MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14755

ABSTRACT: Across relatively small spatial scales, differences in seascape structure may influence how species transverse adjacent habitats, with effects on trophic relationships and energy flow dynamics. To understand the effects of seascape structure, we used stable isotope analysis to examine variation in the resource use of two highly abundant estuarine species, mummichogs (Fundulus heteroclitus) and grass shrimp (Palaemon spp.), both of which are known to forage in intertidal areas. We compared the percent contribution of basal resources, trophic position, and trophic niches of mummichogs and grass shrimp from two tidal creeks with differing seascape structure located ~10 km apart on Sapelo Island, Georgia. Belle Marsh creekbank edge elevation was on average 0.5 m lower and channel density was 5x greater than Dean Creek, potentially influencing marsh platform access. Although we found no difference in the contribution of marsh-derived energy to grass shrimp among sites, the contribution of marsh-derived energy to mummichogs was on average 1.9x higher at Belle Marsh. In addition, both species had higher trophic positions and larger trophic niches at Dean Creek, suggesting a less efficient route of energy transfer to consumer production. There was also little overlap in trophic niche among sites for either species. Our results suggest that species traits, site characteristics, and their interaction may influence the resource use of intertidal estuarine consumers. By examining how marsh resource use by estuarine consumers varies across multiple marshes with differing morphologies, we can better predict and quantify how seascape structure may affect secondary productivity of estuarine systems.