Monterey Bay Aquarium Research Institute
Marine Botany

Kelp Coverage


Macrocystis can be found off the coasts of several continents around the world.  They can be found off the west coast of North America, from southern Alaska to Baja California.  They may also be found off the coast of South America, South Africa, and southern Australia (Connor and Baxter 1989).

Kelp canopy on surface

This is an aerial view of Macrocystis pyrifera cover off the central California coast.  The kelp forest is the dark region in the middle of the picture.

In order for giant kelp to flourish in a particular environment, it must have a hard surface for attachment, high nutrient concentration, moderate water motion, and clear and clean ocean water. Macrocystis prefers salty, well-mixed salty water in the outer coastal waters (Connor and Baxter 1989).

The ocean is usually a two-layered ocean with a warm, less dense surface layer and a dense, cold bottom layer.  The barrier between the two zones is referred to as the thermocline.  Off central Californian coasts, dissolved nutrients are high, due to upwelling from below the thermocline.  Giant kelp may grow 14 inches in a single day under such conditions.  In southern California, summer months bring warm, calm oceans.  This inhibits mixing of nutrients from below the thermocline.  During these times, Macrocystis growth is greatly inhibited, and must employ trace nutrients to sustain life (Connor and Baxter 1989).

Copyright 2001:  James Lopez

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