Attached‐algal abundance altered by individual and combined treatments of zinc and pH

Abstract

Attached‐algal communities were employed to test the U.S. Environmental Protection Agency's (EPA) guidelines for zinc (Zn) and pH. The EPA criterion for Zn is 0.047 mg/L, and the EPA effluent standard generally requires that discharge water fall between pH 6 and 9. The experiment was designed to determine whether algal community composition and abundance would be altered by (a) pH 6 or 9, (b) 0.05 mg/L Zn, or (c) the combination of pH 6 or 9 and 0.05 mg/L Zn. Stream mesocosms were continuously supplied with natural water from the New River, Virginia, USA. Established (12‐d colonization) communities on artificial substrates were sampled on days 0, 5, 10, 20, and 30 after treatment began on 9 July 1985. Total algal abundance increased in pH 6 treatment. Treatments of pH 6 and 0.05 mg/L Zn reduced abundance of species characteristic of control mesocosms. These species were replaced by species characteristic of 0.05 mg/L Zn and pH 6 mesocosms. These changes occurred even though these levels are considered “safe” by EPA. Community composition did not differ significantly between ambient (pH 8.5) and pH 9 treatments. Although further research is needed, one might speculate that this change in community composition may have potential ecosystem effects by reducing food quality from diatoms to green algae that may inhibit higher level consumers.

Laboratory and field responses to cadmium: An experimental study in effluent‐dominated stream mesocosms

“…For example, Genter et al [53] found snail and zinc treatment to alter periphytic biomass and community structure. Others found zinc treatment of 50 μg/L to reduce diatom abundance and increase dominance of green algae in periphytic communities [54]. Increased biomass but not primary productivity may have resulted if tolerant but less productive green algae contributed to our biomass measures.…”

Metal toxicity inferred from algal population density, heterotrophic substrate use, and fatty acid profile in a small stream

“…A widely distributed diatom, A. minutissimum is sensitive to organic (biochemical oxygen demand or saprobic) pollution [34] yet tolerant to at least some metals [17]. The patchy distribution of this taxon is not strong evidence to support the hypothesis that it occurs because of metal stress, but this spatial variation has been observed previously [11,13,14,40,41].…”

Metal Toxicity Inferred From Algal Population Density, Heterotrophic Substrate Use, and Fatty Acid Profile in a Small Stream

“…A widely distributed diatom, A. minutissimum is sensitive to organic (biochemical oxygen demand or saprobic) pollution [34] yet tolerant to at least some metals [17]. The patchy distribution of this taxon is not strong evidence to support the hypothesis that it occurs because of metal stress, but this spatial variation has been observed previously [11,13,14,40,41].…”