E-POLIO (SO 305_2)

E-POLIO (SO 305_2): Emerging Pollutants and Microplastic Abundance in Surface Waters of Indian Ocean

TP3/WP3: Signals of nitrogen cycling in water masses of the Indian Ocean

The aim of the project is to investigate the sources and distribution of pollutants and microplastics in the Indian Ocean. On a profile from Singapore to Mauritius, water and suspended matter samples will be examined for pollutants, microplastics and nitrogen. As part of this sub-project, water and suspended matter samples will be examined for dual stable isotopes and amino acids.

The dual isotopic signal recorded in reactive nitrogen can transport signals of nitrogen sources and nitrogen cycling processes with its water mass across oceanic basins. They are, moreover, very specific water mass tracers which help to observe mixing of water masses such as the mixing of water masses of southern and northern Indian Ocean origin. Amino acids can provide additional tracers of nitrogen cycling processes as amino acid spectra can also be water-mass specific. In this study we analyze dual nitrate isotopes, in depths profiles at seven stations in about 5° spacing, along a transect from the southeastern Bay of Bengal to Mauritius. In addition, stable nitrogen isotopes and amino acids will be analyzed (i) of suspended matter samples collected at specific depths and (ii) in surface samples at near coastal stations. This will allow a characterization of water masses with their specific nitrogen cycling processes in the fast changing but least investigated Indian Ocean. The investigations will add to a better understanding of the transport pathways of pollutants and contaminants analyzed in the other two subprojects of this joined project. The project is a German contribution to the 2nd International Indian Ocean Expedition (IIOE2).

Project partners:

TP1 and Coordination: Prof. Dr. Joanna Waniek, Leibniz Institut für Ostseeforschung, Warnemünde

TP2: Dr. Zhiyong Xie, Helmholtz-Zentrum HEREON, Geesthacht

Project duration: 2024-2026

Information about the project: Dr. Birgit Gaye, Dr. Niko Lahajnar