Water pollution due to a harmful algal bloom: a preliminary study from two drinking water reservoirs in Kandy, Sri Lanka

A dysenteric epidemic condition occurred in a community of people who consumed water from the two reservoirs, Rosmith and Dunumadalawa in Kandy on 29th and 30th of September 2008. The symptoms were diarrhoea, vomiting and headache. It was suspected that the epidemic could relate to the water supply from the two reservoirs. To investigate the sources that caused the disease, water samples were analysed for potentially harmful biological organisms. A dinoflagellate species, Peridinium aciculiferum, known to produce a biological toxin under special environmental conditions, was identified for the first time in Sri Lanka from the samples. The relative abundance of P. aciculiferum ranged from ~75% to 100% of the plankton samples taken from all sites. The abundance and diversity of other organisms at the same trophic level were low and the eutrophication conditions were also predominant in both reservoirs at the time of sampling. It is therefore suggested that P. aciculiferum had outcompeted the other planktons in the reservoirs and the epidemic condition had arisen due to the algal toxins present in the reservoirs during the drought period.

Keywords: Algal toxins, freshwater dinoflagellates, freshwater red tide, Peridinium aciculiferum, water pollution.

Doi: 10.4038/jnsfsr.v39i1.2930

J.Natn.Sci.Foundation Sri Lanka 2011 39 (1):91-94