ALBERT

Description: Background: The microbiota of multicellular organisms undergoes considerable changes during host ontogeny but the general mechanisms that control community assembly and succession are poorly understood. Here, we use bacterial recolonization experiments in Nematostella vectensis as a model to understand general mechanisms determining bacterial establishment and succession. We compared the dynamic establishment of the microbiome on the germfree host and on inert silicone tubes. Results: Following the dynamic reconstruction of microbial communities on both substrates, we show that the initial colonization events are strongly influenced by the host but not by the silicone tube, while the subsequent bacteria-bacteria interactions are the main driver of bacterial succession. Interestingly, the recolonization pattern on adult hosts resembles the ontogenetic colonization succession. This process occurs independently of the bacterial composition of the inoculum and can be followed at the level of individual bacteria. To identify potential metabolic traits associated with initial colonization success and potential metabolic interactions among bacteria associated with bacterial succession, we reconstructed the metabolic networks of bacterial colonizers based on their genomes. These analyses revealed that bacterial metabolic capabilities reflect the recolonization pattern, and the degradation of chitin might be a selection factor during early recolonization of the animal. Concurrently, transcriptomic analyses revealed that Nematostella possesses two chitin synthase genes, one of which is upregulated during early recolonization. Conclusions: Our results show that early recolonization events are strongly controlled by the host while subsequent colonization depends on metabolic bacteria-bacteria interactions largely independent of host ontogeny.

Description: The uptake of dissolved oxygen from the atmosphere via air-sea gas exchange and its physical transport away from the region of uptake are crucial for supplying oxygen to the deep ocean. This process takes place in a few key regions that feature intense oxygen uptake, deep water formation, and physical oxygen export. In this study we analyze one such region, the Labrador Sea, utilizing the World Ocean Database (WOD) to construct a 65–year oxygen content time series in the Labrador Sea Water (LSW) layer (0–2200 m). The data reveal decadal variability associated with the strength of deep convection, with a maximum anomaly of 27 mol m–2 in 1992. There is no long-term trend in the time series, suggesting that the mean oxygen uptake is balanced by oxygen export out of the region. We compared the time series with output from nine models of the Ocean Model Intercomparison Project phase 1 in the Climate Model Intercomparison Project phase 6, (CMIP6-OMIP1), and constructed a “model score” to evaluate how well they match oxygen observations. Most CMIP6-OMIP1 models score around 50/100 points and the highest score is 57/100 for the ensemble mean, suggesting that improvements are needed. All of the models underestimate the maximum oxygen content anomaly in the 1990s. One possible cause for this is the representation of air-sea gas exchange for oxygen, with all models underestimating the mean uptake by a factor of two or more. Unrealistically deep convection and biased mean oxygen profiles may also contribute to the mismatch. Refining the representation of these processes in climate models could be vital for enhanced predictions of deoxygenation. In the CMIP6-OMIP1 multi-model mean, oxygen uptake has its maximum in 1980–1992, followed by a decrease in 1994–2006. There is a concurrent decrease in export, but oxygen storage also changes between the two periods, with oxygen accumulated in the first period and drained out in the second. Consequently, the change in oxygen export (5%) is much less than that in uptake (28%), suggesting that newly ventilated LSW which remains in the formation region acts to buffer the linkage between air-sea gas exchange and oxygen export.

Description: Zooplankton and nekton organisms play multifaceted roles in marine ecosystems and are integral components of the ocean’s food web. By consuming a wide range of planktonic organisms and detrital matter, they directly impact the size-distribution of particles in the ocean by breaking large aggregates down to smaller fragments and by repackaging single phytoplankton cells into dense fecal pellets. Many zooplankton and nekton organisms also conduct diel vertical migrations (DVM). They ascend to the surface layer of the ocean at dusk to feed during the dark hours and return to midwater depths at dawn to hide from visual predation. As they metabolize and excrete organic material in deeper waters, they contribute to an “active flux” of carbon and nutrients. This active flux can have a substantial impact on the functioning of the biological pump — the process responsible for the downward export of carbon and nutrients into the ocean’s interior. In essence, zooplankton and nekton are gatekeepers of the biological pump via their diverse roles in particle dynamics, from consumption and fragmentation to the active transport of organic matter. Understanding these roles is critical for unraveling the complex mechanisms that govern the health and functioning of marine ecosystems, as well as for improving our models of global biogeochemical processes in the world’s oceans.

Description: Have you ever wondered if today’s oceans were different millions of years ago? Well, a group of small algae called diatoms can help us to find this out. Diatoms build a strong glass skeleton, like a shell, which can last for thousands and even millions of years after their deaths. To build their glass skeletons, diatoms take up silicon from the seawater, similar to us eating food to build our bodies. Diatoms preferentially use one type of silicon in their menu, leaving behind the type they do not like. Researchers can track this eating habit by measuring the proportion of the two types of silicon stored within diatoms. Using this silica-print like a fingerprint, scientists can investigate what the surface ocean was like, how much diatoms were eating silicon, and how these organisms have affected Earth’s past climate.

Description: Seagrass meadows have a disproportionally high organic carbon (Corg) storage potential within their sediments and thus can play a role in climate change mitigation via their conservation and restoration. However, high spatial heterogeneity is observed in Corg, with wide differences seen globally, regionally, and even locally (within a seagrass meadow). Consequently, it is difficult to determine their contributions to the national remaining carbon dioxide (CO2) budget without introducing a large degree of uncertainty. To address this spatial heterogeneity, we sampled 20 locations across the German Baltic Sea to quantify Corg stocks and sources in Zostera marina seagrass-vegetated and adjacent unvegetated sediments. To predict and integrate the Corg inventory in space, we measured the physical (seawater depth, sediment grain size, current velocity at the seafloor, anthropogenic inputs) and biological (seagrass complexity) environments to determine regional and local drivers of Corg variation. Here, we show that seagrass meadows in Germany constitute a significant Corg stock, storing on average 7,785 g C/m2, 13 times greater than meadows from other parts of the Baltic Sea, and fourfold richer than adjacent unvegetated sediments. Stocks were highly heterogenous; they differed widely between (by 10-fold) and even within (by 3- to 55-fold) sites. Regionally, Corg was controlled by seagrass complexity, fine sediment fraction, and seawater depth. Autochthonous material contributed to 78% of the total Corg in seagrass-vegetated sediments, and the remaining 22% originated from allochthonous sources (phytoplankton and macroalgae). However, relic terrestrial peatland material, deposited approximately 6,000 years BP during the last deglaciation, was an unexpected and significant source of Corg. Collectively, German seagrasses in the Baltic Sea are preventing 8.14 Mt of future CO2 emissions. Because Corg is mostly produced on-site and not imported from outside the meadow boundaries, the richness of this pool may be contingent on seagrass habitat health. Disturbance of this Corg stock could act as a source of CO2 emissions. However, the high spatial heterogeneity warrants site-specific investigations to obtain accurate estimates of blue carbon and a need to consider millennial timescale deposits of Corg beneath seagrass meadows in Germany and potentially other parts of the southwestern Baltic Sea.

Description: The effect of anthropogenic climate change in the ocean is challenging to project because atmosphere-ocean general circulation models (AOGCMs) respond differently to forcing. This study focuses on changes in the Atlantic Meridional Overturning Circulation (AMOC), ocean heat content (Δ OHC), and the spatial pattern of ocean dynamic sea level (Δ ζ). We analyse experiments following the FAFMIP protocol, in which AOGCMs are forced at the ocean surface with standardised heat, freshwater and momentum flux perturbations, typical of those produced by doubling CO 2. Using two new heat-flux-forced experiments, we find that the AMOC weakening is mainly caused by and linearly related to the North Atlantic heat flux perturbation, and further weakened by a positive coupled heat flux feedback. The quantitative relationships are model-dependent, but few models show significant AMOC change due to freshwater or momentum forcing, or to heat flux forcing outside the North Atlantic. AMOC decline causes warming at the South Atlantic-Southern Ocean interface. It does not strongly affect the global-mean vertical distribution of Δ OHC, which is dominated by the Southern Ocean. AMOC decline strongly affects Δ ζ in the North Atlantic, with smaller effects in the Southern Ocean and North Pacific. The ensemble-mean Δ ζ and Δ OHC patterns are mostly attributable to the heat added by the flux perturbation, with smaller effects from ocean heat and salinity redistribution. The ensemble spread, on the other hand, is largely due to redistribution, with pronounced disagreement among the AOGCMs.

Description: Food web research provides essential insights into ecosystem functioning, but practical applications in ecosystem-based management are hampered by a current lack of knowledge synthesis. To address this gap, we provide the first systematic review of ecological studies applying stable isotope analysis, a pivotal method in food web research, in the heavily anthropogenically impacted Baltic Sea macro-region. We identified a thriving research field, with 164 publications advancing a broad range of fundamental and applied research topics, but also found structural shortcomings limiting ecosystem-level understanding. We argue that enhanced collaboration and integration, including the systematic submission of Baltic Sea primary datasets to stable isotope databases, would help to overcome many of the current shortcomings, unify the scattered knowledge base, and promote future food web research and science-based resource management. The effort undertaken here demonstrates the value of macro-regional synthesis, in enhancing access to existing data and supporting strategic planning of research agendas.

Description: Understanding the drivers behind fluctuations in fish populations remains a key objective in fishery science. Our predictive capacity to explain these fluctuations is still relatively low, due to the amalgam of interacting bottom-up and top-down factors, which vary across time and space among and within populations. Gaining a mechanistic understanding of these recruitment drivers requires a holistic approach, combining field, experimental and modelling efforts. Here, we use the Western Baltic Spring-Spawning (WBSS) herring (Clupea harengus) to exemplify the power of this holistic approach and the high complexity of the recruitment drivers (and their interactions). Since the early 2000s, low recruitment levels have promoted intense research on this stock. Our literature synthesis suggests that the major drivers are habitat compression of the spawning beds (due to eutrophication and coastal modification mainly) and warming, which indirectly leads to changes in spawning phenology, prey abundance and predation pressure. Other factors include increased intensity of extreme climate events and new predators in the system. Four main knowledge gaps were identified related to life-cycle migration and habitat use, population structure and demographics, life-stage specific impact of multi-stressors, and predator–prey interactions. Specific research topics within these areas are proposed, as well as the priority to support a sustainable management of the stock. Given that the Baltic Sea is severely impacted by warming, eutrophication and altered precipitation, WBSS herring could be a harbinger of potential effects of changing environmental drivers to the recruitment of small pelagic fishes in other coastal areas in the world.

Description: Hydroacoustic surveys at the accretionary wedge southwest of Taiwan reveal a confined active hydrocarbon seepage area of ~ 49,000 m 2 in ~ 1350 m water depth on the northern crest of the Four-Way Closure Ridge, which we call Yam Seep. In this study, multibeam and side-scan sonar data acquired during surveys with an autonomous underwater vehicle during an expedition with R/V Ocean Researcher I in 2017 showed that the area is characterized by rough topography and high seafloor backscatter. Seafloor observations with a video sled and sediment sampling with gravity corers and the MeBo seafloor drill rig during an expedition with R/V SONNE in 2018 revealed that the area is almost entirely covered by intensely fractured methane-derived carbonates, which indicate that seepage has been ongoing for thousands of years. Hydroacoustic anomalies (‘flares’) in the water column indicated the presence of several gas bubble emission sites mostly at the center and eastern flank of the area in 2019. Drilling through massive carbonates in the northwestern part of Yam Seep induced free gas escape from a depth of ~ 5.1 m. This suggests the presence of gas hydrates in the subsurface as the seep area is located well within the gas hydrate stability zone. The inter-disciplinary investigations of the Yam Seep demonstrate that upward migration of light hydrocarbons and seafloor discharge has a considerable influence on the seabed properties.

Description: Tropical peat swamps are essential ecosystems, which provide numerous services, and also serve as a rich source of dissolved organic carbon (DOC), hydrogen ions and trace elements to peat draining rivers. However, not much is known about trace element export from tropical peat swamps. We investigated trace element dynamics in rivers and estuaries draining tropical peat swamps on Borneo, and examined the influence of estuarine processes as well as dissolved organic carbon (DOC) on the distribution and concentration of trace elements. Our results indicate acidic conditions (pH = 3.3) and high DOC concentration (3500 µmol L −1 ) at salinities〈1. We observed an initial release of trace elements at low salinity (0.05〈S〈 0.5), followed by scavenging to particles at intermediate salinities (0.5〈S〈10) due to an increasing ionic strength and pH. Peak concentrations (µmol kg −1 ) of Al (24.9), Si (96.2), Mn (4.9), Cu (0.035) and Ni (0.047) were observed during the dry season (July), and Fe concentrations (43.2) were highest during the wet season (December). We used the NICA-Donnan model to investigate the combined impact of DOC and pH on the formation of solid iron hydroxide (Fe(OH) 3 (s)). The Maludam river was predicted to be supersaturated for Fe hydroxides and the results affirmed our model prediction. The output showed Fe and Cu had a strong affinity for DOC and to a lesser extent Al and Ni in the conditions prevailing at the study sites. Statistical analyses also indicated strong correlation between Cu and Ni (r 2 = 0.97, 0.94 and 0.82) in Maludam, Sebuyau and Belait rivers and estuaries, respectively. The results obtained in this study are comparable to values published for southeast Asia and other continents for pristine peat draining rivers.

Description: The abyssal plains are vast areas without large scale relief that occupy much of the ocean floor. Although long considered relatively featureless, they are now known to display substantial biological heterogeneity across different spatial scales. Ecological research in these regions benefits increasingly from non-destructive visual sampling of epifaunal organisms with imaging technology. We analysed images from ultra-high-definition towed camera transects at depths of around 3500 m across three stations (100–130 km apart) in the Bering Sea, to ask whether the density and distribution of visible epifauna indicated any substantial heterogeneity. We identified 71 different megafaunal taxa, of which 24 occurred at only one station. Measurements of the two most abundant faunal elements, the holothurian Elpidia minutissima and two xenophyophores morphotypes (the more common identifiable as Syringammina limosa), indicated significant differences in local densities and patchy aggregations that were strikingly dissimilar among stations. One station was dominated by xenophyophores, one was relatively depauperate in both target taxa as well as other identified megafauna, and the third station was dominated by Elpidia. This is an unexpected level of variation within comparable transects in a well-mixed oceanic basin, reinforcing the emerging view that abyssal habitats encompass biological heterogeneity at similar spatial scales to terrestrial continental realms.

Description: Limiting global warming to well below 2°C and pursuing efforts to limit it to 1.5°C, as agreed in the 2015 Paris Agreement, requires global carbon neutrality by mid-century at the latest. The corresponding carbon budget is decreasing steadily and significantly. To phase out carbon emissions in line with the specified temperature target, countries are formulating their mitigation efforts in their long-term low greenhouse gas emission development strategies (LT-LEDS). However, there are no standardized specifications for preparing these strategies, which is why the reports published to date differ widely in terms of structure and scope. To consider the multiple facets of reaching net-zero from a systemic perspective as comprehensively as possible, the authors propose the Net-Zero-2050 System: A novel, transferrable systems approach that supports the development of national endeavors toward carbon neutrality. The Net-Zero-2050 System is defined by three interconnected components: The Carbon-Emission-Based System, the surrounding Framing System and a set of system boundaries. For both systems levels, IPCC approaches were used as a basis and were then adjusted and supplemented by Net-Zero-2050. We suggest applying the Net-Zero-2050 System—beyond the project environment—in carbon emission based contexts at different levels. Especially at the national level, this would improve the comparability of the different national strategies to achieve carbon neutrality.

