I conducted limnologcal investigation of the river Nunia, receiving a fair share of agricultural runoff, industrial wastes and municipal sewage of Asansol industrial area of West Bengal. This important tributary of Damodar River is considered lifeline of this area. People use it largely for irrigation, fishing and many other domestic purposes.
In my research work, I have mastered both the fundamental and technical aspects necessary for a complete limnological investigation of waterbodies. In my research work, I carried out field sampling, data analysis and presented my findings. My study yielded following findings in brief:
Water quality:
My study revealed that Nunia was severely polluted with high values of dissolved and suspended pollutants including nutrients, pesticides, heavy metals and coliform bacteria. The values of some of the water quality parameters including dissolved and suspended solids, turbidity, alkalinity, nitrate, ammonia, phosphate, sulfate, chloride, BOD, COD and hardness were high compared to the permissible limits set by WHO. Dissolved oxygen, on the other hand, was observed much below the required level recommended for sustaining fish life. Very high values (>100) of water quality index (WQI) and occurrences of several water-borne diseases like infantile diarrhea, jaundice, dysentery and gastro-intestinal disorders among the human users indicated that the water of Nunia was not fit for human consumption.
Aquatic fauna and flora:
Some pollution tolerant zooplanktonic organisms such as Ceriodaphnia, Brachionus, Keratella, Adona, Cyclops, Chydorus, and macroinvertebrates such as Chironomid larvae, Tubifex and Lymnaea were abundantly present. But the polluted aquatic environment caused maximum damage to some molluscs and commercially important fishes. Molluscs such as Viviparus, Lamellidens, Melanoides and Gyraulus declined sharply. High mortality of Catla catla, Labeo rohita, L. bata, Mystus aor, Wallago attu and some small fishes was observed during summer months. High mortality of fish populations might be due to the damaging effects of pollutants as indicated by the histopathological study on gills of the affected fishes. The damage was marked by curling of secondary gill lamellae, rupture of gill rackers and nacrosis. Formation of a film of coagulated mucus on the surface of the gills was also recorded in some cases. Spectrophotometric study revealed considerable bioaccumulation of Zn, Cu, Hg and Pb by the organisms of both herbivore and carnivore levels of aquatic food chains.
High values of nutrients in the water led to the massive growth of water hyacinth in the zones of intense pollution. It was also observed that water hyacinth played important role in abating pollution by removing nutrients such as sulfate, nitrate, ammonia and phosphate from its water. The removal of these nutrients was estimated to be 43.03%, 5.33%, 25.5%, 23.03% respectively.
My work pioneered a series of research projects in the area. I published my scientific works in reputed journals, books and leading Indian newspapers and presented my papers in national level seminars held in different parts of India. My research findings have created a far-reaching environmental awareness in the geographical area. Asansol Municipal Corporation, for example, now has taken urgent measures to curb pollution of this river (Nunia), which is considered as an important lifeline for the entire industrial zone.