Underwater canyons are pretty spectacular geological features that, even when only about 100 miles away, can seem so separate from us. What drew you to researching these special ocean places?
I’ve worked on deep sea coral ecosystems for many years now from Alaska to the Gulf of Mexico and the Norwegian Fjords, but this is the first time I’ve had the opportunity to work in the canyons. This five year multidisciplinary project was funded by the Bureau of Ocean Energy Management, with the overarching goal of mapping and describing ecosystems within the canyons, particularly deep sea corals, that might be vulnerable to energy industry activities.
How did it feel to see real-time imagery of deep-sea corals in Baltimore and Norfolk Canyons?
It’s always an incredible feeling to see animals that live in deep, dark, remote places; most of the time we are the first people to ever see these gorgeous creatures. Most of my earlier work was done using submersibles, which was even better than an ROV screen as you are down there in their habitat at 700m or deeper and looking through a window at giant coral trees a few feet away.
How deep are these canyons?
It varies; the head of Baltimore and Norfolk canyons start on the shelf at around 150-200m and incise the slope down to the abyssal plain at over 2000m. We explored as deep as 1300m in Norfolk Canyon and we could have gone deeper and still been within the canyon, although the walls get further apart as you go deeper and it is unclear where the canyon ends and the abyssal plain begins. Each canyon is different in shape, angle, depth range and topography, and consequently in the type of animals that live there.
Image via NOAA's Okeanos Explorer.
What kinds of dangers do canyons and the plants and animals specially-suited to live in them face?
Canyons are very dynamic places; they have strong and variable currents and often high turbidity (cloudiness) created by suspended organic material and sediment. It is too dark for plant life, but there are many animals that cannot live on the shelf but thrive in the canyons. The high currents clear surface sediments and expose the underlying rock, which provides settlement substrate for colonization by corals, sponges and other sessile benthic animals.
The currents also carry food from the shelf to the deeper parts of the canyon, making them highly productive ecosystems. For animals such as corals, sediment is the biggest problem as their feeding mechanisms and ‘breathing’ surfaces can become easily clogged. Most of the corals were on steep walls and under ledges that do not collect sediment. All the animals in the canyons have adapted to their environment so they can survive in these unusual habitats.
What has been your favorite Mid-Atlantic canyon discovery so far?
I think I have two favorites; the first is the discovery of the cold seeps in Baltimore and Norfolk canyons. We knew the Baltimore seep was there because of information from earlier work by Dr. Hecker who initially described the corals in Baltimore Canyon. She also saw cold seep mussels on her towed-camera film, but by that time she developed the film, she was back on shore.
Image via NOAA's Okeanos Explorer.
The other seep was discovered in 2013, when we dove on some bubble plumes discovered by NOAA during a mapping expedition. That seep is massive and incredibly active, and possibly the largest in the North Atlantic. The second discovery happened on my birthday in 2012; we were exploring a wall in Baltimore Canyon at about 450 m and found colonies of the stony coral. This species forms extensive deep sea coral reefs throughout the North Atlantic and is particularly abundant from North Carolina to south Florida.
To see more of Sandra’s incredible work, check out her table at our Ocean Exploration Day event this weekend!