Toxin in algal blooms sink to ocean floor to poison marine life

March 23rd, 2009 - 12:46 pm ICT by ANI  

London, March 23 (ANI): A new research has suggested that the toxin in algal blooms can sink to the ocean floor, where it persists for weeks, poisoning marine life.

According to a report in New Scientist, the research, by researchers from the University of South Carolina, suggests that far from degrading soon after the bloom, the neurotoxin that causes shellfish poisoning, domoic acid, sinks to the ocean floor and could poison marine mammals, birds and humans.

The first signs of an algal bloom are often birds washing up on the shore or seals acting funny, aggressive and twitching, looking as if they were drunk, said Claudia Benitez-Nelson of the University of South Carolina.

We used to think that once the bloom died, the danger was over, but now it turns out that domoic acid is a gift that just keeps on giving, she added.

Benitez-Nelsons team are the first to look for the chemical in algae particles sinking through the ocean, as well as in sediment samples on the ocean floor, up to 800 metres down.

They found copious amounts of the neurotoxin, reaching concentrations eight times the US federal limit for the substance in shellfish.

The team also compared the peak of domoic acid levels from the sediment with those of algae blooms at the surfaces.

Their findings indicate that the toxin reaches the bottom of the ocean in only three days but stays there for much longer at least several weeks.

The speedy trip to the bottom is probably driven by dead algae clumping together at the surface to form heavier aggregates, a process that also protects the toxin from degradation, according to the team.

Domoic acid gets broken down easily in water and by sunlight, but once the clumped algae are buried in the sediment, the toxin may stay protected until a bottom-dwelling organism eats it.

According to Raphael Kudela at the University of Santa Cruz in California, the new work is the missing link to explain why domoic acid also shows up in bottom-dwelling organisms like crabs and flatfish.

To Benitez-Nelson, the most important next step now is to work out in more detail how much longer the domoic acid sticks around and into how many more organisms it gets.

It is clearly a lot more prevalent and spread out than we thought before and this problem affects many areas, not just California. On top of this, all signs seem to point to further increases in the future as people dump more and more algae feeding nutrients into the ocean, she said. (ANI)

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