Richness, diversity, biomass, and endangered species of macrobenthic fauna from tidal flats in Japan

We quantitatively collected macrobenthos in 10 tidalflats from the Ryukyus Islands to Hokkaido, and compared species richness, biomass, species diversity and evenness, and number of endangered species between the tidalflats. Species diversity indices were calculated for each tidalflat by the number of species and ratios of wet weight for each species. Biomass classified the tidalflats into the clam-, polychaete-, and others-dominated. One or some of rhizopods, crustaceans, snails, polychaetes, and fish was/were dominant in the others-dominated one(s). Clams or snails were dominant in the most sandy tidalflats and polychaetes were in the most sandy-muddy and muddy ones. There was a positive relationship between the average number of species sampled per area (species richness) and the wet weight collected per area (biomass). Evaluations of species diversity by Shannon-Wiener's H', E, Simpson's D and relative abundance curve were generally consistent one another. However, the trends of these parameters were not necessarily consistent with the trends of species richness and biomass. Endangered species were most abundant in two tidalflats from the Ariake Sound which evaluations were neither high with respect to species richness nor biomass. Besides, in one of these tidalflats the evaluations were low with respect to indices of species diversity. The results suggest that multi-dimensional comparisons are needed to evaluate the benthic community in the tidalflats.