Contamination Status of Algae Toxins Microcystins in Some Selected Water Bodies in Sri Lanka

Abstract

Harmful cyanobacterial (blue-green algae) blooms, are common in eutrophic waters. Certainbloom forming species such as Microcystis, Anabaena, Nostoc and Planktothrix/Oscillatoriaare a serious threat to water quality due to the potent toxins production. Microcystins, thecyclic heptapeptides produced by cyanobacteria, are hepatotoxic and tumor-promoting;inhibit protein phosphatases types 1 and 2A. WHO established a recommended level of 1 μg/lfor the most hazardous Microcystin-LR (MC-LR) for drinking water. Therefore, at watertreatment procedures both intra- and extracellular toxin levels are equally important. Morerecent studies done in Sri Lanka indicated that most inland freshwater bodies carry hightoxigenic cyanobacteria populations of twenty four genera, of which Microcystis andCylindrospermopsis are the dominant. The present study was carried out to identify andquantify nuisance algae/ cyanobacteria and potential contamination level of MC-LR in tenselected water bodies used for irrigation, drinking and recreational purposes. Water andphytoplankton sampling was done from February 2011 to February 2012. Some water qualityparameters crucial in algae growth were determined using standard chemical andspectrophotometric methods. Presence of MC-LR was screened by the Immuno Strip kit atthe site and ELISA method in the laboratory. Total phosphates in all ten water bodies wereranged between 0.034-0.315 mg/l and nitrates were <0.1 mg/l respectively. Microcystis sp.which mainly produces microcystin variants was the dominant cyanobacteria in a majority ofwater bodies (Kanthale 98.51%, Girithale 92.68 %, Kondawattuwana 91.05 %, Nuwara wewa66.83%, Jayanthi wewa 65.05%). Cylindrospermopsis sp. which producescylindrospermopsin was recorded in Nuwara wewa (1.89%) and Kondawattuwana (0.06%).Anabaena sp. which produces microcystin variants was detected in Girithale (0.76%) andJayanthi wewa (1.33%). Both Cylindrospermopsis sp. and Anabaena sp. were recorded inlow abundance compared to Microcystis sp. All ten water bodies were screened for MC-LRby the Immuno Strip kit resulted in low to moderate risk (0-15 μg/l) condition. It was furtherconfirmed that some water bodies (used for drinking and other domestic consumption) inSouth East and North East area were contaminated with MC-LR. Microcystins were detectedin Weeragoda tank as 0.146 μg/l, Jayanthi wewa 0.712 μg/l, Kondawattuwana tank 0.441μg/l, Kanthale tank 0.2 μg/l and Unnichchai tank 1.3 μg/l during the non bloom situation.Though the recorded MC-LR contamination was below the permitted values given by theWHO, there is a risk in the near future making water unsuitable for drinking purposes asthere is an increasing tendency of growing toxic cyanobacteria species in all water sourceswhich are used for drinking.