Exploring factors driving macrophytes in rivers—A case study in Middle Atlas Morocco

Abstract

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.

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

“…Bryophytes are represented by one moss species (4.34%), and bacteria are represented by two taxa (8.69%). It was noted that the contributing species constitute only 28% of all the inventoried species in the same sites between June 2018 and June 2019 (Nouri et al, 2022).…”

“…The low values of IBMR and its instability can be explained by a low richness in contributing species (Demars et al, 2012;Maissour and Benamar 2019). Thus, the Oum Errbia river is characterized by the dominance of algal flora, notably Spirogyra sp., Vaucheria sp., and Cladophora sp., which are considered ubiquitous taxa (Nouri et al, 2022), they can grow to the detriment of sensitive species and directly affect the IBMR score (Treguier and Lietout 2019). In three months (June 2018, May, and June 2019), the St-Chbk02 site shows a "high" trophic level.…”