Kim, Dong-gyun (2019) Exploring the relationship between zooplankton diel vertical migration and a tertiary nitrite peak in the mesopelagic oxygen minimum zone (OMZ). (Master thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, VI, 39 pp.

Preview

Text MSc_D_Kim_2019.pdf - Published Version Available under License Creative Commons: Attribution 4.0. Download (19MB) | Preview

Abstract

Oxygen Minimum Zone (OMZ) is the intense oxygen depletion area located in three main regions, the Eastern South Pacific, Eastern Tropical North Pacific, and the Arabian Sea. The OMZ occurs due to the intense upwelling event supplying the nutrients from bottom to surface.
The oxygen concentration is one of the important factors that affect the Dial Vertical Migrating (DVM) zooplanktons behavior. During the day time, DVM zooplankton stays in the core of OMZ to escape their visual oriented predators, and move to the surface during the night time to do the feeding activity. Further, It is believed that this vertically migrating behavior affects the mid water depth nutrients content as DVM zooplankton actively transport the organic matter from surface to mid water depth. But, it is not clear how the DVM zooplankton affects the nutrients content in mid water depth. This study aims to figure out whether the DVM zooplankton
affects to the nitrite content in two intense OMZ regions, Eastern South Pacific (ETSP) and the Arabian Sea.
Through the ADCP backscatter signal, the abundance of DVM zooplankton and their migrating
depth during the day time is calculated. The oxygen and nitrite concentration is collected from several CTD, Niskin bottle, and pump CTD data, and the particle data is collected from UVP5. By using these data, we estimated the relationship between them.
In addition to the secondary nitrite maximum, we found another nitrite maximum, which has can be distinguishable from secondary nitrite maximum. We named this nitrite maximum as ’tertiary nitrite maximum’. In both ETSP and the Arabian Sea, the tertiary nitrite maximum occurred in very intense oxygen regions. Especially, the tertiary nitrite maximum occurs if; 1) the oxygen concentration is less than 1 �mol kg-1, 2) DVM zooplankton goes deeper than the depth at which secondary nitrite maximum occurred.
The regression analysis between the abundance of DVM zooplankton (calculated from ADCP backscatter signal) and tertiary nitrite concentration in midwater depth shows a significant positive relationship (Pearson r= 0.50, p<0.02). Further, the comparison between the secondary nitrite maximum and tertiary nitrite maximum shows a significant positive relationship (Pearson r=0.68, p<0.05), and the relative average ratio is 0.94. These result may imply DVM zooplankton actively export the organic nitrogen from surface to mid-water depth and thereby fuel the denitrification process, which will eventually drive the N loss in the ocean.
thereby fuel the denitrification process, which will eventually drive the N loss in the ocean.

Actions (login required)

View Item