Concentrations and profiles of organochlorine contaminants in North Pacific resident and transient killer whale (Orcinus orca) populations

Distinctive patterns and low concentrations of persistent organic pollutants in Northwestern Pacific killer whales (Orcinus orca)

Persistent organic pollutants (POPs) in killer whale (Orcinus orca) populations in the Northwestern Pacific Ocean are much less studied compared to the Northeastern Pacific and North Atlantic populations. The objective of this study was to address that knowledge gap by analysis of biopsy samples obtained as part of studies of killer whale feeding and habitat use in coastal waters of the Russian Far East. Skin/blubber biopsies collected from 26 killer whales at five locations in coastal waters of the Kamchatka Peninsula (Avacha Gulf), North Kuril Islands, Western and Northern Sea of Okhotsk, and further north in Chukotka, between 2012 and 2016, were analysed for a suite of organochlorine pesticides and byproducts (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). DDT related compounds and PCBs were the most prominent POPs in the biopsy samples with geometric mean concentrations in the 5 regions ranging 34.4 to 161 ng/g (wet weight, ww) for total DDT and 8.10 to 58.5 ng/g ww for total PCBs. Principal components analysis using the data for OCPs showed that key contributors to the geographic differences were DDT isomers as well as the more volatile OCPs, hexachlorobutadiene and pentachlorobenzene. The concentrations of individual OCPs and PCBs agreed with previous reports for female killer whales sampled in the Northwestern Pacific region in 2002-2004 but were up to 180-fold lower than reported in transient males. Overall concentrations of POPs in killer whales in this region are among the lowest for killer whale populations in the northern hemisphere.

Spatial and seasonal foraging patterns drive diet differences among north Pacific resident killer whale populations

Highly social top marine predators, including many cetaceans, exhibit culturally learned ecological behaviours such as diet preference and foraging strategy that can affect their resilience to competition or anthropogenic impacts. When these species are also endangered, conservation efforts require management strategies based on a comprehensive understanding of the variability in these behaviours. In the northeast Pacific Ocean, three partially sympatric populations of resident killer whales occupy coastal ecosystems from California to Alaska. One population (southern resident killer whales) is endangered, while another (southern Alaska resident killer whales) has exhibited positive abundance trends for the last several decades. Using 185 faecal samples collected from both populations between 2011 and 2021, we compare variability in diet preference to provide insight into differences in foraging patterns that may be linked with the relative success and decline of these populations. We find broad similarities in the diet of the two populations, with differences arising from spatiotemporal and social variability in resource use patterns, especially in the timing of shifts between target prey species. The results described here highlight the importance of comprehensive longitudinal monitoring of foraging ecology to inform management strategies for endangered, highly social top marine predators.

Revised taxonomy of eastern North Pacific killer whales (Orcinus orca): Bigg's and resident ecotypes deserve species status

Killer whales (Orcinus orca) are currently recognized as a single ecologically and morphologically diverse, globally distributed species. Multiple morphotypes or ecotypes have been described, often associated with feeding specialization, and several studies have suggested taxonomic revision to include multiple subspecies or species in the genus. We review the ecological, morphological and genetic data for the well-studied 'resident' and Bigg's (aka 'transient') ecotypes in the eastern North Pacific and use quantitative taxonomic guidelines and standards to determine whether the taxonomic status of these killer whale ecotypes should be revised. Our review and new analyses indicate that species-level status is justified in both cases, and we conclude that eastern North Pacific Bigg's killer whales should be recognized as Orcinus rectipinnus (Cope in Scammon, 1869) and resident killer whales should be recognized as Orcinus ater (Cope in Scammon, 1869).

Varying Diet Composition Causes Striking Differences in Legacy and Emerging Contaminant Concentrations in Killer Whales across the North Atlantic

Lipophilic persistent organic pollutants (POPs) tend to biomagnify in food chains, resulting in higher concentrations in species such as killer whales (Orcinus orca) feeding on marine mammals compared to those consuming fish. Advancements in dietary studies include the use of quantitative fatty acid signature analysis (QFASA) and differentiation of feeding habits within and between populations of North Atlantic (NA) killer whales. This comprehensive study assessed the concentrations of legacy and emerging POPs in 162 killer whales from across the NA. We report significantly higher mean levels of polychlorinated biphenyls (PCBs), organochlorine pesticides, and flame retardants in Western NA killer whales compared to those of Eastern NA conspecifics. Mean ∑PCBs ranged from ∼100 mg/kg lipid weight (lw) in the Western NA (Canadian Arctic, Eastern Canada) to ∼50 mg/kg lw in the mid-NA (Greenland, Iceland) to ∼10 mg/kg lw in the Eastern NA (Norway, Faroe Islands). The observed variations in contaminant levels were strongly correlated with diet composition across locations (inferred from QFASA), emphasizing that diet and not environmental variation in contaminant concentrations among locations is crucial in assessing contaminant-associated health risks in killer whales. These findings highlight the urgency for implementing enhanced measures to safely dispose of POP-contaminated waste, prevent further environmental contamination, and mitigate the release of newer and potentially harmful contaminants.

