Identification of microbes involved in the nitrogen cycle along vertical profiles in the eastern tropical North Atlantic Ocean

• Main Author: Löscher, Carolin
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/5462/; https://oceanrep.geomar.de/id/eprint/5462/1/Dipl.%202008%20L%C3%B6scher,%20C.pdf

• The genes amoA, nirS and nifH were found to be present in the research area. • Denitrification is not expected to take place in the investigated area according to too high oxygen concentrations, an enrichment of nitrate in the depths of oxygen minimum and a positive correlation between ΔN2O and AOU or nitrate. Anammox is also not expected to take place due to high oxygen concentrations. • The genetic findings indicate, that nitrification, especially crenarcheotal nitrification, can be assumed to be a major process within the nitrogen cycle in this area. Nitrification could consequently be considered as a possible N2O producing process, here. • A pattern of spatial distribution could not be observed for crenarchaeota. • Nitrogen fixers could be detected throughout the water column and were found to be active mainly in the surface. They clustered into three main clades, cyanobacteria, ϒ-proteobacteria and organisms which are related to cluster III organisms. • Nitrogen fixers showed a pattern of spatial distribution along vertical profiles with cyanobacteria mainly in the surface layers and ϒ- proteobacteria dominating in deeper waters. • The fact that nitrogen is supplied below the Redfield ratio in the ETNA seems to provide a possible necessity for nitrogen fixation, especially in the oligotrophic surface waters in this area.