These seaweeds need lots of sunlight and therefore are found near the water surface. A common green alga is sea lettuce or Ulva . It is thin and delicate and often found floating near the shore or washed up on the b each. It gets crispy when dried out, but regains its soft, leafy appearance when wet. Ulva is found throughout the world.
Brown algae can live in deeper water than green algae, but prefer cooler temperatures.
There are about 1500 species of brown algae, most of which are marine. Include d in this group are the wracks, rockweeds and kelps. The giant kelp off the California coast is the basis for a fascinating marine community. The area dominated by kelp is commonly called a kelp forest and provides food and shelter for a wide variety of animals. A more unique community is found off the east coast of the United States, wher e a free-floating brown alga called sargassum grows in abundance.