Boreal soils are important to the global C cycle. We need to understand what controls how C accumulates and is lost from this soil. To help we examined C & N accumulation rates for five boreal ecosystems. Most ecosystems were similar. But the rich fen had higher long-term C & N accumulation rates, likely due to differences in nutrient cycling & because it burns less. Therefore, shifts among ecosystems will not change regional C & N dynamics much, unless there is a shift to or from a rich fen. Hide

Estuarine sediments are important locations for carbon cycling and burial. We used tracer experiments to investigate how site conditions affect the way in which seafloor biological communities cycle carbon. We showed that while total respiration rates are primarily determined by temperature, total carbon processing by the biological community is strongly related to its biomass. Further, we saw a distinct pattern of carbon cycling in sandy sediment, in which uptake by bacteria dominates. Hide

In this study we used a state-of-the-science coupled physical–biogeochemical model to simulate and examine temporal and spatial variability of sea surface CO₂ concentration in the Gulf of Mexico. Our model revealed the Gulf was a net CO₂ sink with a flux of 1.11 ± 0.84 × 1012 mol C yr⁻¹. We also found that biological uptake was the primary driver making the Gulf an overall CO₂ sink and that the carbon flux in the northern Gulf was very susceptible to changes in river inputs. Hide

Bacterial extracellular enzymes play a significant role in the degradation of organic matter in the open ocean. Using artificial fluorogenic substrates, this research highlights potential artefacts in the response of bacterial glucosidase and aminopeptidase to ocean acidification, and the effects of three different acidification techniques. We conclude that fluorogenic substrate degradation is affected by, or alters pH, and bubbling CO₂ may lead to the overestimation of carbohydrate degradation. Hide

The Southeast Pacific hosts one of the most extensive oxygen minimum zone (OMZ), yet the dynamics behind it remain unveiled. We use a high-resolution coupled physical–biogeochemical model to document the seasonal cycle of dissolved oxygen within the OMZ in both the coastal zone and the offshore ocean. The OMZ seasonal variability is driven by the seasonal fluctuations of the dissolved oxygen eddy flux, with a peak in Austral winter (fall) at the northern (southern) boundary and near the coast. Hide

Subarctic lakes are changing in size as a result of permafrost thawing, resulting in mobilization of soil materials. Our study characterizes the carbon and nutrient regime of a set of thaw lakes and their adjacent permafrost soils in a rapidly degrading landscape, showing how these materials create favorable conditions for aquatic bacterial communities. We discuss the controls over the bacterial community, and demonstrate that gain processes are not a primary control. Hide

Leaf chemical concentrations are key traits in ecosystem functioning. Previous studies were biased for trees and grasses. Here, we explored the patterns of leaf N and P concentrations in relation to climate, soil, and evolutionary history in northern China. We found that climate influenced the community chemical traits through the shift in species composition, whereas soil directly influenced the community chemical traits. Hide

We evaluated the soil carbon stock estimates of Yasso07, Q, and CENTURY soil carbon models, used in national greenhouse gas inventories in Europe, Japan, and USA, with soil carbon stock measurements from Swedish Forest Soil National Inventories. Measurements grouped according to the gradient of soil nutrient status revealed that the models underestimated for the Swedish boreal forest soils with higher site fertility. We discussed mechanisms of underestimation and further model developments. Hide

The main contribution of our study is our finding that rhizodeposits and microbe-assimilated carbon contribute significantly to the sequestration of carbon substrates in rice paddy soils. This contribution is theoretically and practically relevant because few studies have investigated the effects of different carbon substrates on the mineralization of native soil organic carbon and our findings have immediate applications for improving the fertility of paddy soils and mitigating global warming. Hide

We were excited about nature’s diversity when we discovered spectacular flows of heavy oil at the seafloor with the remotely operated vehicle QUEST 4000 m in Campeche Bay, southern Gulf of Mexico. Vigorous methane gas bubble emissions lead to massive gas hydrate deposits at water depth as deep as 3420 m. The hydrates formed metre-sized mounds at the seafloor that were densely overgrown by vestimentiferan tubeworms and other seep-typical organisms. Hide

We have analysed the rate of calcification of fossil reef corals. These measurements are important, because the rate of formation of the skeleton depends on the physical environment in which the corals lived. The rates of skeletal calcification of the fossils were approximately 50 % lower than they are in extant reef corals. This is a likely effect of high water temperatures and/or low carbonate saturation of the water – factors that will also affect coral growth by future global warming. Hide

Regime shifts have been suggested in the late 1970s and late 1980s in the Gulf of Alaska with important consequences for fisheries. Here we investigate the ability of a suite of ocean biogeochemical models of varying complexity to simulate these regime shifts. Our results demonstrate that ocean models can successfully simulate regime shifts in the Gulf of Alaska region, thereby improving our understanding of how changes in physical conditions are propagated from lower to upper trophic levels. Hide

We constructed the habitat models explaining the spatial patterns of the large and small Arctic copepods and the Pacific copepods of the northern Bering Sea and Chukchi Sea. The adequate models show the importance of water masses and sea ice retreat timing. This finding also indicates that earlier sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic–benthic-type ecosystem to a pelagic–pelagic type. Hide

Through a 2-year field experiment and meta-analysis, we found higher GHG (dominated by CH₄ emission) and Nr (dominated by NH₃ volatilization) was released from rice production in TLR, causing great environmental costs, due to direct straw incorporation and excessive N fertilization. Sensible N reduction reduced the GHG and Nr to some extent, but further mitigation is possible, especially for CH₄ emission and NH₃ volatilization, considering current incorporation pattern of straw and N fertilizer. Hide

The recent focus on carbon (C) trading has intensified interest in "Blue Carbon" – C sequestered by coastal vegetation. However, the factors influencing C storage are poorly understood. The patterns found in this study support that C storage in Posidonia seagrass soils is influenced by interactions of biological, chemical and physical factors within the meadow. We conclude that there is a need to improve global estimates accounting for biogeochemical factors driving variability within habitats. Hide

This paper presents concentrations of several trace gases produced by the Baltic Sea phytoplankton community during a mesocosm experiment with five different CO₂ levels. Average concentrations of dimethylsulphide were lower in the highest CO₂ mesocosms over a 6-week period, corresponding to previous mesocosm experiment results. No dimethylsulfoniopropionate was detected due to a methodological issue. Concentrations of iodine- and bromine-containing halocarbons were unaffected by increasing CO₂. Hide