Elucidating carbon flow in settling aggregates

Abstract

The ocean inherits a major role in atmospheric CO2 drawdown. A key driver in carbon sequestration the biological carbon pump, where primary producers photosynthetically fix CO2 in surface waters, convert it into particulate organic forms and transport it into the ocean interior. The main fraction of the particulate organic carbon occurs in forms of sinking phyto- and zooplankton, detritus, zooplankton fecal pellets and microbes. When these marine particles coagulate, they form macroscopic aggregates. The formation of aggregates and the resulting specific sinking velocity are considered as key factors determining the efficiency of carbon export, whereby the sinking velocity defines the time an aggregate is exposed to mineralization and consumption processes, conducted by microbes and zooplankton. Within this thesis I investigated the process of aggregate formation influenced by nutrient availability, possible causes of episodic flux events and the overall carbon and nitrogen flow in the biological carbon pump.