in this region. Therefore, we used molecular markers to identify the symbiotic algae of three Porites species along 〉1000 km of coastline in the PAG and the Gulf of Oman and found that a recently described species, Symbiodinium thermophilum, is integral to coral survival in the southern PAG, the world’s hottest sea. Despite the geographic isolation of the PAG, we discovered that representatives of the S. thermophilum group can also be found in the adjacent Gulf of Oman providing a potential source of thermotolerant symbionts that might facilitate the adaptation of Indian Ocean populations to the higher water temperatures expected for the future. However, corals from the PAG associated with S. thermophilum show strong local adaptation not only to high temperatures but also to the exceptionally high salinity of their habitat. We show that their superior heat tolerance can be lost when these corals are exposed to reduced salinity levels common for oceanic environments elsewhere. Consequently, the salinity prevailing in most reefs outside the PAG might represent a distribution barrier for extreme temperature-tolerant coral/Symbiodinium associations from the PAG.
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    Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming (2015)
    Nature Publishing Group
    In:  Scientific Reports, 5 (8940).
    Details
    Publication Date: 2019-09-23
    Description: Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12 degrees latitudes featuring a steep temperature gradient between the northern (28.5 degrees N, 21-27 degrees C) and southern (16.5 degrees N, 28-33 degrees C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29 degrees C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals
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    Nitrogen Fuelling of the Pelagic Food Web of the Tropical Atlantic (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (6). e0131258.
    Details
    Publication Date: 2019-09-23
    Description: We estimated the relative contribution of atmosphere (ic Nitrogen (N) input (wet and dry deposition and N fixation) to the epipelagic food web by measuring N isotopes of different functional groups of epipelagic zooplankton along 23°W (17°N-4°S) and 18°N (20-24°W) in the Eastern Tropical Atlantic. Results were related to water column observations of nutrient distribution and vertical diffusive flux as well as colony abundance of Trichodesmium obtained with an Underwater Vision Profiler (UVP5). The thickness and depth of the nitracline and phosphocline proved to be significant predictors of zooplankton stable N isotope values. Atmospheric N input was highest (61% of total N) in the strongly stratified and oligotrophic region between 3 and 7°N, which featured very high depth-integrated Trichodesmium abundance (up to 9.4×104 colonies m-2), strong thermohaline stratification and low zooplankton δ15N (~2‰). Relative atmospheric N input was lowest south of the equatorial upwelling between 3 and 5°S (27%). Values in the Guinea Dome region and north of Cape Verde ranged between 45 and 50%, respectively. The microstructure-derived estimate of the vertical diffusive N flux in the equatorial region was about one order of magnitude higher than in any other area (approximately 8 mmol m-2 d 1). At the same time, this region received considerable atmospheric N input (35% of total). In general, zooplankton δ15N and Trichodesmium abundance were closely correlated, indicating that N fixation is the major source of atmospheric N input. Although Trichodesmium is not the only N fixing organism, its abundance can be used with high confidence to estimate the relative atmospheric N input in the tropical Atlantic (r2 = 0.95). Estimates of absolute N fixation rates are two- to tenfold higher than incubation-derived rates reported for the same regions. Our approach integrates over large spatial and temporal scales and also quantifies fixed N released as dissolved inorganic and organic N. In a global analysis, it may thus help to close the gap in oceanic N budgets.
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    Nitrate and Nitrite Variability at the Seafloor of an Oxygen Minimum Zone Revealed by a Novel Microfluidic In-Situ Chemical Sensor (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (7). e0132785.
    Details
    Publication Date: 2019-09-23
    Description: Microfluidics, or lab-on-a-chip (LOC) is a promising technology that allows the development of miniaturized chemical sensors. In contrast to the surging interest in biomedical sciences, the utilization of LOC sensors in aquatic sciences is still in infancy but a wider use of such sensors could mitigate the undersampling problem of ocean biogeochemical processes. Here we describe the first underwater test of a novel LOC sensor to obtain in situ calibrated time-series (up to 40 h) of nitrate+nitrite (ΣNOx) and nitrite on the seafloor of the Mauritanian oxygen minimum zone, offshore Western Africa. Initial tests showed that the sensor successfully reproduced water column (160 m) nutrient profiles. Lander deployments at 50, 100 and 170 m depth indicated that the biogeochemical variability was high over the Mauritanian shelf: The 50 m site had the lowest ΣNOx concentration, with 15.2 to 23.4 μM (median=18.3 μM); while at the 100 site ΣNOx varied between 21.0 and 30.1 μM over 40 hours (median = 25.1μM). The 170 m site had the highest median ΣNOx level (25.8 μM) with less variability (22.8 to 27.7 μM). At the 50 m site, nitrite concentration decreased fivefold from 1 to 0.2 μM in just 30 hours accompanied by decreasing oxygen and increasing nitrate concentrations. Taken together with the time series of oxygen, temperature, pressure and current velocities, we propose that the episodic intrusion of deeper waters via cross-shelf transport leads to intrusion of nitrate-rich, but oxygen-poor waters to shallower locations, with consequences for benthic nitrogen cycling. This first validation of an LOC sensor at elevated water depths revealed that when deployed for longer periods and as a part of a sensor network, LOC technology has the potential to contribute to the understanding of the benthic biogeochemical dynamics.
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    Crucial role of Black Sea warming in amplifying the 2012 Krymsk precipitation extreme (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (8). pp. 615-619.
