Exploring the Utility of Macrophyte Metrics for Evaluating the Quality of Rivers in Morocco: Insights from the Macrophyte Biological Index for Rivers

Abstract

Macrophytes not only integrate environmental conditions but also reflect the trophic state of the aquatic environ - ment through several metrics. The lack of knowledge on the biology and ecology of aquatic plants in Moroccan rivers makes it very difficult to establish a comprehensive and effective national metric for assessing the trophic state of rivers. Indeed, the use of one of the European methods, which have been the subject of geographical inter-calibration projects across different countries, particularly those in the Mediterranean region, proves necessary. Given Morocco’s geographic location within the Mediterranean Basin, Macrophyte Biological Index for Rivers (IBMR) was chosen as a method to assess Moroccan running waters. Furthermore, it allowed answering a number of questions about the usage of biological metrics based on macrophytic communities throughout Morocco. The obtained results showed that the IBMR can provide an indication of the overall trophic state of the watercourse, but with well-defined conditions, namely stable hydrological conditions with a significant richness in contributing pollution-sensitive species. Although this macrophyte index showed correlations with the parameters responsible for eutrophication phenomena, it remained less effective in the face of the downgrading parameter. Thus, the particular context of Moroccan watercourses, namely the watercourses of the Upper Oum Er-rbia basin, and the major pitfall that still lies in the knowledge of the ecology of plant groups in Moroccan running waters, can pose a problem in the application of the IBMR index, especially with regard to ubiquitous species that dominate the downstream sites of the studied rivers.