126
Lisa A. LEVIN and Andrew J. GOODAY
deeper (>1400 m) parts of the margin. Species richness
was higher in areas with boulders, outcrops and cliffs
than in primarily muddy areas (Hecker et al., 1983).
Surveys of the macrofauna on the North Atlantic
and Mid-Atlantic Bight margins have been carried out
by Wigley and Theroux (1981), Rowe et al. (1974,
1982), and Maciolek et al. (1987a,b). Wigley and
Theroux (1981) reported on a study carried out in
the 1960s of macrobenthic invertebrates (>1 mm) in
the Mid-Atlantic Bight between Boston and Cape
Hatteras at 563 locations, at depths from 4 m to 3080 m.
Macrofaunal densities averaged 293 individuals m
−2
at 400–999 m, 72 individuals m
−2 from 1000–1999 m,
and 46 individuals m
−2 from 2000–3080 m. These
low densities were probably a result of the large
mesh size and sampling bias of the grab samplers
used. Corresponding biomass values were 12, 7 and
8 g m
−2 , respectively. Densities were generally higher
off southern New England than in the New York or
Chesapeake Bight areas. A number of groups, including pogonophorans, thyasirid bivalves, hyalinoecid
polychaetes, selected ophiuroids, and scaphopods, were
most abundant at slope and rise depths.
Rowe et al. (1974) reported average densities and
biomass on the continental slope south of New
England (550–2080 m) to be 3325 individuals m
−2
and 5.93 g m
−2 , respectively. Values for the continental
rise (2425–3923 m) were 789 individuals m
−2 and
0.69 g m
−2 ; values for the abyssal plain (4901–4950 m)
were 175 individuals m
−2 and 0.22 g m
−2 . These slope
values were 3 times the densities and 10 times the
biomass observed at comparable depths by Rowe et al.
(1974) in the Gulf of Mexico.
Rowe et al. (1982) observed that, on the margin off New England, densities and biomass of
macrofauna (>420 mm) showed significant declines
with increasing water depth (r
2 = 0.59, P < 0.01, and
r
2 = 0.56, P < 0.01, respectively). Considerable overlap
was observed between upper-slope assemblages and
those characteristic of shallower waters in the Gulf
of Maine. The sharpest faunal boundaries were observed at depths of 1400–1700 m. Dominant taxa were
oligochaetes (30%) from 203 to 570 m; polychaetes
(Cossura longocirrata and Heteromastus filiformis –
27%) from 1141 to 1437 m; bivalves and polychaetes
(Deminucula cancellata and Poecilochaetus fulgoris –
19%) from 1707 to 1815 m (DOS I), polychaetes,
oligochaetes and aplacophorans (Glycera capitata,
oligochaete spp. and Prochaetoderma sp. – 17%) from
2341 to 2673 m (DWD 106), sipunculans and spionid
and oweniid polychaetes (20%) from 2749 to 3264 m
(Hudson Rise) and scaphopods and the polychaete
Ophelina abranchiata (15%) at 3659 m (DOS II).
Diversity was greatest at mid-slope depths.
Detailed surveys of the macrofauna (>0.3 mm) in the
North, Mid- and South Atlantic Bights were carried
out by the United States Minerals Management Service
as part of an oil exploration effort (Maciolek et al.,
1987a,b; Blake et al., 1985). The North Atlantic Bight
study examined stations between 255 and 2180 m
from the United States/Canada border to the region
south of Georges Bank off New England (Maciolek
et al., 1987a). The Mid-Atlantic Bight study examined
stations from 1500 to 2505 m off New Jersey, near
Dump Site 106, and in a test drilling area (Maciolek
et al., 1987b). The South Atlantic Bight results are
discussed below. Faunas of the North Atlantic Bight
and Mid-Atlantic Bight were remarkably similar. Polychaetes comprised 44–47% of the total macrofauna,
arthropods 22% and molluscs 14%. Sipunculans and
pogonophorans were common as well, particularly at
the 1220–1350 m station in the North Atlantic Bight
and the 2100 m station in the Mid-Atlantic Bight.
Cirratulid, dorvilleid, paraonid and spionid polychaetes
were among the most abundant taxa. Diversities were
maximal at 1220–1350 m in the North Atlantic Bight
and 1500–1600 m in the Mid-Atlantic Bight.
Densities in the North Atlantic Bight ranged from
a high of 18 778 individuals m
−2 at 255 m to a low
of 3078 individuals m
−2 at 2100 m. Dominant taxa
included the bivalve Thyasira ferruginea at 255 m
(overall the most abundant in the North Atlantic
Bight study), the polychaetes Prionospio aluta and
Tharyx spp. at 550 m, the sipunculans Aspidosiphon
zinni and Golfingia (Nephasoma) daphanes at 1220–
1350 m, and the polychaete Aurospio dibranchiata at
2100 m (Maciolek et al., 1987a). In the Mid-Atlantic
Bight (1500–2505 m) dominant taxa were polychaetes
(Aurospio dibranchiata [6.6%], Pholoe anoculata
[4.4%], Tharyx sp. 1 [4.1%], and Prionospio sp. [3%])
and 2 prochaetadermatid aplacophorans [together 7%]
(Maciolek et al., 1987b).
Canyons: The continental margin of the Northwest Atlantic is heavily carved by submarine canyons and gullies. Submarine canyons offer a highly heterogeneous
substratum relative to similar depths on slopes. Several
investigations have focused on the benthic faunas of
these canyons and the adjacent slope areas, often with
differing results. Rowe (1971b) reported that Hatteras
Lisa A. LEVIN and Andrew J. GOODAY
deeper (>1400 m) parts of the margin. Species richness
was higher in areas with boulders, outcrops and cliffs
than in primarily muddy areas (Hecker et al., 1983).
