Phytoplankton Composition, Abundance and Temporal Variation in Relation to Some Environmental Parameters

Abstract

This study was carried out in the Karnaphuli river estuary from December 2007 to August 2008 covering three seasons namely post monsoon, pre monsoon and monsoon. Based on the data collected from 3 stations, phytoplankton composition, abundance and temporal variation were examined. A total of 13 genera under 4 division namely Bacillariophyta (6 genera), Cyanophyta (4 genera), Euglenophyta (2 genera), and Chlorophyta (1 genera) were recorded from the study area. Five genera were found to be dominant in phytoplankton abundance and these were melosira (20.88%), coscinodiscus (15.21%), nitzschia, anabaena and trachelomonas (10.23%). The most dominant genus was melosira which showed frequent presence in all seasons and stations. Average diversity index (H′), richness index (Ma) and evenness values were 4.43, 2.12 and 2.02 respectively. Among the eleven environmental parameters tested in this study, salinity and water temperature were found to be most dominant factors to control phytoplankton distributions. Higher phytoplankton concentration recorded during the monsoon was probably due to the suitable environmental condition. Phytoplankton abundance in the Karnaphuli estuary increased seaward through the trend in salinity. A good positive correlation coefficient value (r=0.71) was recorded for total phytoplankton and salinity. Study on seasonal fluctuation of different environmental parameters indicating that fresh water discharge is the major controlling factor in the Karnaphuli river estuary where nutrient variables and turbidity showed the minimal effect on overall phytoplankton distribution. A regression plot analysis exhibit a positive value i.e. R2 = 0.51 or correlates with each other up to 51%.