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Harmful algal blooms and associated biotoxins

In recent years, there has been an increase in the severity, frequency and geographical range of harmful algal blooms (HABs), which can produce biotoxins linked to mass mortalities in fish and birds and cause foodborne illnesses in humans through the consumption of contaminated seafood.  The IAEA assists Member States with the use of nuclear and isotopic techniques to monitor biotoxins in the environment and in seafood as well as to study historical trends in harmful algal blooms.

Phytoplankton are microscopic algae at the base of the marine food chain. Most of them sustain life by providing a vital source of nutrients for marine organisms and produce more than half the earth’s oxygen supply. However, factors such as coastal upwelling or agricultural run-off can increase nutrient levels in water and can cause algal blooms, which in some cases can be toxic. Each year, these harmful algal blooms (HABs), also known as red tides, are responsible for thousands of poisoning incidents all over the globe due to the consumption of contaminated seafood. Symptoms include vomiting, diarrhoea, dizziness or, in extreme cases, even death as well as respiratory issues in people who breathe in toxic aerosols.

Developing detection methods for biotoxins

The IAEA Environment Laboratories use nuclear and isotopic techniques to gain a better understanding of HABs and to develop Member States’ capacity to detect and monitor marine biotoxins in seafood and in the marine environment. IAEA researchers train Member States on the use of the radioligand receptor binding assay (RBA), a nuclear tool used to determine quickly and precisely the presence of biotoxins such as saxitoxins, ciguatoxins or brevetoxins.

The RBA works by mixing a sample containing toxin receptors with a radiolabelled toxin and a membrane preparation. If the seafood is contaminated, the radioactive toxin is displaced from the receptor. By measuring the amounts of radioactivity left in the sample, scientists can determine the exact levels of toxins. Several successful applications have taken place in El Salvador, Morocco, Tunisia and the Philippines, among other places. In addition, researchers develop new analytical methods to measure biotoxins and study how they are taken up by marine organisms and transferred up the food chain.

Such tools could be used by Member States as part of regulatory monitoring activities to determine the presence of HABs and associated biotoxins in coastal waters and in seafood and contribute to more robust seafood safety programmes.

Impact of harmful algal blooms on coastal populations

Harmful algal blooms outbreaks can have a big impact on local economies and lead to the closure of fisheries, aquaculture and recreational areas, the loss of fishery products, with subsequent declines in  businesses, tourism, and associated services. In addition,  regulations issued to deal with harmful algal blooms often involve the banning of selected species of certain sizes. Effective emergency systems can help minimize risks and avoid unnecessary closures thanks to the use of nuclear techniques that quickly identify biotoxins in seafood and in the environment and pinpoint outbreaks more accurately.


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