There are two kinds of common green seaweed in the photograph.
Floating above the wide green blades of sea lettuce, which was discussed in a previous column, is another green algae called the green string lettuce. It consists of narrow hollow tubes made up of a single cell layer. The color ranges from white to yellow to green. The white color is due to bleaching of the blades at the water surface. Bubbles of oxygen within the tube formed from photosynthesis in the algae is causing the blades to float.
This plant grows in a wide range of conditions from very low salinity conditions to highly saline pools found at the extreme high tide level. Because of its tolerance of freshwater it can be used as an indicator of shoreline seeps caused by groundwater or leaking septic tanks.
It is found around the world in the mid to high intertidal zone. It ranges on the Pacific coast of North America from Alaska to Mexico.
Green string lettuce is eaten in Asia. Nutritionally it contains about 20 percent protein and is low in fat and sodium while high in iron and calcium. Its vitamin B content is generally higher than most vegetables. The vitamin A is high, but it is only half of that found in spinach.