The role of N and P released by copepods on biogeochemical cycles and the microbial community during the OUTPACE cruise was studied. In the presence of copepods, NH4+ and DON increase, and an enhanced remineralization was observed. A shift in active bacterial composition was observed, linked with changes in nutrient concentrations. Copepods can be a source of (in)organic compounds for bacterial communities that contribute to nutrient recycling and regenerated production in the photic zone.

Arctic warming mobilizes belowground organic matter in northern high latitudes. This study focused on the size of organic carbon pools and organic matter quality in ice-rich permafrost on the Baldwin Peninsula, West Alaska. We analyzed biogeochemistry and found that three-quarters of the carbon is stored in degraded permafrost deposits. Nonetheless, using biomarker analyses, we showed that the organic matter in undisturbed yedoma permafrost has a higher potential for decomposition.

Phytoplankton biomass changed significantly in the North Atlantic north of 40° N over 1998–2007. With a physical-ecosystem model, we show that biomass increases in the northwest are due to reduced vertical mixing that partially relieves light limitation of phytoplankton. To the east, these circulation changes lead to fewer nutrients being supplied horizontally from the west. Relationships between these biomass variations and atmosphere and ocean physics are not straightforward.

Northern forests enhanced their productivity during and before the 2010 Russian mega heatwave. We scrutinize this issue with a novel type of multivariate extreme event detection approach. Forests compensate for 54 % of the carbon losses in agricultural ecosystems due to vulnerable conditions in spring and better water management in summer. The findings highlight the importance of forests in mitigating climate change, while not alleviating the consequences of extreme events for food security.

We used a time series of MODIS (MAIAC) satellite images from 2000 to 2017 to map the distribution of bamboo-dominated forests in the southwest Amazon and detect when the bamboo populations are suffering massive die-offs. The aim was to test if bamboo die-off is associated with higher fire probability, which could impact other plant species while promoting bamboo dominance. Our findings show 15.5 million ha of bamboo forests which are not directly associated with fire, except in drought years.

A physical–biogeochemical model was applied to study the response of hypoxia and oxygen dynamics to different riverine inputs. Results showed that the hypoxia in the Pearl River estuary was most sensitive to riverine inputs of POC, followed by DO and nutrients. This study also highlighted the significance of re-aeration for its buffering effects; i.e. the re-aeration responded rapidly to the perturbations of riverine inputs and in turn moderated the DO changes impacted by these perturbations.

Nitrous oxide (N₂O) is a strong greenhouse gas and ozone-depletion agent. Intense N₂O effluxes had been observed from nutrient-rich estuaries with human impacts, such as the Chesapeake Bay. We report that increased nitrogen availability and low-oxygen conditions stimulate N₂O production. Thus, controlling the nutrient input to the bay will decrease nitrogen availability and alleviate eutrophication, leading to water column reoxygenation, and subsequently will mitigate N₂O emission.

The ability of marine macroalgae to adapt to changing ocean chemistry will depend on the flexibility of their inorganic carbon uptake mechanisms across biogeographic ranges. Therefore, we investigated the plasticity of inorganic carbon uptake mechanisms in north Atlantic rhodoliths – free-living calcifying red algae that form important benthic habitats in coastal environments. We observed flexible mechanisms related to seawater DIC concentrations, indicating the potential for adaptation.

Time-series sites have been instrumental in providing insight into how the ocean functions. However, to extrapolate the results from a single site to a larger region, the dynamics at the site must be placed into the context of regional-scale dynamics. We develop a framework for determining the spatial domain of a time-series site using high-resolution data. This framework quantifies the representativeness of the site and can be used to improve sampling to better capture the dynamics at the site.

Photosynthetic activity and/or nitrate assimilation by the macroalgae Ulva buffered carbonate chemistry and yielded enhanced growth of bivalves by mitigating the harmful effects of elevated CO₂ levels. This benefit was not limited to acidified conditions, as evidenced by increased bivalve growth in the presence of Ulva within ambient CO₂ treatments. The ability of macroalgae to buffer carbonate chemistry may be increasingly important for calcifying organisms vulnerable to ocean acidification.

Single-celled, benthic foraminifera play a major role in marine biogeochemical cycling. This study compares the organic-matter-derived carbon and nitrogen processing of two abundant intertidal foraminifera species. The results of our laboratory feeding experiments suggest a significant difference in the contributions of each species to coastal carbon and nitrogen fluxes, which is mainly attributed to their different metabolic lifestyles.

The effect of inorganic nutrients on planktonic assemblages has been traditionally assessed by looking at concentrations rather than fluxes of nutrient supply. However, in near-steady-state systems such as subtropical gyres, nitrate concentrations are kept close to the detection limit due to phytoplankton uptake. Our results, based on direct measurements of nitrate diffusive fluxes, support the key role of nitrate supply in controlling the structure of marine picoplankton communities.

We explored the timing of the peak of the short annual growing season in tundra ecosystems as indicated by an extensive suite of satellite indicators of vegetation productivity. Delayed peak greenness compared to peak photosynthesis is consistently found across years and land-cover classes. Plants also experience growth after optimal conditions for assimilation regarding light and temperature have passed. Our results have implications for the modelling of the circumpolar carbon balance.

The present study describes responses of picocyanobacteria (PCY) physiology to different environmental conditions. The cultures were grown under 64 combinations of temperature, irradiance in a photosynthetically active spectrum (PAR), and salinity. The results show that each strain of Baltic Synechococcus sp. behaves differently in respective environmental scenarios. The study develops the knowledge on bloom-forming PCY and reasons further research on the smallest size fraction of phytoplankton.

In this study we collected in situ accretion/erosion rates and abiotic/biotic variables to estimate carbonate budgets and ecological drivers of coral reef growth in the central Red Sea. Our data suggest that reef growth is comparable to estimates of other regions, but the erosive forces in the Red Sea are not as pronounced. Comparison with recent data suggests that Red Sea reef growth might not have decreased over the past decades, despite warming, calling for more detailed investigations.

Humans have had a huge impact on the mercury cycle in the biosphere, but it is difficult to follow the mercury cycle because mercury has so many mobile forms, as gases in the atmosphere and solutes in water. Mercury isotopes constrain mercury fluxes and sources, because mercury has many stable isotopes, and different fractionation mechanisms have different fingerprints in those isotopic compositions. We present the first model of mercury isotopic composition in the ocean.

This study looks at how foraminifera interact with their geochemical environment in the seabed. We focus on the incorporation of the trace metal manganese (Mn), with the aim of developing a tool to reconstruct past pore water profiles. Manganese concentrations in foraminifera are investigated relative to their ecological preferences and geochemical environment. This study demonstrates that Mn in foraminiferal tests is a promising tool to reconstruct oxygen conditions in the seabed.

Our work provides new insights into the biogeochemical cycling of iron, methane and phosphorus. We found that vivianite, an iron-phosphate mineral, is pervasive in methane-rich sediments, suggesting that iron reduction at depth is coupled to phosphorus and methane cycling on a much greater spatial scale than previously assumed. Acting as an important burial mechanism for iron and phosphorus, vivianite authigenesis may be an under-considered process in both modern and ancient settings alike.

Basin-wide comparisons of 3 major greenhouse gases (GHGs) were combined with measurements of C isotopes in DOC, CO₂, and CH₄ to explore how dams and urban wastewater modify the continuum of riverine GHG dynamics in a highly human-impacted river basin in Korea. Contrasting dam effects on 3 GHGs and pulsatile increases in GHGs downstream of urban tributaries delivering wastewater-derived GHGs and old DOC suggest anthropogenic discontinuities in riverine metabolic processes and GHG dynamics.