'You won't find [giant kelp] everywhere, for a couple of reasons," says Bruce Stewart, director of programs and exhibits for the Birch Aquarium at Scripps. "One, it needs to be in the right depth, commonly between 25 and 75 feet. It can't be too deep, say, over 100 feet, because it won't get enough sunlight, and if it's too shallow, it will bear the brunt of the waves." On Saturday, November 18, the Birch Aquarium presents "Kelp Kornicopia!" as one of its "Family Days" programs.
In order for kelp to get the nutrients it requires, the water temperature must be between 5 and 20 degrees Celsius. "Kelp changes with ocean climate, with El Niño [which brings currents of warm water] and La Niña [which brings currents of cold]," says marine ecologist Ed Parnell. "The cold water is conducive for kelp to do quite well, but it does poorly during the warm El Niño."
Visitors to the aquarium will have the opportunity to touch algae during an interactive tank dive. "For living creatures, both plants and animals, life would be miserable without mucus," Stewart says. The mucilage created by the kelp (and most aquatic plants) protects the organism from abrasion and aids in the flexibility of its blades in the water. The abalone, a mollusk that feeds primarily on kelp, is immune to the slippery substance. "Abalone will have its foot and extend its mouth [the layer of flesh, or mantle just inside the shell], and it leaves these 'lips,' if you will, sort of out in the water; if kelp comes by and touches [this extended part of the abalone], it gets stuck to it. You can touch this part on an abalone that it catches kelp with, and it won't do anything to your finger. But if you touch kelp and then touch [this part], it will stick like superglue." This suction is not permanent, explains Stewart. "They let go after a second, when they figure out they don't have seaweed."
The kelp anchors itself to the rocky sea bottom with its holdfast. "The holdfast looks like a tangled root system. The individual strands of that root-like structure are called haptera, and those will reach into crevices and essentially cement themselves to the rock," Stewart explains.
"When you look at kelp from the top, like when you're fishing, it looks like a thin floating mattress of kelp; that's where I think the word 'bed' came from. But if you dive down below the canopy, or visit the aquarium, you can see the stipes, or kelp stems, which are equivalent to tree trunks. Because they're flexible, the ropelike stipes -- about the diameter of your finger -- can bend. Extremely strong waves can rip up kelp from their attachments, but they can withstand the most common waves."
In the past century, the health and abundance of local kelp forests -- the largest of which are off the La Jolla and Point Loma shores -- has not been consistent. According to the 2002 Annual Status of the Fisheries report for the California Department of Fish and Game, the annual harvest reached a high of 395,000 tons in 1918 and a low of less than 1000 tons in 1931. Until the company relocated to Scotland in the summer of 2005, nearly all of the kelp along the California coast since 1929 was harvested by Kelco (originally "Kelp Co."), which was acquired by International Specialty Products Inc. in 1998. No large-scale kelp harvesting has been conducted along the coast of California since.
"They would just harvest the first few feet of kelp, and the kelp would regenerate. It's a nice, sustainable industry," says Stewart. Current regulations specify that harvested kelp can be cut no deeper than four feet beneath the surface. Kelp fronds can grow up to two feet a day. Though individual fronds do not live longer than approximately nine months, the base, or holdfast, of the kelp plant can live for up to eight years.
From the kelp, companies like International Specialty Products Inc. make algin and agar. "They're stabilizers and emulsifiers," explains Stewart. "We often eat those without knowing. One common way we eat seaweed is as emulsifiers in chocolate milk and ice cream." Algin is used in cake mixes, salad dressings, frozen foods, and canned foods, as well as nonedible products like cosmetics and building materials. According to the Encyclopedia of Alternative Medicine, kelp contains about 30 minerals and is rich in iodine, calcium, sulfur, and silicon. Kelp is sometimes used as a dietary supplement for people with mineral deficiencies.
"I wouldn't think you could survive on kelp solely," says Stewart. "Just like you can't get all of your nutritional needs only from beans and rice. But I don't think it would hurt you. My friend Steve once saw a guy collecting sea palms [another brown seaweed] and asked, 'What are you collecting them for?' and the guy said, 'I boil them and eat them with mayonnaise.' Steve asked, 'What do they taste like?' and the guy answered, 'Mayonnaise.'" -- Barbarella
Saturday, November 18
11 a.m. to 3 p.m.
Birch Aquarium at Scripps
2300 Expedition Way
Cost: $11 adults; $9 seniors; $7.50 youth (aged 3-17): additional $4 for "Explore It" class
Info: 858-534-3474 or www.aquarium.ucsd.edu/public