Distribution and Composition of Aquatic Macrophytes in Santhapettai Lake of Villupuram District in Tamil Nadu

. Macrophytes are important component of the aquatic ecosystem and broad changes in the abundance of individual species and community composition provide valuable information on how and why an ecosystem might be changing. Santhapettai lake is one of the biggest fresh water lake in Villupuram district, Tamil Nadu. The physico-chemical parameters were analysed for one year (October 2012-September 2013). Quadrates were laid randomly and extending from shoreline towards the lake center. The macrophytes falling in each quadrate were sorted species wise, identified and data were recorded. The plants have been identified from fresh materials with the help of different floras. In this present investigation, a total of 33 species belonging to 23 families and 28 genera were identified under and monocotyledons. Further, the plants were classified in morphological group as floating (7), submerged (1), submerged anchored (13), floating leaved (1) and emergent anchored (11). The coverage/spread of macrophytes along the shorelines was higher compared to the centre of the lakes where the species composition was found reduced. Assessment of biota, continuous monitoring and conservation lake are the important components to safeguard the biological wealth of lentic and lotic freshwater ecosystem.


INTRODUCTION
Biodiversity means the assets of life forms found on earth in the form of millions of different plants, animals and microorganisms, which are further diversified with vast potential of future creation of the biodiversity from the ocean of genomic diversity at the effectively functional level with in living biomass, the genes the contain and the intricate system the form. Biological diversity also means the variability among living organisms from all sources and ecological complexes of which they are part and includes diversity within species or between species and of ecosystem. In aquatic habitat, biodiversity of organisms depend on availability and quality of water. As water is an essence and elixir of life on the earth and that water totally dominates the chemical composition, abundance, productivity and physiological conditions especially the indigenous population of aquatic organisms. Therefore the nature and health of any aquatic community is an expression of quality of water.
Indian subcontinent is very rich in fresh water resources. The Indian fresh waters are under considerable threat owing to the fast face of development. A survey by NEERI shown that 70% of India's fresh waters are polluted by conventional standards. Although rivers and lakes are most important water resource in India for purpose like drinking water supplies, irrigation and fisheries. Fresh water lakes and reservoirs are also very important water resources in this country and in many areas constitute only available water.
The inland fresh water ecosystem, both lentic and lotic contributes a greater fraction towards the available water resource on the planet which, is now being increasingly subjected to greater stress from various human activities. The physico-chemical and biological characteristics of water depends upon several factors including the location of water body, type of sewage and domestic waste disposal, localized human population in surrounding and their activities. As a result large quantities of organic and inorganic nutrients are added. The enrichment of nutrients also occurs due to disposal of domestic and in industrial effluents from surrounding areas, which supports the growth of a variety of macrophytes and microbes in aquatic system. Some of these organisms in aquatic system assume paramount signification either as biological indicator or as an agent in self-cleaning process.
Aquatic plants (macrophytes) are of important component of lake because they provide food and habitat for invertebrates, fishes and wild life. The aquatic plant community or macrophytes comprises a diverse group of macrophyte organisms including angiosperms, ferns, mosses, liverworts, and some fresh water macro algae that occur in seasonally or permanently wet environment. Aquatic macrophytes can be used as tool in the determination of pollution and nutrient level. Submerged macrophytes play key role in the ecology of shallow, alkaline, clear water, lakes, where they form an extensive and diverse littoral community with numerous associated invertebrates, fish and birds (Jeppesen et al., 1993) while the cover and biomass of submerged macrophytes and their role in lake metabolism are largely predictable from lake area, basic configuration and nutrient loading (Gasithe and Hoyer, 1998).
The present study was carried out in the Santhapettai fresh water lake physico-chemical parameters, to assess the wealth of the macrophytes and to find out the dominance of the macrophytes.

MATERIALS AND METHODS
Santhapettai lake (Lat.

Physico-chemical parameters
The outcomes on a few physico-chemical parameters viz., Air and water temperature, pH, salinity, electrical conductivity, total dissolved solids, total alkalinity, free carbon-dioxide, dissolved oxygen, biological oxygen demand, total hardness, calcium, magnesium, chloride, sulphate, nitrate, potassium and sodium are given in table 1.
In present study, highest value of air and water temperature (39.5; 37.6 °C), pH (9.

Biological parameters
In this present investigation, a total of 33 species belonging to 23 families and 28 genera were identified under four classes. Seven species of seven genera and seven families under the class dicotyledons, nine species of eight genera and nine families under the class monocotyledons, six species of six genera and six families under the class pteridophytes, eight species of five genera and three families under the class algae are recorded. Further the aquatic macrophytes classified in morphological group. Among five morpho-ecologic groups, submerged anchored with 13 species dominated the lake followed by emergent anchored (11), floating (7), floating leaved anchored and submerged with one species each. The most dominant families were Hydrocharitaceae and Najadaceae with three species followed by Salviniaceae, Ceratophyllaceae, Characeae, Cyperaceae and Lemmaceae with two species each. Only one species each was recorded for Aponogetonaceae, Commelinaceae, Poaceae, Pontederiaceae, Convolvulaceae, Isoetaceae, Onagraceae, Verbenaceae, Marseliaceae, Araceae, Potamogetonaceae, Polygonaceae, Traphaceae, Typhaceae, and Haloragaceae. The morpho-ecological group of aquatic macrophytes is given in table-2. The plants were photographed and given in figure 1. Aquatic macrophytes in the lake occur as submerged anchored (40%) dominated the lake followed by emergent anchored (33%), floating (21%), floating leaved anchored and submerged with 3% each (figure 2). Important value index (IVI) of the aquatic macrophytes is given in figure 3.
Presence of Eichornia, Pistia and Ipomoea indicated a clear sign of invasion of alien species in the lake. Narayana and Somashekar (2002) have been conducted that the physico-chemical characters influence the growth of species, distribution, indicator group and Pollution tolerant species. The influence of water chemistry in aquatic plant richness was analysed in several studies. Nicolas et al., (2000) formed that the vegetation response to environmental factors are not always linear. Rorslet (1991) and Murphy (2002) found that the higher macrophytes diversity was observed in mesotrophic to slightly eutrophic lakes. In the present study the monocots predominant over dicots with respects to species, genera and family. Anand and Sharma (1993) also reported that in lotic water bodies monocot dominated the dicot. Such a dominance of monocots over the dicots in aquatic habitates has already been emphasized by a number of works (Muencher, 1994 andHutchinson, 1975). Predominance of monocots in an aquatic ecosystems is due to the high degree of polyploidisation, consequently increased the seed size, tendency to reproduce vegetatively and resistance to herbivores (Kautsky, 1989). Growth of emergents becomes very dense with eutrophication (Moss, 1979) and with the increase in the alkalinity of lakes, the floating leaf species get replaced by emergent macrophyte (Makela et al., 2004). The studied lakes are shallow lakes, which provide suitable habitat for the growth of emergent vegetations (Pandit, 2010).

CONCLUSION
Inhabitants around the lake are unaware about the importance of flora and fauna. Qualitative and quantitative floristic survey, constant monitoring and protection of lentic and lotic ecosystems are the need of the hour in order to save the native biota, to maintain the quality of drinking water, and disqualify the efforts of alien species to invade.