Diversity of desmids in the Thattekkad Bird Sanctuary, Kerala, India: a comprehensive exploration

The present study tries to account for the diversity of desmids and also determine their distribution and abundance in Thattekkad Bird Sanctuary, situated in Ernakulam District, the first Bird Sanctuary in Kerala and lies within the geographical limits of 10°08′N 76°41′E and 10°13′N 76°68′E. The water samples collected were preserved and the physico-chemical parameters were analyzed using standard protocols. The study was carried out over a period of one year, from March 2022 to April 2023 in three seasons (pre-monsoon, monsoon, and post-monsoon) from the freshwater resources within the sanctuary like rivers, streams, and ponds. The following physico-chemical parameters of water were analyzed: the concentration of nitrates and phosphates, pH, temperature, dissolved oxygen (DO), biological oxygen demand (BOD), and turbidity. Desmids are unicellular algae that belong to conjugating green algae and occur exclusively in freshwaters, each cell consists of two almost symmetrical and often profusely sculptured segments. The current study identified a total of seventy-four taxa, which are distributed under four families and 18 genera. Predominant genera included were Cosmarium (21), Euastrum (12), and Staurastrum (8). Notably Heimansia pusilla, Euastrum praemorsum, Euastrum jenneri, Staurastrum saltans var. javanicum, Cosmarium clepsydra var. bicardia are new reports to India, five species are new reports to Kerala and all species being novel to Thattekkad Bird Sanctuary. The Shannon’s diversity index is in the range of 0.8070 to 1.0151, and Simpson’s Index range between 0.5051 to 0.6177.