Trends of persistent organic pollutants in three dolphin species from the Southern California bight during 1990–2012

The Southern California Bight (SCB) is polluted with persistent organic pollutants (POPs) due to long-term industrialization and urban development, yet documentation of top-level marine predator exposure to these contaminants is limited. We characterized POP exposure for three SCB dolphin species by analyzing dichlorodiphenyltrichloroethanes (DDTs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in blubber from common bottlenose dolphins (Tursiops truncatus, n = 37), short-beaked (Delphinus delphis delphis, n = 62), and long-beaked (Delphinus delphis bairdii, n = 46) common dolphins from 1990 to 2012. Temporal, spatial, sex, age, maturity status, and ecotype trends in contaminant concentrations were assessed using multilinear regression models. Short-beaked common dolphins exhibited decreasing POP concentrations temporally, consistent with reduced environmental inputs following regulatory bans. Short-beaked common dolphins from the SCB had higher ΣDDT and ΣPBDE concentrations than those from central California, indicating persistent regional differences. Significant age-sex interactions were observed for all three contaminant classes in both short- and long-beaked common dolphins, reflecting sex-specific bioaccumulation patterns. Long-beaked common dolphins exhibited the highest ΣDDT (∼110 μg/g lipid weight), ΣPCB (∼18 μg/g lipid weight), and ΣPBDE (∼7.3 μg/g lipid weight) concentrations reported globally. Elevated ΣPBDE levels were also observed in both coastal and offshore common bottlenose dolphin ecotypes, as well as in SCB short-beaked common dolphins. These findings demonstrate that exposure to POPs remains elevated among SCB top marine predators, further highlighting the continued value of dolphins as sentinel species for monitoring legacy and emerging contaminants in coastal ecosystems.