Response of benthic macroinvertebrates (ephemeroptera, plecoptera, trichoptera) to anthropogenic pressures in a context of climate change in the Ourika watershed (High Atlas of Morocco)

Abstract

Global changes have a significant impact on lotic ecosystems and aquatic wildlife. We analyzed their impact on benthic populations of mayflies, stoneflies and caddisflies (Ephemeroptera-Plecoptera-Trichoptera [EPT]) within the Ourika watershed, located in the High Atlas of Morocco. The inventory of species present in the stations before 2000, and those found after 2000 show that the species richness increased in Oukaïmeden, whose stations are located at high altitude, while it decreased highly in Ourika whose stations are at medium altitude. In Ourika, the specific richness in EPT fell from 37 before 2000 to 24 after 2000, a decrease of 35%. The number of mayflies species decreased from 13 species before 2000, to 9 after 2000; that of stoneflies from 7 to 5, caddisflies from 17 to 10 after 2000. In Oukaïmeden, species richness en EPT increased from 27 before 2000 to 32 after 2000, an increase of 15%. the number of mayflies species increased from 8 species before 2000, to 12 after 2000; stoneflies from 8 to 10, caddisflies from 11 to 10. These changes result from the decline in the quality of the aquatic environment submitted to human pressure in Ourika (domestic wastewater, solid waste, embankment on the banks, shops, dredging...). The aquatic habitat has deteriorated, organic pollution is quite large, biological water quality has declined strongly compared to the period before 2000. In Oukaïmeden, however, the aquatic environment is much less disturbed, disruptions are mostly concentrated within a station, the others being relatively spared. The aquatic habitat is suboptimal, organic pollution has remained low and the biological quality of the water remains good despite a slight decline. The Oukaïmeden appearing as a refuge area for populations of mayflies, stoneflies and caddisflies, the region has great interest in the conservation of species.