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Effects of hydrography on the distribution of bacteria and virus in Cochin estuary, India

Parvathi, Ammini, Jasna, V., Jina, S., Jayalakshmy, K. V., Lallu, K. R., Madhu, N. V., Muraleedharan, K. R., Naveen Kumar, K. R., Balachandran, K. K.
Ecological research 2015 v.30 no.1 pp. 85-92
ammonium nitrogen, bacteria, chlorophyll, dissolved oxygen, estuaries, hydrology, monitoring, nitrate nitrogen, nutrients, pH, plate count, salinity, statistical analysis, temperature, viruses, water quality, India
The viral dynamics have rarely been investigated in estuarine environments of India. The present study brings out a first hand information on the distribution of virus and bacteria in an eutrophic estuary (Cochin, India). Thirteen stations were selected for monthly monitoring of bacterial abundance (BA), total viable bacterial count (TVC), viral abundance (VA), chlorophyll a (Chl a) and other water quality parameters (temperature, salinity, pH, dissolved oxygen and inorganic nutrients such as NO₃–N, NH₄–N, PO₄–P and SiO₄–Si) for 1 year. There was significant variations in the VA [0.59–4.48 × 10⁷viral like particles (VLPs) mL⁻¹] and BA (0.49–8.12 × 10⁶ cells mL⁻¹) in the estuary. The variation in the viral to bacterial ratio (3–22) indicated marked seasonality. Statistical analysis showed bacteria as a major factor controlling the distribution of viruses (60 % variability) in Cochin estuary (CE). The viruses also showed positive correlations with Chl a, pH and salinity. The distribution of virus followed a distinct pattern of three different zones in the estuary controlled by salinity in zone I, Chl a in zone II and salinity, Chl a in zone III. The zonal distribution suggests that the factors that control the viral-host systems vary in different areas due to the complex hydrography of the estuary and environmental changes are very sensitive to the viral population in CE.