Mercury in Brown Booby (Sula leucogaster) Feathers from the São Pedro and São Paulo Archipelago as a Tool for Environmental Biomonitoring

Seabirds are important bioindicators of environmental quality as their feathers contain records of metal concentration. Among the metals, mercury (Hg) is toxic, causing damage to the organism even in small concentrations. The objective of this study is to determine and evaluate the total Hg levels in brown booby feathers in the São Pedro and São Paulo archipelago (SPSPA) (0º55´02´´N; 29º20´42´´W), comparing to literature levels of metal in feathers of different Sula species in several locations from Brazil and elsewhere in the world. To determine Hg levels, the study uses the methodology of partial digestion of collected feathers, followed by the analysis by inductively coupled plasma optical emission spectrometry (ICPOES). The average value of the Hg concentration was 2.6 ± 3.5 mg kg-11, which is below the threshold for the occurrence of adverse effects due to mercury toxicity in seabirds. For the statistical analysis of comparison between sexes of the SPSPA population, and for comparison between species of the genus Sula in different places around the world, this study uses Analysis of Variance (ANOVA), followed by the Tukey test. There was no significant difference between sexes in Hg concentration. However, there was a significant difference between the compared sites, demonstrating that the SPSPA has a low Hg concentration, differing only from Daphne Island, Galapagos a region with high Hg atmospheric deposition due to its climatic conditions. Between the species of the genus Sula, the study detected a significant difference in the accumulation of Hg. The species S. leucogaster differed from the species S. granti, which is also associated with Galapagos. The other species displayed accumulation of Hg resembling that of S. leucogaster, confirming a similarity between their nourishment habits and their trophic niches. The results support future Hg monitoring programs in this important Marine Conservation Unit and Environmental Protection Area.