Forests of Macrocystis pyrifera, or giant kelp, grow in coastal areas of
temperate oceans. Kelps are not really plants at all -- they're actually brown
algae. Kelp forests such as this one in Monterey Bay off the California coast
are unique habitats for all kinds of marine life, from microscopic algae to sea
horses to grey whales. Some creatures feed on the kelp, others use the kelp
to hide from predators. Still others lay in wait amongst the fronds for lunch to
come swimming by.
Giant kelp can grow two feet per day to a length of about 200 feet. Brown kelp algae looks like a "real" plant, but it's got different parts. Kelp's "root," called the holdfast, is the base that attaches the kelp to rock or coral on the sea floor. Kelp does not absorb nutrients through the holdfast but from all of its surfaces, including the "leaves" or blades, which do most of the photosynthesizing. Pimply-looking air-bladders called pneumatocysts keep the blades afloat.
The ecosystem of a kelp forest is intricate and precariously balanced. Overfishing of predators such as lobster, which feed on kelp-eating urchins disrupts the balance and allows the urchins to snack unchecked. With their huge waves and influence on other weather systems, storms can either uproot the kelp or make the water too warm for the kelp to thrive. Kelp forests support a complex food web that includes humans, too. Algin from commercially harvested kelp is used as an emulsifier in everything from juice drinks to dairy products. Kelp is also made into fertilizer, pet food and cosmetics.
Photo by Kip Evans, Courtesy National Marine Sanctuaries, NOAA.
