LAUSR

Our examination of net phytoplankton collected from coastal localities in Odisha on the east coast of India, including Chilka Lake, Chandrabhaga Beach and Puri, in December 2015, revealed the overwhelming dominance of Thalassiosira mala, a gelatinous colony-forming, potentially harmful, marine planktonic diatom. The large numbers of cells allowed us to observe details of the cingulum not previously reported. The epicingulum is composed of four open bands including an areolated valvocopula, an areolated copula and two non-areolated pleurae. The immature hypocingulum includes at least two bands. Openings of alternate bands are arranged in a dextral pattern. Based on previous reports from the west coast and our current findings, Thalassiosira mala appears to be a common, widely distributed primary producer in Indian coastal waters. The presence of morphologically similar species, especially those <20 μm in diameter, underscores the importance of reliable species-level taxonomy using appropriate techniques for meaningful ecological and biogeographic considerations and for monitoring potentially harmful algae in India’s economically important coastal waters. Published reports suggest that Thalassiosira mala is widely distributed in temperate and tropical waters, present in 26 of 232 ecoregions and 18 of 62 provinces recognized in a recent classification of coastal marine ecoregions.