Description: Interactions between volcanoes and glaciers provide insight to the evolution of a volcanic edifice and may be an indicator for renewed volcanic activity. At Mount St. Helens, Crater Glacier, which has formed in the volcanic crater after the eruption in 1980, is one of the world’s last expanding glaciers and provides a unique opportunity to characterize the evolution of a glacier expanding onto an area of significant thermal flux. We combine photographic documentation and glaciovolcanic cave surveys with remote sensing data from Google Earth, UAS, and LiDAR to analyze the present state of Crater Glacier and reconstruct its development since the emplacement of the 2004–2008 lava dome. Our results show that snow accumulation has caused Crater Glacier to grow from 2009 to 2019 by approximately 13.8 × 106 m3, during which time the glacier toe advanced by several hundred meters. The glacier-dome interface shift toward higher elevations against the 2004–2008 lava dome and subsequent encroachment onto thermally active areas led to glacier modification via extensive subglacial cave system formation. Analysis of subglacial tephra layers revealed the existence of juvenile material from the 2004–2008 eruption cycle, providing insights about glacier subsidence of ~ 40 m since 2004/2005 in spite of net growth. Although the lava dome is cooling, the glacier-dome interface seems to have become increasingly stable in the past few years. Our results suggest that glacier development in the accumulation area adjacent to the dome is now being affected by the thermal characteristics of the lava dome itself, making monitoring internal glacier development via tracking glaciovolcanic cave expansion a potentially important volcano monitoring tool. Zusammenfassung Die Interaktionen von Vulkanen und Gletschern tragen häufig zum Verständnis über die Entwicklung eines vulkanischen Systems bei und können als Indikator für wiederkehrende vulkanische Aktivität dienen. Crater Glacier, der nach der Eruption 1980 im Krater des Mount St. Helens entstanden ist, ist einer der letzten wachsenden Gletscher weltweit und bietet somit eine einmalige Chance, die Entwicklung eines Gletschers in Verbindung mit erheblichen Wärmeflüssen zu charakterisieren. Neben einer fotografischen Dokumentation des Gletschers machen wir uns die Kartierung vulkanischer Gletscherhöhlen zu Nutze. Diese kombinieren wir mit Fernerkundungsdaten von Google Earth sowie Drohnen- und LiDAR-Daten, um den aktuellen Zustand des Gletschers zu charakterisieren und seine Entwicklung seit dem letzten Lavadomwachstum zwischen 2004 und 2008 zu rekonstruieren. Unsere Ergebnisse zeigen, dass die ausreichende Akkumulation von Schnee zum Wachstum des Gletschers mit einem Massenzuwachs von ca. 13,8 x 106 m3 zwischen 2009 und 2019 geführt hat. Neben dem Voranschreiten der Gletscherzunge um mehrere hundert Meter hat sich das Wachstum ebenfalls rund um den neuen Lavadom bemerkbar gemacht. Durch die Verschiebung der Kontaktzone von Gletscher und Lavadom hin zu höheren Bereichen des Doms und der damit verbundenen Interaktion zwischen Gletscher und geothermaler Aktivität ist es zu einer deutlichen Veränderung des Gletschers durch die Ausbildung subglazialer Höhlensysteme gekommen. Analysen von im Gletscher eingebetteten Tephraschichten, die vermutlich der letzten Aktivität zwischen 2004 und 2008 zuzuordnen sind, deuten trotz des allgemeinen Wachstums auf eine Setzung des Gletschers um etwa 40 m seit 2004/05 hin. Obwohl der Lavadom an Hitze verliert, scheint die Kontaktzone von Gletscher und Dom in den letzten Jahren zunehmend konstant geworden zu sein. Unsere Ergebnisse deuten darauf hin, dass der Gletscher in diesem Bereich derzeit vor allem durch die thermalen Eigenschaften des Lavadoms beeinflusst wird. Dadurch kommt dem Monitoring interner Gletscherstrukturen mittels Beobachtung vulkanischer Gletscherhöhlen eine potenziell wichtige Bedeutung bei der Vulkanüberwachung zu.

Description: Ocean data synthesis products for specific biogeochemical essential ocean variables have the potential to facilitate today’s biogeochemical ocean data usage and comply with the Findable Accessible Interoperable and Reusable (FAIR) data principles. The products constitute key outputs from the Global Ocean Observation System, laying the observational foundation for information and services regarding climate and environmental status of the ocean. Using the Framework of Ocean Observing (FOO) readiness level concept, we present an evaluation framework for biogeochemical data synthesis products, which enables a systematic assessment of each product’s maturity. A new criteria catalog provides the foundation for assigning scores to the nine FOO readiness levels. As an example, we apply the assessment to four existing biogeochemical essential ocean variables data products. In descending readiness level order these are: The Surface Ocean CO2 Atlas (SOCAT); the Global Ocean Data Analysis Project (GLODAP); the MarinE MethanE and NiTrous Oxide (MEMENTO) data product and the Global Ocean Oxygen Database and ATlas (GO2DAT). Recognizing that the importance of adequate and comprehensive data from the essential ocean variables will grow, we recommend using this assessment framework to guide the biogeochemical data synthesis activities in their development. Moreover, we envision an overarching cross-platform FAIR biogeochemical data management system that sustainably supports the products individually and creates an integrated biogeochemical essential ocean variables data synthesis product; in short a system that provides truly comparable and FAIR data of the entire biogeochemical essential ocean variables spectrum.

Description: Military field exercises are characterised by high volumes of exercise and prolonged periods of load carriage. Exercise can decrease circulating serum calcium and increase parathyroid hormone and bone resorption. These disturbances to calcium and bone metabolism can be attenuated with calcium supplementation immediately before exercise. This randomised crossover trial will investigate the effect of calcium supplementation on calcium and bone metabolism, and bone mineral balance, during load carriage exercise in women. Methods Thirty women (eumenorrheic or using the combined oral contraceptive pill, intrauterine system, or intrauterine device) will complete two experimental testing sessions either with, or without, a calcium supplement (1000 mg). Each experimental testing session will involve one 120 min session of load carriage exercise carrying 20 kg. Venous blood samples will be taken and analysed for biochemical markers of bone resorption and formation, calcium metabolism, and endocrine function. Urine will be collected pre- and post-load carriage to measure calcium isotopes for the calculation of bone calcium balance. Discussion The results from this study will help identify whether supplementing women with calcium during load carriage is protective of bone and calcium homeostasis.

Description: Coralline algae play important ecological roles throughout the photic zone of the world’s oceans. Recent studies have shown that attached-living coralline algae can contain records of past climate variability. So far, algal-based paleo-reconstructions are mainly available from mid- to high-latitudes, while in low latitude and temperate regions only few examples exist. Here, we investigate samples from the attached-living encrusting coralline algal species Neogoniolithon hauckii (Rothpletz) R.A Townsend & Huisman [= Neogoniolithon mamillosum (Hauck) Setchell & L.R. Mason, nom illeg.] from a temperate site in the Mediterranean Sea to assess its potential as an environmental recorder. The specimens were collected at different water depths (20 and 40 m) in the Columbretes Islands (Spain). Sclerochronological analysis of sectioned samples revealed seasonal growth patterns. Mg/Ca, Li/Ca, and Ba/Ca ratios were measured in the algal skeletons using laser ablation inductively coupled mass spectrometry (LA-ICP-MS) in ultra-high resolution. We report a mean vertical extension rate of 1.1 to 1.2 mm/year (based on analysis of Mg/Ca cycles in 40 m and 20 m samples), representing the first growth rate measurement for this species. In addition, subannual banding patterns were mapped, measured, and could be linked to high frequency variability in laser-analyzed Mg/Ca ratios. Elemental ratios analyzed in Neogoniolithon hauckii were compared to in situ water temperatures measured at the water depth of sample collection. Our results show significant positive relationships between algal Mg/Ca (R=0.55) as well as Li/Ca ratios (R=0.46) and in situ measured temperature data (40 m specimen). Ba/Ca ratios show no significant correlation to temperature and may be influenced by other factors. These data suggest potential of this species for climate reconstructions in warm-temperate regions as Neogoniolithon hauckii is not only widely distributed in the Mediterranean, but also one of the few species that may be used as a temperature archive for mesophotic coralligenous assemblages that are strongly affected by the recent anthropogenic temperature rise. Further calibration studies are needed to test the element-temperature relationships on samples with longer growth records and in different settings and water depths.

Description: Global warming causes profound environmental shifts in the Arctic Ocean, altering the composition and structure of communities. In the Fram Strait, a transitional zone between the North-Atlantic and Arctic Ocean, climate change effects are particularly pronounced and accelerated due to an increased inflow of warm Atlantic water. Gelatinous zooplankton are known as key predators, consuming a great variety of prey and playing an important role in marine ecosystems. Insufficient knowledge of how gelatinous zooplankton are affected by environmental change has resulted in a notable gap in the understanding of the future state of Arctic ecosystems. We analyzed the diversity and abundance of gelatinous zooplankton down to 2600 m depth and established the first regional baseline dataset using optical observations obtained by the towed underwater camera system PELAGIOS (Pelagic In situ Observation System). Our data estimate the abundance of 20 taxa of gelatinous zooplankton. The most abundant taxa belong to the family of Rhopalonematidae, mainly consisting of Aglantha digitale and Sminthea arctica, and the suborder Physonectae. Using the observational data, we employed a joint species distribution modelling approach to better understand their distributional patterns. Variance partitioning over the explanatory variables showed that depth and temperature explained a substantial amount of variation for most of the taxa, suggesting that these parameters drive diversity and distribution. Spatial distribution modelling revealed that the highest abundance and diversity of jellyfish are expected in the marginal sea-ice zones. By coupling the model with climate scenarios of environmental changes, we were able to project potential changes in the spatial distribution and composition of gelatinous communities from 2020 to 2050 (during the summer season). The near-future projections confirmed that with further temperature increases, gelatinous zooplankton communities in the Fram Strait would become less diverse but more abundant. Among taxa of the Rhopalonematidae family, the abundance of Aglantha digitale in the entire water column would increase by 2%, while a loss of up to 60% is to be expected for Sminthea arctica by 2050. The combination of in situ observations and species distribution modelling shows promise as a tool for predicting gelatinous zooplankton community shifts in a changing ocean.

Description: Since the discovery of the first oncaeid copepod described by Philippi in 1843 as Oncaea venusta, great progress has been achieved regarding the morphological/descriptive taxonomy of the microcopepod family Oncaeidae, occurring in all great oceans and all depth layers of the ocean. The species diversity of this family is still underestimated and the ecological role of oncaeids within the marine ecosystem is not yet well understood, but the life strategy appears to be fundamentally different from most other pelagic microcopepod families. The present paper aims at a comprehensive review of the current state of knowledge of this microcopepod family, including taxonomic and phylogenetic issues, questions of species identification, specific morphological and molecular genetic characteristics, information on regional and vertical distribution and abundance, motion behaviour, feeding and food relationships, reproduction aspects, biomass and elemental composition, respiration and metabolic rates. Relevant open questions are highlighted, and examples are given of shortcomings and high uncertainties in results of current attempts to include oncaeid copepods in various aspects of global marine ecosystem studies. It is concluded that continued support of taxonomic research is required for Oncaeidae and other small copepod species, based on an integrated approach of morphological and molecular genetic methods and user-friendly regional identification keys, to allow an adequate consideration of oncaeids in advanced ecological studies and to achieve a better understanding of the ecological role of this abundant microcopepod family in marine ecosystems.

Description: Sponges harbor diverse, specific, and stable microbial communities, but at the same time, they efficiently feed on microbes from the surrounding water column. This filter-feeding lifestyle poses the need to distinguish between three categories of bacteria: food to digest, symbionts to incorporate, and pathogens to eliminate. How sponges discriminate between these categories is still largely unknown. Phagocytosis is conceivable as the cellular mechanism taking part in such discrimination, but experimental evidence is missing. We developed a quantitative in-vivo phagocytosis assay using an emerging experimental model, the sponge Halichondria panicea. We incubated whole sponge individuals with different particles, recovered the sponge (host) cells, and tracked the incorporation of these particles into the sponge cells. Fluorescence-activated cell sorting (FACS) and fluorescent microscopy were used to quantify and verify phagocytic activity, defined here as the population of sponge cells with incorporated particles. Sponges were incubated with a green microalgae to test if particle concentration in the seawater affects the percentage of phagocytic activity, and to determine the timing where the maximum of phagocytic cells are captured in a pulse-chase experiment. Lastly, we investigated the application of our phagocytic assay with other particle types (i.e., fluorescently-labeled bacteria and fluorescent beads). The percentage of sponge cells that had incorporated algae, bacteria, and beads ranged between 5 to 24 %. These phagocytic sponge cells exhibited different morphologies and sizes depending on the type of particle presented to the sponge. Particle incorporation into sponge cells was positively related to algal concentration in the seawater, suggesting that sponge cells adjust their phagocytic activity depending on the number of particles they encounter. Our results further revealed that sponge phagocytosis initiates within minutes after exposure to the particles. Fluorescent and TEM microscopy rectified algal internalization and potential digestion in sponge cells. To our knowledge, this is the first quantitative in-vivo phagocytosis assay established in sponges that could be used to further explore phagocytosis as a cellular mechanism for sponges to differentiate between different microorganisms.

Description: Temperate fisheries grounds are exposed to compound effects of jellyfish proliferations and fishing pressure, which affect local fisheries, cause economic losses, and threaten seafood supply. Here, we quantify the interlink between climate variability and jellyfish blooms and their impact on the Japanese anchovy (Engraulis japonicus), in the Korean coastal waters. We used a bioclimate dataset (2010–2019) that includes quantitative information of two major bloom-former species, Aurelia coerulea and Nemopilema nomurai, in the Korean Peninsula. We show that climate phenomena governing East Asia regions explain circa half of jellyfish variability. In turn, jellyfish blooms have a significant negative effect on anchovy interannual changes (r = -0.47, P 〈 0.01), which varies along with the bloom magnitude. Our results indicate that the intensity of jellyfish blooms, more than their duration, has a predominant effect on anchovy and coastal fisheries production. We also suggest the possibility of using climate signals for assessing and eventually predicting, interannual abundance changes of jellyfish in the Korean Peninsula. These results stress the challenge posed by jellyfish blooms to the provisioning of ecosystem services via their influence on marine harvested fish and further highlight the need for their integration into ecosystem-based management.

Description: Removal of atmospheric carbon dioxide is being considered a suitable option for reducing the recent global rise in atmospheric temperature. The impact of the removal on some climate parameters—near-surface air temperature (TAS), maximum near-surface air temperature (TASMAX), minimum near-surface air temperature (TASMIN) and surface temperature (TS) over West Africa was assessed in this paper. We used CNRM-ESM1-C1 model simulation output consisting of 1%yr−1 CO2 removal from the atmosphere which was compared with CRU observational dataset. Four climatological periods 1990–2019 (reference period), 2040–2069, 2070–2099 and 2100–2129 were considered, and hence the impacts levels in each of the two West African regions, Sahel and Guinea, were estimated in each period with respect to the reference period. The comparison with CRU demonstrated that CNRM-ESM1-C1 model captured temperature variations within major locations in Mauritania, Mali, Niger, Burkina Faso and Senegal with an indication of an underestimation of temperature at locations above 18° N. The value of each parameter was projected to decrease progressively the periods and much impacts were also projected in the last period for the two regions. Time of retreat to 2 °C reduction target is projected a decade before the year 2100 and will occur earlier with greater impact in the Guinea region than in Sahel region. The root mean square deviation of each ensemble member was found at RMSD 〈 0.5 with respect to the model ensemble mean per parameter, although RMSD 〉 0.5 was found with GFDL-ESM4 model for TAS and TS.

Description: The conventional view of spawning in iteroparous bony fish, i.e., the “reproductive drain hypothesis,” is based on the observation that somatic growth (in length) slows down noticeably at approximately the time fish attain maturity, and hence the assumption is made that investment in gonadal development slows down growth. However, when this is translated as growth in weight, the weight at first maturity (or puberty) is usually smaller than the weight at which growth rate is highest, i.e., weight growth accelerates after first maturity. We solve this conundrum, with some emphasis on female cod (Gadus morhua), by proposing the hypothesis that the substantial loss of body mass experienced by fish as a result of spawning is quickly compensated for by increased somatic growth after the spawning period, notably because of the increase in food conversion efficiency resulting from a sudden loss of body weight, which necessarily leads to a large increase in relative oxygen supply via the gills. This is consistent with the argument developed elsewhere that declining relative oxygen supply by the gills, whose surface area cannot keep up with increasing body weight, is the reason for growth rate declining with weight in adult fish.

Description: This paper presents numerous new data on the geochemical composition of olivine, clinopyroxene, and leucite phenocrysts, as well as spinel inclusions in olivine and quench glass from lamproites of Gaussberg volcano (East Antarctica). Most of the olivine phenocrysts in the Gaussberg lamproites are high Mg varieties (Fo89–91) with elevated Ni contents (up to 4900 ppm) and high Ni/Co ratios. According to data of about 320 clinopyroxene analyses, two groups of diopsidic phenocrysts have been established. Group I consists mainly of high-Mg varieties (Mg#〉80), while group II clinopyroxenes are less magnesian (Mg# 52–80). The main difference between the clinopyroxenes of the two groups is the elevated contents of Al2O3, FeO and reduced TiO2, Cr2O3, and NiO in the compositions of group II compared to group I, as well as different contents of trace elements, which may reflect their crystallization from different types of primary melts. According to the study of ~550 grains of leucite phenocrysts in the Gaussberg lamproites, it was shown that they correspond to the ideal stoichiometry of leucite K[AlSi2O6] and are enriched in Na2O (0.05–0.35 wt %), but depleted in K2O (19.9–20.9 wt %) compared to leucites from lamproites of other provinces. The BaO content reaches 0.3 wt %, SrO –0.04 wt %. The iron content in most leucite phenocrysts varies within 0.7–1.2 wt % Fe2O3, but some grains have the low Fe2O3 contents (〈0.5 wt %). In leucite microlites of the groundmass and rims of phenocrysts, the Fe2O3 content can reach 2.4 wt %, which may indicate more oxidized conditions at lava eruption. Based on the study of natural samples, existing experimental data and numerical models, the order and conditions of crystallization of the Gaussberg lamproites were obtained. Crystallization proceeded in the following order: chromian spinel → chromian spinel + olivine → olivine + leucite (± chromian spinel) → olivine + leucite + clinopyroxene (± chromian spinel). The near-liquidus assemblage represented by high-Mg olivine phenocrysts with inclusions of Cr-spinel was formed in the temperature range from 1180 to 1250°C. Further crystallization of the melt with the formation of an association of olivine+leucite+clinopyroxene phenocrysts could occur at pressures below 2 GPa and temperatures of 1070–1180°C, corresponding to the presence of water in the magmatic system. Estimates of the redox conditions of crystallization of lamproites obtained using different oxybarometers vary in a wide range from QFM-0.5 to QFM+2.3. The elevated Ni contents in liquidus olivines of Gaussberg indicate the high nickel contents in the source. It is shown that the formation of ultra-alkaline magmas in the Gaussberg volcano area is likely related to melting of the continental lithosphere, which was heterogeneous and included both the peridotite mantle and hydrous pyroxenite fragments.

