220
N. A. HOLME
6 cm in diameter and some 30 cm long for studies on the microfauna.
I n soft deposits such a core may be obtained by a variety of instruments, such as the Moore and Neil1 (1930) corer (Fig. 27), and the
Enequist sampler. The latter covers an area of 100 om*, the bottom
of the tube being closed by two flaps at ita lower end (Fig. 13). It
“ will sink deeply into all muddy and mixed bottoms but not into hard
sand and gravel bottoms ” (Thorson, 1967a ; Enequist, 1941).
On hard, sandy grounds it is very difficult to get a satisfactory
core. The Knudsen sampler, where available, might be used, but it
takes rather too large a sample. The majority of small corers are useless
on such grounds, and a heavy instrument such aa the free-fall corer
(Hvorslev and Stetson, 1946) might have to be used. Alternatively
it might be necessary to take the sample with a grab in which stratification is, however, partially lost. The “ vacuum ’’ grab is a useful
instrument for taking a small sample not subject to washing out.
Any stratification is completely lost, however. Dr. P. R. 0. Barnett
haa used the improved model (Holme, 1965) for obtaining microfauna,
samples from all parts of the English Channel during my own survey
of the macrofauna.
2. Samplers for snzall boat%
The only instrument which can be used from a small launch not
fitted with a power hoist is a small dredge. Where it is desired to bring
up a sample of the sediment a launch with power hoist is usually
necessary, and for working a grab a small boom or other device for
swinging the gear outboard will be required. By this means some of
the lighter quantitative gem can be umd, although it will be appreciated that the weight of the sediment itself when the sampler is hauled
clear of the water will often be the limiting factor.
The following instruments might be used from a small launch:
(a) Qualitative earnplet-8
Dredges, including the conical dredge
Small beam or Agaasiz trawl
Robertson bucket dredge (semi-quantitative)
(b) Quantitative samplers
Forster’s anchor-dredge
0.1 ma Petereen grab
0.1 ma van Veen grab
0-1 mt Aberdeen grab
N. A. HOLME
6 cm in diameter and some 30 cm long for studies on the microfauna.
I n soft deposits such a core may be obtained by a variety of instruments, such as the Moore and Neil1 (1930) corer (Fig. 27), and the
Enequist sampler. The latter covers an area of 100 om*, the bottom
of the tube being closed by two flaps at ita lower end (Fig. 13). It
“ will sink deeply into all muddy and mixed bottoms but not into hard
sand and gravel bottoms ” (Thorson, 1967a ; Enequist, 1941).
On hard, sandy grounds it is very difficult to get a satisfactory
core. The Knudsen sampler, where available, might be used, but it
takes rather too large a sample. The majority of small corers are useless
on such grounds, and a heavy instrument such aa the free-fall corer
(Hvorslev and Stetson, 1946) might have to be used. Alternatively
it might be necessary to take the sample with a grab in which stratification is, however, partially lost. The “ vacuum ’’ grab is a useful
instrument for taking a small sample not subject to washing out.
Any stratification is completely lost, however. Dr. P. R. 0. Barnett
haa used the improved model (Holme, 1965) for obtaining microfauna,
samples from all parts of the English Channel during my own survey
of the macrofauna.
2. Samplers for snzall boat%
The only instrument which can be used from a small launch not
fitted with a power hoist is a small dredge. Where it is desired to bring
up a sample of the sediment a launch with power hoist is usually
necessary, and for working a grab a small boom or other device for
swinging the gear outboard will be required. By this means some of
the lighter quantitative gem can be umd, although it will be appreciated that the weight of the sediment itself when the sampler is hauled
clear of the water will often be the limiting factor.
The following instruments might be used from a small launch:
(a) Qualitative earnplet-8
Dredges, including the conical dredge
Small beam or Agaasiz trawl
Robertson bucket dredge (semi-quantitative)
(b) Quantitative samplers
Forster’s anchor-dredge
0.1 ma Petereen grab
0.1 ma van Veen grab
0-1 mt Aberdeen grab