Speciation of nickel and its toxicity to Chlorella sp. in the presence of three distinct dissolved organic matter (DOM)

Effect of Dissolved Organic Matter Concentration and Source on the Chronic Toxicity of Copper and Nickel Mixtures to Chlorella sp.

“…Dissolved organic matter is of particular interest because it has the ability to not only complex metals and reduce their bioavailability but also to directly compete for binding sites on the organism and have direct effects on the physiology of the organism (Wood et al 2011). Previous work with the specific DOM isolates used in the present study and their effects on single‐metal toxicity and lability has shown that DOM concentration and source significantly change the toxicity of copper (Cu; Macoustra et al 2019, 2020a), but not nickel (Ni; Macoustra et al 2020b), to Chlorella sp. It is not yet clear whether this means that metal‐mixture toxicity will be additive (noninteraction) or show interaction, that is, more toxicity than expected (synergistic) or less toxicity than expected (antagonistic).…”

“…The effects of Cu/Ni mixtures were investigated using a full‐factorial design, with Cu and Ni concentrations corresponding to the 10 to 50% effect concentrations (EC10–EC50) previously reported for Cu by Macoustra et al (2019) and for Ni (Macoustra et al 2020b). These authors showed that Chlorella sp.…”

“…Both DOM were collected during the 2016 Australian dry season, from seasonally fluctuating tropical freshwaters (Holland et al 2018). From previous work with these DOM and single exposures to Cu (Macoustra et al 2019(Macoustra et al , 2020a and Ni (Macoustra et al 2020b), Appletree Creek DOM was found to be significantly more protective against metal toxicity than Lake Eacham DOM. Dissolved organic matter was isolated directly from the freshwater and collected in acid-washed polyethylene carboys following reverse osmosis, as recommended by Serkiz and Perdue (1990).…”

“…In contrast, both DOM concentration and source had little effect on Ni toxicity to Chlorella sp. (Macoustra et al 2020b). It should be noted that the differing effect of DOM on Cu and Ni was expected because Cu binds much more strongly to DOM compared to Ni.…”

“…The DOM treatment concentrations were achieved by diluting the DOM concentrate with the synthetic freshwater. The DOM source effects on Cu and Ni mixture toxicity were investigated using Appletree Creek DOM (terrestrial DOM, highly protective) and Lake Eacham DOM (microbial DOM, minimally protective; Macoustra et al 2019Macoustra et al , 2020aMacoustra et al , 2020b.…”