STUDIES ON USE OF BACTERIAL POPULATIONS AS A BIOLOGICAL INDICATOR IN AQUATIC ECOSYSTEMS WITH SPECIAL REFERENCE TO BOLGODA NORTH LAKE

Abstract

Investigated densities of bacterial populations in relation to the environmentalprameters in Bolgoda North Lake for a period of six months from January to June2000.

Surface water samples were collected from six sampling stations in the lake atmonthly intervals. Densities of bacterial population (total viable colony count),total coliforms and faecal coliforms were enumerated as biological indicators inall the samples collected. Temperature, pH, electrical conductivity, salinity, sechidisk depth, dissolved oxygen (DO), biochemical oxygen demand (BOD),chemical oxygen demand (COD), Orthophosphate and nitrate contents weremeasured as environmental (physical-chemical) parameters. Examinedcorrelation among biological indicators and some selected water qualityparameters.

High densities of bacterial populations were found in water samples collectedfrom sampling stations at the extreme upper part of the North Lake near out-letsof drains which bring domestic, urban and industrial (textile) effluents. Lowdensities of bacterial populations were reported from sampling stations at thelower part of the North Lake.

Results revealed that some chemical parameters have an influence on the densityof bacterial population. The density of bacterial population showed a significantpositive correlation with biochemical oxygen demand and phosphateconcentration, while a significant negative correlation with dissolved oxygencontent of the surface water of the lake. However, the density of bacterialpopulation did not show a significant correlation with nitrate content.

The density of bacterial population is an useful biolocial indicator for monitoringof organic pollution in inland surface waters since high DO, BOD values and highP04,3 content indicate organic and nutrient pollution parameters of surface waterquality.