THE DEEP-SEA FLOOR: AN OVERVIEW
13
which moves into the collecting bag. Sleds collect
macrofauna in large numbers, supplying specimens for
research in which properties of each individual must
be determined – for example, studies of reproductive
biology, biomass distribution, and taxonomy. Sleds do
not collect every individual in their path in the layer
to be sampled because the mouth of the bag clogs
with sediment as the sled moves along the seabed
(Gage, 1975), so sleds are inappropriate for quantitative
studies. They can also damage delicate specimens (e.g.,
the legs of isopods tend to be broken off) and cannot
sample macrofauna living at greater depths than 1–
2 cm.
The deep-sea-floor ecosystem extends into the nearbottom water because some animals living in or on
the seabed make excursions into the near-bottom water,
and some animals living in the water just above the
seabed interact with the seafloor. Hyperbenthic sledges
(see also Rice et al., 1982) have been developed to
sample the near-bottom water. Such sledges consist
of runners and a frame supporting a vertical array of
opening–closing nets (Dauvin et al., 1995; Fig. 2.10).
A
B
C
D
E
F
Fig. 2.10. The hyperbenthic sled, a device for collecting deep-sea
animals in the waters just above the seabed. The device is 1.51 m
tall. A, Attachment point for the cable to the ship; B, frame; C, mouth
of a sampler; D, net; E, sample container; F, runner. Modified from
Dauvin et al. (1995). Copyright: Elsevier Science.
The usual limitations of plankton nets apply to these
samplers (e.g., bias in collections owing to differences
in avoidance behavior among species, variable filtering
efficiency resulting from net clogging). In addition, the
frame may put animals from the seabed into suspension
and thus cause them to be caught, particularly in the
lowest net. Despite their limitations, these samplers
provide access to an understudied component of the
deep-sea fauna (see also Wishner, 1980).
Despite their limitations, most of the taxonomic,
systematic, and biogeographic research on the deepsea fauna has been based on the large collections
that trawls, sledges, and sleds provide (Hessler, 1970).
This research has resulted in discoveries regarding, for
example, the high diversity of the deep-sea-floor fauna
(Hessler and Sanders, 1967) and the systematics and
phylogeny of major invertebrate groups (Wilson, 1987).
Also, such samples taken repeatedly from the same area
have provided information on temporal phenomena,
in particular reproductive periodicity in the deep sea
(Rokop, 1974; Tyler et al., 1982).
Corers
Corers are used to sample macrofauna, meiofauna, and
microbiota. Two types are presently in common use.
Box corers, in particular the USNEL-Sandia 0.25-m
2
box corer (Hessler and Jumars, 1974; Fig. 2.11), are
Fig. 2.11. An advanced version (Hessler–Sandia) of the USNEL
box corer (shown in the closed position), a device for collecting
quantitative samples of deep-sea macrofauna. The width of the
sample box is 0.5 m. A, The detachable spade; B, vent flaps in the
open position for descent; C, vent flaps in the closed position for
ascent; D, cable to the ship. Some details omitted. Modified from
Fleeger et al. (1988).
lowered on a ship’s trawl wire. About 100 m above
bottom, the rate of descent is slowed to 15 m min
−1
until the corer penetrates the bottom. This relatively
high entry speed is necessary to minimize multiple
touches and pretripping. As the corer is pulled out
of the seabed, the top and bottom of the sample box
are closed. The advantages of a box corer are that it
takes a sample of known area to a depth (>20 cm) that
encompasses the bulk of the vertical distribution of
deep-sea organisms.
Box corers are not strictly quantitative. They occasionally collect megafaunal individuals, but megafauna
are too rare to be effectively sampled. Further, the
13
which moves into the collecting bag. Sleds collect
macrofauna in large numbers, supplying specimens for
research in which properties of each individual must
be determined – for example, studies of reproductive
biology, biomass distribution, and taxonomy. Sleds do
not collect every individual in their path in the layer
to be sampled because the mouth of the bag clogs
with sediment as the sled moves along the seabed
(Gage, 1975), so sleds are inappropriate for quantitative
studies. They can also damage delicate specimens (e.g.,
the legs of isopods tend to be broken off) and cannot
sample macrofauna living at greater depths than 1–
2 cm.
The deep-sea-floor ecosystem extends into the nearbottom water because some animals living in or on
the seabed make excursions into the near-bottom water,
and some animals living in the water just above the
seabed interact with the seafloor. Hyperbenthic sledges
(see also Rice et al., 1982) have been developed to
sample the near-bottom water. Such sledges consist
of runners and a frame supporting a vertical array of
opening–closing nets (Dauvin et al., 1995; Fig. 2.10).
A
B
C
D
E
F
Fig. 2.10. The hyperbenthic sled, a device for collecting deep-sea
animals in the waters just above the seabed. The device is 1.51 m
tall. A, Attachment point for the cable to the ship; B, frame; C, mouth
of a sampler; D, net; E, sample container; F, runner. Modified from
Dauvin et al. (1995). Copyright: Elsevier Science.
The usual limitations of plankton nets apply to these
samplers (e.g., bias in collections owing to differences
in avoidance behavior among species, variable filtering
efficiency resulting from net clogging). In addition, the
frame may put animals from the seabed into suspension
and thus cause them to be caught, particularly in the
lowest net. Despite their limitations, these samplers
provide access to an understudied component of the
deep-sea fauna (see also Wishner, 1980).
Despite their limitations, most of the taxonomic,
systematic, and biogeographic research on the deepsea fauna has been based on the large collections
that trawls, sledges, and sleds provide (Hessler, 1970).
This research has resulted in discoveries regarding, for
example, the high diversity of the deep-sea-floor fauna
(Hessler and Sanders, 1967) and the systematics and
phylogeny of major invertebrate groups (Wilson, 1987).
Also, such samples taken repeatedly from the same area
have provided information on temporal phenomena,
in particular reproductive periodicity in the deep sea
(Rokop, 1974; Tyler et al., 1982).
Corers
Corers are used to sample macrofauna, meiofauna, and
microbiota. Two types are presently in common use.
Box corers, in particular the USNEL-Sandia 0.25-m
2
box corer (Hessler and Jumars, 1974; Fig. 2.11), are
Fig. 2.11. An advanced version (Hessler–Sandia) of the USNEL
box corer (shown in the closed position), a device for collecting
quantitative samples of deep-sea macrofauna. The width of the
sample box is 0.5 m. A, The detachable spade; B, vent flaps in the
open position for descent; C, vent flaps in the closed position for
ascent; D, cable to the ship. Some details omitted. Modified from
Fleeger et al. (1988).
lowered on a ship’s trawl wire. About 100 m above
bottom, the rate of descent is slowed to 15 m min
−1
until the corer penetrates the bottom. This relatively
high entry speed is necessary to minimize multiple
touches and pretripping. As the corer is pulled out
of the seabed, the top and bottom of the sample box
are closed. The advantages of a box corer are that it
takes a sample of known area to a depth (>20 cm) that
encompasses the bulk of the vertical distribution of
deep-sea organisms.
Box corers are not strictly quantitative. They occasionally collect megafaunal individuals, but megafauna
are too rare to be effectively sampled. Further, the