S2-1.4 Wednesday, Jan. 4 The Influence of Salinity on Zinc and Nickel Toxicity to Two Euryhaline Fish Species BIELMYER, GK*; DECARLO, C; MORRIS, C; CARRIGAN, T; BULLINGTON, JB; Valdosta State University email@example.com
Salinity can rapidly change in estuarine systems on a daily and seasonal basis and these changes may influence the bioavailability and thus toxicity of metals to estuarine organisms. Despite this concern, few studies have characterized the influence of salinity on metal toxicity, particularly using the same fish species. In recent years, there has been increasing interest in the effects of zinc (Zn) and nickel (Ni) on aquatic organisms in environments with varying water chemistry. To address this issue, 96 h toxicity experiments were performed with two euryhaline fish species, Fundulus heteroclitus and Kryptolebias marmoratus. Median lethal concentrations (LC50s) for Zn and Ni were determined for 7-9 d old larvae of each species at six different salinities. For both F. heteroclitus and K. marmoratus, metal toxicity generally decreased with increasing salinity. The LC50 values for both metals were similar between the two species at salinity extremes (0 and 36 ppt); however, at intermediate salinities K. marmoratus was more sensitive than F. heteroclitus. Additional experiments were performed in freshwater supplemented with individual salts to determine which components of saltwater (magnesium, calcium, sodium, and/or chloride) were protective against acute Zn and Ni toxicity to F. heteroclitus. Among the ions tested, calcium was most protective against Zn toxicity, likely due to cation competition for binding sites on the gill. Alternatively, chloride concentration was most protective against acute Ni toxicity likely resulting from increased complexation of the metal. These results provide new data concerning effects of water chemistry on metal toxicity in euryhaline fish and could be useful for development of site-specific water quality criteria.