Research Article Biology and Medicine, 3 (2) Special Issue: 336-341, 2011 336 MAASCON-1 (Oct 23-24, 2010): “Frontiers in Life Sciences: Basic and Applied” eISSN: 09748369, www.biolmedonline.com Zooplankton population in relation to physico-chemical factors of a sewage fed pond of Aligarh (UP), India *Ahmad U, Parveen S, Khan AA, Kabir HA, Mola HRA, Ganai AH Limnology Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh, India. *Corresponding Author: uzmaahmad24@yahoo.com Abstract The present study conducted during the year 2008 deals with zooplankton population and chemical characteristics of a sewage fed pond of Aligarh. Sampling was done monthly between 8 am and 11 am from January to December 2008 to work out parameters such as air and water temperature, transparency, dissolved oxygen, total dissolved solids, pH, alkalinity, hardness, calcium, magnesium, hydroxide, carbonate, bicarbonate and conductivity. Air temperature ranged from minimum 17 °C in January to maximum 37 °C in June, and water temperature ranged from 15 °C in January to 35 °C in June. Minimum transparency was recorded 15.0 cm while maximum was 19.5 cm. Dissolved oxygen ranged from 1.6 mg/l to 9.2 mg/l. The pH ranged from 8.3 to 9.1. Carbon dioxide was never recorded throughout the study period. Phosphate ranged from 0.435 mg/l to 1.02 mg/l. Nitrate ranged from 0.106 mg/l to 0.198 mg/l. Total of 20 zooplankton species were found belonging to 4 groups i.e. Cladocera (4 species), Copepoda (3 species), Rotifera (11 species) and Ostracoda (2 species). Rotifers were found to be dominating other groups of zooplankton. The water body is receiving domestic discharge leading to large amount of nutrient inputs and high amount of phosphate and nitrate in the water body indicates that water is eutrophic in nature. Continuous presence of Asplanchna, Brachionus, Keratella, Fillinia, Cyclops and Diaptomus is an indicator of organic pollution. Keywords: Sewage; zooplankton; eutrophic water bodies. Introduction Zooplanktons are microscopic organisms which do not have the power of locomotion and move at the mercy of the water movements. Rotifers, cladocerans, copepods and ostracods constitute the major groups of zooplankton. They occupy an intermediate position in the food web. Zooplankton mediate the transfer of energy from lower to higher trophic level (Waters, 1977), thus zooplankton represent an important link in aquatic food chain and contribute significantly to secondary production in fresh water ecosystem (Sharma, 1998). Zooplankton communities respond to a wide variety of disturbances including nutrient loading (Dodson, 1992), acidification and sediment input. It has immense significance in fisheries (Jhingran, 1991). Zooplanktons also play an important role as indicators of trophic condition in both cold temperate and tropical waters (Sharma, 1998). The most common and severe problem is the enrichment of water by a nutrient that increases the biological growth and renders the water bodies unfit for diverse uses. Nutrients that are present in fertilizers as well as in domestic and industrial wastewater have been identified as main cause for changing the trophic status of water bodies from oligotrophic to mesotrophic to eutrophic. Although zooplankton exists under a wide range of environmental condition, yet many species are limited by dissolved oxygen, pH, salinity and other physico-chemical factors. George (1962) and Hutchinson (1967) have reported several other factors like dissolved oxygen, pH, alkalinity, and temperature light and grazing affecting zooplankton population. Therefore, this work aimed to study the zooplankton population in relation to physico-chemical factors of sewage fed pond in Aligarh. Materials and Methods Present study was carried out on a fresh water body of Aligarh. The pond is a sewage fed used as drainage basins into which the surface runoff water and sewage from the surrounding catchments area enter. Different physico- chemical parameters were analyzed monthly from January 2008 to December 2008. Samples were collected from 8 am to 11 am. Air and water temperature were recorded by mercury thermometer graduated upon 100°C. pH of water was determined at the sites by using a portable electronic digital pH meter. Dissolved oxygen analysis was performed at the sites by Winkler’s modified technique according to APHA (1998). For zooplankton analysis, samples were collected from each water body on a monthly basis. About 100 liters of water is filtered by passing water through plankton net made up of bolting silk cloth having mesh size of 25 micrometer. Samples were then washed into wide mouth bottles and were preserved by adding 5% formaldehyde solution. Further analysis was done by putting 1 ml of the preserved sample on a Sedgwick-Rafter cell