    Details
    Publication Date: 2017-04-12
    Description: Over the past 60 years, both average daily precipitation intensity and extreme precipitation have increased in many regions1, 2, 3. Part of these changes, or even individual events4, 5, have been attributed to anthropogenic warming6, 7. Over the Black Sea and Mediterranean region, the potential for extreme summertime convective precipitation has grown8 alongside substantial sea surface temperature increase. A particularly devastating convective event experienced in that region was the July 2012 precipitation extreme near the Black Sea town of Krymsk9. Here we study the effect of sea surface temperature (SST) increase on convective extremes within the region, taking the Krymsk event as a showcase example. We carry out ensemble sensitivity simulations with a convection-permitting atmospheric model and show the crucial role of SST increase in the extremeness of the event. The enhancement of lower tropospheric instability due to the current warmer Black Sea allows deep convection to be triggered, increasing simulated precipitation by more than 300% relative to simulations with SSTs characteristic of the early 1980s. A highly nonlinear precipitation response to incremental SST increase suggests that the Black Sea has exceeded a regional threshold for the intensification of convective extremes. The physical mechanism we identify indicates that Black Sea and Mediterranean coastal regions may face abrupt amplifications of convective precipitation under continued SST increase, and illustrates the limitations of thermodynamical bounds for estimating the temperature scaling of convective extremes.
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    Identification of Habitat-Specific Biomes of Aquatic Fungal Communities Using a Comprehensive Nearly Full-Length 18S rRNA Dataset Enriched with Contextual Data (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (7). e0134377.
    Details
    Publication Date: 2020-10-26
    Description: Molecular diversity surveys have demonstrated that aquatic fungi are highly diverse, and that they play fundamental ecological roles in aquatic systems. Unfortunately, comparative studies of aquatic fungal communities are few and far between, due to the scarcity of adequate datasets. We combined all publicly available fungal 18S ribosomal RNA (rRNA) gene sequences with new sequence data from a marine fungi culture collection. We further enriched this dataset by adding validated contextual data. Specifically, we included data on the habitat type of the samples assigning fungal taxa to ten different habitat categories. This dataset has been created with the intention to serve as a valuable reference dataset for aquatic fungi including a phylogenetic reference tree. The combined data enabled us to infer fungal community patterns in aquatic systems. Pairwise habitat comparisons showed significant phylogenetic differences, indicating that habitat strongly affects fungal community structure. Fungal taxonomic composition differed considerably even on phylum and class level. Freshwater fungal assemblage was most different from all other habitat types and was dominated by basal fungal lineages. For most communities, phylogenetic signals indicated clustering of sequences suggesting that environmental factors were the main drivers of fungal community structure, rather than species competition. Thus, the diversification process of aquatic fungi must be highly clade specific in some cases.The combined data enabled us to infer fungal community patterns in aquatic systems. Pairwise habitat comparisons showed significant phylogenetic differences, indicating that habitat strongly affects fungal community structure. Fungal taxonomic composition differed considerably even on phylum and class level. Freshwater fungal assemblage was most different from all other habitat types and was dominated by basal fungal lineages. For most communities, phylogenetic signals indicated clustering of sequences suggesting that environmental factors were the main drivers of fungal community structure, rather than species competition. Thus, the diversification process of aquatic fungi must be highly clade specific in some cases.
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    Subducting seamounts control interplate coupling and seismic rupture in the 2014 Iquique earthquake area (2015)
    Nature Publishing Group
    In:  Nature Communications, 6 . p. 8267.
    Details
    Publication Date: 2017-12-19
    Description: To date, the parameters that determine the rupture area of great subduction zone earthquakes remain contentious. On 1 April 2014, the Mw 8.1 Iquique earthquake ruptured a portion of the well-recognized northern Chile seismic gap but left large highly coupled areas un-ruptured. Marine seismic reflection and swath bathymetric data indicate that structural variations in the subducting Nazca Plate control regional-scale plate-coupling variations, and the limited extent of the 2014 earthquake. Several under-thrusting seamounts correlate to the southward and up-dip arrest of seismic rupture during the 2014 Iquique earthquake, thus supporting a causal link. By fracturing of the overriding plate, the subducting seamounts are likely further responsible for reduced plate-coupling in the shallow subduction zone and in a lowly coupled region around 20.5°S. Our data support that structural variations in the lower plate influence coupling and seismic rupture offshore Northern Chile, whereas the structure of the upper plate plays a minor role.
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    Establishing functional relationships between abiotic environment, macrophyte coverage, resource gradients and the distribution of Mytilus trossulus in a brackish non-tidal environment (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (8). e0136949.
    Details
    Publication Date: 2015-12-16
    Description: Benthic suspension feeding mussels are an important functional guild in coastal and estua-rine ecosystems. To date we lack information on how various environmental gradients and biotic interactions separately and interactively shape the distribution patterns of mussels in non-tidal environments. Opposing to tidal environments, mussels inhabit solely subtidal zone in non-tidal waterbodies and, thereby, driving factors for mussel populations are expected to differ from the tidal areas. In the present study, we used the boosted regression tree modelling (BRT), an ensemble method for statistical techniques and machine learning, in order to explain the distribution and biomass of the suspension feeding mussel Mytilus trossulus in the non-tidal Baltic Sea. BRT models suggested that (1) distribution patterns of M. trossulus are largely driven by separate effects of direct environmental gradients and partly by interactive effects of resource gradients with direct environmental gradients. (2) Within its suitable habitat range, however, resource gradients had an important role in shaping the biomass distribution of M. trossulus. (3) Contrary to tidal areas, mussels were not competitively superior over macrophytes with patterns indicating either facilitative interactions between mussels and macrophytes or co-variance due to common stressor. To conclude, direct environmental gradients seem to define the distribution pattern of M. trossulus, and within the favourable distribution range, resource gradients in interaction with direct environmental gradients are expected to set the biomass level of mussels.
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    Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (11). pp. 856-860.
    Details
    Publication Date: 2021-04-23
    Description: Oceanic dissolved organic carbon (DOC) is an important carbon pool, similar in magnitude to atmospheric CO2, but the fate of its oldest forms is not well understood. Hot hydrothermal circulation may facilitate the degradation of otherwise un-reactive dissolved organic matter, playing an important role in the long-term global carbon cycle. The oldest, most recalcitrant forms of DOC, which make up most of oceanic DOC, can be recovered by solid-phase extraction. Here we present measurements of solid-phase extractable DOC from samples collected between 2009 and 2013 at seven vent sites in the Atlantic, Pacific and Southern oceans, along with magnesium concentrations, a conservative tracer of water circulation through hydrothermal systems. We find that magnesium and solid-phase extractable DOC concentrations are correlated, suggesting that solid-phase extractable DOC is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212-401°C. In laboratory experiments, where we heated samples to 380°C for four days, we found a similar removal efficiency. We conclude that thermal degradation alone can account for the loss of solid-phase extractable DOC in natural hydrothermal systems, and that its maximum lifetime is constrained by the timescale of hydrothermal cycling, at about 40 million years
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    Biodiversity, Anti-Trypanosomal Activity Screening, and Metabolomic Profiling of Actinomycetes Isolated from Mediterranean Sponges (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (9). e0138528.
