Geographic information systems and multivariate analysis to evaluate fecal bacterial pollution in coastal waters of Andaman, India

Urbanization of coastal areas in recent years has driven us to consider a new approach for visually delineating sites that are contaminated with fecal bacteria (FB) in the coastal waters of the Andaman Islands in India. Geo-spatial analysis demarcated harbor, settlement, and freshwater/discharge influenced zones as hot spots for FB, while the open sea was demarcated as a cold spot. The land use types, such as developed and agriculture, with more anthropogenic activities increasing the FB counts while open sea showed the least FB. Box whisker plot indicated an increasing FB trend in the coastal waters during monsoon. Furthermore, principal component analysis revealed 67.35%, 78.62% and 70.43% of total variance at Port Blair, Rangat and Aerial bays, respectively. Strong factor loading was observed for depth (0.95), transparency (0.93), dissolved oxygen (0.93) and fecal streptococci (0.85). Distance proximity analysis revealed that fecal contaminations diluted significantly (P < 0.05) at the distance of 2.1 km toward the deeper or open sea water. This study demonstrates the effectiveness of an integrated approach in identifying the sources of fecal contamination and thus helping in better monitoring and management of coastal waters. - Highlights: • Hot spot analysis is a useful tool for visually delineating the FB contaminated areas. • Harbor, settlement and freshwater discharge influenced zones were demarcated as hot spots for FB. • The open sea was demarcated as a cold spot. • Fecal count diluted significantly @ 2.1 km from the sampling point toward deeper or open sea water. - Geo-spatial analysis demarcated harbor, settlement and freshwater/discharge influenced zones as hot spots for fecal bacteria and the contamination was significantly diluted @ 2.1 km toward the deeper or open sea water.