Surveys of the macrofauna on the North Atlantic
and Mid-Atlantic Bight margins have been carried out
by Wigley and Theroux (1981), Rowe et al. (1974,
1982), and Maciolek et al. (1987a,b). Wigley and
Theroux (1981) reported on a study carried out in
the 1960s of macrobenthic invertebrates (>1 mm) in
the Mid-Atlantic Bight between Boston and Cape
Hatteras at 563 locations, at depths from 4 m to 3080 m.
Macrofaunal densities averaged 293 individuals m
−2
at 400–999 m, 72 individuals m
−2 from 1000–1999 m,
and 46 individuals m
−2 from 2000–3080 m. These
low densities were probably a result of the large
mesh size and sampling bias of the grab samplers
used. Corresponding biomass values were 12, 7 and
8 g m
−2 , respectively. Densities were generally higher
off southern New England than in the New York or
Chesapeake Bight areas. A number of groups, including pogonophorans, thyasirid bivalves, hyalinoecid
polychaetes, selected ophiuroids, and scaphopods, were
most abundant at slope and rise depths.
Rowe et al. (1974) reported average densities and
biomass on the continental slope south of New
England (550–2080 m) to be 3325 individuals m
−2
and 5.93 g m
−2 , respectively. Values for the continental
rise (2425–3923 m) were 789 individuals m
−2 and
0.69 g m
−2 ; values for the abyssal plain (4901–4950 m)
were 175 individuals m
−2 and 0.22 g m
−2 . These slope
values were 3 times the densities and 10 times the
biomass observed at comparable depths by Rowe et al.
(1974) in the Gulf of Mexico.
Rowe et al. (1982) observed that, on the margin off New England, densities and biomass of
macrofauna (>420 mm) showed significant declines
with increasing water depth (r
2 = 0.59, P < 0.01, and
r
2 = 0.56, P < 0.01, respectively). Considerable overlap
was observed between upper-slope assemblages and
those characteristic of shallower waters in the Gulf
of Maine. The sharpest faunal boundaries were observed at depths of 1400–1700 m. Dominant taxa were
oligochaetes (30%) from 203 to 570 m; polychaetes
(Cossura longocirrata and Heteromastus filiformis –
27%) from 1141 to 1437 m; bivalves and polychaetes
(Deminucula cancellata and Poecilochaetus fulgoris –
19%) from 1707 to 1815 m (DOS I), polychaetes,
oligochaetes and aplacophorans (Glycera capitata,
oligochaete spp. and Prochaetoderma sp. – 17%) from
2341 to 2673 m (DWD 106), sipunculans and spionid
and oweniid polychaetes (20%) from 2749 to 3264 m
(Hudson Rise) and scaphopods and the polychaete
Ophelina abranchiata (15%) at 3659 m (DOS II).
Diversity was greatest at mid-slope depths.
Detailed surveys of the macrofauna (>0.3 mm) in the
North, Mid- and South Atlantic Bights were carried
out by the United States Minerals Management Service
as part of an oil exploration effort (Maciolek et al.,
1987a,b; Blake et al., 1985). The North Atlantic Bight
study examined stations between 255 and 2180 m
from the United States/Canada border to the region
south of Georges Bank off New England (Maciolek
et al., 1987a). The Mid-Atlantic Bight study examined
stations from 1500 to 2505 m off New Jersey, near
Dump Site 106, and in a test drilling area (Maciolek
et al., 1987b). The South Atlantic Bight results are
discussed below. Faunas of the North Atlantic Bight
and Mid-Atlantic Bight were remarkably similar. Polychaetes comprised 44–47% of the total macrofauna,
arthropods 22% and molluscs 14%. Sipunculans and
pogonophorans were common as well, particularly at
the 1220–1350 m station in the North Atlantic Bight
and the 2100 m station in the Mid-Atlantic Bight.
Cirratulid, dorvilleid, paraonid and spionid polychaetes
were among the most abundant taxa. Diversities were
maximal at 1220–1350 m in the North Atlantic Bight
and 1500–1600 m in the Mid-Atlantic Bight.
Densities in the North Atlantic Bight ranged from
a high of 18 778 individuals m
−2 at 255 m to a low
of 3078 individuals m
−2 at 2100 m. Dominant taxa
included the bivalve Thyasira ferruginea at 255 m
(overall the most abundant in the North Atlantic
Bight study), the polychaetes Prionospio aluta and
Tharyx spp. at 550 m, the sipunculans Aspidosiphon
zinni and Golfingia (Nephasoma) daphanes at 1220–
1350 m, and the polychaete Aurospio dibranchiata at
2100 m (Maciolek et al., 1987a). In the Mid-Atlantic
Bight (1500–2505 m) dominant taxa were polychaetes
(Aurospio dibranchiata [6.6%], Pholoe anoculata
[4.4%], Tharyx sp. 1 [4.1%], and Prionospio sp. [3%])
and 2 prochaetadermatid aplacophorans [together 7%]
(Maciolek et al., 1987b).
Canyons: The continental margin of the Northwest Atlantic is heavily carved by submarine canyons and gullies. Submarine canyons offer a highly heterogeneous
substratum relative to similar depths on slopes. Several
investigations have focused on the benthic faunas of
these canyons and the adjacent slope areas, often with
differing results. Rowe (1971b) reported that Hatteras