Description: A.G. Bain (1797–1864) was probably the first to describe the deposits of the Permo-Carboniferous glaciation of South Africa in 1844, but still attributed their formation to a volcanic origin. It was not until P.C. Sutherland (1822–1908) in 1868 and 1870 that the series was recognised as a glacial formation. J. E. Dunn (1844–1937) named this deposit the Dwyka Series or Dwyka Conglomerate after the Dwyka River near Prince Albert in South Africa in 1886. This series contains scratched boulders and varved sediments, and the basement is characterised by rounded boulders and striated surfaces as evidence of glaciation.

Description: The North Pacific Subtropical Countercurrent area (STCC) is high in mesoscale eddy activities. According to the rotation direction of the eddy flow field and the sign of temperature anomaly within the eddy, they can be divided into four categories: cyclonic cold-core eddy (CCE), anticyclonic warm-core eddy (AWE), cyclonic warm-core eddy (CWE) and anticyclonic cold-core eddy (ACE). CCE and AWE are called normal eddies, and CWE and ACE are named abnormal eddies. Based on the OFES data and vector geometry automatic detection method, we find that at the sea surface, the maximum monthly number of the CCE, AWE, CWE, and ACE occurs in December (765.70 ± 52.05), January (688.20 ± 82.53), August (373.40 ± 43.09) and August (533.00 ± 56.92), respectively. The number of normal eddies is more in winter and spring, and less in summer and autumn, while abnormal eddies have the opposite distribution. The maximum rotation velocity of the four types of eddies appears in June (11.71 ± 0.75 cm/s), June (12.24 ± 0.86 cm/s), May (10.63 ± 0.99 cm/s) and June (9.97 ± 0.91 cm/s), which is fast in winter and spring. The moving speed of the four types of eddies is almost similar (about 10 ~ 11 cm/s). The amplitude of normal and abnormal eddies is both high in summer and autumn, and low in winter and spring, with larger amplitudes in normal than abnormal eddies. The eccentricity (defined as the eccentricity of the ellipse obtained by fitting the eddy boundary) of the four types of eddies is also close to each other, and their variation ranges from 0.7 to 0.8, with no apparent seasonal variation. The vertical penetration depth, which has no significant seasonal difference, is 675.13 ± 67.50 m in cyclonic eddies (CCE and CWE), which is deeper than that 622.32 ± 81.85 m in anticyclonic eddies (ACE and AWE). In addition, increasing the defined temperature threshold for abnormal eddies can significantly reduce their numbers but does not change their seasonal variation trend.

Description: In this study, we present a new 87 Sr/ 86 Sr isoscape map of Central and NE Germany. This area is characterized by an alternation of sedimentary basins and mountainous regions with a very variable lithology. Since lithology and rock age have a major impact on the isotopic composition of biologically available strontium, Central and NE Germany should reveal highly variable 87 Sr/ 86 Sr ratios. From lithological characteristics, particularly high ratios are expected in the mountainous regions of the Erzgebirge/Fichtelgebirge and the Harz Mountains. In contrast to these predictions, published 87 Sr/ 86 Sr isoscape maps of Central and NE Germany record rather uniform and low 87 Sr/ 86 Sr ratios. From this observation, we suspected that existing isoscape maps might be computed from an insufficient database, with mountainous regions being underrepresented. Our goal was to gather 87 Sr/ 86 Sr baselines for each major lithology of Central and NE Germany and to produce an accurate isoscape map of Central and NE Germany. In the first step, we evaluated the suitability of stream water and groundwater as a proxy for biologically available strontium. In a selected watershed, we present mixing relationships and a stream network model. We show that groundwater is prone to very local geologic and anthropogenic influences and should thus be avoided. Instead, we focussed our further sampling on stream water. Altogether, we used 119 new measurements of groundwater and stream water and a set of 23 auxiliary variables as a database for our new isoscape map of Central and NE Germany. Due to a sampling strategy that focussed on covering each major lithology, our measurements and the final isoscape map show a clear contrast between sedimentary basins and mountainous regions. For regions that have been sufficiently sampled, a direct comparison of the isoscape map with published and new data shows good agreement. Although Central and NE Germany were part of published isoscape maps, our new map is the first that predicts 87 Sr/ 86 Sr ratios in mountainous regions with high accuracy.

Description: Dissolved silicon is an essential nutrient for the growth of various ocean organisms that need it to build their skeletons. Most of the dissolved silicon that sustains these organisms comes from the breakdown of silicon-containing rocks on land. In recent decades, human activities have greatly disturbed the transport of silicon from land to ocean. For example, dams built to generate electricity can interrupt the transport of dissolved silicon and starve downstream areas. Fertilizers and other human pollution add large amounts of non-silicon nutrients to rivers, lakes, and reservoirs, which can stimulate organisms to grow and use up silicon before it reaches the ocean. In addition, consequences of climate change can also impact the silicon cycle. In this article, we explain how human activities have disturbed the silicon cycle and discuss how climate change may affect it in the future.

Description: This Open Access book on Ocean Governance examines sustainability challenges facing our oceans today. The book is organized into three sections: knowledge systems, policy foundations and thematic analyses. The knowledge produced in the book was catalyzed by the scientific outcomes within the European-funded Cooperation in Science and Technology (COST) network “Ocean Governance for Sustainability – Challenges, Options and the Role of Science”. This network brings together scientists, policy-makers and civil society representatives from 28 nation states to cooperate on ocean governance research. This book offers a compilation of new research material including focused case studies, broad policy syntheses and reflective chapters on the history and current status of knowledge production systems on ocean governance. New research material is presented, although some chapters draw on secondary sources. The book starts with synthetic review chapters from the editors, outlining past and present knowledge systems, addressing how and why ocean governance for sustainability is where it currently stands with critical reflections on existing narratives, path dependencies and colonialist histories. This is followed by chapters addressing, synthesizing and analyzing different legal and policy frameworks for ocean governance both regionally and internationally. At the core of the book are the thematic analyses, which provide focused case studies with detailed contextual information in support of different ocean governance challenges and sustainability pathways around the world. The book concludes with a chapter explicitly targeting students, researchers and policy-makers with key take-away messages compiled by the editors.

Description: Over one hundred years of vigorous progress in tropical cyclone (TC) research, the genesis of the cyclone (hereafter, tropical cyclogenesis) is remarkable as a doubtful subject. Furthermore, predicting tropical cyclogenesis, particularly in the lesser latitude, remains a significant challenge. Therefore, understanding the complex interactions in developing tropical cyclogenesis over the region is vital to improving tropical cyclogenesis forecasting. Hence, the Indonesia Maritime Continent is a tropical cyclone-free region due to decreasing the Coriolis effect. However, Seroja TC hit Flores (8.6° S, 120° E), east Nusa Tenggara, Indonesia, on 4 April 2021, and was recorded as the first TC that occurred over the mainland, which brought a catastrophic disaster in the region. This study investigated the tropical cyclogenesis of Seroja by using observational and numerical studies. The results indicate that a marine heatwave and double vortices were favorable conditions that produced preconditions for developing tropical cyclogenesis over the Maluku Sea. Thus, tropical cyclogenesis is formed by the breakdown of the intertropical convergence zone (ITCZ) associated with synoptic-scale wave train driven under the interaction of the Madden Julian oscillation (MJO) and equatorial Rossby waves. Moreover, our finding suggested that an extensive background cyclonic vorticity under the cold pool mechanisms is responsible for maintaining tropical cyclogenesis into a persistent Seroja TC.

Description: In highly fragmented and relatively stable cold-seep ecosystems, species are expected to exhibit high migration rates and long-distance dispersal of long-lived pelagic larvae to maintain genetic integrity over their range. Accordingly, several species inhabiting cold seeps are widely distributed across the whole Atlantic Ocean, with low genetic divergence between metapopulations on both sides of the Atlantic Equatorial Belt (AEB, i.e. Barbados and African/European margins). Two hypotheses may explain such patterns: (i) the occurrence of present-day gene flow or (ii) incomplete lineage sorting due to large population sizes and low mutation rates. Here, we evaluated the first hypothesis using the cold seep mussels Gigantidas childressi, G. mauritanicus, Bathymodiolus heckerae and B. boomerang. We combined COI barcoding of 763 individuals with VIKING20X larval dispersal modelling at a large spatial scale not previously investigated. Population genetics supported the parallel evolution of Gigantidas and Bathymodiolus genera in the Atlantic Ocean and the occurrence of a 1-3 Million-year-old vicariance effect that isolated populations across the Caribbean Sea. Both population genetics and larval dispersal modelling suggested that contemporary gene flow and larval exchanges are possible across the AEB and the Caribbean Sea, although probably rare. When occurring, larval flow was eastward (AEB - only for B. boomerang) or northward (Caribbean Sea - only for G. mauritanicus). Caution is nevertheless required since we focused on only one mitochondrial gene, which may underestimate gene flow if a genetic barrier exists. Non-negligible genetic differentiation occurred between Barbados and African populations, so we could not discount the incomplete lineage sorting hypothesis. Larval dispersal modelling simulations supported the genetic findings along the American coast with high amounts of larval flow between the Gulf of Mexico (GoM) and the US Atlantic Margin, although the Blake Ridge population of B. heckerae appeared genetically differentiated. Overall, our results suggest that additional studies using nuclear genetic markers and population genomics approaches are needed to clarify the evolutionary history of the Atlantic bathymodioline mussels and to distinguish between ongoing and past processes.

Description: The Clarion Clipperton Fracture Zone (CCZ) is an abyssal region in the north-east Pacific that is currently being explored for metal-rich polymetallic nodules, but also harbors a highly diverse megabenthic community. This community is influenced by multiple environmental gradients including bathymetric structures as well as differences in habitat and food availability. This study focuses on the benthic megafauna investigated in an exploration area positioned in the very east of the CCZ, which exhibits the lowest water depths (mean: 4200 m) and the highest flux of particulate organic carbon (POC) of the CCZ. Case studies using seafloor images for the detection of megafauna have revealed differences between seamounts and abyssal hills compared to nodule fields, as well as differences in the community composition between areas with and without nodule coverage and rock outcrop. Extrapolations suggest a richness of more than 300 morphotypes in the study area, including multiple invertebrate groups such as corals, sponges, echinoderms, and crustaceans as well as fish. Focusing on sampled specimens, diversities of Ophiuroidea, Porifera, and Bryozoa are high and more species are likely to be discovered in the study area. This also applies for the taxon Ophiuroidea, which is among the taxa investigated in the greatest detail so far. In the context of deep-sea mining, megafauna has been in the focus of a variety of environmental studies including baseline analyses, disturbance experiments, and/or testing of mining components or systems. These studies identify and address key factors responsible for the observed natural and impacted distribution patterns and thereby help to constrain expected anthropogenic impacts to the deep-sea environment in the context of deep-sea mining. Specifically in the area of focus of this study, 10 years of megafauna analyses have shown that the biodiversity in the selected preservation reference zone (PRZ) is not as similar to that of the impact reference zone (IRZ) as originally hypothesized based mainly on geological parameters. We suggest that recent area-wide habitat classifications and faunal mapping exercises (e.g., Uhlenkott et al. 2020, 2022) are used to designate a new PRZ that is more similar to the IRZ to meet its purpose, but that the current PRZ is maintained for scientific and conservation purposes.

Description: Understanding how the salt marsh vegetation will evolve under future climate conditions is essential for predicting the role of marsh ecosystem services in a warmer climate with higher CO 2 -concentrations. In a mesocosm experiment in the northern Wadden Sea, the impact of increased temperature (+ 3 °C) and CO 2 (800 ppm) on salt marsh vegetation was investigated, assessing biomass production in the pioneer zone and low marsh. The pioneer zone, which was dominated by Spartina anglica and exposed to natural tidal inundations , demonstrated a differentiated response between belowground and aboveground biomass. Aboveground biomass increased in response to enhanced CO 2 availability, and belowground biomass increased in response to raised temperatures. Other plant species accounted for less than 18% of the aboveground biomass, and their biomass was suppressed under high CO 2 availability. Increased biomass by Spartina anglica may improve resilience toward sea level rise. Hence, the pioneer zone is expected to maintain its coastal protection and blue carbon storage capacity under future climate conditions. The low marsh, which was dominated by Elymus athericus , was exposed to higher than usual tidal inundations and resembled a scenario with increased sea level. The low marsh showed no response in biomass to increased CO 2 or temperature, which may be due to the increased flooding. The positive response of Spartina anglica (C 4 plant) and the lack of response in Elymus athericus (C 3 plant) counter the notion that C 3 plants are more productive under future climate conditions and demonstrate that C 4 plants can also thrive in future salt marshes.

Description: Polymeric carbohydrates are abundant and their recycling by microbes is a key process of the ocean carbon cycle. A deeper analysis of carbohydrate-active enzymes (CAZymes) can offer a window into the mechanisms of microbial communities to degrade carbohydrates in the ocean. In this study, metagenomic genes encoding microbial CAZymes and sugar transporter systems were predicted to assess the microbial glycan niches and functional potentials of glycan utilization in the inner shelf of the Pearl River Estuary (PRE). The CAZymes gene compositions were significantly different between in free-living (0.2–3 μm, FL) and particle-associated (〉3 μm, PA) bacteria of the water column and between water and surface sediments, reflecting glycan niche separation on size fraction and selective degradation in depth. Proteobacteria and Bacteroidota had the highest abundance and glycan niche width of CAZymes genes, respectively. At the genus level, Alteromonas (Gammaproteobacteria) exhibited the greatest abundance and glycan niche width of CAZymes genes and were marked by a high abundance of periplasmic transporter protein TonB and members of the major facilitator superfamily (MFS). The increasing contribution of genes encoding CAZymes and transporters for Alteromonas in bottom water contrasted to surface water and their metabolism are tightly related with particulate carbohydrates (pectin, alginate, starch, lignin-cellulose, chitin, and peptidoglycan) rather than on the utilization of ambient-water DOC. Candidatus Pelagibacter (Alphaproteobacteria) had a narrow glycan niche and was primarily preferred for nitrogen-containing carbohydrates, while their abundant sugar ABC (ATP binding cassette) transporter supported the scavenging mode for carbohydrate assimilation. Planctomycetota, Verrucomicrobiota, and Bacteroidota had similar potential glycan niches in the consumption of the main component of transparent exopolymer particles (sulfated fucose and rhamnose containing polysaccharide and sulfated-N-glycan), developing considerable niche overlap among these taxa. The most abundant CAZymes and transporter genes as well as the widest glycan niche in the abundant bacterial taxa implied their potential key roles on the organic carbon utilization, and the high degree of glycan niches separation and polysaccharide composition importantly influenced bacterial communities in the coastal waters of PRE. These findings expand the current understanding of the organic carbon biotransformation, underlying the size-fractionated glycan niche separation near the estuarine system.

Description: Over half a century ago, following the development and integration of the adequate technology, the deep sea transitioned from being the last frontier for exploration on our planet to the subject of industrial-level exploitation. While the main impacts in the deep sea are currently the product of large-scale fisheries and offshore energy production (mainly oil and gas), the expected transition of the global economy towards greener (or, in this case, bluer) solutions will likely include the use of the marine domain as a setting for renewable energy infrastructure (e.g., floating wind farms loosely anchored to the seabed) and seabed mining for rare minerals that are fundamental to the renewable energy technologies. Despite the risks posed by these impacts, the development of robust management guidelines for deep-sea habitats and resources has not kept pace with technological progress and growing economic forces. As a result, this highlights an opportunity to develop standardized methodologies, goals and overall strategies. To achieve this, it is imperative for scientists and managing authorities to reach a high level of consensus in both data acquisition and treatment, as well as in reliable ecological indicators to track both natural and human-induced ecosystem changes. (...)

Description: Background: Biological invasions threaten the functioning of ecosystems, biodiversity, and human well-being by degrading ecosystem services and eliciting massive economic costs. The European Union has historically been a hub for cultural development and global trade, and thus, has extensive opportunities for the introduction and spread of alien species. While reported costs of biological invasions to some member states have been recently assessed, ongoing knowledge gaps in taxonomic and spatio-temporal data suggest that these costs were considerably underestimated. Results: We used the latest available cost data in InvaCost (v4.1)—the most comprehensive database on the costs of biological invasions—to assess the magnitude of this underestimation within the European Union via projections of current and future invasion costs. We used macroeconomic scaling and temporal modelling approaches to project available cost information over gaps in taxa, space, and time, thereby producing a more complete estimate for the European Union economy. We identified that only 259 out of 13,331 (~ 1%) known invasive alien species have reported costs in the European Union. Using a conservative subset of highly reliable, observed, country-level cost entries from 49 species (totalling US$4.7 billion; 2017 value), combined with the establishment data of alien species within European Union member states, we projected unreported cost data for all member states. Conclusions: Our corrected estimate of observed costs was potentially 501% higher (US$28.0 billion) than currently recorded. Using future projections of current estimates, we also identified a substantial increase in costs and costly species (US$148.2 billion) by 2040. We urge that cost reporting be improved to clarify the economic impacts of greatest concern, concomitant with coordinated international action to prevent and mitigate the impacts of invasive alien species in the European Union and globally.

