Assessment of Metals in Tissues of Marine-Associated Birds in South Florida

Seabirds – broadly defined as any bird species associated with the marine environment – are exposed to a wide range of environmental contaminants. Vectors of exposure to metal pollution include by external contact, inhalation, and most often ingestion of food and incidental seawater. Seabirds are often considered marine ecosystem bioindicators due to their high trophic position, relatively long lifespan, and wide geographic ranges. We examined the concentration of total mercury (THg), lead (Pb), and cadmium (Cd), in the kidney, liver, breast muscle, and feathers of seven species of juvenile and adult seabirds commonly found in South Florida: brown pelican Pelecanus occidentalis (n=16), northern gannet Morus bassanus (n=16), double-crested cormorant Phalacrocorax auritus (n=15), royal tern Thalasseus maximus (n=15), herring gull Larus argentatus (n=9), laughing gull Leucophaeus atricilla (n=15), and osprey Pandion halietus (n=15). Trace amounts of lead and cadmium were found in the subsample of birds tested, suggesting that the birds living in south Florida do not face a significant threat from those metals. Results of total mercury in 101 specimens ranged from 0 to 45.07 mg/kg (dry wt), 0.15 to 132.13 mg/kg (wet wt), 0.06 to 352.35 mg/kg (wet wt), and 0.06 to 23.43 mg/kg (wet wt) in feathers, liver, kidney, and breast muscle respectively. Individual birds found to have the highest levels of total mercury were collected from centers in Monroe County. Osprey showed the highest total mercury values overall. These findings suggest a potential link to the Everglades and runoff into the Florida Bay, thus possibly exposing birds who utilize the Florida Bay at a higher risk for mercury poisoning