The use of macroinvertebrates in water quality monitoring : a preliminary study on the bioassessment methods for watercourses in Bangladesh

Biological assessment methods based on macroinvertebrates, in conjunction with traditionalphysical and chemical methods have been widely used as an integral part of water qualitymonitoring in many countries. Biological assessment of the health of biotic communities inreceiving waters offers several important advantages over chemical-based approaches. Becauseorganisms integrate environmental conditions over a long period of time as they are constantlyexposed to their ambient environment, where as physical and chemical analysis is instantaneousin time when the sample was collected. At the same time, biological assessment methods oftenare cheaper than chemical methods. Water quality monitoring in Bangladesh is limited tophysicochemical analysis. Therefore, application of biological assessment method for river waterquality is still a new field in Bangladesh.The study area chosen for this research project is located in the greater Dhaka district where theBalu river flows from north to south towards the Shitalakshya river. Macroinvertebrates weresampled from different sites of the river ranging from relatively unpolluted to grossly pollutedsites during the period of October to December 2005 and at the same time associatedphysicochemical parameters of the water quality were measured. Macroinvertebrates wereidentified up to family level with little exception. Taxa richness, diversity and biotic indices werecalculated and evaluated with respect to physicochemical water quality variables, using graphicalmethods.The results show that biological assessment based on macroinvertebrate communities providesuseful information about water quality by displaying response to pollution. Of the five indicestested four found to be promising namely, Taxa richness, BMWP, BMWP-ASPT andCommunity Loss Index to use in Bangladesh. These four indices performed well in theassessment of the study sites and the description of the pollution gradient adequately. However,local modifications e.g. inclusion of local taxa and modification of the sensitivity scores of theindicator organisms are necessary to improve the performance of the biotic indices.Multiple indices have been recommended for assessment of organic pollution status of the riversin Bangladesh using macroinvertebrates. These indices appear to be suitable indicators forassessing the progress towards achievement of Millennium Development Goal 7: Target 9 inprotection and restoration of freshwater ecosystems in Banglades