Dataset and code: Experimental evidence for intergenerational effects of a contaminated and low-quality diet in a long-lived seabird

Abstract of the study: Marine ecosystems are experiencing unprecedented selective pressures from multiple anthropogenic stressors, including chemical pollution and changes in prey quality. As top predators, seabirds are particularly exposed to these pressures. While the impacts of contaminants and low food quality on adult seabirds are well documented, far less is known about potential intergenerational consequences. Yet, filling this gap is crucial, as early-life development can have lasting consequences on individual fitness and population dynamics. Using a unique experimental setting, we fed breeding Common gulls (Larus canus) with either fish originating from polluted or clean habitats during the egg-laying period. Fish caught from the polluted habitat were confirmed to contain higher concentrations of a cocktail of non-essential trace elements and a lower energy content compared to fish from the clean habitat. Chicks from parents exposed to this environmentally relevant compound dietary treatment hatched with smaller head-bill lengths and tended to exhibit lower hatchling mass when parents were fed fish from the polluted habitat. Moreover, these chicks exhibited lower baseline corticosterone and an altered relationship between growth and corticosterone compared to chicks from parents fed with fish from the clean habitat. Although the relative contribution of contaminant exposure and prey quality cannot be disentangled in the present design, our study provides rare experimental evidence that an environmentally relevant compound stressor can generate negative intergenerational effects in seabirds. Our findings highlight an overlooked pathway through which human-driven environmental changes may alter early-life development and, consequently, population dynamics in wild marine vertebrates.