Marine Ecosystems

Kelp Forests



Worldwide in temperate to polar latitudes





Kelp thrives in cold, nutrient-rich waters. Since kelp is not actually a plant, it does not have roots. Instead, it obtains all of its minerals and nutrients directly from the water, attaching itself to the rocky bottom by a structure known as a holdfast. Like plants however, kelp harvests the sun’s energy through photosynthesis. In order to remain upright and grow towards the water’s surface, each kelp blade (leaf) includes a gas-filled pod that floats. Because kelp attaches to the seafloor and eventually grows to the water’s surface and relies on sunlight to generate food and energy, kelp forests are always coastal and require shallow, relatively clear water. In Canada, kelp forests of differing species can be found off all three coasts in the Atlantic, Arctic and Pacific Oceans, with the most famous kelp forests in Canada found off the coast of British Columbia.

Kelp forests provide important three-dimensional, underwater habitat that is home to hundreds or thousands of species of invertebrates, fishes and other algae. Some species aggregate and spawn in kelp forests or utilize these areas as juvenile nursery habitat. Predatory species of sharks and marine mammals are known to hunt in the long corridors that form in kelp forests between rows of individual plants. 

Though kelp forests are important ecosystems wherever they occur, they are incredibly dynamic. In other words, they can disappear and reappear based on the oceanographic conditions and the populations sizes of the species that prey on them; sea urchins. Warmer than normal summers and seasonal changes to currents that bring fewer nutrients to kelp forests (both sometimes occurring naturally) combine to weaken kelps and threaten their survival in some years. Strong individual storms can wipe out large kelp forests, by ripping the kelps from the seafloor. Large gatherings of sea urchins, a herbivore that eats kelps, can prevent kelp from growing large enough to form forests. The cycle between these so called “urchin barrens” and well-developed kelp forests is a well-studied phenomenon in regions that are favourable for forest formation. Each of these natural alterations to kelp forest density or total area affects the community of invertebrates and fishes that live in this ecosystem. Population sizes of many of these species, including some that are commercially important food species, depend on the success of kelp growth each year.

Destructive fishing practices, coastal pollution and accidental damage caused by boat entanglements are known to negatively affect kelp forests. Area based management, such as the designation of marine protected areas (MPAs), is an effective way to protect kelp forests from excessive use or harm by people.




  • Sea otters wrap themselves in giant kelp to keep from floating away while sleeping.
  • Some kelp species can measure up to 45 metres long. If living in ideal physical conditions, kelp can grow 45 centimetres a day.
  • Kelp forests compromise one of the ocean’s most diverse ecosystems. Many fish species use kelp forests as nurseries for their young, while seabirds and marine mammals like sea lions and sea otters use them as shelter from predators and storms.
  • Sea urchins can destroy entire kelp forests at a rate of 9 metres per month by moving in herds. Sea otters play a key role in stabilizing sea urchin populations, by eating them, so that kelp forests can thrive.
  • Giant kelp is harvested from kelp forests and used as a binding agent in products like ice cream, cereal, ranch dressing, yogurt, toothpaste, lotion and more.





Bamfield Marine Station: Kelp forests of British Columbia

DFO Assessment of information on Irish moss, rockweed and kelp harvests in Nova Scotia

NOAA Ocean Facts

NOAA National Marine Sanctuaries

Monterey Bay Aquarium

Ocean Wise Seaweed in BC Report