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MEPS prepress abstract   -  DOI:

Stable isotopes in seabirds reflect changes in marine productivity patterns

Francisco Ramírez*, Diego Vicente-Sastre, Isabel Afán, José M. Igual, Daniel Oro, Manuela G. Forero

*Corresponding author:

ABSTRACT: Seabirds have been proposed as suitable candidates for tracking and monitoring changes in marine systems (bioindicators). However, their suitability will depend on our ability to link the large degree of environmental variability inherent to marine systems within a few, relevant, and accessible signals (biomarkers) informing on changes in their feeding behavior or reproductive performance. We combined satellite remote-sensing records with stable isotope data (δ15N and δ13C) and breeding parameters (fledging success) spanning several years (2001 to 2014) to investigate the ecological responses to environmental variability by two sympatric seabirds inhabiting the western Mediterranean: the Scopoli’s shearwater, Calonectris diomedea, and the Cory’s shearwater, C. borealis. Both species showed similar annual variations in their stable isotopic composition, likely as a response to the trophic consequences of changes in the magnitude and timing of the annual peak in marine productivity (as proxied by satellite imagery on chlorophyll-a concentrations). Contrastingly, no relevant responses were observed in their breeding performance, thus suggesting that life-history strategy has evolved to constancy in breeding success that detracts from its value as biomarker of changes in marine productivity patterns. Despite this limitation, combining remote sensing and stable isotopes in seabirds emerges as a reliable and powerful tool for the early detection of fine-scale, climate-driven changes in marine productivity patterns and its cascading effects across communities and trophic levels, especially under the current scenario of ocean warming.