Grass shrimp (Palaemonetes pugio) are an important species from an ecological perspective because they serve as a link for energy transfer between trophic levels in the coastal food web. Grass shrimp are predators of meiofauna and small infaunal polychaetes, oligochaetes and nematodes. Grass shrimp are also consumed in large quantities by commercially important fishes and forage species, including spotted seatrout (Cynoscion nebulosus), red drum (Sciaenops ocellatus) and mummichogs (Fundulus heteroclitus).
The critical life stage of embryos through hatching will be selected for acute toxicity testing. Embryos from tissue cap stage will be exposed to water soluble fraction of oil, oil dispersants and mixtures for 12 days. The embryos will be kept in 20 ppt seawater and observed daily. Photographs and records of time of hatch will be taken for each day of the experiment. Risk analysis will be performed to determine the 50% risk of mortality (LC50) as well as 1% and 10% risk using toxtools and systat program for risk analysis. This program analysis will allow us to assess lower risk values than just the LC50.
As part of the overall effort in determining and quantifying the effects of Deep Horizon oil spill on estuarine environments in the Gulf of Mexico. This proposal would quantify the effects of oil and oil dispersant and their interaction on toxicity to grass shrimp (Palaemonetes pugio). The questions is to what extent if any do the oil dispersants affect the direct toxicity to Deep Horizon oil spill?
The objectives investigated would be:
- To determine the acute toxicity of oil from Deep Horizon
- To determine the acute toxicity of the oil dispersants used
- To determine combined effects between the two and to characterize them as synergism, antagonisms or response addition using toxic unit analysis