PHYSICO-CHEMICAL STATUS OF POLACHIRA WETLAND ECOSYSTEM IN SOUTHERN KERALA

Polachira wetland in Southern Kerala is a famousdestination of itinerant birds.Thebird aggregation in wetlands is always correlated to the abiotic and biotic factors of the ecosystem. The present investigation reveals the hydrology of the Polachirawetland during February to July 2014. The air and water temperature agreed with the climatic factors prevailed. The pH showed slight acidity and alkalinity. The total solids fluctuation was renderedby the Total Suspended Solid and Total Dissolved Solid which was indicated by organic discharge, high chloride content and salinity in water. Salinity in water was elevated due to the incursion of saline water from Paravur estuary to Polachira wetland through a canal. The free carbondioxide concentration did not show much variation but dissolved oxygen showed variation. The total hardness which was related to the calcium and magnesium hardness in water was determined.Alkalinity was balance in the ecosystem. Nutrients such as nitrite, nitrate, phosphate and silicate were in equilibrium concentration.Correlations of physicochemical parameters among six months were statistically significant.


INTRODUCTION
Wetlands are unique landscape which abode a great biodiversity. These ecotonesare saturated with countless forms of species of great ecological importance. This sensitive system preserves both aquatic and terrestrial ecosystems.In wetland the species richness is always enveloped around the hydrological regime of the environment. Nowadays anthropogenic input is elevating beyond a certain threshold level which has a profound impact on the water quality of the aquatic environment.India sustains assorted types of wetlands strewn across various eco-geographical regimes that comprises of wetlands in high altitude Himalayas to Deccan plateau.Kerala is bestowed with the most productive wetlands. Wetlands in Kerala are facing dwindling of ecological and economical valuesdue to high populace.The present investigation has been taken up the variations in the hydrology of Polachira wetland in Southern Kerala.

MATERIALS AND METHODS
The present study was carried out on the physico-chemical parameters of Polachira Wetland (8°50′26.89″N and 76°42′0.3″E) located in the Southern part of Kollam district in Kerala.The sprawling wetland spread over 600 hectares is on theem bankment of estuaries of the Ithikkara River and Paravur backwaters.It is an oval shape wetland at a depth of 1m below ground level and is encircled by small creeks and is densely vegetated. The samples were collected from five stations in the second week of every month during a period from February 2014 to July 2014. Physical parameters like Temperature and pH, were performed on the field. The physicochemical parameters like Total Solids (TS), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Dissolved O2, Free carbon dioxide, Total alkalinity, Total hardness, Calcium hardness, Magnesium hardness, Chloride, Salinity, Phosphate, Sulphate, Nitrite and Nitrate were analyzed as per the methods of APHA (1998) and Trivedy and Goel (1986). Data collected were subjected to proper statistical analysis. One-way analysis of variance (ANOVA) and Pearsoncorrelation coefficient was calculated to test the degree of relationship of water quality parameters between six months.

