Priority Ocean Areas for Protection in the Mid-Atlantic
Findings of NRDC's Marine Habitat Workshop
Discussion of Overlapping Priority Areas for Protection
This section describes the overlapping priority areas for protection identified by several participants at NRDC’s workshop. The maps and descriptions of the areas recommended by each individual participant are contained in Part Three.
In the mid-Atlantic there are nine major submarine canyons (from south to north): Norfolk, Washington, Baltimore, Wilmington, Hudson, Veatch, Hydrographer, Oceanographer, and Lydonia. In addition, there is also the Bear Seamount, an underwater mountain just southeast of Lydonia Canyon that is centered near 67 25¢ W and 39 55¢ N and offers similarly diverse habitats.
While much of the canyon bottom is sand, the hard substrate exposed at the heads of canyons and along canyon walls provides habitat for sessile species of sponges, corals, and anemones, which require a hard surface on which to attach. Because the incidence of these populations is restricted by the availability of hard substrate, and because canyons frequently provide the only such features within a wide area, disruptions to canyon environments could significantly impact these species. Some deepwater coral species have exceptionally slow growth rates and do not recover easily from disruptions.
Canyons also provide a refuge for juveniles of commercially important fish and crabs. The heterogeneous habitat provided by hard substrate outcrops and the sessile organisms inhabiting them offer refuge from predators for both juveniles and adults.
Other organisms found in high concentration in the canyons of the mid-Atlantic include cerianthids (Cerianthus borealis), sea pens (Pennatula aculeata), and holothurians (Peniagone sp.).
During the NRDC workshop, Hudson Canyon was cited by several participants as a priority area for protection. Besides being a dynamic environment supporting nurseries for a variety of fish and crustaceans, the head of Hudson Canyon is home to tilefish burrows, which in turn attract secondary burrowing and support a highly diverse community. (See the "Tilefish Habitat" discussion, below.)
Economically important species such as tuna, lobster, and swordfish (some populations of which are overfished) are found in Hudson, Baltimore, and Norfolk Canyons. Norfolk Canyon is noteworthy because it contains what is possibly the southernmost outpost of fauna associated with boreal red coral. This canyon was nominated in 1975 as a marine sanctuary, but was never designated as such.
For more information on submarine canyons, see the discussions, maps, and references provided by Grassle, Hecker, and Musick.
Cape Hatteras, North Carolina, might be called the southern gateway to the mid-Atlantic. Most coastal fauna that migrate into the mid-Atlantic from the south Atlantic pass this point. From the surface to the bottom, out to the 2,000-meter isobath, this area experiences seasonal migrations of cetaceans, sea turtles, and fishes, including sharks.
More than any other single area discussed during NRDC’s workshop, the waters off Cape Hatteras were repeatedly cited for both high biodiversity and high abundance of fauna. In particular, there is an unusually high abundance of benthic fish species. The continental slope off Cape Hatteras receives exceptionally high fluxes of sediment and nutrients that are funneled off the shelf above, helping to account for high abundance of infaunal organisms as well. The incline of the continental slope is particularly steep, and the waters off Cape Hatteras have the steepest temperature gradient of any area off the Atlantic coast.
Located at the convergence of currents, the area around Cape Hatteras encompasses a variety of physical features -- from sandy shoals to deepwater coral systems. The Gulf Stream passes close to Cape Hatteras, making this a hydrographically dynamic area and attracting seasonal concentrations of seabirds, turtles, and other marine wildlife. The hard bottom along the edge of the Gulf Stream, extending toward the South Carolina border, hosts the most northern occurrence of some tropical fish species, such as snapper and grouper. Black sea bass and porgy are among other fish species that concentrate seasonally. The reef also provides winter habitat for loggerhead sea turtles. Crustaceans and other invertebrates tend to colonize these hard surfaces as well.
