Assessment of benthic macroinvertebrates diversity and streams quality in the Northern Sahara, Algeria

This study aims to assess the ecological health of Aquatic ecosystems located in the Saharan bioclimatic zone of northern Sahara in Algeria, through a multiparametric approach based on the ecology of benthic macroinvertebrates. Between 2015 and 2017, we investigated five aquatic ecosystems (Wadi Z’mor, Wadi Ithel, Wadi Djedi, Lake Ayata, and Lake Megarine) to evaluate the biodiversity of benthic macroinvertebrates in relation to various environmental factors. These factors include 12 physicochemical water parameters, general habitat characteristics, and the degree of anthropogenic pressure. Benthic macroinvertebrates were collected from various habitat compartments (substrates) during the same period between August 2015 and November 2017. W. Z'mor displayed the greatest substrate diversity, predominantly consisting of pebbles, boulders, sand, solid supports, and vegetation, while the other sites were mostly dominated by sand. The pH levels at the study sites ranged from slightly alkaline to alkaline. Turbidity and suspended solids concentrations were significantly higher in W. Djedi and W. Z'mor, while the average BOD5 across all the studied hydrosystems suggested moderate pollution levels, with W. Djedi, W. Ithel, and L. Megarine showing the highest pollution. Regarding salinity, W. Djedi's waters were slightly brackish, while the other sites ranged from brackish to very brackish. The fauna recorded consisted of 995 individuals, representing 55 genera/taxa across 8 orders and 29 families. The most diverse groups were Coleoptera (24 taxa), Diptera (14 taxa), and Hemiptera (10 taxa), with Diptera and Coleoptera being the most abundant. W. Z'mor and W. Ithel exhibited the highest biodiversity (total richness: 35 taxa; Shannon index > 2.50). The IBGN calculation showed that the hydrobiological quality of the water was poor in W. Djedi, W. Ithel, L. Megarine, and L. Ayata (IBGN 5), while W. Z'mor had average water quality (IBGN 9).