Toxicology tests with aquatic animals need to consider the trophic transfer of metals Nicholas S. Fisher , Sharon E. Hook Marine Sciences Research Center, State University of New York, Stony Brook, NY 11794-5000, USA Abstract Water quality criteria for metals have largely been based on toxicity tests in which organisms are exposed to dissolved metals, often at concentrations that exceed by several orders of magnitude those which are found even in contaminated waters; these tests assume that ecological impacts can be extrapolated from acute toxicity assessments. We have shown that when marine copepods are exposed to metals (Ag, Cd, Hg, Se, Zn) through their diet the reproductive capacity decreases by up to 75% because fewer eggs are produced and the hatching success of the eggs which are produced is diminished. These sublethal effects occur at metal concentrations that are 2  /3 orders of magnitude below acutely toxic concentrations. Metals accumulated in copepods by trophic transfer deposit in internal tissues, and only modest increases above background levels can depress reproductive capability. Metals accumulated from the dissolved phase deposit primarily on external surfaces, where they have negligible effects at environmentally realistic concentrations. Toxicity tests must consider the bioaccumulation of metals from dietary exposure in order to account for sublethal effects at metal concentrations that are comparable to those in contaminated waters. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Zooplankton; Copepods; Metals; Eggs; Bioaccumulation 1. Water quality criteria and risk In the US, the Clean Water Act stipulates that discharges of toxic substances must not interfere with environmental processes. Specifically, public water supplies, fish, shellfish and wildlife, recrea- tion, agriculture, industry and navigation all must be protected. Clearly, different societal values must be balanced in regulating toxic discharge and protecting all these interests. To achieve this goal, water quality criteria, which stipulate con- centrations that contaminants should not exceed, are set by local, state and federal regulatory agencies. Ideally, these criteria are set at levels low enough to protect wildlife without unduly restricting industrial activity. Water quality criteria must be set for thousands of sites and chemicals on an annual basis, with a consequent element of pragmatism to test design (Wood et al., 1997). Risk must be analyzed quickly, cheaply, replicably and in a way that is  Corresponding author. Tel.:  /1-631-632-8649; fax:  /1- 631-632-8820 E-mail address: nfisher@notes.cc.sunysb.edu (N.S. Fisher). Toxicology 181  /182 (2002) 531  /536 www.elsevier.com/locate/toxicol 0300-483X/02/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII:S0300-483X(02)00475-4