Description: Introduction: Active hydrothermal vents of volcanic origin provide a remarkable manifestation of life on Earth under extreme conditions, which may have consequences for our understanding of habitability on other terrestrial bodies as well. Methods: Here, we performed for the first time Illumina sequencing of bacterial and archaeal communities on sub-seafloor samples collected from the Santorini-Kolumbo volcanic field. A total of 19 (3-m long) gravity corers were collected and processed for microbial community analysis. Results: From a total of 6,46,671 produced V4 sequences for all samples, a total of 10,496 different Operational Taxonomic Units (OTUs) were identified that were assigned to 40 bacterial and 9 archaeal phyla and 14 candidate divisions. On average, the most abundant phyla in all samples were Chloroflexi (Chloroflexota) (24.62%), followed by Proteobacteria (Pseudomonadota) (11.29%), Firmicutes (Bacillota) (10.73%), Crenarchaeota (Thermoproteota) (8.55%), and Acidobacteria (Acidobacteriota) (8.07%). At the genus level, a total of 286 known genera and candidate genera were mostly dominated by members of Bacillus, Thermoflexus, Desulfatiglans, Pseudoalteromonas, and Pseudomonas. Discussion: In most of the stations, the Chao1 values at the deeper layers were comparable to the surface sediment samples denoting the high diversity in the subsurface of these ecosystems. Heatmap analysis based on the 100 most abundant OTUs, grouped the sampling stations according to their geographical location, placing together the two hottest stations (up to 99°C). This result indicates that this specific area within the active Kolumbo crater create a distinct niche, where microorganisms with adaptation strategies to withstand heat stresses can thrive, such as the endospore-forming Firmicutes.

Description: Tropical environments with unique abiotic and biotic factors—such as salt ponds, mangroves, and coral reefs—are often in close proximity. The heterogeneity of these environments is reflected in community shifts over short distances, resulting in high biodiversity. While phytoplankton assemblages physically associated with corals, particularly their symbionts, are well studied, less is known about phytoplankton diversity across tropical aquatic environments. We assess shifts in phytoplankton community composition along inshore to offshore gradients by sequencing and analyzing 16S rRNA gene amplicons using primers targeting the V1-V2 region that capture plastids from eukaryotic phytoplankton and cyanobacteria, as well as heterotrophic bacteria. Microbial alpha diversity computed from 16S V1-V2 amplicon sequence variant (ASV) data from 282 samples collected in and around Curaçao, in the Southern Caribbean Sea, varied more within the dynamic salt ponds, salterns, and mangroves, compared to the seemingly stable above-reef, off-reef, and open sea environments. Among eukaryotic phytoplankton, stramenopiles often exhibited the highest relative abundances in mangrove, above-reef, off-reef, and open sea environments, where cyanobacteria also showed high relative abundances. Within stramenopiles, diatom amplicons dominated in salt ponds and mangroves, while dictyochophytes and pelagophytes prevailed above reefs and offshore. Green algae and cryptophytes were also present, and the former exhibited transitions following the gradient from inland to offshore. Chlorophytes and prasinophyte Class IV dominated in salt ponds, while prasinophyte Class II, including Micromonas commoda and Ostreococcus Clade OII, had the highest relative abundances of green algae in mangroves, above-reef, off-reef, and the open sea. To improve Class II prasinophyte classification, we sequenced 18S rRNA gene amplicons from the V4 region in 41 samples which were used to interrelate plastid-based results with information on uncultured prasinophyte species from prior 18S rRNA gene-based studies. This highlighted the presence of newly described Ostreococcus bengalensis and two Micromonas candidate species. Network analyses identified co-occurrence patterns between individual phytoplankton groups, including cyanobacteria, and heterotrophic bacteria. Our study reveals multiple uncultured and novel lineages within green algae and dictyochophytes in tropical marine habitats. Collectively, the algal diversity patterns and potential co-occurrence relationships observed in connection to physicochemical and spatial influences help provide a baseline against which future change can be assessed.

Description: Surface wind is taken as the primary driver of upwelling in the eastern boundary upwelling systems. The fluctuation of momentum flux associated with the variation in wind regulates the nutrient supply to the euphotic surface layer via changing the properties of oceanic mixed layer depth, the coastal and offshore upwelling, and horizontal advection. Here, the spatial and temporal variability of the surface wind field over the last seven decades across the Peruvian upwelling system is investigated. Strong fluctuations in seasonal to decadal timescales are found over the entire upwelling system. A semi-periodic wind fluctuation on an interannual timescale is found, which is closely related to the regional sea surface temperature and can be attributed to the El Niño Southern Oscillation (ENSO). However, the wind anomaly patterns during positive and negative phases of ENSO are not opposite, which suggests an asymmetric response of local wind to ENSO cycles. In addition, a semi-regular fluctuation on the decadal timescale is evident in the wind field, which can be attributed to the Interdecadal Pacific Oscillation (IPO). Our results show that the sea surface temperature over the Humboldt Upwelling System is closely connected to local wind stress and the wind stress curl. The SST wind stress co-variability seems more pronounced in the coastal upwelling cells, in which equatorward winds are very likely accompanied by robust cooling over the coastal zones. Over the past seven decades, wind speed underwent a slightly positive trend. However, the spatial pattern of the trend features considerable heterogeneity with larger values near the coastal upwelling cells.

Description: Seamounts are abundant features on the seafloor that serve as hotspots and barriers for the dispersal of benthic organisms. The primary focus of seamount ecology has typically been on the composition and distribution of faunal communities, with far less attention given to microbial communities. Here, we investigated the microbial communities in the water column (0-3400 m depth) and sediments (619-3883 m depth, 0-16 cm below seafloor) along the ice-covered Arctic ridge system called the Langseth Ridge. We contextualized the microbial community composition with data on the benthic trophic state (i.e., organic matter, chlorophyll- a content, and porewater geochemistry) and substrate type (i.e., sponge mats, sediments, basaltic pebbles). Our results showed slow current velocities throughout the water column, a shift in the pelagic microbial community from a dominance of Bacteroidia in the 0-10 m depth towards Proteobacteria and Nitrososphaeria below the epipelagic zone. In general, the pelagic microbial communities showed a high degree of similarity between the Langseth Ridge seamounts to a northern reference site. The only notable differences were decreases in richness between ~600 m and the bottom waters (~10 m above the seafloor) that suggest a pelagic-benthic coupling mediated by filter feeding of sponges living on the seamount summits. On the seafloor, the sponge spicule mats, and polychaete worms were the principal source of variation in sedimentary biogeochemistry and the benthic microbial community structure. The porewater signature suggested that low organic matter degradation rates are accompanied by a microbial community typical of deep-sea oligotrophic environments, such as Proteobacteria, Acidimicrobiia, Dehalococcoidia, Nitrospira, and archaeal Nitrososphaeria. The combined analysis of biogeochemical parameters and the microbial community suggests that the sponges play a significant role for pelagic-benthic coupling and acted as ecosystem engineers on the seafloor of ice-covered seamounts in the oligotrophic central Arctic Ocean.

Description: Ocean deoxygenation and expansion and intensification of hypoxia in the ocean are a major, growing threat to marine ecosystems. Measures currently used to protect marine biodiversity (e.g., marine protected areas) are ineffective in countering this threat. Here, we highlight the example of the Gulf of St. Lawrence in eastern Canada, where oxygen loss is not only due to eutrophication (which can be mitigated by nutrient controls) but also is a consequence of ocean circulation change and warming. Climate-related loss of oxygen will be an increasingly widespread source of risk to marine biodiversity over this century. Again using the Gulf of St. Lawrence as an example, we show that production of oxygen by the green hydrogen industry can be comparable to the loss rate of dissolved oxygen on large spatial scales, offering new possibilities for mitigation. However, this mitigation approach has rarely been considered for marine environments to date. Given confluence of increasing risk to marine ecosystems from oxygen loss and rapid emergence, worldwide, of industrial sources of pure oxygen, which are likely to be located in coastal regions, we believe this option will be proposed increasingly in coming years, including by the private sector. We argue that it is urgent for ocean scientists, engineers, and policymakers to recognize and address this emerging potential. A coordinated research effort should be established immediately in order to harness the potential of the green hydrogen industry to mitigate major impacts of climate change on marine biodiversity, and avoid any unintended negative consequences.

Description: Two atmospheric feedbacks play an important role in the dynamics of the El Nino/Southern Oscillation (ENSO), namely the amplifying zonal wind feedback and the damping heat flux feedback. Here we investigate how and why both feedbacks change under global warming in climate models participating in the 5th and 6th phase of the Coupled Model Intercomparison Project (CMIP5 and CMIP6) under the business-as-usual scenario (RCP8.5 and SSP5-8.5, respectively). The amplifying zonal wind feedback over the western equatorial Pacific (WEP) becomes significantly stronger in two third of the models, on average by 12 +/- 7% in these models. The heat flux damping feedback over the eastern and central equatorial Pacific (EEP and CEP, respectively) increases as well in nearly all models, with the damping effect increasing on average by 18 +/- 11%. The simultaneous strengthening of the two feedbacks can be explained by the stronger warming in the EEP relative to the WEP and the off-equatorial regions, which shifts the rising branch of the Pacific Walker Circulation to the east and increases the mean convection over the CEP. This in turn leads to a stronger vertical wind response during ENSO events over the CEP that strengthens both atmospheric feedbacks. We separate the climate models into sub-ensembles with STRONG and WEAK ENSO atmospheric feedbacks, as 2/3 of the models underestimate both feedbacks under present-day conditions by more than 40%, causing an error compensation in the ENSO dynamics. The biased mean state in WEAK in 20C constrains the ENSO atmospheric feedback projection in 21C, as the models of the WEAK sub-ensemble also have weaker ENSO atmospheric feedbacks in 21C. Further, due to the more realistic dynamics and teleconnections, we postulate that one should have more confidence in the ENSO predictions with models belonging to the STRONG sub-ensemble. Finally, we analyze the relation between ENSO amplitude change and ENSO atmospheric feedback change. We find that models simulating an eastward shift of the zonal wind feedback and increasing precipitation over the EEP during Eastern Pacific El Nino events tend to predict a larger ENSO amplitude in response to global warming.

Description: In recent decades, Arctic summer sea ice extent (SIE) has shown a rapid decline overlaid with large interannual variations, both of which are influenced by geopotential height anomalies over Greenland (GL-high) and the central Arctic (CA-high). In this study, we find that SIE along coastal Siberia (Sib-SIE) and Alaska (Ala-SIE) accounts for about 65% and 21% of the Arctic SIE interannual variability, respectively. Variability in Ala-SIE is related to the GL-high, whereas variability in Sib-SIE is related to the CA-high. A decreased Ala-SIE is associated with decreased cloud cover and increased easterly winds along the Alaskan coast, promoting ice-albedo feedback. A decreased Sib-SIE is associated with a significant increase in water vapor and downward longwave radiation (DLR) along the Siberian coast. The years 2012 and 2020 with minimum recorded ASIE are used as examples. Compared to climatology, summer 2012 is characterized by a significantly enhanced GL-high with major sea ice loss along the Alaskan coast, while summer 2020 is characterized by an enhanced CA-high with sea ice loss focused along the Siberian coast. In 2012, the lack of cloud cover along the Alaskan coast contributed to an increase in incoming solar radiation, amplifying ice-albedo feedback there; while in 2020 the opposite occurs with an increase in cloud cover along the Alaskan coast, resulting in a slight increase in sea ice there. Along the Siberian coast, increased DLR in 2020 plays a dominant role in sea ice loss and increased cloud cover and water vapor both contribute to the increased DLR.

Description: Volcanic flanks subject to hydrothermal alteration become mechanically weak and gravitationally unstable, which may collapse and develop far-reaching landslides. The dynamics and trajectories of volcanic landslides are hardly preserved and challenging to determine, which is due to the steep slopes and the inherent instability. Here we analyze the proximal deposits of the 21 July 2014, landslide at Askja (Iceland), by combining high-resolution imagery from satellites and Unoccupied Aircraft Systems. We performed a Principal Component Analysis in combination with supervised classification to identify different material classes and altered rocks. We trained a maximum-likelihood classifier and were able to distinguish 7 different material classes and compare these to ground-based hyperspectral measurements that we conducted on different rock types found in the field. Results underline that the Northern part of the landslide source region is a hydrothermally altered material class, which bifurcates halfway downslope and then extends to the lake. We find that a large portion of this material is originating from a lava body at the landslide headwall, which is the persistent site of intense hydrothermal activity. By comparing the classification result to in-situ hyperspectral measurements, we were able to further identify the involved types of rocks and the degree of hydrothermal alteration. We further discuss associated effects of mechanical weakening and the relevance of the heterogeneous materials for the dynamics and processes of the landslide. As the study demonstrates the success of our approach for identification of altered and less altered materials, important implications for hazard assessment in the Askja caldera and elsewhere can be drawn.

Description: Atlantic herring (Clupea harengus) has a complex population structure and displays a variety of reproductive strategies. Differences in reproductive strategies among herring populations are linked to their time of spawning, as well as to their reproductive investment which can be an indicator for migratory vs. stationary behavior. These differences are reflected in the number of oocytes (fecundity) and the size of the oocytes prior spawning. We studied potential mixing of herring with different reproductive strategies during the spring spawning season on a coastal spawning ground. It has been hypothesized that both spring and autumn spawning herring co-occur on this specific spawning ground. Therefore, we investigated the reproductive traits oocyte size, fecundity, fertilization success as well as length of the hatching larvae during the spring spawning season from February to April. We used a set of 11 single nucleotide polymorphism markers (SNPs), which are associated with spawning season, to genetically identify autumn and spring spawning herring. Reproductive traits were investigated separately within these genetically distinct spawning types. Furthermore, we used multivariate analyses to identify groups with potentially different reproductive strategies within the genetic spring spawners. Our results indicate that mixing between ripe spring and autumn spawners occurs on the spawning ground during spring, with ripe autumn spawners being generally smaller but having larger oocytes than spring spawners. Within spring spawners, we found large variability in reproductive traits. A following multivariate cluster analysis indicated two groups with different reproductive investment. Comparisons with other herring populations along the Norwegian coastline suggest that the high variability can be explained by the co-occurrence of groups with different reproductive investments potentially resulting from stationary or migratory behavior. Fertilization success and the length of the hatching larvae decreased with progression of the spawning season, with strong inter-individual variation, supporting our findings. Incorporating such complex population dynamics into management strategies of this species will be essential to build its future population resilience.

Description: A growing population on a planet with limited resources demands finding new sources of protein. Hence, fisheries are turning their perspectives towards mesopelagic fish, which have, so far, remained relatively unexploited and poorly studied. Large uncertainties are associated with regards to their biomass, turn-over rates, susceptibility to environmental forcing and ecological and biogeochemical role. Models are useful to disentangle sources of uncertainties and to understand the impact of different processes on the biomass. In this study, we employed two food-web models – OSMOSE and the model by Anderson et al. (2019, or A2019) – coupled to a regional physical–biogeochemical model to simulate mesopelagic fish in the Eastern Tropical South Pacific ocean. The model by A2019 produced the largest biomass estimate, 26 to 130% higher than OSMOSE depending on the mortality parameters used. However, OSMOSE was calibrated to match observations in the coastal region off Peru and its temporal variability is affected by an explicit life cycle and food web. In contrast, the model by A2019 is more convenient to perform uncertainty analysis and it can be easily coupled to a biogeochemical model to estimate mesopelagic fish biomass. However, it is based on a flow analysis that had been previously applied to estimate global biomass of mesopelagic fish but has never been calibrated for the Eastern Tropical South Pacific. Furthermore, it assumes a steady-state in the energy transfer between primary production and mesopelagic fish, which may be an oversimplification for this highly dynamic system. OSMOSE is convenient to understand the interactions of the ecosystem and how including different life stages affects the model response. The combined strengths of both models allow us to study mesopelagic fish from a holistic perspective, taking into account energy fluxes and biomass uncertainties based on primary production, as well as complex ecological interactions.

Description: The subarctic front (SAF) in the pelagic North Pacific is the northernmost front of the Kuroshio-Oyashio transition zone separating the subpolar and subtropical gyres and is marked by a strong sea surface temperature gradient. A complex interplay of e.g. variations of currents, the wind system and other forcing mechanisms causes shifts of the SAF’s position on timescales from orbital to interannual. In this study, we present proxy data from the Emperor Seamount chain, which reveal a link between long-term ENSO (El Niño/Southern Oscillation) dynamics in the tropics and shifts of the SAF. Based on sediment core SO264-45-2 from Jimmu Seamount (46°33.792’N, 169°36.072’E) located close to the modern position of the SAF, we reconstruct changes in (sub)surface temperature ((sub)SST Mg/Ca ) and δ 18 O sw-ivc (approximating salinities) via combined Mg/Ca and δ 18 O analyses of the shallow-dwelling foraminifera Globigerina bulloides and the near-thermocline-dwelling Neogloboquadrina pachyderma , biological productivity (XRF-based Ba/Ti ratios), and terrigenous input via dust (XRF-based Fe). From ~600 to ~280 ka BP we observe significantly higher SST Mg/Ca than after an abrupt change at 280 ka BP. We assume that during this time warmer water from the Kuroshio-Oyashio transition zone reached the core site, reflecting a shift of the SAF from a position at or even north of our study site prior to 280 ka BP to a position south of our study site after 280 ka BP. We propose that such a northward displacement of the SAF between 600-280 ka BP was induced by sustained La Niña-like conditions, which led to increased transport of tropical ocean heat into the Kuroshio-Oyashio transition zone via the Kuroshio Current. After ~280 ka BP, the change to more El Niño-like conditions led to less heat transfer via the Kuroshio Current with the SAF remaining south of the core location. In contrast, our productivity record shows a clear glacial-interglacial pattern that is common in the North Pacific. We assume that this pattern is connected to changes in nutrient supply or utilization, which are not primarily driven by changes of the Kuroshio and Oyashio Currents or the SAF.

