Mercury and lead hepatic content in shag (Phalacrocorax aristotelis) and gannet (Morus bassanus) from the Galician coast (Spain)

At the present work, heavy metal (Hg and Pb) concentrations in hepatic tissue from two seabird species (shag, Phalacrocorax aristotelis, and gannet, Morus bassanus) have been analyzed, by using collected animals which died or were dying along the Galician coast (NW Spain). The considered animals were divided in two groups, considering if they had been affected or not by the oil spill caused by the "Prestige" in November 2002, and in order to determine if such spill had modified the heavy metal content of such seabird species. After sample wet digestion, heavy metal content was determined using anodic stripping voltammetry (Pb) and direct mercury analyzer (DMA) (Hg). When considering inter-specific differences for total Hg, hepatic concentrations from shag samples (mean 4.2-7.6 ppm) were higher than those from gannet (mean 1.6-1.8 ppm), with a maximum value reaching up to 20 ppm (wet weight), corresponding to an animal affected by the oil spill. With regards to Pb content, results were different, with slightly higher levels from gannet samples than those from shag, but never exceeding 0.01 ppm (wet weight). When considering both established groups (affected or not by the "Prestige" accident), it could be established that the oil spill did not affect on a statistically significant manner the levels of both metallic contaminants on the hepatic tissue of the considered animals.