STATUS OF WATER QUALITY IN SELECTED SHRIMP FARMING CREEKS IN NAGAPATTINAM DISTRICT, TAMILNADU, INDIA

The present study was carried out to determine the physico-chemical characteristics and microbiological aspects of ten selected creeks in Nagapattinam District during January 2018 to December 2018. Most of the creeks fall in the range of 7 to 7.5 pH range while Sempodai, followed by Vettaikaranirupu, Vellapallam and Kallimedu showed pH above 8. Salinity of most of the creeks were recorded in the range of 20 to 35 while some creeks viz., Sempodai followed by Kallimedu and Thopputhurai showed above 50 ppt just before monsoon rains. The maximum salinity has been recorded as 61 ppt at Sempodai creek. Alkalinity values were fall in the range of 50 to 150mg/l as CaCo3 for most of the creeks except Vellapallam creek wherein wider variations in alkalinity 112 to 270 ppm was recorded. The maximum value of hardness (12000ppm) was measured at Sembodai creek followed by Kallimedu. After monsoonal rain a sharp decrease in hardness was observed in almost all the creeks. Highest ammonia concentration was recorded (2ppm) at Nagoor Vettar creek followed by Sempodai while rest of the creeks were fallen in the range of 0 to 0.5 ppm. The nitrite value was found to be higher at Karuvelankadai creek. Maximum phosphate concentration was observed at Karuvelankadai, Periyathumbur and Kallimedu creeks.  TPC showed an increasing trend from the start of the year towards the end in most of the creeks except in Veilankanni, Vettaikariniruppu, Vellapallam and Thopputhurai where a mixed trend in TPC was observed. The presumptive pathogenic Vibrios were maximum at Vellapallam creek (1800 cfu/ml) followed by kallimedu, Karuvalenkadai and Veilankanni.  A few creeks showed differences with the regular pattern due to the variables like flow of water, pollution from the nearby farms etc. The seasonal variations were found in the water quality parameters among the creeks with respect to the standard water quality parameters.