Invasion
Invasion Description
1st Record: near Richmond/VA/James River, river km 72 (1971, Diaz 1974).
Geographic Extent
Conowingo Dam/MD/Susquehanna River (1980, Counts 1986; Nichols and Dommermuth 1981); Susquehanna Flats (Havre de Grace)/MD/Upper Chesapeake Bay (1980, Counts 1986; Nichols and Dommermuth 1981); Salisbury/MD/Wicomico River; Seaford/DE/Nanticoke River (1985, Counts 1986; Kennedy and Huekelem 1985; Counts 1991); Salisbury/MD/Wicomico River (1981, Counts 1986; Kennedy and Huekelem 1985); Potomac Electric Company plants, Alexandria/VA/Potomac River (Dresler and Cory 1980); Accokeek/MD/Piscataway Creek (Potomac River) (1978, Dresler and Cory 1980); Plummers Island/MD/Potomac River (nontidal, 2004, Pearce and Evans 2008, 3rd most abundant mollusk); near Richmond/VA/James River, river km 72 (1971, Diaz 1974); River Miles 45-80/VA/James River (1972, Diaz 1974); Near confluence/VA/Appomatox, Chickahominy Rivers (1972, Diaz 1974); Hog Island Point, Surry/VA/James River (Jordan and Sutton 1984).
Vectors
| Level | Vector |
|---|---|
| Alternate | Fisheries Accidental (not Oyster) |
| Alternate | Fisheries Intentional |
| Alternate | Pet Release |
| Alternate | Discarded Bait |
| Alternate | Canal |
Regional Impacts
| Economic Impact | Industry | |
| Corbicula fluminea caused fouling of nuclear and conventional power plants, by clogging water pumps and condensers, including Potomac River Steam Electric Station, Alexandria VA, and the 12th Street Generating Plant, Richmond VA. This resulted in reduced efficiency, decreased output, and outages due to time required for cleaning (Diaz 1974; Potter and Liden 1986). | ||
| Ecological Impact | Herbivory | |
| In 1980, the biomass of C. fluminea in the tidal fresh Potomac River was estimated to be sufficient to filter all of the phytoplankton from one stretch (Rosier Bluff to Hatton Point, MD; River Km 160-165) every 3-4 days (Cohen et al. 1984). Cerco and Noel (2010) estimated filtering rates for bivalves (Corbicula and Rangia) in the oligohaline waters of Chesapeake Bay and its tributaries. Corbicula comprised <1-60% of the filter-feeding biomass in the major tributaries and upper Bay, being most abundant in the Potomac. The two species together removed 14% to 40% of the carbon load, 11% to 23% of the nitrogen load, and 37% to 84% of the phosphorus load from the water column (Cerco and Noel 2010). | ||
| Ecological Impact | Competition | |
| In the nontidal James River, Corbicula fluminea was thought to have virtually eliminated the native unionid Pleurobema collina (James River Spiny mussel), which formerly ranged from Richmond to the headwaters and is now confined to a few headwater streams. Abundances of Fusconaia masoni (Atlantic Pigtoe), Alismidonta undulata (Triangle Floater) and Strophitus undulatus (Squawfoot) may have been seriously reduced, but Elliptio complanata appeared to have been unaffected (Clarke 1986). Later studies have stressed the effects of habitat disturbance (siltation, stream modification, pollution) in the decline of P. collina in the James River Basin (Howe and Neves 1991). The importance of C. fluminea in the decline of native mussels is unresolved. | ||
| Ecological Impact | Habitat Change | |
| Changes possibly caused by C. fluminea's high filtering rates in the Potomac include: increased light penetration resulting in regrowth of native submerged aquatic vegetation, decreased down-bay transport of phosphates, disappearance of blooms of the blue-green alga Microcystis, and changes in sediment composition due to deposition of pseudofeces (Phelps 1994). Regrowth of native and introduced submerged aquatic vegetation in turn has positively affected waterfowl and fish populations (Killgore et al. 1989; Perry and Deller 1996; Phelps 1994). Additional factors, such as reduction of nutrient inputs are likely involved in these ecosystem-level changes, and the relative importance of the C. fluminea invasion remains to be determined. | ||
| Ecological Impact | Trophic Cascade | |
| Corbicula fluminea's invasion, especially in the Potomac River, has resulted in major changes in local foodwebs in tidal fresh and oligohaine regions, and has apparently shifted much of the flow of nutrients and energy from the water column to the benthos, affecting both the primary producers (phytoplankton and submerged vascular plants), and higher level predators, such as fishes and waterfowl. Changes attributed to C. fluminea include bay transport of phosphates on particles, disappearance of blooms of the blue-green alga Microcystis, and changes in sediment composition due to deposition of pseudofeces (Phelps 1994). | ||
| Ecological Impact | Food/Prey | |
| A wide variety of fishes are known to eat C. fluminea, but many of these species are not native to the Chesapeake region. Among possible native predators are suckers (Catostomidae); and White Catfish and Bullheads (Amieurus spp.) Fishes of the same families are listed by McMahon (1983) as predators of C. fluminea. Corbicula fluminea is an important food source for the endangered Shortnose Sturgeon Acipenser brevirostris and rare Atlantic Sturgeon A. oxyrhynchus in the Delaware River (Horwitz 1986); and probably in the Chesapeake as well. Five species of Chesapeake Bay ducks, Aix sponsa (Wood Duck), Anas clypeata (Northern Shoveler), Anas acuta (Pintail), Anas platyrhychos (Mallard), and Anas rubripes (American Black Duck) were found to be feeding on C. fluminea during 1973-76 (Perry 1981). Several additional species of diving ducks, known to feed on molluscs, including the Ring-Neck Duck (Athya collariformis), Bufflehead (Bucephala albeola), and Canvasback (Athya vallisnerae), also increased in the freshwater tidal Potomac during the height of the Corbicula invasion (Phelps 1994). | ||
| Economic Impact | Fisheries | |
| Increased light penetration and vegetation growth, believed to be caused by C. fluminea's filtering (Phelps 1994), may have been responsible for increased fish populations (Killgore et al. 1989), including increased catches of Micropterus salmoides (Largemouth Bass) by sportsmen (Phelps 1994). | ||