Abstract

Marine mammals are effective indicators of marine pollution due to their longevity, high trophic position, and large blubber stores that lead to the accumulation of high concentrations and diverse classes of nonpolar, persistent organic pollutants.¹ Anthropogenic contaminants such as DDT and PCBs are known to contribute to an array of health effects including impaired reproduction² and immunosuppression in marine mammals^3,4. Routine screening methods used to assess marine mammal contaminant loads typically consist of a targeted list of well-recognized, legacy compounds. However, many unknown or unrecognized anthropogenic contaminants with the potential to cause physiological harm fall outside of routine ecosystem monitoring efforts. In addition, naturally occurring halogenated natural products (HNPs) produced by marine invertebrates exhibit bioaccumulative properties, may confound toxicological studies of anthropogenic chemicals, and are rarely targeted in marine studies.⁵ An innovative non-targeted analytical method using two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC TOF-MS) can characterize thousands of known and unknown anthropogenic and natural compounds through enhanced chromatographic resolution and improved sensitivity. Mass spectra can then be identified by matching to reference standards, searching against existing libraries of mass spectra, or manual interpretation. Eighty-six anthropogenic contaminants and 54 HNPs not routinely targeted in environmental surveys were previously identified in an Atlantic common dolphin (Delphinus delphis) using this analytical approach.⁵

The Southern California Bight (SCB) extends from Point Conception (Santa Barbara County) to Cabo Colonett, Mexico, and is prone to large-scale ocean contamination from a variety of sources.⁶ Toxic algal blooms of Pseudo-nitzschia spp. produce high concentrations of particulate domoic acid (DA) and are a repetitive phenomenon along coastal regions of the SCB.⁷ Fatal stranding incidents of long-beaked common dolphins (Delphinus capensis), short-beaked common dolphins (Delphinus delphis), and California sea lions (Zalophus californianus) have been attributed to DA poisoning.^8,9 Other species including Risso's dolphin (Grampus griseus) and the Pacific harbor seal (Phoca vitulina) have not been documented to experience lethal health consequences with exposure to toxic blooms of DA. Using non-targeted mass spectrometry, a full inventory of halogenated, bioaccumulative organic compounds is being generated from archived blubber samples from these five marine mammal species. The contaminant profiles generated for each indicator species will be compared to examine associations between exposure to bioaccumulative chemicals and susceptibility to domoic acid toxicosis. The magnitude and multitude of compounds found across the archived blubber samples for each species will also be compared against a profile for the common bottlenose dolphin (Tursiops truncatus)¹⁰ to identify the best sentinel species among the six for future monitoring efforts in the SCB. Additionally, the contaminant profiles and mass spectra generated in this study will evaluate the distribution of bioaccumulative contaminants across southern California marine mammal species to identify emerging and previously unrecognized chemicals that may pose a significant ecological risk.

Acknowledgements

This project would not be possible without the financial support of Prescott Award Number NA14NMF4390177 from the National Oceanic and Atmospheric Association. We are grateful to Kerri Danil for assistance in providing the samples and Dr. Wayne Lao and David Tsukada of the Southern California Coastal Water Resources Project for performing the blubber oil extractions.

* Presenting author
⁺ Student presenter

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