Growing seaweed can solve acidification

Large-scale cultivation of sea lettuce can help reduce acidification of the oceans. And help solve the global food supply problem to boot.

This idea, presented by Wageningen 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 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.'

Osinga and his University of Amsterdam colleague Jaap Kaandorp brought the symposium to Wageningen in order to draw attention to Dutch coral research. Wageningen UR plays a modest role in this research, but that may be about to change through the accession of the 'BES' islands (Bonaire, St. Eustatius and Saba) in the Caribbean to the Netherlands. But that is a separate issue, says Osinga, and not the reason for the symposium. 'It's a coincidence. But a useful one, with all the attention to the around the BES islands.' Three hundred scientists from all over the world took part in the symposium.

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Dec 23, 2010
That's roughly 425km * 425km.

That's around 30% more area than the entire state of Louisiana...

That's a pretty large operation and would require many ten thousand workers. Also, you'd need offshore solar power platforms to be able to power the boats and other machinery to grow, maintain, and harvest these farms.

Don't mention this to FBM, because he thinks projects like this are "impossible".

I think this is possible and will even become necessary as we build floating cities and solar fuel depots in the middle of the oceans, etc.

Dec 23, 2010
If they plant it, I'll eat it--so long as toxic runoff and dumping is curtailed. Nothing we do to help the ocean will help a thing until we get that toxic waste in the sea under control.

I think that this is a wonderful plan to raise pH, and to think that this approach likely will not do more harm to the planet than the problem perceived as needing to be solved. This is far better by far than the toxic iron idea and could be used to add to the economy in addition.

Dec 23, 2010
Sure, it's the size of Louisiana, but it's "arable farmland" we aren't currently using. Unlike ethanol, it doesn't remove farmland from food processing. Fish and greens, call it Soylent.

Dec 23, 2010
Reforestation of the sea. We do it on land and it works, so why not? I certainly think ocean conservation as it is is severely lacking.

Dec 23, 2010
Seaweed's pretty tasty if you prepare it right. I doubt this would be one 425km square farm, though. Maybe dozens of smaller ones scattered across the globe.

I'm interested in what other effects this may have. Large surge in sea urchins? Attracting other predators? I imagine the practical implementation is far more difficult than many think, but it's still an interesting idea worth exploring.

Jan 02, 2011
This is an interesting idea but there are two main problem how do you provide the nutrients needed to grow the sea lettuce and the second is how do you keep predators off of your crop? The Tidal Irrigation and Electrical System could be the answer. It uses the tide to suck up nutrient rich water from deep in the ocean into a lagoon where a controlled aquaculture like the one called for in the article can take place.

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