Plant and Benthic Macroinvertebrates Communities in the Headwater Region of a Stream: Case Study Waturawa Ela a Tributary of Ginganga, Deniyaya.

Abstract

The headwater region is a unique'ecosystem with unique characteristics. However, these habitats have been affected due to tea cultivations, deforestation and monospecific reforestation. To fill the scarse of information gap in such ecosystems. present study was conducted to survey the benthic and plant communities in Waturawa Ela, a tributary of the Ginganga in Deniyaya, Matara from October 2017 to August 2018. Samples were collected bimonthly and in each field visit, plants and macrobenthos were examined together with physico chemical parameters. For plants, observations were made across the stream at the headwater region while random macrobenthos samples were collected using a surber sampler. Physicochemical properties of water were also examined. Headwater region of this stream is totally covered with a dense canopy of tree fern (Cyatheasp) while there are no true aquatic macrophytes inside the stream. The substrate of the headwater stream is a rocky and gravel and it was covered with an array of lower plants including bryophytes and liverworts. Water quality parameters were within the unpolluted standards i.e dissolved oxygen (8.8 -11.1 mg/L), biological oxygen demand (0.07-0.08 mg/L), pH (7.0-7.1), conductivity (20.1-21.9 mS).The larval stages of the Tricoptera, Plecoptera, Ephemeroptera (EPT taxa) were found at the head water region and the EPT index was reported as 5.2 ± 0.9. In addition, the larval stages of the Psephenidae and the Elmidae beetels were observed. Family Perlidae was the dominant plecopteran group while the Hydropsychidae dominate the Order Tricoptera. Ephameropterans were dominated by Leptophlebiidae. Elmidae and Psephenidae families which belong to Order Coleoptera were able to identify within the site. Euphaeidae which commonly refers as damselflies was the dominant group of the order Odonata. Both water quality and the abundance of sensitice macro invertibrates indicated the unpolluted condition of the study site.