Local and interannual variations in mercury and cadmium in eggs of eight seabird species of the Sinaloa coast, México

Mercury (Hg) and cadmium (Cd) concentrations in eggs of 8 seabird species inhabiting 5 coastal ecosystems in Sinaloa, México were determined during 2 breeding seasons (2012 and 2013): blue‐footed booby ( Sula nebouxii ), brown booby ( Sula leucogaster ), double‐crested cormorant ( Phalacrocorax auritus) , magnificent frigatebird ( Fregata magnificens ), brown pelican ( Pelecanus occidentalis ), royal tern ( Thalasseus maximus ), laughing gull ( Leucophaeus atricilla ), and Heermann's gull ( Larus heermanni ). The interspecific differences found in the concentrations of both metals were attributed to the diet and foraging ecology of the species. The highest Hg concentrations were detected in piscivorous species (brown pelican, 0.42 µg/g; brown booby, 0.31 µg/g; blue‐footed booby, 0.26 µg/g; and double‐crested cormorant, 0.23 µg/g); whereas species with more varied diets presented the highest Cd concentrations (Heermann's gull, 0.31 µg/g; laughing gull, 0.27 µg/g; and magnificent frigatebird, 0.27 µg/g). Cadmium concentrations were significantly greater in 2013 than 2012 for most species, and brown pelican and laughing gull also had higher Hg concentrations in 2013 in Santa María Bay, suggesting a relationship as a result of the changes either in oceanographic conditions or in continental runoff. Mercury concentrations in brown pelican and Cd concentrations in Heermann's gull and laughing gull were above threshold levels for adverse effects on reproduction and survival. Environ Toxicol Chem 2016;35:2330–2338. © 2016 SETAC