By: Lauren Farley
Wouldn’t it be wonderful if Atlantic Canada had some of the gorgeous, diverse, and stunning coral reefs we see all around the tropics? Well guess what, we do! They are just a little harder to see from the shore...
The Atlantic Ocean is home to many species of cold-water, or deep-water coral species. Now before we get into that, what is a coral?
Corals are often mistaken for plants, but they are actually very important animals. Corals are part of the cnidarian phylum which also consists of our friends the jellyfish and sea anemones. I like to think of corals as a colony of tiny upside-down jellyfish. Picture a jelly with its tentacles up and their bells stuck to a limestone skeleton - this single individual is called a polyp. The large corals we see when we look at a reef are composed of colonies of many coral polyps.
Photo: A close-up look at a coral polyp, notice the tentacles facing up and the little green stuff is the algae housed inside the coral that photosynthesizes (Credit: Smithsonian Ocean)
Corals are a very important species for MANY different reasons, but one of their biggest claims to fame is their capacity to produce oxygen. Corals house tiny micro-algae that photosynthesize or produce oxygen from CO2 and sunlight energy, just like plants. Access to sunlight is important for photosynthesis which is why many people think corals only exist in shallow, tropical areas. However, not all species of corals photosynthesize. Cold-water corals are one of the deep sea’s best kept secrets. These majestic animals are one of the coolest groups of species and, if you’re curious why, let me explain.
Unlike tropical corals, cold-water corals don’t need sunlight to eat and live. The waters surrounding Atlantic Canada is home to many species of cold-water corals. It’s hard to say how many species of cold-water corals exist since scientists have only been studying these corals for the last decade. But there are at least 45 described species in Canada's Atlantic Ocean. These corals can be found living at depths greater than 4 kilometers, living in waters as cold as -1ºC (which happens to be the average temperature of Halifax in December).
Corals in Atlantic Canada can live in temperature less that -1o C!
So if these corals don’t need sunlight to photosynthesize, how do they eat? Cold water coral polyps are typically larger than those of tropical corals so they are able to trap food particles from the surrounding water. These corals still rely on photosynthesis in a way, but the food particles they eat are things like zooplankton, which also use photosynthesis from sunlight provided at the surface ocean.
Another reasons these corals are so cool is their age and size. These corals are OLD, like very old. Radiocarbon dating of a coral off the coast of Norway estimates it to be around 8,000 years old, give or take a few thousand years. It one of the longest living animals! Some corals studied in Atlantic Canada were also found to be over 1,000 years old.
These old corals are of great importance. By looking at their skeletons, we can use corals as a climate change indicator by determining historical water temperatures and other conditions from thousands of years ago. These deep-water corals are also huge. One species, the bubblegum coral, is said to be the largest marine invertebrate species with some reaching 6-10 meters in height!
The bubblegum coral (Paragorgia arborea) named after its appearance can reach heights up to 10 meters! (Photo: Oceana Canada)
These deep-sea dwellers form vast coral "forests" which provide important habitat for many species. They are also very important for medicine development and some are currently being studied for their ability to block tumors in cancer research. Unfortunately, these corals are very vulnerable to climate change because they require very specific environmental conditions. Currently cold-water coral conservation focuses on establishing Marine Protected Areas to make sure these corals are safe from destructive fishing practices.
For more information on these awesome animals check out this video from DFO.