The first full-congener analysis of 209 polychlorinated biphenyls (PCBs) in the blubber of short-finned pilot whales (Globicephala macrorhynchus) stranded along the coast of Savu Island, Indonesia

Short-finned pilot whales (SFPW) are a group of cetaceans found globally in tropical and temperate seas and are commonly stranded in the group, but the reason behind their stranding is still unknown. No detailed information on the contamination status and bioaccumulation of halogenated organic compounds, including polychlorinated biphenyls (PCBs), in the SFPW from Indonesian waters has been reported. Therefore, we analyzed all 209 PCB congeners in the blubber of 20 SFPW specimens stranded along the coast of Savu Island, East Nusa Tenggara, Indonesia, in October 2012 to explain the status of contamination, congener profiles, potential risk of PCBs to cetaceans, and the determination of unintentionally produced PCBs (u-PCBs) in the blubber of SFPW. Concentrations of Σ209PCBs, Σ7in-PCBs, Σ12dl-PCBs, and Σ21u-PCBs were between 48 and 490 (mean:240 ± 140), 22-230 (110 ± 60), 2.6-38 (17 ± 10), and 1.0-13 (6.3 ± 3.7) ng g^-1 lipid weight (lw), respectively. Congener-specific profiles of PCBs among sex and estimated age groups were observed; relatively high proportions of tri-to penta-CBs in juveniles and highly chlorinated recalcitrant congeners in structure-activity groups (SAGs) in sub-adult females were noted. The estimated toxic equivalency (TEQs) value for dl-PCBs ranged from 2.2 to 60 TEQ_WHO pg/g lw, with juveniles containing high TEQ values than sub-adults and adults. Although the TEQs and concentrations of PCBs in SFPW stranded along Indonesian coasts were lower than those reported for similar whale species from other North Pacific regions, further research is needed to assess the long-term impact of halogenated organic pollutants on their survival and health.

Impacts of endocrine disrupting chemicals on reproduction in wildlife and humans

Endocrine disrupting chemicals (EDCs) are ubiquitous in aquatic and terrestrial environments. The main objective of this review was to summarize the current knowledge of the impacts of EDCs on reproductive success in wildlife and humans. The examples selected often include a retrospective assessment of the knowledge of reproductive impacts over time to discern how the effects of EDCs have changed over the last several decades. Collectively, the evidence summarized here within reinforce the concept that reproduction in wildlife and humans is negatively impacted by anthropogenic chemicals, with several altering endocrine system function. These observations of chemicals interfering with different aspects of the reproductive endocrine axis are particularly pronounced for aquatic species and are often corroborated by laboratory-based experiments (i.e. fish, amphibians, birds). Noteworthy, many of these same indicators are also observed in epidemiological studies in mammalian wildlife and humans. Given the vast array of reproductive strategies used by animals, it is perhaps not surprising that no single disrupted target is predictive of reproductive effects. Nevertheless, there are some general features of the endocrine control of reproduction, and in particular, the critical role that steroid hormones play in these processes that confer a high degree of susceptibility to environmental chemicals. New research is needed on the implications of chemical exposures during development and the potential for long-term reproductive effects. Future emphasis on field-based observations that can form the basis of more deliberate, extensive, and long-term population level studies to monitor contaminant effects, including adverse effects on the endocrine system, are key to addressing these knowledge gaps.

Passive acoustic monitoring of killer whales (Orcinus orca) reveals year-round distribution and residency patterns in the Gulf of Alaska

Killer whales (Orcinus orca) are top predators throughout the world's oceans. In the North Pacific, the species is divided into three ecotypes-resident (fish-eating), transient (mammal-eating), and offshore (largely shark-eating)-that are genetically and acoustically distinct and have unique roles in the marine ecosystem. In this study, we examined the year-round distribution of killer whales in the northern Gulf of Alaska from 2016 to 2020 using passive acoustic monitoring. We further described the daily acoustic residency patterns of three killer whale populations (southern Alaska residents, Gulf of Alaska transients, and AT1 transients) for one year of these data. Highest year-round acoustic presence occurred in Montague Strait, with strong seasonal patterns in Hinchinbrook Entrance and Resurrection Bay. Daily acoustic residency times for the southern Alaska residents paralleled seasonal distribution patterns. The majority of Gulf of Alaska transient detections occurred in Hinchinbrook Entrance in spring. The depleted AT1 transient killer whale population was most often identified in Montague Strait. Passive acoustic monitoring revealed that both resident and transient killer whales used these areas much more extensively than previously known and provided novel insights into high use locations and times for each population. These results may be driven by seasonal foraging opportunities and social factors and have management implications for this species.

