Recent  

Understanding species richness patterns remains a challenge for biodiversity management. We estimated fish species richness over a large coastal salinity gradient (3–32), with a method that allowed comparing data from various sources. Species richness was threefold higher at high vs. low salinity, and salinity influenced species’ habitat preference, mobility and feeding type. If climate change causes freshening of the Baltic Sea, further shifts along the identified patterns may be expected.

Estuaries can significantly alter nutrient loads before reaching coastal waters. Our study of the heavily managed Ems estuary reveals three zones of nitrogen turnover along the estuary. Overall, the Ems acted as a nitrate sink with water-column denitrification in the most upstream hyper-turbid part, nitrate production in the Middle Reaches and mixing/nitrate uptake in the North Sea. Suspended particulate matter was the overarching control on nitrogen cycling in the hyper-turbid estuary.

The impact of anthropogenic climate change on the biological production of phytoplankton in the ocean is a cause for concern because its evolution could affect the response of marine ecosystems to climate change. Here, we identify biological N-fixation, and its response to future climate change, as a key process in shaping the future evolution of marine phytoplankton production. Our results show that further study of how this nitrogen fixation responds to environmental change is essential.

We investigate the impact of the eddies and of the Amazon River water on the CO₂ air-sea fluxes to better characterize the ocean carbon sink in winter 2020. The region is a strong CO₂ sink, underestimated in climatology by a factor 10 due to a lack of data and understanding of the processes responsible for the variability of ocean carbon parameters. The CO₂ absorption is mainly driven by freshwater from the amazon entrained away from the coast by eddies, and by the winter seasonal cooling.

This work has described the variability in sedimentary organic matter composition through a broad sampling campaign of marine mudflats at the regional scale (Brittany Region), and made the link with sediment potential biodegradability and nutrient release. In these coastal ecosystems affected by the eutrophication, the potential impact of human activities on the nutrient dynamics at the sediment-water interface was highlighted.

We use in-situ high temporal measurements of dissolved inorganic carbon and atmospheric parameters at the air-sea interface to analyze the initiation of the phytoplankton bloom identified as net rate of biological carbon uptake in the Mediterranean Sea. The shift from wind-driven mixing to buoyancy-driven creates the conditions for blooms to begin. Active mixing at the air-sea interface lead to the onset of the phytoplankton bloom due to the relaxation of wind speed following storms.

The concentration of the trace metal barium (Ba) in coastal seawater is a function of continental input, such as by riverine discharge. Our geochemical records of the severely hot and dry year 2018, and following wet year 2019, reveal that prolonged drought imprints with exceptionally low Ba concentrations in benthic foraminiferal calcium carbonates of coastal sediments. This highlights the potential of benthic Ba/Ca to trace past climate extremes and variability in coastal marine records.

Spring bloom observations in oceanic waters of phytoplankton biomass accumulating in winter, when light still limits growth, are ascribed to grazing release as the mixed layer deepens. However, in coastal areas, it is not clear whether winter accumulation can occur without this deepening. Using 21 years of weekly data, we found that in the Scottish coastal North Sea, the seasonal increase in winter light triggers the accumulation of phytoplankton biomass when light limitation is strongest.

Satellite observations help interpret station measurements of local carbon, water, and energy exchange between the land surface and the atmosphere, and are indispensable for simulations of the same in land surface models and their evaluation. We propose generalisable and efficient approaches to systematically ensure high quality and to estimate values in data gaps. We apply them to satellite data of surface reflectance and temperature with different resolutions at the stations.

We evaluate the interactions between geodiversity, limnology, and aquatic species from southern Mexico to Nicaragua. Geological, limnological, sedimentological and mineralogical characteristics of 76 systems reveal two main limnological regions and seven subregions. Water ionic and sediment composition are the most influential. Species association are disjunct faunas related to limnological regions. We deduce a linear influence of geodiversity for limnology, and biological composition.

Tundra vegetation and the carbon balance of Arctic ecosystems can be substantially impacted by herbivory. We tested how herbivory by brown lemmings in individual enclosure plots impacted carbon exchange of tundra ecosystems via altering carbon dioxide (CO₂) and methane (CH₄) fluxes. Lemmings significantly decreased CO₂ uptake, while not affecting CH₄ emissions. There was no significant difference the following growing season due to recovery of the vegetation.

