Article Dans Une Revue Journal of Hazardous Materials Année : 2025

The role of seabird foraging strategies on the uptake of mercury: A case study using gulls and shearwaters from the Portuguese coast

Résumé

Mercury (Hg) is a non-essential element that bioaccumulates and biomagnifies in food webs through site-specific biogeochemical processes. Seabirds are valuable bioindicators of Hg contamination, yet certain regions, like the Portuguese coast, remain under represented. This study measured Hg concentrations in the blood of yellow legged gulls (Larus michahellis), Audouin’s gulls (Ichthyaetus audouinii), and Cory’s shearwaters (Calonectris borealis) breeding along the Portuguese coastline. The influence of foraging ecology on Hg contamination was investigated using stable isotopes (δ13C, δ15N, δ34S) along with GPS-loggers. Thus, 52 % of the adults were at low risk (0.95–4.8 μg g-1 dry weight, dw), while 37 % were at moderate risk of Hg toxicity (>4.8 μg g-1 dw). The highest trophic positions (indicated by δ15N values) were associated with higher Hg concentrations, particularly in gulls from Deserta Island. Yellow-legged gulls foraging in terrestrial habitats (inferred from lower δ13C and δ34S values and GPS data) generally exhibited lower Hg concentrations, although patterns varied between regions. Gulls from Deserta Island had elevated Hg concentrations, likely because they feed on discarded demersal fish. In contrast, those from Porto showed some of the lowest concentrations, likely because they fed on terrestrial food. However, other factors not evaluated here, like age, sex, or even phylogeny could have also influenced Hg uptake and bioaccumulation and should not be disregarded in future research. This study highlights the critical role of foraging strategies in Hg contamination and stresses the importance of estimate food web-specific baseline isotopic composition to better understand how these differences may impact Hg trophic transfer.

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Dates et versions

hal-05007682 , version 1 (26-03-2025)

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Ivo dos Santos, Jaime Ramos, Filipe Ceia, Joana Pais de Faria, Jorge Pereira, et al.. The role of seabird foraging strategies on the uptake of mercury: A case study using gulls and shearwaters from the Portuguese coast. Journal of Hazardous Materials, 2025, 489, pp.137673. ⟨10.1016/j.jhazmat.2025.137673⟩. ⟨hal-05007682⟩
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