Abstract
This study investigated the effect of the main physicochemical factors in structuring aquatic macroinvertebrate assemblages of three streams in northern Tunisia. Aquatic macroinvertebrate and water physicochemical surveys were carried out seasonally in 2013, at three pristine sites and three altered sites located, respectively, in the upstream and downstream parts of the streams investigated. Macroinvertebrates were sampled using a kick net and a Surber net, and eight physicochemical factors were measured at the same time. Both biotic and abiotic data were analyzed using STATICO method. A total of 41 macroinvertebrate taxa were collected during the sampling period, and the most dominant taxa were Diptera (Culicidae) and Oligochaeta (Tubificidae). STATICO identified the dissolved oxygen, COD, and BOD5 as the major abiotic factors shaping macroinvertebrate assemblages. This study highlighted the impacts of anthropogenic land-based activities such as urban runoff on the distribution and diversity of macrobenthic invertebrates at the three downstream sites.

Keywords: Anthropogenic impacts, Benthic macroinvertebrates, Water quality, Tunisia