OCCURRENCE OF DIAPHANOSOMA-EXCISUM (SARS) ON A SANDY BEACH AT BALRAMGARI (ORISSA), INDIA

The occurrence of Diaphanosoma excisum (Sars), a freshwater cladoceran , in benthic samples of an intertidal sandy beach is reported. Populat ion density was seasonal. A relatively high density was recorded from June to September (south-west monsoon season) with a maximum (46 ind 1 0 cm(-2)) in September at a depth of 10-15 cm of sediment. A sudden de cline occurred during north-east monsoon (October to January), and in the fair season (February to May), the cladocerans disappeared. Mean d ensity varied (P<0.001) with sediment depth and season and showed a co ntagious dispersion. Abundance was negatively correlated with salinity (r = -0.76) but positively with POC (r = 0.79) and mean grain size of the sediment (r = 0.93). The density of D. excisum was highest in fin e sand.