    Details
    Publication Date: 2017-04-13
    Description: Marine sponge–associated actinomycetes are considered as promising sources for the discovery of novel biologically active compounds. In the present study, a total of 64 actinomycetes were isolated from 12 different marine sponge species that had been collected offshore the islands of Milos and Crete, Greece, eastern Mediterranean. The isolates were affiliated to 23 genera representing 8 different suborders based on nearly full length 16S rRNA gene sequencing. Four putatively novel species belonging to genera Geodermatophilus, Microlunatus, Rhodococcus and Actinomycetospora were identified based on a 16S rRNA gene sequence similarity of 〈 98.5% to currently described strains. Eight actinomycete isolates showed bioactivities against Trypanosma brucei brucei TC221 with half maximal inhibitory concentration (IC50) values 〈20 μg/mL. Thirty four isolates from the Milos collection and 12 isolates from the Crete collection were subjected to metabolomic analysis using high resolution LC-MS and NMR for dereplication purposes. Two isolates belonging to the genera Streptomyces (SBT348) and Micromonospora (SBT687) were prioritized based on their distinct chemistry profiles as well as their anti-trypanosomal activities. These findings demonstrated the feasibility and efficacy of utilizing metabolomics tools to prioritize chemically unique strains from microorganism collections and further highlight sponges as rich source for novel and bioactive actinomycetes.
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    Discovery of symbiotic nitrogen fixation and chemoautotrophy in cold-water corals (2015)
    Nature Publishing Group
    In:  Scientific Reports, 5 . p. 17962.
    Details
    Publication Date: 2016-11-03
    Description: Cold-water corals (CWC) are widely distributed around the world forming extensive reefs at par with tropical coral reefs. They are hotspots of biodiversity and organic matter processing in the world’s deep oceans. Living in the dark they lack photosynthetic symbionts and are therefore considered to depend entirely on the limited flux of organic resources from the surface ocean. While symbiotic relations in tropical corals are known to be key to their survival in oligotrophic conditions, the full metabolic capacity of CWC has yet to be revealed. Here we report isotope tracer evidence for efficient nitrogen recycling, including nitrogen assimilation, regeneration, nitrification and denitrification. Moreover, we also discovered chemoautotrophy and nitrogen fixation in CWC and transfer of fixed nitrogen and inorganic carbon into bulk coral tissue and tissue compounds (fatty acids and amino acids). This unrecognized yet versatile metabolic machinery of CWC conserves precious limiting resources and provides access to new nitrogen and organic carbon resources that may be essential for CWC to survive in the resource-depleted dark ocean.
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    Atlantic multi-decadal oscillation covaries with Agulhas leakage (2015)
    Nature Publishing Group
    In:  Nature Communications, 6 (10082).
    Details
    Publication Date: 2019-02-25
    Description: The interoceanic transfer of seawater between the Indian Ocean and the Atlantic, ‘Agulhas leakage’, forms a choke point for the overturning circulation in the global ocean. Here, by combining output from a series of high-resolution ocean and climate models with in situ and satellite observations, we construct a time series of Agulhas leakage for the period 1870–2014. The time series demonstrates the impact of Southern Hemisphere westerlies on decadal timescales. Agulhas leakage shows a correlation with the Atlantic Multi-decadal Oscillation on multi-decadal timescales; the former leading by 15 years. This is relevant for climate in the North Atlantic
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    Effects of long-term variability on projections of twenty-first century dynamic sea level (2015)
    Nature Publishing Group
    In:  Nature Climate Change, 5 (4). pp. 343-347.
    Details
    Publication Date: 2017-04-13
    Description: Sea-level rise1 is one of the most pressing aspects of anthropogenic global warming with far-reaching consequences for coastal societies. However, sea-level rise did2, 3, 4, 5, 6, 7 and will strongly vary from coast to coast8, 9, 10. Here we investigate the long-term internal variability effects on centennial projections of dynamic sea level (DSL), the local departure from the globally averaged sea level. A large ensemble of global warming integrations has been conducted with a climate model, where each realization was forced by identical CO2 increase but started from different atmospheric and oceanic initial conditions. In large parts of the mid- and high latitudes, the ensemble spread of the projected centennial DSL trends is of the same order of magnitude as the globally averaged steric sea-level rise, suggesting that internal variability cannot be ignored when assessing twenty-first-century DSL trends. The ensemble spread is considerably reduced in the mid- to high latitudes when only the atmospheric initial conditions differ while keeping the oceanic initial state identical; indicating that centennial DSL projections are strongly dependent on ocean initial conditions.
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    Policy: Five priorities for the UN Sustainable Development Goals - Comment (2015)
    Nature Publishing Group
    In:  Nature, 520 (7548). pp. 432-433.
    Details
    Publication Date: 2019-09-23
    Description: Restructure data-gathering and evaluation networks to address climate change, energy, food, health and water provision, say Yonglong Lu and colleagues.
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    Pacific origin of the abrupt increase in Indian Ocean heat content during the warming hiatus (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (6). pp. 445-449.
