Abstract
Legacy persistent organic pollutants (POPs) were measured in blubber samples collected from 196 common bottlenose dolphins (Tursiops truncatus) from 2000 to 2016 in the Sarasota Bay, Florida, ecosystem. Legacy POPs included polychlorinated biphenyl congeners (ΣPCB; sum of 37 congeners or congener groups), dichloro-diphenyl-trichloroethane (DDT) and transformation products (ΣDDT), chlordane and related compounds (ΣChlor), mirex, polybrominated diphenyl ether congeners (ΣPBDE, sum of five congeners), dieldrin and hexachlorobenzene (HCB). All POP compounds or compound groups declined in dolphin blubber over the study period. POP classes declined at different rates within classifications (sex, adult or calf). For example, dieldrin decline in male dolphins was greatest (−13% per year) while HCB decline was lower (−6.3% per year). For individual POP classes, rates of decline depended on classification. For example, ΣPCB, the POP class present at the highest concentration relative to other POPs, declined at −8.4, −7.8, and −5.6% per year in adult females, adult males and calves, respectively. Overall POP declines were highest in adult males and lowest in calves. Declines in POP concentration with time based on individual dolphins resampled at different time points were consistent with declines calculated based on yearly or biennial cross-sections taken from 2000 through 2016. Overall rates of decline in Sarasota Bay bottlenose dolphins were like declines seen for Great Lakes fish and about twice the rate of decline observed in arctic temporal trend data sets. POP trends appear to have leveled off since 2009 in Sarasota Bay dolphins. For example, ΣPCBs in calves appear to have stabilized at 21 mg/kg lipid. Recent published work on delphinids with blubber concentrations spanning those observed in the present work suggest that levels of legacy POPs currently observed in Sarasota dolphins may suppress population growth. Results from this study confirm the need for continued monitoring of POPs in the Sarasota Bay bottlenose dolphin population to see if concentrations are continuing to fall or have indeed plateaued.
Highlights
Legacy persistent organic pollutants (POPs) are stable, bioaccumulative, and toxic chemicals that have been largely either regulated or phased out of production
A study modeling the effects of polychlorinated biphenyls (PCBs) on killer whale calf mortality and immunosuppression showed that more than 50% of global killer whale populations are at risk of collapse given current PCB blubber concentrations (Desforges et al, 2018)
The objective of this study is to document the changes with time of legacy persistent organic pollutants (POPs) in the blubber of the well-studied, long-term resident population of common bottlenose dolphins (Tursiops truncatus) living in Sarasota Bay, Florida, United States
Summary
Legacy persistent organic pollutants (POPs) are stable, bioaccumulative, and toxic chemicals that have been largely either regulated or phased out of production. Because of high lipophilicity (log Kow > 3 L/kg) and resistance to metabolism, POPs accumulate and biomagnify in food webs resulting in the highest concentrations at the top of the food web in animals such as the bottlenose dolphin. Due to their potential for bioaccumulation, POP concentrations were observed in excess of 100 mg/kg lipid in delphinid blubber, such as marine mammal-eating killer whales in the Northwest Pacific Ocean, and common bottlenose dolphins living near a PCB-contaminated site near Brunswick, Georgia, United States (Krahn et al, 2009; Kucklick et al, 2011). Populations at greatest risk of decline included transient killer whales in the Northeast Pacific Ocean feeding on marine mammals (Ross et al, 2000)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
