The Diatom Asterionella in the Krishna Estuary Region

Abstract

DURING the course of an extensive hydrobiological survey of the Krishna River estuary, standing at the mouth of the northernmost branch of the Krishna River, we noticed that the shore waters and the sea, as far as the eye could see, were coloured deep chocolate brown, and that the intertidal sand was covered with a thick green scum. A sample of the water, taken one mile south of the river mouth, was collected in a bottle of known volume (2½ 1.), fixed with formaldehyde and allowed to settle for a day, giving a sediment 30 ml. in volume. On analysis of the sediment by a conventional method (using a Sidgwick–Rafter cell), we found that it contained mainly swarms of diatoms, the majority of which belong to the chain-forming genus Asterionella (Japonica?). Other forms like Biddulphia, Thallassiothrix, Pleurosigma, Fragillaria, and Chaetoceros were also found, but in fewer numbers. The catch represents a total population of 55.568 millions per litre (approximately 55.6 cells/mm.³). Of this Asterionella alone accounted for 51.6 cells/mm.³.