    Details
    Publication Date: 2017-12-19
    Description: Global mean surface warming has stalled since the end of the twentieth century1, 2, but the net radiation imbalance at the top of the atmosphere continues to suggest an increasingly warming planet. This apparent contradiction has been reconciled by an anomalous heat flux into the ocean3, 4, 5, 6, 7, 8, induced by a shift towards a La Niña-like state with cold sea surface temperatures in the eastern tropical Pacific over the past decade or so. A significant portion of the heat missing from the atmosphere is therefore expected to be stored in the Pacific Ocean. However, in situ hydrographic records indicate that Pacific Ocean heat content has been decreasing9. Here, we analyse observations along with simulations from a global ocean–sea ice model to track the pathway of heat. We find that the enhanced heat uptake by the Pacific Ocean has been compensated by an increased heat transport from the Pacific Ocean to the Indian Ocean, carried by the Indonesian throughflow. As a result, Indian Ocean heat content has increased abruptly, which accounts for more than 70% of the global ocean heat gain in the upper 700 m during the past decade. We conclude that the Indian Ocean has become increasingly important in modulating global climate variability.
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    Ocean science: The origins of a climate oscillation (2015)
    Nature Publishing Group
    In:  Nature, 521 (7553). pp. 428-430.
    Details
    Publication Date: 2017-12-19
    Description: An index of water-circulation strength in the North Atlantic Ocean has been derived from sea-level measurements. This provides fresh evidence of the ocean's leading role in multidecadal climate variability. See Letter p.508
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    How and when plume zonation appeared during the 132 Myr evolution of the Tristan Hotspot (2015)
    Nature Publishing Group
    In:  Nature Communications, 6 (7799).
    Details
    Publication Date: 2019-09-23
    Description: Increasingly, spatial geochemical zonation, present as geographically distinct, subparallel trends, is observed along hotspot tracks, such as Hawaii and the Galapagos. The origin of this zonation is currently unclear. Recently zonation was found along the last B70 Myr of the Tristan-Gough hotspot track. Here we present new Sr–Nd–Pb–Hf isotope data from the older parts of this hotspot track (Walvis Ridge and Rio Grande Rise) and re-evaluate published data from the Etendeka and Parana flood basalts erupted at the initiation of the hotspot track. We show that only the enriched Gough, but not the less-enriched Tristan, component is present in the earlier (70–132 Ma) history of the hotspot. Here we present a model that can explain the temporal evolution and origin of plume zonation for both the Tristan-Gough and Hawaiian hotspots, two end member types of zoned plumes, through processes taking place in the plume sources at the base of the lower mantle.
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    Ocean acidification increases the accumulation of toxic phenolic compounds across trophic levels (2015)
    Nature Publishing Group
    In:  Nature Communications, 6 (8714).
    Details
    Publication Date: 2019-09-23
    Description: Increasing atmospheric CO2 concentrations are causing ocean acidification (OA), altering carbonate chemistry with consequences for marine organisms. Here we show that OA increases by 46–212% the production of phenolic compounds in phytoplankton grown under the elevated CO2 concentrations projected for the end of this century, compared with the ambient CO2 level. At the same time, mitochondrial respiration rate is enhanced under elevated CO2 concentrations by 130–160% in a single species or mixed phytoplankton assemblage. When fed with phytoplankton cells grown under OA, zooplankton assemblages have significantly higher phenolic compound content, by about 28–48%. The functional consequences of the increased accumulation of toxic phenolic compounds in primary and secondary producers have the potential to have profound consequences for marine ecosystem and seafood quality, with the possibility that fishery industries could be influenced as a result of progressive ocean changes
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    Proteomic Analysis of Anti-Cancerous Scopularide Production by a Marine Microascus brevicaulis Strain and Its UV Mutant (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (10). e0140047.
    Details
    Publication Date: 2019-09-23
    Description: The marine fungus Microascus brevicaulis strain LF580 is a non-model secondary metabolite producer with high yields of the two secondary metabolites scopularides A and B, which exhibit distinct activities against tumour cell lines. A mutant strain was obtained using UV mutagenesis, showing faster growth and differences in pellet formation besides higher production levels. Here, we show the first proteome study of a marine fungus. Comparative proteomics were applied to gain deeper understanding of the regulation of production and of the physiology of the wild type strain and its mutant. For this purpose, an optimised protein extraction protocol was established. In total, 4759 proteins were identified. The central metabolic pathway of strain LF580 was mapped using the KEGG pathway analysis and GO annotation. Employing iTRAQ labelling, 318 proteins were shown to be significantly regulated in the mutant strain: 189 were down- and 129 upregulated. Proteomics are a powerful tool for the understanding of regulatory aspects: The differences on proteome level could be attributed to limited nutrient availability in the wild type strain due to a strong pellet formation. This information can be applied for optimisation on strain and process level. The linkage between nutrient limitation and pellet formation in the non-model fungus M. brevicaulis is in consensus with the knowledge on model organisms like Aspergillus niger and Penicillium chrysogenum
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    Diversity of key players in the microbial ecosystems of the human body (2015)
    Nature Publishing Group
    In:  Scientific Reports, 5 . p. 15920.
    Details
    Publication Date: 2020-11-09
    Description: Coexisting bacteria form various microbial communities in human body parts. In these ecosystems they interact in various ways and the properties of the interaction network can be related to the stability and functional diversity of the local bacterial community. In this study, we analyze the interaction network among bacterial OTUs in 11 locations of the human body. These belong to two major groups. One is the digestive system and the other is the female genital tract. In each local ecosystem we determine the key species, both the ones being in key positions in the interaction network and the ones that dominate by frequency. Beyond identifying the key players and discussing their biological relevance, we also quantify and compare the properties of the 11 networks. The interaction networks of the female genital system and the digestive system show totally different architecture. Both the topological properties and the identity of the key groups differ. Key groups represent four phyla of prokaryotes. Some groups appear in key positions in several locations, while others are assigned only to a single body part. The key groups of the digestive and the genital tracts are totally different.
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    Institutional coordination of global ocean observations (2015)
    Nature Publishing Group
    In:  Nature Climate Change, 5 (1). pp. 4-6.
    Details
    Publication Date: 2019-09-23
    Description: A sustainable global ocean observation system requires timely implementation of the framework for ocean observing. The recent Qingdao Global Ocean Summit highlighted the need for a more coherent institutional response to maintain an integrated ocean-observing system.
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    Ocean currents generate large footprints in marine palaeoclimate proxies (2015)
    Nature Publishing Group
    In:  Nature Communications, 6 (6521).
