Publication Abstract

Spatial variability of infaunal nematode and polychaete assemblages in two muddy subtidal habitats

M. Schratzberger, T.A.D. Maxwell, K. Warr, J.R. Ellis and S.I. Rogers

Spatial variation of populations and their assemblages is an important component of many aspects of ecology, including the maintenance of species diversity. In nature, organisms are generally aggregated in patches or form gradients or other spatially-related patterns. This investigation quantified the degree of spatial structure in benthic invertebrate assemblages. It examined the distribution of infaunal assemblages of different size, mobility and contrasting life-history strategies (i.e. meiofaunal nematodes and macrofaunal polychaetes) in two offshore muddy habitats in the Celtic Deep and the NW Irish Sea off the west coast of the United Kingdom. The influence of environmental variables and densities of common epibenthic bioturbators on spatial patterns was also examined. In both habitats, the environmental conditions became increasingly dissimilar with separation. In contrast to the comparatively heterogeneous environment in the NW Irish Sea, the more homogeneous conditions in the Celtic Deep changed along predictable gradients. Results from correlation analyses revealed statistically robust relationships of community similarity and sample distance. Infaunal populations were clearly distributed along gradients that reflected the scales of influence of a suite of environmental factors. Given their small size and low mobility, nematodes were more susceptible to within-habitat physical variability than larger-sized, more mobile polychaetes. This resulted in a significant decrease in community similarity with distance at the spatial scales sampled (4 - 23 km). Polychaete species responded to fewer environmental factors and thus their populations were relatively unaffected by sample distance. The potential mechanisms causing the observed variation are discussed.

Reference

M. Schratzberger, T.A.D. Maxwell, K. Warr, J.R. Ellis and S.I. Rogers (2008) Spatial variability of infaunal nematode and polychaete assemblages in two muddy subtidal habitat. Marine Biology 153: 621-624