What is Kelp?
Kelp is a type of marine brown alga (Phylum Phaeophyta
). Other marine algal groups include green algae (Phylum Chlorophyta
) and red algae (Phylum Rhodophyta
). Though typically dark brown, kelp can range in colour from golden, through olive green, to purplish. Kelp forms “forests” in the sea and thus provides habitat and nutrients for a vast array of creatures. Many species of kelp are common to the coasts of B.C. One of most well-known in our area is bull kelp (Nereocystis luetkeana
). This distinctive whip-like kelp has a large round float (pneumatocyst) with many long flat blades trailing from it, reaching lengths of up to 20m. The most common kelps in the harbours of the CRD are non-floating species including Laminaria
, and Sargassum. Sargassum
is an exotic species that was introduced from Japan along with Pacific oysters, which are cultivated
Where does kelp grow?
Kelp grows on rocky shores, in areas with abundant nutrients, moderate to strong wave action and cool, clear, seawater. Kelp is found in many areas of the world in temperate and northern latitudes where these conditions are met.
Kelp (mostly Laminaria saccharina
) is common in the lower Gorge Waterway
and Victoria Harbour
in the Selkirk Waters, where considerable tidal flushing occurs.
There are also large kelp beds in Esquimalt Lagoon
covering approximately six hectares of the bottom. Laminaria saccharina
is the dominant kelp species, and is most abundant in the northeast portion of the lagoon and near the entrance. Other species present here include Alaria
In Esquimalt Harbour
, kelp is most prominent at the entrance (on both shores), along the southwest shore, around Smart and McCarthy Islands, around Inskip Islands and off Dallas Bank. The most common species in this harbour are Laminaria
, followed by Sargassum
In Victoria Harbour, there are dense kelp beds between Macaulay Point and McLoughlin Point, composed of Laminaria, Nereocystis, Agarum
species. Other areas with kelp beds in this harbour include Rose Bay, Shoal Point, Work Point and Coffin Island Point. The species of kelp previously mentioned are represented here, in varying densities.
How does kelp live and reproduce?
Like land plants, marine algae are photosynthetic (using sunlight to convert carbon dioxide and water to simple sugars). However, since they can obtain their nutrients directly from the surrounding water, and live in fairly constant temperatures, they have much simpler tissues and structures.
The main structures of kelp consist of a holdfast, stipe, and blades. The holdfast’s purpose is to anchor the kelp to the bottom; it doesn’t absorb nutrients as a land plant’s roots do. The stipe is similar to a plant’s stem, though simpler; it delivers the sugars of photosynthesis from the blades to lower portions of the plant. Some kelps grow hollow, gas-filled bladders from the stipe that aid in flotation. The leaf-like blades grow at or near the surface of the water, where they use the energy of the sun to make the sugars and amino acids necessary for survival.
Most kelp lifecycles have two distinct phases. The large plants we see are only half the story. These are called sporophytes, and reproduce asexually, by releasing swimming spores that attach to the bottom. These spores develop into microscopic male or female forms called gametophytes. The female gametophyte produces an egg, and attracts male sperm by releasing a chemical called a pheromone. Once the egg is fertilized with sperm, it quickly develops into the large sporophyte once again.
How have people used kelp?
People all over the world have used various types of kelp as a food. Even today, some kelp is used as a health supplement. Extracts of kelp are used as stabilizers and emulsifiers in products including toothpastes, lotions, soaps, and ice cream. Furthermore, coastal peoples have long relied on hunting animals that live within kelp beds, such as fish, shellfish, seals and otters.
Why is kelp important?
Kelp forests are among the most diverse and productive ecosystems in the world.
They create sheltered habitats and provide a food source for herbivores, creating a hospitable environment for animals and other algae. Kelp is a nursery ground for juvenile fish, a garden for grazing limpets and sea urchins, a smorgasbord for sea otters and seals.
Forests on land are known for their diverse animal life, and host species from about three major groups or phyla. The animal life in kelp forests is even more diverse, and representing more than 10 phyla. Some of the many creatures found in kelp forests include:
- fish, birds, seals, sea otters
- crabs, shrimps, barnacles
- sea stars, sea urchins, sea cucumbers
- jellyfish, coral and anemones
- limpets, abalone, snails, clams, octopus
- and less well-known animals such as lampshells, “moss-like” bryozoans, flatworms and segmented worms
150 different species have been recorded living among kelp holdfasts alone. Other species live on the sea floor and within the canopy. In addition to providing habitat and food, kelp dampens the energy of waves and currents, reducing coastal erosion.
Bull kelp has an annual growth cycle; each winter, the plants die off and are replaced during the spring. Winter storms tear up plants, and tonnes of kelp are washed up on the beaches. These decaying masses provide food and shelter for tiny animals such as insects and beach hoppers, and nourish coastal plants.
What threatens kelp?
Sea urchins can “clear-cut” huge areas of kelp forests. Normally, predators like the sea otter keep urchin populations in check. However, in the 1700s and 1800s, sea otters were hunted to the brink of extinction. This resulted in a significant loss of kelp forests and the fish and animals that live in them. Today, the sea otter is protected and populations are slowly recovering. Excessive sediment, resulting from development or logging in the watershed, can increase the turbidity of the water. This may result in less light penetration so that kelp cannot grow.
Kelp is sensitive to changes in temperature and nutrients. Global fluctuations such as El Niño have been known to cause kelp deforestation when warm waters intrude in normally cool areas. Global climate change could affect the distribution and population of kelp beds.
How can I help protect kelp?
For information on protecting kelp, please visit our How Can I Help?
Additional Links & References
© Image courtesy of Mary Sanseverino
- Archipelago Marine Research Ltd. 2000. Subtidal Survey of Physical and Biological Features of Portage Inlet and the Gorge Waterway
- Connor, J. and C. Baxter. Kelp Forests. Monterey Bay Aquarium Foundation, 1989