How the sea can toss a salad for manatees — and for us

Those slimy, crumpled, bright green masses of seaweed you may have noticed at the beach are called, appropriately, sea lettuce (Ulva).

Ten species occur around the world — free-floating in tide pools, attached to rocks and pilings, and often washed up onto the shore.

Sea lettuce is food for a variety of marine animals, including manatees, sea slugs, sea urchins, and tiny crustaceans called amphipods.

But sometimes unusually dense populations of sea lettuce make beaches inhospitable for swimmers and beach walkers, as has happened notably in France, England, and Ireland, as well as along both coasts of the U.S.

Seaweed “blooms” can shelter a variety of small marine invertebrates, but they also block light from reaching submerged plants below.

And washed-up piles of the seaweed may blanket shorelines and release a strong, sulfurous odor as they decompose.

Since sea lettuce can tolerate heavy sewage runoff, blooms in some areas may indicate high levels of nitrates and phosphates in the water.

Despite being a nuisance at times, the seaweed has been harvested for use as a fertilizer and mulch.

Sea lettuce also has a long history of culinary use in Japan, China, Scotland, Ireland, Scandinavia, and other parts of the world.

It can be eaten raw in salads and cooked in soups. Sometimes it’s dried and powdered, then added to depart a well, maritime flavor to various dishes. Soaking and then blanching it first may make it more palatable.

Nutritional analyses show that sea lettuce is relatively high in protein, minerals, vitamins, and dietary fiber. It’s low in fat.

If you’re tempted to try sea lettuce in your own kitchen, be sure you identify it correctly and gather it from pollution-free waters, since in some places it can be contaminated with heavy metals or other pollutants.

This story was originally published May 4, 2017 at 6:13 AM with the headline "How the sea can toss a salad for manatees — and for us."