Environmental stress studies with reference to the pollution in the Vattakayal backwaters near the industrial area of Chavara Kollam district Kerala

Abstract

The study aimed to evaluate the pollution and subsequent environmental stress in the Vattakayal backwaters, near the industrial area of Chavara, Kollam, Kerala. Analysis of the various physico-chemical parameters of water (temperature, pH, electrical conductivity, turbidity, total dissolved solids, total alkalinity, total hardness, chloride, salinity, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, sulphate, nitrate, phosphate, and heavy metals - zinc, copper, cadmium, lead, chromium and iron) and sediment samples (pH, electrical conductivity, organic carbon and heavy metals - zinc, copper, cadmium, lead, chromium and iron) were carried out for a period of two years (2008-2010) during premonsoon, monsoon and postmonsoon seasons. To study the stress effect, the experimental fish (Oreochromis mossambicus) was exposed to wastewater from the industry for different concentrations and durations to evaluate the haematological and histological changes induced. Seven metal resistant bacterial strains were isolated from the sediments of the Vattakayal estuary and minimal inhibitory concentrations (MIC) and antibiotic sensitivity were studied. Bioaccumulation potentials of two bacterial strains [Bacillus cereus (JQ863364) and Bacillus licheniformis (JQ863365)] against the heavy metals (chromium and lead) were also studied. The principal component analysis (PCA) showed similar trend for both water and sediment parameters studied, indicating the common source of contaminants. Haematological and histological (gill, liver and intestine) studies revealed remarkable changes in the experimental fish compared to the control. Metal resistance study showed that out of the seven bacterial isolates, 57.14% exhibited high tolerance against lead, zinc and copper. The bioaccumulation studies revealed that the above two bacterial strains, identified based on 16S rDNA sequencing and phylogenetic analysis, are found to be efficient agents for the removal of Cr (VI) and Pb (II) in aqueous solution