Dietary Assessment

The overall scope of changes to the Gulf of Mexico ecosystem in the wake of the DWH oil spill is immeasurable.

Co-PIs: Ruth Carmichael (Dauphin Island Sea Lab, University of South Alabama), Maggie Broadwater (NOAA/NOS National Centers for Coastal Ocean Science);

Key Collaborators: Mandy Tumlin (LDWF), Carl Cloyed (Dauphin Island Sea Lab)

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.

Progress Summary

September 5th, 2019 – DISL, LDWF, and NCCOS have completed stable isotope analysis of dolphin prey (fish and shrimp) collected from Barataria Bay, as well as fatty acid analysis of dolphin serum. The dietary team has completed mixing model analyses to compare trends in dolphin prey over time and by site. The dietary team has also begun collaborations with researchers outside the CARMMHA team to investigate relationships between dolphin prey trends and movement patterns.