Abundance, diversity and community structureof macroinvertebrates in an Algerian stream : the Sébaou wadi

Abstract

We investigated the abundance, diversity and community structure of mayflies (Ephemeroptera), stoneflies (Plecoptera) andblackflies (Diptera : Simuliidae) in the Sébaou basin (Algeria). Fifty-five species were collected (i.e. 22 mayflies, 14 stonefliesand 19 blackflies species) in 18 sampling sites located in both main streams and tributaries of the Sébaou river (Great Kabylie,North Algeria). Analysis of species diversity of the three considered taxa showed an altitudinal gradient with maximal diversityin the piedmont and low altitude mountain areas (from 200 to 500 m), which provided the most heterogeneous habitats to thebenthic fauna. In contrast, the low diversity of the lowland sites was due to high water temperatures, reduced summer dischargeand anthropogenic disturbances. In the same way, the low diversity of the high mountain areas can be attributed either to lowwater temperatures or high fluctuation in daily temperature. Three species assemblage groups are revealed, the first two are relatedto an upstream-downstream gradient, with headwater sites characterised by stoneflies species and middle stream sites by ahigh mayfly and blackfy diversity and abundance. The third group was identified as spring sites characterised by a low abundanceand occurrence of stonefly species.Both altitudinal species diversity gradient and species assemblage of the Sébaou wadi were different from European and temperateareas, revealing that the accentuated North African Mediterranean climate could induce changes to both species and communitystructure. These results provide insights to the influence of some environmental features on aquatic insect species distributionand community structure in North African streams.