Freshwater biodiversity in the littoral Zone of a Sri Lankan Tank ecosystem with its water quality parameters

Nikiniyawa wewa is one of the tanks situated within the Anuradhapura district, North Central province in the dry zone of Sri Lanka. This tank is surrounded by urban and suburban areas. Both biological and physico-chemical data were collected according to the standard methods. During the survey a total of 21 aquatic plant species belong to 18 families were recorded. This includes 8 submerged, 6 emergent, 3 free floating species and 4 plants which are attached to the substratum and have floating leaves. The highest plant diversity was recorded in non polluted area (H’=2.87) while the lowest recorded in polluted site (H’=2.71). The identified faunal composition was 38 bird species belonged to 22 families consist of 36 breeding residents, 2 winter visitors and 1 endemic species; 11 fish species belonged to 7 families included 10 indigenous species and 1 exotic species; 12 dragonfly species belonged to 3 families included 11 residents and 1 endemic species; 3 amphibian species; 2 reptile species and 1 mammal species. The highest fish faunal diversity was recorded in non-polluted (H’=2.14) site while the lowest in polluted site (H’=0.60). It is observed that although most of the water quality parameters have values within the permissible limits of National Water Supply and Drainage Board (NWSDB) and water of the polluted site had high phosphate level. The fauna and flora species distribution has determined by one or more physicochemical parameters. The biodiversity of aquatic plants and fishes were influenced by water quality parameters such as BOD, colour, electrical conductivity, pH and chloride content and not influenced by temperature, DO and phosphate content.