Greater protection needed for US underwater canyons

The United States has one of the largest exclusive economic zones in the world. The area of the ocean under our jurisdiction is nearly one and a half times larger than the continental U.S., making it effectively an “underwater United States” hidden beneath the waves, but still within our borders.

Like the land, the underwater U.S. holds a staggering array of features, ecosystems and organisms, almost all of which are beyond view. However, that does not mean these areas are safe from activities on land or on the ocean surface.

The continental shelf off the East Coast is a perfect example. When the glaciers receded at the end of the last Ice Age, runoff from the melting ice carved steep canyons into the continental shelf, in some places stretching more than 400 miles into the abyssal plain. 

In 2012, partly in response to damage caused by the Deepwater Horizon oil spill to deep-sea coral ecosystems in the Gulf of Mexico, we began conducting surveys with the National Oceanic and Atmospheric Administration (NOAA) to document what lies within U.S. territorial waters off the mid-Atlantic and Northeast Coast. The concern was that we might not know what we could lose if an oil spill occurred elsewhere along our coastline.

We discovered more than 90 canyons between the Carolinas and the Canadian border. Most are deeper than the Grand Canyon and almost any of them could be a national park if they were on land. The complex current that flows through underwater canyons can create a nutrient-rich upwelling and mixing that makes life remarkably diverse to these parts of the ocean.

Unlike most shallow reef corals, deep-water corals are entirely filter feeders that grow up and out into fans that trap organic material carried by currents. They create reef-like structures, or large clusters, that provide habitat for more than 3,000 species worldwide, many of them commercially important. In addition, these corals could prove to be biomedical resources.

Studies are being conducted to show whether they can treat more than 20 human diseases, including cardiovascular disease, leukemia and osteoporosis. In all, we documented 75 species of coral in the Atlantic canyons, about 30 percent of which are new to science.

The corals and the ecosystems they support sustain biodiversity and provide critical habitats for ecologically and commercially important species, including more than 50 species of fish and 23 species of whales and dolphins. Losing these hidden oases would threaten our East Coast fisheries,  which yield billions of dollars annually. 

Like many marine species and ecosystems, deep-water corals are highly vulnerable to changes we see occurring around the world and especially along the East Coast. The Northwest Atlantic, particularly the Gulf of Maine, is expected to warm faster than almost any other part of the Atlantic in the coming decades. In addition, declining pH (also known as ocean acidification), fishing and marine debris are exacerbating the damages caused by climate change.

The characteristics of these corals compound their vulnerability. They can live for hundreds — even thousands — of years, but once disturbed they do not readily recolonize the same patch of seafloor. In addition, they are extremely brittle and grow only fractions of a millimeter per year. A single errant trawl, like one we saw near the New England Seamounts, or an oil spill a fraction of the size of Deepwater Horizon could wipe out ecosystems that have required centuries or millennia to grow. 

Only three major canyons on the East Coast — Oceanographer, Gilbert and Lydonia, located just 100 miles from Manhattan — enjoy some level of protection as part of the Northeast Canyons and Seamounts National Monument, the only marine monument in North America. In fact, only about 3 percent of U.S. waters are protected to a level that restricts extractive activity, compared to about 13 percent of our lands. Until the canyons along the U.S. East Coast can be systematically explored and studied, these places that are shining examples of our natural and cultural heritage are in need of greater protection and science-based management that is sustainable. 

Timothy Shank is a deep-sea biologist at the Woods Hole Oceanographic Institution on Cape Cod.