Ecology of phytoplankton from Dharamtar creek, west coast of India

Phytoplankton pigment, cell count and species diversity were studied at five locations in Dharamtar creek during September 1984 to November 1985. Chemical parameters indicated a healthy system free of any environmental stress. The water was vertically mixed except during the monsoon period and nutrients never became a limiting factor for phytoplankton production. Concentration of chlorophyll a and phaeophytin were fairly high, (av. 1.94 and 1.89 mg m(-3) respectively). A total of 58 genera of phytoplankton comprising 46 diatoms, 6 dinoflagellates and 6 other algae were recorded from the area. Thalassiosira dominated the phytoplankton community. In the interior part of the creek blooms of Skeletonema and Peridinium were respectively observed during October-November and December. Correlation between chlorophyll a and cell count was significant while there was no correlation between phytoplankton and different physico-chemical parameters. Margalefs diversity index D varied from 1.14 to 4.93 with higher diversity towards the outer than the interior zone. In general the creek sustained a rich and diverse phytoplankton community.