Impact of domestic sewage pollution on rotifer abundance in Adyar estuary

The zooplankton and physico-chemical parameters of Adyar estuary were studied from (July-2010 to June 2011) in order to evaluate seasonal trend in rotifer diversity and abundance in relation to water quality and impact of sand bar at mouth of Adyar estuary, Chennai. The minimum and maximum values of atmospheric and surface water temperature (°C), pH, salinity (‰) and dissolved oxygen (mg/l) were: 27.33–30.00; 28.66–31.33; 7.067.86; 15.66–25.66 and 1.81–5.76 respectively. The range of nitrite (mg/l), ammonia (mg/l) and phosphate (mg/l) were: 0.12- 0.22: 1.80- 6.66 and 0.57- 5.33 respectively. A total of 8 rotifer species were recorded from four seasons of which Brachionus plicatilis formed the predominant species. Maximum density of rotifers was recorded during pre monsoon (6426.21±3707.26 Ind./L) and summer seasons (4042.32±3379.43 Ind./L) while minimum was recorded during monsoon (24.66±24.24 Ind./L) and post monsoon months (203.50±106.65 Ind./L).