Marine fishes face an array of environmental contaminants that may reduce their ability to perform in ecological situations. The effects of factors producing direct mortality in populations, such as fishing, are often easier to quantify than sublethal impacts. The overall objective of this proposal is to determine the toxicity of individual dispersants (e.g., NALCO's COREXIT 9500) and contaminants including Louisiana Sweet Crude oil and mixtures of dispersants and contaminants on the fish fauna of deep waters. Lethal concentrations (LC50) trials will be performed on selected juvenile fishes.
The Florida pompano has been used previously and will be used as our initial model carangid species selected to test for toxicity of combinations of Louisiana Sweet Crude and Corexit 9500. As many sublethal effects of pollutants are difficult to quantify, this work is preparatory to future research using a respirometry-based approach to directly measure how swimming performance is impacted by dispersants. The Florida pompano Trachinotus carolinus was chosen as our initial model species for assessment of acute and sublethal effects of exposure to petroleum and dispersants because the species occurs in the vicinity of transport pipelines and deep-water wells in the Gulf of Mexico.
The greater amberjack, Seriola dumerili is our second species of interest. It is a commercially and recreationally important reef-associated species. It is the largest of the amberjack species but only one of several carangids that are abundant in offshore waters adjacent to Louisiana. Initial LC50 range-finding tests will be conducted on Florida pompano with six chemical concentrations of crude oil ranging from 0 to 5000 ppm of oil. Fishes will be exposed to water accommodated fractions (WAFs). Oil will be mixed with 2 liters of seawater and stirred @ 200 rpm for 24 hrs and the WAF decanted from the oil-water mixture and used for exposures. In the second and third trials we will select concentrations to ensure that we meet test assumptions for determining the LC values with the Environmental Protection Agency’s Probit Analysis Program, Version 1.5 (Lazaorchak 1994).
Following the LC50 tests, two behavior and recovery experiments will be conducted in preparation for future swimming experiments to identify sublethal concentrations of chemical(s) from which juvenile Florida pompano can apparently recover. Behavior and mortality will be recorded periodically during the 24-h exposure, as well as during a 15-h recovery period in sea water containing no chemical(s). At 24 h, fish swimming behavior will be videotaped for later analyses and the remaining fish euthanized. These results will provide a clearer understanding of the possible ecological consequences from spills or leakage in the marine environment to offshore and coastal juveniles fishes.