Total Dissolved Solids Significance to Fish and Aquatic Life
Some fish are adapted to living in more saline waters and a few species of fresh water forms have been found in natural waters with high dissolved salt concentrations of 15,000 to 20,000 mg/L. Fish can become acclimatized slowly to higher salinities than those to which they are accustomed, but fish in waters of low salinity cannot survive sudden exposure to high salt concentrations such as those resulting from discharges of oil well brines.
Among inland waters in the United States supporting good mixed fish fauna, about 5% have a dissolved solids concentration under 72 mg/L, about 50% under 169 mg/L and about 95% under 400 mg/L.
Finally, dissolved solids may influence the toxicity of heavy metals and organic compounds to fish and other aquatic life. This takes place primarily because of the antagonistic effect of hardness on metals. Chromates, coppers, cyanides, detergents, phenolic compounds, zinc and several other substances are generally more toxic in distilled water than in hard water of high dissolved solids.