A multi-proxy approach is applied in surface sediments collected from deep slopes and basins (1018-4087 m depth) of the oligotrophic eastern Mediterranean Sea. This study sheds new light on the sources and transport mechanisms along with the impact of preservation vs. diagenetic processes on the composition of sedimentary organic matter in the deep basins of the oligotrophic eastern Mediterranean Sea.

One continuing, significant source of uncertainty in global climate predictions is the combined effect of wind and pressure on trace gas fluxes. We quantified the effects of wind speed and pressure on fluxes of CO2 and CH4 within three different ecosystems. Trace gas fluxes are positively correlated with both wind speed and pressure near the soil surface but we argue that wind speed is a better proxy for general use. These results have implications for a number of global feedback mechanisms.

-A shift from diatom-associated diazotrophs (DDAs) to unicellular cyanobacterial group C (UCYN-C) in response to DIP fertilization was captured in a large-scale mesocosm experiment in the Noumea lagoon (NL), a low-nutrient low-chlorophyll coastal environment. -First report of in situ net growth and mortality rates for unicellular diazotrophs UCYN-A2, and UCYN-C. -First quantitative abundance data for diazotrophs in NL indicate that DDAs and UCYN-A1/A2 may be important N2 fixers in this region.

Gamma ray (GR) fluctuations and K values from downhole logging data obtained in the sediments of Lake Ohrid correlate with the global climate reference record (LR04 stack from δ18O) (Lisiecki and Raymo, 2005). GR and K values are considered a reliable proxy to depict glacial-interglacial cycles and document warm, humid and cold, drier periods. A robust age model for the downhole logging data over the past 630kyr was established and will play a crucial role for other working groups.

The waters of the tropical Atlantic Open Ocean usually contain comparably high concentrations of oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic.

In the sediments underlying the global oligotrophic ocean, low levels of microbial activity persist, despite low input of organic matter from surface ocean productivity. Using measured nitrogen and oxygen isotopes of porewater nitrate we estimate the magnitude and extent of microbial nitrogen cycling. We find evidence for the overlap of both denitrification as well as autotrophic pathways such as nitrification and nitrogen fixation, pointing to a relatively large role for subsurface autotrophy.

Future climate change has the potential to increase drought in many regions of the globe. Recent data syntheses show that drought sensitivity varies considerably among plants from different climate zones, but state-of-the-art models currently assume the same drought sensitivity for all vegetation. Our results indicate that models will over-estimate drought impacts in drier climates unless different sensitivity of vegetation to drought is taken into account.

The coastal upwelling systems, e.g. off Peru and Mauritania, are key regions for the emissions of climate relevant trace gases from the ocean into the atmosphere. Here, gases and nutrients are transported into the ocean mixed layer from below. The upwelling velocities, however, are too small to be measured directly. We use the enhancement of helium-3 in upwelled waters to quantify the vertical velocity, which varies between 1.0 and 2.5 metres per day in the coastal regions.

Two large floodplains hold the peak flows in the Zambezi River system – the dam-impacted Kafue Flats and the largely pristine Barotse Plains. Here we show that the inputs of organic matter and nutrients from such floodplains to the river are strongly affected by the presence of hydropower dams and highlight how floodplains act as large biogeochemical reactors that can behave distinctly differently from the entire catchment.