Saving the Deep

More than two-thirds of coral species reside in deep water, and many are threatened.

For many of us, the ideal coral reef evokes brightly colored coral branches illuminated by sunlight streaming through translucent water, with many fish darting between the coral branches and nearby sea fans. This kaleidoscope of shapes and colors is typically associated with coral reefs in shallow, tropical waters.

Few people know that similar coral ecosystems live quite happily under the darkest deep waters of the ocean. But fishermen have long known about deep-sea corals, because coral fragments often snarl their nets. Scientists have been studying these oases of the deep with recent technological advances in mapping and deep-water exploration. Sadly, just as we are beginning to understand the importance of deep-sea coral ecosystems, destructive fishing practices and ocean acidification are threatening their very existence deep below the waves.

Respecting the Deep
This year is a special one for ocean advocates because it has been designated as the International Year of the Reef (IYOR). Oceana, a global ocean conservation organization based in Washington, D.C., continues to work to protect deep-sea corals from bottom trawling and the ravages of climate change.

Deep-sea corals are among the oldest animals on Earth. They grow just a few millimeters each year and, when undisturbed, live for thousands of years. Like shallow corals, deep-sea corals often form reefs and gardens that serve numerous aquatic species, including fish, by providing a safe haven. Deep-sea corals offer protection from strong currents and predators, nurseries for young fish, feeding areas, spawning areas, resting and breeding areas. Unlike shallow corals, deep-sea corals lack symbiotic algae and can survive at incredible depths that receive virtually no sunlight.

Deep-sea corals thrive in swift currents and are typically found along edges of the continental shelf, seamounts, undersea canyons and ridges. They take many forms. In some species, individual corals grow together to form small bushes or fans. Other species form larger colonies such as reefs. Deep-sea corals make up about two-thirds of all coral species.

Importance of Deep-Sea Corals
Deep-sea corals are essential to the ocean’s health because they help to preserve biodiversity and the long-term survival of commercial and recreational fish species. Rockfish, Atka mackerel, walleye pollock, Pacific cod, sablefish, flatfish and other economically important species in the North Pacific inhabit coral and sponge areas. Areas such as the Oculina Banks, located off the coast of Florida in the Atlantic, also support large numbers of fish, including grouper, bass, jack, snapper, porgy and sharks. Scientific studies corroborate fishermen’s observations that the disappearance of corals impacts the distribution of fish and other ocean wildlife.

Beyond providing the foundation for some of the most prolific ecosystems in the world, deep-sea coral communities may also be valuable to the pharmaceutical and biotechnology industries. Recent discoveries reveal that some corals contain medicinal properties valuable in producing antibiotics, pain killers, and treatments for cancer, AIDS, asthma and heart disease.

On expeditions using remotely operated vehicles (ROVs), scientists have discovered that two-thirds of coral species found in the world’s oceans live in deep or cold waters. These deep-sea corals have been found worldwide, from New Zealand and South America to Africa and Europe’s North Sea.

In the U.S., deep-sea corals grow off every coast, from Maine to Texas, Alaska to California and around the Hawaiian Islands. However, most of the deep-sea corals in U.S. waters have not even been discovered, let alone studied. As a result, they remain largely unprotected from a variety of threats, including destructive fishing gear such as bottom trawlers.

The Bottom Trawling Threat
The practice of bottom trawling involves using large, heavy nets that drag along the ocean floor, leveling everything in their path, including fragile deep-sea corals and anemones, and unintentionally catching a wide swath of marine life.

The base of a trawl net can span more than 150 feet in width and can be lined with “rockhoppers” — heavy rollers that are more than 30 inches in diameter. The larger trawls can drag over a half-acre swath with each pass over an aquatic area, causing extensive damage to the environment with even a single pass. Mounting scientific evidence shows that trawling is one of the most destructive types of fishing because it reduces overall habitat structure and productivity.

Restricting bottom trawling in complex habitats promotes sustainable fisheries. The issue is not whether to stop fishing but whether to allow use of a type of gear as destructive as large roller and rockhopper trawls. The same fish may be caught by hook and line or by fish trap without causing the widespread flattening of habitat or changes in species composition.

It is critical that the remaining pristine areas of structurally complex habitat be protected from damage by trawling gear. It is also possible that stopping the practice of trawling in areas that have already been altered would allow for recovery. Protecting structurally complex habitat would result in a richer diversity of species, a healthier marine ecosystem and more fish for both fishermen and their customers.

The Specter of Acidification
While bottom trawling represents a localized threat to deep reefs, ocean acidification presents a threat to coral reefs at all depths throughout the world. Carbon dioxide emissions affecting the world’s climate are also harming its oceans. The ocean acts as a natural “sink,” absorbing carbon dioxide from the atmosphere. As the oceans absorb more carbon dioxide, they become more acidic, and the acidic waters break down the calcium carbonate shells and skeletons of many essential marine organisms. More than 30 million metric tons of carbon dioxide are absorbed by the oceans each day. If the waters of the oceans become acidic enough, calcium carbonate will simply start to dissolve.

This is an introduction to ocean acidification; for a more in-depth explanation, visit

Ocean acidification affects all corals. By the year 2040, all known deep-sea corals could suffer under marginal growing conditions. And by the end of the century at least two-thirds of all deep-sea corals could live in corrosive waters. It is likely that some deep-sea corals will be damaged by corrosive waters as early as 2020, resulting in a significant reduction in growth rates well before then. If we continue emitting carbon dioxide at current levels, we will likely be responsible for a huge die-off of corals before the end of this century.

Faced with the possibility of coral “osteoporosis,” or the degeneration of coral growths, it is urgent that deep-sea reefs are kept as ecologically healthy and intact as possible while addressing the leading causes of ocean acidification. By reducing or even eliminating localized threats such as bottom trawling, we can improve the resiliency of deep coral reefs. To best protect the deep reefs, we need to aggressively reduce bottom trawling and cut our carbon emissions. You can help by adopting energy-saving practices like those on the IYOR website (, choosing sustainably fished seafood (download Oceana’s seafood guide by clicking on the “Living Blue” tab at and by supporting Oceana’s global effort to protect corals.

Worldwide, more than a million square miles of ocean floor have been protected from destructive trawling, including more than 700,000 square miles of the Pacific Ocean, thanks to efforts led by conservationists all over the world, including Oceana’s team of advocates and scientists. In 2006, federal legislation ensured more research and protection of deep-sea coral habitats. Oceana’s research catamaran, the Ranger, has sailed the Mediterranean Sea since 2005 to scientifically document threats posed to coral reefs and marine creatures.

The Ranger crew’s expeditions discovered deep-sea corals off the coast of Spain and documented areas destroyed by trawling gear. Oceana’s South American office is planning to map and protect deep reefs off the coast of Chile. During 2007 and 2008, Oceana’s marine scientists have begun in-depth research to alert policymakers, business leaders and ocean-loving members of the public about how climate change is threatening healthy oceans. Oceana has also pressured the Environmental Protection Agency to require major reductions of greenhouse gas pollution from large marine vessels and aircraft.

Deep-sea corals may be out of sight for most of us, but we should be mindful of their essential role in protecting the vitality of our oceans, especially for future generations.

Oceana campaigns to protect and restore the world’s oceans. Our teams of marine scientists, economists, lawyers and advocates are instrumental in winning specific and concrete policy changes to reduce pollution and to prevent the irreversible collapse of fish populations, marine mammals and other sea life. For more information, please visit For more information about the International Year of the Reef, visit

Article Categories: