Durable bull kelp has remarkable cycle of reproduction, growth

The annual is the world's fastest growing plant (up to 2 feet a day) in a single season.

SHARON WOOTTON

Originally published October 9, 2001

After a hard paddle into an unusual north wind, we rested for a moment in a sheltered cove, protected from the foam-topped chop.

The double kayak drifted slowly. Behind me Jennifer Hahn, author of the recently released "Spirited Waters" and solo kayaker through the Inside Passage, was wielding her knife on a long strand of dark greenish-brown bull kelp.

Then a few musical notes drifted across the natural amphitheater of the cove for an audience of birds and mink.

Hahn knows someone who can play "Amazing Grace," but her three-note effort was enough to make me smile over another of nature's little surprises.

Rafts of bull kelp are drifting with the tides these days. Their death is an end to a remarkable cycle of growth and a surprising reproduction pattern.

Nereocystis leutkeana is a complex algae that thrives in Washington waters. It grows in rocky subtidal zones, reaching up to 80 feet or more of holdfast, stipe, bulb and fronds.

The annual is the world's fastest growing plant (up to 2 feet a day) in a single season. The kelp that you see in the summer is actually the grand offspring of the kelp you saw last year.

The asexual plant can produce trillions of spores from leaf sacs in late summer or early fall. Few survive to the microscopic plant stage, at which point they are male or female and produce sperm and eggs for winter fertilization.

It is their offspring that cling to a rock at a depth up to 60 feet with its holdfast. I've found beached kelp whose holdfast still clung to the rock to which it had been attached.

Out of the holdfast grows a single hollow stipe (stem) topped by a hollow bulb 4 to 6 inches in diameter. The tough, thick stipe, with its long air pocket and carbon-monoxide-filled bulb, float 32 to 64 blades in ribbonlike groups that can grow to 5 inches wide and a dozen or more feet long.

Locally, the leaves also are known as the tresses of Samish Indian princess Ko-kwal-alwoot.

The fronds act as solar panels, gathering the light, picking up nutrients in the water and manufacturing mineral-rich kelp food.

Kelp beds may have thousands of plants creating an underground forest with different stories sheltering and feeding juvenile fish, anemones and seas stars, chitons, crabs, snails and shrimp, sea cucumbers, sea squirts and sponges.

Urchins, kelp crab and nudibranches eat kelp. The red sea urchin has a huge appetite and has been known to clear-cut kelp forests.

Densely packed kelp beds provide a resting site for sea otters and birds. The groves also break some of the wave and current action that can be destructive to intertidal communities.

Eventually, death and storms will send the kelp afloat in tangled rafts. It's the most likely plant to make it to the beach because less-tough algae are destroyed by wave action and pounding surf.

Beached, they become home to beach hoppers (sand fleas), tiny crustaceans. At night the hoppers scavenge kelp or other plant material. Turn over the kelp and see them scatter.

Beach hoppers aren't the only creatures eating kelp or other algae. Seaweed is in ice cream and salad dressings. Dried kelp can be used to wrap sushi. Kelp powder has been used to replace salt in recipes and to prepare pharmaceutical supplies and glazing agents.

Pickle and eat the stipe of young kelp. Fresh is better. To tell, bend the stem like you would an asparagus stalk. If it bends like a licorice stick but doesn't snap, it's too old.

And if you're not that adventurous, you can always blow your kelp horn.

Sharon Wootton is a free-lance writer from the San Juan Islands. E-mail questions, suggestions or comments about nature, or Nature's Journal, to songandword@rockisland.com.

The Olympian Copyright 2001