Effects of pH on toxicity of As, Cr, Cu, Ni and Zn to Selenastrum capricornutum Printz

Abstract

Acute toxicity tests were conducted to establish the response of Selenastrum capricornutum Printz to sublethal concentrations of As, Cr, Cu, Ni and Zn at a broad range ofpH levels. Cultures were incubated for a period of seven days at pH 4 in standard algal assay media containing sublethal concentrations of metals. At this low pH, growth was depressed for all metals tested. The adjustment of pH to higher levels resulted in increased growth when cultures were treated with As, Cu, or Ni and incubated for an additional 7 days. Toxicity was least at the optimum pH range for growth of the alga.The observation that the toxicity of As, Cu, and Ni to S. capricornutum decreases markedly at pH values above 4.0 may be of ecological importance in the control of acid mine pollution. Ifa high percentage of algae show a similar response to decreasing toxicity with increasing pH, it clearly would be of value to adopt measures which control pH as well as the levels of metals present. It was suggested that algae with a broad pH growth range, such as S. capricornutum, could benefit from the addition of highly alkaline materials to waters where certain metals are present.

What Limits the Productivity of Acid Mine Drainage Treatment Ponds?

“…Zinc has been shown to inhibit phytoplankton growth at concentrations as low as 0.19 mg L -1 , which is within the range found in this study (Table 1; Hargreaves and Whitton 1976;Campbell and Stokes 1985;Sunda and Huntsman, 1998). Furthermore, Zn tends to be more toxic at circumneutral pH and so could still exert an effect in the chemically-treated or biologically-treated ponds (Michnowicz and Weaks 1984;Campbell and Stokes 1985). However, in an AMD-contaminated stream, Niyogi et al (1999) found that an acid-tolerant alga was not inhibited by dissolved Zn concentrations as high as 10 mg L -1 .…”

Impact of Industrial Effluents on Water Quality of Streams in Nakawa-Ntinda, Uganda

“…The recorded influence on stream pH by industrial effluent is similar to previous studies (Muwanga & Barifaijo, 2006;Oladele et al, 2011). According to Michnowicz and Weaks (1984) low pH (< 4.0) increases the toxicity of heavy metals (e.g. As, Cr, Cu, Zn).…”

Effect of nickel on certain physiological and biochemical behaviors of an acid tolerantChlorella vulgaris

“…Michnowicz & Weaks (1984) and Rachlin & Grosso (1991), while working on the effects of pH on metal toxicity in green algae, demonstrated that acidic pH inhibits growth. The present study not only offered support to these earlier findings (see Table 1) but also demonstrated reduction in growth, carbon fixation, 02 evolution, the electron transport chain (data not shown), and the ATP content of the wild-type and acid-tolerant strain of C. vulgaris.…”