Preliminary ecotoxicological data on C type killer whale (Orcinus orca) from Terra Nova Bay (Antarctica): Molecular biomarkers and persistent organic contaminants

Among killer whale forms, the type C is a fish eating form and the most common in the Ross Sea. In the austral summer 2015 a study to evaluate the toxicological hazard C type killer whale faces in the Antarctic ecosystem was conducted in Terra Nova Bay. Seven biopsy samples were collected from adult specimens (5 males and 2 females) in the surroundings of the Italian research station Mario Zucchelli by means of remote dart sampling from the pack ice.The accumulation levels of persistent organic pollutants (POPs), including legacy (DDTs, PCBs, HCB) and emerging POPs (PBDEs) were measured. Moreover, the protein expression of cythocrome P450 (CYP1A and 2B) and the mRNA level variations of the peroxisome proliferator-activated receptors α and γ (PPARαγ) and the Estrogen Receptor α (ERα) were evaluated. PPARs are ligand-dependent nuclear receptors involved in lipid homeostasis, inflammation and adipogenesis, and ERα is involved in the estrogen pathways and induced by estrogen-like exogenous compounds such as OCs and PBDEs. PCBs (twenty-one ortho PCB congeners), DDTs, HCB and PBDEs (fourteen congeners from tri- to deca-substituted) were analyzed on freeze-dried blubber biopsy samples by GC-qMS. The protein expression was evaluated by Western Blot and the mRNA levels were quantified by quantitative Real-Time PCR. The average abundance pattern for the contaminants was DDTs>PCBs>HCB>PBDEs. Contaminant levels resulted to be lower when compared to existing data from Antarctic type C killer whales from Ross Sea (McMurdo Sound) and those reported for the fish-eating resident or offshore killer whales, or feeding at higher trophic levels. Both protein and gene expression biomarker responses were correlated to contaminant levels to evaluate the biological responses to POPs. A comprehensive assessment of the ecotoxicological status of Ross Sea killer whale will be undertaken by considering the satellite tracking and feeding ecology data gained on the same samples.