Description: One of the major problems in the volcanic surveillance is how data from several techniques can be correlated and used to discriminate between possible precursors of volcanic eruptions and changes related to non-eruptive processes. Gas chemical surveys and measurements of SO 2 emission rates performed in the past (2006–2019) at Lastarria volcano in Northern Chile have revealed a persistent increment of magmatic sourced gas emissions since late November 2012, following a 13 years period of intense ground uplift. In this work, we provide new insights into the gas-chemical evolution of Lastarria’s fumarolic discharges obtained from direct sampling (2006–2019) and SO 2 emission rates using UV camera and DOAS instruments (2018–2019) and link these to pre-existing information on ground deformation (1998–2016) in order to determine the origin of observed degassing and ground deformation processes. We revise the four mechanisms originally proposed as alternatives by Lopez et al. (Geosphere, 2018, 14 (3), 983–1007) to explain the changes observed in the fluid geochemistry and ground deformation between 2009 and 2012, in order to explain major changes in gas-geochemistry over an extended period between 1998 and 2019. We hypothesize that a continuous sequence of processes explains the evolution in the fluid geochemistry of fumarolic discharges. Two mechanisms are responsible of the changes in the gas composition during the studied period, corresponding to a 1) deep magma chamber (7–15 km depth) pressurized by volatile exsolution (1998–2020), which is responsible of the large-scale deformation; followed by 2) a crystallization-induced degassing (2001–2020) and pressurization of the hydrothermal system (2003-early November 2012), where the former process induced the changes in the gas composition from hydrothermal-dominated to magmatic-dominated, whereas the last produced the small-scale deformation at Lastarria volcano. The changes in the gas composition since late November 2012, which were strongly dominated by magmatic volatiles, produced two consecutive processes: 1) acidification (late November 2012–2020) and 2) depletion (2019–2020) of the hydrothermal system. In this work we have shown that a long-term surveillance of the chemistry of fluid discharges provides valuable insights into underlying magmatic/volcanic processes, and consequently, for forecasting future eruptions.

Description: The aim of this work is to present the food web models developed using the Ecopath with Ecosim (EwE) software tool to describe structure and functioning of various European marine ecosystems (eastern, central and western Mediterranean Sea; Black Sea; Bay of Biscay, Celtic Sea and Iberian coast; Baltic Sea; North Sea; English Channel, Irish Sea and west Scottish Sea; and Norwegian and Barents Seas). A total of 195 Ecopath models based on 168 scientific publications, which report original, updated and modified versions, were reviewed. Seventy models included Ecosim temporal simulations while 28 implemented Ecospace spatiotemporal dynamics. Most of the models and publications referred to the western Mediterranean Sea followed by the English Channel, Irish Sea and west Scottish Sea sub-regions. In the Mediterranean Sea, the western region had the largest number of models and publications, followed by the central and eastern regions; similar trends were observed in previous literature reviews. Most models addressed ecosystem functioning and fisheries-related hypotheses while several investigated the impact of climate change, the presence of alien species, aquaculture, chemical pollution, infrastructure, and energy production. Model complexity (i.e., number of functional groups) increased over time. Main forcing factors considered to run spatial and temporal simulations were trophic interactions, fishery, and primary production. Average scores of ecosystem indicators derived from the Ecopath summary statistics were compared. Uncertainty was also investigated based on the use of the Ecosampler plug-in and the Monte Carlo routine; only one third of the reviewed publications incorporated uncertainty analysis. Only a limited number of the models included the use of the ECOIND plug-in which provides the user with quantitative output of ecological indicators. We assert that the EwE modelling approach is a successful tool which provides a quantitative framework to analyse the structure and dynamics of ecosystems, and to evaluate the potential impacts of different management scenarios.

Description: The paper presents petrographic, mineralogical, and geochemical data on dunites, pyroxenites, peridotites, and gabbroids of the Kamchatsky Mys ophiolite. These data were acquired to distinguish cogenetic assemblages of igneous rocks, gain an insight into their geodynamic settings, and test various criteria of genetic links between the different magmatic rocks of ophiolites. The ultramafic and mafic rocks are shown to belong to two series, which differ in the compositions of the primary minerals, bulk rocks, and estimated trapped melts. The rocks of these series are found out to have been produced by geochemically different melts in different geodynamic settings, and during different episodes of mantle magmatism. The rocks of the high-Ti series (gabbro of the Olenegorsk massif, dunite and melanogabbro xenoliths in them, and vein gabbro in these xenoliths) crystallized from N-MORB melts in an oceanic spreading center. The rocks of the low-Ti series (dunite, pyroxenite, and gabbro veins in the residual spinel peridotites of the Mount Soldatskaya massif, as well as pyroxenite, peridotite, and gabbro alluvium and diluvium in the central and western parts of the peninsula) crystallized from water-rich boninite melts in relation to initial subduction magmatism. Taken into account the absence of boninite lavas from the Kamchatsky Mys ophiolite, the plutonic ultramafic rocks (including the rocks of the veins) might be the only evidence of subduction boninitic magmatism in the ophiolites. It was demonstrated that conclusions about the geodynamic settings of plutonic ultramafic and mafic rocks and recognition of cogenetic relations of these rocks with spatially associated basalts are more reliable when derived from the compositions of the trapped melts, which are estimated from their bulk geochemistry and primary mineral compositions, than when they are based on the mineral compositions only.

Description: Kharchinsky and Zarechny volcanoes and the Kharchinsky Lake zone of monogenic cones are unique eruptive centers of magnesian lavas located above the northern margin of the Pacific plate subducting beneath Kamchatka. This paper presents new geochemical data on the composition of rocks (55 samples) and minerals (over 900 analyses of olivine, pyroxenes, amphibole, and plagioclase) of these centers analyzed by XRF and LA-ICP-MS (rocks) and electron microprobe (minerals). Most of the studied rocks are magnesian (Mg# = 60–75 mol %) medium-K basalts and basaltic andesites. Moderate-magnesian (Mg# = 52–59 mol %) basaltic andesites are present among the monogenic cones of Kharchinsky Lake. The rare rock varieties include the high-K basalts–basaltic andesites of dikes in the center of Kharchinsky volcano and the magnesian andesites (Mg# = 58–61 mol %) of the extrusions of Zarechnу volcano. The distribution of trace-element contents in these samples demonstrates enrichment in large-ion lithophile elements and light REEs at depletion in high field strength elements and heavy REEs, as is typical of arc rocks. The high-K basalts and basaltic andesites show anomalous enrichment in Ba (〉1000 ppm), Th (〉3.8 ppm), U (〉1.8 ppm), Sr (〉 800 ppm, Sr/Y 〉 50), and light REE (La 〉 20 ppm), and their compositions are close to those of low-Si adakites. The basalts and basaltic andesites contain phenocrysts of high-Mg olivine (up to Fo92.6) and clinopyroxene (Mg # up to 91 mol %). The rocks show petrographic and geochemical evidence of fractional crystallization, along with the processes of mineral accumulation and magma mixing. Some of the olivine phenocrysts show high NiO contents (up to 5000 ppm) and an elevated Fe/Mn ratio (up to 80), which were interpreted as evidence of the participation of a pyroxenite source in the magma generation processes. The use of the Ca/Fe and Ni/Mg ratios allowed us to distinguish the composition fields and evolution trends of olivine associated with different sources: peridotite and pyroxenite, which were formed by a reaction between mantle-wedge peridotites and high-Si melts of the subducted oceanic crust. The new data are consistent with other lines of evidence of melting of the subducted Pacific plate edge beneath the northern part of the Central Kamchatka Depression at the Kurile–Kamchatka and Aleutian subduction zone junction and testify to a significant heterogeneity of the mantle in this area.

Description: Climate change and plastic pollution are two of the most pressing environmental challenges caused by human activity, and they are directly and indirectly linked. We focus on the relationship between marine plastic litter and the air-sea flux of greenhouse gases (GHGs). Marine plastic litter has the potential to both enhance and reduce oceanic GHG fluxes, but this depends on many factors that are not well understood. Different kinds of plastic behave quite differently in the sea, affecting air-sea gas exchange in different, largely unknown, ways. The mechanisms of air-sea exchange of GHGs have been extensively studied and if air-sea gas transfer coefficients and concentrations of the gas in water and air are known, calculating the resulting GHG fluxes is reasonably straightforward. However, relatively little is known about the consequences of marine plastic litter for gas transfer coefficients, concentrations, and fluxes. Here we evaluate the most important aspects controlling the exchange of GHGs between the sea and the atmosphere and how marine plastic litter could change these. The aim is to move towards improving air-sea GHG flux calculations in the presence of plastic litter and we have largely limited ourselves to identifying processes, rather than estimating relative importance.

Description: Communicating environmental change and mitigation scenarios to stakeholders and decision-makers can be challenging. Immersive environments offer an innovative approach for knowledge transfer, allowing science-based scenarios to be discussed interactively. The use of such environments is particularly helpful for the analysis of large, multi-component geospatial datasets, as commonly employed in the classification of ecosystems. Virtual environments can play an important role in conveying and discussing the findings gathered from these geomorphometric datasets. However, textured meshes and point clouds are not always well suited for direct import to a virtual reality or the creation of a truly immersive environment, and often result in geometrical artifacts, which can be misinterpreted during the import to a game engine. Such technical hurdles may lead to viewers rejecting the experience altogether, failing to achieve a higher educational purpose. In this study, we apply an asset-based approach to create an immersive virtual representation of a coastal environment. The focus hereby is on the coastal vegetation and changes in species distribution, which could potentially be triggered by the impact of climate change. We present an easy-to-use blueprint for the game engine EPIC Unreal Engine 5. In contrast to traditional virtual reality environments, which use static textured mesh data derived from photogrammetry, this asset-based approach enables the use of dynamic and physical properties (e.g. vegetation moving due to wind or waves), which makes the virtual environment more immersive. This will help to stimulate understanding and discussion amongst different stakeholders, and will also help to foster inclusion in earth- and environmental science education.

Description: Enhanced mineral dissolution in the benthic environment is currently discussed as a potential technique for ocean alkalinity enhancement (OAE) to reduce atmospheric CO 2 levels. This study explores how biogeochemical processes affect the dissolution of alkaline minerals in surface sediments during laboratory incubation experiments. These involved introducing dunite and calcite to organic-rich sediments from the Baltic Sea under controlled conditions in an oxic environment. The sediment cores were incubated with Baltic Sea bottom water. Findings reveal that the addition of calcite increased the benthic alkalinity release from 0.4 μmol cm −2 d −1 (control) to 1.4 μmol cm −2 d −1 (calcite) as well as other weathering products such as calcium. However, these enhanced fluxes returned to lower fluxes after approximately 4 weeks yet still higher than the un-amended controls. Microbial activity appeared to be the primary driver for lowering pore water pH and thus enhanced weathering. In several sediment cores, pH profiles taken at the start of the experiments indicated activity of sulfur oxidizing Beggiatoa spp, which was verified by RNA-profiling of 16S rRNA genes. The pH profiles transitioned to those commonly associated with the activity of cable bacteria as the experiments progressed. The metabolic activity of cable bacteria would explain the significantly lower pH values (~5.6) at sediment depths of 1–3 cm, which would favor substantial calcite dissolution. However, a high abundance of cable bacteria was not reflected in 16S rRNA sequence data. Total alkalinity (TA) fluxes in these cores increased by a factor of ~3, with excess TA/calcium ratios indicating that the enhanced flux originated from calcite dissolution. The dissolution of dunite or the potential formation of secondary minerals could not be identified due to the strong natural flux of silicic acid, likely due to biogenic silica dissolution. Furthermore, no accumulation of potentially harmful metals such as nickel was observed, as highlighted as a potential risk in other studies concerning OAE. Given the complexity of sediment chemistry and changes of the benthic conditions induced by the incubation, it remains challenging to distinguish between natural and enhanced mineral weathering. Further investigation, including the identification of suitable tracers for mineral dissolution, are necessary to assess the feasibility of benthic weathering as a practical approach for OAE and climate change mitigation.

Description: The warming climate is causing a strengthening of ocean stratification. Ocean stratification, in turn, has significant impacts on physical, biogeochemical and ecological processes, such as ocean circulation, ventilation, air-sea interactions, nutrient fluxes, primary productivity and fisheries. How these processes are affected in detail by changing stratification still remains uncertain and are likely to vary locally. Here, we investigate the state and trend of different parameters characterizing the stratification of the global upper-ocean which can be derived from Argo profiles for the period 2006-2021. Among those parameters are mixed layer depth, magnitude and depth of the vertical stratification maximum. The summertime stratification maximum has increased in both hemispheres, respectively. During wintertime, the stratification maximum has intensified in the Northern Hemisphere, while changes in the Southern Hemisphere have been relatively small. Comparisons to mixed layer characteristics show that a strengthening stratification is mainly accompanied by a warming and freshening of the mixed layer. In agreement with previous observational studies, we find a large-scale mixed layer deepening that regionally contributes to the increasing stratification. Globally, the vertical stratification maximum strengthens by 7-8% and the mixed layer deepens by 4 m during 2006-2021. This hints to an ongoing de-coupling of the surface ocean from the ocean interior. The investigated changes can help determine the origin of existing model-observation discrepancies and improve predictions on climate change impact on upper-ocean ecology and biogeochemistry.

Description: Archaea play an important role in global biogeochemical cycles and are considered ancestral to eukaryotes. The unique lipid composition of archaea, characterized by isoprenoid alkyl chains and ether linkage to glycerol-1-phosphate, offers valuable insights into archaeal phylogeny and evolution. However, comprehensive studies focusing on archaeal lipidomes, especially at the intact polar lipid level, are currently limited. Here, we built an in-house library of archaeal lipids by using high-performance liquid chromatography coupled with mass-spectrometry, which was integrated with bioinformatics and molecular network analyses. Seven halobacterial strains, representing three distinct orders, were cultured under identical conditions to investigate their lipidomes. A total of 162 features were identified, corresponding to 107 lipids that could be assigned to different strains. Clustering analyses of both core lipids and total lipids matched the phylogeny of Halobacteria at the order level. Notably, lipids such as triglycosyl diether-phosphatidyl acid and bis-sulfate glycosyl lipids were specific to particular groups and could serve as diagnostic intact lipid biomarkers for Halobacteria. Furthermore, the analysis of network-coordinated features facilitated the linkage of unknown lipid compounds to phylogeny, which promotes a lipidome to phylogeny matchup among three Haloferax strains, thereby expanding the knowledge of the halobacterial lipidome. Our study provides a comprehensive view of the lipidomes of the seven strains of Halobacteria and highlights the potential of lipidomics for studying archaeal phylogeny.

Description: Microplastic is a ubiquitous marine pollutant whose small dimensions make it biologically available to phytoplankton and zooplankton. These organisms are crucial as the basis of the marine food web and for the export of organic material in the form of faecal pellets from the surface to deeper in the water column, forming a long-term carbon sink. Previous laboratory studies have demonstrated empirically that ingestion of low density microplastics reduces the sinking rates of zooplankton faecal pellets. This study uses a complex earth system model to analyse this effect and assess its wider impacts in a changing climate. Results show that the slowing of faecal pellet sinking stimulates changes to ecosystems regionally and reduces ocean carbon uptake by about 4.4 Pg C between the years 1950-2100, 0.24% of anthropogenic emissions over this time. However, perturbation of organic particle fluxes is significant, especially in gyres, and of the order of climate change impacts over the same time period. We calculate that plastics carbon has a 3 orders of magnitude greater impact on marine ecosystems than atmospheric carbon over our centennial timescale. Large uncertainties in model parameters and simplistic model structure suggest our results should be interpreted as motivation to further investigate parameter estimation, calcification responses to pollution, and the combined effects of multiple impact mechanisms on ecosystems.

Description: The three-dimensional (3D) structure of habitat-forming corals has profound impacts on reef ecosystem processes. Elucidating coral structural responses to the environment is therefore crucial to understand changes in these ecosystems. However, little is known of how environmental factors shape coral structure in deep and dark waters, where cold-water coral (CWC) reefs thrive. Here, we attempt to infer the influence of current flow on CWC framework architecture, using 3D scanning to quantify colony shape traits (volume compactness and surface complexity) in the reef-building CWC Desmophyllum pertusum from adjacent fjord and offshore habitats with contrasting flow regimes. We find substantial architectural variability both between and within habitats. We show that corals are generally more compact in the fjord habitat, reflecting the prevailing higher current speeds, although differences in volume compactness between fjord and offshore corals are more subtle when comparing the fjord with the more exposed side of the offshore setting, probably due to locally intensified currents. Conversely, we observe no clear disparity in coral surface complexity between habitats (despite its positive correlation with volume compactness), suggesting it is not affected by current speed. Unlike volume compactness, surface complexity is similarly variable within a single colony as it is between colonies within the same habitat or between habitats and is therefore perhaps more dependent than volume compactness on microenvironmental conditions. These findings suggest a highly plastic, trait-specific and functionally relevant structural response of CWCs to current flow and underscore the importance of multiple concurrent sources of hydrodynamic forcing on CWC growth.

