Contemporary patterns of mercury contamination in the Portuguese Atlantic inferred from mercury concentrations in seabird tissues

摘要

Mercury concentrations in 1809 egg and plumage samples of adults and chicks of seabirds from colonies in the Portuguese Atlantic (30-40 N, 8-32 W) were determined. Species and tissues were selected to ensure varied levels of ecological (epipelagic vs mesopelagic), spatial (coastal vs pelagic) and temporal (short-to medium-term) integration of mercury contamination. There was an overall general agreement in the information provided by species and types of tissues employed. Results show a four-fold increase in mercury bioaccumulation from the epipelagic to the mesopelagic compartment. Fourteen out of 20 inter-location comparisons of mercury concentrations in tissues yield statistically significant differences. However, 11 differences did not rise above the intra-specific variability of the monitor species and were not considered to reflect genuine geographic variation in mercury contamination. The remaining three differences indicate shightly enhanced mercury contamination in the epipelagic food web adjacent to the southwest Portuguese coast, which deserves further elucidation. Seabird indications of mercury contamination in the study region were assembled with similar information in a brief meta-analysis for the North Atlantic and adjoining regions.