COS 272-5 - CANCELLED - Burrowing crabs have greater impacts on edaphic characteristics in created than natural tidal wetlands along the northern Gulf of Mexico.

Background/Question/Methods

Tidal wetland creation often fails to recover all ecosystem functions. Failure to recover ecosystem functions may occur when creation strategies focus on establishing populations of foundation plant species and neglect other important ecosystem engineers. For instance, burrowing crab communities, through their tunneling and foraging behaviors, can promote the retention and accumulation of organic matter in wetland soils. To understand if burrowing crabs facilitate ecosystem functions in created wetlands and how these effects compare to crab effects in natural wetlands, we conducted two complementary studies in a tidal wetland complex consisting of two created wetlands and one natural wetland along the West Fowl River in Alabama, U.S.A. In the first study, we used a comparative survey to understand how plots with naturally occurring High and Low crab burrow densities differ in biological structure and ecosystem functions, including edaphic characteristics like soil organic matter content. The second study was a caging study, where we manipulated the relative density of crab burrows (i.e., High vs. Low) to mechanistically understand the impacts of crab burrow density on tidal wetland biological structure and ecosystem functions.

Results/Conclusions

In both studies and sites, areas with High crab burrow densities had higher densities of Juncus roemerianus stems and greater aboveground biomass than plots with Low crab burrow densities. Additionally, in created wetlands, High crab burrow densities were associated with lower soil pH and higher bulk densities of surface soils (top 2.5 cm). Burrowing crabs had no effects on soil pH or bulk density in the natural wetland. Crab burrowing likely increased surface bulk density in the created wetlands by excavating deeper soils that, in our specific sites, are characterized by inorganic clays. Our initial findings show that burrowing crab communities have greater effects on edaphic characteristics in created wetlands than reference wetlands; however, the directionality of these effects depend on the specific characteristic being examined. This suggests that burrowing crab communities, by altering edaphic characteristics, may influence the recovery of ecosystem functions in created tidal wetlands.