WATER QUALITY CHARACTERISTICS OF MENGKUANG RESERVOIR BASED ON PHYTOPLANKTON COMMUNITY STRUCTURE AND PHYSICO- CHEMICAL ANALYSIS

ASIEH MAKHLOUGH (2008)

ABSTRACT

This study was carried out at Mengkuang Reservoir (M.R), Penang, in the northwest of Malaysia. This study focused on the spatio-temporal variation of phytoplankton composition and physico-chemical parameters, and was conducted due to the importance of the reservoir as a drinking water supply and also the lack of algological data of the studied area. Nine sampling stations were selected with six stations in littoral zone and three stations in the limnetic zone. Monthly samples were collected from the water surface to the bottom, with 5 meter intervals over a one-year period from August 2005 to July 2006, which were comprised of two different tropical seasons (the dry and rainy seasons). Physico-chemical parameters showed the following ranges on the surface water of Mengkuang Reservoir: temperature (29.28 – 33.50 ºC), DO (3.25 – 9.20 mg/l), COD (2 – 54 mg/l), pH (4.5 – 9.44), EC (40 - 70 μS/cm), TSS (0.22 – 30.00 mg/l), transparency depth (1.15 – 3.10 m), Chl-a (0.03 – 19.36 mg/m3), gross primary production (14.27 – 100.25 mgC/m3/hour), PO4-P (0.00 – 0.07 mg/l), NH4 +-N (0.00 - 0.32 mg/l) and NO3 - -N (0.00 – 0.13 mg/l). The seasonal variation was observed in nitrate, EC, TDS, transparency depth, and abundance of phytoplankton which were significantly higher during rainy season (p more than 0.05). Temperature, DO, pH, Chl-a and abundance of phytoplankton decreased from the surface to the bottom, while EC, TSS, TDS, total phosphorus and total nitrogen increased vertically towards the bottom. The results indicated that abundance of phytoplankton was affected by nitrogen and phosphate, ions availability and light penetration. On the other hand, these physical and chemical factors were affected by the amount of rainfall, water pumping and water draw off, inter cycling process (decomposition and mineralization) as well as biological community. A total of 128 phytoplankton species were identified. The dominant division was Chlorophyta, which were mainly composed of Staurastrum apiculatum and Staurastrum paradoxum. The third and fourth dominant species were Glenodinium lenticula (Pyrrophyta) and Lyngbya sp. (Cyanophyta), respectively. The range of evenness and Shannon-Weiner’s index was 0.43-0.56 and 1.91-2.45 (bits/individual) in M.R, respectively. Calculation of the Carlson modified trophic state index showed that the reservoir was near to a mesotrophic state based on Chl-a and transparency depth. The mesotrophic state of the reservoir was also confirmed by the N/P ratio value. Based on the Shannon-Weiner’s and saprobic indices, the reservoir was in class III (slightly polluted) and class II (moderately polluted), respectively. The study also recorded the presence of Anabaena, Microcystis, Oscillatoria, Nostoc, Dinobryon, Chroococcus, Staurastrum paradoxum and Mallomonas which are indicators of toxic, unfavorable odors and flavors, and pollution in aquatic ecosystems. As a conclusion, this study showed the ability of algological studies to provide early warning of water degradation and its importance in water quality assessment.

Masters thesis, Universiti Sains Malaysia.