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Advisory Committee Chair

Stephen A Watts

Advisory Committee Members

Julia M Gohlke

Mickie L Powell

Document Type

Thesis

Date of Award

2014

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

Following the Deepwater Horizon oil spill the dispersant Corexit EC 9500A (C-9500) was applied to facilitate rapid oil degradation. C-9500 toxicity has been evaluated on a number of marine species; however, many of these studies do not account for environmental conditions that may increase negative outcomes related to dispersant exposure in the wild. We examined lethality and behavioral effects of C-9500 exposure on the model marine zooplankton Brachionus plicatilis. We also evaluated interactions of abiotic and biotic stressors that may alter outcomes of exposure. C-9500 exposure at standard husbandry conditions (17.5ppt, 24°C, 200 rotifer*ml-1 density) produced a 24 hr median lethal concentration of 107 ppm for cultured B. plicatilis by Probit analysis. Rotifers surviving exposure to a low concentration (50 ppm) of C-9500 exhibited increased swimming velocity, suggesting increased metabolic rate and a possible escape response to chemical perturbation. Rotifers surviving exposure to higher concentrations (100 and 150 ppm) exhibited a decreased swimming velocity and a reduced net to gross movement ratio indicative of an altered directional swimming behavior. Significant interaction between C-9500 exposure and increasing temperature was observed resulting in a decreased upper thermal range of exposed B. plicatilis populations. Increasing salinity also interacted with C-9500 exposure resulting in increased mortality at higher salinities. Increased or decreased nutritional availability over the exposure period did not significantly alter mortality of B. plicatilis populations at concentrations tested. Results from this study may be useful for predicting possible outcomes on marine zooplankton following dispersant application under diverse natural conditions.

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