Year-round element quantification of a wide-ranging seabird and their relationships with oxidative stress, trophic ecology, and foraging patterns

Acknowledgements : We would like to thank the Instituto da Conservação da Natureza e Florestas (ICNF) for permits and logistical support (lodging) to conduct this work. All applicable international, national, and/or institutional guidelines for the care and use of animals were followed and all necessary approvals have been obtained from the ICNF. Special thanks to the wardens, Paulo Crisostomo ´ and Eduardo Mourato (Reserva Natural das Berlengas). We would like to thank Jos´e Seco for valuable inputs during earlier drafts of the manuscript. LMFA and JMP acknowledge their grants (SFRH/BD/122082/2016, SFRH/BD/123499/2016, respectively) attributed by the Foundation for Science and Technology (FCT; Portugal). This study benefited from the strategic program of MARE, financed by FCT (MARE - UID/MAR/04292/2020) and the transitory norm contracts DL57/2016 to FRC (DL57/2016/CP1370/ CT90), ACN (DL57/2016/CP1370/CT89), VHP (SFRH/BPD/85024/2012) and SCN (SFRH/BPD/94500/2013). Financial support provided by FCT and MARE through a PhD grant attributed to MIL (UI/BD/150956/2021) and the project ECOLIND – Seabirds and fish as ecological indicators of contaminants and health in the North Atlantic relevant to ocean resources assessment (MFM/2017/0003)

Multidisciplinary approaches are essential to diligently assess environmental health status of ecosystems. In this study, year-round chemical elements’ exposure and impacts were assessed on the wide-ranging Cory’s shearwater Calonectris borealis breeding in Berlenga Island, offshore Portugal, North Atlantic Ocean. The aim was to identify potential contamination and oxidative stress sources associated with trophic ecology, habitat and spatial use, and foraging patterns. A set of 20 chemical elements were quantified, along with oxidative stress biomarkers, stable isotope analyses, and GPS tracking data. Birds presented higher accumulation to some nonessential elements along the year (i.e. arsenic, As; cadmium, Cd; mercury, Hg; lead, Pb; and strontium, Sr), in which concentrations were similar or surpassed other procellariform seabird populations all over the world. No significant differences were found for any of the elements between different periods within the breeding season, with exception of Hg. However, a Principal Component Analysis taking into consideration a group of elements showed differences between pre-laying and chick-rearing periods, with overall higher concentrations in the former. Individuals spending more time engaging in an intensive search for food, and in more coastal environments, presented overall higher element concentrations, and particularly Hg. Contrary to expectations, no relationships were found between chemical elements and oxidative stress. On the other hand, spatial use and foraging patterns of Cory’s shearwaters influenced their oxidative stress responses. Our results highlight the need for multidisciplinary approaches to deepen understanding of the large-scale vulnerability of bioindicators such as seabirds and, by extension, the overall environmental health of ecosystems in which they rely.

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