Monitoring the Diatom bloom of <i>Leptocylindrus danicus</i> (Cleve 1889, Bacillariophyceae) in the coastal waters of South Andaman Island

Abstract

Hydrographical parameters were studied and nutrients such as nitrate, nitrite, phosphate and silicate were measured. Temperature ranged from (24.5-27ºC), Salinity ranged from (19-25 psu). Nutrients such as nitrite varied between 0.23-1.009 µmol. l^-1, nitrate (0.63-4.71 µmol. l^-1), phosphate (0.02-0.23 µmol. l^-1) and silicate concentrations remained much higher and exhibited between the ranges of 4.07-10.37 µmol. l^-1. Biomass expressed in terms of chlorophyll <i>a</i> was high, ranged from 0.09-0.267µg. l^-1. It was found out that an increase in the nutrient content has initiated the bloom. In the present investigation, following species of phytoplankton were found to be common; diatoms such as <i>Bacteriastrum </i> sp.,<i> Cerataulina </i> sp.,<i> Chaetoceros </i> sp.,<i> Corthron </i> sp., <i>Coscinodiscus </i> sp., <i>Guinardia </i> sp.,<i> Odontella </i> sp.,dinoflagellatessuch as <i> Ceratium </i> sp.,<i> Gonyaulax </i> sp.,<i> Gymnodinium </i> sp.,<i> Prorocentrum </i> sp and <i> Protoperidinium </i> sp. An increase in rain fall (904.0 mm) during September 2012 due to south west monsoon which was also found to be major factor that contributed to the bloom.