Concentrations of selenium and mercury in eared grebes (Podiceps nigricollis) from Utah's great Salt Lake, USA

Abstract

We examined selenium and mercury concentrations in eared grebes (Podiceps nigricollis) that spent the fall of 2006 on the Great Salt Lake (UT, U.S.A.), where their diet consisted mainly of brine shrimp (Artemia franciscana). Selenium concentrations in livers varied based on when the grebes were collected (lower in September [mean +/- standard error, 9.4 +/- 0.7 microg/g dry wt] than in November [14.5 +/- 1.4 microg/g]), on where the birds were collected on the Great Salt Lake (Antelope Island, 8.6 +/- 0.5 +/- microg/g; Stansbury Island, 15.2 +/- 1.4 microg/g), and on the grebe's age (juveniles, 8.5 +/- 1.5 mcirog/g; adults, 15.8 +/- 1.3 microg/g), but not by sex. Selenium concentrations in blood differed only by collection site (Antelope Island, 16.8 +/- 2.3 microg/g; Stansbury Island, 25.4 +/- 3.0 microg/g). Mercury concentration in the blood of grebes varied by when the grebes were collected (September, 5.6 +/- 0.5 microg/g; November, 8.4 +/- 1.2 microg/g), where the birds were collected (Antelope Island, 4.3 +/- 0.5 microg/g; Stansbury Island, 10.1 +/- 2.6 microg/g), and the grebe's age (juveniles, 5.5 +/- 0.8 microg/g; adults, 8.4 +/- 1.0 microg/g), but not by sex. Selenium concentrations in blood were correlated with selenium concentrations in the liver and with mercury concentrations in both blood and liver. Body mass of grebes increased dramatically from September (381 +/- 14 g wet wt) to November (591 +/- 11 g). Body, liver, and spleen mass either were not correlated with selenium or mercury concentrations or the relationship was positive. These results suggest that high mercury and selenium levels were not preventing grebes from increasing or maintaining mass.