Temporal and spatial distributions of intertidal macrobenthos in the sand flats of the Shuangtaizi Estuary, Bohai Sea in China

ABSTRACTThe intertidal macrobenthos in the sand flats of the Shuangtaizi Estuary, Bohai Sea in China, were investigated in the spring, summer, and autumn in 2013 to identify the macrobenthic community of species components, abundance, and biomass. Twenty-nine species were identified, and classified primarily as mollusks (45%), polychaetes (31%), and crustaceans (21%). The abundance and biomass of the macrobenthos in the intertidal zone of the Shuangtaizi Estuary exhibited distinct seasonal patterns; both factors were higher in summer (16,762 ind/m2 and 782.5 g/m2, respectively) than in spring or autumn. The intertidal macrobenthos displayed a remarkable vertical distribution, and exhibited typical characteristics of estuaries: polychaetes such as Perinereis aibuhitensis distributed in the high tidal zone. Mollusks, such as Bullacta exarata, Potamocorbula laevis, and Umbonium thomasi mainly inhabited the mid-tidal zone. The buried clams Mactra veneriformis and Meretrix meretrix were dominant in the mid-tidal and low tidal regions, where the two clams shared overlapping habitats to some extent. Moreover, these benthic species were also highly abundant in the sections near the Shuangtaizi River mouth (23,661 ind/m2), but were detected as a high biomass in the sections far from the mouth (1492.9 g/m2). The bivalve P. laevis and M. veneriformis primarily contributed to the abundance and biomass of mollusks. The average Shannon–Wiener, evenness, and species richness indices of the intertidal macrobenthos in the estuary were 0.83, 0.37, and 0.45, respectively. The surface sediments in the intertidal zone consisted mainly of clay, silt sand, fine-grained sand, and sand types, which were closely related to the distributions of macrobenthos. Our study suggests that the Shuangtaizi Estuary is an important shellfish fishery, and the high abundance and biomass of P. laevis and U. thomasi can be exploited further. However, effective measures should be implemented to protect and restore the population of the clam M. meretrix.