Macrophytes as indicators of the quality and ecological status of waterbodies and for use in removing nutrients and metals
Résumé
Submerged macrophytes respond to environmental fluctuations in nutrient concentrations. A general framework for the assessment of aquatic macrophyte communities has been developed in France, in part using phytosociology tools and water chemical composition. A bioindication scale based on assessment of the macrophyte communities for the water trophic level was established in both hard and soft streams. The relationships between water chemistry and aquatic bryoflora in Eastern France were studied in an attempt to survey the processes of acidification. A bioindication scale based on the degree of acidification was proposed using aquatic plant communities.Subsequently, research in Europe focused on the development of synthetic indices that allowed for the quantification of water quality. Three main macrophyte indices are available for assessing the ecological status of water bodies as tested in accordance with the aims of the Water Framework Directive “WFD”. These are the Mean Trophic Rank (MTR), the Trophic Index of Macrophytes (TIM), and the French Biological Macrophyte Index for Rivers (IBMR). The MTR and IBMR indices could be useful for estimating the ecological status of rivers in accordance with the aims of the WFD. Ecological optima and ranges of submerged macrophytes are, amongst other factors, assumed to be influenced by ecoregion. Different macrophyte-based assessment systems have also been developed for application on lakes to fulfil the demands of the Water Framework Directive of the European Community. Aquatic macrophytes may be successfully used as ecological indicators for assessing and predicting environmental changes. The metal and nutrient bioaccumulation ability of macrophytes was also investigated. The use of aquatic macrophytes for treatment of wastewater to mitigate a variety of pollution levels is a research area of great interest. The removal efficiency of nutrients and of metals by macrophytes has been discussed in this non-exhaustive review. The potential use of these plants in wastewater treatment was also explored.