Exploring the Intertidal

Check out the intertidal zone and its biodiversity!


This phylum includes the brown algae, and is almost exclusively marine. All phaeophyte species in this group are multi-cellular. The giant kelps also belong to this group. These amazing algae can grow a metre in length in a couple of weeks, and dozens of metres in a single year! This group contains the pigments chlorophyll a and c and fucoxanthins. Most brown algae are found in the intertidal or shallow subtidal, and they are more abundant in the Northern Hemisphere. Kelp are becoming very important commercially: for food, cosmetics, pharmaceuticals and in the sciences.

A kelp can easily be identified by four basic structural components (three shown on left): blade/frond (photosynthetic portion), bulb (used as a float to keep blades near light at the surface; only present in some species), stipe (analogous to a stem in vascular plants), and holdfast (root-like or disk-shaped; attaches the kelp firmly to the substrate) (for more on brown algae, click here).

Egregia menziesii (Feather Boa Kelp)
 Small branches and floats off either side of thick stipe.
Range: British Columbia to California.
Habitat: Exposed, rocky shores. Low intertidal to upper subtidal.
Cool Fact: Used as fertilizer by coastal farmers!

 Fucus gardneri (Rockweed)
Green to brown. Dichotomous branching. Swollen receptacles at end. Midrib present.
Range: Alaska to California.
Habitat: Attached to rocks. Mid to low intertidal. Often the most common intertidal algae on B.C. shores. It is difficult to miss!
Cool Fact: The receptacles contain the gametes, which are released after a period of desiccation. A hardy algae - capable of tolerating extreme physical conditions!

Laminaria setchellii (Split Kelp)
Brown to black. Smooth blade with a split down the centre.
Range: Alaska to California.
Habitat: Very exposed rocky shores. Low intertidal to upper subtidal.
Cool Fact: This algae can survive the high velocity and heavy turbulence found in surge channels!


Leathesia difformis (Sea Cauliflower)
Yellow. Hollow, convoluted and spongy.
Range: Bering Sea to Mexico.
Habitat: Rocky shores. Sometimes epiphytic. All intertidal zones.
Cool Fact: Originally thought to be a jelly fungus!

Macrocystis integrifolia (Giant Kelp)
Blades branch along length of stipe. Small float at the base of each blade.
Range: Alaska to California.
Habitat: Rocky shores. Low intertidal to 10m deep.
Cool Fact: This kelp grows incredibly fast - 20cm in only a few days! Also important because herring lay their row on this kelp.

Nereocystis luetkeana (Bull Kelp)
Long stipe with bulb and long fronds at one end.
Range: Alaska to California.
Habitat: Rocky shores. Upper subtidal and lower.
Cool Fact: One of the largest kelps! An annual alga that can grow 25m or more in a single year! The float is filled with carbon monoxide to keep the blades at the surface.

see more about Phaeophyta!

  to Intertidal Field Guide directory

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