In 2013, a mass mortality event resulted in the deaths of approximately three million short-tailed shearwaters (Ardenna tenuirostris) along the east coast of Australia. As pelagic apex predators within their marine ecosystems and extensive migratory routes, these seabirds may serve as a bioindicator for assessing global ocean pollution. This study evaluates the current level of marine pollution by quantifying polychlorinated biphenyls (PCBs) and toxic metals in the liver tissue of short-tailed shearwaters. A micro-QuEChERS method was successfully developed and optimised for the extraction of 17 PCBs and achieved recoveries of 72-130% with relative standard deviations (<24%) and limits of detection (1.0-67 ng g-1) suitable for detecting both major and minor PCB congeners. Downscaling the method allowed replicate analyses of livers, as only 300 mg of sample was required per replicate. Extracts from 14 liver samples were analysed using gas chromatography-mass spectrometry. Total PCB concentrations ranged from 447 to 1810 ng g-1, with PCB-101, PCB-110, PCB-138 and PCB-153 responsible for 76% of all detected congeners. Concentrations exceeded those previously reported for the livers of healthy short-tailed shearwaters by one to two orders of magnitude. Additionally, elemental analysis detected elevated levels of cadmium (47 ± 18 μg g-1) and mercury (6 ± 3 μg g-1), highlighting the biomagnification of these toxic metals in marine food webs. The results presented here support the need for ongoing monitoring of short-tailed shearwaters to better understand the role contaminants may play in mass mortality events.
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