Phytoplankton from Vam Co River in Southern Vietnam

In this study we investigated the variation of phytoplankton and the water quality in Vam Co River, Southern Vietnam. Phytoplankton were bi-monthly monitored in 2011 at 12 sampling sites in the river. Some basic environmental parameters were also monitored including temperature, pH, turbidity, inorganic nitrogen and dissolved phosphorus. The phytoplankton biodiversity and Diatomeae indices were applied for environmental quality evaluation. The results showed that temperature ranged from 28.7 – 31.9 °C during the monitoring. The pH and turbidity were in between 3.9 – 7.0 and 2 – 64 NTU, respectively. The nitrate and ammonium concentrations were from 0.06 – 1.21 and 0.03 – 1.15 mg/L, respectively. The phosphate concentration was between 0.02 and 0.37 mg/L. The environmental parameters were favorable for phytoplankton development. The phytoplankton analyses showed that there were 290 species of diatoms, green algae, golden algae, yellow algae, euglenoids, dinoflagellates and cyanobacteria of which green algae and diatoms were dominant in species number. Phytoplankton density ranged from 920 – 383 600 individuals/L with the main dominant species of diatoms. The biodiversity index values during the monitoring were from 0.15 – 3.80 characterized for oligotrophic to eutrophic conditions whereas the Diatomeae index values were more than 0.2 indicating for the eutrophic characteristic of the aquatic environment. Besides, phytoplankton species number positively correlated with temperature but negatively correlated with nitrate concentration. Additionally, the biodiversity positively correlated with temperature and species number, but negatively correlated with nitrate and phytoplankton abundance. The results confirmed the advantage of using phytoplankton and their indices for environmental monitoring and water quality assessment.