此物種詳細資訊 San Francisco Bay (Estuary)
來源： Department of Fisheries, 2000-2001
The Asian clam's initial introduction to San Francisco Bay was as veliger larvae transported in ballast water by trans-Pacific cargo ships. First found in San Francisco Bay in 1986, C. amurensis took only two years to spread throughout the bay estuary, irrespective of the sediment type, water depth or salinity. It quickly reached densities of greater than 10 000 individuals per square metre. Within one year the composition of the soft substrate community had changed dramatically, with C. amurensis comprising more than 95 per cent of its biomass (Department of Fisheries, 2000-2001). For more information about invasive marine species in the San Francisco Bay area, see Exotic Species of San Francisco Bay
其他: Studies show that selenium contamination in the benthic food web has increased following the invasion of P. amurensis in the San Francisco Bay area. Selinium is a toxin that threatens higher trophic level species because of its reproductive toxicity and efficient food web transfer (Linville et al 2002).
捕食: Predation by Potamocorbula amurensis has been reported to have an important influence on biomass and species composition of inshore zooplankton. Studies show that within a year of the invasion of P. amurensis, chlorophyll concentration and the abundance of adults of 3 common estuarine copepod species had declined by 53% to 91%. The decline has been attributed to predation of nauplii (the free-swimming first stage of the larva) by P. amurensis (Kimmerer et al.,1994).
改變營養機制: Studies on nutrient supplies in the Sacramento-San Joaquin River Delta, a complex of tidal waterways forming the landward portion of the San Francisco Estuary, indicate that the invasion of the Asian clam has led to a persistent decrease in phytoplankton biomass (chlorophyll a) (Jassby et al., 2002). It has been suggested that invasions by the Asian clam has led to alterations in food dynamics in the San Francisco Estuary. Significant declines in the abundance of at least eight of 13 species were observed. This has been attributed to a major decline in mysid (part of fish diets) abundance caused by the invasion of the C.amurensis. (Feyrer et al., 2003).
改變自然底棲生物群落: Potamocorbula amurensis was found in high abundances (>25, 000m2) at many sites within one year of it invading the San Francisco Bay; it has been reported to contribute to >95% of total individuals and biomass.This has led to an alteration in the benthic community structure (Thompson et al., 1991).
棲地改變: Observations recorded before the invasion of Potamocorbula amurensis in the San Francisco Bay showed that phytoplankton biomass in the upper estuary was low during seasonal periods of high river flow and short residence time, and usually high during the summer-autumn seasons of low river flow and long residence time. Since the widespread invasion and abundance of P. amurensis it has been observed that the summer phytoplankton biomass maximum has disappeared. This change has been attributed to increased grazing pressure by this newly introduced species along with physical effects like river-driven transport (Alpine and Cloern, 1992; Murrell & Hollibaugh, 1998).
經濟 /民生: Potamocorbula amurensis is a suspension feeder, its abundance has led it to become the major consumer of phytoplankton produced leading to a change in the trophic dynamics of the estuary. Its spread therefore would have negative implications on the commercial shell fisheries in nearby areas (Thompson et al., 1991).
最後修改 ： 8/11/2005 2:27:58 p.m.