For the first time in decades, researchers have conducted an extensive exploration for deep-sea corals and sponges in submarine canyons²（峡谷） off the northeastern coast of the US. The survey revealed coral "hotspots," and found that a new coral habitat suitability model could help predict where corals are likely to occur. The model is being developed by the Northeast Fisheries Science Center (NEFSC) and the National Ocean Service's Biogeography Branch. Among the canyons surveyed during the July 6-18 cruise aboard the NOAA Ship Henry B. Bigelow were Toms, Middle Toms, and Hendrickson canyons off New Jersey³, and Veatch and Gilbert canyons off Georges Bank. All of these were known or suspected habitats of deep-sea corals. More than 70 deepwater canyons, ranging in depth from 100 meters (about 330 feet) to more than 3,500 meters (about 11,500 feet), exist along the Northeast US continental⁴ shelf and slope. Few are well studied.

 

"The deep-sea coral and sponge habitats observed in the canyons are not like those found in shallow-water tropical reefs or deep-sea coral habitats in other regions," said Martha Nizinski of NEFSC's National Systematics Laboratory in Washington, DC, a zoologist⁵ and deep-sea coral specialist who served as the chief scientist on the recent research cruise aboard the NOAA ship Bigelow. "We know very little about the distribution and ecology of corals in the canyons off the Northeast coast," she said. "Although our explorations have just begun, we've already increased our knowledge about these deepwater coral habitats a hundred times over."

 

Findings from this cruise will not only improve knowledge about deep-sea life off the Northeastern US, but will also aid the New England and Mid-Atlantic fishery management councils in their efforts to manage these habitats, which support a variety of fish species and other marine¹ life.

 

The July survey on the Bigelow was the culmination⁶（顶点，高潮） of a larger mission to explore deepwater canyons, and gain increased knowledge of deep-sea corals. The Bigelow was one of three NOAA ships involved in the Atlantic Canyons Undersea Mapping Expeditions (or ACUMEN), which has been used to document the deepwater canyons on the continental shelf and slope from Norfolk, Virginia, to New England. During February-June 2012, the NOAA ships Okeanos Explorer and Ferdinand R. Hassler extensively mapped offshore⁷ areas designated as priorities by the NEFSC deepwater coral research team and external partners.

 

Using high-quality multibeam sonar maps, NEFSC scientists and collaborators explored the deepwater canyons in the Northeast. Cruise objectives included gaining a better understanding of deep-sea coral diversity and distribution in the region, and testing the accuracy of a habitat suitability model to predict where deepwater corals exist in the Northeast.

 

Bottom topography, as well as various other environmental factors, historical coral records, and model predictions helped guide the search and sampling of coral habitats. The science team aboard the Bigelow, using TowCam, a towed deep-sea digital imaging system operated by researchers from the Woods Hole Oceanographic Institution (WHOI), was then able to photograph what was on the bottom at the sites they chose, which is important for groundtruthing the modeling data.

 

Many corals observed during the Bigelow cruise live at depths between 200 and 2,000 meters (roughly between 650 and 6,500 feet deep). Although no specimens⁸ were collected during this expedition, more than 38,000TowCam images will be analyzed⁹ in the coming months. Data derived¹⁰ from these images will be used to evaluate the presence or absence of corals in areas having historical records; to quantitatively¹¹ verify the habitat suitability model; and to enhance knowledge of the diversity and distributions of deep-sea corals in the region. These data will also provide the baseline information for a three-year research effort in the Northeast funded by NOAA's Deep-Sea Coral Research and Technology program.

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