Summary of Abstract Submission

Abstract Submission No. IO50-10-0037PresentationPoster


S. K. Baliarsingh*1, Aneesh A. Lotliker1, Mark Wells2, Chandanlal Parida3, K. C. Sahu3, T. Sinivasa Kumar1

1 Indian National Centre for Ocean Information Services, India
2 School of Marine Sciences, University of Maine, USA
3 Department of Marine Sciences, Berhampur University, India


Surface waters of a coastal site along north western Bay of Bengal was observed with sporadic bloom of Noctiluca scintillans (NS) resulting brown to dull-red discoloration of surface water during April, 2014. The highest cell density of 32.87 x 104 cells-l-1 was observed during peak blooming phase. A low species diversity and low abundance of other phytoplankton were observed during the present investigation. Nutrient depletion in these waters may have preconditioned the water column for proliferation of NS. Increased concentrations of ammonia during the latter phase of the NS bloom were indicative of active grazing and nutrient regeneration. Two toxigenic dinoflagellate species, Gonyaulux spp. and Alexandrium spp., were present during the bloom period, although their numbers were low. Dissolved oxygen concentrations in sub-surface waters decreased to near hypoxia, and anecdotal information from local fishermen suggest fish were avoiding the area. The contribution of microplankton to total chl-a increased in conjunction with the decreases in pico and nanoplankton biomass as the NS bloom declined. Mesodinium rubrum, observed to be swarming at the end of NS bloom, may have fed upon nanoplankton, suggesting that M. rubrum outcompeted NS for the nonoplankton food. Likewise, a jellyfish bloom that coincided with the peak NS bloom could have reduced the population of herbivorous zooplankton (particularly copepods) that could compete with NS for diatom prey, which may have helped to establish favorable conditions for NS bloom initiation.