Vascular Hydrophytes for Bioassay of Phosphate Enrichment in Fresh Waters: A Pilot Study

Vascular hydrophytes were shown to have the potential to be useful for straightforward, low-technology, bioassay of fresh water quality, specifically in relation to phosphate enrichment by effluent from sewage treatment works. Field-collected shoots of Elodea canadensis and Callitriche sp. made greater extension growth when incubated in canal water from downstream of discharges, indicating enrichment. This was supported by phosphate analysis and by conventional Selenastrum bioassay. Growth of shoots incubated in phosphate-augmented water from upstream of discharges equalled that in downstream water, confirming that bioassay, using vascular plants, is effective in detecting enrichment by phosphate.