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Nuclear Techniques Help to Detect Harmful Algal Blooms

Red tides, more correctly known as the Harmful Algal Blooms (HABs), are one of the most serious periodically occurring events facing marine coastal areas. Outbreaks of algal blooms result from an increase in nutrient levels in the water, induced by coastal upwelling and agricultural runoffs.  HABs are an accumulation of algae that produce natural toxins, which collect in shellfish. This results in contaminated seafood entering the food chain and affecting not only on the marine ecosystem, but also human health. HABs are also a major threat to fishermen's livelihoods: the red tides can cause massive fish kills and therefore, significantly affect local and commercial fisheries. In addition, the closure of fishing grounds due to HAB events creates considerable financial hardship for fishermen.

Although HABs can sometimes look like a massive, coloured patch of water approaching the shore,  most of the time it is rather difficult to see the blooms with the naked eye. This increases the risk of contaminated sea products entering the human food chain.

Nuclear technology can be used to identify HABs early, and to pinpoint outbreaks with more accuracy. This protects the food chain, and helps to limit the amount of time that fishing grounds must be closed. Through its technical cooperation (TC) programme, the IAEA is helping countries use nuclear technology to identify HABs events, and to limit their impact.

Several TC projects are focusing on the development of early warning systems for HABs, with the goal of minimizing the damage they cause. Nuclear techniques such as receptor-binding assay (RBA), used in combination with other methods, allow the concentration of toxins in seawater and in marine products to be measured quickly and efficiently. In addition, the nuclear approach provides a faster and more precise detection of toxins than the conventional mouse bioassay method. This faster, more accurate procedure helps to prevent contaminated products from entering the local food market and reduces the risk of intoxication through the ingestion of contaminated seafood.

Case Study - El Salvador

El Salvador has suffered greatly from HABs occurrences in its coastal waters. Red tides have caused, for example, deaths of fishes and marine turtles, as well as considerable financial losses. In addition, the ingestion of intoxicated food has led to severe consequences for human health and in some cases even death.  HABs can cause considerable damage to El Salvador's economy, as 30 per cent of the population lives in coastal areas and the livelihood of 27 000 coastal dwellers depends on the fishing industry.

To deal with HABs emergencies and contribute to the sustainable management of fisheries and marine products, the IAEA has helped El Salvador to establish a permanent monitoring system that provides early warnings of marine toxins in microalgae and seafood products. To support these initiatives and help fishing communities benefit from nuclear technologies, the IAEA provides training in the use of specialized detection equipment that is used to monitor Harmful Algal Blooms. In addition, a marine toxin laboratory (LABTOX-UES) has been established and equipped at the University of El Salvador to facilitate HABs related work.

The laboratory has developed an online information system (http://toxinasmarinas.cimat.ues.edu.sv) as a primary mechanism to support early warning of red tides. This information system provides data on physicochemical parameters of phytoplankton in the coastal zone of El Salvador. The data is used to identify critical algae outbreaks and thereby to avert the negative impact of HABs on human beings.

El Salvador's marine toxin laboratory is unique in Central America because of its capacity to measure the toxin content of HABs - an ability that no other laboratory in the region has yet developed. The facility is therefore, invaluable to the region. During a red tide incident in 2010 it was used to measure the toxin levels in HABs, which allowed pre-warning to the locals of the contamination in the waters.

To consolidate the early warning system, a complementary TC project at LABOTOX-UES is supporting the  monitoring of other elements in the water that could trigger the emergence of HABs, such as organic compounds,  heavy metals contamination, sewage and agro-industry discharges.

Effects of HABs

Effect on human health

Consuming marine organisms that have fed on toxic algae may cause serious health problems. Among the worst consequences are different types of shellfish poisoning (see chart for details). These can be the result of ingesting any type of shellfish, such as mussels, oysters or scallops, with an accumulated toxin concentration. The symptoms vary from nausea to memory loss, brain damage and paralysis. In the worst cases, the toxin concentration can be lethal.

n addition, inhaling toxins produced by algae may cause allergic reactions, and contact with bare skin can result in severe rashes and redness.

Effect on the marine ecosystem

Algae are an important source of nutrition for oceanic life, placed at the base of the food cycle. The occurence of HABs in coastal areas disrupts the marine food-web, causing the intoxication, stranding and death of many marine mammals, birds and turtles.

Effect on the economy

HABs events that lead to the closure of aquaculture and recreational areas cause grave economic losses. These include a severe decline in fishery-related business, tourism activities and associated services. The effect is reflected in increased unemployment and insurance rates as well as in higher prices for marine products.  Moreover, public illness and medical treatment result in the loss of millions of dollars per outbreak.



The accurate identification of oceanographic events such as Harmful Algal Blooms is important to a country's economy, food security and public health. With the help of the IAEA, Member States can improve their monitoring of HABs and develop capabilities for the early detection of toxins in seafood. With an effective emergency system, it is possible to minimize the risks HABs pose to the marine ecosystem, human health and economic stability. To date, 20 countries, including El Salvador, have received technical assistance from the IAEA on HABs related problems.


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