Effect of multiple parasites in the Gulf of Mexico
As oyster populations decline globally, it’s important to understand how parasites may affect these ecologically important and economically valuable species across the dominant environmental gradients of estuaries. While it is common to study the effects of one parasite on one host, it’s rare to find a host infected with only a single parasite. In this study, Hanley et al. looked at patterns of parasite species diversity across the two main environmental gradients of an estuary in the northern Gulf of Mexico, a region that has experienced dramatic decreases in oyster populations, with devastating impacts on the oyster fishery. Hanley et al. sampled oyster reefs at distances close to and far from the river input (freshwater) in order to sample parasites across a salinity gradient. In addition, Hanley et al. sampled oyster reefs that are always submerged by water and reefs that are periodically submerged by water and exposed to the air (intertidal reefs). They found that almost 70% of oysters were infected with multiple parasites. While the diversity of parasites did not vary across each of the environmental gradients, parasite identity did. In addition, a variety of different environmental (salinity, tidal height) and biotic (host density and size) factors best predicted the prevalence of each parasite species. Consequently, predicting disease outbreaks and long-term health of oyster populations requires consideration of multiple environmental contexts and multiple parasites.
Photos of oyster shells damaged by two different parasites: mud blister worms (left) and boring sponge (right).
Hanley, T.C., J.W. White, C.D. Stallings, D.L. Kimbro. 2019. Environmental gradients shape the combined effects of multiple parasites on oyster hosts in the northern Gulf of Mexico. Marine Ecology Progress Series 612, 111-125.