Roditi H A, Fisher N S, Sañudo-Wilhelmy S A
Marine Sciences Research Center, State University of New York, Stony Brook 11794-5000, USA.
Nature. 2000 Sep 7;407(6800):78-80. doi: 10.1038/35024069.
Zebra mussels (Dreissena polymorpha) are widespread and abundant in major freshwater ecosystems in North America, even though the phytoplankton food resources in some of these systems seem to be too low to sustain them. Because phytoplankton biomass is greatly depleted in ecosystems with large D. polymorpha populations and bacteria do not seem to be an important food source for this species, exploitation of alternative carbon sources may explain the unexpected success of D. polymorpha in such environments. Here we examine the possibility that absorption of dissolved organic carbon (DOC) from water could provide a nutritional supplement to zebra mussels. We find that mussels absorb 14C-labelled DOC produced by cultured diatoms with an efficiency of 0.23%; this indicates that DOC in natural waters could contribute up to 50% of the carbon demand of zebra mussels. We also find that zebra mussels absorb some dissolved metals that have been complexed by the DOM; although absorption of dissolved selenium was unaffected by DOC, absorption of dissolved cadmium, silver and mercury by the mussels increased 32-, 8.7- and 3.6-fold, respectively, in the presence of high-molecular-weight DOC.
斑马贻贝（多形饰贝）在北美的主要淡水生态系统中广泛分布且数量众多，尽管其中一些系统中的浮游植物食物资源似乎过低，难以维持它们的生存。由于在多形饰贝数量众多的生态系统中浮游植物生物量大幅减少，而且细菌似乎并非该物种的重要食物来源，利用替代碳源或许可以解释多形饰贝在这类环境中取得意外成功的原因。在此，我们研究了从水中吸收溶解有机碳（DOC）能否为斑马贻贝提供营养补充的可能性。我们发现，贻贝吸收由培养硅藻产生的14C标记的DOC，效率为0.23%；这表明天然水体中的DOC可为斑马贻贝提供高达50%的碳需求。我们还发现，斑马贻贝会吸收一些已与溶解有机物（DOM）络合的溶解态金属；虽然溶解态硒的吸收不受DOC影响，但在存在高分子量DOC的情况下，贻贝对溶解态镉、银和汞的吸收分别增加了32倍、8.7倍和3.6倍。
