When we think about coral reefs, the first thing that comes to mind are usually the colourful and diverse coral reefs in the tropics. But did you know there are corals found in the cold waters north and south of the equator too? In fact, there are about 700 species of cold, deep-water corals found around the world – including here off the coast of Canada!
Much like their tropical coral relatives, cold-water corals are brightly coloured and come in many shapes and sizes. And while corals may look like plants, they are actually animals. Every coral you see is either a solitary animal, called a polyp, or a colony of polyps that together can form incredibly large and branching corals.
Tropical corals are restricted to shallow, sunlit waters because they rely on a symbiotic relationship – where both species benefit – with small algae, called zooxanthellae, that live within their cells and create energy from the sun. Cold-water corals, on the other hand, have adapted to live in the absence of sunlight and rely entirely on filter feeding. Each coral polyp has several tentacles that feed by capturing dead matter and small living organisms, like phytoplankton and zooplankton, that drift by in ocean currents.
Cold-water corals are slow to grow but can be extremely long lived, with records of some individual of cold-water coral species reaching nearly 1,000 years and some cold-water coral reefs systems that are many thousands of years old. Scientists are able to determine the approximate age of corals because their “skeletons”, made of calcium carbonate that the corals extract from surrounding seawater, have distinct growth rings much like the rings inside a tree trunk.
By now you’re probably wondering where you can find corals in Canada? Although most are found at such great depths that they are only visible by submersible and remotely operated vehicles, corals and coral reefs can be found along the Pacific, Atlantic and even Arctic coasts of Canada. Through Oceana Canada’s expeditions over the years, we’ve been able to see many different coral species along Canada’s coasts, which you too can discover here!
Here are some of the amazing corals that are found along the coasts of Canada.
Bubblegum coral – Paragorgia arborea
Bubblegum corals are one of the largest coral species found in North America. They get their name from their appearance: they are often bright pink and the polyps at the end of their branches resemble wads of gum. The three-dimensional structure of bubblegum corals also provides important structural habitat for other sea creatures like northern shrimp.
Red tree coral – Primnoa resedaeformis
Red tree coral, sometimes also called a sea corn or sea fan coral, is a large, branching coral that ranges in colour from a yellowish-orange to bright red. These corals form important habitat for many animals, including rockfish in the Pacific and redfish in the Atlantic. Red tree corals are excellent oceanographic indicator species, with scientists able to extract information about water temperature from the growth rings inside their skeletons, as well as information about what the coral was eating and other variables in the water that affected their growth.
Lophelia coral/Spiders hazard – Lophelia pertusa
Lophelia coral is an important deep-sea, reef-forming coral and can be incredibly long-lived. They are a bushy, branching coral whose branch-like skeletons grow out and fuse together, forming reefs. As the coral reef grows, the corals continue to grow on top of each other with dead coral skeletons forming the center of the reef. The largest known intact lophelia reef can be found off the coast of Norway. It measures 40 kilometres long by three kilometres wide and is estimated to be tens of thousands of years old. In Canada, most lophelia corals are found along the edge of the Scotian Shelf, in the Atlantic Ocean.
Sea pens – Penatulacea spp.
Sea pens are colonial corals. Like their relatives, sea pens are made up of a colony of several polyps. What makes them unique among colonial corals is that each polyp is specialized to perform specific functions. One of their polyps develops into a rigid, erect stalk, which anchors the rest of the colony to the ocean floor. This gives many sea pens an appearance similar to a large feather or old-fashioned quill pen, which is how they got their name.
Sea strawberry – Gersemia rubiformes
Sea strawberries are a type of soft coral, which means they do not produce stony, calcium carbonate skeletons like many of the larger corals. Instead, their skeletons are made up of small, stiff, spiny elements called sclerites, which help to give the coral structure and provides a substrate for the polyps to grow, feed and reproduce on. Large clusters of sea strawberries are collectively known as strawberry grounds, and are recognized as being important nursery and feeding habitats for lobsters, basket stars, and more.
Although scientists have just started to observe cold-water corals in their natural habitats over the past few decades, most species of cold-water coral are currently at risk. They are threatened by destructive fishing practices, offshore oil and gas drilling, and ocean warming and acidification caused by climate change. By protecting important marine habitat and reducing destructive fishing practices, we can help protect cold-water corals and the animals that rely on them. You can learn more about our campaigns to protect marine habitat, and take action, at Oceana.ca/ProtectHabitat.