140
Lisa A. LEVIN and Andrew J. GOODAY
there is no increase on the lower slope. Instead, pigment
intensities peak at the shelf edge, decline rapidly to
1200 m, and then remain relatively constant down to
3000 m.
Meiofaunal densities are higher at all depths off Cap
Blanc (21ºN) than off Morocco (35ºN), presumably
reflecting the increased organic-matter input in this
highly productive region. Moreover, the abundance
profiles along these transects are distinctly different,
corresponding fairly closely to pigment concentrations.
At 21ºN, meiofaunal abundances are highest on the
shelf, drop to a distinct minimum at 200 m, followed
by maximum values between 400 and 1000 m and
declining numbers in deeper samples. At 35ºN, high
abundances are also found on the shelf (2656 individuals m
−2 ) and at 400 m (2480 individuals m
−2 )
with a minimum at 200 m (1778 individuals m
−2 ).
However, below 400 m, meiofaunal numbers fall fairly
steeply down to 1200 m (631 individuals m
−2 ), below
which they decline only slightly down to 3000 m
(557 individuals m
−2 ). Meiofaunal biomass along the
Moroccan transect follows a similar trend. Macrofaunal
densities and biomass are also much higher at 21ºN
and 17ºN than they are at 35ºN. The difference is
particularly apparent above a depth of 1000 m. Along
the deeper parts of the two southerly transects, the
decrease in macrofaunal abundance is much steeper
than off the Moroccan coast. Pfannkuche et al. (1983)
also determined rates of benthic respiration and the
activity of the electron transport system (ETS) (a
measure of metabolic activity) along the Moroccan
transect, in both cases using a shipboard technique.
Respiration was highest at 130 m and 400 m, fell
sharply between 400 and 800 m and then decreased
slightly down to 3000 m. Electron transport activity
also decreased with depth, and was substantially lower
than values reported by Christensen and Packard (1977)
from 21ºN, particularly at the shelf and slope sites
above 500 m.
Sibuet et al. (1993), Cosson et al. (1997), and
Gal´ eron et al. (2000) have presented faunal data for
their eutrophic, mesotrophic and oligotrophic EUMELI
stations (sites E, M and O) located at 1700 m depth
on the slope off Cap Blanc, 3100 m on the continental
rise southwest of Cap Blanc, and 4700 m on the Cape
Verde Abyssal Plain, respectively (Fig. 5.1). Densities
of macrofauna (>500 mm) were 5403 individuals m
−2 at
site E and 1856 individuals m
−2 at site M – high values
which reflect the substantial organic-matter inputs at
these stations. In contrast, only 231 individuals m
−2
were recovered at site O. Polychaetes were the most
abundant macrofaunal group (56% at site E, 67%
at site M and 64% at site O) but tanaidaceans
(12.7%, 10.0%, 11.9%), isopods (10.6%, 8.6%, 7.6%)
and bivalves (8.2%, 1.9%, 6.5%) were also important.
The spatial distribution of macrofauna tended to be
patchy at the two shallower stations and particularly
at site E, but much more homogeneous at site O.
Cosson et al. (1997) attributed the aggregated faunal
distributions at site E to the heterogeneous deposition
of organic matter associated with upwelling, strong
near-bottom currents, and the generation of small-scale
sedimentary structure by macrofaunal activity. There
was no evidence for temporal (seasonal) variability
among the macrofauna at either station, although this
may have reflected inadequate sampling. The densities
of other faunal categories followed trends similar to
those for the macrofauna (Sibuet et al., 1993). Densities
of meiofauna (>40 mm; multiple and box-core samples)
were 55.2±4.6, 27.7±2.3, 6.9±0.5 cm
−2 , and those
of megafauna (>2 mm; trawl samples) were 8624,
702 and 33 ha
−1 at sites E, M and O, respectively.
Xenophyophores (giant protists) were an important
component of the megafauna in photographs from
site M (Auffret et al., 1992).
Megafauna on the Northwest African margin have
been sampled using various types of trawl, including
an IOSDL epibenthic sledge equipped with a camera
(Aldred et al., 1976; Rice et al., 1979). Unusually large
populations of megafaunal organisms occur at various
places on the continental slope and rise. At 2000 m
off Cap Blanc (21ºN), sledge catches were dominated numerically by the suspension-feeding anemone
Actinoscyphia aurelia and the irregular spatangoid
echinoid Pourtalesia miranda (Rice et al., 1979). The
anemone is abundant (>1 m
−2 ) in both the catches
and photographs obtained between 1000 and 2000 m
in this area (Aldred et al., 1979). At 4000 m off Cap
Blanc, virtually the only organism visible in bottom
photographs was the xenophyophore Reticulammina
labyrinthica (Rice et al., 1979; Tendal and Gooday,
1981). Individual specimens reached 6 cm maximum
dimension (Gooday and Tendal, 1988), considerably
larger than specimens of the same species from the
Porcupine Abyssal Plain (Gooday, 1996a). Further
north, off the Moroccan coast, the hexactinellid sponge
Pheronema carpenteri occurs in overall densities of
up to 0.17 individuals m
−2 at depths between 740 and
820 m (Barthel et al., 1996). Although considerably
lower than the Pheronema densities recorded in the
Lisa A. LEVIN and Andrew J. GOODAY
there is no increase on the lower slope. Instead, pigment
intensities peak at the shelf edge, decline rapidly to
1200 m, and then remain relatively constant down to
3000 m.
