Macrobenthic migration and its influence on the intertidal diversity dynamics of a meso-tidal system

The link between movement and migration of organisms to patterns of biodiversity may be an important mechanism of biodiversity maintenance at local scales. but is regularly underestimated in marine studies. Patterns of diversity, density and distribution of all mobile macrofaunal components of an intertidal assemblage were quantitatively investigated throughout diurnal and tidal cycles In a meso-tidal system southwest Ireland. A significant trend of decreasing diversity with shore height was observed during periods of emersion at both day and night, but not during immersion. While certain taxa (e.g. the isopod Ligia oceanica and the sea mite Erythraeus sp.) exhibited obvious patterns of activity and migration with tide and time, the majority of species were observed to be sedentary or showed no obvious pattern of migration. The influence of rare, transient species on biodiversity measurement and community structure was significant, particularly during periods of immersion. In order to produce meaningful descriptions of intertidal biodiversity, it is therefore crucial that future studies be conducted during periods of immersion and emersion, and that they should consider the influence of migrating species.