Regional Overview & Fact Sheet
The Gulf Stream Region is defined and dominated by the Gulf Stream current—a river within the ocean. This offshore region sees many migrating species such as the humpback whale and bluefin tuna, and is home to the only known North American population of wreckfish. Due to the interaction of the Gulf Stream with bathymetric features such as the Charleston Bump, upwelling occurs, enriching surface waters downstream of the Bump. The region starts from the Straits of Florida at its southern extreme, and continues northward and seaward of the coastal Atlantic Bight following the Gulf Stream current to the Outer Banks of North Carolina and Cape Hatteras, where the region terminates as the current veers northeastward (out of the region of study). The region includes sections of the slope, abyssal plain and several ecologically important bottom features.
Defined by the Gulf Stream, a large, predominantly northeastward flowing current.
avg. 23°C (winter), 27–30°C (summer)
Gulf Stream, upwelling along shelf break.
From shelf break to the deep ocean, including Blake Plateau, and deep seamounts.
shelf (roughly 0–200 m): 0%
slope (roughly 200–2,500/3,000 m): 59% including the Blake Plateau
abyssal plain (roughly 3,000+ m): 41%
deep silt and basalt seamounts
Deep ocean benthos, open water nekton communities.
Benthic community types including deep-sea Lophelia coral banks.
Moderately high productivity ecosystem (150-300 gCm-2yr-1). Upwelling along the Gulf Stream front and intrusions from the Gulf Stream cause short-lived plankton blooms.
fin whale, Humpback whale, North Atlantic right whale, sperm whale, leatherback sea turtle, silver hake, Atlantic white marlin, tilefish, Oculina varicosa coral, groupers, Great Northern tilefish
Overfishing is a major threat—current stocks of the white marlin are 5–15 percent of carrying capacity.
Physical and Oceanographic Setting
Region 10 represents the Gulf Stream flow along the southeast US coast—the point where the Stream approaches continental North America most closely. The Gulf Stream forms the western boundary current of the North Atlantic subtropical gyre, flowing offshore up to 2,000 m deep, and following along the edge of the continental shelf. This current, often described as a river within the ocean, is up to 320 km wide, with a core about 144 km in width, and carries warm tropical waters poleward at velocities of up to 2 m per second. The current forms from the Florida Current, emanating from the Gulf of Mexico, and forms a jet between the continent and Cuba and the Bahamas that boosts the current’s speed along the Florida coast. Along the western wall of the current, eddies often form and spin off in a northerly direction to form warm core rings that enter the adjacent Northern Gulf Stream Transition Region. These oceanographic features, which can be many kilometers in diameter, carry semi-tropical fauna into the cold reaches influenced by the Labrador Current.
The bathymetry of the region incorporates two distinct areas. In the northern section, beyond the wide continental shelf off Virginia and North Carolina, the region’s sea bottom slopes steeply to a deep abyssal plain. In the southern section, the shelf of the adjacent region leads to a sharp but relatively shallow drop (200–1,000 m) to the immense Blake Plateau—an area that is about three times the areas of the adjacent shelf. East of the Blake Plateau, the slope drops off steeply to the abyssal plain at a depth of approximately 5,000 m. Sediments are composed of silty clays. Sea surface temperatures range from 23° C in winter to 27–30° C in summer.
The biology of this region is similar to, and in many ways a continuation of, region 9 to the north. The deep waters support high densities of bluefin tuna, white marlin and tilefishes on the continental slope. The Charleston Bump/Blake Plateau area is also home to the only known North American population of wreckfish—a slow-growing, late-age maturing and long-lived species that prefers deep reef habitats. In fact, this area is the only documented spawning area for the fish in the North Atlantic. The North Atlantic right, fin, humpback and sperm whales as well as the leatherback sea turtle migrate throughout the region, its southern section representing the southern limit of many of these whale species. Because the Gulf Stream current governs much of the biology of the region, and also because the current is maintained offshore by the shallow continental shelf barrier, the biology of this region is very different from that of the adjacent Carolinian Atlantic Region. The Gulf Stream carries water of moderate temperature far north of this region’s limit, extending the range for many subtropical species such as dolphinfish, wahoo, butterflyfish, wrasses, and goatfishes.
The interaction of the current with the shelf edge, and with bathymetric features such as the Charleston Bump at the South Carolina/Georgia border, causes upwellings to occur, enriching the surface waters downstream (north) of the feature with nutrient rich deeper water. Consequently, the waters around the Bump are very productive, with a complex food web supporting one of the most popular fishing areas of the South Atlantic Bight (in region 11, adjacent). The eddies generated by the motion of the current past such bathymetric features are an important means of transporting reef fish northward to shelf habitats off North and South Carolina.
Below the Gulf Stream, an extensive system of deepwater coral banks, dominated by Lophelia and Dendrophelia, form reefs on and below the shelf break. In particular, stony corals (Lophelia pertusa and Enallopsammia spp.) are found in the Straits of Florida and on the Blake Plateau off North Carolina, South Carolina, Georgia and Florida. These structures support a high diversity of fish and macroinvertebrate species, and appear to be the most extensive reef formations known from the northwest Atlantic
Human Activities and Impacts
A number of commercially and recreationally important fisheries occur along the edge of the Gulf Stream, where the current interacts with the shelf break creating upwelled hotspots of high biological productivity. Tuna (bluefin, bigeye) is caught in abundance in this region, as is the white marlin, Atlantic croaker and various species of tilefish. There is concern over overfishing (swordfish, in particular) and bycatch of untargeted species (such as undersized swordfish, marlin and sailfish) in the region, around the Charleston Bump in particular. Recreational and commercial fishing, as well as commercial shipping carries many vessels through the region, creating the potential for severe damage to the ecosystems. For example, fishing activities have destroyed the Oculina or ivory bush coral reefs offshore of the north coast of Florida. Ivory tree coral, a very slow-growing deepwater coral, is fragile and very difficult to re-establish once damaged. Fishing of the reef fish—grouper, wreckfish—and for migratory pelagic species has decimated large parts of the reef over the years. To aid in recovery of this unique and ecologically important habitat, a large portion of the area was closed to fishing in 1994 as the Oculina Bank Habitat of Particular Concern, the first deepwater site to be granted such protection in the eastern United States. The reef is currently protected in the shallowest part of its range, but much of the remaining reef exists at or beyond the shelf break (and overfishing of long-lived groupers still occurs).