Meiofaunal densities are higher at all depths off Cap
Blanc (21ºN) than off Morocco (35ºN), presumably
reflecting the increased organic-matter input in this
highly productive region. Moreover, the abundance
profiles along these transects are distinctly different,
corresponding fairly closely to pigment concentrations.
At 21ºN, meiofaunal abundances are highest on the
shelf, drop to a distinct minimum at 200 m, followed
by maximum values between 400 and 1000 m and
declining numbers in deeper samples. At 35ºN, high
abundances are also found on the shelf (2656 individuals m
−2 ) and at 400 m (2480 individuals m
−2 )
with a minimum at 200 m (1778 individuals m
−2 ).
However, below 400 m, meiofaunal numbers fall fairly
steeply down to 1200 m (631 individuals m
−2 ), below
which they decline only slightly down to 3000 m
(557 individuals m
−2 ). Meiofaunal biomass along the
Moroccan transect follows a similar trend. Macrofaunal
densities and biomass are also much higher at 21ºN
and 17ºN than they are at 35ºN. The difference is
particularly apparent above a depth of 1000 m. Along
the deeper parts of the two southerly transects, the
decrease in macrofaunal abundance is much steeper
than off the Moroccan coast. Pfannkuche et al. (1983)
also determined rates of benthic respiration and the
activity of the electron transport system (ETS) (a
measure of metabolic activity) along the Moroccan
transect, in both cases using a shipboard technique.
Respiration was highest at 130 m and 400 m, fell
sharply between 400 and 800 m and then decreased
slightly down to 3000 m. Electron transport activity
also decreased with depth, and was substantially lower
than values reported by Christensen and Packard (1977)
from 21ºN, particularly at the shelf and slope sites
above 500 m.
Sibuet et al. (1993), Cosson et al. (1997), and
Gal´ eron et al. (2000) have presented faunal data for
their eutrophic, mesotrophic and oligotrophic EUMELI
stations (sites E, M and O) located at 1700 m depth
on the slope off Cap Blanc, 3100 m on the continental
rise southwest of Cap Blanc, and 4700 m on the Cape
Verde Abyssal Plain, respectively (Fig. 5.1). Densities
of macrofauna (>500 mm) were 5403 individuals m
−2 at
site E and 1856 individuals m
−2 at site M – high values
which reflect the substantial organic-matter inputs at
these stations. In contrast, only 231 individuals m
−2
were recovered at site O. Polychaetes were the most
abundant macrofaunal group (56% at site E, 67%
at site M and 64% at site O) but tanaidaceans
(12.7%, 10.0%, 11.9%), isopods (10.6%, 8.6%, 7.6%)
and bivalves (8.2%, 1.9%, 6.5%) were also important.
The spatial distribution of macrofauna tended to be
patchy at the two shallower stations and particularly
at site E, but much more homogeneous at site O.
Cosson et al. (1997) attributed the aggregated faunal
distributions at site E to the heterogeneous deposition
of organic matter associated with upwelling, strong
near-bottom currents, and the generation of small-scale
sedimentary structure by macrofaunal activity. There
was no evidence for temporal (seasonal) variability
among the macrofauna at either station, although this
may have reflected inadequate sampling. The densities
of other faunal categories followed trends similar to
those for the macrofauna (Sibuet et al., 1993). Densities
of meiofauna (>40 mm; multiple and box-core samples)
were 55.2±4.6, 27.7±2.3, 6.9±0.5 cm
−2 , and those
of megafauna (>2 mm; trawl samples) were 8624,
702 and 33 ha
−1 at sites E, M and O, respectively.
Xenophyophores (giant protists) were an important
component of the megafauna in photographs from
site M (Auffret et al., 1992).
Megafauna on the Northwest African margin have
been sampled using various types of trawl, including
an IOSDL epibenthic sledge equipped with a camera
(Aldred et al., 1976; Rice et al., 1979). Unusually large
populations of megafaunal organisms occur at various
places on the continental slope and rise. At 2000 m
off Cap Blanc (21ºN), sledge catches were dominated numerically by the suspension-feeding anemone
Actinoscyphia aurelia and the irregular spatangoid
echinoid Pourtalesia miranda (Rice et al., 1979). The
anemone is abundant (>1 m
−2 ) in both the catches
and photographs obtained between 1000 and 2000 m
in this area (Aldred et al., 1979). At 4000 m off Cap
Blanc, virtually the only organism visible in bottom
photographs was the xenophyophore Reticulammina
labyrinthica (Rice et al., 1979; Tendal and Gooday,
1981). Individual specimens reached 6 cm maximum
dimension (Gooday and Tendal, 1988), considerably
larger than specimens of the same species from the
Porcupine Abyssal Plain (Gooday, 1996a). Further
north, off the Moroccan coast, the hexactinellid sponge
Pheronema carpenteri occurs in overall densities of
up to 0.17 individuals m
−2 at depths between 740 and
820 m (Barthel et al., 1996). Although considerably
lower than the Pheronema densities recorded in the