Variation and Relationship between Water Qualities and Phytoplankton along the Coast of The Upper Gulf of Thailand

Abstract

This study aims to investigate the composition of phytoplankton, variation, and the relationship between water qualities and phytoplankton. Seawater samples were collected bimonthly from 6 stations along the coastal area of the upper gulf of Thailand during November 2017 to September 2018 a total of 6 times. A total of 75 genera of phytoplankton were found in this study. The Bacillariophyceae was found as the dominant group throughout the year, followed by Dinophyceae. The density of phytoplankton varied between 3,421-2,427,088 cells/L. The average density of the Blue-green algae and Dinoflagellate was significantly different among 6 stations (p < 0.05). Additionally, the average density of the Green algae and Dinoflagellate between the two seasons was also significantly different (p < 0.05). From the analysis of the relationship between water qualities and the density of each group of phytoplankton, it was found that the Green algae had a positive correlation with nitrate, ammonium, and phosphate (r=0.56, 0.61, and 0.57, respectively). It also had a negative correlation with pH (r=0.70). On the other hand, Dinoflagellates had a positive correlation with pH and dissolved oxygen (r=0.53 and 0.49, respectively) and a negative correlation with silicate (r=0.50).