in Sri Lanka - Ministry of Environment

(saltpans, reservoirs, gravel/brick pits, sewage/treatment ponds and canals) (Kotagama andBambaradeniya, 2006).Wetland ecosystems are amongst the most productive ecosystems in the world that supportmany kinds of life. Wetlands always have influenced humans from the time of early civilization,which first arose along the edges of rivers in the fertile soils of the flood plains. They provide anarray of human benefits including food and drinking water, raw material, and medicinal herbs.Further, many waterfalls and major rivers have been utilized for generating hydro-electricity.Wetlands are considered as the transitional zone between land and water and provide severalecological functions such as ground water buffering and reducing pollution. They also providerecreation sites full of wildlife; Bundala National Park, Anawilundawa Sanctuary and WilpattuNational Park being few of them. Aquatic flora play a key role in these wetland ecosystemsproviding habitats to fauna. Amongst the total inland vertebrate species in Sri Lanka, about30% are ecologically dependent on wetlands (Kotagama and Bambaradeniya, 2006). Further,over 50% of the migratory birds that visit Sri Lanka annually are directly dependent on wetlandsfor food and shelter. Moreover, the future survival of approximately 32% of the nationallythreatened vertebrate species in Sri Lanka is dependent on wetland ecosystems of the island(Kotagama and Bambaradeniya, 2006).Prominent plants and DistributionThe definition of the term "aquatic" can be subject to various interpretations. Aquatic plantsor wetland plants themselves however, do not always fit rigid definitions. Aquatic plants arealso referred to as hydrophytes or aquatic macrophytes. The wetland plants do not belong toa particular plant family, have rather derived from several terrestrial families, and are adaptedto live in aquatic environments by developing similar modifications. These include largeair spaces within their leaves, stems and roots, presence of both underwater and floatingleaves, thin and often finely dissected leaves, thick waxy leaves, and specialized pollinationmechanisms. In addition, many aquatic plants also show a great variation in growth patterns.For instance Water-hyacinth, floating at the water surface has typical bulbous leaf petiole, butwhen rooted the leaf-petiole elongates losing its bulbous form. The species composition andthe appearance of an aquatic ecosystem vary both with time and among the wetland sites.The marshes are characterized by tall grasses, sedges and herbaceous plants while lakevegetation is characterized by emergent plants towards the periphery and floating aquaticsdominating the water surface.Four categories (growth forms) of aquatic plants may be recognized on the basis of theirattachment to the soil and their position in relation to the water surface:(1) Free-floating plants: Plants that are floating at the surface or beneath the surface. Theyare typically not rooted to the soil at the bottom, but in shallow water or where they arestranded on the shore by a drop in the water level, they may become rooted. The leavesmay stand above the surface (e.g. Pistia and Eichhornia), at the surface (e.g. Wolffia), orthe whole plant may float beneath the surface (e.g. Ceratophyllum). These plants occur inshallow or deep water.(2) Plants rooted at the bottom, with leaves floating at the surface: These plants could beeither with short or long rhizomes at the bottom, and large leaf-blades at the ends of long187