WATER QUALITY EVALUATION USING BENTHIC MACROINVERTEBRATES, PHYSICOCHEMICAL PARAMETERS AND HEAVY METAL LEVELS IN TWO LAKES (NORTHWESTERN ALGERIA)

In North Algeria, human activities have dramatically deteriorated the water quality of fresh waters and threatened aquatic ecosystem health. These rare hydrosystems deserve special attention because they are an important source of water, supporting the local ecological and environmental balance in this semi-arid region. To monitor the surface water quality of two lakes (Sidi M'hamed Benali and Lalla Setti), benthic macroinvertebrates, physicochemical parameters and heavy metals of the water were studied between May 2017 and May 2018. The results from a collection of 21462 individuals showed that macroinvertebrate assemblages significantly varied between the two lakes. Thirteen orders, 19 families and 64 genus-species taxa were identified for the two lakes, with the most dominant orders belonging to Hexapods, Copepoda and Platyhelminthes (Dugesiidae). The seven taxa collected are tolerant and highly adaptable to various environmental conditions. Thus, tolerant taxa such as the insect families Caenidae (34%) and Chironomiidae (10%) achieved the highest relative abundances in both lakes. The metric index values showed the highest diversity and evenness in Lake Lalla Setti communities. The biotic indices indicated a greater deterioration of water quality in the two lakes. The results of the physicochemical and heavy metal analyses show an ecological state conditioned by the excess of Calcium, CaCO3 and Magnesium, which considerably increase the hardness of the water, to which anthropic pollutants, mainly nitrates and lead, are added.