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Deep-Sea Coral Ecosystems

Image credit: Lophelia II Reefs, Rigs, and Wrecks Expedition 2009

Deep-sea coral ecosystems are communities of reef-building corals, black corals, sea fans, and sea pens that thrive in deep, cold water (> 50 meters depth). They are azooxanthellate, meaning they lack the ability to photosynthesize and do not depend on the sunlight for energy. Instead, they rely on food strained from the water, and particles “raining” down from the surface.

Deep-sea coral occurs throughout United States waters, from New England to Alaska, and across the Pacific. We think they are widespread where suitable bottom types occur, but they are poorly understood and only recently explored. Sophisticated technologies like multibeam echosounders, manned submersibles, remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) are required to access and sample deep-sea coral environments.

Why are they Important?

Deep-sea corals provide essential habitat and refuge for fish, crabs, shrimps, lobsters, among other invertebrates. As such, they help sustain commercial fisheries and fishing communities. Spot prawns, sablefish, rockfish, thornyheads, and golden crabs are a few of the market species commonly observed in deep-sea coral environments.

Deep-sea corals themselves are culturally and economically important. Black coral is the state gem of Hawaii where the tree-like coral colonies are harvested for jewelry. In 2007 Hawaii’s black coral fishery was valued at an estimated US$33 million. Around 1000 people were involved in the fishery, including coral divers, manufacturers and salespeople. Deep-sea corals and sponges also have the potential to provide novel materials and life-saving drugs that support human health and welfare.

These corals also help us study age, growth, and climate change in the deep-sea. Individual colonies can be hundreds to thousands of years old. They have growth rings like trees that scientists use to ‘look back in time’ using chemical signatures.

What Threats do Deep-sea Coral Ecosystems Face?

Natural threats include sedimentation, disease, and predation and invasive species. Man-made threats include bottom-contact fishing gear, directed harvest, oil drilling, submarine cabling operations, human induced sedimentation, changing ocean temperatures, and water chemistry. Because deep-sea coral colonies are fragile and extremely slow-growing, damaged habitats would require many years to recover. It is preferable to avoid extensive damage to these ecosystems altogether.

What We Are Doing

NCCOS is identifying where deep-sea corals and sponges occur and building a national geo-database. We are developing models that predict the places where deep corals are most likely to grow. This helps NOAA focus mapping and exploration efforts.

We also conduct field surveys of deep-water habitats, providing crucial scientific data and analyses of ecosystem diversity, health, and condition that support coastal ecosystem management.

NCCOS field research helps regional fisheries management councils to identify essential fish habitat in the South Atlantic and Pacific, and lends support to the Natural Resource Damage Assessment for the Deepwater Horizon oil spill in the Gulf of Mexico.