Seasonal Variation in Arsenic Concentration and its Bioremediation Potential of Marine Bacteria Isolated from Alang-Sosiya Ship-Scrapping Yard, Gujarat, India

Abstract

This work investigates seasonal variations in arsenic concentration at Alang-Sosiya, world's largest ship-scrapping yard situated on the Gulf of Khambhat. Annually, hundreds of ships have been dismantled, which lead to discharge large amounts of detrimental and persistent pollutants at this location. In all seasons, the arsenic concentration was significantly elevated in sediments and seawaters in the intertidal zone of Alang-Sosiya ship-scrapping yard as compared to the reference station at Ghogha, 42 km away towards the northeast. The highest arsenic concentrations in seawater and sediment samples were observed during the Winter season and Summer season respectively. The marine environment affected by ship-scrapping activity and contaminated with arsenic is the potential location to get arsenic hyper-tolerant bacterial isolates. Out of 16 isolated bacterial strains, KKDK-1 and KKDK-2 sustained 600 mM and 500 mM arsenate respectively. The 16S rRNA ribotyping identified strains KKDK-1 and KKDK-2 as Halomonas species. The strain KKDK-1 showed the maximum arsenic accumulation of 21.7±3.3 mg g-1 cell dry weight at exponential phase (60 h), followed by sudden extrusion of arsenic during stationary phase (84 h) of bacterial growth. Whereas, strain KKDK-2 accumulated 6.8±1.12 mg Arsenic g-1 cell dry weight during exponential phase (72 h), which remains almost invariable during stationary phase (96-144 h) of bacterial growth. These results indicate the hypertolerance of arsenic by KKDK-1 and KKDK-2 with its higher accumulation capacity, signifying them as potential candidates for arsenic detoxification of arsenic contaminated sites.