    Details
    Publication Date: 2019-02-25
    Description: Fossils of marine microorganisms such as planktic foraminifera are among the cornerstones of palaeoclimatological studies. It is often assumed that the proxies derived from their shells represent ocean conditions above the location where they were deposited. Planktic foraminifera, however, are carried by ocean currents and, depending on the life traits of the species, potentially incorporate distant ocean conditions. Here we use high-resolution ocean models to assess the footprint of planktic foraminifera and validate our method with proxy analyses from two locations. Results show that foraminifera, and thus recorded palaeoclimatic conditions, may originate from areas up to several thousands of kilometres away, reflecting an ocean state significantly different from the core site. In the eastern equatorial regions and the western boundary current extensions, the offset may reach 1.5 °C for species living for a month and 3.0 °C for longer-living species. Oceanic transport hence appears to be a crucial aspect in the interpretation of proxy signals.
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    Hemolymph microbiome of Pacific oysters in response to temperature, temperature stress and infection (2015)
    Nature Publishing Group
    In:  The ISME Journal, 9 (3). pp. 670-682.
    Details
    Publication Date: 2017-04-13
    Description: Microbiota provide their hosts with a range of beneficial services, including defense from external pathogens. However, host-associated microbial communities themselves can act as a source of opportunistic pathogens depending on the environment. Marine poikilotherms and their microbiota are strongly influenced by temperature, but experimental studies exploring how temperature affects the interactions between both parties are rare. To assess the effects of temperature, temperature stress and infection on diversity, composition and dynamics of the hemolymph microbiota of Pacific oysters (Crassostrea gigas), we conducted an experiment in a fully-crossed, three-factorial design, in which the temperature acclimated oysters (8 or 22 °C) were exposed to temperature stress and to experimental challenge with a virulent Vibrio sp. Strain. We monitored oyster survival and repeatedly collected hemolymph of dead and alive animals to determine the microbiome composition by 16s rRNA gene amplicon pyrosequencing. We found that the microbial dynamics and composition of communities in healthy animals (including infection survivors) were significantly affected by temperature and temperature stress, but not by infection. The response was mediated by changes in the incidence and abundance of operational taxonomic units (OTUs) and accompanied by little change at higher taxonomic levels, indicating dynamic stability of the hemolymph microbiome. Dead and moribund oysters, on the contrary, displayed signs of community structure disruption, characterized by very low diversity and proliferation of few OTUs. We can therefore link short-term responses of host-associated microbial communities to abiotic and biotic factors and assess the potential feedback between microbiota dynamics and host survival during disease.
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    Fossil fuels in a trillion tonne world (2015)
    Nature Publishing Group
    In:  Nature Climate Change, 5 (5). pp. 419-423.
    Details
    Publication Date: 2017-12-19
    Description: The useful energy services and energy density value of fossil carbon fuels could be retained for longer timescales into the future if their combustion is balanced by CO2 recapture and storage. We assess the global balance between fossil carbon supply and the sufficiency (size) and capability (technology, security) of candidate carbon stores. A hierarchy of value for extraction-to-storage pairings is proposed, which is augmented by classification of CO2 containment as temporary (〈1,000 yr) or permanent (〉100,000 yr). Using temporary stores is inefficient and defers an intergenerational problem. Permanent storage capacity is adequate to technically match current fossil fuel reserves. However, rates of storage creation cannot balance current and expected rates of fossil fuel extraction and CO2 consequences. Extraction of conventional natural gas is uniquely holistic because it creates the capacity to re-inject an equivalent tonnage of carbon for storage into the same reservoir and can re-use gas-extraction infrastructure for storage. By contrast, balancing the extraction of coal, oil, biomass and unconventional fossil fuels requires the engineering and validation of additional carbon storage. Such storage is, so far, unproven in sufficiency.
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    Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian–Emperor bend (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (5). pp. 393-397.
    Details
    Publication Date: 2019-09-23
    Description: Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor and some might instead be caused by cracks in the oceanic crust linked to the reorganization of plate motions. A distinctive bend in the Hawaiian–Emperor volcanic chain has been linked to changes in the direction of motion of the Pacific Plate, movement of the Hawaiian plume, or a combination of both. However, these links are uncertain because there is no independent record that precisely dates tectonic events that affected the Pacific Plate. Here we analyse the geochemical characteristics of lava samples collected from the Musicians Ridges, lines of volcanic seamounts formed close to the Hawaiian–Emperor bend. We find that the geochemical signature of these lavas is unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. We infer that the seamounts are unrelated to mantle plume activity and instead formed in an extensional setting, due to deformation of the Pacific Plate. 40Ar/39Ar dating reveals that the Musicians Ridges formed during two time windows that bracket the time of formation of the Hawaiian–Emperor bend, 53–52 and 48–47 million years ago. We conclude that the Hawaiian–Emperor bend was formed by plate–mantle reorganization, potentially triggered by a series of subduction events at the Pacific Plate margins.
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    Long-Term Conditioning to Elevated pCO2 and Warming Influences the Fatty and Amino Acid Composition of the Diatom Cylindrotheca fusiformis (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (5). e0123945.
    Details
    Publication Date: 2017-04-13
    Description: The unabated rise in anthropogenic CO2 emissions is predicted to strongly influence the ocean's environment, increasing the mean sea-surface temperature by 4°C and causing a pH decline of 0.3 units by the year 2100. These changes are likely to affect the nutritional value of marine food sources since temperature and CO2 can influence the fatty (FA) and amino acid (AA) composition of marine primary producers. Here, essential amino (EA) and polyunsaturated fatty (PUFA) acids are of particular importance due to their nutritional value to higher trophic levels. In order to determine the interactive effects of CO2 and temperature on the nutritional quality of a primary producer, we analyzed the relative PUFA and EA composition of the diatom Cylindrotheca fusiformis cultured under a factorial matrix of 2 temperatures (14 and 19°C) and 3 partial pressures of CO2 (180, 380, 750 μatm) for 〉250 generations. Our results show a decay of ∼3% and ∼6% in PUFA and EA content in algae kept at a pCO2 of 750 μatm (high) compared to the 380 μatm (intermediate) CO2 treatments at 14°C. Cultures kept at 19°C displayed a ∼3% lower PUFA content under high compared to intermediate pCO2, while EA did not show differences between treatments. Algae grown at a pCO2 of 180 μatm (low) had a lower PUFA and AA content in relation to those at intermediate and high CO2 levels at 14°C, but there were no differences in EA at 19°C for any CO2 treatment. This study is the first to report adverse effects of warming and acidification on the EA of a primary producer, and corroborates previous observations of negative effects of these stressors on PUFA. Considering that only ∼20% of essential biomolecules such as PUFA (and possibly EA) are incorporated into new biomass at the next trophic level, thepotential impacts of adverse effects of ocean warming and acidification at the base of the food web may be amplified towards higher trophic levels, which rely on them as source of essential biomolecules.
