Applying some biotic indices of macrobenthic invertebrates to assess water quality of Lake Manzala, Egypt

Water and macrobenthic invertebrate (MBI) samples were collected from nine stations of Lake Manzala during spring (May, 2014) and summer (August, 2014). Chemical parameters e.g. Dissolved Oxygen, Biological Oxygen Demand, Total Dissolved Solids, Ammonia, Nitrite, Orthophosphorus, Total Suspended Solids were measured for Nile Chemical Pollution Index (NCPI). Macrobenthic invertebrates were sorted, counted and identified for Biological Monitoring Working Party (BMWP) and Nile Biotic Pollution Index (NBPI) was conducted. The highest number of macrobenthic invertebrates and the best water quality was observed at the stations away from the source of pollution (Legan and Boom Station), while the lowest water quality and the lowest number of species were observed at Bahr El-Bakar and its discharged point. The present study revealed that, the average score of NCBI was ranged between 33 during spring and 29 during summer, indicating heavily polluted ranges (26-35). In this work, 19 MBI species under 18 families were recorded; out of these 8 families are bioindicatory families (Viviparidae, Planorbidae, Lymnaeidae, Thiaridae, Physidae, Neritidae, Tubificidae and Chironomidae) which used in the applied biotic indices. During spring, the average value of NCBI recorded high score, whereas BMWP-ASPT and NBPI-ASPT were decreased being 2.99 and 2.59 respectively. On the other hand during summer, the average value of NCBI recorded low score whereas BMWP-ASPT and NBPI-ASPT were increased. Regression values between the chemical index (NCBI) and BMWP-ASPT Index and NBPI Index showed a non significant values (p value more than 0.05) during spring and summer. So, the present study concluded that, BMWP-ASPT and NBPI-ASPT Indices did not show a good indication to assess water quality of Lake Manzala and they were not matching with chemical index (NCBI) and more developments to these indices are needed to develop them according to the nature of the lake and their dominant macrobethic indicator species.