Abstract:
This is the first study of PCB levels and life history parameters in long-finned pilot whales (Globicephala melas) of the Southern Hemisphere. The study material was collected from mass strandings around New Zealand. PCB levels in pilot whale blubber ranged from 33 to 931 ng/g (parts per billion) with a mean PCB burden of 311 ng/g. This is 2-3 orders of magnitude lower than in Northern Hemisphere pilot whales. Comparison of PCB levels in various New Zealand cetaceans reveals trophic level and feeding proximity to the coast are major determinants in the accumulation of PCB residues.
The life history parameters of age, growth and reproductive status in long-finned pilot whales off New Zealand closely match those of Northern Hemisphere populations.
Both male and female New Zealand long-finned pilot whales exhibit distinct PCB age trends. In males, PCB levels increase linearly with age throughout life. Females show on increase prior to maturity, then a decrease throughout parturition due to unloading of PCBs to their calves, and then increase again with old age. The female PCB age trend indicates a limited period of active parturition in females.
It is hypothesized that the high variability of PCB levels observed in calves is due to the presence of three male first-born calves in the sample with exceptionally high PCB body burdens and distinct PCB congener profiles. Despite high variability in PCB levels, PCB profiles were remarkably consistent in all individuals sampled, and in other New Zealand open ocean cetaceans, pointing to exposure to a common and distant PCB contaminant source. An abundance of the more volatile, lower chlorinated PCB congeners in the PCB profiles suggests atmospheric transport is the likely mode of dissemination of these contaminants into the Southern Ocean.
Based on data from this and Northern Hemisphere studies, long-finned pilot whales appear to exhibit a reduced capacity to metabolise meta-para as well as certain ortho-meta non-substituted PCB congeners.
The relatively low 2,3,7,8 TCDD-Toxic Equivalent (TEQ) concentrations determined in this study appear to be below levels at which adverse effects might be expected. Still, a PCB dose-effect relationship and marine mammal sensitivity to these compounds has yet to be determined.
Findings of this study suggest that PCBs can be useful tracers of age-related reproductive parameters in open ocean cetaceans of the Southern Ocean. Also this study shows that Southern Ocean open ocean cetaceans are suitable bioindicators for the long-term monitoring of persistent pollutants and could be a novel tool for investigating baseline biological parameters at low contaminant exposure levels.
