Date of Award

Summer 2022

Document Type

Open Access Thesis


Marine Science

First Advisor

James Pinckney


The eastern mud snail, Ilyanassa obsoleta, is found at densities of 100’s of individuals m-2 on soft sediments in the intertidal zones of estuaries. These obligate deposit feeders consume microalgae, detritus, larvae, meiofauna, and macrofauna in the surface layers of sediments with possible trophic impacts on benthic microalgal (BMA) biomass. The goals of this study were to quantify mud snail grazing on BMA biomass, observe the variation in monthly and seasonal grazing rates, and evaluate the relationship between atmospheric temperatures and grazing rates. The sites for this experiment were two mudflats in Oyster Landing, North Inlet estuary, South Carolina. Two different methods were used; in-situ enclosures placed at each site (June 2021-September 2021) and in-vitro plastic containers filled with mud and snails from each site (November 2021- May 2022). Biweekly, sediment samples before and after I. obsoleta grazing opportunity were collected and analyzed for BMA biomass using high-performance liquid chromatography or fluorometry. There was not a statistically detectable difference between grazed and ungrazed corrected average daily differences in mean BMA biomass/chlorophyll a (p = 0.061). Looking at each method separately, there was not a significant difference between the two variables in the enclosures (p = 0.904) or the containers (p = 0.059). Corrected mean monthly grazing rates did not significantly differ (p = 0.895). Corrected mean seasonal grazing rates did not have any statistically detectable differences (p = 0.961). There was not a clear relationship between the median experimental temperatures and the corrected average daily difference in mean chlorophyll a of the grazed plots (p = 0.607) or the corrected average daily I. obsoleta grazing rates (p = 0.693). I. obsoleta grazing effects could change the BMA biomass, leading to changes in other trophic levels within the temperate estuary ecosystem. The direction and magnitude of these grazing effects are still unclear.


© 2022, Brittany DeArmitt