PW08 Aquatic Ecotoxicology II
Exhibit Hall
8:00 AM - Wednesday
(PW125) Acute toxicity of cobalt to mottled sculpin and rainbow trout and implications for establishment of water quality criteria.
Kunz, J1, Besser, J1, Ivey, C1, Ingersoll, C1, Mebane, C2, 1 U.S. Geological Survey, Columbia, MO, USA2 U.S. Geological Survey, Boise, ID, USA
ABSTRACT- The toxicity of cobalt to cold-water fish taxa is of special interest because high levels of dissolved cobalt may occur in streams draining mining areas in mountainous regions, and because no national recommended water quality criteria have been established for cobalt. We evaluated the sensitivity of mottled sculpin (Cottus bairdi) and rainbow trout (Onchorhynchus mykiss) to acute toxicity of cobalt in soft water. Results of previous studies suggest that rainbow trout are more sensitive to cobalt toxicity than several warm-water fish taxa, and that toxicity of cobalt may be hardness dependent, with greater toxicity in soft water. No cobalt toxicity data is available for sculpins, which often co-occur with trout in mining-affected streams in the western U.S. We used mottled sculpins as a surrogate species for toxicity testing, because this has a wide geographic distribution, including many watersheds affected by mining. The wide distribution of C. bairdi also facilitates collection of brood stock for spawning in the laboratory, eliminating the need to maintain permanent laboratory cultures. We tested mottled sculpins produced by brood stock collected in northern Missouri. We determined a 96-hr LC50 of 1.75 mg/L for toxicity of cobalt to swim-up rainbow trout at a hardness of 50 mg/L. This result suggest slightly lower toxicity of cobalt than in published studies of rainbow trout tested in softer water (LC50=1.41 mg/L at hardness of 25 mg/L). Swim-up mottled sculpin were less sensitive to acute cobalt toxicity, with a 96-hr LC50 of 2.5 mg/L. These results suggest that site-specific water quality criteria based on testing with rainbow trout may be adequate to protect sculpins from cobalt toxicity. However, additional testing should be conducted to validate this conclusion, including chronic toxicity tests with mottled sculpin and/or with sculpin species that are resident in mining-affected watersheds.
Key words: acute toxicity, cobalt, sculpin, trout