In addition, floating mats of Sargassum that support an array of sea creatures drift up with the Gulf Stream, which usually meanders between the 100-meter and the 2,000-meter isobaths off Cape Hatteras. The leafy structure of Sargassum provides a nursery environment for hatchling and small juvenile sea turtles and many fishes. Some of the fishes inhabiting Sargassum are prey for larger pelagic predators, making the preservation of this habitat important for the overall sustenance of the region.
For more information on the area around Cape Hatteras, see the discussions, maps, and references provided by Able, Auster, Crowder, Hecker, Knowlton, Lipcius, Musick, and Rader.
Tilefish make their home in the mid-Atlantic from Cape May, New Jersey, to Cape Cod, Massachusetts, generally between the 80-meter and 400-meter isobaths. This area includes the head of Hudson Canyon and has been designated a Habitat Area of Particular Concern (HAPC) by the Mid-Atlantic Fishery Management Council. (See "Submarine Canyons," above, for a discussion of the importance of Hudson and other submarine canyons.)
Beyond supporting an economically significant, though relatively small, commercial fishery, tilefish help to create areas of biodiversity through their unique manner of inhabiting the seafloor. The fish dig funnel-shaped burrows, up to 3 to 4 meters wide and 2 meters deep, attracting secondary burrowing by and providing shelter for lobsters, crabs, and eels. A large number of fish also find overwintering habitat in the same depths as tilefish burrows, including summer, winter, and witch flounder, scup, black sea bass, hake, and squid. Disruption of tilefish habitat would thus affect a range of fish and invertebrate species.
For more information on tilefish habitat, see the discussions, maps, and references provided by Able, Chiarella, Hecker, and Hoff.
During NRDC’s workshop a coastal corridor extending along the length of the study area, 35 kilometers (18.9 nautical miles) from shore, evolved as a priority for protection. Several scientists recommended consideration of all or most of this corridor area (or in one case an even wider corridor), varying from approximately 19 kilometers (10.3 nautical miles) to 56 kilometers (30.2 nautical miles) offshore, to protect migrating right whales, sea turtles, and fish species. Other scientists pinpointed within that corridor specific areas of importance for migration, nurseries and spawning, diversity hot spots, and fish populations of commercial importance. It should be noted that NRDC’s map ends at the 3-mile state-federal boundary, but all of the rationales provided for protecting this area would also support protection into state-regulated waters.
The North Atlantic right whale, one of the most endangered large whale species in the world, feeds in the waters off the Gulf of Maine and Cape Cod during the spring through fall. Mature females migrate south in late fall to give birth off the coasts of Florida and Georgia during the winter, then return north in the spring. Most right whales seen in the mid-Atlantic have been spotted within 32 kilometers (17.3 nautical miles) of the coast, although they travel out to at least 56 kilometers (30.2 nautical miles) from shore, in pelagic waters, between November and April. The already low numbers of right whales are threatened by the busy shipping lanes through which they pass.
A similar broad coastal swath, out to 35 kilometers (18.9 nautical miles) from shore, was identified as a migratory pathway for fish species of commercial and ecological importance, including bay anchovy, bluefish, striped bass, menhaden, summer flounder, shad, sturgeon, and sharks. Additionally, much spawning activity takes place in these coastal waters, and larvae are transported to inshore nursery areas.
Sea turtles also travel seasonally along the mid-Atlantic coast, typically within approximately 19 kilometers (10.3 nautical miles) of shore. The major species involved in this migration include loggerheads, Kemp’s ridleys, and leatherbacks. Their presence seems to be concentrated along the coast from Cape Hatteras, North Carolina, to Cape May, New Jersey.
The coastal waters off North Carolina, south of Cape Hatteras, were noted in the workshop for the degree of spawning activity of a wide variety of both pelagic and benthic fish and crustacean species. The inlets found along this varied coastline offer access to nursery areas for the larvae that drift in and out with the tides. Oregon Inlet in particular (north of Cape Hatteras) offers access to a critical nursery area for crab larvae, including blue and fiddler crabs, between May and October, and for summer flounder larvae from November through March.
