The role of Pondweed (Potamogeton spp) beds as an important micro-ecosystem in Embillakala lagoon of Bundala National Park; A Ramsar wetland in Sri Lanka

Abstract

The present study focused on the ecological role of aquatic macrophytes on micro ecosystem diversity of pondweed beds in Embillakala lagoon of Bundala National Park. The taxonomic investigation indicates that pondweed beds of Embillakala lagoon may comprise of a hybrid of Potamogeton crispus (Linnaeus, 1753) and Potamogeton nodosus (Poiret, 1788). The study compared the physico-chemical parameters and biological parameters between the pondweed beds and non-weedy localities of the lagoon. Mean dissolved oxygen level and the BOD5 were respectively significantly higher in pondweed beds (8.92±0.1mg/l; 1.7±0.3mg/l) in contrast to non-weedy localities (5.35±0.3mg/l; 1.3±0.1mg/l) and the mean nitrate concentration was also significantly higher in pondweed beds (1671.16±606.2pg/l) when compared with non-weedy localities (133.14±22.5pg/l). Mean suspended solids were comparatively lower in pondweed beds (193.24±116.4mg/l) than in non-weedy localities (222.6±156.5mg/l). Means of dissolved phosphate level (78.1±35.0pg/l), gross primary productivity (0.56±0.1mg/l/h), salinity (2.57±0.28ppt), alkalinity (3.5±1.2mmol/l) and suspended solids were not significantly different between pondweed beds and non-weedy localities. Results showed a significantly (p<0.01) higher abundance of microcrustaceans (Phyllodiapotomus annendalai, Cyclops minutus, Cypridiopsis sp), prawn larvae and insect larvae in pondweed beds in contrast with non-weedy localities indicating the value of the pondweed beds as a larval feeding ground. Benthic mollusc species Phos senticosus and Bithynia tentaculata were also abundant in pondweed beds. As shown by the present study, pondweed beds exhibit a specific ecological identity. Further studies on pondweed beds and non-weedy localities are encouraged as a useful indicator to understand the micro-ecosystem dynamics and diversity in Bundala water bodies. Regulation of the growth of pondweed beds in Embillakala lagoon may be a useful management tool