Protecting aquatic ecosystem health : are water quality objective realistic ?

Many regulatory authorities set water quality objectives or thresholds based on nutrient concentrations to safeguard aquatic ecosystem health. But do these criteria adequately assess the biological and ecological status? Our research has been focussing on the performance of constructed wetlands for water quality improvement and ecosystem health. In this paper we present data on macroinvertebrate species richness from two wastewater treatment wetlands and two stormwater treatment wetlands. Despite nutrient concentrations exceeding water quality objectives all four wetlands supported a diverse assemblage of macroinvertebrates, including sensitive taxa. From our study we concluded that water quality objectives may be too stringent and that aquatic plants are more important for macroinvertebrate richness. Thus, constructed wetlands are effective for both water quality improvement and aquatic biodiversity.