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    Warming and Ocean Acidification Effects on Phytoplankton - From Species Shifts to Size Shifts within Species in a Mesocosm Experiment (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (5). e0125239.
    Details
    Publication Date: 2017-04-13
    Description: While the isolated responses of marine phytoplankton to climate warming and to ocean acidification have been studied intensively, studies on the combined effect of both aspects of Global Change are still scarce. Therefore, we performed a mesocosm experiment with a factorial combination of temperature (9 and 15°C) and pCO2 (means: 439 ppm and 1040 ppm) with a natural autumn plankton community from the western Baltic Sea. Temporal trajectories of total biomass and of the biomass of the most important higher taxa followed similar patterns in all treatments. When averaging over the entire time course, phytoplankton biomass decreased with warming and increased with CO2 under warm conditions. The contribution of the two dominant higher phytoplankton taxa (diatoms and cryptophytes) and of the 4 most important species (3 diatoms, 1 cryptophyte) did not respond to the experimental treatments. Taxonomic composition of phytoplankton showed only responses at the level of subdominant and rare species. Phytoplankton cell sizes increased with CO2 addition and decreased with warming. Both effects were stronger for larger species. Warming effects were stronger than CO2 effects and tended to counteract each other. Phytoplankton communities without calcifying species and exposed to short-term variation of CO2 seem to be rather resistant to ocean acidification.
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    Points of significance: Bayesian statistics (2015)
    Nature Publishing Group
    In:  Nature Methods, 12 (5). pp. 377-378.
    Details
    Publication Date: 2020-06-24
    Description: Today’s predictions are tomorrow’s priors
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    The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions (2015)
    Public Library of Science
    In:  PLoS ONE, 10 (9). e0139421.
    Details
    Publication Date: 2019-07-11
    Description: During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequences
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    Long-term response of oceans to CO2 removal from the atmosphere (2015)
    Nature Publishing Group
    In:  Nature Climate Change, 5 (12). pp. 1107-1113.
    Details
    Publication Date: 2017-04-11
    Description: Carbon dioxide removal (CDR) from the atmosphere has been proposed as a measure for mitigating global warming and ocean acidification. To assess the extent to which CDR might eliminate the long-term consequences of anthropogenic CO2 emissions in the marine environment, we simulate the effect of two massive CDR interventions with CO2 extraction rates of 5 GtC yr(-1) and 25 GtC yr(-1), respectively, while CO2 emissions follow the extended RCP8.5 pathway. We falsify two hypotheses: the first being that CDR can restore pre-industrial conditions in the ocean by reducing the atmospheric CO2 concentration back to its pre-industrial level, and the second being that high CO2 emissions rates (RCP8.5) followed by CDR have long-term oceanic consequences that are similar to those of low emissions rates (RCP2.6). Focusing on pH, temperature and dissolved oxygen, we find that even after several centuries of CDR deployment, past CO2 emissions would leave a substantial legacy in the marine environment.
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    The re-emergence of natural products for drug discovery in the genomics era (2015)
    Nature Publishing Group
    In:  Nature Reviews Drug Discovery, 14 (2). pp. 111-129.
    Details
    Publication Date: 2020-06-23
    Description: Natural products have been a rich source of compounds for drug discovery. However, their use has diminished in the past two decades, in part because of technical barriers to screening natural products in high-throughput assays against molecular targets. Here, we review strategies for natural product screening that harness the recent technical advances that have reduced these barriers. We also assess the use of genomic and metabolomic approaches to augment traditional methods of studying natural products, and highlight recent examples of natural products in antimicrobial drug discovery and as inhibitors of protein–protein interactions. The growing appreciation of functional assays and phenotypic screens may further contribute to a revival of interest in natural products for drug discovery.
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    Genome-wide maps of recombination and chromosome segregation in human oocytes and embryos show selection for maternal recombination rates (2015)
    Nature Publishing Group
    In:  Nature Genetics, 47 (7). pp. 727-735.
    Details
    Publication Date: 2020-06-25
    Description: Crossover recombination reshuffies genes and prevents errors in segregation tha't Iead to extra or missing chromosomes (aneuploidy) in human eggs, a major cause of pregnancy failure and congenital disorders. Here we generate genome-wide maps of cro~sovers and chromosome segregation patterns by recovering all three products of single female meioses. Genotyping 〉4 millioninformative SNPs from 23 complete meioses allowed us to map 2,032 maternal and 1,342 paternal crossovers and to infer the segregation patterns of 529 chromosome pairs. We uncover a new reverse chromosome segregation pattern in which both homologsseparate their sister chromatids at meiosis I; detect selection for higher recombination rates in the female germ line by the elimination of aneuploid embryos; and report chromosomal drive against non recombinant chromatids at meiosis II. Collectively, our findings show !hat recombination not only affects homolog segregation at meiosis I but also the fate of sister chromatids at meiosis II.
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    A novel hydrogen oxidizer amidst the sulfur-oxidizing Thiomicrospira lineage (2015)
    Nature Publishing Group
    In:  The ISME Journal, 9 (3). pp. 696-707.
