Biotechnology to aid environmental monitoring

THE RAJIV Gandhi Centre for Biotechnology at Thiruvananthapuram is successfully using environmental biotechnology for systematic environmental and ecological monitoring of aquatic environment in Kerala.

The results of studies conducted over 12 months in Kuttanad, the rice bowl of Kerala, have confirmed serious deterioration of the ecosystem. There were high concentrations of heavy metals and organochlorine pesticide residues in water and sediment. High levels of bioaccumulation of these chemicals were taking place in humans and animals living in the area.

The studies also showed the presence of virulent strains of poliovirus I and other viruses like hepatitis viruses in water. It is hoped that the studies would soon throw up biotechnological innovations for abatement of environmental risks.

Kuttanad is a 278 square km area spread across two districts in Kerala interspersed with backwaters and reclaimed paddy fields. The paddy fields actually lie below the water level protected by dikes. The environmental degradation of the Kuttanad started with construction a barrage across the backwaters separating the upper areas of the backwaters from the lower areas and the estuary and replacement of the dikes, made of mud, with concrete structures.

This was done to facilitate cultivation of an additional crop by preventing floods and salt water intrusion. The construction of the barrage upset the water balance of the region. During monsoons, the paddy fields used to be flooded by the discharge of four rivers into the backwaters. The sediments brought by the rivers kept the land fertile and the salt water intrusion in summer cleansed the waters. With the construction of the barrage and additional cropping of the land, all this changed and Kuttanad became a cesspool of human waste and fertilizer and pesticide residues.

Researchers from the Centre, led by Dr. M. R. Das, have collected water and sediment samples from 15 selected stations in Kuttanad at regular monthly intervals and analysed various quality parameters. The data covering three seasons indicated deterioration of the ecosystem and consequent depletion of faunistic compartments.

The distribution of heavy metals and pesticides in water, sediment and different trophic levels in the food chain were analysed. The analysis showed that the heavy metals in water and sediment exceeded acceptable levels, indicating a serious heavy metal pollution in the region. Organochlorine pesticide residues were also found in considerable amounts. It was observed that water and sediment in the Kuttanad system acted as sources for bioaccumulation in the faunal compartments. High concentrations of residues were found in plankton, benthos, earthworm, clam, fish, prawn, frog, cow's milk and human blood from the area.

Data on the average concentration of heavy metals in water showed that the concentrations of cadmium, iron, manganese, nickel, lead and zinc were highest in the pre-monsoon period whereas those of chromium and copper were maximum in the monsoon period. Post monsoon values were generally low for all the metals studied except iron. All heavy metals except nickel and chromium exceeded the respective permissible levels in the pre monsoon and post monsoon periods. Iron and manganese were the dominant metals.

In the sediments, all heavy metals except iron had maximum concentration in the post monsoon period. Concentration of iron was high in the pre-monsoon period. Manganese, zinc and lead were the most dominant metals in the sediment.

The seasonal variations in the concentration of heavy metals, according to the study, was related to their flushing into the sea during the monsoon season when there is sufficient flow. After the monsoonal flow is reduced, metal concentration increase from various sources. Owing to drinking water scarcity in the area during the period, many people use the lake or well water for domestic purposes. The study has also reported presence of metals, especially nonessential metals like cadmium and lead, in edible organisms and cow milk raising serious concern. These indicated that the local people are facing considerable risk of heavy metal poisioning.

The Centre has also assessed the cumulative effects of various anthropogenic pressure upon the planktonic and benthic biocoenoisis. High concentrations of detergent in the water was found to have adversely affected the growth of phytoplankton.

It selected four sampling sites, one each in the kari land and lower Kuttanad and two in the Kayal lands, for studying the bacterial and virological status of Kuttanad lake system.

The analysis showed that enteroviruses were positive in Kari land during the February, April, November and January. It also indicated clearly the presence of virulent strains of poliovirus I in the environment. Enteroviruses were detected but no hepatitis E virus was detected.

Analysis of bacteriological quality of water showed predominantly the presence of vibrio species, Klebsiella species, pathogenic and toxigenic E. coli and Pseudomonas species. The value of coliforms were more than 1500 in most of the sampling sites, except in one site in the Kayal land. (In safe drinking water, this should be near zero).

The season and location of detection of viruses and heavy metals have certain significance. For example, the finding of viruses in the Kari lands (the discharge point of Pamba) suggests that it is linked to the Sabarimala pilgrimage. Similarly, high concentration of copper in the kayal land (discharge point of Manimalayar) suggests that its source is the rubber plantations upstream. (Copper sulphate is sprayed in rubber planations prior to the monsoon, and the plantations are concentrated in the catchment area of Manimalayar.)

The scientists who worked on the project included Mr. Paul Murugan, Mr. Sanil George, Mr. K. Harikrishnan, Mr. Sabu Thomas and Mr. G. S. Naveen Kumar.

Roy Mathew

Thiruvananthapuram

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