Spatial and interspecific differences of trace element concentrations in the feathers of pelagic and coastal seabirds from the Northeast Atlantic Ocean and the Western Mediterranean Sea.

Coastal ecosystems face increasing contamination threats due to urbanisation and consequent human pressure worldwide. This study assessed exposure to 15 trace elements (Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sr, Ti, V, Zn) across the Northeast Atlantic and the western Mediterranean in pelagic shearwaters (Calonectris borealis and C. diomedea) and coastal gulls (Ichthyaetus audouinii and Larus michahellis). Shearwaters from the Mediterranean showed higher feather concentrations of Al, Cd, Co, Cr, Fe, Mn, Se, and Ti compared to Atlantic ones, reflecting historical contaminants in this basin. Coastal gulls exhibited varied concentrations influenced by diet and colony location. Audouin's gulls in the Ebro Delta had elevated Al, Fe, Mn, and Ti associated with industrial and agricultural activities. Yellow-legged gulls in Mediterranean colonies had higher Al, Co, Cr, Fe, Mn, and Zn levels, but Ria Formosa individuals had the highest Hg and Cd levels, linked to the ingestion of demersal prey. This study highlights the importance of using seabirds as indicators to understand trace element contamination in marine areas with different circulation characteristics, ranging from inshore to offshore areas and from less to more urbanised coastal areas.