Hydrography induced changes in viral-induced mortality of prokaryotes in a monsoon driven tropical estuarine system (Cochin estuary, India)

Parvathi A1, Jasna Vijayan1 and Pradeep Ram AS2
1CSIR-National Institute of Oceanography, Regional Centre (CSIR), Kochi-682 018, India
2Laboratoire Microorganismes : Génome et Environnement, UMR CNRS 6023, Université Blaise Pascal, 1 Impasse Amélie Murat, , 63178 Aubière Cedex, France

Limited information exists on the structure and dynamics of planktonic viruses in monsoon driven tropical estuarine systems. The community structure, functioning, species diversity and succession of viral hosts such as prokaryotes and phytoplankton are influenced largely by their viruses through lysis, horizontal gene transfer and as divers of energy and nutrient cycling. The present study was conducted to determine the distribution, dynamics and diversity of viral assemblages in one of the largest monsoonal estuaries, the Cochin estuary (CE) in India. Significant variation in viral and bacterial characteristics was observed across the salinity gradient. The mesohaline regions of the estuary was characterized by high viral abundance, lytic infection and production which was accompanied by low bacterial growth efficiency and high bacterial respiration. Significant seasonal and spatial variations were seen in the viral communities and frequency of viral induced mortality of prokaryotes. The poster represents seasonal modification in the microbial loop due to the changes in hydrography characteristics, viral infection and production. Our data suggests that both bacteria and viruses appear to be strongly linked to environmental conditions induced by hydrography in this estuarine system which may affect the processes at the ecosystem scale.