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Abstract
The river ecosystems from the headwaters to the foothills in the upper mountain reach of the Ganga (Bhagirathi River) were characterized by increasing temperature, pH, total alkalinity, nutrient and BOD and decreasing current velocity, turbidity and DO. The biotic communities included benthos (phytobenthos, zoobenthos) and nekton (fish). The headwaters at Gangotri were heterotrophic and lacked fish (both grazers and predators). Functionally, the detritus and grazing chains operate in headwaters of the upper Ganga. The food chain was short and the web simple. In the middle and lower stretches, the macroinvertebrate assemblages functioned as filtering collectors and scrapers, representing detritus and grazing food chains. The abundance of scrapers indicated transition from heterotrophic to autotrophic state. The food chains and the food web became complex from the middle to lower stretches.
Acknowledgements
The financial support from the G B Pant Institute of Himalayan Environment and Development, Kosi–Katarmal, Almora, Ministry of Environment and Forest, New Delhi and academic support from Prof. J. P. Bhatt, Head, Department of Zoology, H N B Garhwal University are all gratefully acknowledged. I thank Dr. Asheesh Shivam and Mr. K. R. Singh for assisting me in preparing this MS. I also thank the anonymous reviewers who have encouraged me to improve the content of this MS through their comments and suggestions.