Mediterranean Sea ecosystems and their capability to provide ecosystem services are affected by several impacts related to human activities (e.g. overexploitation of marine resources and pollution). Future projections of the Mediterranean Sea biogeochemistry at the end of the 21st century, under two climate change emission scenarios, show an overall decline in the nutrient, oxygen and biomass content. The acidification trend is confirmed, and it is projected to be stronger in the Eastern part.

For this study, we demonstrate the commonly used TEX₈₆ paleoclimate proxy can become heavily impacted by the ocean floor archaeal community. The impact result from a combination of source inputs, their diagenetic and catagenetic alteration, and further overprint by the additions of lipids from the ocean floor sedimentary archaeal community. We then present a method to correct the overprints by both water column and subsurface archaeal community’s using IPLs extracted from both of these sources.

We assess the impact of riverine nutrients and carbon (C) on future projections of marine primary production (PP) and C uptake by using a fully coupled Earth system model. Riverine inputs (RI) alleviate nutrient limitation, thus lessen the projected decline in PP by up to 27.3 % globally. However, the large range of the uncertainty of the RI does not transfer to large uncertainty of the projected global PP and C uptake. Plausible transient RI may be important for high-resolution regional studies.

Dissolved cobalt is present in trace amounts in seawater and is a necessary nutrient for marine life. On a transect from the Alaskan coast to Tahiti, we measured seawater concentrations of dissolved cobalt. Here, we describe several interesting features of the Pacific cobalt cycle including cobalt sources along the Alaskan coast and Hawaiian vents, deep ocean particle formation, cobalt activity in low oxygen regions, and how our samples compare to a global biogeochemical model’s predictions.

A 5 year record of long-chain mid-chain diols export flux and composition are presented with a 1 to 3 week resolution from the CBeu sediment trap positioned in the NW African upwelling. All environmental parameters as well as the diol composition are dominated by the seasonal cycle, albeit with different phase relations for temperature and upwelling. The diol based proxies for nutrient concentrations, production but also those for temperature are all dominated by upwelling.

The ocean is an important part of the global carbon cycle, taking up about a quarter of the anthropgenic CO₂ emitted by burning of fossil fuels, and thus slowing down climate change. However, the CO₂ uptake by the ocean is, in turn, affected by variability and trends in climate. Here we use carbon measurements in the surface ocean to quantify the response of the oceanic CO₂ exchange to environmental conditions, and discuss possible mechanisms underlying this response.

We spectroscopically evaluated the gradients of dissolved C, N, S, Fe and Mn in a newly formed redox stratified lake. The lake features an intermediate redox state between nitrogenous and euxinic conditions that encompass vigorous open sulfur cycling, fuelled by the reducible Fe and Mn stocks of the anoxic sediments. This results in substantial bottom water loads of dissolved Fe and sulfate. Observations made in this ecosystem have relevance for deep time paleoceanographic reconstructions.

We investigated the biogeochemical processes that dominate the release and the retention of elements (nutrients and potentially toxic) during the litter degradation. Our results show that toxic elements are retained in the litter, while nutrients are released in solution during the first stages of degradation. This seems linked to the capability of trees to distribute the elements between degradation resistant and non degradation-resistant compounds of leaves, according to their chemical nature.

Because soils are an important sink for greenhouse gasses, we subjected sub-alpine grassland to a six level climate change treatment. Two independent methods showed that at warming > 1.5 °C the grassland ecosystem lost ca. 14 % or ca. 1 kg C m⁻² in five years. This shrinking of the terrestrial C sink implies a substantial positive feedback to the atmospheric greenhouse effect. It is likely that this dramatic C loss is a transient effect before a new, climate adjusted steady state is reached.

A better constrain of the components of carbonyl sulfide (COS) global budget is needed to exploit its potential as a gross primary productivity proxy. In this study, we compare two representations of oxic soil COS fluxes, and we develop an approach to represent anoxic soil COS fluxes in a land surface model. We show the importance of atmospheric COS concentration variations on oxic soil COS fluxes and provide new estimates for oxic and anoxic soil contributions to the COS global budget.

