Written by Sofia Perez
You, an intrepid ocean ROV, begin descending into the icy Norwegian inlet Tysfjord, North of the Arctic Circle. Your robotic eyes wide with wonder, you sink past familiar organisms- kelp and anemones, then fall into a twilight zone 200ft. down dominated by large sponges. You go a little deeper and you meet the Primnoa resedaeformis, a soft coral with elegant orange arms stretching from the wall. A little bit lower and you’re in the permanent night 500 ft. down, where all is quiet and dark like the sky without stars. Then you finally reach it, 700 ft. down in the midnight glory of the ocean- the lophelia pertusa.
Despite the staggering darkness of the ocean at 130-10,000 ft. down where it’s found, this cold-water coral offers a shining beacon of life to biodiversity such as clams, shrimp, small sponges, lobsters, bivalves, and a plethora of other bottom-dwelling invertebrates and fish which call these depths home. Any physical damage to these delicately formed coral skeletons have grave impacts on this diverse ecosystem which could take hundreds to thousands of years to recover. The threat of bottom-contracting fishing gear, for example, crushes all the coral in its path, offering a slow recovery at best.
Not much is known of these mysterious coldwater cousins and the magnitude of bottom-trawling’s impact on them, but it’s definitely not good news! Deep sea trawling involves dragging a heavy net fitted with rubber rollers across the ocean floor at depths of more than a kilometre, obliterating everything in its path. At first this technique was meant for shallow-water, but as fish stocks dwindled and technology met desperation, fishing fleets began trying their luck in deeper water. While this might put fish in the supermarkets, according to WWF, bottom trawling is currently the greatest threat to deep-sea biodiversity. In an experiment off Alaska, 55% of cold-water coral damaged by one pass of a trawl hadn’t recovered a year later and in heavily fished areas around coral seamounts off southern Australia, 90% of the surfaces where coral used to grow are now just bare rock.
The first thought most people have when picturing coral reefs are the shallow, tropical coral reefs located around the equator. These corals host photosynthetic algae which are able to provide nutrients to their host. In return, the host provides the algae with shelter and protection. However, far beneath the surface of the ocean, lophelia pertusa don’t have access to the sunlight needed to photosynthesize in this way. Instead, they are filter feeders, meaning they pick off plankton from deep-sea currents. After hundreds to thousands of years of careful construction, the calcium carbonate skeleton of these corals can stretch several miles and at least a hundred feet above the seafloor.
Moreover, these three-dimensional calcium carbonate fortresses house a wide variety of invertebrates and fish such as echinoderms, bristle worms, bryozoans and various demersal fish, offering increased food availability and a place to feed, breed, and nurse. They also increase habitat complexity on the continental shelf, slope, and seamounts, acting as an attachment point for sessile organisms.
We are still at the brink of discovery when it comes to the deep sea, and still among the marine biologist community the questions greatly outnumber the answers. For all these reasons and too many more to list, it is of the utmost importance that the lophelia pertusa be kept safe from all that threatens it. While most attention is concentrated on preserving warm-water reefs near the equator, perhaps some can be spared for their cold-water cousins. More importantly, attention should be given to the alarming expansion of bottom-trawling fishing vessels with a global reach into areas that have not been fished before.
To mitigate the effects of bottom-trawling on lophelia pertusa and other coral, gear design or type can be altered, marine protected areas established, and fishing efforts reduced using quotas. Nonetheless, change is never easy, and will require compromise on the behalf of the government and fishing corporations, but most of all, compromise on behalf of the consumer, who must be willing to acknowledge the efforts that go into putting fish in the supermarkets.
So maybe the next time you decide to visit the lophelia pertusa, nestled at the foot of a granite wall in Tysfjord, Norway, 700 ft. below the chilly surface of the sea, you can remember all this and look with admiring appreciation upon the three-dimensional fortresses of calcium carbonate that house a hidden kingdom of marine life.
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11 September 2012 “Method in the Madness or Madness in the Method?” (online) Wild Oceans Accessed on June 10, 2020. Available from: https://cumbriawildoceans.blogspot.com/2012/09/method-in-madness-or-madness-in-method.html
Added by Editor, Featured Image: Lophelia pertusa reef (showing the white and orange colour morphs) at 400 m depth off Rost, Norway, the largest known cold-water coral reef on Earth. (Photograph taken on Polarstern Cruise ARK-XXII © Jago/IFM Geomar 2007)