A novel approach to contaminant-related health assessment in marine mammals

Background/Question/Methods

Environmental pollutants in marine mammals have been correlated with changes in endocrine hormones, such as testosterone and cortisol, which are commonly associated with reproductive health and stress response. Despite many toxicological studies characterizing differences in serum hormone levels with contaminant concentrations, existing research has been unable to link contaminant exposure to changes in demographic parameters, i.e. vital rates. These studies typically target up to a handful of known chemicals without examining uncharacterized or unknown, potentially toxic contaminants of emerging concern (CECs). As such, standard techniques do not allow for the early detection of CECs before they pose a significant health risk. An innovative technique utilizing comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) enables the detection of contaminants with a non-targeted analytical approach. Furthermore, quantification of endocrine hormones in blubber has the ability to assess endocrine health in free-ranging marine mammals. We integrated these two newly developed molecular methods for the first time to validate the use of this approach for contaminant risk-assessment in marine mammals. We identified a broad range of contaminants and compared contaminant concentrations with hormone biomarkers in bycaught male short-beaked common dolphins (Delphinus delphis) of known reproductive status in the Southern California Bight.

Results/Conclusions

Non-targeted contaminant analysis of blubber identified a broad range of known and unknown contaminants in bycaught short-beaked common dolphins (Delphinus delphis). Preliminary analysis confirmed the presence of legacy contaminants, such as PCBs and DDT, highlighting their continued persistence in wildlife. We also detected both anthropogenic and naturally derived polybrominated diphenyl ethers (PBDEs). For example, Me-O PBDE 4Br, a naturally occurring compound structurally similar to anthropogenic PBDE congeners, was characterized. This compound is known to biomagnify in marine systems but the source of this compound in the southern California region is unknown as is its health risk. These findings highlight the need for further research on both anthropogenic compounds and halogenated natural products and their effect on marine marine mammals. The application of this novel approach to marine mammal contaminant risk-assessment will allow for the identification of newly emerging CECs in the southern California region and a more complete assessment of the total body burden of contaminants in marine mammals. When combined with other known diagnostics of endocrine and cellular function, this approach can provide new information on the mechanistic link between contaminant exposure and population level health in free-ranging marine mammals.