Abstract:
The relationship between some physico-chemical parameters and bioindicators in Bolgoda canal
and Waga stream in Colombo, Sri Lanka was assessed from February to July 2010. The objective of the
study was to evaluate the quality of aquatic health in the two water bodies using some physico-chemical
parameters and bioindicators. Physico-chemical parameters of the Water bodies were measured. Macro
invertebrates and phytoplankton were studied as biological indicators. Quantification of macro
invertebrates were carried out and Pollution Tolerant Index (PTI) of Bolgoda canal and Waga stream was
calculated according to the standard manual published by the United States Environmental Protection
Agency (USEPA). Macro invertebrate component in the Bolgoda canal represented both moderately
pollution tolerant (Nepa cinerea, Zygopteran nymphs) and pollution tolerant (Planorbella trivolvis,
Promacea bridgesi, Gerris sp, Lethocerus americanus, Plea frontalis, Cerithiidae sp, Tubifex tubifex)
organisms while in Waga stream only pollution sensitive organisms (Paludomous loricatus, Paludomous
zeylanicus, Cylindrostesthus productus, Plecopteran nymphs, Psephenidae larvae, Aegla sp,
Ephemeropteran nymphs) were reported. The PTI value of Bolgoda canal ranged from 17.00 to 19.90
where as in Waga stream was ranged from 34.00 to 39.60 indicating poor and good water quality
respectively. The phytoplankton composition of both water bodies were analyzed using Shannon Wiener
Diversity Index (SWDI). SWDI for phytoplankton in Bolgoda canal was ranged between 0.674±0.36 and
1.513±1.80 and in Waga stream was ranged from 1.89±0.72 - 3.01±1.89 indicating low and high diversity
respectively. Data analysis by Principle Component Analysis (PCA) showed that physico-chemical
parameters, PTI and SWDI of the sampling locations in Bolgoda canal and Waga stream were clustered
into three distinct groups according to the site selection. Regression analysis showed temperature, pH,
DO, nitrate concentration and BOD had a significant effect on the PTI value of the Bolgoda canal and
Waga stream.
