While walking the Oregon beaches, it is not uncommon to find several bull whip kelp that have washed up on the shore. The tangle of kelp becomes an oasis for tiny shore creatures which use it for shelter and feed upon it.
Bull whip kelp (Nereocystis luetkeana) is a fast growing type of seaweed that lives in shallow, cold oceans that are rich in nutrients. Kelp is a type of seaweed, which makes it an alga, not a plant. Algae absorb the water which they need as well as the suns energy directly through the tissues of all of its structures. Plants must rely on a complex delivery system, utilizing specialized structures (roots and leaves for water & nutrients, and leaves for energy from the sun) for collection.
Because of their immense size, the beds for these oversized brown algae are called kelp forests. The claims for maximum height range from 80′ to 200′. I suspect that the actual maximum height of bull whip kelp does not exceed 120′ even though it is the tallest of all kelp. My son and I found a specimen that was 75′ long. What makes the size of the kelp truly remarkable is that they grow as annuals, although some individuals do survive through a second year. So the kelp must reach these amazing heights in a short period of time.
One of the major structures making up the kelp is the holdfast which is a bundle of finger-like projections that keep the kelp anchored to the ocean floor. The stipe is a long gently tapering body which is little more than the width of a pencil at the holdfast. This stipe can stretch nearly to the surface of the water, where it is almost three inches thick. Topping off the stipe is a gas filled float. From this bulb, fronds or blades spread out across the surface of the ocean or reach up towards it.
Sea urchins can easily wipe out a kelp forest with their voracious appetites, but sea otters and some types of starfish prey upon the sea urchins, and can minimize the damage done by them.