The overall scope of changes to the Gulf of Mexico ecosystem in the wake of the DWH oil spill is immeasurable.
Bottlenose dolphins in bays, sounds, and estuaries are apex predators in coastal food webs, and would likely suffer if the number and/or quality of fish and crustacean prey dropped due to oil exposure. In previous dolphin studies in LA and MS, researchers found both live and dead dolphins that were underweight compared to healthy dolphins of the same length. There are also new studies demonstrating that fatty acids in animals’ blood can be used to monitor other aspects of dolphin health.
The CARMMHA Dietary Assessment project has two main objectives: 1) to understand how dolphin diets may have changed during and after the DWH oil spill, and 2) to measure fatty acids in dolphin blood samples since the spill and look for correlations with other related health effects.
To characterize dolphin diets since the spill, the Dauphin Island Sea Laboratory (DISL) will work with the Louisiana Department of Wildlife and Fisheries (LDWF) to measure stable isotopes from typical dolphin prey species (fish and crustaceans). The team will then compare them to stable isotopes from archived dolphin samples and samples from CARMMHA Field projects to characterize what dolphins have been eating since the DWH oil spill and whether that diet has changed over time.
Similarly, scientists from NOAA’s National Centers of Coastal Ocean Science (NCCOS) will compare the levels of fatty acids (the molecules found in cellular membranes) in archived samples over time since the spill with the new samples collected by the CARMMHA Field projects. CARMMHA veterinarians will then work with NCCOS to identify any relationships between fatty acid signatures and other health parameters from the assessments and identify how any changes in fatty acids may impact overall health prognoses.
DISL, LDWF, and NCCOS have begun cataloging the archived samples available for stable isotope and fatty acid analysis, in order to finalize their study design. They are also working with the field personnel to identify the types of samples they’ll need and where they’d like to sample from in Barataria Bay and Dauphin Island.