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Algal bloom identified on West Coast

02 Apr 2014

A naturally occurring algal bloom has formed near Coffin Bay on the West Coast of South Australia.

The bloom has resulted in localised fish and shellfish deaths, prompting an investigation by Primary Industries and Regions South Australia (PIRSA).

Recent testing of water samples from Coffin Bay to Pt Drummond confirmed the presence of the algae Karenia mikimotoi, a naturally occurring algae known to cause fish kills around the world. This algae does not pose any human health issues.

Professor Mehdi Doroudi, Executive Director, PIRSA Fisheries and Aquaculture, says tests have also been conducted on abalone and oyster samples to rule out the presence of known infectious marine diseases, with test results negative.

“Blooms of this particular algae occur naturally when the right environmental conditions are favourable,” Professor Doroudi said.

“In this instance, dodge tides, high local water temperatures and the upwelling of nutrients from deeper waters, culminated in late February to make this particular algae increase in numbers, creating a bloom.

“This has resulted in localised deaths of species including abalone, cockles, rock lobster and fish around the reefs of Frenchman’s Bluff, Coffin Bay, with a small number of fish deaths now evident on the shore near Farm Beach, Coffin Bay.

“Testing of water and marine species occurred as soon as the bloom was reported. However, we have not had to close any areas or beaches as a result of the bloom because infectious disease and biotoxins are not present.

“PIRSA has been working closely with the fishing and aquaculture industry bodies to monitor the bloom’s density and movement.

“The algal bloom is not currently affecting oyster leases in Coffin Bay, however, if this situation changes, lease holders have the option to move their oysters to alternative lease areas.

“Growers are encouraged to speak with their South Australian Oyster Growers Association Bay Representative.”

Jill Coates, President of the South Australian Oyster Growers Association, said it was unusual for a bloom such as this to occur near Coffin Bay, and there hadn’t been one in the area for almost 20 years.

“We are hopeful that there will not be an impact on the oyster sector given that it appears the algae is tending to affect marine species on the sea floor, rather than surface species,” Ms Coates said.

“The industry will continue to work with PIRSA to monitor and evaluate the situation.”

While marine species are affected, the algal bloom poses no known human health issues, and worldwide there has been no reported human illness due to this particular algae. Recent test results from this event were negative for biotoxins.

SA Health advises that the species of algae involved in the bloom does not pose a human health risk, and as such live, healthy fish caught in the area are safe to consume.

However, people should not eat any fish found dead along the shoreline or in the water because of the normal risk of spoilage. Further advice is available from SA Health at www.health.sa.gov.au

People who find large scale fish deaths in the region are asked report to the Fishwatch 24-hour line on 1800 065 522. All reports received about fish mortalities are investigated.

algal bloom 

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