Benthic fauna in tropical tidal flats - A comparative perspective

Tidal flats extend seaward from mangrove forests along many tropical coastlines. This contribution compiles the current knowledge on tropical tidal flats with regard to species richness, abundance, spatial distribution patterns and ecological roles taken by major organisms. Tidal flats encompass a variety of soft-sediment habitats which are inhabited by a species-rich fauna. Species numbers are generally higher than in temperate tidal flats, but vary widely between tropical sites where they have not yet been fully assessed due to lack of research and taxonomic problems. The assessment of biodiversity is further complicated by a low species frequency, the small size of macroinfaunal organisms and variations in the occurrence of species between sites. Mean abundance ranges from 1000-2000 individuals m ^-2 , although figures ten times higher have been recorded in a mudflat in Costa Rica, and there are great variations in general. Individual densities of small-sized macrofauna are about ten times higher than for larger macrobenthos. A generalized zonation scheme for intertidal distribution patterns of tropical tidal flat fauna is presented. The comparison shows that the occurrence of macrofauna and especially of ecosystem engineers varies between sites, which can in turn explain the great variability in species abundance patterns recorded in benthic surveys of tidal flats within and between regions. This review revealed similarities as well as differences between various tropical tidal flats, which underlines the need for further comparative studies to be done, using the same methodology, before generalizations can be made.