The Sounds of Seaweed Synthesizing


At a shallow depth, in ‘Aquarium’, a thicket of coral seaweed.

A recent NIW study has shown how gas bubbles released by seaweeds during photosynthesis produce sounds which correlate to the amount of oxygen they release.

Dr Giacomo Giorli, a marine acoustician, is one of the authors of a recently published scientific paper that identified these sounds.

He said: “Declining algal cover is one of the major indicators of stress in coral reef ecosystems. Our observation suggests that monitoring the sounds generated by algal photosynthesis could potentially be used to estimate the amount of algal cover and ecosystem health in coral reefs.“

Dr Giorli’s and his colleagues’ research at The Hawaii Institute of Marine Biology involved collecting a large amount of the algae Gracilaria salicornia and placing it in an experimental tank equipped with an aquarium light. The algae were exposed to cycles of dark and light and a hydrophone was used to measure the sound in the tank while a high-resolution video camera recorded the bubbles and measured their size.

The sounds comes from the tiny movements of the bubbles as they form a spherical shape in the water. During release, relaxation of the bubble to a spherical shape creates a sound source that ‘rings’, the scientists found.

“The bigger the bubble, the lower the sound. The whole process was reversed when we turned the light off.”

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