Persistent organic pollutants in fat of three species of Pacific pelagic longline caught sea turtles: Accumulation in relation to ingested plastic marine debris.

In addition to eating contaminated prey, sea turtles may be exposed to persistent organic pollutants (POPs) from ingesting plastic debris that has absorbed these chemicals. Given the limited knowledge about POPs in pelagic sea turtles and how plastic ingestion influences POP exposure, our objectives were to: 1) provide baseline contaminant levels of three species of pelagic Pacific sea turtles; and 2) assess trends of contaminant levels in relation to species, sex, length, body condition and capture location. In addition, we hypothesized that if ingesting plastic is a significant source of POP exposure, then the amount of ingested plastic may be correlated to POP concentrations accumulated in fat. To address our objectives we compared POP concentrations in fat samples to previously described amounts of ingested plastic from the same turtles. Fat samples from 25 Pacific pelagic sea turtles [2 loggerhead (Caretta caretta), 6 green (Chelonia mydas) and 17 olive ridley (Lepidochelys olivacea) turtles] were analyzed for 81 polychlorinated biphenyls (PCBs), 20 organochlorine pesticides, and 35 brominated flame-retardants. The olive ridley and loggerhead turtles had higher ΣDDTs (dichlorodiphenyltrichloroethane and metabolites) than ΣPCBs, at a ratio similar to biota measured in the South China Sea and southern California. Green turtles had a ratio close to 1:1. These pelagic turtles had lower POP levels than previously reported in nearshore turtles. POP concentrations were unrelated to the amounts of ingested plastic in olive ridleys, suggesting that their exposure to POPs is mainly through prey. In green turtles, concentrations of ΣPCBs were positively correlated with the number of plastic pieces ingested, but these findings were confounded by covariance with body condition index (BCI). Green turtles with a higher BCI had eaten more plastic and also had higher POPs. Taken together, our findings suggest that sea turtles accumulate most POPs through their prey rather than marine debris.

Skin Transcriptomes of common bottlenose dolphins (Tursiops truncatus) from the northern Gulf of Mexico and southeastern U.S. Atlantic coasts.

Common bottlenose dolphins serve as sentinels for the health of their coastal environments as they are susceptible to health impacts from anthropogenic inputs through both direct exposure and food web magnification. Remote biopsy samples have been widely used to reveal contaminant burdens in free-ranging bottlenose dolphins, but do not address the health consequences of this exposure. To gain insight into whether remote biopsies can also identify health impacts associated with contaminant burdens, we employed RNA sequencing (RNA-seq) to interrogate the transcriptomes of remote skin biopsies from 116 bottlenose dolphins from the northern Gulf of Mexico and southeastern U.S. Atlantic coasts. Gene expression was analyzed using principal component analysis, differential expression testing, and gene co-expression networks, and the results correlated to season, location, and contaminant burden. Season had a significant impact, with over 60% of genes differentially expressed between spring/summer and winter months. Geographic location exhibited lesser effects on the transcriptome, with 23.5% of genes differentially expressed between the northern Gulf of Mexico and the southeastern U.S. Atlantic locations. Despite a large overlap between the seasonal and geographical gene sets, the pathways altered in the observed gene expression profiles were somewhat distinct. Co-regulated gene modules and differential expression analysis both identified epidermal development and cellular architecture pathways to be expressed at lower levels in animals from the northern Gulf of Mexico. Although contaminant burdens measured were not significantly different between regions, some correlation with contaminant loads in individuals was observed among co-expressed gene modules, but these did not include classical detoxification pathways. Instead, this study identified other, possibly downstream pathways, including those involved in cellular architecture, immune response, and oxidative stress, that may prove to be contaminant responsive markers in bottlenose dolphin skin.

Using cytochrome P4501A1 expression in liver and blubber to understand effects of persistent organic pollutant exposure in stranded Pacific Island cetaceans.

Elevated levels of persistent organic pollutants (POPs) have been reported in tropical Pacific Island cetaceans and their environment. In addition, recent health concerns in cetacean populations have warranted investigation into potential physiological effects from POP exposure for this region. Cytochrome P450 1A1 (CYP1A1) is a candidate for examining such effects. This well-studied biomarker of exposure and effect was examined in stranded cetacean liver using immunoblot (n = 39, 16 species) and blubber using immunohistochemistry (n = 23, 10 species). Paired tissue samples allowed for CYP1A1 comparisons not only between species but also within each individual animal to examine differences between tissue types. Liver CYP1A1 expression correlated positively and significantly with blubber concentrations of all POP categories (n = 39, p < 0.050) except octachlorostyrene and pentachlorobenzene (p > 0.100). Among Stenella species, liver CYP1A1 tissue expression was correlated negatively with the sum of all blubber layer endothelial cell CYP1A1 expression (n = 14, p = 0.049). Overall, elevated expression of liver CYP1A1 confirms its use as a biomarker of POP exposure to cetaceans stranded in the tropical Pacific basin.

Persistent organic pollutant concentrations in blubber of 16 species of cetaceans stranded in the Pacific Islands from 1997 through 2011.

Persistent organic pollutants (POPs) are toxic man-made chemicals that bioaccumulate and biomagnify in food webs, making them a ubiquitous threat to the marine environment. Although many studies have determined concentrations of POPs in top predators, no studies have quantified POPs in stranded cetaceans within the last 30 years around the Hawaiian Islands. A suite of POPs was measured in the blubber of 16 cetacean species that stranded in the tropical Pacific, including Hawai'i from 1997 to 2011. The sample set includes odontocetes (n=39) and mysticetes (n=3). Median (range) contaminant concentrations in ng/g lipid for the most representative species category (delphinids excluding killer whales [n=27]) are: 9650 (44.4-99,100) for ∑DDTs, 6240 (40.8-50,200) for ∑PCBs, 1380 (6.73-9520) for ∑chlordanes, 1230 (13.4-5510) for ∑toxaphenes, 269 (1.99-10,100) for ∑PBDEs, 280 (2.14-4190) for mirex, 176 (5.43-857) for HCB, 48.1 (<5.42-566) for ∑HCHs, 33.9 (<2.42-990) for ∑HBCDs, 1.65 (<0.435-11.7) for octachlorostyrene and 1.49 (<2.07-13.1) for pentachlorobenzene. ∑PCB concentrations in these Pacific Island cetaceans approach and sometimes exceed proposed toxic threshold values. Backward stepwise multiple regressions indicated the influence of life history parameters on contaminant concentrations when performed with three independent variables (species category, year of stranding, and sex/age class). No temporal trends were noted (p>0.063), but sex/age class influences were evident with adult males exhibiting greater contaminant loads than adult females and juveniles for ∑DDT, ∑PCBs, ∑CHLs, and mirex (p≤0.036). POP concentrations were lower in mysticetes than odontocetes for many compound classes (p≤0.003). p,p'-DDE/∑DDTs ratios were greater than 0.6 for all species except humpback whales, suggesting exposure to an old DDT source. These POP levels are high enough to warrant concern and continued monitoring.