Marine biogeochemical cycles and climatic gases

Climatic gases include both greenhouse (CO2, N2O, CH4) and cooling (DMS) gases.  The Ocean plays an important role as a buffer to global warning, by absorbing some 40 % of the CO2 released annually and by releasing some 15% of the global sulphur emissions.

The net uptake of CO2 results from heating and cooling of surface waters (physical pump) and from biological uptake and export of organic carbon to the deep waters (biological pump). Five phytoplankton functional types (diatoms, pico/nanophytoplankton, coccolithophorids, Phaeocystis, nitrogen-fixers) have been identified as important for understanding the functioning of the biological pump, the associated biogeochemical cycles (C, N, P, Si, S, Fe) and the related effect on climate change.

In accordance, ESA research on global and climate change involves process-level experimental studies and complex ecosystem modelling.

Both aim to an increased understanding of the mechanisms controlling the biological pump in the global ocean (EU-IRONAGES), with a focus on the coastal ocean (AMORE, CARBOOCEAN), the Southern Ocean (BELCANTO, CARUSO) and ice-covered regions of the northern and southern polar oceans (SIBCLIM).

The ocean is the main natural sulphur source via the phytoplankton syntheis of  dimethylsulphoniopropionate (DMSP), the DMS precursor. The lack of correlation between observed DMS and phytoplankton distributions is explained by the complexity of DMSP production and conversion to DMS pathways. Indeed the ability to synthetize DMSP is species-specific and varies with environmental conditions. Moreover, the enzymatic cleavage of DMSP in DMS can either be performed by phytoplankton or bacterial lyases. In this context ESA aims to improve the knowledge and modelling of DMS production and its emission to the atmosphere in the coastal North Sea (DMS-SNS).