Influence of anthropogenic activities on the spatial distribution of heterotrophic, indicator and pathogenic bacteria around Andaman and Nicobar Islands

To examine the influence of anthropogenic activities on the marine ecosystem around the Andaman and Nicobar Islands, a study was conducted to investigate the abundance of heterotrophic, indicator and pathogenic bacteria during the monsoon season. We noticed the higher abundance of heterotrophic, indicator (Escherichia coli and Enterococcus faecalis) and pathogenic bacterial counts (Aeromonas hydrophila, Enterobacter aerogens, Escherichia coli strain O157:H7, Shigella dysenteriae and Vibrio parahaemolyticus) near the 10o channel, which is the principal route to reach Andaman mainland. Most of the stations are offshore (chosen to cover shipping tracks) at a distance ranging from 41 to 266 km from the coast. The nearest station to the coast was at 21 km away. Apart from those mentioned above, several other pathogenic bacteria were also detected such as Klebsiella pneumoniae, Salmonella paratyphi, Vibrio cholera and Vibrio vulnificus but they are sparsely detected at few stations only. •This study reveals the impact of offshore activities on bacterial abundance and distribution around the A & N islands.•Higher abundance of HB, IB & PB near the 10o channel which is a major shipping channel to reach the A & N islands.•The presence of AH, EC O157:H7, EA, KP, SP, SD., VC, VP & VV in the waters around the islands is alarming.•Significant variation in bacterial counts between BoB & AS with AS has a higher human impact, especially near 10o channel.•Possible presence of these bacteria in the offshore waters might be due fishermen activities or ship based sewage release.