The scientific question that is addressed in this study is how forest disturbance affects organic and inorganic nitrogen export from a boreal landscape. The key findings are that the mobilization of inorganic nitrogen from the terrestrial environment to streams increased strongly as a response to harvesting, but the stream network removed a major fraction of this load before it reached the outlet, while organic nitrogen was not removed and transported downstream.

Permafrost thaw lakes are a subject of increasing research interest given their abundance across the northern landscape. Our aim in the present study was to characterize the photosynthetic communities in a range of subarctic thaw lakes using a combination of HPLC analysis of algal and bacterial pigments, flow cytometry and molecular analysis. Our results showed that the thaw lakes contain diverse phototrophic communities and are a previously unrecognized habitat for abundant picophotoautotrophs.

We mapped and characterized methane ebullition bubbles trapped in lake ice, and estimated whole-lake methane emission using high-resolution aerial images of a lake acquired following freeze-up. We identified the location and relative sizes of high- and low-flux seepage zones within the lake. A large number of seeps showed spatiotemporal stability over our study period. Our approach is applicable to other regions to improve the estimation of methane emission from lakes at the regional scale.

Productivity of the vegetation of northern Eurasia has been found to be increasing over the last few decades. Using statistical tools we investigate major factors driving the increase in photosynthetic activity. Most of this change is explained by rising temperatures, which drive an increase in productivity. However, the contribution of changing patterns of rainfall and cloudiness is also significant, especially in the southern parts of the region which exhibit higher drought vulnerability.

In low oxygen environments, the lack of oxygen influences sediment biogeochemistry and in turn sediment-water fluxes. These nonlinear interactions are often missing from biogeochemical circulation models because sediment models are computationally expensive. A method for parameterizing realistic sediment-water fluxes is presented and applied to the Mississippi River Dead Zone where high primary production, stimulated by excess nutrient loads, promotes low bottom water conditions in summer.

The suitability of a land use change (LUC) from cropland to short rotation coppice of poplar in Central Italy was investigated by comparing the respective greenhouse gas budgets. Biogenic and anthropogenic CO2, CH4, and N2O fluxes, change in soil C stocks, and effects of biomass use were considered. In 2 years the LUC saved 2358 ± 835 gCO2eq m-2. Net ecosystem exchange of CO2 and C exports represented the main contributions to the overall budgets, while soil non-CO2 fluxes were negligible.

This study provides the general relationship between the timing of sea ice retreat and phytoplankton size structure during the marginal ice zone bloom period in the Chukchi and Bering shelves using a satellite remote sensing approach. We also found that not only the length of the ice-free season but also the annual phytoplankton size composition positively correlated with annual net primary production.

We conducted a shipboard observation over the Chukchi Sea and the Canada Basin in the western Arctic Ocean to obtain vertical distributions of four volatile organic iodine compounds (VOIs) in seawater. High concentrations of four VOIs were found in the bottom layer water over the Chukchi Sea shelf, in which layer the concentration maximum of ammonium occurred simultaneously. We considered that the VOI production is associated with degradation of organic matter in the bottom sediment.

Lake Baikal, Siberia, is the world's most voluminous lake. Diatoms are the most dominant primary producers in the lake and form the basis of the food chain. This paper investigated the productivity of these organisms over the course of a year with a view to understanding their preservation in sediments and their value for reconstructing past productivity in the lake. This is important when recent climate change and the pressures of pollution are having demonstrable impacts in the region.

We consider the time period before and after a wind disturbance in an Austrian karst system. Using a process-based flow and solute transport simulation model we estimate impacts on DIN and DOC. We show that DIN increases for several years, while DOC remains within its pre-disturbance variability. Simulated transit times indicate that impact passes through the hydrological system within some months but with a small fraction exceeding transit times of even a year.

Thaw ponds and lakes varied in their bacterial community structure. A small number of taxa occurred in high abundance and dominated many of the communities. Nevertheless, there were taxonomic differences among different valleys implying some degree of habitat selection. Association networks were composed of a limited number of highly connected OTUs. These "keystone species" were not merely the abundant taxa, whose loss would greatly alter the structure and functioning of these aquatic ecosystem.

Several transitional settings in the western Indian continental margin, including the shelf, slope, and basin, provide multiple oxygen and other environmental gradients. These settings allowed us to investigate how oxygen and environmental factors affect and modulate the structure and function of nematode communities at the species level. An study from the Indian western continental margin with reference to nematode tolerance in the oxygen minimum zone is therefore important.

Models predict a decrease in future ocean O2, driven by surface water warming and freshening in the polar regions, causing a reduction in ocean circulation. Here we assess this effect in the past, focussing on the response of deep and intermediate waters from the North Atlantic during large-scale ice rafting and millennial-scale cooling events of the last glacial. Our assessment agrees with the models but also highlights the importance of biological processes driving ocean O2 change.

We modelled the carbon (C) cycle in Mexico for three different time periods: past (20th century), present (2000-2005) and future (2006-2100). We used different available products to estimate C stocks and fluxes in the country. Contrary to other current estimates, our results showed that Mexico was a C sink and this is likely to continue in the next century (unless the most extreme climate-change scenarios are reached).

This paper provides a unique insight into vertical distribution of leaf area index across North American ecosystems using spaceborne lidar data. This data set of leaf area index and vertical foliage profile can help set up a baseline of canopy structure needed for evaluating climate and land use induced forest changes at continental scale in the future.

We analysed 22 years of water quality data collected through a citizen science program focused on Buzzards Bay, MA. We found that summertime water temperatures warmed by nearly 2C and chlorophyll a nearly doubled across Buzzards Bay from 1992-2013. Although water quality worsened over time, nutrient concentrations remained largely the same in many places. Warming or altered rainfall patterns from a changing climate may partially offset benefits achieved by reducing nutrients.

Wildfires are the largest contributor to atmospheric pollution from all fires globally, with major consequences for health and air quality. This study examines the main contributing factors governing wildfire emissions during the 20th and 21st centuries using simulations with climate and ecosystem models. Contrary to common perception, climate change is only one of several important factors, but population change, urbanization and changing atmospheric CO2 levels are at least equally important.

The concurrence of methanogenesis and sulfate reduction was investigated in surface sediments (0–25cm b.s.f.) traversing the Peruvian margin. Surface methanogenesis was mainly based on non-competitive substrates to avoid competition with sulfate reducers. Accordingly, surface methanogenesis was mainly controlled by the availability of labile organic matter. The high relevance of surface methanogenesis especially on the shelf indicates its underestimated role within benthic methane budgeting.

The emerging field of blue carbon research seeks to quantify the carbon sequestration in coastal habitats. Seagrasses are highly productive, and have a particularly large carbon storage capacity, relative to area. This study evaluated the influence of nutrient input on seagrass carbon stocks in Florida Bay (USA). There was high carbon content in the soils, indicating that seagrass beds have extremely high carbon storage potential, even in nutrient-limited areas with low biomass or productivity.

Oceans are a source of H2, an indirect greenhouse gas. Measurements constraining the temporal and spatial patterns of oceanic H2 emissions are sparse and although H2 is assumed to be produced mainly biologically, direct evidence for biogenic marine production was lacking. By analyzing the H2 isotopic composition (δD) we were able to constrain the global H2 budget in more detail, verify biogenic production and point to additional sources. We also showed that current models are reasonably working.

Here we develop, calibrate, and test a nutrient competition model that accounts for multiple soil nutrients interacting with multiple biotic and abiotic consumers based on enzyme kinetics theory. Our model provides an ecologically consistent representation of nutrient competition appropriate for land biogeochemical models integrated in Earth system models.