The phytoplankton diversity, distribution, density and their relationships to physicochemical variables were investigated using multivariate analyses. Day and night samples were collected monthly between November 2011 and April 2012 from two different stations, Chatham and Junglighat in South Andaman Island. A total of 204 species and 65 genera were identified at these two stations. Diatoms (135 species), dinoflagellates (63 species), cyanobacteria (4 species) and silicoflagellates (2 species) were the most important taxonomic groups represented. Bacteriastrum furcatum, Guinardia flaccida, Leptocylindrus danicus, Rhizosolenia alata, Rhizosolenia imbricata, and Meuniera membranacea were the major diatoms abundant in the coastal waters. The relationships between the phytoplankton and the environmental factors were studied by canonical correspondence analysis with special attention to the sampling time (day and night). The distribution patterns of the phytoplankton communities during day and night were analyzed indirectly by detrended correspondence analysis. Seasonal and spatial variations in the phytoplankton density were largely resulted from light and temperature. The long-term trends in phytoplankton community dynamics would provide information about the change in trophic status of the system, as well as a foundation for distribution studies of these species in marine ecosystems.

Phytoplankton community, diatoms, dinoflagellates, environmental variables, multivariate analysis, South Andaman