Mercury concentrations of two forage fish from Waties Island, SC

Event Location: 
BCCMWS Room 100
Event Date: 
Thursday, September 11, 2014 - 3:00pm
Event Type: 
SCMSS Seminar Series

Presenter: Dano Ferons

Inorganic mercury (Hg2+) enters South Carolina waterways through wet and dry deposition. Before bioaccumulation in organisms can begin, the inorganic mercury has to be converted into methylmercury (CH3Hg+). This process is enabled by sulfate and iron reducing bacteria in the sediments of low oxygen environments, such as salt marshes. After mercury is converted into methylmercury, it is resuspended in the water column. Diatoms and other phytoplankton will accumulate the methylmercury through passive diffusion across their cell membrane. When phytoplankton are consumed by zooplankton, the methylmercury within the phytoplankton is assimilated into the tissues of the zooplankton. Forage fish feeding on the zooplankton will accumulate the methylmercury from the zooplankton into their tissues. As trophic levels increase, the concentration of mercury assimilated in the tissues of organisms increase.

Mummichogs (Fundulus heteroclitus) and Atlantic silversides (Menidia menidia) are abundant forage fish species that live year round in South Carolina salt marshes. Both species are tertiary consumers that have different food web interactions. Mummichogs are opportunistic omnivores that feed during high tide within the stalks of Spartina alterniflora. Prey is captured from the water column, within sediments and off of S. alterniflora. Atlantic silversides are planktivores and prey on zooplankton suspended above oyster reefs and mud flats during high tide. Preliminary mercury data shows that silversides (32.98 +/- 2.97 ng/g dry weight total Hg) have higher mercury concentrations than mummichogs (15.90 +/- 9.02 ng/g dry weight total Hg). Differences in mercury concentrations may impact the bioaccumulation of mercury in higher trophic organisms.