Date of Award

Spring 2008

Document Type

Legacy Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

John J. Hutchens, Jr.

Second Advisor

James O. Luken

Third Advisor

Keith R. Walters

Abstract

Strong pressures from abiotic conditions (e.g., temperature, salinity, inundation) and biotic interactions, such as competition, lead to unique distributions of the gastropods, Melampus bidentatus and Littoraria irrorata, in low-, mid-and high-marsh zones of salt marshes in the southeastern United States. Littoraria can displace Melampus from mid-marsh to high-marsh zones, yet Littoraria abundance and biomass are also relatively high in the high-marsh zone. Three Littoraria density manipulations were used in two habitats differing in dominant plant species, Juncus roemerianus and Salicornia virginica, to test whether competition or abiotic conditions affected the distribution of Melampus in the high-marsh zone. Growth rates and survivorship were recorded to assess competitive effects of Littoraria on Melampus. Soil constituents (e.g., phosphorous, pH), soil temperature and soil salinity within patches of Juncus and Salicornia were used to examine if abiotic conditions influenced differences in distribution of Melampus in the high marsh. Melampus growth was not significantly different among the three density treatments in either J roemerianus or S. virginica habitats. Melampus survivorship was significantly different between habitats (higher in Juncus than in Salicornia), but not among varying density treatments. Certain soil constituents (pH, phosphorous and sodium) were significantly different between Juncus and Salicornia. Average temperatures were higher in Salicornia than in Juncus. No evidence for competition was found in either Juncus or Salicornia. Therefore, habitat suitability, in particular abiotic conditions such as salinity and temperature, were most likely influencing gastropod assemblages in the high marsh of Waties Island.

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