Natural freshwater ecosystem ensures the supply of several beneficial services, such as freshwater, foods, medicines, clean air, aesthetic values etc., it may be cut off by indiscriminate discharges of industrial effluents. The present study was carried out to evaluate water quality and freshwater biodiversity in polluted and non-polluted wetlands at three Upazilas (administrative unit) in Gazipur district of Bangladesh. Two wetlands, that is, one polluted and another non-polluted were selected from each Upazila. Data were collected through face to face interview of relevant 450 respondents by prior prepared questionnaire. A total of 71 aquatic species were evaluated under four groups: fish and shellfish (50), plants (10), birds (6) and amphibians (5). The existence of maximum aquatic species was drastically affected in polluted wetlands. Twenty fish and shellfish, 3 plants and 1 amphibian species were extinct from all polluted wetlands. Conversely, 39 fish and shellfish, 1 amphibian and 4 plants species were extinct from Mokeshbeel wetland only. Others were observed as threatened (T), endangered (En), and vulnerable (Vu). But majority of the species were visible (V) in non-polluted wetlands. Average 70-80% respondents articulated these results. Water quality severely deteriorated in all polluted wetlands. The minimum and maximum values of dissolved oxygen (DO) were 0.4 and 2.0 mg/L in polluted and 4.2 and 4.9 mg/L in non-polluted wetlands, respectively. Higher values of Cr and Ni were recorded in polluted waters as compared with the standard. Excessively decreased DO was responsible for the destruction of aquatic biodiversity. Proper discharge of measures may helpful to overcome the present problem and conserve aquatic biodiversity.

Key words: Fish and shellfish, Aquatic plants and birds, Amphibians, Endangered, Extinct, Polluted wetlands.