METHODS OF SAMPLING THE BENTHOS
209
D. Underwater photography and television,
I n recent years both underwater photography (e.g. Ewing et al.,
1946; Vevers, 1951, 1952 ; Hartman, 1955 ; McIntyre, 1956 ; Barnard
et al., 1959 ; Hurley, 1959 ; Edgerton and Raymond, 1962 ; Craig and
Priestley, 1963; Edgerton, 1963) and to a lesser extent television
(summarized in Barnes, 1963) have been widely used a t sea and have
contributed considerably to certain aspects of our knowledge of the
benthos. This is not the place to discuss the use of such instruments
in studying the behaviour of bottom-living animals, and remarks will
be confined to their possible uses in exploring the nature of the bottom
and the occurrence of benthic species.
The equipment is basically quite simple, consisting of a camera in
a watertight case having a glass front. The camera is supported to
point either vertically or obliquely down at the sea bed. The subject
is illuminated by floodlights (or electronic flash) and in the photographic cameras a rigid foot or hanging counterweight operates the
camera when it has been lowered to the required distaiice above the
sea bed. In shallow water an electric cable from the ship may be used
to provide power for the floodlights, but in deeper water photographs
may be taken by self-contained flash equipment. In either case it is
possible to take a series of picturcs a t one lowering. Considerable
advances have recently been made in the optical, electronic and
mechanical equipment used for such work, details of which may be
found in the literature cited above.
It is a t oncc clear that both photography and television may be
used in surveying larger members of the epifauna, but that information
on the infauna will be cqnfined to observation of burrows or other
features visible on the surface. It must be frustrating to be able to
see but not collect an unknown animal, and studies are probably most
useful where the fauna is well known and animals can be identified
in the pictures. The area which can be scanned is larger than can be
covered by the grab, but the opacity of the water and need for fine
detail may restrict the area seen a t any one time to not much more
than a, square metre (Fig. 24). The surveys by Vevers (1961, 1952) of
beds of brittle-stars in the English Channel illustrate the use of the
camera where it is most helpful. Other uses are in investigating details
of the deposit. the presence of ripple-marks, and other features
(Laughton, 1063). McIntyre (1956) has made a useful comparison of
the efficiency of trawl, grab and camera in surveying the benthos
(see p. 2151, and with television it is also possible to watch the operation
of collecting gear on the sea floor, although this may often be better
done in shallow water by free-divers, perhaps equipped with cameras.
209
D. Underwater photography and television,
I n recent years both underwater photography (e.g. Ewing et al.,
1946; Vevers, 1951, 1952 ; Hartman, 1955 ; McIntyre, 1956 ; Barnard
et al., 1959 ; Hurley, 1959 ; Edgerton and Raymond, 1962 ; Craig and
Priestley, 1963; Edgerton, 1963) and to a lesser extent television
(summarized in Barnes, 1963) have been widely used a t sea and have
contributed considerably to certain aspects of our knowledge of the
benthos. This is not the place to discuss the use of such instruments
in studying the behaviour of bottom-living animals, and remarks will
be confined to their possible uses in exploring the nature of the bottom
and the occurrence of benthic species.
The equipment is basically quite simple, consisting of a camera in
a watertight case having a glass front. The camera is supported to
point either vertically or obliquely down at the sea bed. The subject
is illuminated by floodlights (or electronic flash) and in the photographic cameras a rigid foot or hanging counterweight operates the
camera when it has been lowered to the required distaiice above the
sea bed. In shallow water an electric cable from the ship may be used
to provide power for the floodlights, but in deeper water photographs
may be taken by self-contained flash equipment. In either case it is
possible to take a series of picturcs a t one lowering. Considerable
advances have recently been made in the optical, electronic and
mechanical equipment used for such work, details of which may be
found in the literature cited above.
It is a t oncc clear that both photography and television may be
used in surveying larger members of the epifauna, but that information
on the infauna will be cqnfined to observation of burrows or other
features visible on the surface. It must be frustrating to be able to
see but not collect an unknown animal, and studies are probably most
useful where the fauna is well known and animals can be identified
in the pictures. The area which can be scanned is larger than can be
covered by the grab, but the opacity of the water and need for fine
detail may restrict the area seen a t any one time to not much more
than a, square metre (Fig. 24). The surveys by Vevers (1961, 1952) of
beds of brittle-stars in the English Channel illustrate the use of the
camera where it is most helpful. Other uses are in investigating details
of the deposit. the presence of ripple-marks, and other features
(Laughton, 1063). McIntyre (1956) has made a useful comparison of
the efficiency of trawl, grab and camera in surveying the benthos
(see p. 2151, and with television it is also possible to watch the operation
of collecting gear on the sea floor, although this may often be better
done in shallow water by free-divers, perhaps equipped with cameras.