Abstract:

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.

Suggested Citation:

Chin, Wei-Chun; Chiu, Meng-Hsuen (James). 2017. Impact of Oil and Corexit on Marine Dissolved Organic Matter (DOM) Aggregation and Microgel Formation Through Dynamic Laser Scattering (DLS). Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7KH0KBC

Publications:

Chiu, M.-H., Garcia, S. G., Hwang, B., Claiche, D., Sanchez, G., Aldayafleh, R., … Chin, W.-C. (2017). Corexit, oil and marine microgels. Marine Pollution Bulletin. doi:10.1016/j.marpolbul.2017.06.077

Purpose:

To understand and compare the origin of microgel formation under oil spill and dispersant condition. This data will provide evidence of the origin of marine aggregates.

Data Parameters and Units:

treatment, replicate, time (hr), particle size (um) WAF: Water accommodated fraction. CEWAF: chemically (corexit) enhanced water accommodated fraction. 8hr WAF: collect water sample from WAF mesocosm after 8 hrs set up. 8hr CEWAF: collect water sample from CEWAF mesocosm after 8 hrs set up. 48hr WAF: collect water sample from WAF mesocosm after 48 hrs set up. 48hr CEWAF: collect water sample from CEWAF mesocosm after 48 hrs set up.

Methods:

Samples were shaken, and filtered through a 0.22-μm Millipore membrane (pre-washed with 0.1N HCl) before use. Aliquots were then poured directly into scattering cells. The scattering cells were positioned in the goniometer of a Brookhaven laser spectrometer (Brookhaven Instruments, NY, USA). The polymer assembly was monitored for 8 ~ 10 days by analyzing the scattering fluctuations detected at a 45 degree scattering angle. The autocorrelation function of the scattering intensity fluctuations was averaged over a 10-min sampling time, using a Brookhaven BI 9000AT auto correlator. Particle size distribution was calculated by the CONTIN method. Each measurement was taken in triplicate in 10 ml at room temperature. A calibration of the DLS method was conducted using standard suspensions of latex microspheres.

Instruments:

dynamic laser scattering

Individual Files: