Accumulation and maternal transfer of perfluorooctane sulphonic acid in yellow-legged (Larus michahellis) and Audouin's gull (Larus audouinii) from the Ebro Delta Natural Park

This study aimed to determine the accumulation and maternal transfer of perfluorooctane sulphonic acid (PFOS) in yellow-legged gulls (YLG, Larus michahellis) and the protected species Audouin's gull (AG, Larus audouinii), which cohabit in the Ebro Delta Natural Park (Catalonia, Spain). The Estimated Daily Intake (EDI) through diet (fish and crayfish), depuration rates and transfer capacity from blood to first eggs was studied for a set of 44 pairs. For AG, mean (±SD) EDI was of 128±36 ng/d in males and 119±32 ng/d in females, and for YLG, 170±48 ng/d in males and 159±42 ng/d in females. PFOS levels in blood were higher in males than females (60.6±21 and 61.1±27 ng/g ww in AG and YLG males versus 25.2±12 and 27.3±14 ng/g ww in AG and YLG females), with little differences among species. The lower levels in females were attributed to the annual release of PFOS to eggs during the laying period, which was estimated of 5544±1571 ng/egg for AG females and 6716±2689 ng/egg for YLG. The overall mass balance of PFOS calculated for both species clearly demonstrates that uptake is higher than elimination rates, considering depuration rates and transfer of PFOS to eggs, and this explains that PFOS is accumulated in gulls in a yearly basis.