Distribution of phytoplankton in a river-lake system with strong seasonal discharge variations in Central India
Sankaran Unni, K.; Varghese, M.
Phytoplankton development in the Narmada, Central India was followed at 10 stations. Along its downstream course at a distance of 212 km it passes through a deep pool between stations 4 and 5 (4 km long and 0.5 km wide and 6 m deep during low water period). Between stations 8 and 9 at a distance of 326 km from the source it passes through another deep gorge turned reservoir. This permits large fluctuations in aggregate phytoplankton and in the present studies these reservoirs were found to act as mixed reactors supplying inoculum downstream. Aulacoseira granulata dominated during the post-flood through its capacity for meroplankty. The inoculum supplied by the Bergi dam combained with continuous mixing of the waters through the impact of waterfall resulted in peak growth of Aulacoseira in October and November before the winter. Factors which further contributed to the dominance of Aulacoseira during the postflood period were the effluents which supplied nutrients, greater water temperature between 20 to 25 °C, and clarity of water. Aulacoseira being a benthic diatom developed to maxima and declined during the winter and summer. The river transformed reservoir at Bheraghat (Stations 8 and 9) acts a mixed reactor for the peak development of phytoplankton in particular Aulacoseira granulata.