Ph.D. Dissertation Defense - Melissa Rohal

RESEARCH PROPOSAL SEMINAR NOTICE
COASTAL AND MARINE SYSTEM SCIENCE PROGRAM
DEPARTMENT OF PHYSICAL AND ENVIRONMENTAL SCIENCES
TEXAS A&M UNIVERSITY-CORPUS CHRISTI

SUBJECT: Ecosystem impacts of oil spills on offshore environment in the Gulf of Mexico

SPEAKER: Melissa Rohal

CHAIR: Dr. Paul Montagna

The Deepwater Horizon oil spill increased the level of concern about offshore exploration activities. The goal of this dissertation was to quantify changes to ecosystem services as a result of the DWH, test the impact of marine oiled snow on meiofauna, and investigate the resiliency of macrofauna and meiofauna benthic communities. Changes on ecosystem services were investigated using an Ecopath with Ecosim model (EWE) of the Deepwater Horizon oil spill. Model simulations found that changes in commercial fisheries yields and carbon sequestration resulted in total losses of $24,291,203. The majority of the loss was because of losses in the Grouper fisheries. In the oil spill simulation the functional groups shifted to a more demersal based diet. In particular, meiofauna contributed to a larger percent of diets for 15 of 24 functional groups. Oil reached the bottom because of sedimentation of marine oiled snow. This event, called the dirty blizzard, damaged a large area of the deep-sea. A mesocosm experiment was used to determine the effect of marine snow and petroleum on meiofauna. The presence of oil in the experiment caused an enrichment response, not a toxic response. The lack of a toxic response compared to the Deepwater Horizon area was attributed to the absence of dispersants in the experiment, because dispersants solubilize fractions of toxic hydrocarbons making them biologically available. The deep-sea benthos has not recovered from the Deepwater Horizon event. The area around the Ixtoc-1 1979-1980 oil spill was sampled to determine the recovery rate of benthic meiofauna and macrofauna. The Ixtoc signal was found between 2 and 3 cm below the sediment surface. However, high TPAH concentrations, low macrofauna diversity, and high nematode-copepod rations with depth indicate that the benthic community has not yet recovered from the Ixtoc-1 spill. If recovery occurs when the contaminated sediment moves below 10 cm, that could take another 97 years. In summary, the Deepwater Horizon oil spill caused a large loss of natural capital, oil reached the bottom via marine oiled snow, large areas were damaged, and it will take a long time (perhaps 100 years) to recover.