About:

Lipids as indicators of N-cycling in sub-oxic zones of present and past oceans (project funded by The Darwin Center for Biogeosciences; project nr 3012)
Project leader: Prof. dr. J. S. Sinninghe Damsté
Researcher(s): MSc M. Sollai

Abstract
In the last decade, our view on the functioning of the marine nitrogen cycle has changed considerably. Both bacterial anaerobic ammonium oxidation (anammox) and archaeal nitrification were shown to be important novel pathways in the complex marine N-cycle. Both pathways occur in the sub-oxic zones of the ocean, have important consequences for the marine N-budget, but the functioning of these microbes in addition to other bacteria (nitrite-oxidizing and denitrifying bacteria) in natural settings remains far from understood. In past oceans N-cycling in sub-oxic zones probably also played an important role, especially at times of deposition of organic-rich shales (e.g. sapropels, Cretaceous black shales) with important consequence for the availability of fixed nitrogen for phytoplankton. This projects aims at the development and application of microbial biomarkers for N-cycling through the study of lipids in cultures, presents-day sub-oxic environments, settling particles from these environments, and sediments deposited at the time of ocean anoxia. In addition, we will apply new biomarkers for N2-fixing cyanobacteria in ancient sediments to test if these bacteria compensated the fixed N-loss through anammox. This project will provide further insight in present (in close collaboration with the sister project) and ancient N-cycling in sub-oxic settings.