Acute and Chronic Toxicity of Zinc to the Mottled Sculpin Cottus Bairdi

Abstract

The acute and chronic toxicity of zinc to wild mottled sculpin (Cottus bairdi) was measured with 13-d and 30-d flow-through toxicity tests, respectively. Exposure water hardness was 48.6 mg/L as CaCO3 and 46.3 mg/L as CaCO3 in the acute and chronic tests, respectively; pH was slightly above neutral; and temperature near 12 degrees C. The median lethal concentration (LC50) after 96 h was 156 microg Zn/L, but decreased with exposure duration to a median incipient lethal level (ILL50) of 38 microg Zn/L after 9 d, the lowest zinc LC50 reported for any fish species. The 30-d chronic no-effect and lowest-effect concentrations were 16 microg Zn/L (no mortality) and 27 microg Zn/L (32% mortality), respectively. The ILL50 was 32 microg Zn/L. No sublethal growth differences were observed during the chronic test. Analysis of the results from these tests suggested that mottled sculpin may experience acute and chronic toxicity at zinc concentrations lower than any other fish species tested to date. Protection of aquatic communities in stream reaches contaminated by metals seem to require determination of zinc toxicity to lotic species other than trout and other species amenable to aquaculture.

Sensitivity of mottled sculpins (Cottus bairdi) and rainbow trout (Onchorhynchus mykiss) to acute and chronic toxicity of cadmium, copper, and zinc

“…Our BLM-normalized copper acute value for mottled sculpins ranked ninth out of 28 listed aquatic taxa, and our chronic value ranked second of 13 taxa. This finding is consistent with results of previous toxicity tests with mottled sculpins collected from the White River in Colorado [20,21]. Results of our tests indicate that current recommended WQC for cadmium, copper, and zinc adequately protect rainbow trout but may not adequately protect mottled sculpins.…”

“…The inconsistent results of previous toxicity tests with sculpins may be due in part to differences in the age and size of the sculpins tested. Woodling et al [20] and Brinkman and Woodling [21] reported that mortality of mottled sculpins exposed to zinc continued well past the typical 96-h test period for acute toxicity tests. Differences in test duration also may have affected results Table 1.…”

“…Results of some field and laboratory studies suggest that sculpins may be no more sensitive than salmonids to elevated concentrations of metals [11,18,19]. Field-collected sculpins used for laboratory toxicity testing were typically greater than 30 mm in length [20,21], a size range that is typically achieved after a full growing season in cool-water streams of North America [14], whereas for salmonids (and other fish species), sensitivity to metal toxicity is typically greatest during early life stages (e.g., [22]). The inconsistent results of previous toxicity tests with sculpins may be due in part to differences in the age and size of the sculpins tested.…”

Zinc toxicity to the mottled sculpin (Cottus bairdt) in high-hardness water

“…Hardness, conductivity, and dissolved zinc levels at the collection site were 240 mg/L as CaCO 3 , 454 μs/cm, and <10 μg Zn/L, respectively. The fish were collected, transported, received, and maintained at the Colorado Division of Wildlife Toxicology Laboratory in Fort Collins, Colorado, USA, as previously described [3]. After a 26‐d holding period, well water was added to dechlorinated Fort Collins municipal tap water to increase the water hardness to 150 mg/L as CaCO 3 .…”

“…Existing U.S. Environmental Protection Agency (U.S. EPA) criteria and various stream restoration objectives may not be adequate to protect diverse aquatic communities if sculpin are more sensitive to zinc than trout species. Laboratory tests demonstrated the mottled sculpin, Cottus bairdi , was extremely sensitive to zinc in soft water [3]. Sensitive species must be protected to ensure that appropriate water quality criteria and restoration objectives are chosen for zinc‐contaminated stream reaches.…”