News and ResourcesDeep-Sea Corals: Deep Sea Treasures - June 28, 2015
When most people think about coral and coral reefs, they usually think about crystal clear, warm waters with hundreds of fish and aquatic animals, all of which live in or on brightly colored corals. These coral reefs are usually in some tropical locale, just off the pristine white sand beach of some isolated island. And while these coral reefs are certainly important, and very beautiful, they are not the only places to find coral in our oceans.
Over the past few decades, scientists have delved deep in search of deep-sea corals, corals that live and grow under hundreds, if not thousands, of feet of water and with almost no natural light at all. Deep-sea corals are weird, but beautiful, organisms that we have discovered hidden in some of the strangest parts of our oceans and each dive we take to find these corals, we learn a little bit more about them and their environment.
Deep-sea corals, as the name implies, live in the deeper waters of our oceans and mostly out of the euphotic zone, the top few meters of the water column that actually receive sunlight. In general corals, colonial or individual organisms made up of tiny coral polyps that are usually in a symbiotic relationship with algae species, need light to live and grow. We thought that corals like to live in places with sufficient sunlight, not to much silt or suspended solids, and where the water temperature is warm, preferably between 77° to 84° Fahrenheit. Therefore, it was a big surprise to scientists and researchers to not only find these deep-sea corals under hundreds of feet of water, but also that these deep-sea coral communities appeared to be thriving.
Corals in general are very slow growing, which means that the amazing coral reefs we see today have been growing for hundreds, if not thousands, of years. Even in ideal conditions, corals might only grow a few centimeters a year, and reefs depend on both hard and soft corals to grow and thrive.
Hard corals are what we call the “reef-building” corals. These corals have hard, calcium carbonate based skeletons which provide the base for the coral polyps. Even though coral seems to live forever, it is really a colonial organism, being made up of individual coral polyps connected by a thin layer of living tissue on the outside of the skeleton. Each coral polyp consists of one sea-anemone like organism that has a varying amount of tentacles for feeding, based on species, and shallow-water coral species have symbiotic algae within the coral to help provide energy and nutrition.
Hard corals are the bases on which coral reefs are built and provide habitat and substrate for other animals and plants to use. Living polyps will grow on the outside of the coral and will grow the coral structure by adding new layers to the calcium carbonate skeleton below, so that the polyp tentacles can reach out farther to gather food. Once you get past the initial layer of living hard coral tissue, most of it is dead calcium-carbonate skeleton underneath.
Soft corals are not “reef-building” corals, however they are still very important habitat and shelter for aquatic animals. Soft corals lack the ability to create sturdy calcium carbonate skeletons like hard corals, and therefore tend to be much more flexible and free-form. These corals are sometimes mistaken for seaweed, algae or other submerged aquatic vegetation, as they can be very graceful, large and colorful.
Even though it seems hard to believe, deep-sea corals are just as colorful, large, diverse and amazing as their shallow-water cousins. Even though we still have yet to explore much of the ocean depths, already scientists have discovered over 3,300 different species of deep-sea corals and that number continues to grow each year. Thus far we have found deep-sea corals in many of the world's oceans, even in freezing cold waters that can be around 30° Fahrenheit. And the diversity of species is tremendous for deep-sea corals; they can come in many colors like red, purple, orange, yellow and more, and can range in size from a single grain of rice to a towering structure up to 35 feet high or a reef stretching over 25 miles.
Because of the nature of their environment, searching for deep-sea coral can be painstakingly arduous, however scientists and researchers have found a plethora of coral and reefs right along the Atlantic coast of the U.S., including off the coast of Maryland. Most of the larger coral colonies tended to be found in the submarine canyons located off the Atlantic coast, such as the Baltimore, South Vries, Warr and Phoenix Canyons.
In order to preserve these areas, the Mid-Atlantic Fishery Management Council is currently working on a Deep Sea Corals Amendment to the Mackerel, Squid, and Butterfish Fishery Management Plan that would help to protect areas that are known or highly likely to contain deep-sea corals. As of June, the Deep Sea Corals Amendment has been approved by the Mid-Atlantic Fishery Management Council and is ready to be submitted to the U.S. Secretary of Commerce. This historic piece of legislature could be key to the longterm health and future of these crucial deep-sea coral colonies.
Harrison Jackson is the Coastal Stewards Coordinator for the Maryland Coastal Bays Program.
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