The green porcelain crab (Petrolisthes armatus) is a small tropical crustacean that has advanced up the eastern seaboard of the United States since 1990. Commonly found in the oyster reefs of the South Atlantic Bight, the porcelain crabs appear to be having mixed effects on native species. Recent research at the Georgia Institute of Technology has demonstrated that the porcelain crabs do not directly prey upon oysters, in fact, they seem to promote the survival of juvenile oysters. This is due to the fact that the native predators of juvenile oysters appear to prefer porcelain crabs, thus possibly simultaneously increasing the predator population and reducing the predation of juvenile oysters. However, this positive effect for the oyster population is at least somewhat mitigated by the fact that the researchers also found that the presence of porcelain crabs suppressed the growth of juvenile oysters, supposedly through competition for food as both species are filter feeders. In light of these conflicting effects, further monitoring and research of the porcelain crab is necessary to ascertain the long term effects its arrival will have for the ecosystems of the southeastern United States.
Due to their roles as nurseries for many species, oyster reefs serve as the foundation of the marine ecosystems of the southeastern United States and so any threat to this valuable habitat warrants serious investigation. One source of danger is that the green porcelain crab appears to be a preferred prey option to many common native predators of oysters. This could lead to an ecological disaster if the porcelain crab suddenly died out and the increased predator population reverted to its traditional prey. Also, if the green porcelain crab is truly slowly the development of juvenile oysters, this will have important ramifications for the commercial fishermen who harvest oysters. As noted in the article, too little is presently known about the long term effects of the green porcelain crab to determine if it poses a significant threat. However it should be noted that despite the heavy predation, green porcelain crab populations in its new range exist in densities far in excess of what has been observed in its native habitat. This suggests that ecological management of the green porcelain crab will be costly and difficult should it become necessary to protect the valuable oyster reef ecosystems of the southeast.