Ocean acidification is an effect of having too much carbon dioxide. The other effect of too much carbon dioxide is global warming. Growing 180,000 square kilometres of sea lettuce (ulva lactuca) could be part of geoengineering a fix for too much CO2.
This idea, presented by Wageningen (UK) biologist Ronald Osinga, came as a surprise to delegates at the international coral symposium held in Wageningen last week. The symposium was an initiative by the International Society for Reef Studies (ISRS) and focused on the effects of climate change on coral reefs. Acidification of the oceans is one of the problems, and corals are highly sensitive to it. They become bleached and the calcium they contain dissolves.
But this does not have to happen, says marine biologist Osinga. On the closing day of the symposium he proposed a solution: sea lettuce (ulva lactuca). As it grows, this marine plant lowers the acidity of water. What is more, it is edible. Osinga and his colleagues have calculated that a ‘marine garden’ of 180,000 square kilometres could provide enough protein for the entire world population. A sea lettuce bed of such gigantic proportions would raise the pH (acidity level) of the Mediterranean Sea by one tenth. That may not seem much, but according to Osinga, it would be enough to compensate for the rise in acidity that started with the industrial revolution.
Linking the cultivation of sea lettuce with fish farming would create a closed food cycle, says Osinga. The waste products of the fish would nourish the sea lettuce. Osinga: ‘Offshore fish-farming is a massive polluter. It’s much better if you can recycle these nutrients. There is a lot of interest nowadays in this sort of integrated concept.’
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