Kelp Forests in Canada

Description

Located in shallow, coastal waters, kelp forests thrive in the cold, nutrient-rich waters of temperate and polar regions. They are made up of fast-growing kelp species such as giant kelp (Macrocystis pyrifera) and bull kelp (Nereocystis luetkeana), which can grow up to 45 cm a day. Due to their dependence on sunlight for photosynthesis, kelp forests are rarely found beneath 14 to 46 m in depth. Like land-based forests, kelp forests produce oxygen, store carbon and can mitigate the impacts of climate change while simultaneously creating crucial habitat along the coasts of Canada. This ecosystem takes up a substantial amount of carbon dioxide, at a similar per-area rate as rainforests. Kelp forests are highly dynamic, arising quickly in favourable conditions. However, a kelp forest can also disappear rapidly due to changes in ocean conditions such as warming waters or low nutrient levels. Variations in sea urchin populations will also impact kelp forests; unregulated urchin populations will lead to what is known as an urchin barren, since the herbivorous invertebrates can overgraze on kelp and lead to the destruction of entire kelp forests.

Distribution

Kelp forests are found in all three oceans bordering Canada: the Arctic, Atlantic and Pacific. The best-known kelp forests in Canada are found on the West Coast of British Columbia. This ecosystem thrives in the cooler waters of temperate and polar latitudes worldwide. Kelp forests vary with the seasons, with their growing season beginning in the spring and extending throughout the summer before peaking in early autumn. In the winter, storms and strong winds will tear kelp fronds and rip out kelp forests, decreasing the density and availability of habitat.

Ecology

Kelp forests provide habitat for many species. This ecosystem acts as a shelter and nursery habitat, as well as a hunting ground for certain predatory species. Sea urchins, rockfish, sea otters and seals are some common inhabitants. Fish such as herring and juvenile salmon and various birds, including gulls, terns, snowy egrets, herons, cormorants and shore birds, also enjoy kelp forests. As a result, kelp forests support high levels of biodiversity and provide the basis of the food web, since the herbivorous species will feed on the kelp. The density and health of the kelp forest will have an impact on many of these species, with changes in kelp populations potentially leading to cascades throughout the food web.

Kelp forests also protect coasts from storms and erosion by reducing wave energy and improving water quality by absorbing excess nutrients such as nitrogen while supporting fisheries by sheltering commercially fished species such as rockfish, crab and lobster (see Living Shorelines).

The health of kelp forests depends on the presence of sea otters. These small mammals are keystone species in kelp forests, feeding on sea urchins and helping regulate their populations. Without sea otters, kelp forests are at much greater risk of being ravaged into urchin barrens. In the past, overhunting of sea otter populations for the fur trade negatively affected kelp forests by allowing urchin populations to become unregulated. In the last 50 years, the hunt for sea otters ended, allowing their populations to recover along the Pacific coast and, in turn, supporting the recovery of some kelp forests.

Conservation and Threats

Despite some recovery over the last half-century, kelp forests remain at risk as climate change intensifies and ocean temperatures rise. Warmer springs and summers, as well as marine heatwaves such as the Blob (a large mass of warm water extending from Alaska to Mexico in the Pacific from 2013 to 2016, which had severe impacts on weather, wildlife and fisheries), decrease the resilience of kelp forests, leading to the decline of this important habitat. Major kelp forest habitat has been lost in the Salish Sea, off the coast of British Columbia, with over 5.5 million square metres disappearing in 12 years. Furthermore, climate change decreases ocean mixing, reducing nutrient delivery to kelp forests and further threatening them. Strengthening storms also negatively impact kelp forests by dislodging the kelp fronds. Additionally, destructive fishing practices, coastal pollution and accidental damage from boat entanglements threaten kelp forests.

Groups such as the Kelp Rescue Initiative work with First Nations to revitalize kelp forests in Canada. By assessing multiple facets of kelp restoration, such as researching restoration methods, thermal tolerance and adaptation of kelp, the status of kelp and working on community outreach, these groups aim to restore and preserve kelp forests on the west coast of Vancouver Island.