Phytal marine nematode assemblages on Sargassum confus~m Agardh, with reference to the structure and seasonal fluctuations

Free-living nematodes are the major members of marine meiobenthic animals which play important roles in the secondary production and food webs (e.g. McIn-tyre, 1969; Gerlach, 1971, 1978), therefore a number of ecological studies on the nematode assemblages have been carried out in various marine habitats (see Nicholas, 1975). However, our quantitative knowledge concerning the seasonal variability in population density and species composition is poor, and most of it is given in sediment habitats (e.g. Tietjen, 1969; Warwick and Buchanan, 1970, 1971; Lorenzen, 1974; Juario, 1975). Although phytal marine nematode assemblages have been investigated mainly on the relation between their faunal characteristics and the morphology of seaweeds (Wieser, 1951, 1952, 1959a, b; Ott, 1967; Moore, 1971; Warwick, 1977), there were only a few data on seasonal change in populatio