June 25, 2018 by Graham Merrington & Adam Peters

A new paper has been accepted for publication, with Adam Peters as lead author, on the validation of the nickel biotic ligand model for locally relevant species in Australian freshwaters in Environmental Toxicology and Chemistry. The paper reports on the outputs from a NiPERA funded project that has been ongoing for five years with the collaboration and technical support of Australian scientists from CSIRO, Environmental Research Institute of the Supervising Scientist, Department of the Environment and Energy, Office of Environment and Heritage, consultancy company Hydrobiology, Ecotox Services in Sydney, and NIWA in New Zealand.

Some important Australian freshwaters have relatively low water hardness that fall below the application boundary of the existing European nickel Biotic Ligand Models (NiBLMs) of 2 mg Ca/L. Ecotoxicity testing was undertaken using Hydra viridissima to assess the predictive ability of the existing NiBLM for this species in extremely soft waters. This testing revealed an increased competitive effect of calcium and magnesium with nickel for binding to the biotic ligand in soft water (<10 mg CaCO3/L) than at higher water hardness. Modifications were made to the NiBLM by increasing the binding constants for Ca and Mg at the biotic ligand to account for softer waters encountered in Australia and the more important competitive effect of calcium and magnesium on nickel toxicity.

In order to validate the modified NiBLM, testing was performed on five Australian test species, including two tropical species, in five different field collected Australian natural waters. Overall, no single water chemistry parameter was able to indicate the trends in toxicity to all of the test species. The modified NiBLMs were able to predict the toxicity of nickel to the test species in the validation studies in natural waters better than the existing NiBLMs.

Of considerable importance for other regions of the world, where BLMs have not been developed or tested, this work suggests that the overarching mechanisms defining nickel bioavailability to freshwater species are globally similar, and that NiBLMs can be used in all freshwater systems with minor modifications.