Middle-Scale Spatial and Temporal Patterns in Estuaries: Rocky Intertidal Macrobenthic Communities in the Hangzhou Bay and Zhoushan Sea

Salinity gradient directly influences the composition and distribution of biological communities from upstream to downstream of the estuary. In this middle-scale study, a large dataset (10 rocky sections of 3 islands) of the Hangzhou Bay and Zhoushan Sea allowed thoroughly analyzing salinity and seasonal gradients and relating macrobenthos distributions and community structure to environment factors. In general, distinct regional differences were found in the distribution, diversity and community structures of macrobenthos. Abundance and biomass in all regions were dominated by suspension feeders and increased along the estuarine gradient. Significant seasonal differences were found in the abundance and biomass of herbivores, and significant regional differences were found in the abundance and biomass of suspension feeders. Redundancy analysis showed that water temperature was the dominant factor for the low-salt region, suspended particulate matter was the dominant factor for the mid-salt region, and water temperature as well as chlorophyll-a were the dominant factors for the high-salt region. These results showed that at a middle-scale estuary a considerable fraction of the variation in distribution and community structure of the intertidal macrobenthos correlated very well with environmental factors (salinity, water temperature, chlorophyll-a and suspended particulate matter).