Fifth Annual Grant Winners 2004-2005

Edward Keith, Ph.D., Oceanographic Center

Dean Richard Dodge, Oceanographic Center

Title: Mercury Analysis in the Alvarado Lagoon System, Veracruz State, Mexico

Abstract:

The Alvarado Lagoon System (ALS) is located about 50 km southeast of Veracruz, Mexico, along the Gulf of Mexico. The ALS is a vast (314,000 hectare) wetland created by the merged deltas of three rivers, and is home to a burgeoning human population, many of whom live at a subsistence level consuming fish and edible invertebrates harvested from the waters of the ALS.

Based on verbal reports of elevated mercury levels in the ALS, a preliminary study was conducted last year to determine total mercury levels in ALS water, fish, and invertebrates (i.e. shrimp, crab, and squid). The results of this survey indicate that the waters of the ALS contain low levels of mercury (0.92 – 37.0 ng/L). The fish and invertebrate samples were also generally low in mercury (0.008-0.144 ppm edible wet weight) however, one species of fish, the mojarra (Eugerres plumieri)

contained 0.35 ppm (edible wet weight) of mercury, enough to cause concern if that species of fish were to be consumed on a regular basis.

In order to ascertain the level of threat that this mercury contamination represents, it is proposed to conduct a more thorough sampling of waters and sediments in the ALS, and to collect samples of human hair from the residents of the ALS. This will permit elucidation of the pathways by which mercury is entering and cycling within the ALS ecosystem, and to determine mercury levels in the human population to evaluate if a threat to human health exists.

Work will be conducted in collaboration with Mexican scientists and public officials, in order to facilitate data collection, and to ensure that the results of this study are disseminated to the appropriate authorities, both in the United States and in Mexico.