关键词: |
TRAFFIC, NAVIGATION, VELOCITY, STATIONS, DENSITY, DELIVERY, COMPETITION, IMPACT, DISTRIBUTION, SITES, POPULATION, PHASE, SUSPENDED SEDIMENTS, OPERATION, BACKGROUND, VALUE, RIVERS, HABITATS, NUMBERS, MUSSELS, SEDIMENTS, ADULTS, OHIO RIVER, BARGES, COAL. |
摘要: |
Qualitative and quantitative baseline data were obtained at six and four sites, respectively, at a mussel bed located on the Ohio River (river miles 444.4-445.6), near the William H. Zimmer Station, in July 1991. This information, in conjunction with additional data to be collected in future years, will be used to assess the effects of coal deliveries by barge on freshwater mussels (Family: Unionidae). The station began commercial operation in March 1991. Total species richness (23) was similar to that at other large- river mussel beds. The unionid fauna consisted almost entirely of thick-shelled species and was dominated by Quadrula pustulosa (22.79 percent), Amblema plicata plicata (20.25 percent), and Pleurobema cordatum (18.49 percent). The assemblage was characterized by an equitable distribution of species with no clear dominants. Average unionid density (23.2 to 52.4 individuals/sq m) was only slightly less than typical values at similar habitats but not substantially different from values recorded at this bed in 1989 and 1990. Corbicula fluminea density ranged from 472.0 to 780 individuals/sq m, which, although much greater than native unionid density, was similar to that found in most other large-river mussel beds. There was no evidence of competition (either in terms of density or biomass) between native and nonnative bivalves. Populations of dominant unionids consisted of large numbers of intermediate-sized individuals and moderate to low numbers of juveniles and adults. All had multiple age classes and showed evidence of moderately strong recruitment by several recent year classes. Changes in background levels of water velocity and suspended sediments caused by movement of the workboat that shuttles coal to the unloader were measured. These were minor of little significance at the mussel bed. |