Master of Science (MS)
Oceanography and Coastal Sciences
The Deep Water Horizon (DWH) oil spill resulted in the largest accidental release of crude oil in U.S. waters with both short- and long-term effects on the marine environment. Extensive studies conducted immediately following the oil spill in the northern Gulf of Mexico provided greater understanding of the physical processes influencing the distribution of the released oil, including the use of optical detection of polycyclic aromatic hydrocarbons (PAHs), a toxic crude oil fraction in the northern Gulf of Mexico. In this study, the optical properties of chromophoric dissolved organic matter (CDOM) and the concentrations of dissolved organic carbon (DOC) were examined from seawater samples collected during two cruises in April of 2012 and 2013 near the DWH spill site in the northern Gulf of Mexico. During both 2012 and 2013, eddies associated with the Loop Current appeared to strongly influence the hydrography at the study site with deeper mixed-layer depths in 2012 than in 2013. Average DOC concentrations were similar in 2013 (mean 0.96 +- 0.20 mg L-1) in comparison to 2012 (0.85 +- 0.25 mg L-1) with higher levels in the near surface waters than at depths. Absorption and fluorescence properties of CDOM for samples obtained in 2013 revealed both the characteristics and composition of CDOM near the DWH site. Absorption coefficients at 355 nm (aCDOM(355) m-1) used to quantify CDOM in seawater varied over a small range and showed elevated values at depths corresponding to or just below the chlorophyll fluorescence maxima suggesting autochthonous contribution to the CDOM pool. In contrast to river-influenced coastal regions, relationships between CDOM optical properties and salinity were not clear due to the small salinity range in the study region. Excitation-emission matrix fluorescence (EEMs) of CDOM revealed the presence of typical humic-like and protein-like fluorophores. Parallel factor analysis (PARAFAC) of EEMs resulted in four fluorescent components characterized as humic-like (two) and protein-like (two). Higher values of protein-like components both in surface and depth at stations with more elevated surface chlorophyll fluorescence north of the DWH suggests biological contribution to the CDOM pool and its fluxes to depths with implications to related fluxes of contaminants such as PAHs.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
Li, Zhi, "CDOM optical properties near DWH site, Gulf of Mexico: pot oil spill" (2014). LSU Master's Theses. 1347.