Rock Platforms: Subtidal Zone - Macrocystis Holdfast

A large, root-like fibrous holdfast anchors the kelp to the substrate. The holdfast usually remains submerged, except when tides are extremely low.

The stresses on the holdfast as the waves surge onto the rock platform are enormous, and often the rocks themselves will break away before the holdfast is dislodged.

Macrocystis angustifolia occurs in relatively shallow water (0 -10 metres) off the southern coasts; Macrocystis angustifolia grows in deep water (> 6 metres) off the Tasmania coast.

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Move the mouse over the image to examine Macrocystis.