Description: Silicon is one of the most abundant chemical elements in the universe. On Earth, it forms sediments, minerals, and rocks. In the ocean, silicon is found in a dissolved form that can be used by many organisms to grow. You probably know that humans use calcium to build their skeletons, but did you know that there are creatures capable of forming skeletons out of silicon? Organisms capable of capturing dissolved silicon from the environment and transforming it into glassy skeletons are called silicifiers. Silicifiers use a unique process called biosilicification to create their skeletons. In the marine ecosystem, silicifiers come in a surprising variety of shapes and sizes, and they include, among others, diatoms, rhizarians, and sponges. These three groups, so diverse and yet so similar, are essential to the health of the oceans.

Description: Squid play a major role in the Southern Ocean food web. However, their age and growth remain poorly studied. Here, using upper and lower beaks of Moroteuthopsis longimana collected from the diet of Dissostichus mawsoni from Pacific and Atlantic sectors of the Southern Ocean, we studied: (1) Feasibility of using beaks collected from predators’ stomachs to study the age of Southern Ocean oceanic squid; and (2) Age estimation and growth patterns of M. longimana. The rostrum sagittal section (RSS) of both beaks had micro-increments, with the lower beak being the best to observe and count a readable sequence of increments to estimate the age. Assuming a daily deposition of increments, our results suggest that M. longimana can live up to 820 days and may hatch throughout the year. Studied individuals presented a consistent growth rate from hatching to death but with, at least, one period of faster growth. A novel pattern of regular cycles, composed of 7–10 lighter increments followed by a darker one, was found in the medium-anterior region of the RSS. Differences were found in the growth rate and size reached at the same age between individuals from the Pacific and Atlantic sectors, which might be related with different environmental conditions between both capture sites. This study shows that lower beaks from predators’ stomachs can be used to study the age of Southern Ocean squids and that M. longimana hatches in all seasons, being available year round to predators that feed of this species.

Description: Climate change is expected to produce major effects across marine life, and cephalopods seem to benefit from these effects. Of these animals, squids exhibit the greatest levels of biomass and of a substantial importance for human consumption. To test the hypothesis that effects of climate change are beneficial for commercial squid, we used species distribution models on climate scenarios for the period between 2000 and 2014, as well as the years 2050 and 2100 (RCP [representative concentration pathway] 2.6, 4.5, 6.0, and 8.5; CMIP5). Our results suggest that consequences of climate change scenarios are species specific. In the North Pacific and Northwest Atlantic, habitat suitability may increase (from + 0.83% [Doryteuthis pealeii] to + 8.77% increase [Illex illecebrosus]), while the habitat of other species is predicted to decrease (from − 1.03% [Doryteuthis opalescens] to -15.04% decrease [Loligo reynaudii]). Increases in habitat suitability occurred mostly at higher latitudes, while suitable habitat decrease was predicted for the tropical regions. Stronger changes were attained with the harsher emission scenarios. In the future, as a result of warming of the Arctic, squid habitat may increase along both coasts of North America. In the Southern Hemisphere, squids may lose habitat with no poleward habitat alternatives to move into. Contrary to our hypothesis, commercial squid do not stand to benefit from climate change. Since these squid are an important food source for marine megafauna and humans, it is imperative that climate change biogeographic impacts are considered for a sustainable management of this important group of molluscs.

Description: Climate change could shift the impacts of biological invasions on aquatic ecosystems. Sea freshening is an often-inconspicuous consequence of climatic change that may modify invasive alien species performance in enclosed seas. Several gammarid crustaceans have been particularly successful aliens across fresh, brackish, and marine waters. Here, we use comparative functional responses (feeding rates across resource densities) to examine the ecological impacts of an invasive alien (Gammarus tigrinus) and native (Gammarus locusta) gammarid, present in the Baltic Sea, under three different salinity regimes (14, 10, 6) toward larval chironomid prey. Feeding rates differed between the two species, but these differences depended on salinity, whereby at the lowest salinities, the invasive alien species showed significantly improved performance compared to the native species. Both gammarids exhibited hyperbolic Type II functional responses, with attack rates similar across salinity regimes. Handling times were significantly shortened, and maximum feeding rates heightened, in the alien under sea freshening scenarios compared to the native. These results have implications for enclosed sea systems, where projected freshening could shift the performance advantage toward invasive alien species over natives, thereby exacerbating their ecological impacts.

Description: The habitat quality of the littoral zone is of key importance for almost all lentic fish species. In anthropogenically created gravel pit lakes, the littoral zone is often structurally homogenized with limited fish habitats. We supplemented deadwood brush piles in the littoral zone of eight gravel pit lakes and investigated the diurnal and seasonal use of this and other typical microhabitats by six dominant fish species. Shoreline habitats were sampled using point abundance electrofishing during day and night in all four seasons, and patterns of fish abundance were compared amongst unstructured littoral habitats, emerged macrophytes and brush piles. We caught a total of 14,458 specimens from 15 species in the gravel pit lakes. Complex shoreline structures were used by all fish species that we examined, especially during daytime, whilst the use of unstructured habitats was highest during night. The newly added brush piles constituted suitable microhabitats for selected fish species, perch (Perca fluviatilis), roach (Rutilus rutilus) and pike (Esox lucius), particularly during winter. Supplemented deadwood provides suitable fish habitat in gravel pit lakes and may to some degree compensate for the loss of submerged macrophytes in winter by offering refuge and foraging habitat for selected fish species.

Description: We provide a sequence of analysis-ready optical underwater images from the Clarion-Clipperton Zone (CCZ) of the Pacific Ocean. The images were originally recorded using a towed camera sledge that photographed a seabed covered with polymetallic manganese-nodules, at an average water depth of 4,250 meters. The original degradation in visual quality and inconsistent scale among individual raw images due to different altitude implies that they are not scientifically comparable in their original form. Here, we present analysis-ready images that have already been pre-processed to account for this degradation. We also provide accompanying metadata for each image, which includes their geographic coordinates, depth of the seafloor, absolute scale (cm/pixel), and seafloor habitat class obtained from a previous study. The provided images are thus directly usable by the marine scientific community e.g., to train machine learning models for seafloor substrate classification and megafauna detection.

Description: Deoxygenation of the ocean has been occurring over the last half century, particularly in poorly ventilated coastal waters. In coastal and estuarine environments, both the water column and sediments play key roles in controlling oxygen variability. In this study, we focus on controls of oxygen concentration in Bedford Basin (BB), a 70 m deep, seasonally hypoxic semi-enclosed fjord on the West Atlantic coast in Nova Scotia. The basin is connected to the Scotian Shelf via a narrow 20 m deep sill that restricts the resupply of bottom water. Hypoxia was recorded seasonally in 2018, 2019 and 2021 with minimum oxygen concentration of 5, 6.7 and 2.7 μM, respectively. Using a 1-D benthic-pelagic coupled model we investigate oxygen consumption and resupply processes during these years. The model was constrained with weekly water column measurements of temperature, salinity, chlorophyll-a fluorescence and dissolved oxygen from a monitoring station in the central basin together with seasonal measurements of benthic diffusive oxygen uptake. Our model suggested that 29-81%, and up to 36% of bottom water re-oxygenation occurred during the winter mixing period and through summer/fall intrusions of Scotian Shelf water, respectively. Occasional shelf water intrusions occurred rapidly, on a timescale of a few hours, and delivered equivalent amounts of oxygen as winter mixing and were sufficient to end bottom water hypoxia. Collectively, these mechanisms supplied the majority of the oxygen delivered to the bottom water. Oxygen supply to bottom waters during periods of water column stratification accounted for 19-36% of the annual flux. The mean benthic uptake was 12 ± 8 mmol m -2 d -1 and contributed ~20% of the total oxygen consumption below the sill depth. In 2021, sea surface temperature (SST) was unusually high and likely resulted in 50% less bottom water oxygenation compared to 2018 and 2019 due to increased stratification; SST in BB was found to be increasing at a rate of 0.11 ± 0.02 °C/year. Climate control on water column stratification are discussed and numerical experiments are used to compare the effects of different water column mixing scenarios on bottom water oxygenation.

Description: As alien invasive species are a key driver of biodiversity loss, understanding patterns of rapidly changing global species compositions depends upon knowledge of invasive species population dynamics and trends at large scales. Within this context, the Ponto-Caspian region is among the most notable donor regions for aquatic invasive species in Europe. Using macroinvertebrate time series collected over 52 years (1968–2020) at 265 sites across 11 central and western European countries, we examined the occurrences, invasion rates, and abundances of freshwater Ponto-Caspian fauna. We examined whether: (i) successive Ponto-Caspian invasions follow a consistent pattern of composition pioneered by the same species, and (ii) Ponto-Caspian invasion accelerates subsequent invasion rates. In our dataset, Ponto-Caspian macroinvertebrates increased from two species in 1972 to 29 species in 2012. This trend was parallelled by a non-significant increasing trend in the abundances of Ponto-Caspian taxa. Trends in Ponto-Caspian invader richness increased significantly over time. We found a relatively uniform distribution of Ponto-Caspian macroinvertebrates across Europe without any relation to the distance to their native region. The Ponto-Caspian species that arrived first were often bivalves (46.5% of cases), particularly Dreissena polymorpha, followed secondarily by amphipods (83.8%; primarily Chelicorophium curvispinum and Dikerogammarus villosus). The time between consecutive invasions decreased significantly at our coarse regional scale, suggesting that previous alien establishments may facilitate invasions of subsequent taxa. Should alien species continue to translocate from the Ponto-Caspian region, our results suggest a high potential for their future invasion success highly connected central and western European waters. However, each species’ population may decline after an initial ‘boom’ phase or after the arrival of new invasive species, resulting in different alien species dominating over time.

Description: In the last three decades, quantitative approaches that rely on organism traits instead of taxonomy have advanced different fields of ecological research through establishing the mechanistic links between environmental drivers, functional traits, and ecosystem functions. A research subfield where trait-based approaches have been frequently used but poorly synthesized is the ecology of seagrasses; marine angiosperms that colonized the ocean 100M YA and today make up productive yet threatened coastal ecosystems globally. Here, we compiled a comprehensive trait-based response-effect framework (TBF) which builds on previous concepts and ideas, including the use of traits for the study of community assembly processes, from dispersal and response to abiotic and biotic factors, to ecosystem function and service provision. We then apply this framework to the global seagrass literature, using a systematic review to identify the strengths, gaps, and opportunities of the field. Seagrass trait research has mostly focused on the effect of environmental drivers on traits, i.e., “environmental filtering” (72%), whereas links between traits and functions are less common (26.9%). Despite the richness of trait-based data available, concepts related to TBFs are rare in the seagrass literature (15% of studies), including the relative importance of neutral and niche assembly processes, or the influence of trait dominance or complementarity in ecosystem function provision. These knowledge gaps indicate ample potential for further research, highlighting the need to understand the links between the unique traits of seagrasses and the ecosystem services they provide.

Description: Atlantic decadal-to-bidecadal variability (ADV) is described from a multimillennial control integration of a version of the Kiel Climate Model (KCM). The KCM’s ADV is the second most energetic mode of long-term North Atlantic variability in that simulation, whereas the Atlantic multidecadal variability (AMV) is the leading mode that has been described in a previous study. The KCM’s ADV can be regarded as a mixed oceanic gyre-overturning circulation mode that is forced by the North Atlantic Oscillation. The extratropical North Atlantic sea surface temperature (SST) anomalies associated with the model’s ADV initially exhibit a tripolar structure in the meridional direction, which is linked to the gyre circulation. After some years, the SST-anomaly pattern turns into a monopolar pattern located in the subpolar North Atlantic. This transition is related to the overturning circulation. The AMV and the ADV co-exist and share some similarities. Both modes of variability rely on the upper-ocean heat transport into the subpolar North Atlantic. They differ in the importance of the gyre and overturning circulations. In the ADV, gyre and overturning-heat transports into the subpolar North Atlantic are equally important in contrast to the AMV where the overturning contribution dominates.

Description: The deep-sea mining industry is currently at a point where large-sale, commercial polymetallic nodule exploitation is becoming a more realistic scenario. At the same time, certain aspects such as the spatiotemporal scale of impacts, sediment plume dispersion and the disturbance-related biological responses remain highly uncertain. In this paper, findings from a small-scale seabed disturbance experiment in the German contract area (Clarion-Clipperton Zone, CCZ) are described, with a focus on the soft-sediment ecosystem component. Despite the limited spatial scale of the induced disturbance on the seafloor, this experiment allowed us to evaluate how short-term (〈 1 month) soft-sediment changes can be assessed based on sediment characteristics (grain size, nutrients and pigments) and metazoan meiofaunal communities (morphological and metabarcoding analyses). Furthermore, we show how benthic measurements can be combined with numerical modelling of sediment transport to enhance our understanding of meiofaunal responses to increased sedimentation levels. The lessons learned within this study highlight the major issues of current deep-sea mining-related ecological research such as deficient baseline knowledge, unrepresentative impact intensity of mining simulations and challenges associated with sampling trade-offs (e.g., replication).

Description: The Clarion Clipperton Fracture Zone (CCZ) in the northeast Pacific is a heterogeneous deep-sea environment, featuring abyssal plains as well as multiple seamounts and abyssal hills (bathymetric elevations) that harbour a highly diverse megabenthic fauna. Based on the analysis of seafloor photographic transects that were taken from elevated areas downslope into the abyssal plains in the eastern CCZ, a similar distribution of habitats was observed on five different bathymetric elevations including abyssal hills as well as the foothills of two seamounts. Rock outcrops occur at the summits, surrounded by an area with varying coverage and size of polymetallic nodules, which were divided into two different habitats characterized by large and small nodules, respectively, and followed by nodule-free sediments. Megafauna composition, density and diversity varies across these habitats. While density is the highest in areas with rock outcrops (1.4 individuals per m 2 ), the biodiversity is the highest when regarding all of the habitats combined. Regarded individually, nodule-covered areas are the most diverse, whereas sediment areas without hard substratum, i.e. nodule free sediments, show the lowest biodiversity and the lowest density (0.2 individuals per m 2 ). The multinomial species classification method (CLAM) shows that most of the observed megafauna morphotypes have to be regarded as rare. The large differences between the megafaunal communities at bathymetric elevations and the abyssal plain reported from previous studies might partly be explained by the multiplicity of habitats. This high heterogeneity can lead to a more diversified community at elevations, although most habitats can also be observed in the abyssal plain.

Description: The study of marine food web models has increased during the last years, but input data of important groups such as cephalopods are missing sometimes which restricts the quality of the model results. Cephalopods feed on a variety of preys, ranging from small crustaceans to large commercially important fish species. In turn, they are taken by larger invertebrates, fish, cephalopods, marine mammals and seabirds, which emphasizes their important role in various marine food webs. Our study presents stomach content analyses of various cephalopod species from the North Sea and describes their general feeding trends. The results further support the inclusion of cephalopods as predators into food web models to increase our knowledge of the North Sea ecosystem and to improve its management. Our data in combination with observed increasing biomasses of North Sea cephalopods suggest that the impact of cephalopods in the North Sea food web has increased and that large-sized cephalopods have become more important as predators for commercially exploited fish species during recent years.

Description: Background: Animals are expected to adjust their social behaviour to cope with challenges in their environment. Therefore, for fish populations in temperate regions with seasonal and daily environmental oscillations, characteristic rhythms of social relationships should be pronounced. To date, most research concerning fish social networks and biorhythms has occurred in artificial laboratory environments or over confined temporal scales of days to weeks. Little is known about the social networks of wild, freely roaming fish, including how seasonal and diurnal rhythms modulate social networks over the course of a full year. The advent of high-resolution acoustic telemetry enables us to quantify detailed social interactions in the wild over time-scales sufficient to examine seasonal rhythms at whole-ecosystems scales. Our objective was to explore the rhythms of social interactions in a social fish population at various time-scales over one full year in the wild by examining high-resolution snapshots of a dynamic social network. Methods: To that end, we tracked the behaviour of 36 adult common carp, Cyprinus carpio, in a 25 ha lake and constructed temporal social networks among individuals across various time-scales, where social interactions were defined by proximity. We compared the network structure to a temporally shuffled null model to examine the importance of social attraction, and checked for persistent characteristic groups over time. Results: The clustering within the carp social network tended to be more pronounced during daytime than nighttime throughout the year. Social attraction, particularly during daytime, was a key driver for interactions. Shoaling behavior substantially increased during daytime in the wintertime, whereas in summer carp interacted less frequently, but the interaction duration increased. Therefore, smaller, characteristic groups were more common in the summer months and during nighttime, where the social memory of carp lasted up to two weeks. Conclusions: We conclude that social relationships of carp change diurnally and seasonally. These patterns were likely driven by predator avoidance, seasonal shifts in lake temperature, visibility, forage availability and the presence of anoxic zones. The techniques we employed can be applied generally to high-resolution biotelemetry data to reveal social structures across other fish species at ecologically realistic scales.

