Effects of severe inundation on a coastal marsh grass and its associated insect assemblage

Coastal marshes face a constant risk of catastrophic flooding from severe weather events such as hurricanes, and many predict that the intensity and frequency of such events will rise due to global climate change and rising sea level. The physiological impact of inundation stress has been characterized for many salt marsh plants; it is not known how flooding affects the invertebrate assemblages that these plants support. Flood-induced mortality or emigration can directly reduce insect populations. There may also be prolonged indirect effects on insects, mediated by host plant physiological responses to flooding. Spartina patens, the dominant plant in our experimental plots, is fed upon by several guilds of herbivores, which in turn support an assemblage of predators, parasites and parasitoids. In this study we simulated catastrophic flooding in 50m2 plots on a brackish coastal marsh in Louisiana. Insects were collected from study plots and their taxonomic identity and feeding guild were recorded. Spartina patens was also collected and nutritional value and palatability of plant tissues were measured and compared between plots. Pathway analysis was used to determine the effects of flooding on plant quality and the magnitude of direct and indirect effects of flooding on the species richness and abundance of insects. This project emphasizes the value of a multitrophic perspective when examining the impact of environmental stressors on an ecosystem.