The Mysterious World of Deep-water Corals
Watch the video above, Habitat Exploration: Deep-Sea Corals, featuring NOAA Fisheries zoologist and deep-water coral expert Martha Nizinkski>>>
NOAA Fisheries zoologist and deep-water corals expert Martha Nizinski explores the little-known ecosystems of the continental shelf.
Martha Nizinski was more than 400 meters below the surface, moving slowly among the strange life forms of the deep sea, when something large crashed against her submersible. She and three other scientists were exploring the continental slope off the Carolinas, and whatever rear-ended them was in a blind spot behind the vehicle. For a few tense moments, she couldn’t see what it was or what it wanted.
That was Nizinski's first voyage to the bottom of the sea.
Nizinski had recently received her PhD when the scientists planning that expedition recruited her. They needed an invertebrates expert, so they offered Nizinski a coveted spot in the cramped sphere of the submersible.
"It was the turning point in my career," Nizinski said. "I was hooked," despite the close encounter with what turned out to be a swordfish—and a big one. Swordfish don’t have many predators, and they tend to be bold.
Today Nizinski is a zoologist at the NOAA Fisheries National Systematics Lab, which is housed in the Smithsonian Museum of Natural History in Washington, DC. Her office is packed with shelves of deep-sea crustaceans preserved in alcohol, their articulated appendages pressing against the curved glass of their jars. Because she plies her trade in the least explored ecosystem on the planet, Nizinski and her colleagues occasionally discover a new species. With her co-authors, Nizinski has named one starfish and one shrimp that live in the near total darkness of the deep. They have also found at least five new species of crustaceans still awaiting description.
An Unexplored World
"Deep sea habitats are prime areas for finding new species because they haven't been fully explored," Nizinski said. "We know less about the deep sea than we do about the Moon, or even Mars."
Thanks to Nizinski and her colleagues, that’s beginning to change. With funding from NOAA’s Deep Sea Coral Research and Technology Program, Nizinski and other scientists have been exploring the canyons that cut into the continental shelf between the mid-Atlantic and the New England states. Their goal is to find and map deep-water coral communities—biodiversity hotspots that are important habitat for some valuable species of fish.
One of the main threats to fragile and slow-growing deep-water coral colonies is bottom-tending fishing gear. For instance, when bottom trawls damage coral habitat, it can take hundreds of years for the area to recover, if it recovers at all. Because these areas provide important habitat, fishery managers are looking for ways to protect them.
Last summer, NOAA’s research ship Okeanos Explorer set out to explore the deep-sea canyons off the coast from Virginia to Maine, with Nizinski as one of two lead scientists onboard. On this expedition, scientists didn't go down in submersibles. Instead, they piloted a remotely operated vehicle (ROV) from the ship. ROVs are safer and less expensive than manned submersibles, and they can also stay at depth for much longer periods of time. In this case, they dove below 3,000 meters.
"We found areas that had corals meters tall," Nizinski said. "Corals grow very slowly, so those could be hundreds, even thousands of years old."
Predictive Models Are the Cutting Edge of Corals Research
Locating deep-water coral colonies on the vast frontier of the continental slope isn't easy. "Deep sea research is expensive," Nizinski said. "You don't want to just drop in and wander around hoping you'll find something."
To help find coral colonies, NOAA scientists are developing habitat suitability models that predict likely coral-bearing sites. Areas with swift currents are good places to start. That’s because deep-water corals, unlike their shallow-water cousins, don’t have zooxanthellae, the symbiotic algae that produce nutrients from sunlight to feed their coral hosts. Because deep-water corals live in total darkness, they have to feed themselves by capturing food out of the swift-moving currents washing over them.
Scientists also consider depth and substrate type when considering where corals are likely to be found. What other indicators point to likely deep-water coral habitat? “That’s what we’re trying to figure out,” Nizinski said.
The Okeanos expedition mapped out new deep-water coral communities. More importantly, by ground-truthing the habitat suitability models, Nizinski and her colleagues increased the ability of scientists to predict the location of deep-water corals based on environmental data.
"The information we gathered on the Okeanos cruise increased exponentially what we know about the distribution, abundance, and diversity of deep-sea corals on the Northeast continental shelf and slope,” Nizinski said.
With this new information, it may soon be possible for fishery managers to propose discrete and tightly focused areas for protection from fishing trawls while still allowing fishermen access to the rest of the shelf.
And doing that requires more trips to the bottom of the sea. “If you want to protect something,” Nizinski said, “you have to know where it is.”
Deep-water coral research is a collaborative effort across NOAA Fisheries, NOAA Research, and NOAA Ocean Service.