Slide 1
A forest of algae
Kelp forests are made by large brown algae. Their branching holdfasts grip rock while flexible blades reach into sunlit water.
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A holdfast resembles a root but mainly anchors the alga. Kelp absorbs dissolved nutrients across its surfaces, so it does not need soil beneath a rocky reef.
Slide 2
Reaching the light
Some kelps carry gas-filled floats that lift their blades. Their flexible bodies bend as waves pass through the forest.
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A forest can contain several species with different heights. Taller kelp shades smaller algae beneath it, creating layers of habitat rather than a uniform underwater lawn.
Slide 3
A place to shelter
Kelp provides surfaces and hiding spaces for animals. Small fish and invertebrates can live among blades and tangled holdfasts.
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Shelter is only one service. Grazers eat kelp, and detached fragments carry food away from the living forest, linking nearby habitats through drifting organic material.
Slide 4
Changing the water
Dense kelp growth can soften water movement and shade the seabed. The forest changes conditions for its own residents.
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These effects depend on forest density and local waves. An exposed rocky coast and a sheltered cove need not receive the same protection from similar kelp species.
Slide 5
A forest can disappear
Heavy grazing and unusually warm conditions can reduce kelp cover. A rocky seabed does not guarantee a lasting forest.
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Restoration therefore requires more than attaching young kelp to rocks. Conditions that allow growth and the balance between kelp and its consumers both matter to recovery.
Sources
- Kelp and Kelp Forests
Smithsonian Ocean
- Kelp Forest Habitat on the West Coast
NOAA Fisheries