MEPS 714:1-14 (2023)  -  DOI: https://doi.org/10.3354/meps14323

ABSTRACT: The Deepwater Horizon disaster resulted in the release of 490000 m³ of oil into the northern Gulf of Mexico. We quantified population consequences for pelagic cetaceans, including sperm whales, beaked whales and 11 species of delphinids. We used existing spatial density models to establish pre-spill population size and distribution, and overlaid an oil footprint to estimate the proportion exposed to oil. This proportion ranged from 0.058 (Atlantic spotted dolphin, 95% CI = 0.041-0.078) to 0.377 (spinner dolphin, 95% CI = 0.217-0.555). We adapted a population dynamics model, developed for an estuarine population of bottlenose dolphins, to each pelagic species by scaling demographic parameters using literature-derived estimates of gestation duration. We used expert elicitation to translate knowledge from dedicated studies of oil effects on bottlenose dolphins to pelagic species and address how density dependence may affect reproduction. We quantified impact by comparing population trajectories under baseline and oil-impacted scenarios. The number of lost cetacean years (difference between trajectories, summed over years) ranged from 964 (short-finned pilot whale, 95% CI = 385-2291) to 32584 (oceanic bottlenose dolphin, 95% = CI 13377-71967). Maximum proportional population decrease ranged from 1.3% (Atlantic spotted dolphin 95% CI = 0.5-2.3) to 8.4% (spinner dolphin 95% CI = 3.2-17.7). Estimated time to recover to 95% of baseline was >10 yr for spinner dolphin (12 yr, 95% CI = 0-21) and sperm whale (11 yr, 95% CI = 0-21), while 7 taxonomic units remained within 95% of the baseline population size (time to recover, therefore, as per its definition, was 0). We investigated the sensitivity of results to alternative plausible inputs. Our methods are widely applicable for estimating population effects of stressors in the absence of direct measurements.

KEY WORDS: Environmental impact assessment · Fecundity · Gulf of Mexico · Injury quantification · Marine mammals · Natural resource damage assessment · Population dynamics model · Survival

Full text in pdf format Information about this Feature Article Supplementary material

Cite this article as: Marques TA, Thomas L, Booth CG, Garrison LP and others (2023) Population consequences of the Deepwater Horizon oil spill on pelagic cetaceans. Mar Ecol Prog Ser 714:1-14. https://doi.org/10.3354/meps14323 Export citation Share:    Facebook - - linkedIn