This study assessed the water quality of Mengkuang
Reservoir, Penang, Malaysia, by its trophic status
according to a Carlson Modified Trophic Index (CMTSI)
and by its biological parameters using Shannon–Wiener
diversity index (H'
) and saprobic index. The study conducted
from August 2005 to July 2006 showed that mean
values of CMTSI (nutrients), CMTSI (chlorophyll α) and
CMTSI (Secchi depth) were 27.18 ± 8.73, 40.63 ± 7.12
and 41.74 ± 6.38, respectively. The mean values of
CMTSI indicated that the reservoir was oligotrophic. Mean
value of H'
was 2.15 bits/individual, showing that the water
quality based on H'
value was in class III (slightly polluted).
Saprobic index value (2.24) also revealed that the
reservoir was moderately polluted (class II). The occurrence
, Staurastrum paradoxum
which are indicators of toxic and polluted
waters was also recorded. This study therefore showed the
importance of phytoplankton composition and community
structure as a reliable and important tool to assess the
degree of pollution in Mengkuang Reservoir. Long-term
assessments of biological and chemical parameters in the
reservoir are necessary, and phytoplankton community
structure as bioindicator provides unique information about
the ecosystem. This information is potentially useful as an
early warning sign of deteriorating condition and thus gives
insight into the overall ecology of lakes and will assist in
the future conservation and management of this lentic