Pete and I recently published a paper on an approach for the derivation of site specific water quality standards for zinc which take account of both the bioavailability of the metal and the composition of the local aquatic benthic macroinvertebrate community. We developed this approach because the composition of the ecological communities depends upon a number of factors such as the local habitat and water chemistry, and different ecological communities may show variable responses to chemical stressors as a result of differences in their composition. A specific community which is composed of several sensitive families of invertebrates would be expected to be more sensitive than one which does not include any particularly sensitive families because the local habitat or water chemistry is unsuitable for them. The approach that we developed identified the sensitivity of a large number of benthic macroinvertebrate families to zinc, in order to establish how sensitive any specific community would be.
We believe that this approach has the potential to be important, particularly in cases where costly programmes of measures are considered to achieve compliance with a chemical quality standard. It is likely to be of greatest interest in reconciling differences between assessments of ecological quality based on chemical standards and ecological standards, especially where a chemical standard is failed but the ecological standard is not failed. We considered three sites with different local invertebrate communities and different zinc exposures (low, moderate and high). All of the sites had relatively similar water chemistries, so differences due to bioavailability were small. We were able to correctly classify a site which had failed the EQS for zinc, but maintained a healthy invertebrate community, as well a site which was unimpacted and another site which was impacted.
The paper has been published in Environmental Science and Pollution Research and can be found here: http://link.springer.com/article/10.1007%2Fs11356-013-1720-z#