Partitioning of Persistent Organic Pollutants between Blubber and Blood of Wild Bottlenose Dolphins: Implications for Biomonitoring and Health

Abstract

Biomonitoring surveys of wild cetaceans commonly utilize blubber as a means to assess exposure to persistent organic pollutants (POPs), but the relationship between concentrations in blubber and those in blood, a better indicator of target organ exposure, is poorly understood. To define this relationship, matched blubber and plasma samples (n = 56) were collected from free-ranging bottlenose dolphins (Tursiops truncatus) and analyzed for 61 polychlorinated biphenyl (PCB) congeners, 5 polybrominated diphenyl ether (PBDE) congeners, and 13 organochlorine pesticides (OCPs). With the exception of PCB 209, lipid-normalized concentrations of the major POPs in blubber and plasma were positively and significantly correlated (R(2) = 0.828 to 0.976). Plasma concentrations, however, significantly increased with declining blubber lipid content, suggesting that as lipid is utilized, POPs are mobilized into blood. Compound- and homologue- specific blubber/blood partition coefficients also differed according to lipid content, suggesting POPs are selectively mobilized from blubber. Overall, these results suggest that with the regression parameters derived here, blubber may be used to estimate blood concentrations and vice versa. Additionally, the mobilization of lipid from blubber and concomitant increase in contaminants in blood suggests cetaceans with reduced blubber lipid may be at greater risk for contaminant-associated health effects.

Persistent organic pollutants (POPs) in blubber of common bottlenose dolphins (Tursiops truncatus) along the northern Gulf of Mexico coast, USA

“…Marine mammal blubber thickness and lipid content fluctuate across seasons (Pabst et al, 1999) and lipid normalization of POP concentrations reduces some of the variability associated with seasonal effects (reviewed in Kucklick et al, 2011). However, Yordy et al (2010a) determined that as lipid is mobilized from dolphin blubber to other tissues, the distribution of contaminants is not solely lipid-dependent. In California sea lions (Zalophus californianus), increases in POP concentrations within the blubber were observed as an animal's weight decreased, and lower chlorinated PCB congeners were lost at higher rates than other POP classes (Hall et al, 2008).…”

“…Additional studies that would increase the sample size during the cold season and repeated samples from the same individuals across seasons would provide further insight into fine-scale variations in POP profile patterns. Although Yordy et al (2010a) provided the first insights into the distribution and mobilization of POPs in different tissues, the study was limited to a sample size of four individual dolphins. A more in-depth study comparing POP levels within dolphins across seasons would identify the mobilization of contaminants among tissue types and provide insight into differences in POP levels observed in remote biopsy samples.…”

“…POPs, lipophilic chemicals that bioaccumulate in fatty tissues, are of particular concern for dolphins as these chemicals are biomagnified in higher trophic level organisms (J. Yordy et al, 2010;Yordy et al, 2010a). In fact, the bottlenose dolphin has been suggested as a sentinel species for examining regional trends of POPs for estuarine waters due to the species' year-round residency and top trophic position in estuarine ecosystems.…”

Lipid and fatty acid profiles of migrating Southern Hemisphere humpback whales Megaptera novaeangliae

“…Understanding the mobilisation of FA during times of increased metabolic demands, such as fasting, is essential for a detailed assessment of the increased environmental risk posed by mobilisation of co-entrained lipophilic organic pollutants. Once these pollutants are mobilised into the bloodstream, they have a heightened potential of reaching target sites of toxicity and causing adverse health effects (Bigsby et al 1997, Imbeault et al 2001, Martineau et al 2002, Yordy et al 2010.Analysis of FA profiles in Southern Hemisphere humpback whales is also important from an ecosystem management perspective to allow an understanding of Southern Ocean trophic interactions. Little is known about the specific foraging behaviour and prey preference of Southern Hemisphere humpback whales, but it is generally accepted that these populations feed almost exclusively on Antarctic krill Euphausia superba (Chittleborough 1965, Bannister & Hedley 2001, Paterson et al 2001.…”

Complex contaminant exposure in cetaceans: A comparative E‐Screen analysis of bottlenose dolphin blubber and mixtures of four persistent organic pollutants

“…Extracts were evaporated to dryness, reconstituted in a solvent mixture of 1:1 (volume fraction) DMSO:EtOH, and diluted in experimental media so that solvent concentrations did not exceed 0.01% and POPs were at the predicted blood level concentration for each individual dolphin. Blood concentrations were estimated from blubber concentrations as determined previously [25]. Details regarding the relationship used to estimate blood-level concentrations are provided as Supplemental Data.…”