Grantee Research Project Results
An Invasive Crab in the South Atlantic Bight: Friend or Foe?EPA Grant Number: U915531
Title: An Invasive Crab in the South Atlantic Bight: Friend or Foe?
Investigators: Hollebone, Amanda L.
Institution: Georgia Institute of Technology
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1999 through January 1, 2002
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1999)
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems
Biological invasions can be a threat to the integrity of natural communities and a major force in determining the structure of ecosystems. The green porcelain crab, Petrolisthes armatus, recently invaded oyster reefs of the South Atlantic Bight at densities of up to several thousand/m2, but the spatial pattern of invasion and its ecological consequence are undetermined. The objectives of this research project are to: (1) monitor seasonal patterns of crab density across estuarine gradients at the Sapelo National Estuarine Research Reserve and Skidaway Island, GA; (2) use outdoor mesocosm tanks to experimentally manipulate crab densities to determine their impacts on oyster reef communities.Approach:
The mesocosm treatments assess crab effects at densities equivalent to 0, 700, 1,500, or 2,250 crabs/m2 with measured responses including: survivorship; growth and settlement of oysters and mussels; settlement of juvenile crabs, gastropods, annelids, and other crustaceans; percent cover of macrophytes; chla/substrate area; and organic content of surrounding sediments. Monitoring data show that crab densities in both estuaries commonly reach 1,000-10,000 crabs/m2, that densities decline in the upper regions of the estuaries, and that densities increase the lower the oyster substrate lies in the intertidal. The mesocosm experiment suggests that the crabs affect the abundance of both macrophytes (+ effect) and microalgae (changing from – to + over time) growing on oyster substrate, but do not affect the growth and survivorship of mussels and oysters or sediment organic content. Field experiments to verify these results are underway. Preliminary data suggest that larval crabs preferentially settle where there are adult conspecifics.Supplemental Keywords:
fellowship, South Atlantic Bight, green porcelain crab, Petrolisthes armatus, Skidaway Island, Georgia, GA, crab densities, oyster reef communities, invasive species.