Effects of salinity, temperature and food type on the uptake and elimination rates of cd, cr, and zn in the asiatic clamcorbicula fluminea |
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| Authors: | Jung -Suk Lee Byeong -Gweon Lee |
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| Institution: | (1) Department of Biology, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong, China;(2) Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China |
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| Abstract: | Laboratory radiotracer experiments were conducted to determine assimilation efficiencies (AE) from ingested algal food and oxic sediment particles, uptake rates from the dissolved phase, and the efflux rates of Cd, Cr and Zn in the Asiatic clamCorbicula fluminea. Among three elements, AE from both algal and sediment food was greatest for Cd, followed by Zn and Cr. The AEs of tested elements from algal food(Phaeodactylum tricornutum) were consistently higher than those from sediments at a given salinity and temperature. The influence of salinity (0, 4 and 8 psu) and temperature (5, 13 and 21¼) on the metal AEs was not evident for most tested elements, except Cd AEs from sediment. The rate constant of metal uptake from the dissolved phase (k u was greatest for Cd, followed by Zn and Cr in freshwater media. However, in saline water, thek u of Zn were greater than those of Cd. The influx rate of all tested metals increased with temperature. The efflux rate constant was greatest for Cr (0.02 d-1), followed by Zn (0.010~0.017 d-1) and Cd (0.006 d-1). The efflux rate constant for Zn in clam tissues depurated in 0 psu (0.017 d-1) was faster than that in 8 psu (0.010 d-1). Overall results showed that the variation of salinity and temperature in estuarine systems can considerably influence the metal bioaccumulation potential in the estuarine clamC. fluminea. The relatively high Cd accumulation capacity ofC. fluminea characterized by the high AE, high dissolved influx rate and low efflux rate, suggested that this clam species can be used as an efficient biomonitor for the Cd contamination in freshwater and estuarine environments. |
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