Impact of Oil and Corexit on Marine Dissolved Organic Matter (DOM) Aggregation and Microgel Formation Through Dynamic Laser Scattering (DLS)

Marine dissolved organic carbon (DOC), a major reservoir of reduced carbon in the ocean, plays a critical role in marine carbon cycling. Marine microgel formation represents a critical link between more refractory DOC and POC (particulate organic carbon), an available pool of higher bioreactivity and biodegradable organic carbon accessible to the microbial community. Biopolymers (exopolymeric substances, EPS) released from marine phytoplankton or bacteria serve as important sources for the surface DOC pool that contribute to microgel formation. Here we aim to investigate the impact of oil and corexit on this critical process for surface ocean carbon dynamics. We performed mesocosm studies with four treatments: control, water accommodated oil fraction (WAF), Corexit plus WAF (CEWAF), and a diluted CEWAF (DCEWAF), in which the CEWAF and DCEWAF each match the oil concentration in the WAF tank. Our preliminary results based on dynamic laser scattering indicate that oil and Corexit can significantly change the assembly of microgels. Our observation will provide supporting evidence to help us understand the relationships shaping remineralization of these materials and the interactions with the microbial community. Further, the findings will help elucidate processes for the transport/mobilization of oil-derived carbon in the water column, and consequently its fate (sinking, dispersion or aggregation) in the ocean.