No abstract

Macrophytes are one of the main components of the aquatic ecosystem. They are used in several countries as metrics for the ecological assessment of hydrosystems. The objective of our study was to evaluate the suitability of the Macrophyte Biological Index for Rivers (IBMR) to determine a trophic level in the upper Oum Er Rbia basin (Morocco) and to understand physicochemical parameters of water that govern the distribution of macrophyte species. CCA analysis was used to relate the distribution of macrophytes to hydrochemical parameters of water. The CCA analysis shows that the distribution of macrophytes was more correlated with abiotic parameters (EC, WT and DO) than nutrient parameters (PO4-P, NO3-N, NO2-N, NH3-N and CODMn). The recorded values of IBMR in the upper Oum Er Rbia basin indicate that the trophic level of the studied rivers ranged from “moderate” to “very high”. Pearson's correlation coefficient showed that the IBMR is more correlated with the abiotic parameters such as WT and EC and does not show any significant correlation with the content of PO4-P and NH3-N in water, which makes the IBMR index unreliable for assessing the trophic status related to phosphate and ammonia concentrations in our lotic waters.

Macrophytes represent a functional compartment that plays multiple and fundamental ecological roles in aquatic environments. They are linked with the other compartments of hydrosystems, both abiotic and biotic, which gives them the ability to integrate environmental conditions and reflect the trophic state of watercourses.Nevertheless, macrophytes in Moroccan rivers have been rarely studied. Thus, the main objective of the present work is to study these plants by determining the environmental factors that control their presence and distribution in the watercourses of the upper Oum Er-rbia basin (Middle Atlas Morocco). From June 2018 to June 2019, 14 sites spread over five rivers were monitored monthly to describe macrophytic communities and investigate their ecological determinism. We used a principal component analysis to establish each river's typology and a detrended correspondence analysis to explore macrophyte assemblages. Canonical correspondence analysis was used to determine the hydrochemical parameters of water that govern the development and distribution of macrophyte species in the upper Oum Er-rbia basin. The Amengous river stands out from the other surveyed rivers for its exceptional richness of macrophytic species. This richness is often associated with the enrichment of the aquatic environment by nitrogen and phosphate inputs. Furthermore, in some rivers, such as Oum Er-rbia, nutrient enrichment plays a secondary function in comparison to the hydromorphological descriptors that tend to be more important for macrophyte composition and distribution.

No abstract