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Coastal slicks caused by algal blooms |
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Written by Alan Richardson
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 Trichodesmium algae bloom near Enderby Island in the Dampier Archipelago. In recent weeks the Department of Environment and Conservation has received several calls regarding slicks in local waters thought to be possible oil spills.
The slicks have in fact been Trichodesmium algal blooms which have been observed throughout waters of the Dampier Archipelago and surrounding areas.
Trichodesmium blooms, commonly known as a ‘red-tide’ or ‘sea-sawdust’, can be highly variable in colour, ranging from green to purple to rust reds and mustard yellows, but those observed recently have typically been pinkish-brown.
Trichodesmium algal blooms are often thought to be oil or other pollutant spills but Dampier Port Authority environment manager Wayne Young said there was an easy way to check if a slick was algae.
“The best test is to dip a stick into the slick, then dip it into clear water. If it is Trichodesmium it will wash off easily, but if it is oil it will remain stuck to the stick,” Mr Young said.
Department of Environment and Conservation Pilbara Region marine program coordinator Cath Samson said another good indicator of algal bloom was the smell, as Trichodesmium had a very distinct, strong fishy smell.
“People are advised not to come in contact with the algae as it can be toxic and can cause skin irritations and vomiting if swallowed,” Dr Samson said.
Trichodesmium is naturally occurring blue-green algae and commonly occurs in north west waters between September and December as sea temperatures start to rise.
Although it generally forms a thin layer on the surface of the water it can develop into large slicks several centimeters thick where it is concentrated or becomes trapped against the shore by wind or currents.
Trichodesmium is thought to play an important role in the marine ecosystem as it is one of a few algae that is capable of taking nitrogen gas from the air and transferring it into a form that is useable by other plants and animals in the marine food chain. |
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Last Updated ( Monday, 30 November 2009 )
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