Spatio-temporal distribution of chlorophyll-a in relation to physico-chemical parameters in coastal waters of the northwestern Bay of Bengal S. K. Baliarsingh & Aneesh A. Lotliker & K. C. Sahu & T. Sinivasa Kumar Received: 7 October 2014 /Accepted: 1 June 2015 /Published online: 1 July 2015 # Springer International Publishing Switzerland 2015 Abstract The present study focuses on understanding the long-term distribution of physico-chemical parame- ters and their influence on the distribution of chloro- phyll-a (chl-a) at a coastal site in the northwestern Bay of Bengal. Chl-a showed large variability (0.12 to 10.05 mg m -3 ) on a spatio-temporal scale during the study period. However, the distribution showed a simi- lar pattern with marginal variability from March 2010 to February 2011 and March 2011 to February 2012. The vertical distribution of salinity, pH, total suspended mat- ter (TSM) and chl-a showed systematic temporal vari- ability. However, dissolved oxygen (DO) and nutrients (nitrite + nitrate, phosphate, silicate) did not show any significant spatio-temporal trend. Chl-a showed bimod- al distribution on an annual scale, with the first peak appearing during the pre-monsoon period in March due to a seasonal phytoplankton bloom, whereas the second peak occurring during September as a result of nutrient loading from river influx due to monsoonal precipita- tion. Factor analysis revealed the association of low salinity and high nutrients with chl-a. This infers that the nutrients brought by the influx of river into the study area were fuelling the growth and abundance of phyto- plankton. Cluster analysis resulted in two distinct clus- ters among all physico-chemical datasets, indicating the presence of two distinct areas separated by the 30 m isobath that were strongly influenced by physico- chemical characteristics associated with the seasonal monsoon. Keywords Chlorophyll-a . Nutrients . Monsoon . Cluster analysis . SATCORE Introduction The transition zone between land and open sea experi- ences high fluxes of freshwater bringing nutrients and organic matter from adjoining rivers, resulting in high productivity (Jickells 2005; Laane et al. 2005). These zones have a major contribution to global primary pro- duction despite their relatively small volume. Over the past decades, human activities have accelerated the sup- ply of land-derived nutrients to the coastal ocean which contribute to a complex ecosystem influenced by large fluctuations in physico-chemical and biological param- eters (Alheit 2009). This multitude of physical, chemical and biological processes including seasonal tropical monsoons plays a critical role and exerts significant stress on coastal habitats (Sournia 1969; Cloern 2001; Turner et al. 2003; Hebbeln and Paul 2009). In the aquatic ecosystem, phytoplankton play a vital role in nutrient cycling and overall food web dynamics. The major phytoplankton pigment, chlorophyll-a (chl- Environ Monit Assess (2015) 187: 481 DOI 10.1007/s10661-015-4660-x S. K. Baliarsingh : A. A. Lotliker (*) : T. Sinivasa Kumar Indian National Centre for Ocean Information Services (INCOIS), Ocean Valley, Pragathi Nagar (BO), Nizampet (SO), Hyderabad 500 090, India e-mail: aneesh@incois.gov.in K. C. Sahu Department of Marine Sciences, Berhampur University, Brahmapur, Odisha 760007, India