Benthos - Meiofauna
Source: University of Crete
Equipment required
| Corers | Cylindrical, transparent, plastic tubes (proposed inner diameter 4.4 cm) with smooth internal surface and beveled lower end to facilitate sediment penetration and core removal. The length should be at least 15 cm (Fig. 1a) |
| Rubber stoppers | Appropriate diameter for tight-fitting to the coring tubes (Fig. 1) |
| Core plunger | Same diameter with the corers for extruding the sediment core (Fig. 1b) |
| Corers basket | Will ensure the upright position of the core samples |
| Sample containers | ~ 500 ml volume |
| Sample labels | Indicate area, station, replicate and date |
| Syringe |
~ 20 ml volume |
| 7% MgCl2 |
7.5 g MgCl2 6H2O dissolved in 100 ml distilled water. Used as a narcotic agent |
|
10% buffered formalin (4% formaldehyde) |
Filtered seawater (through a 45 um sieve) should be used as dilutant to prevent contamination with planktonic species. The formalin should be buffered with 200 g Borax per liter |
| Washbottles | Used for distilled/filtered water, MgCl2 |
| Sample labels | Helpful for slicing the cores |
| Rubber mallet | |
Sampling
In sediments, coring is the best quantitative sampling technique for meiobenthos, because when corers are used with care they collect a known area or volume of sediment with all depths equally represented and all animals present before sampling are captured.
Figure 1 a) Corers, rubber stoppers and b) core plunger for sampling meiobenthos.
If possible, subtidal samples should be taken by SCUBA divers (Fleeger et al. 1988). Divers usually obtain superior samples because they are able to position the samplers with care and insert the corer slowly (McIntyre 1971). In addition, the presence of the investigator will often yield important insights about the ecology of the site or practical aspects of the sampling (Fleeger et al. 1988). However, if diving is not possible, a Craib type corer (Fig. 2a) may be used instead. Subsampling from a sample collected with a multiple SMBA type corer, grab or box corer is also an alternative (Fig 2b,c). In the above case, caution should be taken to avoid pseudoreplication by taking each subsample from different deployments.
Figure 2. Different samplers used on research vessels for meiobenthic studies. a) Craib corer, b) box corer, c) multiple corer.
Processing cores It is easiest to process the cores by working with another person. The bottom stopper is removed and replaced by the core plunger, to avoid loss of the sample. Following this, the upper stopper is removed and the overlying water is transferred, with a syringe, to a sample jar (because meiofauna may have swum out of the sediments to the water). Next, the sediment is pushed out of the corer and the top 10cm are transferred to the sample jar. A 7% MgCl2 solution is added to the jar until the sample is fully covered. Stir gently and allow 10 minutes to react. Next, the sample is fixed by adding buffered formalin to achieve a final concentration of 10% (take into consideration the volume of sediment, water and MgCl2). Invert the jar several times to mix the fixative and sediment and store at room temperature until the samples may be processed further. References Elmgren R (1973) Methods of sampling sublittoral soft bottom meiofauna. Oikos Supplement 15: 112-120 Fleeger JW, Thistle D, Thiel H (1988) Sampling equipment. In: Higgins RP, Thiel H (eds) Introduction to the study of meiofauna. Smithsonian Institution Press, Washington DC, London, p 115-125 Pfannkuche O, Thiel H (1988) Sample processing. In: Higgins RP, Thiel H (eds) Introduction to the study of meiofauna. Smithsonian Institution Press, Washington DC, London, p 134-145 Giere O (1993) Meiobenthology. The microscopic fauna in aquatic sediments. Springer-Verlag, Berlin McIntyre AD (1971) Deficiency of gravity corers for sampling meiobenthos and sediments. Nature 231:260
