Studies on riverine ecology of torrential waters in the uplands of the Garhwal region II. Seasonal fluctuations in diatom density
Seasonal fluctuations along with certain physico-chemical parameters were recorded for two hillstreams, the Alaknanda (snow-fed) and the Nayar (spring-fed). In the former, the water temperature range of 9–14°C is considered optimum for the growth of diatoms, compared to 12–21°C in the Nayar. In both hillstreams diatoms achieved their maxima during January, when the water temperature is the lowest. Sudden influx of rain water carrying enormous silt during monsoon is responsible for the decline in density. The water temperature and current, especially the latter is thus a detrimental factor. The interesting feature of the study is, the relatively higher percentage of diatoms in the Nayar than in the Alaknanda, obviously to be attributed to the warm waters in the former.