The same applies to our knowledge of the role meiofauna play in organic production within different areas of the sea. It is also important to increase our knowledge of the trophic relationships and position of meiofauna in food chains. One such area could be the use of meiofauna species as test organisms for studying the biological effect of water pollution components.
Based on their own experiences, the authors of this manual have recommended certain methods for the study of meiofauna. There is therefore still much to be done in the field of both the systematics and the ecology of the meiofauna in the rest of the world. We are indebted to many individuals and organizations for the success of the conference.
Funding for the conference was made possible by the Office of International Activity of the Smithsonian Institution, Washington, D.C. The management of the Hilton Hotel, Tunis, assisted in many aspects of the local arrangements.
General Description of Habitat
In both the littoral and the sublittoral, attention must be paid to the characteristics of the water column. Samples should also be taken from the adjacent seawater (at low tide) or the overlying seawater (at high tide). Intermediate values measure the water saturation of the pores proportionally in percent, and measurements to the nearest 2 percent saturation can be obtained.
A simple and rapid measurement of the hydrogen sulphide content of a sediment can be made using a Hach H2S test (see appendix, section 10.1.10). Initially, the sediment sample should be wet sieved through a 62/* sieve, using only water of the same salinity as the sample area. The asymmetry or skewness of the grain size distribution pattern can be measured by the inclusive graphical skewness, SKX (Folk, 1968).
Placement of the samples can be done according to a stratified or random procedure, depending on the study. However, core and sample sizes should be related to the size and relative abundance of the animals to be studied. The sand is then dug away to the level of the bottom of the auger and the auger is removed.
The replicas can be divided horizontally to provide information on the vertical distribution of the fauna.
General Extraction Techniques
A suitable qualitative sampler should collect only the top few centimeters of the precipitate over a fairly extensive area and should not be subject to winnowing. Suitable devices of this type have not yet been designed for deep-sea meiofauna work, but some of the meiofauna samplers currently in use can be suitably modified, such as the epibenthic sledge designed at the Woods Hole Oceanographic Institute (Hessler and Sanders, 1967). The meiofauna is finally washed into the cone of the net and the inverted net is washed in a container.
At the end of the process, decant the liquid and replace it with fresh 4 percent formalin or 70 percent alcohol. The process is repeated three to seven times, after which the fauna is rinsed into the mesh cone (8), which is then inverted and the collection is washed into a container (9) and stored (10). Death is almost certain as a result of heatstroke, which accompanies the transition of fauna from deep cold to warmer surface conditions.
Animals may still be alive when they surface due to the insulating effect of the large volume of sediment, and if suitable cooling facilities are available it may be possible to keep them alive at least long enough to applied anesthetics before conservation. If extensive manipulation of the live sample is required, it is best to bring large refrigerated samples ashore for processing, and this may be practical when a laboratory is close to deep-sea areas, such as in Bermuda. The technique has also been used successfully with 40°C water instead of ice, and this may be preferable in tropical regions.
The melting time of the ice is, of course, shorter, but he found that this does not cause problems in the extraction. The pressure is adjusted in such a way that a balance is achieved between vigorous mixing of the sand and only a small amount of sediment is transferred to pipe C and sieve (D). Further, while it may be used as above for living fauna, several groups (Tardigrada, some Nematodes) are difficult to separate from grains of sand, and others, such as Turbellaria, quickly recover from the anesthetic and attach themselves firmly to the walls of the tubes.
The main components of the Lasserre modification are a 5 liter glass flask with two stirring systems. A glass column contains a large mesh net that retains most very coarse particles and fragments of seagrass and algae. For preserved material a similar technique can be used, but the sample is first stained with Rose Bengal (0.1 g/.
SILICONE COATED LARGE PIPETTE
The usual procedure for live meiobenthos is to divide the sample into two fractions, using a fine sieve (30 to 60 /i). The fine fraction, which contains the silt and clay, is stirred to a uniform suspension and the liquid is subsampled. The precipitate in the subsamples is allowed to settle in a thin layer on a Petri dish, and the animals can be seen and counted by their movements.
I50J) OR LESS
PLEXIGLASS NYLON SIEVE
PETRI DISH
Culture and Experimental Techniques
- Experimental Techniques
In productivity studies, there is a great need for more information on community metabolism, including a preferred method to measure laboratory studies of the major pathways of the energy flow. An adequate culture of organisms presupposes a good knowledge of the species and of the environmental conditions in the normal habitat. Animals can be seen through the beads, and the chemical nature of the beads is infinitely easier to control than the natural substrata.
In this way, the attraction of sorted sand (Boaden, 1962) or migration due to tidal movements of the interstitial water (Renaud-Debyser) has been studied. For comparison with other studies, the results should be expressed as LD-50 values (lethal) dose 50), meaning the time or dose at which 50 percent of the test population died. Careful observation of the organisms during the experiment, noting whether they are sluggish, comatose, etc., will provide information for further studies and give the data greater biological significance.
It is better to observe the degree of recovery of the test population after transfer to optimal conditions than to simply note LD-50 values. The deviation from the theoretical random distribution is taken as a measure of the intensity of the preference. In alternative experiments, the animals are offered two or more alternative properties of the investigated parameter, e.g. feed types, sand qualities, salinities (Gray, 1966a,b, in press.fe; Jansson.
In gradient experiments, the organisms are transferred to a gradient of the factor being studied, eg temperature (Gray, 1965; Jansson, 1966). Physiological techniques.—Where the ecologist ends his task, the physiologist can sometimes carry it further to explain the metabolic processes that determine the reactions of the animals. When purely ecological techniques fail to explain the distribution of the organisms, physiological evidence can be shown.
Oxygen consumption has often been taken as a measure of the organism's metabolic activity. Studies of the oxygen consumption in water with different salinity and ionic composition (corresponding to Lasserre in press) provide valuable information for the ecologist when explaining field distributions. Little is known about the function and even the morphology of the different types of sensory organs in the meiofauna.
Biotopes other than Sediment