Moving north, three similar environments provide nursery areas for crab larvae and spawning grounds for pelagic fish, including summer flounder, menhaden, croaker, spot, and weakfish. These areas are the mouth of Cheseapeake Bay, the mouth of Delaware Bay, and New York Harbor. The area off Delaware Bay was cited as a diversity hot spot as well, containing a representative assemblage of benthic fish species inhabiting the mid-Atlantic, including summer flounder, bluefish, scup, Illex and Loligo squid, dogfish, black sea bass, and monkfish.
The coastal waters off New Jersey were cited by more than one participant as being highly productive habitat for bivalve populations. Upwelling in four areas distributes invertebrate larvae and is thought to increase productivity. About 76 percent of the economically important surf clam fishery, in particular, is supported by populations off the New Jersey coast. The coarse sands off this coast also support a high diversity of organisms, a high abundance of crustaceans, and include certain unusual species.
For more information about this nearshore corridor, see the discussions, maps, and references provided by Able, Auster, Grassle, Knowlton, Lipcius, Powell, Rader, and Watling.
CONTINENTAL SHELF/SLOPE BREAK
In the mid-Atlantic, the relatively flat continental shelf transitions to the steeper slope typically around the 200-meter isobath. The continental shelf/slope break is the point at which this transition from shelf to slope occurs. During NRDC’s workshop, scientists studying quite different marine populations pointed to the continental shelf/slope break area as a priority area for protection. The width, length, location, and depth of their polygons varied, but taken together, their recommendations form a strong argument for considering protection along the entire shelf/slope break area, between the 100-meter and at least the 400-meter isobath.
The benthic waters encompassing the 100- to 400-meter isobaths contain a high concentration of Illex and Loligo squid, and very likely other squid species as well. Illex and Loligo support important commercial fisheries in this area. In addition, squid are an important food source for mammals and for commercially important species such as tuna and swordfish. Illex are present in this area in largest numbers from May through September; Loligo, from October through April.
Loggerhead sea turtles are found in pelagic waters along the shelf/slope break, between the 100-meter and 250-meter isobaths (as well as throughout the mid-shelf region). At present one of the threats to these turtles is longline fishing vessels targeting highly migratory species, particularly swordfish, which often ensnare the turtles by accident.
Many fish species are found in the upper portion of the shelf-break area, from Cape May to Cape Cod. The moderate bottom temperatures there provide habitat for warm temperate species in winter and boreal species in summer.
The pelagic waters of the continental shelf break and upper continental slope, out to the 2,000-meter isobath, contain the highest diversity of marine mammals in the mid-Atlantic EEZ. Shelf-edge cetacean species include sperm, beaked, pilot, sei, and fin whales, and common, Rizzo’s, bottlenose, striped, and spotted dolphins. Some species occupy the entire swath, from Cape Hatteras, North Carolina, to Cape Cod, Massachusetts, while others occur primarily in only the more northern or southern portions of this region. Cetaceans, as migratory animals, tend to reside in these waters seasonally, but different species come and go at different times, amounting to year-round importance.
The shelf-break area off the coast of North Carolina, between the 50-meter and 2,000-meter isobaths, was cited by a number of participants as a hot spot for biodiversity. High benthic diversity of small crustaceans and infauna is found in this area, while a high diversity of both benthic and pelagic fish is also found off this coast. This is due to the steep shelf edge, a convergence of currents, and steep temperature gradients.
Finally, most of the submarine canyons in the mid-Atlantic begin near the break of the continental shelf, at the 100-meter isobath. (See "Submarine Canyons," above, for a discussion of the importance of canyons for marine life.)
For more information about the shelf-break area, see the discussions, maps, and references provided by Auster, Chiarella, Crowder, Kenney, Powell, Rader, and Watling.
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