Mercury, cadmium, copper, arsenic, and selenium measurements in the feathers of adult eastern brown pelicans (Pelecanus occidentalis carolinensis) and chicks in multiple breeding grounds in the northern Gulf of Mexico

The amounts of trace metals and metalloids that have been introduced into aquatic ecosystems due to anthropogenic activities have increased in recent decades. Some of these elements like mercury are easily transferred from one trophic level to another and can accumulate to toxic quantities in organisms at the top of aquatic food webs. For this reason, seabirds like the Eastern brown pelican (Pelecanus occidentalis carolinensis) are susceptible to heavy metal and metalloid toxicity and may warrant periodic monitoring. Mercury, cadmium, copper, arsenic and selenium were measured in the feathers of adult brown pelicans and chicks in several breeding colonies (Shamrock Island, Chester Island, Marker 52 Island, North Deer Island, Raccoon Island, Felicity Island, Gaillard Island, Audubon Island, and Ten Palms Island) in the Northern Gulf of Mexico. Overall, most chicks and adults examined had mercury levels in feathers that were below the concentration range in which birds show symptoms of mercury toxicity. However, chicks in the Audubon Island and Ten Palms Island colonies displayed mercury levels that were 3 times higher than values observed in 5 other colonies. In addition, several adults and chicks displayed selenium concentrations that are above what is considered safe for birds. Cadmium quantities in feathers were below levels that trigger toxicity in birds. Similarly, arsenic measurements were at quantities below the average of what has been reported for birds living in contaminated sites. Finally, we identify pelican breeding colonies that may warrant monitoring due to elevated levels of contaminants.