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Algal Bloom Identified on Hobart's Eastern Shore

23 January 2009
The presence of a pinkish-red coloured slick in the Derwent estuary has been reported to the EPA by a number of Hobart residents. The Director of the Environment Protection Authority, Warren Jones says the slick stretching from Ralphs Bay, Tranmere up the River Derwent to Little Howrah Beach has been identified as a dinoflagellate, Noctiluca scintillans. "Officers representing the EPA have received several calls over the past two weeks from residents concerned about the pink substance in the water and wondering if it was a result of pollution," Mr Jones said. "Samples have been taken and examinations in the laboratory have identified the slick as the dinoflagellate." "Noctiluca scintillans usually appears as a pink coloured slick and is sometimes mistaken as an oil spill," Mr Jones said. It is not uncommon to see Noctiluca scintillans in waters around Tasmania. There have been reports in recent years from a number of locations including Falmouth, Bicheno, Bruny Island, Prion Bay and the Hobart docks. During the day the blooms can look like pinkish clouds in the water; at night they glow due to bioluminescece. Mr Jones said while some dinoflagellate blooms can cause the release of toxins, there are no known toxins in the dinoflagellates that form this algal bloom. The Director of Public Health Dr Roscoe Taylor said that while there were no known public health issues associated with this species, if individuals are concerned they may wish to avoid swimming in areas where the bloom is present. "The bloom may also discolour some shellfish such as oysters and mussels in areas where Noctiluca scintillans is clearly visible, but there would be no additional risk to humans if these shellfish were to be consumed," Dr Taylor said. However, Dr Taylor added that the general public is advised not to collect and consume any wild shellfish because of the possible presence of other pollutants.
This is what the pink coloured slick looked like a Tranmere earlier this month
The bloom stretches from Ralphs Bay up the River Derwent to Little Howrah Beach.
Another shot of the slick at Little Howrah Beach