Date of Award

1-1-2015

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

Jane Guentzel

Second Advisor

Andrew Heyes

Third Advisor

Juliana M. Harding

Additional Advisors

Rachel Whitaker; Eric T. Koepfler

Abstract

Few studies have focused on mercury cycling within salt marsh estuaries. Mummichogs (Fundulus heteroclitus) and Atlantic silversides (Menidia menidia) are two species of forage fish that live year round in South Carolina salt marshes. During high tide, mummichogs feed from the water column, sediment, and off of smooth cordgrass while Atlantic silversides prey upon zooplankton. In this study, total and methyl mercury within mummichogs and Atlantic silversides from Dunn Sound, SC were quantified and compared over four seasons throughout 2014. Gut contents were also quantified and compared to determine if there was a dietary impact on the concentrations of total and methyl mercury in these fish. Atlantic silversides (20-44.8 ng/g THg; 17.1-40.6 ng/g MeHg) had significantly higher whole body total and methyl mercury concentrations than mummichogs (6.2-26.7 ng/g THg; 2.8-19.5 ng/g MeHg; p < 0.01, Two- way ANOVA, Tukey’s Test). There was no significant difference between the percentages of methylmercury in mummichogs and Atlantic silverside (Two-way ANOVA). This suggests that mummichogs and Atlantic silversides assimilate mercury at the same rate. The percent gut contents by weight (%W) and by number (%N) of Atlantic silversides were significantly different than mummichogs (p < 0.01, PREMANOVA). Mummichog gut contents were morediverse consisting of more than ten percent (%W and %N) Arthropods, detritus, and miscellaneous throughout 2014. Atlantic silverside gut contents were dominated by planktonic Arthropods. The differences in mercury concentrations in these two fish may impact the bioaccumulation of mercury in higher trophic level organisms.

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