Planktonic Influence on the Toxicity of HEWAFS (High-Energy Water Attenuated Fractions)

• Main Author: Saal, Erin Elizabeth
• Other Authors: Wilson, Vince Lee
• Format: Others
• Language: en
• Published: LSU 2015
• Subjects: Environmental Sciences
• Online Access: http://etd.lsu.edu/docs/available/etd-11032015-141209/

The Deep Water Horizon oilrig explosion led to the release of 6.8 ± 1.7 x 108 kg or 4.9 million barrels of petroleum hydrocarbons into the Gulf of Mexico. The spill persisted from the end of April to mid July 2010 affecting a significant portion of the Gulf coast. The effects of this spill are being studied in labs across the country, and this thesis investigated high-energy water accommodated fractions (HEWAFs) as a potential tool for use in this effort. Water accommodated fractions (WAFs) are mediums containing only the fraction of petroleum that remains in aqueous phase after a mixing energy has been removed, and after a period sufficient for phase separation. HEWAF was the exposure medium of choice because this type of WAF is created by vigorous mixing of seawater with crude oil, similar to what occurs in the environment. The effects of plankton (a zooplankton and phytoplankton species) on the toxicity of HEWAFs were also investigated because the spill occurred at a time of year when plankton populations are especially high in the Gulf of Mexico. Dr. Sarah Webb looked at how the HEWAFs and inclusion of plankton affected the test species, Anchoa mitchilli. The inclusion of plankton was also meant to more closely resemble the natural environment, and give a more accurate indication of oil spill dynamics in the Gulf ecosystem. The trials conducted throughout this experiment demonstrated that concentrations of aromatics and alkanes increased steadily with increases in HEWAF loadings. At high HEWAF loadings (33.3% HEWAF and above), alkane and aromatic concentrations in samples containing plankton were elevated; however, this effect dropped off in lower HEWAF concentrations (15% HEWAF and below). HEWAF shows potential as a tool in exposures simulating GoM conditions, but much more work needs to be done before the results they yield are reliable. The species responsible for the planktonic effect seen in the high HEWAF loading studies was not determined in this study; however, the results do show that plankton might play a significant role in crude oil partitioning in the environment. This would make plankton important in exposures for determining real world oil toxicities.