Sulfate toxicity to early life stages of European whitefish (Coregonus lavaretus) in soft freshwater

Sulfate occurs naturally in the aquatic environment but its elevated levels can be toxic to aquatic life in freshwater environments. We investigated the toxicity of sulfate in humic, soft freshwater to whitefish (Coregonus lavaretus) from fertilization of eggs to hatching i.e. during the critical phases of whitefish early development. Anadromous Kokemadenjoki whitefish eggs and sperm during fertilization, embryos and larvae were exposed in the long-term 175-day incubation to seven different sodium sulfate (Na2SO4) concentrations from 44 to 2 000 mg SO4 L-1. Endpoint variables were the fertilization success, offspring survival and larval growth. Egg fertilization and early embryonic development were the most sensitive developmental stages of whitefish to sulfate, although the fertilization success and survival of embryos decreased only in the highest concentration of 2 000 mg SO4 L-1. The survival during late embryonic period, hatching and the 5-day larval period was high and no difference between the control and sulfate treatments were observed. LC50-values of sulfate for early embryonic period and for the entire embryonic and larval period was 1 413 and 1 161 mg L-1, respectively. The NOEC (No-observed Effect Concentration) of sulfate for the both periods was 1 207 mg L-1. The tolerance of whitefish early stages to sulfate toxicity seems to be on the same level as the tolerance of other salmonids' early stages.

Automated summary

Sulfate's toxicity to whitefish early development primarily affects fertilization and early embryonic development stages, with decreased fertilization success and embryo survival in high sulfate concentrations. However, the tolerance of whitefish embryos and larvae to sulfate exposure is relatively high, with no significant differences in survival observed between control and sulfate treatments during late embryonic and larval periods. The LC50 values for sulfate indicate its relatively moderate toxicity to whitefish early development stages, comparable to other salmonids.