MEPS prepress abstract  -  DOI:

Environmental gradients shape the combined effects of multiple parasites on oyster hosts in the northern Gulf of Mexico

Torrance C. Hanley*, J. Wilson White, Christopher D. Stallings, David L. Kimbro


ABSTRACT: Parasites can shape population, community, and ecosystem dynamics, especially if their hosts play a key role in the ecosystem. Multiple parasites frequently co-infect hosts that alter disease dynamics via a variety of mechanisms. Further, abiotic and biotic factors often differentially affect hosts and their associated parasites, with direct and/or indirect effects on disease prevalence and intensity. We conducted a field survey of eastern oyster populations in the northern Gulf of Mexico to examine spatial patterns in parasite species richness of this foundation species. We assessed whether environmental factors and/or host characteristics best predicted prevalence and intensity of the most common micro- (Perkinsus marinus; Dermo) and macro-parasites (boring sponge Cliona, mud blister worm Polydora) in the region. The number of parasite species infecting each host (i.e., species richness) was spatially homogeneous due to variation in the predominant factors underlying the prevalence and intensity of each species. These factors were host density, tidal elevation, and temperature for Dermo; tidal elevation and host size for boring sponge; and salinity for mud blister worm. Host condition depended on abiotic and biotic factors, including tidal elevation (intertidal > subtidal) and prevalence of both Dermo (positive relationship) and boring sponge (negative relationship). Abiotic influences on oysters and parasites – and multiple parasite effects – produced an unexpected positive correlation between host condition and Dermo prevalence. Thus, predicting the likelihood of disease outbreaks and assessing the long-term health of host populations requires consideration of the combined effects of multiple parasites, abiotic conditions, and biotic factors.