Seaweed farming and its surprising benefits (text and video)

Seaweed may be thought of as a nuisance, but an increasing number of fishermen, scientists and consumers are seeing it as a solution

Many of us think of seaweed as a nuisance — the slimy, sometimes smelly stuff that clogs fishermen’s nets, gets tangled in our ankles in the ocean, and washes up unwanted on the beach. Even its name — sea-weed — implies something undesirable.

And yet increasing numbers of fishermen, scientists, and foodies in this country are starting to look at seaweed very differently — as a promising source of food, jobs and help cleaning ocean waters. With rising global populations and limited space to expand agriculture on land, they are turning to the sea — and its “weeds” — as a new frontier.

How seaweed can save the environment

But at this kelp farm across the country in the waters outside Seattle, producing food is almost beside the point. This is a test farm, where Betsy Peabody of the Puget Sound Restoration Fund and a team of scientists are doing an experiment to see whether seaweed can help fight the growing problem of ocean acidification — caused mainly by increasing carbon dioxide levels in the seas.

Betsy Peabody: Roughly 25% of CO2 in the atmosphere is being absorbed into oceans.

Lesley Stahl: And that is what we’re getting from fossil fuels?

Betsy Peabody: From both carbon emissions, from deforestation, and I think initially people thought, “Well, thank goodness the oceans are taking up some of that carbon dioxide.” But then, scientists started to document that, in fact, when that carbon dioxide goes into the ocean, it causes chemical changes.

Changes like increasing the water’s acidity, as documented in the U.S. government’s 2017 climate science special report. The excess CO2 causes “a decrease of carbonate ions… Which many marine species use to build their shells and skeletons.” Worldwide, “ocean surface waters have become 30% more acidic over the last 150 years.” And in the Pacific Northwest, the problem is compounded by currents that bring more carbon-rich waters to the surface. And that’s where seaweed comes in.

Dr. Charlie Yarish: Kelp take up carbon dioxide like any plant does, and it just so happens it lives in the water. There are winners and losers in ocean acidification. Organisms that produce carbonate shells like shellfish, they’re a loser. They can’t handle the lower PH. They can’t deposit as much calcium in their shells. On the other hand, when seaweeds like kelp, they actually pick up that carbon dioxide because now it’s easier for them to do photosynthesis.

Betsy Peabody: Imagine trees on land, pulling CO2 out of the atmosphere. Well, seaweeds and kelp are really good at pulling CO2 out of the water.

Lesley Stahl: So basically what you’re doing is the equivalent of planting trees in the ocean?

Betsy Peabody: Exactly.

And then testing to see how much of a difference it makes.

Betsy Peabody: We’ve got scientific mooring buoys anchored at both sides.

Lesley Stahl: The yellow.

Betsy Peabody: The yellow buoys.

They’re measuring how water changes as it flows through the kelp field, and seeing if baby shellfish grown with the kelp do better at building their shells. Results won’t be in for more than a year, and Bren Smith is eager to see them. He’s been growing shellfish on his kelp farm too — but not, he admits, because of the science.  He says, it’s good business. In November, he and his team loaded thousands of baby mussels into netting that looked like massive sausages, then suspended them from ropes that hang down below the kelp. He calls it 3D ocean farming.

Lesley Stahl: Why 3D?

Bren Smith: We call it that because we’re using the entire water column. And if you can stack crops on top of each other it’s just really efficient. You don’t use large, you know, plots of ocean. But you get so much food.

Lesley Stahl: So you’ve got your seaweed.

Bren Smith: Yup. You’ve got the kelp here. And then we have the mussels.

Underwater, each row looks something like this.

Bren Smith: Off those same lines we have scallops. And then below the whole system we have cages with oysters in them.

He brought up one of those oyster cages from the bottom to show us.

Lesley Stahl: What kind are these?

Bren Smith: We call these Thimble Island salts.

Bren Smith: Let’s haul some mussels.

And he hauled up a mussel line so we could see their progress too.

Lesley Stahl: They’re in bunches.

Bren Smith: These are about mid-size. So they’ll double in size and we’ll harvest these just about the same time we harvest our kelp. So this is gonna be a big harvest

later on.

Lesley Stahl, 29 April 2018. CBS News. Article and video.

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Ocean acidification in the IPCC AR5 WG II

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