238
N. A. HOLME
When hand-sorting the meiobenthos it may be advantageous to
us0 a dye to distinguish the living organisms. McIntyre (1961) has
used tho stain rose bengal for this purpose and an account of the
methods used is given in his paper.
XI. SEDIMENT ANALYSIS
A sample of sediment for reference purposes, or for mechanical or
chemical analysis is usually required. I n dredge samples this may be
taken from the middle of the contents of the bag (Smith, 1932), to
minimize tshe effects of washing out. Except in extreme cases where
the jaws have been held open by a stone, fairly representative samples
may be taken from a grab (Davis, 1925). I n the majority of instances
the original stratification will have h e n lost or distorted, and if
greater precision is required a separate sample with a corer may be
taken. However, in benthos studies we are concerned with the properties of the sediment as they affect the fauna, and it is therefore best
if both are sampled a t the same time. This point was made by Davis
(1925) who used sediment samples taken from the grab rather than
take additional samples with a conical dredge, the latter instrument
being considered to take a more satisfactory sample for grade analysis.
Certain techniques developed for agricultural soils have been used
for chemical analyses of sediments, but these should be employed
with caution. For example, Southward (1952) has pointed out that the
presence of coal in deposits will vitiate certain methods for analysis
of organic carbon. (Methods of analysis subject, however, to this
source of error are given by Morgans (1956), Slinn (in Jones, 1956),
and el Wakeel and Riley, 1057.) Much remains to be done on the
methods to be employed for measuring other properties of the substrate, always bearing in mind that one is attempting to measure
conditions as they are in situ at the bottom of the sea.
Qrade Analysis. Mechanical analysis of particle size is often necessary as it is difficult to classify sediments merely by inspection. A
sample of 400-500 ml may be taken in a screw-top jar, no prcscrvative
being added (cp. Morgans, 1956, p. 379). Any large animal would
naturally he removed, but normally such samples store wdl. Borley
(1923) records instances of animals found alive in samples examined
up to 17 months after capture.
Various methods of mechanical analysis have been described ;
most have been developed either for agricultural soils or for sedimentary petrology, and require some modification :
(a) Solution of carbonates before analysis as used for agricultural
soils (e.g. Piper, 1942) and advocated by Barnes (1959s) for
N. A. HOLME
When hand-sorting the meiobenthos it may be advantageous to
us0 a dye to distinguish the living organisms. McIntyre (1961) has
used tho stain rose bengal for this purpose and an account of the
methods used is given in his paper.
XI. SEDIMENT ANALYSIS
A sample of sediment for reference purposes, or for mechanical or
chemical analysis is usually required. I n dredge samples this may be
taken from the middle of the contents of the bag (Smith, 1932), to
minimize tshe effects of washing out. Except in extreme cases where
the jaws have been held open by a stone, fairly representative samples
may be taken from a grab (Davis, 1925). I n the majority of instances
the original stratification will have h e n lost or distorted, and if
greater precision is required a separate sample with a corer may be
taken. However, in benthos studies we are concerned with the properties of the sediment as they affect the fauna, and it is therefore best
if both are sampled a t the same time. This point was made by Davis
(1925) who used sediment samples taken from the grab rather than
take additional samples with a conical dredge, the latter instrument
being considered to take a more satisfactory sample for grade analysis.
Certain techniques developed for agricultural soils have been used
for chemical analyses of sediments, but these should be employed
with caution. For example, Southward (1952) has pointed out that the
presence of coal in deposits will vitiate certain methods for analysis
of organic carbon. (Methods of analysis subject, however, to this
source of error are given by Morgans (1956), Slinn (in Jones, 1956),
and el Wakeel and Riley, 1057.) Much remains to be done on the
methods to be employed for measuring other properties of the substrate, always bearing in mind that one is attempting to measure
conditions as they are in situ at the bottom of the sea.
Qrade Analysis. Mechanical analysis of particle size is often necessary as it is difficult to classify sediments merely by inspection. A
sample of 400-500 ml may be taken in a screw-top jar, no prcscrvative
being added (cp. Morgans, 1956, p. 379). Any large animal would
naturally he removed, but normally such samples store wdl. Borley
(1923) records instances of animals found alive in samples examined
up to 17 months after capture.
Various methods of mechanical analysis have been described ;
most have been developed either for agricultural soils or for sedimentary petrology, and require some modification :
(a) Solution of carbonates before analysis as used for agricultural
soils (e.g. Piper, 1942) and advocated by Barnes (1959s) for