Linking seabird behaviour and environmental toxicology: An assessment of pollutant exposure, biological matrices for analysis, and foraging ecology

Abstract

Marine ecosystems support human well-being by providing food and helping regulate the cli-mate, but face threats from overexploitation and degradation. Among various threats, pollution has emerged as a major concern. The Mediterranean Sea, in particular, is heavily impacted by pollution, emphasizing the need for comprehensive pollution monitoring. Especially of pollutants, that are subject to bioaccumulation due to their high stability in the environment. Despite this, current ef-forts to monitor persistent organic pollutants (POPs) lack sufficient geographical coverage, and no standardized evaluation protocols exist for seabirds and marine mammals. Environmental toxicology is a field dedicated to investigating the sources, pathways, and impacts of pollutants as they move through air, water, soil, and living organisms. For lower trophic organisms, pollutant assessment is more straightforward, but grows more complex in highly mobile and long-lived species like seabirds and marine mammals. Despite this, it is crucial to assess pollutants in higher trophic organisms, not only because they play a key role in biodiversity and integrate magnification processes along the food chain, but also because they occupy a similar trophic position to humans as consumers of fish. Scopoli’s shearwaters (Calonectris diomedea) are long-lived Mediterranean seabirds, adapting their behaviour to seasonal needs but are impacted by anthropogenic stressors and chemical pollution. This PhD thesis focuses on three critical factors that influence the quality and interpretability of pollutant biomonitoring studies in seabirds: (1) development of analytical methods, (2) the choice of tissue matrix, and (3) the foraging ecology of the study species. The goal was to establish baseline data on pollutant levels, diet, and foraging behaviour in Scopoli’s shearwaters and to develop effec-tive methods for advancing environmental toxicology research in seabirds, focussing on Scopoli’s shearwater as a potential indicator species. A range of methods were employed, including liquid and gas chromatography coupled with mass spectrometry for pollutant analysis, isotope ratio mass spec-trometry for stable isotope analysis, DNA metabarcoding for molecular diet analysis, and camera loggers to track foraging behaviour. Bioaccumulative organic legacy and in-use pollutants were de-tected in all analysed Scopoli’s shearwater tissues. Blood values likely reflect local and temporal differences in pollutant burdens. In the study year 2020, isotopic niche was relatively narrow in Sco-poli’s shearwaters during chick-rearing and pollutant concentrations were lower than during incuba-tion in males. Sample choice depends on the research goal and pollutant type, but blood samples reflect current contamination, support population comparisons and several explanatory variables can be included in routine analyses. Pollutant exposure is likely influenced by foraging strategy and sex. Artisanal fisheries play a role for foraging Scopoli’s shearwaters, but distinguishing prey sources (natural vs. discards) is challenging due to size similarities and variable species distribution. This research underscores the importance of interdisciplinary collaboration between analytical chemists and behavioural ecologists to push the boundaries of environmental toxicology.