Interannual and cyclone-driven variability in phytoplankton communities of a tropical coastal lagoon

• Phytoplankton communities in lagoon were eurytopic in nature having a wide salinity tolerance.
• Phailin altered the nutrient regime of the lagoon from nitrate limiting to phosphate limiting conditions.
• Increase in turbidity after the Phailin prevented the development of phytoplankton blooms.
• Salinity and light availability were the major ecological driver of phytoplankton communities.

One of the main challenges in phytoplankton ecology is to understand their variability at different spatiotemporal scales. We investigated the interannual and cyclone-derived variability in phytoplankton communities of Chilika, the largest tropical coastal lagoon in Asia and the underlying mechanisms in relation to environmental forcing. Between July 2012 and June 2013, Cyanophyta were most prolific in freshwater northern region of the lagoon. A category-5 very severe cyclonic storm (VSCS) Phailin struck the lagoon on 12th October 2013 and introduced additional variability into the hydrology and phytoplankton communities. Freshwater Cyanophyta further expanded their territory and occupied the northern as well as central region of the lagoon. Satellite remote sensing imagery revealed that the phytoplankton biomass did not change much due to high turbidity prevailing in the lagoon after Phailin. Modeling analysis of species–salinity relationship identified specific responses of phytoplankton taxa to the different salinity regime of lagoon.