Chalinda Ariyadej, Phimphan Tansakul, and Saowapa Angsupanich

pp. 595 - 607

Abstract

The diversity of phytoplankton and its relationships to the physico-chemical environment were
studied in Banglang Reservoir, located on the Pattani River in Southern Thailand. Samples were collected
monthly from May 2000 to April 2001 at three stations and three different depths: water surface, 10, and 30
meters. Physico-chemical parameters: temperature, pH, dissolved oxygen, alkalinity, conductivity, water
transparency, and nutrients were measured simultaneously. One-hundred and thirty-five species in seven
divisions of phytoplankton were found. The greatest number of species were in Division Chlorophyta (50%),
followed by Cyanophyta (21%), Bacillariophyta (13%), Pyrrophyta (6%), Cryptophyta (4%), Chrysophyta
(3%) and Euglenophyta (3%). The most diverse genus was Staurastrum (15 species). Phytoplankton density
ranged from zero to 2.1x10⁹ cells.m^-3. Microcystis aeruginosa Kützing in January at 30 m at the lacustrine
zone had the highest phytoplankton density. By applying a PCA(principal components analysis) using the
MVSP statistical analysis program on the abundance of species, it was found that Cyclotella meneghiniana Kützing and Melosira varians Agardh were the most abundant in each station. Diversity index (Simpson’s
diversity index) was maximum at 10 m at the transition zone and lowest at the outflow zone. The factors
affecting the phytoplankton species by Canonical correspondence analysis ordination (PC-ORD program)
were alkalinity, water temperature, water transparency, nutrients and conductivity. When the water quality
parameters were classified by the trophic level, Banglang Reservoir belonged to oligo-mesotrophic status.
Furthermore, Cyclotella meneghiniana Kutzing and Melosira varians Agardh could be used as the phytoplankton indicator of oligo-mesotrophic reservoir