Mussels, better known as ‘‘tahong,” are a tasty treat
that may turn deadly in times of Red Tide.
Using ball clay, method removes up to 99% of deadly algae.
Jeff Smith, the original celebrity chef once said, “Do not overcook this dish. Most seafoods...should be simply threatened with heat and then celebrated with joy.” With a recent discovery by scientists at the UP Diliman Marine Science Institute (MSI), the adage might just ring truer.
Mussels, better known as ‘‘tahong,” are a tasty treat
that may turn deadly in times of Red Tide.
A team composed of MSI faculty members Dr. Maria Lourdes San Diego-McGlone, and Dr. Rhodora Azanza, with corresponding author Larry Padilla, recently found a way to use ball clay to remove as much as 99-percent of Pyrodinium bahamense, one of the species of algae native to the Pacific Ocean that has been known to produce toxins that cause Paralytic Shellfish Poisoning (PSP).
Tiny amounts of such algae are naturally present in seawater, but under certain conditions and at certain times of the year, these populations sometimes start to increase dramatically, and lead
to harmful algal blooms, which can form dense, visible colored patches on the water surface, leading to the term “Red Tide.”
P. bahamense is one of the more common species known to cause Red Tide.
In the article “Preliminary Results on the Use of Clay to Control Pyrodinium bloom - A Mitigation Strategy” published in the January-June 2006 issue of Science Diliman, one of the University’s refereed semi-annual journals, the MSI team reported the results of a study seeking to find a better, less hazardous method of controlling large algae populations by using locally sourced materials such as ball clay, brown bentonite and Malampaya sediment. Each material was prepared as a slurry and then individually added to seawater samples inoculated with P. bahamense.
The results showed that among the three materials tested, ball clay was found to be the most efficient, with a highest recorded removal efficiency of 99.9 percent. The other materials tested fared less, with highest recorded removal efficiencies of 69.3 percent and 48.4 percent, respectively.
“Although the method is not new, this is the first attempt to control blooms of P. bahamense,” according to their report.
Besides dramatically reducing the number of harmful algae in the samples, addition of ball clay showed no significant changes in seawater chemistry.
Symptoms of PSP can begin to appear within 30 minutes to two hours from eating the harmful seafood (which do not disappear even after cooking), and in lethal doses, can lead to death within two to 24 hours. The first shellfish poisoning was in 1983 in Western Samar and Leyte and resulted in losses to the mussel industry as well as poisoning among the locals.
Chemicals have been used to control numbers of harmful algal blooms in the past, but these sometimes have a negative effect on the marine ecosystem.
In February, Red Tide forced health authorities in Mindanao to ban the catching of crabs and shellfish for food in Zamboanga del Sur.
A 1992 outbreak in Manila Bay cost over 38,000 municipal fishermen some four months of livelihood.
---Anna Regidor