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Getting to the Bottom of Algal Blooms:
Nuclear Methods Target Toxins

Bolinao, Philippines. Suddenly, in the early days of February 2002, milkfish started floating to the surface of the clouded ocean waters. Hundreds of tonnes of milkfish (locally known as bangus) valued at tens of US$ millions were dying in their cages and traps, and beginning to decompose en mass on local beaches. The coastal town of Bolinao in western Luzon—one of the principal sources of fresh seafood for Metro Manila—was rapidly turning from prosperity to an economic and environmental disaster area. The Bolinao Municipal Council declared the town under a state of emergency.
Dead fish resulting from algal bloom

A massive fish kill resulted from an algal bloom near the shores of Bolinao, a major fishing town on the west coast of Luzon.

“We knew that the heavy concentration of aquaculture in the area made it extremely vulnerable to an algal bloom at some point,” says Professor Rhodora Azanza of the Marine Science Institute of the University of the Philippines (UPMSI). “But the severity and magnitude of the fish kill was nearly unprecedented, and the nature of the phytoplankton bloom causing all the damage remained a mystery.”

It was critically important to find out. Some algal blooms are laden with a toxin that can concentrate in mussels, clams, and other shellfish and be lethal to consumers. Scientists call these varieties Harmful Algal Blooms (HABs). One health condition they can cause is paralytic shellfish poisoning (PSP), characterized by death from respiratory arrest. Dr. Azanza and her team at UPMSI went to work quickly analyzing water and shellfish samples in their laboratory in Quezon City. Within a few days, and thanks to a powerful microscope provided by the IAEA, they were able to inform the concerned public that a phytoplankton, Prorocentrum minimum, was the source of the bloom. While it had helped kill a lot of fish, it posed no danger of toxic effects on humans.

While that was good news to seafood consumers in the Philippines, the incident points to a much more extensive set of environmental problems that are not about to go away. With more than 7,000 islands spread across thousands of square kilometres of tropical seas, the Philippines is a fisherman’s wonderland—and an ideal location for aquaculture, the cultivation of seafood in artificial environments. Indeed, Philippine fisheries production surpassed the 3 million metric tonne mark in 2000, and aquaculture growth represented the most dynamic subsector surging at 10.6 per cent annually.

Researcher Iris Baula of the Marine Sciences Institute gathers water samples in Manila Bay using equipment supplied by the IAEA. The Institute is tracking the history of algal bloom incidences in the Bay in order to better forecast and prevent new occurrences.

But along with the growth of coastal aquaculture over the past two decades, the incidence of “red tides” like the one in Bolinao and toxic algal blooms causing PSP have been on a rapid rise. There are now 17 coastal areas across the country that are known to have been affected by an algal agent known as Pyrodinium bahamense var. compressum, and some 1,800 cases of PSP have been reported and over 110 deaths over the period.

The government agency in charge of tracking HABs is the Philippine Bureau of Fisheries and Aquatic Resources (BFAR), which has established monitoring stations across much of the country and a central laboratory to conduct toxic testing of water and shellfish. According to BFAR’s senior aquaculturist, Fe Bajarias, who now heads an inter-agency National Red Tide Task Force, “Our labs are constantly monitoring to ensure safety for the public. Due to potentially harmful algal blooms, we currently have placed three coastal areas under a complete shellfish harvesting ban. Our warning system is working, but our methods of testing and analysis would benefit from more advanced knowledge and testing technologies.”

BFAR’s shellfish testing laboratories rely on a tried and true—if slightly primitive—technique, injecting lab mice with the suspect shellfish toxin concentrate and measuring how long it takes for the mice to die. The “live mouse bioassay” method has been employed throughout the Asia-Pacific region for decades, even though its level of specificity in toxin determination is mediocre at best.

“The mouse bioassay is very imprecise, and the fishermen complain that harvesting bans are imposed even though their products are perfectly safe to consume,” explains Elvira Sombrito, chief of Chemistry Research at the Philippine Nuclear Research Institute (PNRI). “The Philippines has had more than half of all the HABs occurrences throughout the whole region in recent years. It’s clear that we need more thorough and accurate, and more humane means for determining which samples are safe and which are toxic to humans.”

Since 1997, an IAEA TC project has been working to transfer a more scientifically advanced and precise method—the receptor binding assay technology—to assist the government in evaluating shellfish toxins resulting from increasingly frequent toxic “red tides.”

Ms. Sombrito’s views are given even more credence by those of Elmeterio Hopio, President of the Paranague Fisherman’s cooperative on the southwestern shore of Manila Bay. Mr. Hopio’s cooperative of 81 boat owners is the biggest source of fresh mussels for Metro Manila consumers. “The testing and information from the government is not very good or reliable,” says Mr. Hopio. “Most of our members are very leery of their results. The United Nations could really help us if they would work with BFAR to make the shellfish testing more accurate and reliable.”

That’s precisely what the UPMSI has set out to do, in collaboration with PNRI, BFAR, and the IAEA TC programme.

“HABs is an environmental problem that has emerged rapidly with the growth of the aquaculture industry, and all indications are that it is only going to get more dramatic over time,” says UPMSI expert Rhodora Azanza. “We owe it to Philippine and overseas consumers to provide the most accurate evaluation of any safety hazards in our seafood products. Our eventual adoption of the receptor binding assay technique using a tritium labeled saxitoxin is the very best way to ensure that.”

PNRI and UPMSI have been making excellent progress in adopting the new method, and are already providing backup testing and analysis for the conventional laboratories operated by BFAR. “We’re still in the experimental phases of adopting this advanced approach,” says Professor Azanza. “But within a few years, we expect that the nuclear technique will assume the lead role in ensuring safety for the public.”

Improved testing can deliver immediate results in terms of reducing human poisonings and lingering consumer uncertainty after a major HAB incident. Obviously, it will take far more than just better technology to bring the Philippine aquaculture industry into a more sustainable balance. “Devastating incidents like the one in Bolinao can occur because local governments are charged with regulating their local economies and marine environment,” explains Sandra Arcamo, chief of fisheries resource management at BFAR. “We can provide the essential technical expertise, but it is up to the local authorities to properly implement the mandated environmental plans.”

Intensive media coverage of recent fish kills and a more focused policy dialogue at the national level are beginning to question some aquaculture production methods that are currently widespread—such as fish cages and traps in high concentrations combined with heavy inputs of artificial nutrients. Clearly more ecologically sound methods will need to be identified if coastal peoples of the Philippines are to make a living from the sea on a sustainable basis.

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Laboratories throughout Southeast Asia still rely on the “live mouse bioassay” to test for toxicity in shellfish. Alternative nuclear methods are more accurate and cheaper and will soon be adopted in the Region.

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