ANIMAL TRACES ON A TIDAL FLAT IN HANGZHOU BAY, CHINA

Despite prevailing low salinity (S ranging from 1 to 10) of the Hangzhou Bay, its extensive (up to 2 km wide) flats along the northern coast have a species-rich macrobenthic fauna of crustaceans, bivalves, gastropods and polychaetes. These produce a variety of crawling, feeding, dwelling and resting traces, some comparable to those observed on the flats of Korea and Taiwan. The characteristic star-like feeding traces of the bivalve Tellina (Moerella) iridescens are described here for the first time. Sediment reworking appears to be largely confined to the surface layer. The burrow-inhabiting crabs are also mainly surface sediment feeders. These Chinese flats lack organisms reworking deeper sediment layers such as lugworms or callianassid crustaceans. As compared to the Wadden Sea, sedimentation rate is higher and subsurface sediment reworking less intense, resulting in relatively few bioturbation structures in vertical sections of the Hangzhou tidal flat sediments.