Distribution and risk assessment of hexachlorobutadiene, pentachloroanisole, and chlorobenzenes in sediment and wild fish from a region affected by industrial and agricultural activities in South China

Hexachlorobutadiene, pentachloroanisole, and chlorobenzenes are regulated to control their release into the environment. There is little information regarding the distribution and risks of these pollutants in Chinese rivers. Therefore, we selected a prosperous agricultural and industrial region in South China as our study area and investigated the contamination profiles and risks of these pollutants in sediment and fish tissue samples. The results showed that, when compared with their levels in sediment, these lipophilic pollutants tended to accumulate in fish tissues in the following order: liver > brain > muscle. Some trichlorobenzene was found to be the result of reductive dechlorination of higher chlorinated benzenes. Hexachlorobutadiene and hexachlorobenzene could pose medium risks at certain sampling sites, but in general, almost no risk was found to the ecosystem. When the estimated daily human intakes of analytes through fish consumption were calculated for different age groups, the results suggested the analytes were unlikely to be a serious health concern for human. Our results could be used to update the existing data on the occurrence of these pollutants in the aquatic environment and to provide information for further pollution control by the local government.

The endocrine disruptor hexachlorobenzene can cause oxidative damage in the testis of mice

Hexachlorobenzene is a widespread endocrine disruptor. However, the effect of hexachlorobenzene on the reproductive toxicity of male animals is not described in detail. To investigate the toxic effects of hexachlorobenzene in mouse testes, hexachlorobenzene (100, 400 and 1,600 mg/kg) is fed to mice. The morphology of the testes was analysed by haematoxylin and eosin staining. We also investigated the expression of biomarkers for oxidative stress. Database screening identified proteins that interact with hexachlorobenzene and the aryl hydrocarbon receptor, a weak ligand of hexachlorobenzene. Gene enrichment analysis and protein-protein interaction analyses were also performed. Real-time PCR detected the expression levels of the aryl hydrocarbon receptor in four different stages of testicular cells. We identified significantly increased activity levels of superoxide dismutase (p < 0.05) and catalase (p < 0.05) in mouse testes that had been subjected to oxidative damage. The cell thickness and the number of cell layers in the seminiferous tubules had decreased by varying degrees after the hexachlorobenzene treatment. Particularly, cytokines and proteins involved in transcriptional regulation showed enrichment. The highest levels of aryl hydrocarbon receptor expression were detected in the spermatocytic cell line. Hexachlorobenzene exposure caused testicular damage in mice. The toxicity characteristics of hexachlorobenzene were not dose-dependent.

Application of endocrine biomarkers to update information on reproductive physiology in gray whale (Eschrichtius robustus)

Most of our knowledge on reproductive biology of gray whales dates back to scientific research conducted during commercial whaling in the late 1950s and 1960s. The goal of the present study was to provide updated insights on reproductive physiology of gray whales, using progesterone and testosterone as biomarkers. We measured hormone concentrations using enzyme immunoassay (EIA) techniques in blubber biopsies collected from 106 individual whales from March to November over a span of 12 years (2004-2016) between California and Alaska. We found testosterone concentrations in males to increase significantly with age (P = 0.03). Adult males showed significantly elevated testosterone concentrations when sampled in the fall compared to the summer (P = 0.01), likely indicating physiological preparation for mating. We measured testosterone concentrations in females of different age classes, but no statistical differences were found. We found significantly higher progesterone concentrations in pregnant females compared to non-pregnant females and adult males (P< 0.001), indicating progesterone is a valid biomarker for pregnancy in gray whales. Both female and male calves had elevated progesterone concentrations, suggesting maternal transfer via lactation. We fit a mixture of two normal distributions to progesterone data from all non-calf females to identify clusters of high and low progesterone and estimated the probability of being pregnant for whales of unknown reproductive status. With this approach we identified likely pregnant and non-pregnant animals. This study represents an important milestone on reproductive profiles in this population, that can be used to estimate more accurate and precise reproductive parameters to be used for better understanding population dynamics of gray whales.