Modeling population effects of the Deepwater Horizon oil spill on a long-lived species |
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| Authors: | Lori H Schwacke Tiago A Marques Len Thomas Cormac G Booth Brian C Balmer Ashley Barratclough Kathleen Colegrove Sylvain De Guise Lance P Garrison Forrest M Gomez Jeanine S Morey Keith D Mullin Brian M Quigley Patricia E Rosel Teresa K Rowles Ryan Takeshita Forrest I Townsend Todd R Speakman Randall S Wells Eric S Zolman Cynthia R Smith |
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| Institution: | 1. National Marine Mammal Foundation, Johns Island, South Carolina, USA;2. Centre for Research into Ecological and Environmental Modelling (CREEM), University of St Andrews, The Observatory, London, UK;3. SMRU Consulting, Scottish Oceans Institute, East Sands, University of St Andrews, St Andrews, UK;4. National Marine Mammal Foundation, San Diego, California, USA;5. Zoological Pathology Program, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Brookfield, Illinois, USA;6. Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, Connecticut, USA;7. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida, USA;8. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Pascagoula, Mississippi, USA;9. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Lafayette, Louisiana, USA;10. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, Silver Spring, Maryland, USA;11. Bayside Hospital for Animals, Fort Walton Beach, Florida, USA;12. Chicago Zoological Society's Sarasota Dolphin Research Program, c/o Mote Marine Laboratory, Sarasota, Florida, USA |
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| Abstract: | The 2010 Deepwater Horizon (DWH) oil spill exposed common bottlenose dolphins (Tursiops truncatus) in Barataria Bay, Louisiana to heavy oiling that caused increased mortality and chronic disease and impaired reproduction in surviving dolphins. We conducted photographic surveys and veterinary assessments in the decade following the spill. We assigned a prognostic score (good, fair, guarded, poor, or grave) for each dolphin to provide a single integrated indicator of overall health, and we examined temporal trends in prognostic scores. We used expert elicitation to quantify the implications of trends for the proportion of the dolphins that would recover within their lifetime. We integrated expert elicitation, along with other new information, in a population dynamics model to predict the effects of observed health trends on demography. We compared the resulting population trajectory with that predicted under baseline (no spill) conditions. Disease conditions persisted and have recently worsened in dolphins that were presumably exposed to DWH oil: 78% of those assessed in 2018 had a guarded, poor, or grave prognosis. Dolphins born after the spill were in better health. We estimated that the population declined by 45% (95% CI 14–74) relative to baseline and will take 35 years (95% CI 18–67) to recover to 95% of baseline numbers. The sum of annual differences between baseline and injured population sizes (i.e., the lost cetacean years) was 30,993 (95% CI 6607–94,148). The population is currently at a minimum point in its recovery trajectory and is vulnerable to emerging threats, including planned ecosystem restoration efforts that are likely to be detrimental to the dolphins’ survival. Our modeling framework demonstrates an approach for integrating different sources and types of data, highlights the utility of expert elicitation for indeterminable input parameters, and emphasizes the importance of considering and monitoring long-term health of long-lived species subject to environmental disasters. Article impact statement: Oil spills can have long-term consequences for the health of long-lived species; thus, effective restoration and monitoring are needed. |
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| Keywords: | dolphin expert elicitation health assessment marine mammal oil spill population model slow-living species análisis de salud delfín derrame de petróleo especie longeva información de expertos mamífero marino modelo poblacional |
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