Comparative examination of processes affecting the marine Nitrogen cycle of the ETNP

Abstract

[Author's Abstract] Nutrients in the ocean are used by plankton at the bottom of the food web, which act as food for progressively larger organisms. In particular, nitrogen based nutrients are often in short supply, limiting the growth of the plankton. The process of denitrification converts these nutrients into nitrogen gas which escapes into the air, preventing them from being used. Denitrification can be broken into two processes, known as heterotrophic denitrification and the anammox reaction, which are both driven by bacteria. This study focused on these two processes in attempt to show which of them removes more nitrogen from the water. To do so, each nutrient was tagged with an isotope tracer and injected into bags of seawater. As the nutrients incubate in the bag, the bacteria inside converted the tagged nutrients into tagged nitrogen gas, which was measured using a mass spectrometer. The amount of nitrogen gas produced from each process is an indicator of the rates of heterotrophic denitrification and the anammox reaction. This information allows for an interpretation of each process’ contribution to nitrogen removal in the ocean.