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.

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Heavy metal contamination in aquatic ecosystems has become an emerging environmental issue. The stable physicochemical properties of heavy metals could result in bioconcentration and bioaccumulation in different organs of freshwater fishes. The present study records the accumulation of Lead (Pb), Cadmium (Cd), Chromium (Cr), Copper (Cu) and Zinc (Zn) in the head, muscle and skin regions of seven fish species namely, Labeo rohita, Oreochromis mossambicus, Oreochromis niloticus, Etroplus suratensis, Heteropneustes fossilis, Oligolepsis acutipennis and Puntius dorsalis collected from Minnerya, Parakrama Samudraya and Kaudulla reservoirs in Polonnaruwa district, Sri Lanka. The results showed that both Pb and Cd accumulated in high concentrations in the head region compared to the skin and muscles of the fish samples. The highest amounts of Pb (22.44±5.48 mg/Kg) and Cd (4.98±0.86mg/Kg) were recorded from the head parts of the H. fossilis in Minneriya and O. niloticus in Kaudulla respectively, whereas the highest amount of Cr (30.87±4.51mg/Kg) was detected in head part of the O. acutipennis in Minneriya. The Cu concentration was the highest (2.92±0.001 mg/Kg) in head regions of H. fossilis from Minneriya. Zn was the most abundant heavy metal detected in the head, muscle and skin regions of fish in all three reservoirs. The highest amount of Zn (118.93±10.55mg/Kg) was detected in the head part of O. acutipennis from Minneriya. The Pb, Cd, Cr, Cu and Zn concentrations detected in the head part of popular edible freshwater species, O. mossambicus, O. niloticus and E. suratensis were higher than the provisional tolerable weekly intake (PTWI) of Pb (0.025 mg/Kg), Cd (0.007 mg/Kg), Cr (0.1 mg/Kg), Cu (3.5 mg/Kg) and Zn (7 mg/Kg) specified by the FAO/WHO. Therefore, long-term consumption of these fish species especially the head parts may lead to accumulation of these heavy metals in tissues and lead to chronic diseases which may risk the health of consumers especially in the north-central province of Sri Lanka.

Microcystin-LR (MC-LR) is a cyclic peptide produced as a secondary metabolite of certain freshwater cyanobacteria species such as, Microcystis, Anabaena, and Oscillatoria. Biodegradation of MC-LR by heterotrophic bacteria have been accepted as a reliable and cost effective method to treat MC-LR contamination. To date, more than 30 different bacterial genera have been recorded as potential MCs degraders. However, limited information are available on MC-LR degradation mechanism of bacteria. Intracellular MC-LR degradation by enzymes encoded by mlr A,B,C and D genes is the only hypothesis accepted so far. Hence, the present study focused on the elucidation of MC-LR degradation mechanism of KJ954304 Bacillus cereus 12GK strain which was previously isolated and characterized by authors as an efficient MC-LR degrader. Overnight grown and starved B. cereus bacterial suspension (0.5 µl) was inoculated into 100 ml of filter sterile (0.2 μm) Beira lake water containing MC-LR at a final concentration of 5 µgml -1 . Control sample was prepared without bacterial inoculation. All flasks were incubated at 28°C and shaken at 100 rpm for 3 days. Following three days of incubation 0.5 ml sub sample aliquot was removed from both experimental and control flasks and frozen at (-20°C). Then 45 ml of experimental sample was kept aside as initial experimental sample and remaining 45 ml of sample was filtered under sterile conditions using 0.2 μm filter to remove bacterial cells. Then the filtrate was placed immediately in ice to prevent denature of enzymes. Subsequently, MC-LR was spiked to both initial experimental samples and filtered samples at a final concentration of 5µgml-1, and incubated at 28 0 C, 100 rpm for 3 days. 1ml aliquots were removed from initial experimental sample and filtrate sample for 0-3 days of incubation. These samples were frozen and processed for High Performance Liquid Chromatography (HPLC) analysis. A PCR analysis was carried out to detect the presence of MC-LR degrading mlr A,B,C and D genes in B. cereus. Amplifications were performed in 50 µL volumes, containing 1 mM of each primer. A GeneAmps 2400 PCR System was utilized for the amplifications.At the end of 3 days of experiment MC-LR concentration of the initial experimental sample with bacteria was 1.8 µgml -1 whereas the filtrate sample without bacteria had 4.8 µgml -1 of MC-LR. Furthermore, the PCR study confirmed the presence of mlr A,B,C and D genes in B. cereus. Thus, MC-LR degradation is performed as an intracellular degradation by B. cereus with the involvement of intracellular enzymes.

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