I love seaweed salad. But, not when it covers the mud and keeps critical oxygen from getting to the creatures that live beneath it – creatures like valuable shellfish. That’s what’s happening right now at Thomas Point Beach. Swaths of mud look bright green instead of the usual dark grey-brown. The culprit is a sea vegetable known as sea lettuce, or Ulva lactuca. The cause is the question – as is the solution.

Sea lettuce is not the most common sea vegetable. Most people are more familiar with rockweed, the floppy brown algae that grows on the rocks. Sea lettuce, by contrast is bright green and nearly translucent. It grows in broad leaves much like lettuce and has what looks like a small stem, also like that at the base of a lettuce leaf. But, in seaweed, this stem is known as a holdfast. This is designed to do exactly as its name suggests – attach to something and hold fast to it. It’s almost like a tiny round suction cup that helps hold it in place. Another difference is that sea lettuce grows in individual leaves rather than as a head of bunched leaves. These “leaves” can get quite large – seven inches long and 12 inches across, but they are usually much smaller. They appear papery thin when floating on water and look like they might be fragile. But, their tissues are composed of two layers, making sea lettuce tougher than it appears.

Sea lettuce, like any plant, thrives on nutrients. In addition to sunlight, they need things like nitrogen and phosphorus, both of which occur naturally in the marine environment. But, they also come from sources on land that can add to the naturally occurring amounts – sources like fertilizers that people put on their lawns or waste from domestic animals or farm fields. That’s why there is concern about the current “bloom” of sea lettuce occurring at Thomas Point Beach. It could be from naturally elevated levels, but it also could be from land-based sources that may be able to be identified and remedied. That’s what is being assessed now with the use of the town’s airboat and aerial drone.

That’s part one of the issue – why there is so much sea lettuce at that location right now. The other is what to do with it so that it doesn’t smother the clams living underneath it. There is some potential since sea lettuce is a delicious sea vegetable. You can eat it fresh in dishes like seaweed salad or some people dry it in sheets to use in sushi rolls. It also makes a tasty salt substitute and can be used to make a briny broth. Some people also pickle it, using vinegar and spices to keep it moist and crisp. It is also quite nutritious. It is predictably rich in iodine, but more surprisingly it also has iron, calcium, protein and fiber as well as Vitamins A, B and C.

That sounds like a tasty solution, but getting the lettuce off the mud isn’t simple. First off, it weighs a lot since it is wet. That’s tricky because it is currently on shallow, soft mud. It is also attached to shell, some of which is attached to newly set baby clams. So, it would have to be removed carefully so as not to disturb the animals living underneath it. Then, even though people have identified ways to eat it, there isn’t exactly a thriving sea lettuce market. Potentially, it could provide some additional income for shellfish harvesters, if a sustainable method could be identified.

Like all natural resources, there are complex factors that go into management. These determine the balance between the health of the resource as well as the ability for that resource to provide income. And, at the same time, the management has to take into account the natural and unnatural impacts that cause changes in the environment. For now, it is an opportunity to learn more about an interesting species and perhaps to give it a try. You can find it dried online through several local businesses. Check out the Maine Seaweed Council’s website (www.seaweedcouncil.org) for a list of companies.

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