Corals… In the Arctic?
Josh Pysanczyn
Since the mid-eighteenth century, ocean explorers, scientists and voyagers of the deep have been dredging up relics of a hidden world beneath the ocean. Thankfully, since then, the exploratory methods by which we carry out our research have not only become less destructive, but far more technologically advanced. Under careful guidance from acoustic surveyors and deep-sea submersibles, we can now venture ever further into the Arctic abyss and challenge the conventional wisdoms of our time.
As technology advances and exploration continues, we begin to uncover more about the mysterious world of the Arctic. Photo: Pexels.
Conventional Wisdom
As much as textbooks would have us believe, corals thrive in waters very different to the clear, warm lagoons of the tropics. In fact, it’s been suggested that of the 5100 species of coral alive today, over half are found in cold waters.
These corals inhabit the continental shelves, fjords and sea mounds of all the world’s oceans. They consist of three main groups: the stony corals, such as the reef forming Lopheilia pertusa; true soft corals, like the dandelion-esque Umbellula encrinus; and the Anthipitharians or black-corals.
These corals are generally restricted to water temperatures of 4 – 12˚C, which at higher latitudes means relatively shallower waters (50 – 1000m). At lower latitudes, however, these corals can be found at enormous depths of up to 4km.
Reef formation by cold water corals is a slow process – we’re talking between 5-25mm per year, slow – taking 1000’s of years to develop into the topographically complex structures we know of today. This, along with their longevity and relative fragility, make cold-water coral reefs extremely vulnerable to human associated destruction.
Just like their tropical counterparts, cold water corals provide a complex, 3-demensional ecosystem which offers shelter and sanctuary to a range of reef typical taxa including molluscs, crustaceans, marine worms, echinoderms and fish.
Once we stray past the arctic circle, however, things get a little different. The harsh array of conditions that are deemed inhospitable by many, select only a mere handful of well adapted coral species to construct this delicate habitat.
Of those found in the arctic, only two corals are said to be reef building: Flabellum macandrewi and Lophelia pertusa. The latter of these is a cosmopolitan, colonial species, coming together to form the world’s largest cold water coral reef, Røst reef.
Similarly to these tropical Scleractinian corals, stony cold-water corals provide biodiversity through complex 3-D structures, allowing all types of marine life to flourish. Photo: Maddie St Clair Baker.
Røst Reef
Beneath the icy waters patrolling the Lofoten archipelago in Northern Norway, lies the world’s largest known cold water coral city, Røst reef. After its discovery in 2002 during a series of routine acoustic surveys, scientists from the UK, Norway and Germany fought for their place aboard “Jago”, a two-manned submersible tasked with undertaking the first manned observations of the reef.
At a depth of 350m, the researchers discovered a coral reef extending over 40km! The myriad of local biological communities observed on the reef, whose diversity rivals that of tropical coral reefs, owe their survival to one, well adapted species of coral, our friend, Lophelia pertusa.
Adapting to the Arctic
In the tropics, reef-forming corals adapt to the nutrient poor, well-lit, warm, shallow waters by forming a mutualistic relationship with single celled algae called zooxanthellae. The respiring coral and photosynthesising algae live in perfect symbiotic harmony by trading their metabolic wastes. If this all sounds a bit alien to you, go check out Coral 101: The Basics… we’ve got you covered.
Now, as cold-water corals tend to live in the dark, they wouldn’t exactly benefit from this photosynthetic relationship and therefore lack the partnership – these corals are known as azooxanthellate.
Instead, these corals are entirely dependent on zooplankton and particulate organic matter. They use their outstretched tentacles like filters, trapping dead algae, decomposing animals and faeces floating by in the passing current.
But how do these corals survive such cold temperatures?
Interestingly, what seems to have tickled the fancy of scientists is not how these corals have adapted to the cold, but how well adapted they are to changes in temperature.
This might seem odd, but in fact it’s rather brilliant. Despite living in the deep, cold waters of the Arctic, these corals experience highly variable temperature fluctuations because of the encroaching Gulf Stream and downwelling of relatively warm surface water.
As we would expect, researchers from Norway and Germany discovered that L. pertusa readily tolerates a broad range of water temperatures, fluctuating from 5˚C to 15˚C without experiencing any significant levels of stress nor mortality. This not only highlights the adaptive capacity of cold water stony corals, but also provides extremely valuable data when predicting how this keystone organism will respond to global climate change.
Cold-water corals are azooxanthellate. They use their tentacles to grab bite-sized pieces of zooplankton floating by in the water column. Photo: Unsplash.
Conservation and Future
Although seemingly dominant amongst the arctic benthos, Norwegian scientists have suggested that between 30-50% of all Lophelia reefs in Arctic waters have been destroyed as a result of fishing practices such as bottom-trawling. Following their advice, in 1999 the Norwegian government put in place the Coral Protection Regulation, prohibiting the deliberate destruction of all its coral reefs.
Fishing practices using trawls and heavy equipment, as well as hydrocarbon and mineral exploration (not to mention our usual culprits: global warming and ocean acidification) represent the major threats to cold-water coral reefs.
Nevertheless, video observations of Røst reef highlight largely intact, dense Lophelia colonies on the reef, gaining recognition from the WWF as a Global Natural Heritage site. Conservation minded organisations have since urged the Norwegian government to go one step further and sanction reef specific protection for these ocean tethered treasures.
In 2003, Norway heard their call and amended both the 1999 Coral Protection Regulation and Nature Conservation Act, introducing ‘No-Trawl Areas’ around several ecologically important reefs including Røst.
Norway is pioneering the way in cold-water coral conservation and has since established a network of Marine Protected Areas (MPAs) in the North-East Atlantic spanning 60% of cold-water coral reef habitats. In this, the WWF recognises the actions of Norway as a Gift to the Earth - “a globally significant conservation act which demonstrates environmentally responsible leadership and is an inspiration to others”.
Furthermore, Norway’s Gift to the Earth has earned the respect and support of local fisherman and the community. They recognise the reef’s importance to their livelihood – setting an international example in cold water coral conservation.
Norway is leading the way in cold-water coral conservation. Photo: Unsplash.