989-999Phytoplankton community structure along the coastal waters of the Northeastern Arabian Sea (NEAS) was analysed for three years (2009, 2011 and 2012) during the winter monsoon season. The coastal waters of NEAS, especially Saurashtra coast are a region of high fishery potential. A total of 137 species of phytoplankton were identified. The community structure of phytoplankton showed significant inter-annual variability. The study highlights the persistence of certain non-indigenous phytoplankton species such as Scrippsiella trochoidea, Karenia mikimotoi and potentially harmful dinoflagellates mainly Gonyaulax polygramma, Dinophysis acuminata, D. miles and Tripos furca in the region that can raise probable threats towards the indigenous species and can cause harmful or toxic events. The increased abundance of diatom, Pseudo-nitzschia spp. that can produce toxins at certain threshold levels was also observed. The possible reason for the increased abundance of such groups can be suggestively due to the increased anthropogenic inputs into the coastal waters and intense fishing and maritime activity in the area
