172
N. A. HOLME
trace the history of benthos investigations and then consider how far
the instruments now available provide 11s with the quantitative samples
we require. It will thcn bc stiowii how advances in other fields such
as radio-position finding, sonar and electronic equipment have increased
the precision of our sampling nicthods. Sorting and sieving on board
ship will be considered and brief mention made of methods of soil
analysis and biomass determination. Considerable advances have been
made in recent years in statistical studies of plant and animal populations, and the application of these methods to benthos sampling will
finally be considered.
11. BOTTOM DEPOSITS AND THEIR FAUNA
Large areas of the sea floor are covercd by uncompacted deposits
of mud, sand or gravel, the proportion occupied by rocky outcrops
being relatively small and confined to limited areas in the vicinity of
the coasts, parts of the continental slope, submarine ridges, canyons,
and so on. These areas are either stcep-sloping or exposed to turbulent
conditions so that deposits are unable to accumulate. The exploration
of such rocky areas is a specialized field, in which the development of
free-diving in shallow water, and underwater photography, television
and the bathyscaphe in deeper water, have enabled considerable
advances in our knowledge to take place during the last few years.
This review is concerned with the problems of sampling the sediments and their contained fauna 011 the level sea bottom, with particular refercnce to work in open sea conditions on the continental
shelf. It is not proposcd to describe in detail methods of sampling the
microfauna, and in gcneral the techniques described arc applicable
to collecting members of the macrofauna of such a size that they can
be readily separated by sieving.
Nearly every type of marine deposit, except for a few exposed to
excessive disturbance by waves or currents, is inhabited by an assemblage of animals, some of which live on the surface (the so-called
" epifauna "), while others (the " infauna ") burrow or lie buried
beneath the surface, usually maintaining connection with the overlying
wster by a tube or by siphons. The depth to which such animals
may burrow is discussed on p. 212, but in general it may be said that
the vast majority occur within 30 cm of the surface. On most gronnds
the infauna is of considerably more importance than the epifauna,
both in terms of numbers and of total weight. Members of the epifauna
tend to be active predators, they themselves being protected from
attack either by their powers of rapid movement, possession of
mechanical means of protection, or by being inedible to fish. Members
N. A. HOLME
trace the history of benthos investigations and then consider how far
the instruments now available provide 11s with the quantitative samples
we require. It will thcn bc stiowii how advances in other fields such
as radio-position finding, sonar and electronic equipment have increased
the precision of our sampling nicthods. Sorting and sieving on board
ship will be considered and brief mention made of methods of soil
analysis and biomass determination. Considerable advances have been
made in recent years in statistical studies of plant and animal populations, and the application of these methods to benthos sampling will
finally be considered.
11. BOTTOM DEPOSITS AND THEIR FAUNA
Large areas of the sea floor are covercd by uncompacted deposits
of mud, sand or gravel, the proportion occupied by rocky outcrops
being relatively small and confined to limited areas in the vicinity of
the coasts, parts of the continental slope, submarine ridges, canyons,
and so on. These areas are either stcep-sloping or exposed to turbulent
conditions so that deposits are unable to accumulate. The exploration
of such rocky areas is a specialized field, in which the development of
free-diving in shallow water, and underwater photography, television
and the bathyscaphe in deeper water, have enabled considerable
advances in our knowledge to take place during the last few years.
This review is concerned with the problems of sampling the sediments and their contained fauna 011 the level sea bottom, with particular refercnce to work in open sea conditions on the continental
shelf. It is not proposcd to describe in detail methods of sampling the
microfauna, and in gcneral the techniques described arc applicable
to collecting members of the macrofauna of such a size that they can
be readily separated by sieving.
Nearly every type of marine deposit, except for a few exposed to
excessive disturbance by waves or currents, is inhabited by an assemblage of animals, some of which live on the surface (the so-called
" epifauna "), while others (the " infauna ") burrow or lie buried
beneath the surface, usually maintaining connection with the overlying
wster by a tube or by siphons. The depth to which such animals
may burrow is discussed on p. 212, but in general it may be said that
the vast majority occur within 30 cm of the surface. On most gronnds
the infauna is of considerably more importance than the epifauna,
both in terms of numbers and of total weight. Members of the epifauna
tend to be active predators, they themselves being protected from
attack either by their powers of rapid movement, possession of
mechanical means of protection, or by being inedible to fish. Members