Relationships between meiofaunal population densities and physico-chemical properties of unpolluted sandy beaches.

Water and sediment samples from ten unpolluted sandy beaches have been analysed for various chemical parameters and meiofauna. The results have indicated that, within the range of grain sizes found, (196-337 μm), short term fluctuations in the natural levels of the various chemical constituents do not significantly influence the densities of meiofauna populations. These are, however, governed largely by the median grain size of the sediments. The relationships between median grain size and the population densities of nematodes and harpacticoid copepods have been established. The optimum grain size for the populations studied was 284 μm, and as the sediment size deviated from this, the population density decreased. Thus knowledge of the median grain size of sediments should indicate the approximate meiofaunal density which can be expected in the absence of any other external influence. Deviations from this can then be attributed to perturbation.