Date Available

12-17-2013

Year of Publication

2013

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Arts and Sciences

Department/School/Program

Earth and Environmental Sciences (Geology)

First Advisor

Dr. Kevin M. Yeager

Abstract

Following the 2010 Deepwater Horizon (DWH) spill, sediment cores were analyzed from marshes at various levels of oiling to determine how deeply oil penetrated sediment in these marsh environments, and if at these sites it had quantifiably affected benthic ecosystems. Minimum mixing depths were determined from penetration of the lithogenic radionuclide 234Th, which ranged from 0.25 to 4.5 cm. Sediment accumulation rates were determined using 210Pb, with verification from 137Cs in selected cores. Lead-210 profiles revealed long-term (decadal) mixing. Bay Jimmy, Louisiana was significantly affected by the DWH oil spill, as indicated by total polycyclic aromatic hydrocarbon concentrations of up to 21,913 ppb. This is far above the level at which adverse biological effects occur (4,022 ppb). Benthic foraminifera responded to the heavy oiling by decreases to standing stock and depth of habitation relative to unoiled sites, as well as exhibiting deformities. These data clearly show that oil can be quickly mixed into salt marsh sediments, with demonstrable impacts on indigenous benthos. Further, radioisotope inventories indicated that most of the sampled sites are in a net erosional state. Should marshes containing trapped DWH oil be submerged by rising sea level, there is a great potential for the remobilization of oil.

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