Description: Biological nitrogen fixation is a key process balancing the loss of combined nitrogen in the marine nitrogen cycle. Its relevance in upwelling or high nutrient regions is still unclear, with the few available studies in these regions of the ocean reporting rates that vary widely from below detection limit to 〉 100 nmol N L−1 d−1. In the eastern tropical Atlantic Ocean, two open ocean upwelling systems are active in boreal summer. One is the seasonal equatorial upwelling, where the residual phosphorus associated with aged upwelled waters is suggested to enhance nitrogen fixation in this season. The other is the Guinea Dome, a thermal upwelling dome. We conducted two surveys along 23° W across the Guinea Dome and the Equator from 15° N to 5° S in September 2015 and August–September 2016 with high latitudinal resolution (20–60 nm between stations). The abundance of Trichodesmium colonies was characterized by an Underwater Vision Profiler 5 and the total biological nitrogen fixation in the euphotic layer was measured using the 15N2 technique. The highest abundances of Trichodesmium colonies were found in the area of the Guinea Dome (9°–15° N) with a maximum of 3 colonies L−1 near the surface. By contrast, colonies were almost absent in the Equatorial band between 2° N and 5° S. The highest nitrogen fixation rate was measured at the northern edge of the Guinea Dome in 2016 (ca. 31 nmol N L−1 d−1). In this region, where diazotrophs thrived on a sufficient supply of both phosphorus and iron, a patchy distribution was unveiled by our increased spatial resolution scheme. In the Equatorial band, rates were considerably lower, ranging from below detection limit to ca. 4 nmol N L−1 d−1, with a clear difference in magnitude between 2015 (rates close to zero) and 2016 (average rates around 2 nmol N L−1 d−1). This difference seemed triggered by a contrasting supply of phosphorus between years. Our study stresses the importance of surveys with sampling at fine-scale spatial resolution, and shows unexpected high variability in the rates of nitrogen fixation in the Guinea Dome, a region where diazotrophy is a significant process supplying new nitrogen into the euphotic layer.

Description: While most coastal communities are expected to, or have been, negatively impacted by climate change, cephalopods have generally thrived with shifting ocean conditions. However, whilst benefitting from the same physiological flexibility that characterizes cephalopods in general, cuttlefish have depth constraints imposed by the presence of a cuttlebone and are limited to specific locations by their particularly low vagility. To evaluate the potential effects of marine climate change on cuttlefish, Species Distribution Models (SDM) were applied to nine species of genus Sepiidae to assess potential changes to their future distribution (2050 and 2100), under four representative concentration pathway (RCP) scenarios (i.e., RCP 2.6, 4.5, 6.0, and 8.5; CMIP5). We show that future cuttlefish habitat suitability and distribution will potentially decrease. The species with the most extreme impacts, Doratosepion braggi (Verco, 1907), was observed to decline as much as 30.77% in average habitat suitability (from present 55.26% to 24.48% at RCP 8.5 in 2100), to Sepia officinalis Linnaeus, 1758 with a low maximum decrease of 1.64% in average habitat suitability (from present 59.62% to 57.98% at RCP 8.5 in 2100). Increases in habitat suitability were projected mostly at higher latitudes, while habitat decrease was predicted for the tropical regions and lower latitudinal limits of species’ distributions. As their habitats decrease in terms of habitat suitability, cuttlefish may not benefit from future changes in climate. Additionally, as potential “sea canaries” for coastal ecosystems, we may see many species and habitats from these systems affected by climate change, particularly in tropical regions.

Description: The topographic fabric of the rift valley floor has been analyzed using the multibeam echosounder data obtained by the autonomous underwater vehicle (AUV) Abyss at two locations over a short segment of the slow-spreading Central Indian Ridge between 10°18′ and 10°57′S. The region is influenced by hydrothermal venting in the near vicinity. Two AUV dives D51 and D52 were performed over this segment at two locations that are 30 km apart and covered 5 km2 and 8 km2 seafloor area, respectively. The dive D51 covered the off-axis part of the rift valley floor in the middle part of the segment, and the dive D52 is located near to the non-transform discontinuity that covered the terminal part of an oceanic core complex (OCC). High-resolution seafloor topography as revealed by the AUV-mounted multibeam echosounder system brought out several micro-bathymetric fabric features such as a lava lake, a cratered volcano, an OCC, and the foot wall volcanic complex at the distal part of the OCC. The valley floor imaged in the D51 is marked by a lava flow encompassing an area of 1 km2 and a volcano in the NE corner. The volcano has a diameter of about 800 m with an elevation of about 200 m from the adjacent seafloor, and the partially mapped volcano crater has a relief of about 60 m. A prominent linear fissure running parallel to the ridge axis has been identified; this feature joins with the volcano. Analysis of AUV-mounted CTD data indicated three distinct temperature spikes ranging 0.009 to 0.013 °C in the region of dive D51. The observed temperature spikes appear to be related to the linear fissure on the seafloor and probably represent leaky venting of fluids from the fissure. With respect to the dive D52, the foot wall volcanic features associated with the OCC are prominent. The volcanic seafloor feature covered an area of 3.45 km2 and is conspicuous with rugged topographic fabric at the base of the OCC. These inferences and the morphotectonics of the rift valley floor as revealed by the AUV data suggest moderate hydrothermal venting in this segment of the slow-spreading Central Indian Ridge.

Description: We contend that ocean turbulent fluxes should be included in the list of Essential Ocean Variables (EOVs) created by the Global Ocean Observing System. This list aims to identify variables that are essential to observe to inform policy and maintain a healthy and resilient ocean. Diapycnal turbulent fluxes quantify the rates of exchange of tracers (such as temperature, salinity, density or nutrients, all of which are already EOVs) across a density layer. Measuring them is necessary to close the tracer concentration budgets of these quantities. Measuring turbulent fluxes of buoyancy (Jb), heat (Jq), salinity (JS) or any other tracer requires either synchronous microscale (a few centimeters) measurements of both the vector velocity and the scalar (e.g., temperature) to produce time series of the highly correlated perturbations of the two variables, or microscale measurements of turbulent dissipation rates of kinetic energy (ϵ) and of thermal/salinity/tracer variance (χ), from which fluxes can be derived. Unlike isopycnal turbulent fluxes, which are dominated by the mesoscale (tens of kilometers), microscale diapycnal fluxes cannot be derived as the product of existing EOVs, but rather require observations at the appropriate scales. The instrumentation, standardization of measurement practices, and data coordination of turbulence observations have advanced greatly in the past decade and are becoming increasingly robust. With more routine measurements, we can begin to unravel the relationships between physical mixing processes and ecosystem health. In addition to laying out the scientific relevance of the turbulent diapycnal fluxes, this review also compiles the current developments steering the community toward such routine measurements, strengthening the case for registering the turbulent diapycnal fluxes as an pilot Essential Ocean Variable.

Description: The Southern Ocean, the ocean encircling Antarctica, has been described by explorers as cold, empty, and dangerous. Despite this, it is a paradise for tiny algae called diatoms that are crucial players in the regulation of our climate. Why are these tiny organisms so happy in this cold and far away ocean? Diatoms have a solid shell made of a glass-like material called silica, so they need to find silicon in surface waters to build it. The Southern Ocean is the perfect place for diatoms because it is full of silicon compared to the other oceans. This is due to a special phenomenon called the silicon pump, which makes the Southern Ocean a giant trap for silicon. In this article, we point out the central role of the Southern Ocean in the regulation of Earth’s climate and how it controls the distribution of silicon and the wellbeing of diatoms in Antarctic waters.

Description: Ocean artificial upwelling has been suggested to boost primary production and increase harvestable resources such as fish. Yet, for this ecosystem-based approach to work, an effective energy transfer up the food web is required. Here, we studied the trophic role of microzooplankton under artificial upwelling via biomass and community composition as well as grazing rates on phytoplankton. Using mesocosms in the oligotrophic ocean, we supplied nutrient-rich deep water at varying intensities (low to high) and addition modes (a Singular large pulse or smaller Recurring pulses). Deep-water fertilization created a diatom-dominated bloom that scaled with the amount of inorganic nutrients added, but also Synechococcus -like cells, picoeukaryotes and nanophytoplankton increased in abundance with added nutrients. After 30 days, towards the end of the experiment, coccolithophores bloomed under recurring upwelling of high intensity. Across all upwelling scenarios, the microzooplankton community was dominated by ciliates, dinoflagellates (mixo- and heterotrophic) and radiolarians. Under the highest upwelling intensity, the average grazing rates of Synechococcus -like cells, picoeukaryotes and nanophytoplankton by microzooplankton were 0.35 d -1 ± 0.18 (SD), 0.09 d -1 ± 0.12 (SD), and 0.11 d -1 ± 0.13 (SD), respectively. There was little temporal variation in grazing of nanophytoplankton but grazing of Synechococcus -like cells and picoeukaryotes were more variable. There were positive correlations between abundance of these groups and grazing rates, suggesting a response in the microzooplankton community to prey availability. The average phytoplankton to microzooplankton ratio (biovolume) increased with added deep water, and this increase was highest in the Singular treatment, reaching ~30 (m 3 m -3 ), whereas the phytoplankton to total zooplankton biomass ratio (weight) increased from ~1 under low upwelling to ~6 (g g -1 ) in the highest upwelling but without a difference between the Singular and the Recurring mode. Several smaller, recurring upwelling events increased the importance of microzooplankton compared with one large pulse of deep water. Our results demonstrate that microzooplankton would be an important component for trophic transfer if artificial upwelling would be carried out at scale in the oligotrophic ocean.

Description: We report two Arctic species of incirrate octopods new to science. One is formally described here as Muusoctopus aegir Golikov, Gudmundsson & Sabirov sp. nov. while the other, Muusoctopus sp. 1, is not formally described due to a limited number of samples (all are immature individuals). These two species differ from each other, and from other Muusoctopus, especially in: 1) absence of stylets (in M. aegir sp. nov.); 2) proportions of mantle and head; 3) funnel organ morphology (W-shaped with medial and marginal limbs of equal length in M. aegir sp. nov., or medial are slightly longer; V V-shaped with medial limbs slightly longer and broader than marginal in Muusoctopus sp. 1); 4) sucker and gill lamellae counts; 5) relative arm length and sucker diameter; and 6) male reproductive system relative size and morphology. Species of Muusoctopus now comprise four of 12 known Arctic cephalopods. Additionally, this study provides: a) new data on the morphology and reproductive biology of M. johnsonianus and M. sibiricus, and a diagnosis of M. sibiricus; b) the equations to estimate mantle length and body mass from beak measurements of M. aegir sp. nov. and M. johnsonianus; c) a cytochrome c oxidase subunit I gene barcode for M. sibiricus; d) new data on the ecology and distribution of all studied species; and e) a data table for the identification of northern North Atlantic and Arctic species of Muusoctopus.

Description: The Clarion Clipperton Zone (CCZ) in the Northeast Pacific Ocean holds the largest deposits of polymetallic nodules at abyssal depths. These nodules are rock formations containing valuable metals and minerals targeted for mining. They further provide diverse habitat for a range of deep-sea species. Little is known so far on the taxonomy, natural history and biogeography of these deep-sea animals which is vital for accurate assessment of the risk of species extinctions from large-scale mining. One of the most abundant megafaunal groups in the CCZ is the Ophiuroidea (brittle stars), of which Ophiotholia is one of the more abundant genera found in the area. The genus Ophiotholia has a world-wide distribution and currently holds six species.

Description: Benthic foraminifera cannot be sampled adequately using a single device. Smaller taxa are best collected using multicorers, the larger with box corers, but towed devices (dredges, trawls and epibenthic sledges) also retain many larger species. Here, we describe macrofaunal (>300 µm) foraminiferal assemblages obtained using an epibenthic sledge (EBS) in the Clarion-Clipperton Zone (eastern equatorial Pacific), a region hosting seafloor deposits of polymetallic nodules. Twelve EBS samples were collected in four areas licenced for exploration by the International Seabed Authority (ISA) to German, IOM, Belgium and French contractors, and to APEI-3, one of the protected Areas of Special Scientific Interest designated by the ISA. We recognised 280 morphospecies among 1954 specimens, with between 74 (IOM) and 121 (Belgium) in particular areas. Most (92.7%) were single-chambered monothalamids, of which 75 species (26.8%) belonged to the Komokioidea (‘komoki’), 47 (16.8%) to branched and unbranched tubes, 33 (11.8%) to chain-like and 32 (11.4%) to various ‘komoki-like’ forms. Fragments of megafaunal xenophyophores represented 21 species (7.50%), including Spiculammina delicata , previously reported only from the Russian area. Rarefaction curves and sample coverage completeness curves suggest that only a fraction of the macrofaunal foraminiferal diversity had been sampled. The occurrence of 71.8% of species in 1-2 of the 12 samples and 84.9% in 1-3 of the samples was a likely result of substantial undersampling. Dissimilarity in species composition between areas was very high: 64.2% (German vs IOM area) to 86.9% (German area vs APEI-3). Similarity within a single area was quite low: 29.1% (German) to 45.1% (IOM). In multidimensional scaling (MDS) plots, the APEI-3 area was clearly distinct in terms of faunal composition from all other areas, the French area somewhat separated from the German, IOM and Belgium areas, with the German and IOM samples being the most similar. These patterns may reflect the geographical separation of the French and APEI-3 areas and their location in deeper, more oligotrophic waters. Our study demonstrates that EBS samples from the eastern CCZ are a rich source of novel foraminiferal taxa, particularly light, easily resuspended komoki, providing a valuable perspective on foraminiferal biodiversity.

Description: Due to the increasing challenge of meeting human demands for metals from land-based resources, interest in extracting mineral ores from the deep sea has gained momentum in recent years. Targeted mining of deep-seabed minerals could have adverse effects on the associated ecosystems, but knowledge on the biological communities found there, their structure and functions is still limited. The focus of this study is to provide an overview on isopod crustaceans from the Clarion Clipperton Fracture Zone (CCFZ), an area well-known for its abundance of high-grade polymetallic nodules. Isopods generally comprise an important part of the macrofaunal communities of soft deep-sea sediments and indeed are one of the most dominant macrobenthic groups in the CCFZ. In this review, we have compiled all available data and information on isopod diversity and distribution in the CCFZ in a hybrid manner, which includes published data from the literature as well as the analysis of previously unpublished sources and newly collected data. Although isopods are one of the more prevalent and better-known groups of the CCFZ fauna, this study shows that it is still remarkably difficult to obtain a clear perception of isopod diversity and distribution, as well as the factors that could be responsible for the observed patterns. In many places, knowledge remains incomplete, which is largely due to the low sampling and taxonomic effort, non-standardised sample protocols and the limited taxonomic inter-calibration between studies. The latter is pivotal due to the high proportion of undescribed and presumably new species that typically occur there. An important starting point would therefore be to increase sampling effort and its spatial and temporal coverage in a standardised way, to intensify (integrative) taxonomic work as well as to facilitate sample and data exchange between scientists and contractors. These are fundamental requirements to improve our understanding of the biodiversity of isopods, but also of other faunal groups, in the CCFZ, before mining operations begin.

Description: Marine ecosystems, ranging from coastal seas and wetlands to the open ocean, accommodate a wealth of biological diversity from small microorganisms to large mammals. This biodiversity and its associated ecosystem function occurs across complex spatial and temporal scales and is not yet fully understood. Given the wide range of external pressures on the marine environment, this knowledge is crucial for enabling effective conservation measures and defining the limits of sustainable use. The development and application of omics-based approaches to biodiversity research has helped overcome hurdles, such as allowing the previously hidden community of microbial life to be identified, thereby enabling a holistic view of an entire ecosystem's biodiversity and functioning. The potential of omics-based approaches for marine ecosystems observation is enormous and their added value to ecosystem monitoring, management, and conservation is widely acknowledged. Despite these encouraging prospects, most omics-based studies are short-termed and typically cover only small spatial scales which therefore fail to include the full spatio-temporal complexity and dynamics of the system. To date, few attempts have been made to establish standardised, coordinated, broad scaled, and long-term omics observation networks. Here we outline the creation of an omics-based marine observation network at the European scale, the European Marine Omics Biodiversity Observation Network (EMO BON). We illustrate how linking multiple existing individual observation efforts increases the observational power in large-scale assessments of status and change in biodiversity in the oceans. Such large-scale observation efforts have the added value of cross-border cooperation, are characterised by shared costs through economies of scale, and produce structured, comparable data. The key components required to compile reference environmental datasets and how these should be linked are major challenges that we address.

Description: Anthropogenic carbon dioxide (CO2) levels are rising to alarming concentrations in earth’s atmosphere, causing adverse effects and global climate changes. In the last century, innovative research on CO2 reduction using chemical, photochemical, electrochemical and enzymatic approaches has been addressed. In particular, natural CO2 conversion serves as a model for many processes and extensive studies on microbes and enzymes regarding redox reactions involving CO2 have already been conducted. In this review we focus on the enzymatic conversion of CO2 to carbon monoxide (CO) as the chemical conversion downstream of CO production render CO particularly attractive as a key intermediate. We briefly discuss the different currently known natural autotrophic CO2 fixation pathways, focusing on the reversible reaction of CO2, two electrons and protons to CO and water, catalyzed by carbon monoxide dehydrogenases (CODHs). We then move on to classify the different type of CODHs, involved catalyzed chemical reactions and coupled metabolisms. Finally, we discuss applications of CODH enzymes in photochemical and electrochemical cells to harness CO2 from the environment transforming it into commodity chemicals.

