A Study On Limnology And Phytoplankton Biodiversity Of Ahning Reservoir, Kedah
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Date
2006-05
Authors
Chan, Kok Yeng
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Abstract
A monthly study of the limnology and phytoplankton biodiversity at Ahning Reservoir
was carried out between November 2002 and October 2003. A total of 8 sampling
stations were selected in this study. The physical parameters were measured in-situ
from surface to the 10m depth with one meter intervals. Water samples were taken at
surface, Secchi depth and three meters below Secchi for chemical parameters
analysis. Chlorophyll a was measured and phytoplankton was identified at the
laboratory for both upper and deeper layer at all sampling stations. The dissolved
oxygen, temperature and pH decreased vertically at all sampling stations. However, the
conductivity was increased vertically. The chemical parameters were also higher at the
deeper depth. The range for each parameter in this study were D.O. (3.44 - 8.35
mg/L), water temperature (26.94 - 34.09 °C), pH (6.32 - 8.86), conductivity (40.8 -
59.2 mS/cm), TSS (0.20 - 45.20 mg/L), Secchi depth (0.28 - 2.27 m), P04-P (O.OH -
0.038 mg/L), NOrN (0.0002 - 0.0023 mg/L), N03-N (0.03 - 1.92 mg/L) and NH4-N
(0.020 - 0.091 mg/L), Productivity and chlorophyll a levels were low (mean
33.61±19.22 mgC/m3/hour and 2.25±1.25 mg/L) during the study period. The measured
parameters vary with the total rainfall in this study. Lower concentrations of measured
parameters were recorded during the rainy season. This showed that rainfall play an
important role of dilution factor at Ahning Reservoir. A total of 164 phytoplankton
species were recorded in this study and Chlorophyta was the major taxa of
phytoplankton. The dominant phytoplankton species was Staurastrum leptoc/adium
followed by Cosmarium bioculatum and Cosmarium subtumitum. The Evenness Index
and Shannon Weiner's Index were ranged 0.413 - 0.621 and 0.836 - 1.328
respectively. Seasonal changes of relative abundance of phytoplankton were recorded
in this study. The higher abundance of phytoplankton during the rainy season may due
to increase of other micronutrients as the major nutrients of nitrate-nitrogen and
orthophosphate remained low. There was lack of nutrients input from the catchment
area thus the unclear forest at Ahning Reservoir was the major nutrients source. The
internal recycling of nutrients was important at Ahning Reservoir and seasonality also
influences the interactions of all measured parameters in this study.
Description
Keywords
Study of the limnology and phytoplankton , biodiversity at Ahning Reservoir