Gomphonema incrassata sp. n., a new benthic diatom species (Bacillariophyceae: Gomphonemataceae) from Walayar Dam, Palakkad district, Kerala, India

A new freshwater benthic diatom species, Gomphonema incrassata sp. n. (Mohan and Prabha), is described from the Walayar Dam, Palakkad district, Kerala, India. The description is based on data derived from light and scanning electron microscopic studies. The main features of Gomphonema incrassata are: valves are weakly heteropolar; linear-lanceolate; head pole is bluntly round; basal or foot pole is sharply rounded; and the frustule is club-shaped and flexed (bent) in the girdle view. In addition, the analysed physicochemical characteristics revealed that Walayar Dam is moderately polluted, due to various human activities. The newly identified freshwater diatom species adds to the knowledge of diatom diversity in the Indian subcontinent.