RESULTS AND DISCUSSION
The monthly variation (average value of different stations) of physicochemical parameters is given in Table 1. The temperature of both air and water is a remarkable regulatory factor governing the biogeochemical reactions of aquatic ecosystem. Monthly variation of atmospheric temperature in Polachira wetland ecosystem ranged between 30.1˚C and 36.6˚C during the month of June and March respectively.The present investigation revealed well marked variations in the atmospheric temperature. This may be due to the climatic conditions. Water temperature ranged from 29.6˚C (July) to 33.4˚C (March). The maximum and minimum temperatures may be due to the hot and cold climatic conditions.  pH showed a minimum and maximum value of 5.88 and 8.28 during the month of April and May. It is found that a slight acidic as well as basic in water may be induced by the improper use of fertilizers from agriculture field and garbage disposal.
The Total solids (TS) are a measure of both, the dissolved as well as suspended solids in watercomprising dissolved salts, suspended particles, soil particles, discharged effluents and decomposed organic matter (Patil et al., 2011). In the present study the total solid varied between 560 mg/L (July) and 2160 mg/L (April). The total suspended solid was measured between 220 mg/L (July) and 500 mg/L (April). The total solid and total suspended solid may be resulted from the run-off water, which carries dissolved solids and also organic wastes from garbage dumping, agricultural land, waste water discharges and algal growth. A similar observation was reported by Chennakrishnan et al. (2008). A minimum total dissolved solid of 340 mg/L was observed in July and a maximum of 1680 mg/L was during the month of April.Presence of high TDS may be due to the high chloride and salinity contributed by the intrusion of saline water from Paravur estuary to Polachira wetland through a canal.
Oxygen content is a major parameter needed by aquatic life forms. The dissolved O2 measured a lowest concentration of 3.4 mg/L in the month of March and the highest concentration of 6.3 mg/L observed during the month of June.Low oxygen concentrations are generally associated with heavy contamination of organic matter. In such conditions oxygen, sometimes, totally disappears from the water (Trivedy and Goel, 1986). Monthly variation of free CO2 concentration ranged between 14.12 mg/L (July) and 17.03 mg/L (April).The wetland received more organic matter through surface run off and drainage and its decomposition might have resulted in the liberation of more amounts of CO2 in the water column. The free CO2 concentration change may be due to the micro bacterial activities, increase in temperature and biochemical reactions.
Alkalinity is a measure of acid present in water and of the cations balanced against them (Yogesh Shastri and Pendse, 2001). The presence of total alkalinity during the investigation period showed a fluctuation between 71 mg/L in May and 101 mg/L during the month of February and June respectively. The increase in total alkalinity was found to be associated with the rainfall and the subsequent surface run off and leaching. The level of hardness was estimated between 160 mg/L CaCO3 and 380 mg/L CaCO3 during the month of July and March. High values of hardness are probably due to regular addition of large quantities of sewage and detergent into wetland from the nearby residential localities. Trivedi and Goel (1986) and Singh and Mahajen (1987) are of the view that the high hardness is suggestive of pollution due to domestic waste and industrial effluents.The calcium hardness value was recorded between a minimum of 41.022 mg/L CaCO3 (February) and a maximum of 96.162 mg/L CaCO3 (March). The amount of calcium increase may be due to rapid oxidation/decomposition of organic matter.
Monthly variation of magnesium hardness recorded between 10.712 mg/L CaCO3 (July) and 50.692 mg/L CaCO3 (February). Magnesium also occurs in all kinds of natural waters with calcium, but its concentration remains generally lower than the calcium (Trivedy and Goel, 1986).
Chloride is one of the factor governing the biota of aquatic system. The chloride content recorded lowest value of 202.74 mg/L (March) and maximum rate of 1177.8 mg/L (April). High and low chloride concentration was coincided with the salinity. The salinity ratewas measured between 0.3870 ppt (March) and 2.1038 ppt (April). Higher salinity content was due to the connection of Polachira wetland with Paravurestuary through a canal.
The nitrite content showed a variation between 0.0057 ppm and 0.0836 ppm. Presence of even a small quantity of nitrite will indicate the organic pollution and the availability of partially oxidized nitrogenous matter (Trivedy and Goel, 1986). The average nitrate concentration was measured between 0.0465 ppm (March) and 0.7863 ppm (May). The low rate of nitrite and nitrate concentration may be due to the utilization by the phytoplankton which was abundant during March. The increase in nitrate concentration may be due to the decaying of organic materials, discharge of sewage, natural runoff and agricultural wastes.
Phosphate is the nutrient considered to be the critical limiting nutrient causing eutrophication offresh water systems (Rabalais, 2002). The variation of phosphate concentration was between 0.0174 ppm (May) and 0.0296 ppm (July). The presence of phosphate in the wetland may be due to surface runoff during rainy season receiving huge quantity of domestic sewage, cattle dung and detergents from the surrounding catchment area. Monthly variation of silicate concentration showed a minimum of 12.168 ppm (April) and maximum of 16.013 ppm (February). High silicate content may be due to the soil erosion from catchment area.Analysis of variance of physico-chemical parameters during February to July 2014 showed that there is no significant difference in the mean value among months (Table 2). All correlations among six months were statistically significant (Table 3).

CONCLUSION
The monthly variations in physicochemical characteristics of Polachira wetland are providing a vivid knowledgeregarding the ecological status of wetland. This wetland is a preferred safe haven for resident and migratory birds. A frequent and continuous evaluation of this ecosystem is necessary to avoid dwindling of the resources.