Spatial niches and long-term performance in meiobenthic Plathelminthes of an intertidal lugworm flat

Abstract

A spatio-temporal study over 7 yr and 26 microsites revealed a significant correlation between interannual variability and the location, size and shape of spatial niches for 56 plathelminth (turbellarian) populations in a sandy, marine sediment. Each June, microsites of the surface layer, of the sulfide layer, of vertical shafts, and of coarse sand at feeding pockets of lugworm burrows were investigated on a sand flat in the lower tidal zone near the island of Sylt (North Sea). Microsite prefergnces were consistent over time. Populations distributed over a wide range of microsites tended to persist longer than populations confined to narrow spatial niches. The latter fluctuated more in population density than those scattered over several sites. Surface-dwekng species were more variable over time than species characteristic of the sulfide layer. Two species deviated from this pattern. They were restricted to pocket sand and yet their population size remained almost constant over the years. They may b e microsite specialists. Apparently, meiobenthic plathelminths perceive the sediment a s a dinstinctly structured habitat, and species of the sediment surface differ in their adaptive traits from species living in the sulfide layer