Pre and post fire values of four climate variables and four vegetation variables were analysed at the global scale, in order to observe i) the general fire likelihood factors, and ii) the vegetation recovery trends over various biomes. The main result of this study is that L-band vegetation optical depth (L-VOD) is the most impacted vegetation variable and the longer to recover over dense forests. L-VOD could then be useful for post-fire vegetation recovery studies.

Although some studies have been conducted on primary productivity in the Amundsen Sea, the spatial differences and mechanisms that drive differences in phenology, decadal and long-term changes in primary productivity are still not clear. We first obtained a bioregional map of the Amundsen Sea. Using the bioregionalization outputs, the limiting factors that affect spatial differences, the phenology, decadal and long-term changes of primary productivity was analyzed.

This study's main objective was to better understand the feeding habits of benthic foraminifera around an active methane seepage site. For this we carried out a feeding experiment with a marine methanotroph to examine uptake and cell ultrastructure using transmission electron microscopy (TEM). The results revealed three putative methanotrophs as the outside of the cell/test, which could be taken up via untargeted grazing in seeps. We conclude that this species is a non-selective deposit feeder.

The largest share of terrestrial carbon is stored in soils making them highly relevant in regard of Global Change. Yet, the mechanisms governing soil carbon stabilization are not well understood. The present study contributes to a better understanding of these processes. We show that qualitative changes of soil organic matter (SOM) co-vary with alterations of the soil matrix following soil weathering. Hence, the type of SOM that is stabilized in soils might change as soils develop.

This research utilizes high spatio-temporal resolution soil and vegetation measurements, including water stable isotopes, within an ecohydrological model to partition water flux dynamics and identify flow paths and durations. Results showed high vegetation water use and high spatio-temporal dynamics of vegetation water source and vegetation isotopes. The evaluation of these dynamics further revealed relatively fast flow paths through both shallow soil and vegetation.

This study is the first compound flooding assessment in the Kapuas River Delta. We successfully created a realistic hydrodynamic model whose domain covers the land-sea continuum using a wetting-drying algorithm in a data-scarce environment. Based on the maximum water level profile along the river, we proposed a new method to categorize the compound flooding risk zone due to tide-storm-discharge interactions, i.e., Tidally-dominated region, Mixed Energy region, and River-dominated region.

This study focused on the modelisation of two important drivers of soil greenhouse gases emissions: soil contamination and soil moisture change. The aim was to include a Cu function into the soil biogeochemical model DNDC for different soil moisture condition then to estimate variation in N₂O, NO₂ or NO_x emissions. Our results show larger effect of Cu on N₂ and N₂O emissions than on the other nitrogen species and higher effect for the soils incubated under constant than variable moisture.

Plankton are a vital group of organisms in the arctic as they are prey for animals such as fish, seals and whales. Communities of plankton consist of many different species that need different environmental conditions in order to thrive. Using data from the past decade, we show how changes to environmental conditions on an interannual time scale results in changes to the plankton community. The changes we found could have wider impacts on fisheries, and other species that feed upon plankton.

During an oceanographic cruise conducted in January 2020 in the south-western Indian Ocean we observed very low CO₂ concentrations associated to a strong phytoplankton bloom that occurred south-east of Madagascar. This biological event leaded to a strong regional CO₂ ocean sink not previously observed.

Coastal hypoxia is a major environmental problem of increasing severity. The 21^st century forecast analyzed indicates global coastal waters will warm and experience rapid declines in oxygen. The forecasted median coastal trends for increasing sea surface temperature and decreasing oxygen capacity are 48 % and 18 % faster than the rates observed over the last four decades. Existing hypoxic areas are expected to worsen and new hypoxic areas likely will emerge under these warming-related pressures.

Biological nitrogen fixation is the largest natural input of new nitrogen onto land. Earth System Models mainly represent global total terrestrial biological nitrogen fixation within observational uncertainties, but overestimate tropical fixation. The model range of increase in biological nitrogen fixation increase in the SSP3-7.0 scenario is 3 to 87 %. While biological nitrogen fixation is an key source of new nitrogen, its predictive power for net primary productivity in models is limited.