Effects on the Animal Community of Dislodgment of Holdfasts of Macrocystis pyrifera

Abstract

Effects of natural dislodgment of holdfasts of Macrocystis pyrifera (L.) C. Agardh on the associated holdfast community were studied during a 110-day period. Six holdfasts were collected at the beginning of the study and analyzed to determine the abundance of major taxa at time O. Forty-four holdfasts were detached from the rocky substrate and suspended on three midwater buoys to simulate natural dislodgment and drift in the kelp forest. The most abundant taxa associated with attached and drift holdfasts were decapod crustaceans, mollusks, polychaetes, ophiuroids, echinoids, asteroids, isopods, and amphipods. Only amphipods and isopods increased significantly in density in drift holdfasts during the experimental period. All other invertebrate taxa showed a decrease in abundance during the 3-month experiment.