Assessment of Zambezi River Water Quality Using Macroinvertebrates Population Diversity

摘要

Background and Objective: The section of Zambezi river in Katima Mulilo has currently come under intense anthropogenic pressure due to the increasing economic activities in and around the river. The main objective of this study was to assess the river water quality using macroinvertebrates population. Materials and Methods: Samples of macroinvertebrates were collected on bi-monthly basis (January-November, 2015) at four different locations along the Zambezi river in Katima Mulilo. D-net (1μm) was used to trap the macroinvertebrate species using a three-minute single-habitat kick sampling method in which the net was swept five times per sites. At each sampling site, the abiotic factors: pH, temperature, dissolved oxygen and electrical conductivity of the river water were determined in-situ using a hand held multifunction sensor HQ40d portable meter and their levels compared with recommended freshwater quality criteria. Results: Sixty-two macro-invertebrates made up of 9 different species were recorded at two sampling points, Stone city and Bezi bar. The assessment of these macroinvertebrates based on pollution tolerance sensitivity scale revealed 54.84% (highly tolerance), 40.32% (moderately tolerance) and 4.84% (very low tolerance) to pollution categories. In-situ measurement of the abiotic factors revealed pH, temperature, dissolved oxygen and conductivities values of 6.68-8.93, 18.40-28.73°C, 5.01-7.92 mg L^?1 and 37.73-105.27 μS cm^?1, respectively. Conclusion: The various pollution tolerances of the macroinvertebrates recorded in this study suggests varying degree of the river water contaminations. However, the levels of the abiotic factors were within reported safe limits for aquatic organisms. Therefore, further study should be undertaken to establish the chemical components? pollution status of the Zambezi river in order to provide a versatile baseline data for future monitoring of the river quality.