Abstract-The protectiveness of USEPA ambient water quality criteria for copper (Cu) and zinc (Zn) was tested using the snail Leptoxis praerosa in short-and long-term artificial stream tests. Acute criteria were tested in 96-h survival tests. Chronic criteria were tested by comparing cellulolytic enzyme activity impairment, bioconcentration, and survival in 14-, 20-, 30-, and 114-d exposures. Significant Cu bioconcentration occurred within 40 d at the chronic Cu criteria concentration, followed by significant cellulolytic enzyme activity impairment within 54 d. Significant bioconcentration and enzyme activity impairment occurred within 40 and 54 d, respectively, at the chronic Zn criteria concentration, but survival was much higher than in Cu-exposed snails. Approximate additive effects were seen in combination treatments of Cu and Zn. Similar patterns of effects were seen from both increased exposure duration and concentration. This research concluded that criteria based on abbreviated chronic tests may be underprotective for some sensitive taxa when exposures are prolonged.

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The protectiveness of USEPA ambient water quality criteria for copper (Cu) and zinc (Zn) was tested using the snail Leptoxis praerosa in short‐ and long‐term artificial stream tests. Acute criteria were tested in 96‐h survival tests. Chronic criteria were tested by comparing cellulolytic enzyme activity impairment, bioconcentration, and survival in 14‐, 20‐, 30‐, and 114‐d exposures. Significant Cu bioconcentration occurred within 40 d at the chronic Cu criteria concentration, followed by significant cellulolytic enzyme activity impairment within 54 d. Significant bioconcentration and enzyme activity impairment occurred within 40 and 54 d, respectively, at the chronic Zn criteria concentration, but survival was much higher than in Cu‐exposed snails. Approximate additive effects were seen in combination treatments of Cu and Zn. Similar patterns of effects were seen from both increased exposure duration and concentration. This research concluded that criteria based on abbreviated chronic tests may be underprotective for some sensitive taxa when exposures are prolonged.