Extensive Chaetoceros curvisetus bloom in relation to water quality in Port Blair Bay, Andaman Islands Mehmuna Begum & Biraja Kumar Sahu & Apurba Kumar Das & Nambali Valsalan Vinithkumar & Ramalingam Kirubagaran Received: 31 July 2014 /Accepted: 18 March 2015 # Springer International Publishing Switzerland 2015 Abstract Blooming of diatom species Chaetoceros curvisetus (Cleve, 1889) was observed in Junglighat Bay and Haddo Harbour of Port Blair Bay of Andaman and Nicobar Islands during June 2010. Physico- chemical parameters, nutrient concentrations and phy- toplankton composition data collected from five stations during 2010 were classified as bloom area (BA) and non-bloom area (NBA) and compared. Elevated values of dissolved oxygen were recorded in the BA, and it significantly varied (p <0.01) from NBA. Among the nutrient parameters studied, nitrate concentration indi- cated significant variation in BA and NBA (p <0.01). Phosphate and ammonia concentrations reduced to be- low detection level (BDL) in the BA and NBA, indicat- ing its utilization. In Junglighat Bay, the C. curvisetus species constituted 93.4 and 69.2 % composition of total phytoplankton population during day 1 and day 2, re- spectively. The bloom forming stations separated out from the non-bloom forming station in non-parametric multidimensional scaling (nMDS) ordinations; cluster analysis powered by SIMPROF test also grouped the stations as BA and NBA. Keywords Chaetoceros curvisetus . Bloom . Phytoplankton . Water quality . Multivariate statistics . Andaman Sea Introduction Phytoplankton accounts for 95 % of marine primary productivity (Nielsen 1975). Under certain conditions, their population proliferates vigorously with apparent impact on the environment (Bhat et al. 2006). Over the past several decades, coastal regions throughout the world have experienced increasing incidences of bloom that are toxic or otherwise harmful (Hallegraeff 1993; Steidinger et al. 1999; Anderson 1997; Pan et al. 2001; Anderson et al. 2002). Harmful algal bloom (HAB) is known for its lethal effects directly on aquatic ecosys- tem and decreases the aesthetic value of the area affected (Graneli and Turner 2006). Pollution particularly in the coastal inshore water has been the most probable factor for creating eutrophic condition (Anderson et al. 2002; Heisler et al. 2008). The increasing urban population along with inputs from agriculture and atmosphere are main causes of eutrophication in the coastal regions in the recent years (Paerl 1997). Several incidents of harm- ful effects have been reported earlier in Indian waters (Rajasekar et al. 2010;D’Silva et al. 2012). In recent years, incidences of blooms of dinoflagellate Noctiluca Environ Monit Assess (2015) 187:226 DOI 10.1007/s10661-015-4461-2 M. Begum (*) : A. K. Das : N. V. Vinithkumar Andaman and Nicobar Centre for Ocean Science and Technology, National Institute of Ocean Technology, Port Blair 744103, India e-mail: mehmuna@gmail.com B. K. Sahu Department of Marine Sciences, Berhampur University, Berhampur 760007 Odisha, India R. Kirubagaran Ocean Science and Technology for Islands, NIOT, Earth System Sciences Organization, Chennai 600100, India