    Details
    Publication Date: 2019-01-17
    Description: Thiomicrospira species are ubiquitously found in various marine environments and appear particularly common in hydrothermal vent systems. Members of this lineage are commonly classified as sulfur-oxidizing chemolithoautotrophs. Although sequencing of Thiomicrospira crunogena's genome has revealed genes that encode enzymes for hydrogen uptake activity and for hydrogenase maturation and assembly, hydrogen uptake ability has so far not been reported for any Thiomicrospira species. We isolated a Thiomicrospira species (SP-41) from a deep sea hydrothermal vent and demonstrated that it can oxidize hydrogen. We show in vivo hydrogen consumption, hydrogen uptake activity in partially purified protein extracts and transcript abundance of hydrogenases during different growth stages. The ability of this strain to oxidize hydrogen opens up new perspectives with respect to the physiology of Thiomicrospira species that have been detected in hydrothermal vents and that have so far been exclusively associated with sulfur oxidation.
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    Microbiology: Exclusive networks in the sea (2015)
    Nature Publishing Group
    In:  Nature, 522 (7554). pp. 36-37.
    Details
    Publication Date: 2019-03-05
    Description: The identification of an exchange of nutrients and signalling molecules between a planktonic alga and a bacterium demonstrates that targeted mutualistic interactions occur across domains of life in the oceans. See Letter p.98
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    Ecophysiology of uncultivated marine euryarchaea is linked to particulate organic matter (2015)
    Nature Publishing Group
    In:  ISME Journal, 9 (8). pp. 1747-1763.
    Details
    Publication Date: 2019-03-05
    Description: Particles in aquatic environments host distinct communities of microbes, yet the evolution of particlespecialized taxa and the extent to which specialized microbial metabolism is associated with particles is largely unexplored. Here, we investigate the hypothesis that a widely distributed and uncultivated microbial group - the marine group II euryarchaea (MGII) - interacts with living and detrital particulate organic matter (POM) in the euphotic zone of the central California Current System. Using fluorescent in situ hybridization, we verified the association of euryarchaea with POM. We further quantified the abundance and distribution of MGII 16S ribosomal RNA genes in size-fractionated seawater samples and compared MGII functional capacity in metagenomes from the same fractions. The abundance of MGII in free-living and 〈3 μm fractions decreased with increasing distance from the coast, whereas MGII abundance in the 0.8-3 lm fraction remained constant. At several offshore sites, MGII abundance was highest in particle fractions, indicating that particle-attached MGII can outnumber free-living MGII under oligotrophic conditions. Compared with free-living MGII, the genome content of MGII in particleassociated fractions exhibits an increased capacity for surface adhesion, transcriptional regulation and catabolism of high molecular weight substrates. Moreover, MGII populations in POM fractions are phylogenetically distinct from and more diverse than free-living MGII. Eukaryotic phytoplankton additions stimulated MGII growth in bottle incubations, providing the first MGII net growth rate measurements. These ranged from 0.47 to 0.54 d-1. However, MGII were not recovered in wholegenome amplifications of flow-sorted picoeukaryotic phytoplankton and heterotrophic nanoflagellates, suggesting that MGII in particle fractions are not physically attached to living POM. Collectively, our results support a linkage between MGII ecophysiology and POM, implying that marine archaea have a role in elemental cycling through interactions with particles. © 2015 International Society for Microbial Ecology. All rights reserved.
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    Updating algal evolutionary relationships through plastid genome sequencing: did alveolate plastids emerge through endosymbiosis of an ochrophyte? (2015)
    Nature Publishing Group
    In:  Scientific Reports, 5 (1). Art.Nr. 10134.
    Details
    Publication Date: 2019-03-05
    Description: Algae with secondary plastids of a red algal origin, such as ochrophytes (photosynthetic stramenopiles), are diverse and ecologically important, yet their evolutionary history remains controversial. We sequenced plastid genomes of two ochrophytes, Ochromonas sp. CCMP1393 (Chrysophyceae) and Trachydiscus minutus (Eustigmatophyceae). A shared split of the clpC gene as well as phylogenomic analyses of concatenated protein sequences demonstrated that chrysophytes and eustigmatophytes form a clade, the Limnista, exhibiting an unexpectedly elevated rate of plastid gene evolution. Our analyses also indicate that the root of the ochrophyte phylogeny falls between the recently redefined Khakista and Phaeista assemblages. Taking advantage of the expanded sampling of plastid genome sequences, we revisited the phylogenetic position of the plastid of Vitrella brassicaformis, a member of Alveolata with the least derived plastid genome known for the whole group. The results varied depending on the dataset and phylogenetic method employed, but suggested that the Vitrella plastids emerged from a deep ochrophyte lineage rather than being derived vertically from a hypothetical plastid-bearing common ancestor of alveolates and stramenopiles. Thus, we hypothesize that the plastid in Vitrella, and potentially in other alveolates, may have been acquired by an endosymbiosis of an early ochrophyte.
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    Strong and deep Atlantic meridional overturning circulation during the last glacial cycle (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 517 (7532). pp. 73-76.
    Details
    Publication Date: 2019-09-23
    Description: Extreme, abrupt Northern Hemisphere climate oscillations during the last glacial cycle (140,000 years ago to present) were modulated by changes in ocean circulation and atmospheric forcing. However, the variability of the Atlantic meridional overturning circulation (AMOC), which has a role in controlling heat transport from low to high latitudes and in ocean CO2 storage, is still poorly constrained beyond the Last Glacial Maximum. Here we show that a deep and vigorous overturning circulation mode has persisted for most of the last glacial cycle, dominating ocean circulation in the Atlantic, whereas a shallower glacial mode with southern-sourced waters filling the deep western North Atlantic prevailed during glacial maxima. Our results are based on a reconstruction of both the strength and the direction of the AMOC during the last glacial cycle from a highly resolved marine sedimentary record in the deep western North Atlantic. Parallel measurements of two independent chemical water tracers (the isotope ratios of 231Pa/230Th and 143Nd/144Nd), which are not directly affected by changes in the global cycle, reveal consistent responses of the AMOC during the last two glacial terminations. Any significant deviations from this configuration, resulting in slowdowns of the AMOC, were restricted to centennial-scale excursions during catastrophic iceberg discharges of the Heinrich stadials. Severe and multicentennial weakening of North Atlantic Deep Water formation occurred only during Heinrich stadials close to glacial maxima with increased ice coverage, probably as a result of increased fresh-water input. In contrast, the AMOC was relatively insensitive to submillennial meltwater pulses during warmer climate states, and an active AMOC prevailed during Dansgaard–Oeschger interstadials (Greenland warm periods).
