University of Southern California Sea Grant Program

Help with Kelp

El Niño effects can be devastating to kelp. High waves from the storms produced during El Niño tear the canopy and rip up holdfasts causing massive damage to the structure of the kelp forests. For example, after the 1982-83 El Niño, certain kelp forests off the coast of San Diego and off of the Palos Verdes peninsula in Los Angeles were reduced by 90-95% (Nybakken p.191). This most recent El Niño in 1997-98 also caused massive losses. Off of Catalina Island much of the kelp has been lost due to the two El Niño events and there has been little recovery.

Kelp needs nutrients to grow, and that is another reason why plants have so much trouble recovering—the warm tropical water that arrives with El Niño contains very few nutrients. The growth of kelp plants is slowed and new plants cannot get started. Since conditions in the kelp forest are different after El Niño, for example less canopy and therefore less shade, new varieties of plants can start growing and then young kelp cannot grow in that area. Sea urchins normally dine on kelp drift (pieces of kelp that have broken off and formed 'mats' that drift on the ocean surface). The drift is no longer available since kelp is not growing normally during El Niño conditions. As a result, hungry sea urchins that now do not have their normal food, will move in 'fronts' eating all the plants in their path. Sure is hard for young kelp to have a chance at growing under these circumstances! So El Niño conditions can not only wipe out kelp beds but the kelp environment may not be able to recover even when the conditions change.