Effect of Two Oil Dispersants on Larval Grass Shrimp (Palaemonetes pugio) Development.

Abstract:

The study focused on the effects that two oil dispersants, Corexit® EC9500A and Finasol® OSR52, have on the development of larval grass shrimp, (Palaemonetes pugio). The hypothesis was that Finasol would have a greater effect on larval grass shrimp development than Corexit. The experiment was conducted using 300 grass shrimp larvae that were 24 hours old. Each larva was exposed individually. In total, five sub-lethal concentrations were tested for each dispersant (control, 1.25, 2.50, 5.0,10.0 mg/L). The larvae were exposed for five days then transferred to clean seawater until metamorphosis into the juvenile stage. Key data measurements recorded included number of days to become juveniles, number of instars, length, dry weight, and mortality. Data from exposed shrimp was compared to the results of the control for each dispersant concentration. Corexit and Finasol exposure treatments of 5 mg/L and 10 mg/L showed significantly higher values for number of days and number of instars to reach juvenile status than values obtained from unexposed, control shrimp. Overall, mortality was higher in the Finasol treatments but the two dispersants did not respond significantly different from one another. Future studies are needed to determine the long term effects of dispersant exposure on all grass shrimp life stages and how any dispersant exposure impacts grass shrimp populations. Grass shrimp serve as excellent toxicity indicators of estuaries, and further studies will help to develop better oil spill mitigation techniques.