The study of meiobenthos size structure with the sieving method (Case study of the Arctic Basin free-living nematodes)

Body lengths and widths were measured and body volumes were calculated for 1556 Arctic nematodes sampled from depths of 800-3000 m. The samples were f iltered through standard sieves with mesh sizes of 500, 250, 125, 63, and 3 2 pm. Due to the random orientation of the animal bodies with respect to th e sieve plane and the presence of detrital and sediment particles, one can only assess the probabilities of the animal retention over the sieves. The distributions of the logarithms of the body volume and length values of nem atodes were close to the normal distribution on the three finer sieves. A s imple mathematical filtration model describing size distribution of nematod es on the sieves is proposed. A relation between the mean logl(mean) value on the sieve and the logarithm of its mesh size logm was obtained: logl(mea n),an = a + k logm; the k values ranged from 0.5 to 1.0 linearly depending on the dispersion of the original size spectra. The limitations for the app lication of this relation are discussed.