Effects of mercury, selenium, and organochlorine contaminants on reproduction of Forster's terns and black skimmers nesting in a contaminated Texas bay

Mean mercury (0.40 mu g/g), and geometric mean DDE (1.6 mu g/g) and polychlorinated biphenyl (PCB) (2.3 mu g/g) concentrations in Forster's tern (Sterna forsteri ) eggs from Lavaca Bay were higher than those in tern eggs from a reference area in San Antonio Bay, but residues were not correlated with hatching success. Nest success was similar between bays. Selenium levels in Lavaca Bay tern eggs (0.71 mu g/g) were also comparable to those in eggs from the reference area (0.68 mu g/g). Clutch size (3.1 to 3.4) of Lavaca Bay black skimmers (Rynchops niger ) was no different than that (3.4) at a reference colony near Laguna Vista. Nest success was similar among three Lavaca Bay colonies, but success was lower at one Lavaca Bay colony (40%) than at Laguna Vista (65%). Mean mercury (0.46 mu g/g) and selenium (0.75 mu g/g) concentrations in skimmer eggs from Lavaca Bay wee higher than those (0.19, 0.33 mu g/g) from Laguna Vista.