NITROFORAM · The New Players in the Marine Nitrogen Cycle: Benthic Foraminifera

Generally, anaerobic respiration of nitrate is regarded as a bacterial process. In addition to bacteria only three eukaryotes were known to have the potential to reduce nitrate and nitrous oxide. However, very recently three species of benthic foraminifera were found to respire nitrate completely to dinitrogen gas. To be able to do so they store high concentrations of nitrate in their cell (Risgaard-Petersen et al. 2006). Benthic foraminifera are unicellular eukaryotes that are among the most successful organism in marine environments and they can be very abundant in anoxic habitats, which suggests that their role in the N cycle might be very important. In the proposed project we will investigate Foraminifera known to occur predominantly in anoxic sediments for the presence of intracellular nitrate sources and ability to respire these through denitrification. In this way the importance of this process in the total nitrogen cycle will be determined. We will also survey how different species of foraminifera are related, and how is the evolution of this anaerobic respiration in eukaryotes. Last but not least, we will investigate different species of nitrate respiring foraminifers for survival and uptake mechanisms.