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 Kokemäenjoki whitefish eggs and sperm during fertilization, embryos and larvae were exposed in the long-term 175-day incubation to seven different sodium sulfate (Na ₂ SO ₄ ) concentrations from 44 to 2 000 mg SO ₄ 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 SO ₄ 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. LC ₅₀ -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.
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