Santschi, Peter H., Laodong Guo, Liang-Saw Wen, Degui Tang, and Matthew QuigleyProceedings: The State of the Bay Symposium IV. January 28-29, 19992010-02-152010-02-151999http://hdl.handle.net/1969.3/25820pgs. 45-49Bioavailability and toxicity of trace metals to aquatic organisms are profoundly affected by the speciation of the element. For example, trace metal bioavailability and toxicity to organisms can be greatly enhanced when metals are present as labile ionic species. Hence, the use of the free ion model is prevalent. However, small hydrophobic metal chelates are bioavailable, and possibly, macromolecular species through coagulation with food particles. Many environmental regulations are still written in terms of the concentration of dissolved forms. However, the traditionally defined dissolved phase contains not just truly dissolved species (defined as <1kDa) but also a considerable portion of colloidal (e.g., 1kDa to 0.4 micrometers) metals (Stordal et al., 1996a; Wen et al., 1997, 1998) and organic carbon (Guo and Santschi, 1997), which have different physical, chemical, and biological properties.bioavailabilitytoxicitytrace metalsChapter