Description: Ocean Census is a new Large-Scale Strategic Science Mission aimed at accelerating the discovery and description of marine species. This mission addresses the knowledge gap of the diversity and distribution of marine life whereby of an estimated 1 million to 2 million species of marine life between 75% to 90% remain undescribed to date. Without improved knowledge of marine biodiversity, tackling the decline and eventual extinction of many marine species will not be possible. The marine biota has evolved over 4 billion years and includes many branches of the tree of life that do not exist on land or in freshwater. Understanding what is in the ocean and where it lives is fundamental science, which is required to understand how the ocean works, the direct and indirect benefits it provides to society and how human impacts can be reduced and managed to ensure marine ecosystems remain healthy. We describe a strategy to accelerate the rate of ocean species discovery by: 1) employing consistent standards for digitisation of species data to broaden access to biodiversity knowledge and enabling cybertaxonomy; 2) establishing new working practices and adopting advanced technologies to accelerate taxonomy; 3) building the capacity of stakeholders to undertake taxonomic and biodiversity research and capacity development, especially targeted at low- and middle-income countries (LMICs) so they can better assess and manage life in their waters and contribute to global biodiversity knowledge; and 4) increasing observational coverage on dedicated expeditions. Ocean Census, is conceived as a global open network of scientists anchored by Biodiversity Centres in developed countries and LMICs. Through a collaborative approach, including co-production of science with LMICs, and by working with funding partners, Ocean Census will focus and grow current efforts to discover ocean life globally, and permanently transform our ability to document, describe and safeguard marine species.

Description: The role and conditions of liquid immiscibility or crystallization of sulfide phase during evolution of subduction-related magmas remains a debated topic, which bears relevance to the genesis of porphyry copper deposits and evolution of the continental crust. We studied rare volcanic rocks with inclusions of magmatic sulfides in olivine—the basalts of Medvezhya Mount in the Avachinsky group of volcanoes. The rocks belong to primitive (Mg# = 66 mol %) middle-K island-arc olivine basalts. Olivine with normal zoning predominates (~98%) among phenocrysts. The olivine compositions are typical for Kamchatka basalts, except for an unusual trend of increase of MnO content from 0.20 to 0.55 wt % and decrease of Fe/Mn from 60 to 35 with a change of olivine composition from Fo87.8 to Fo78.2. Olivine of this group contains numerous inclusions of spinel-group minerals varying in composition from chromium spinel to magnesian magnetite. Olivine phenocrysts with sulfide inclusions are characterized by the absence of or weak reverse zoning and reduced contents of Ca, Ni, Mn, Cr, and Al. The estimated crystallization temperatures are 1036–1241°C for olivine of the prevailing type and 1010–1062°C for sulfide-bearing olivine. The data suggest that crystallization of the main olivine population occurred under relatively shallow conditions and was accompanied by strong magma oxidation. On the contrary, the zoning pattern and compositional features of sulfide-bearing olivine suggest its xenogenic origin and the probable crystallization under deep-crustal conditions from low-temperature water-rich and/or low-Ca magmas. The results obtained confirm the possibility of saturation of oxidized island-arc magmas with sulfide phase at lower crustal conditions, but show that this process is rare and not typical for low-pressure crystallization stage.

Description: Subterranean estuaries are connective zones between inland aquifers and the open sea where terrestrial freshwater and circulating seawater mix and undergo major biogeochemical changes. They are biogeochemical reactors that modify groundwater chemistry prior to discharge into the sea. We propose that subterranean estuaries of high-energy beaches are particularly dynamic environments, where the effect of the dynamic boundary conditions propagates tens of meters into the subsurface, leading to strong spatio-temporal variability of geochemical conditions. We hypothesize that they form a unique habitat with an adapted microbial community unlike other typically more stable subsurface environments. So far, however, studies concerning subterranean estuaries of high-energy beaches have been rare and therefore their functioning, and their importance for coastal ecosystems, as well as for carbon, nutrient and trace element cycling, is little understood. We are addressing this knowledge gap within the interdisciplinary research project DynaDeep by studying the combined effect of surface (hydro- and morphodynamics) on subsurface processes (groundwater flow and transport, biogeochemical reactions, microbiology). A unique subterranean estuary observatory was established on the northern beach of the island of Spiekeroog facing the North Sea, serving as an exemplary high-energy research site and model system. It consists of fixed and permanent infrastructure such as a pole with measuring devices, multi-level groundwater wells and an electrode chain. This forms the base for autonomous measurements, regular repeated sampling, interdisciplinary field campaigns and experimental work, all of which are integrated via mathematical modelling to understand and quantify the functioning of the biogeochemical reactor. First results show that the DynaDeep observatory is collecting the intended spatially and temporally resolved morphological, sedimentological and biogeochemical data. Samples and data are further processed ex-situ and combined with experiments and modelling. Ultimately, DynaDeep aims at elucidating the global relevance of these common but overlooked environments.

Description: Außerschulische Lernorte wie Themenpfade, Geoparks, Weltkulturerbestätten, Museen und Schülerlabore an geowissenschaftlichen Forschungseinrichtungen sind von essenzieller Bedeutung für die Kommunikation geowissenschaftlicher Wissensbestände hinein in die Schulen und an die Öffentlichkeit. Das vorliegende Kapitel zeigt die Vielfalt der Angebote. An der Vermittlung interessierten Geowissenschaftlerinnen und Geowissenschaftlern können die Beschreibungen der Vermittlungsansätze als Anregung für eigene Projekte dienen. Lehrkräfte erhalten einen Überblick über außerschulische Lernorte, die sie mit ihren Lerngruppen aufsuchen können, und erfahren, was sie dort erwarten wird.

Description: Available information and potential data gaps for non-fish marine organisms (cnidarians, crustaceans, echinoderms, molluscs, sponges, mammals, reptiles, and seabirds) covered by the global database SeaLifeBase were reviewed for eight marine ecosystems (Adriatic Sea, Aegean Sea, Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea, western Mediterranean Sea, Levantine Sea) across European Seas. The review of the SeaLifeBase dataset, which is based on published literature, analyzed information coverage for eight biological characteristics (diet, fecundity, maturity, length-weight relationships, spawning, growth, lifespan, and natural mortality). These characteristics are required for the development of ecosystem and ecological models to evaluate the status of marine resources and related fisheries. Our analyses revealed that information regarding these biological characteristics in the literature was far from complete across all studied areas. The level of available information was nonetheless reasonably good for sea turtles and moderate for marine mammals in some areas (Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea and western Mediterranean Sea). Further, seven of the areas have well-studied species in terms of information coverage for biological characteristics of some commercial species whereas threatened species are generally not well studied. Across areas, the most well-studied species are the cephalopod common cuttlefish (Sepia officinalis) and the crustacean Norway lobster (Nephrops norvegicus). Overall, the information gap is narrowest for length-weight relationships followed by growth and maturity, and widest for fecundity and natural mortality. Based on these insights, we provide recommendations to prioritize species with insufficient or missing biological data that are common across the studied marine ecosystems and to address data deficiencies.

Description: Isolation and detection of microplastics (MP) in marine samples is extremely cost- and labor-intensive, limiting the speed and amount of data that can be collected. In the current work, we describe rapid measurement of net-collected MPs (net mesh size 300 µm) using a benchtop near-infrared hyperspectral imaging system during a research expedition to the subtropical North Atlantic gyre. Suspected plastic particles were identified microscopically and mounted on a black adhesive background. Particles were imaged with a Specim FX17 near-infrared linescan camera and a motorized stage. A particle mapping procedure was built on existing edge-finding algorithms and a polymer identification method developed using spectra from virgin polymer reference materials. This preliminary work focused on polyethylene, polypropylene, and polystyrene as they are less dense than seawater and therefore likely to be found floating in the open ocean. A total of 27 net tows sampled 2534 suspected MP particles that were imaged and analyzed at sea. Approximately 77.1% of particles were identified as polyethylene, followed by polypropylene (9.2%). A small fraction of polystyrene was detected only at one station. Approximately 13.6% of particles were either other plastic polymers or were natural materials visually misidentified as plastics. Particle size distributions for PE and PP particles with a length greater than 1 mm followed an approximate power law relationship with abundance. This method allowed at-sea, near real-time identification of MP polymer types and particle dimensions, and shows great promise for rapid field measurements of microplastics in net-collected samples.

Description: Abyssal plain communities rely on the overlying water column for a settling flux of organic matter. The origin and rate of this flux as well as the controls on its fine-scale spatial distribution following seafloor settlement are largely unquantified. This is particularly true across regions where anthropogenically-induced seafloor disturbance has occurred. Here, we observed, quantified and mapped a mass deposition event of gelatinous zooplankton carcasses (pyrosomes) in July-September 2015 across one such physically disturbed region in the Peru Basin polymetallic nodule province (4150 m). Seafloor in this area was disturbed with a plough harrow in 1989 (as part of the DISCOL experiment) causing troughs in the sediment. Other parts were disturbed with an epibenthic sled (EBS) during a cruise in 2015 resulting in steep-walled, U-shaped troughs. We investigated two hypotheses: a) gelatinous food falls contribute significantly to the abyssal plain carbon pump and b) physical seafloor disturbance influences abyssal distribution of organic matter. We combined optical and bathymetric seafloor observations, to analyze pyrosome distribution on seabeds with different levels of disturbance. 2954 pyrosome colonies and associated taxa were detected in 〉 14,000 seafloor images. The mean regional carbon (C) deposition associated with pyrosome carcasses was significant compared to the flux of particulate organic C (182 to 1543%), and the total respired benthic C flux in the DISCOL Experimental Area (39 to 184%). EBS-disturbed seafloor tracks contained 72 times more pyrosome-associated C than an undisturbed reference site, and up to 4 times more than an area disturbed in 1989. Deposited pyrosomes collected had a higher proportion of labile fatty acids compared to the sediment. We document the temporal and spatial extent of an abyssal food fall event with unprecedented detail and show that physical seafloor disturbance results in the accumulation of detrital material. Such accumulation may reduce oxygen availability and alter benthic community structure. Understanding both the relevance of large food falls and the fine scale topography of the seafloor, is necessary for impact assessment of technologies altering seafloor integrity (e.g. as a result of bottom-trawling or deep seabed mining) and may improve their management on a global scale.

Description: Previous studies indicated that the North Tropical Atlantic (NTA) SST can serve as a precursor for the El Niño–Southern Oscillation (ENSO) predictability and the connection of NTA-ENSO is modulated by the mid-high latitude atmospheric variability. Despite significant solar footprints being found in the North Atlantic and tropical Pacific separately, their role in the two basins’ connection is still missing. In this study, we systematically examined this point by using observational/reanalysis datasets and outputs of a pair of sensitivity experiments with and without solar forcings (SOL and NOSOL). In observations, DJF-mean NAO-like SLP anomalies have a linear covariation with the subsequent JJA-mean El Niño Modoki-like SST anomalies in the tropical Pacific in the following 1 year. This observed SLP-SST covariation shows up in the high solar activity (HS) subset and disappears in the low solar activity (LS) subset. In the HS years, positive NAO-like SLP anomalies are produced by the stronger solar-UV radiation through a “top-down” mechanism. These atmospheric anomalies can enhance the influence of the NTA on the tropical Pacific SST by triggering significant and more persistent subtropical teleconnections. Here we proposed an indirect possible mechanism that the solar-UV forcing can modulate the tropical Pacific SST variability via its impacts on the atmospheric anomalies over the North Atlantic region. However, based on the same analysis method, we found a different coupled mode of the SLP and SST anomalies in the modeling outputs. The SLP anomalies in the North Atlantic, with a triple pattern (negative SLP anomalies in the Pole and the NTA, positive SLP anomalies in the mid-latitude), have “lead-lag” covariations with the Eastern Pacific El Niño-like SST anomalies in both the SOL and NOSOL. Although the impact of the solar activity is found in the North Atlantic and the tropical Pacific respectively in the SOL, no solar effect is involved in the simulated SLP-SST coupled mode.

Description: Volcanoes are sources of numerous threats including lava flows, pyroclastic flows, ash dispersal and landslides or sector collapses. In addition to these commonly known volcanic hazards, volcano-induced tsunamis can occur in the marine environment, introducing a major hazard that can affect populations located far away from the volcanoes. Existing tsunami warning systems generally do not account for volcano-generated tsunamis, due to the multiple source mechanisms that can cause such tsunamis, a limited understanding of precursory signals for these events, and the need for local detection rather than remote sensing. Among these source mechanisms of volcanic tsunamis, sector and lateral collapses are at the high risk-low frequency extreme of risk matrices. Marine volcanoes grow in specific environments, with factors like marine clays, constant full saturation, sediment transport and remobilization, interaction with ocean dynamics, and sea level changes that may impact edifice stability in distinct ways. The majority of historically documented marine volcano collapses occurred at erupting volcanoes, suggesting that eruptions could serve as a remotely detectable warning signal for collapses. However, careful examination of temporal sequences of these examples reveals that collapses do not always follow eruptions. Consequently, there is a need for identifying other, more robust precursors to volcano collapse, in particular in the marine environment, where the consequences of collapses may be widespread.

Description: Digital elevation models (DEMs) are crucial in natural hazard assessments, as they often present the only comprehensive information. While satellites deliver remote sensing information of the land surface of up to 2m resolution, only 25% of the seafloor is mapped with a minimum resolution of 400m. The acquisition of high-resolution bathymetry requires hydroacoustic surveys by research vessels or autonomous vehicles, which is time-consuming and expensive. Predicted bathymetry from satellite altimetry, on the other hand, is widely available but has a significantly lower spatial resolution and high uncertainties in elevation, especially in shallow waters. The research on volcanic islands as a source of both volcanic as well as marine hazards such as tsunamis, is greatly limited by the lack of high-resolution bathymetry. Here we compare 24 geomorphometric parameters of 47 volcanic islands derived from a) the comprehensive bathymetric data of the General Bathymetric Chart of the Ocean (GEBCO) and b) high-resolution (〈 250m), ship-based bathymetry. Out of 24 parameters tested, 20 show 〈 ± 2.5% median deviation, and quartiles 〈 ± 10%. Parameters describing the size of a volcanic island are the most robust and slope parameters show the greatest deviations. With this benchmark, we will be able to increase geomorphometric investigations to volcanic islands where little or no high-resolution bathymetry data is available.

Description: In order to expand the knowledge of microbial ecosystems from deep-sea hydrothermal vent systems located on the Central and South-East Indian Ridge, we sampled hydrothermal fluids, massive sulfides, ambient water and sediments of six distinct vent fields. Most of these vent sites were only recently discovered in the course of the German exploration program for massive sulfide deposits and no previous studies of the respective microbial communities exist. Apart from typically vent-associated chemosynthetic members of the orders Campylobacterales , Mariprofundales , and Thiomicrospirales , high numbers of uncultured and unspecified Bacteria were identified via 16S rRNA gene analyses in hydrothermal fluid and massive sulfide samples. The sampled sediments however, were characterized by an overall lack of chemosynthetic Bacteria and the presence of high proportions of low abundant bacterial groups. The archaeal communities were generally less diverse and mostly dominated by members of Nitrosopumilales and Woesearchaeales , partly exhibiting high proportions of unassigned Archaea. Correlations with environmental parameters were primarily observed for sediment communities and for microbial species (associated with the nitrogen cycle) in samples from a recently identified vent field, which was geochemically distinct from all other sampled sites. Enrichment cultures of diffuse fluids demonstrated a great potential for hydrogen oxidation coupled to the reduction of various electron-acceptors with high abundances of Hydrogenovibrio and Sulfurimonas species. Overall, given the large number of currently uncultured and unspecified microorganisms identified in the vent communities, their respective metabolic traits, ecosystem functions and mediated biogeochemical processes have still to be resolved for estimating consequences of potential environmental disturbances by future mining activities.

Description: The mid-ocean rift in the Red Sea is one of the youngest rifting systems on Earth. Only recently, state-of-the-art methods and modern deep-sea instruments have been used to explore this young and unique volcanic system. During the first autonomous underwater vehicle surveys of the Red Sea Rift in Spring 2022, we collected multibeam bathymetry, backscatter, sub-bottom profiler data, and water column data over a 9 km long ridge segment in the Hadarba Deep between 22.49°N and 22.56°N to investigate the volcano-tectonic processes of this ultra-slow spreading segment (12 mm/year spreading rate). The high-resolution hydroacoustic data was used to (1) delineate and quantify the geometry of tectonic structures and individual lava flows, (2) define lava flow morphology and eruption style, (3) estimate relative ages of flows and features, and (4) retrace the evolution of the volcanic activity. In addition, the geochemistry of several young lava flows provides information on the relation between the different magma that supply these eruptions. About 90 eruptive units with variable sedimentary cover have been identified within the 43 km 2 mapped region. The oldest lava flows are buried under 3 to 4.2 m of sediment, indicating ages of up to ~30 ka based on average sedimentation rate estimates (~14 cm/ka), while the youngest eruptions are covered by〈10 cm of sediment, and are thus younger than 700 years. Three volcanic phases have been identified based on changes in flow morphology and distribution, and tectonic pattern. All three axial phases have an average eruptive frequency of ~100-250 years. The segment displays an overall low tectonic extension (〈10% of the total extension) and low vertical offset. Our geomorphological maps, analyses, and statistics reveal a moderately faulted, ultra-slow spreading MOR segment in the Red Sea with a surprisingly large amount of magmatic extension, implying that the segment has been underlined by a large magma supply for at least 15 ka. All these observations provide valuable implications for the formation history of the Red Sea Rift and the formation of ultra-slow spreading crust.