LEGAZPI CITY, Philippines – Volcanic ash might be a big problem during eruptions, but a scientist says it can help minimize a different problem – red tide.
The Philippines’ fishing grounds is in dismal situation, as high levels of chemical contamination and harmful algae now affect almost all major fishing grounds in the country, says marine scientist Ronnel Dioneda, the director of the Bicol University Research and Development Center–Higher Education Regional Research Center
Dioned said that an increasing number of fishing grounds in the country is becoming more toxic, with the spread becoming more frequent and intense.
“More fishing grounds in the country are contaminated with chemicals [increasing the] toxicity of oceans… The serious threat is to human health, decimating aquaculture, and… to tourism too,” he said.
Dioneda said harmful algal bloom (HAB), known as the “red tide” toxin, is now affecting fishing grounds across the country. He cited the case of Sorsogon Bay when the red tide toxin was in bloom from September 2006 to July 2011. In this incident, contaminated shellfish caused the deaths of 20 people and the hospitalization of more than 300 others.
The dinoflagellate toxin is dangerous to public health, and it affects the livelihood of people who are dependent on shellfish, the marine scientist said.
In Sorsogon, the presence of red tide was temporarily contained after volcanic ash spewed by Mayon and Bulusan volcanoes flowed down to Sorsogon Bay.
Dioneda, who conducted a series of studies in Sorsogon Bay and other red tide-affected waters in Bicol, said the ash – rich in sulphur, silica and iron – indirectly helped curtail the toxin as these minerals encourage the proliferation of diatoms, microscopic algae that prevent the growth of dinoflagellates, which produce the red tide toxin.
He explained that diatoms are plankton that control the prevalence of the red tide agents. The diatoms, according to him, appear to benefit from the silica and other minerals more than the HAB-causing dinoflagellates. With an abundance of diatoms, the poisonous group of microorganisms are prevented from multiplying.
He explained that the cysts of dinoflagellates lay dormant on the ocean floor or buried on the sediment and left undisturbed and they can stay in this state for years.
Dioneda uncovered that there are rivers from Mayon Volcano in Albay that traverse Donsol and Pilar towns down to Sorsogon Bay, where a considerable amount of silica can be traced in the mouth of Sorsogon Bay.
“Volcanic materials, once dissolved in sea water, kills the cell with high density of toxicity,” he said. He said the decline in the red tide-producing microorganisms was noted after Bulusan spewed ash in 2011.
“Somehow, the volcanoes eruptions (Mayon and Bulusan) also help out to bring back the livelihood of the people specifically for tahong mussels’ dependent source of living,” he added. – Rappler.com
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