Kelp
What is Kelp?
Kelp is a type of marine brown algae (Phylum Phaeophyta). Other marine algae groups include green algae (Phylum Chlorophyta) and red algae
(Phylum Rhodophyta). Though often brown, kelp can range in colour from
golden, through olive green, to purplish. Kelp form “forests”
in the sea and thus provide 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
along in our area is the bull kelp (Nereocystis luetkeana). The giant
kelp (Macrocystis species) can grow to lengths of 45 m. The most
common kelps in the harbours of the CRD are Laminaria species; others
found here include Agarum, Costaria, Pterygophora, and wireweed (Sargassum
species). Sargassum is an exotic species that was introduced from Japan,
along with Japanese oysters, which are cultivated.
Where does kelp grow?
Kelp grows on rocky shores, in areas with abundant nutrients, moderate water motion and cool, clear, salty water. Kelp is found in many areas of the world in mid 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.
Significant kelp beds grow in Esquimalt Lagoon, where they cover approximately
six hectares of the bottom, in moderate to dense concentrations. Laminaria
saccharina is the dominant kelp species, and is most common in the northeast
portion of the lagoon and near the entrance. Other species present here
include Alaria, Desmerestia and Sargassum.
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 of Dallas Bank. The most common species in this harbour are Laminaria and Agarum, followed by Sargassum and Nereocystis (bull kelp).
In Victoria Harbour, the most dense kelp beds are located between McCauley Point and MacLaughlin Point, and are composed of Laminaria, Nereocystis, Agarum and Pterygophera species. Other prominent kelp areas 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 obtain their energy from photosynthesis
(the use of 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 areas and provide nutrients, thus 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 varied, and represents 10 phyla. Some of the many creatures found in kelp forests include:
- fish, birds, seals, sea otters
- crabs, lobsters, shrimps, barnacles
- sea stars, sea urchins, sea cucumbers
- jellyfish and anemones
- limpets, clams, octopus
- sponges
- 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 over the summer. 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 proteting kelp, please visit our How Can I Help Section.
Additional Links & References
Websites
Articles
- Archipelago Marine Research Ltd. 2000. Subtidal Survey of Physical and Biological Features of Portge Inlet and the Gorge Waterway
- Connor, J. and C. Baxter. Kelp Forests. Monterey Bay Aquarium Foundation, 1989
© Image courtesy of Mary Sanseverino
