6. Mercury-Resistant Marine Bacterial Population in Relation to Abiotic Variables at the Bay of Bengal, India

Sediment and water samples were collected during monsoon and summer seasons for 2 years from four study sites, viz. Paradeep, Chilika, Gopalpur, and Rushikulya, along the Bay of Bengal, Odisha, India. Samples were analysed for abiotic parameters such as pH, salinity, temperature and total mercury content. Similarly, total heterotrophic bacterial load and mercury-resistant marine bacterial load were analysed in the collected samples. The pH of water samples in all the study sites varied from 6.41 ± 0.014 to 8.4 ± 0.141 during the summer season, whereas during the monsoon season it varied from 6.535 ± 0.077 to 8.55 ± 0.070. Similarly, the salinity in the study sites ranged from 9 ± 1.414 psu to 36.5 ± 0.707 psu during the summer season and 4.5 ± 0.707 psu to 34.5 ± 0.707 psu during the monsoon season. The temperature of the water also followed the same trend that varied from 26.55 ± 1.343 °C to 38.5 ± 0.141 °C in the summer season, and during the monsoon season the range was 21.85 ± 0.494 °C to 28.95 ± 0.636 °C. Sediment samples showed to contain a higher amount of mercury at Rushikulya (2.48 and 2.26 ppb) among the study sites in both seasons followed by Paradeep, Chilika and Gopalpur. Huge fractions of marine bacteria were found to be mercury resistant in nature, and a strong positive correlation (r = 0.94 and 0.93 in water and sediment samples) was obtained between mercury content and the mercury-resistant marine bacterial populations in the Bay of Bengal, India.