Authors:

Abstract

This study was performed to detect the presence of cyanotoxin producing organisms in the reservoirs of the Anuradhapura Distrct. Water samples were collected from Kala wewa, Tissa wewa and Nuwara wewa in Anuradhapura. Environmental and cultured samples were subjected to PCR to detect cyanobacteria, Microcystis, microcystin, Cylindrospermopsis and cylindrospermopsin, targeting the specific 16S rRNA and cpc, mcyA and mcyE, cylindrospermopsin synthetase (rpoC1) and cylindrospermopsin specific peptide synthase (PS) genes, respectively. All tested samples were positive for unicellular and five were positive for filamentous cyanobacteria. In all three reservoirs, positive amplification was observed for mcyA/ mcyE genes indicating the presence of cyanobacterial strains with genetic potential to produce microcystins. A positive amplification resulted in samples cultured from Nuwara wewa for rpoC1 gene confirming the presence of Cylindrospermopsis species in the reservoir. Further more, an environmental sample from Nuwara wewa was positive for PS gene confirming the presence of toxic Cylindrospermopsis species, and thereby cylindrospermopsin in that reservoir. Bioassay was performed using Artemia salina to test the toxicity of water samples.

Filtrates and filters were assayed and in all three tanks, higher toxicities were recorded for filters of both environmental and cultured samples. Among filters, the highest toxicity was recorded in two environmental samples from Nuwara wewa with a mean LD50 value of -694 ppm. Among cultured samples, the highest toxicity of -1128.28 ppm was recorded from Kala wewa. According to molecular and bioassay findings, all three lakes have a wide distribution of cyanobacterial species with toxin generating ability and it might be a potential risk factor for the health issues that prevail in the Anuradhapura District.

Keywords: Bioassays, cyanotoxins, Cylindrospermopsis, Microcystis, PCR.

DOI: http://dx.doi.org/10.4038/jnsfsr.v40i2.4443

J.Natn.Sci.Foundation Sri Lanka 2012 40(2):157-167

Keywords: Bioassays, cyanotoxins, Cylindrospermopsis, Microcystis, PCR