Comparative analysis has been made on the water quality parameters in three seagrass sites, Sangumal and Farm pond in Palk Bay; Thonithurai and one non seagrass site - Kundhukaal point in the Gulf of Mannar from January 2006 to December 2007. The atmospheric temperature ranged from 24.8° to 35.3 °C, sea surface temperature from 25° to 35°C, pH from 7.44 to 8.44, dissolved oxygen from 1.0 ml to 5.9 ml l-1 and total suspended solids from 10.7 mg to 122 mg l-1 in the four sites. The maximum concentration of phosphate, silicate, nitrite and nitrate in the water were 1.22 μmol, 5.83 μmol, 0.63 μmol and 2.03 μmol l-1 respectively. Sangumal had the maximum input of nutrients especially during the northeast monsoon. Pearsons correlation coefficient showed significantpositive correlation (ρ<0.01) of sea surface temperature with pH, salinity, dissolved oxygen and negative correlation with total suspended solids,nitrite and ammonia. Though ANOVA did not show significant difference in water quality parameter between sites with and without seagrass, highly significant difference (ρ<0.001) was observed seasonally in sea surface temperature, salinity, nitrite, ammonia, wind velocity, rainfall and number of rainy days,thereby influencing the growth of seagrass beds.

Seagrass, nutrients, sea surface temperature, chlorophyll, rainfall, Palk Bay, Gulf of Mannar