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    Aerobic Microbial Respiration In Oceanic Oxygen Minimum Zones (2015)
    Public Library of Science
    Details
    Publication Date: 2022-02-18
    Description: Oxygen minimum zones are major sites of fixed nitrogen loss in the ocean. Recent studies have highlighted the importance of anaerobic ammonium oxidation, anammox, in pelagic nitrogen removal. Sources of ammonium for the anammox reaction, however, remain controversial, as heterotrophic denitrification and alternative anaerobic pathways of organic matter remineralization cannot account for the ammonium requirements of reported anammox rates. Here, we explore the significance of microaerobic respiration as a source of ammonium during organic matter degradation in the oxygen-deficient waters off Namibia and Peru. Experiments with additions of double-labelled oxygen revealed high aerobic activity in the upper OMZs, likely controlled by surface organic matter export. Consistently observed oxygen consumption in samples retrieved throughout the lower OMZs hints at efficient exploitation of vertically and laterally advected, oxygenated waters in this zone by aerobic microorganisms. In accordance, metagenomic and metatranscriptomic analyses identified genes encoding for aerobic terminal oxidases and demonstrated their expression by diverse microbial communities, even in virtually anoxic waters. Our results suggest that microaerobic respiration is a major mode of organic matter remineralization and source of ammonium (~45-100%) in the upper oxygen minimum zones, and reconcile hitherto observed mismatches between ammonium producing and consuming processes therein.
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    Complementary effects of species and genetic diversity on productivity and stability of sown grasslands (2015)
    Nature Publishing Group
    Details
    Publication Date: 2022-09-21
    Description: Plant species diversity regulates the productivity1–3 and stability2,4 of natural ecosystems, along with their resilience to disturbance5,6. The influence of species diversity on the productivity of agronomic systems is less clear7–10. Plant genetic diversity is also suspected to influence ecosystem function3,11–14, although empirical evidence is scarce. Given the large range of genotypes that can be generated per species through artificial selection, genetic diversity is a potentially important leverage of productivity in cultivated systems. Here we assess the effect of species and genetic diversity on the production and sustainable supply of livestock fodder in sown grasslands, comprising single and multispecies assemblages characterized by different levels of genetic diversity, exposed to drought and non-drought conditions. Multispecies assemblages proved more productive than monocultures when subject to drought, regardless of the number of genotypes per species present. Conversely, the temporal stability of production increased only with the number of genotypes present under both drought and non-drought conditions, and was unaffected by the number of species. We conclude that taxonomic and genetic diversity can play complementary roles when it comes to optimizing livestock fodder production in managed grasslands, and suggest that both levels of diversity should be considered in plant breeding programmes designed to boost the productivity and resilience of managed grasslands in the face of increasing environmental hazards.
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    Massive nitrous oxide emissions from the tropical South Pacific Ocean (2015)
    Nature Publishing Group
    Details
    Publication Date: 2023-09-19
    Description: Nitrous oxide is a potent greenhouse gas and a key compound in stratospheric ozone depletion. In the ocean, nitrous oxide is produced at intermediate depths through nitrification and denitrification, in particular at low oxygen concentrations. Although a third of natural emissions of nitrous oxide to the atmosphere originate from the ocean, considerable uncertainties in the distribution and magnitude of the emissions still exist. Here we present high-resolution surface measurements and vertical profiles of nitrous oxide that include the highest reported nitrous oxide concentrations in marine surface waters, suggesting that there is a hotspot of nitrous oxide emissions in high-productivity upwelling ecosystems along the Peruvian coast. We estimate that off Peru, the extremely high nitrous oxide supersaturations we observed drive a massive efflux of 0.2–0.9 Tg of nitrogen emitted as nitrous oxide per year, equivalent to 5–22% of previous estimates of global marine nitrous oxide emissions. Nutrient and gene abundance data suggest that coupled nitrification–denitrification in the upper oxygen minimum zone and transport of resulting nitrous oxide to the surface by upwelling lead to the high nitrous oxide concentrations. Our estimate of nitrous oxide emissions from the Peruvian coast surpasses values from similar, highly productive areas.
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    A function-based screen for seeking RubisCO active clones from metagenomes: novel enzymes influencing RubisCO activity (2015)
    Nature Publishing Group
    Details
    Publication Date: 2023-11-29
    Description: Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) is a key enzyme of the Calvin cycle, which is responsible for most of Earth's primary production. Although research on RubisCO genes and enzymes in plants, cyanobacteria and bacteria has been ongoing for years, still little is understood about its regulation and activation in bacteria. Even more so, hardly any information exists about the function of metagenomic RubisCOs and the role of the enzymes encoded on the flanking DNA owing to the lack of available function-based screens for seeking active RubisCOs from the environment. Here we present the first solely activity-based approach for identifying RubisCO active fosmid clones from a metagenomic library. We constructed a metagenomic library from hydrothermal vent fluids and screened 1056 fosmid clones. Twelve clones exhibited RubisCO activity and the metagenomic fragments resembled genes from Thiomicrospira crunogena. One of these clones was further analyzed. It contained a 35.2 kb metagenomic insert carrying the RubisCO gene cluster and flanking DNA regions. Knockouts of twelve genes and two intergenic regions on this metagenomic fragment demonstrated that the RubisCO activity was significantly impaired and was attributed to deletions in genes encoding putative transcriptional regulators and those believed to be vital for RubisCO activation. Our new technique revealed a novel link between a poorly characterized gene and RubisCO activity. This screen opens the door to directly investigating RubisCO genes and respective enzymes from environmental samples.
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