DESALT DA SEA LETTUCE
Sea Lettuce - Ulva
Copyright © 2006 Jan Holmes
Roaming beaches, one often notes a bright green, translucent alga with a most appropriate common name: Sea Lettuce - known to those more scientifically inclined by its genus names Ulva and Ulvaria.
Found on rocks, shells, pieces of wood and such at lower tide levels, the often torn from same and the substratum and then pushed up the beach slope by inclining waves, Sea Lettuce leaves (called blades technically), and other adrift seaweeds, are deposited on the beach as the seawater retreats. The left-behind fresh Sea Lettuce indeed do somewhat resemble store purchased or home-grown lettuce, but seem thinner, more fragile, more see-throughish. On the beach it’s more like over-ripe, discardable, still fairly green, table lettuce that can be overlooked and begin breaking down in the vegetable drawers of our refrigerators.
Its look of fragility can be quite misleading, however, because the detached Sea Lettuce can continue to photosynthesize - live on - as a free-water-floater. It is, in reality, hardier than some far larger algal marine life - although it reportedly is unable to withstand moderate to strong wave action. Any fragility manifested may be attributed to the fact that microscopic examination of thin slices of the lettuces’ thin wide fronds has established that they are a mere one or two cells thick, depending on their genus and species. Some Sea Lettuce leaves appear as sheets, some as sheets perforated with holes, some as raggedy edged or ruffled sheets, others adhering to one another – little more than globs of green.
Writer/photographer, Anne Wertheim* describes Ulva as “essentially a two layered sheet of photosynthetic tissue”. She further informs us that these sheet forms are very efficient and productive as they present large surfaces to the sun’s rays, thus maximizing photosynthetic areas. She also states that Ulva “is the commonest form (of algae) in the intertidal”. One reason they are found from the Bering Sea to Chile is that they are tolerant of a wide range of temperatures. And when fertile conditions prevail, the leaves can cover large areas.
Sea Lettuce and its relatives are adapted to utilize the more intense sunlight of intertidal water - water not too deep. Hence, we at times will see lettuce blades out of the water on intertidal rocks in bright sunlight where they may appear quite dried out. Good chance, though, if we returned later at a higher tide when liquid-bathed again, the leaves would have soaked up Puget Sound fluid and be just fine. But as the sun beats down on detached, more permanently beached Sea Lettuce, and prolonged drying occurs, it will become rather crinkly-looking and crisp – and will feel more like gift wrapping tissue paper than seaweed. Eventually the stranded lettuce will bleach until quite colorless.
Only one of some 600 species of seaweed in Puget Sound, and a member of a group that makes up at least half of all living matter on earth, Sea Lettuce and other seaweeds are right down there at the base of the Sound’s food web - a web which supports all marine life and determines the health of all Sound species. They are a most important food source to many forms of sea life. They, as we know, also take carbon dioxide from the water and give off oxygen as a waste product which fish and other organisms absorb. Supplying places for critters to attach to, hide in and reproduce in are other roles Sea Lettuce and other seaweeds effectuate.
So marine plants such as Sea Lettuce are more than at times wet and slimy stuff whose consistency has been compared to wet wax paper - contributing to piles of beach debris we see and occasionally carelessly slip on when walking beaches. Critical to the offshore/shoreline environment? You bet!!
Most beach walkers and visitors will be totally uninterested in carrying a dab home to spike their luncheon salad; however, Sea Lettuce is edible as well. It is rich in protein, in vitamins such as C, and elements such as iron and iodine. Traditionally Hawaiians utilized it as foodstuff in a variety of ways - mixed with other seaweeds to serve with sushi, made into a light soup, and mixed into stews. Native Americans also used it as foodstuff.
Seaweeds taste more primo when harvested early in the spring growing season far away from possible pollutants. They can then be integrated into recipes either fresh or dried. Harvested Ulva blades should be completely grass green in color. Merely rinse them in fresh water to remove the strong salty taste and - Voila! - it’s ready to mix into a salad or whatever - a fine addition and enhancement to a meal. Bon appetit!
Pat Nash, Beach Watcher, Class of 1994*Anne Wertheim Rosenfled, The Intertidal Wilderness, University of California Press, revised March 2002, ISBN: 0520217055