Differences in sulfate sensitivity of early development between brackish and freshwater coregonines

Abstract

Sulfate is found naturally in the aquatic environments, but due to various anthropogenic activities the sulfate concentrations in surface waters have increased globally. High levels of sulfate can cause adverse effects on aquatic organisms. In this study we explored the effects of sulfate on the reproduction of two coregonine species, whitefish (Coregonus lavaretus (L.)) and vendace (Coregonus albula (L.)), in Baltic Sea brackish water and soft boreal freshwater. The chronic toxicity tests lasted from fertilization to hatching of the larvae, endpoints being embryonic and larval survival, and size of newly hatched larvae. The chronic 196–214-day tests were conducted in different sodium sulfate (Na2SO4) solutions at water temperatures simulating natural conditions during the egg incubation from autumn to spring. The separate fertilization tests were carried out to measure fertilization success (%). The fertilization and early embryonic phase were found to be the most sensitive periods for sulfate toxicity. The survival in late embryonic phase, hatching and 5-day larval phase was high (>80%). In the acute fertilization tests with brackish water populations, the LC50-values were between 2554 and 2575 mg/L and with freshwater populations between 1107 and 1230 mg/L of sulfate. In the chronic experiments from fertilization to hatching the LC10-values for brackish water populations were between 1800 and 1820 mg/L and for freshwater populations between 335 and 624 mg/L of sulfate. The tolerance for sulfate in freshwater coregonines was significantly lower than brackish water coregonines, but it was in similar range as to what has been observed in other freshwater species.