Disturbed Macrocystis Pyrifera holdfasts : who leaves, who stays

Macrocystis pyrifera (12) were subjected to a controlled shore wash-up treatment to determine which animals leave from and which remain within holdfasts detached from a rocky substrate. The procedure encompassed five phases: 1) separation from bottom and drift to surface 2) Drift at surface; 3) Wave wash in surf zone; 4) Out of water on shore; 5) Recovery of the holdfast. Among the varieties of animals inhabiting M. pyrifera holdfasts, amphipods and polychaetes make up the great majority (75%). Most of the animals capable of leaving the holdfasts did so during the ascension to the surface and during the early part of the drift phase. Responses varied for groups and species. Indirect evidence suggests that pressure change may be primarily responsible for the exodus.