Coastal and Marine Pollution
Sustained pollution can damage coastal and marine ecosystems and jeopardise the livelihood of entire communities. By applying cutting-edge nuclear and isotopic techniques, the IAEA helps Member States accurately monitor pollution, minimise the impact of incidents and mitigate their effect on local populations.
It is estimated that 80 per cent of pollutants in the marine environment originate from land. Some of the hazardous substances, such as toxic heavy metals, persistent organic compounds (including pesticides and industrial chemicals), hydrocarbons and radioactive substances released from industrial, agricultural, municipal and mining activities ultimately enter the marine environment through surface water and groundwater.
To assist Member States in addressing coastal and marine pollution, the IAEA has developed a number of science-based tools and techniques that help decision-makers protect the marine environment. The Agency maintains environment laboratories in Monaco and Seibersdorf, Austria, that use nuclear and isotopic techniques to study pollution processes and fingerprint pollutants’ sources.
Coastal pollution and seafood safety
Contaminants that end up in coastal waters may accumulate in marine organisms through the food chain, degrading an ecosystem’s resilience and threatening human health through the consumption of contaminated seafood. In recent years, there has also been an increase in the occurrences of harmful algal blooms, which can produce toxins that cause foodborne illnesses such as the deadly paralytic shellfish poisoning and ciguatera fish poisoning disease. These incidents impact fisheries, aquaculture, tourism and the use of drinking and recreational waters.
Through its environment laboratories, the IAEA plays a key role in research and training on how to monitor hazardous contaminants and biotoxins in seafood, through for example the use of the radio-ligand receptor binding assay, an analytic procedure used to detect toxins during harmful algal blooms. Similarly, as part of a partnership with the Regional Organization for the Protection of the Marine Environment, one of the United Nations Environment Programme’s regional seas programmes, the IAEA’s Monaco-based Environment Laboratories analysed oyster and marine sediment samples from the Persian Gulf to determine levels of radionuclides, trace elements, organic contaminants and biotoxins related to harmful algal blooms.
Plastics
Some plastics accumulate in the oceans because of their slow degradation rates. Some estimates place as many as 5.25 trillion plastic particles weighing a total of 250,000 tons floating in the world’s oceans, including micro-plastics (plastics smaller than 5mm). They originate from the weathering and disintegration of larger plastic debris, from pellets used in the manufacturing of plastics, from additives in cleaning and personal care products, and from synthetic clothing.
Due to their small size, micro-plastics can be mistaken for plankton and ingested by marine animals, including bivalves (mussels, clams) and fish. Together with the pollutants that have accumulated on them, they can be transferred through the food chain. Radiolabelled tracers can help understand how microplastics get contaminated by organic pollutants and how they transfer such contaminants to marine organisms.
Similarly, the study of natural archives such as sediment cores, corals and shells reveals the history of pollution incidents in marine ecosystems. The IAEA’s Radiometrics Laboratory uses for example lead-210 and caesium-137 based geochronologies to reconstruct a record of environmental changes recorded in sediment and coral cores. This approach helps evaluate contamination accumulation rates in coastal and marine ecosystems.
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.
Plastics
As many as 5.25 trillion plastic particles weighing 250,000 tons are floating in the oceans, according to recent estimates. This presents a serious environmental challenge: in addition to chemicals in the plastics themselves, pollutants already dissolved in seawater can adsorb, or latch onto, these plastic fragments. These can be eaten by marine animals which mistake them for food and can pose a threat to seafood safety.
The IAEA uses nuclear and isotopic techniques to gain a better understanding of the effect microplastics have on organisms and to evaluate any additional contamination risks from associated pollutants. This includes the use of radiolabelled tracers in controlled aquaria to examine to what extent plastics can be further contaminated and transferred through the marine environment and up the food chain.
Plastics accumulate in the oceans because of their slow degradation rates. Micro-plastics, plastics smaller than 5mm, originate from the weathering and disintegration of larger plastic debris, from pellets used in the manufacturing of plastics, from additives in cleaning and personal care products, and from synthetic clothing.
Due to their small size, microplastics may also enter internal organs, where they could potentially be vectors for the transfer of contaminants attached to them. These could include persistent organic pollutants like polychlorinated biphenyls (PCBs) as well as trace elements like mercury and lead. Plastics and any pollutants which accumulate on them, can enter the food chain and be transferred to humans through the consumption of seafood.
To help evaluate risks and strengthen seafood safety programmes, IAEA experts are conducting research using nuclear and isotopic techniques under controlled laboratory conditions to precisely quantify the movement, fate and impact of plastic particles and associated organic and inorganic contaminants on a range of aquatic biota such as fish and oysters. By using tracers such as carbon-13, and carbon-14, IAEA researchers can study how pollutants such as PCBs ‘attach’ themselves to microplastics in the environment and if they can dissociate or ‘detach’ from these plastics when ingested by marine animals.
IAEA researchers will also use tracers to study the movement and fate of microplastics within the animals to understand how they are taken up — whether via the digestive system or through gills depending on the organism as well as whether they can be eliminated or if they clog different organs. If plastics accumulate in the gut, for example, organisms could get a false sense of being full, which can negatively influence their nutrient intake.
This information will advance our understanding of the role of microplastics and associated contaminants in societally and commercially important marine organisms and help strengthen Member State seafood safety programmes. Understanding to what extent microplastics can transfer hazardous contaminants to marine biota is an issue of global concern, in particular for countries that rely on fisheries as a source of food and income.
