An accidental encounter with bloom of diatom Palmerina hardmaniana (Greville) Hasle in Sundarbans, India: Impact on zooplankton community structure in tidal creek environment.

The present study reports on a transient diatom bloom of Palmerina hardmaniana (Greville) Hasle 1996 encountered accidentally in May 2018 in the world's largest mangrove forest of Sundarbans, India. This bloom was the sixth record of diatom blooms from Indian coastal waters and the fourth from Sundarbans waters. The diatom cell count ranged from 2.571 × 10 to 6.857 × 10 cells L during the bloom. The zooplankton taxa count decreased from 39 during the pre-bloom to 30 during bloom and 31 during the post-bloom phase. However, no significant (p < 0.05) change in zooplankton species richness was observed between the three different phases. The consistent occurrence of copepod Bestiolina simlis across sampling points indicated a high tolerance to environmental parameters. The zooplankton population also did not respond vehemently to bloom-forming P. hardmaniana in this creek environment. These observations warrant further studies to examine the effect of blooms on the overall marine ecological food chain of creek ecosystems.