Scientists at the University of Hull, UK, think they have found a way to put a stop to red tide by exposing them to blasts of ultrasound. Michiel Postema and his colleagues tested three different frequencies on a particularly harmful species of blue-green algae, Anabaena sphaerica, which can cause respiratory disease and liver cancer in humans who come into contact with it. Although all three frequencies worked to some extent, the most effective was close to 1 megahertz. That value matches the expected resonant frequency of this alga's buoyancy cell, which is about 6 micrometres across (Applied Acoustics, DOI: 10.1016/j.apacoust.2009.02.003)."
"These high frequencies are absorbed rapidly as they travel through water, and at 1 megahertz the effective radius is less than 20 metres, says Postema. So the technique may be more practical for clearing algal blooms in lakes and ponds than for large-scale red tides that can cover hundreds of square kilometres of sea."
"These high frequencies are absorbed rapidly as they travel through water, and at 1 megahertz the effective radius is less than 20 metres, says Postema. So the technique may be more practical for clearing algal blooms in lakes and ponds than for large-scale red tides that can cover hundreds of square kilometres of sea."
