Bull Kelp
© 2007 Jan Holmes
Walking along the water at the Naval Air Station a couple of weeks ago, I was impressed by the big piles of bull kelp that littered the beach. The appearance of Nereocystis luetkeana makes it easy to understand how this brown alga has acquired such descriptive common names as bullwhip kelp, ribbon kelp, and bladder kelp.
You probably remember from Beach Watcher training that bull kelp has a float that contains carbon monoxide, that it has fingerlike projections on its holdfast called haptera, and that it is an annual that breaks loose from the substrate and washes ashore this time of year as a natural part of its life cycle.
You may not realize however, what an important part of our shoreline environment kelp is. Nereocystis is one of the large kelps that form kelp forests in water to about 60 feet deep. In the open ocean, the stipe can grow over 100 feet long but in Puget Sounds it is more likely to measure around 20 feet. Like eelgrass beds, kelp forests support many forms of life. Sea urchins and isopods feed directly on Nereocystis. Detritus from the blades slough off and support filter feeders such as mussels. One nudibranch, Triopha maculata, lays its eggs only on this alga or its cousin, the giant perennial kelp Macrocystis. Thick stands of Nereocystis slow water currents, allowing plankton to become more concentrated, thus making good feeding grounds for smaller critters. They in turn attract larger fish and invertebrates. This creates a rich hunting area for grebes, loons, goldeneyes and other sea ducks.
Bull kelp also has direct effects on our beaches. Water is slowed as it moves through the thick vegetation, softening the force of waves and thereby decreasing beach erosion. The big piles of bull kelp we've been seeing are important sources of food and cover for little beach critters.
Nereocystis luetkeana is another species that makes it easy to understand how closely everything in the Puget Sound environment is interwoven.
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