Role of eukaryote pico- and nanoplankton in the biogeochemical processes of the deep sea.

In this project we investigate the distribution and activity of the smallest eukaryotes of the deep sea in order to understand their ecology and contribution to biogeochemical processes. Using fluorescence in situ hybridization, protists in the pico- and nanoplankton size range (i.e., primarily heterotrophic flagellates) are enumerated and classified into major taxonomic groups.

A major focus is placed on the basin-scale distribution of major taxonomic groups in the deep subtropical North Atlantic (900 - 6000m), their relation with bacterial and archaeal biomass, and their correlation with organic and inorganic dissolved nutrients.

Our sampling strategy involves following representative water masses of major currents such as the Antarctic Intermediate Water, the North Atlantic Deep Water and the Antarctic Bottom Water that represent a range of 14C-ages. Bacterivory and viability of these protists are measured using titanium samplers that maintain pressure and can be kept at in situ temperature onboard the research vessel for live incubations.

This project is an international collaboration with Dr. Gerhard Herndl at the Netherlands Institute of Sea Research (NIOZ).