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Regional Overview & Fact Sheet
The Northern Gulf Stream Transition Region—a region of open ocean in North Atlantic lying adjacent to and affected by the Gulf Stream to the east, the Labrador Current to the north and west, and the Acadian and Virginian Atlantic Regions (the neritic regions) to the west—is an important and highly productive region for over 250 fish species, including bluefin tuna and Atlantic white marlin. Extending from waters off of Cape Hatteras to north of the Grand Banks, the waters of the region do not border any continental landmass, but overlay several important bathymetric features of the northwestern Atlantic, such as the Canyon Lands, Pickett Seamount and the New England Seamount chain. This once remote marine region is becoming increasing under pressure from fishing due to new technologies and equipment.
Fact Sheet
Characterized by current and sea surface temperature influence from the adjacent Gulf Stream, including moderated water temperatures and the frequent presence of warm core and cold core rings; a pelagic area offshore of the NW Atlantic extending from the shelf break to the EEZ and Cape Hatteras where the Gulf Stream diverges north east.
10–18°C (winter), 12–25°C (summer)
Warm core rings formed from the Gulf Stream, adjacent.
One of the few non-coastal regions, this ecoregion extends from shelf break to the deep ocean.
shelf (roughly 0–200 m): 0%
slope (roughly 200–2,500/3,000 m): 45%
abyssal plain (roughly 3,000+ m): 55%
deep ocean benthos, pelagic fisheries, deepwater gorgonian corals, octocoral gardens
Moderately high productivity ecosystem (150-300 gCm-2yr-1).
sperm whale, fin whale, humpback whale, North Atlantic right whale, loggerhead turtle, leatherback turtle, Atlantic white marlin, Atlantic cod, silver hake, Great northern tilefish
Overfishing has affected some species. For instance, the Atlantic white marlin, found throughout the western Atlantic usually above the thermocline in deep pelagic waters, is a victim of overfishing and current stocks are 5–15 percent of carrying capacity. Bluefin and bigeye tuna have also been heavily overfished in the region.
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Physical and Oceanographic Setting
The Northern Gulf Stream Transition Region, lying east of regions 7 and 8, begins at the shelf break and extends seaward over North Atlantic deep waters. The region is composed of Gulf Stream-influenced Atlantic water and steep bathymetry extending from 200 m at the shelf break to nearly 4,500 m at the abyssal plain. At the western edge of the region is the locus of the Canyon Lands—a series of steep canyons, extending from the top of the shelf break through the slope to the abyssal plain. Though the region is not within the Gulf Stream current (the Gulf Stream is south and east of the region), it is strongly influenced by it, and is prone to anti-cyclonic warm core eddy incursions, which spin off of the Stream and meander westward to the shelf break. These warm core rings can be as large as the state of Massachusetts and carry parcels of warm water far northward of their general provenance. Sea surface temperatures of the region can range in January from 10°C at the cold western edge to 18°C at the eastern boundary with the Gulf Stream. In summer, surface temperatures range between 12º and 25°C. Sediment types of the region are mostly silts and clays delivered from the continental land mass.
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Biological Setting
Over 250 fish species have been recorded in this important and highly productive area. The deep waters of this region are home to high densities of bluefin tuna and white marlin. Great northern tilefish congregate on the continental slope to depths of 500 m, and Northern Atlantic right, fin, humpback and sperm whales migrate throughout the region. Several species of sea turtle, including the loggerhead, and leatherback, as well as common, Risso’s, bottlenose and Atlantic white-sided dolphin are also commonly observed in this region. The region also represents one of the major breeding areas for the gray seal in eastern North America. Atlantic herring, cod, mackerel, hake and pollock are abundant. These offshore waters are important areas for several avian species, including northern fulmars, storm-petrels, alcids, shearwaters and gannets.
Because the region is a transition zone between the warm tropical waters to the south and the cold Labrador Current to the north, there is often a large migratory component to the species composition of the fish communities. Many of the residents are eurythermic tropical or warm-temperate forms migrating from the south for periods when the water temperature is high. Thus, while species diversity is high, relatively few species are endemic to the area.
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Human Activities and Impacts
The Northern Gulf Steam Transition Region encompasses a vast distance, much of which is threatened by overfishing. Where much of this region was not greatly exploited by fishing in the past, new technologies, such as remotely operated vehicles, video, sea surface temperature images, bottom landers, submarines and sonar, as well as sturdier winches, stronger cable, and more powerful engines have allowed fishing trawlers to extend their reach to depths of 900 m and beyond. Moreover, because: a) fishing effort is more difficult to control on the high seas and b) deepwater species are slower growing, longer lived and reproduce later in life, deepwater fisheries are not particularly sustainable. While proposals are being developed to ensure the protection of habitat and sustainability of pelagic fisheries, it is generally accepted that the open water areas are underrepresented and unprotected in much of the northwest Atlantic. Bycatch is also an issue for the Northern Gulf Stream Transition Region. As within the Gulf of Mexico, incidental take and entanglement of sea turtles and other species occurs in this area. Moreover, the US Navy sonar exercises also likely affect many marine species (NRC 2003).
This area is also affected by pollution—particularly plastics and hydrocarbons that accumulate in driftlines and at convergence zones. Fish and crustacean eggs and juveniles, as well as juvenile sea turtles and even adult seabirds are affected.
Level II and Level III Descriptions
Level II captures the break between neritic (near shore) and oceanic areas and is determined by large-scale physiography (continental shelf, slope, and abyssal plain, as well as areas of oceanic islands and major trenches, ridges and straits). This level reflects the importance of depth as a major determinant of benthic marine communities as well as the importance of major physiographic features in determining current flows and upwelling. Like Level I, it extends from the coasts to the EEZ.
Level III captures differences within the neritic realm and is based on more locally significant variables (local characteristics of the water mass, regional landforms, as well as biological community type). Level III is limited to the continental shelf, since only this area has sufficient information for finer-scale delineation.
Level II and Level III Ecoregions
Other Marine Ecoregions
Marine ecoregions are areas of general similarity in terms of physiographic, oceanographic and biological characteristics, which fall within the Exclusive Economic Zones of the North American countries. There are 24 marine ecoregions in North America.
