Islands of Mytilus as a habitat for small intertidal animals: effect of island size on community structure

Abstract

Patches of Mytilus edulis 1. composed of similar sized mussels were surveyed in order to investigate the effect of patch size on community structure of associated animals. Each patch included common components such as byssus, shell fragments, sediments. algae and associated animals. Volume of each component increased with patch size. With increasing patch size. species richness and number of individuals of associated animals increased, but decreased per unit patch size. Patch area affected population density more than patch volume. Volume of associated animals per unit patch area was relatively constant, but volume per unit patch volume decreased with increasing patch size. Mean body width of the polychaete Typosyllis adamanteus Jrun'lensis Chlebovitsh increased with patch size, Large individuals of the winkle Littorina brevicula Philippi were not found in smaller patches. At high tides, large numbers of the amphipod Hyale grandicomis Kroyer, which live among algae attached to the patches, were seen on rock surfaces covered by the barnacle Chthamalus challengeri Hoek around the patches. These results can be mainly explained in relation to accumulation of sediments and shell fragments of M, edulis in the patches, and the community structure of the Mytilus island is discussed with reference to species-area relations.