Survival, growth, and reproduction of Hyalella azteca were determined under various test conditions. Reproduction by a cohort begins when the amphipods are 5 to 6 weeks old, peaks at 8 to 12 weeks, and then declines due to continuing adult mortality. Full life-cycle tests can be completed in 12 to 14 weeks at 25 degrees C. Reproduction is poor when only artificial plastic substrate is provided. A substrate of cotton gauze results in dramatic improvements in both reproduction and growth. Better reproduction can be obtained by culturing the amphipods in some sediments, but this makes weekly enumeration difficult. Increased mortality during chronic exposure to cadmium was observed at 1 microgram/L for H. azteca and 3.2 micrograms/L for Gammarus fasciatus. Reproduction during longer exposure was not reduced at concentrations lower than those causing increased mortality within six weeks. Chronic toxicity of pentachlorophenol was observed at 100 micrograms/L for both species. Chronic toxicity to Daphnia magna was similar to that of the amphipods for cadmium, but lower for pentachlorophenol. Amphipods are at least as sensitive as Daphnia to a variety of toxicants during chronic exposure.

Tissue levels of chlorinated dioxins and furans and the physiological and biochemical responses of fish were measured upstream and downstream of a bleached kraft mill in the St. Maurice River, Quebec. Relative to fish 10 km upstream of the source, white suckers (Catostomus commersoni) downstream showed evidence of chemical exposure, chemical metabolism, stress, and altered energy use. Levels of 2,3,7,8–tetrachlorodibenzo‐p‐dioxin and tetrachlorodibenzofuran in gutted whole fish averaged 23 and 260 pg/g immediately downstream of the plant and declined to 18 and 112 pg/g at 95 km downstream. The activity of hepatic aryl hydrocarbon hydroxylase (AHH) was 10X higher immediately downstream and 5X higher 95 km downstream. There were corresponding increases in relative liver size, hematocrit, serum glucose, serum protein, and fin‐ray asymmetries, with a pattern of response that matched enzyme induction. These responses pointed to a strong effluent effect and followed the patterns of tissue contamination by dioxins and furans and of water contamination by chlorinated phenolics and guaiacols. There were strong correlations between AHH induction and tissue contamination. Whereas lipid levels increased at all downstream sites, condition factor decreased at 95 km from the source, indicating that there may be disturbances in energy metabolism. Effects on sexual maturation, as shown by levels of serum hormones and gonad somatic index, were inconclusive.

The addition of 100 micrograms/L of Aroclor 1242 (A1242) or 2,5,2',5'-tetrachlorobiphenyl (TeCB) during 10 week chronic toxicity tests with Hyalella azteca resulted in complete mortality. There were no effects on survival, growth, or reproduction after addition of 30 micrograms/L. Toxic effects were observed at tissue levels of between 30 and 180 micrograms/g on a wet weight basis, and tissue levels appear to be a better indicator of toxicity than levels in water. No toxic effects were observed after additions of up to 2,700 micrograms/L of the coplanar congener 3,4,3',4'-TeCB. H. azteca has the ability to avoid accumulating in excess of 140 micrograms/g 3,4,3',4'-TeCB. The amount taken up was proportional to the amount added in water up to 100 micrograms/L, but was constant at higher additions, possibly accounting for its relatively low toxicity. The low toxicity of the coplanar congener, as compared to the non-coplanar 2,5,2',5'-TeCB, is in direct contrast to the high toxicity of coplanar PCB congeners to mammals and may be associated with slower rates of aromatic hydrocarbon metabolism in amphipods. Polychlorinated biphenyl levels measured in amphipods from Lake Ontario are approximately 100-fold below levels associated with toxicity in H. azteca, but are above levels which, through biomagnification up the food chain, lead to salmonid residues in excess of 2 micrograms/g, a tolerance limit for human consumption.

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