This lovely photograph shows the three common urchins found in eastern Pacific kelp forests. Starfish, Solaster Sp. Photo by Paul Banko Asteroid starfish are abundant in kelp forests and are important predators on benthic invertebrates such as urchin. Locally abundant starfish predation is sufficiently intense to eliminate urchins and to allow patches of kelp to grow. These aggregations cause the appearance of gaps, creating a patchy landscape in a kelp forest area.
Urchin behavior is connected to kelp community structure by a fascinating feedback loop.
Food abundance affects urchin feeding behavior and feeding behavior, in turn may determine the pattern of kelp recruitment. The word forest is very appropriate for eastern and northern Pacific kelp habitats. In many cases, a surface canopy is present. Kelps such as Macrocystis and Nereocystis have floats that keep fronds at the water surface. Several other distinct vertical layers may also be present.