We examine several pieces of seaweed. Some have a root-like mass at the base of the stem. Dad calls this a holdfast, a very proper name! It attaches the plant to the rocky bottom. "So why are so many seaweeds washed ashore here?" I ask. Dad explains that violent storms and some plant-eating creatures like sea urchins, can loosen the holdfast.	It may look like a wad of roots, but the holdfast (photo left) doesn't absorb nutrients like the roots of a tree. Instead, every part of a marine plant is capable of taking in nutrients directly from the seawater that surrounds it
A stem, called a stipe, rises from the holdfast, and blades branch off from the stipe. Now we have the basic structure of most marine plants: holdfast, stipe, and blades.
	"Did you know," Dad tells me, "that the most important marine plants in the ocean are so small that we can't see them without a microscope?" We sit down on a dry rock and I learn about the phytoplankton. These tiny forms of algae float on and near the ocean’s surface, basking in sunlight that they need for photosynthesis. These tiny plants, like the diatoms, are sometimes called the “meadows of the sea.” They’re grazed upon by microscopic marine animals called zooplankton which are in turn eaten by larger forms of sea life, and so on up the “food ladder” to the final consumers (like sharks, tuna, seabirds and us!)
	Dad explains that the seaweeds visible all around us, like kelp, surf grass and encrusting seaweeds, are grazed upon by intertidal animals such as urchins (photo right), chitons, limpets, and nudibranchs. Seaweeds also create a cool moist place for crabs and other free-moving animals to find shelter during low tide. (photo below)
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