How vegetation influence the macrobenthos distribution in different saltmarsh zones along coastal topographic gradients

Abstract

Macrobenthos are a key constituent of coastal salt marsh ecosystems and have often been used as sensitive indicators of the environment quality. In this study, field investigations in vegetated regions and adjacent bare patches of low, middle and high marshes were conducted to explore whether and how vegetation influence the macrobenthos distribution in different saltmarsh zones along coastal topographic gradients. Results showed that vegetation positively or negatively influenced macrobenthos mainly by changing their environment in different saltmarsh zones, as there were different degrees of physical stresses and food supply for the macrobenthos from the low to the high marsh. In the low marsh, no major differences in macrobenthos indices between the bare and vegetated sediments were found, yet density and biomass of the molluscs were higher in the bare patches. In the middle marsh, vegetation promoted the biomass and diversity indices but not the density and species richness of the macrobenthos, and vegetation was beneficial for some types of crustaceans but was detrimental for some types of polychaetes. In the high marsh, vegetation promoted the biomass, density, and species richness of the macrobenthos compared to those of adjacent bare patches. Coastal topographic gradients also had effects on macrobenthos distribution consistently with different habitat preferences and ecological niches, and the low marsh had the highest species richness, Shannon diversity, Pielou evenness and Margalef richness. This study also provided scientific implications for the management and restoration of the ecosystems in different intertidal saltmarsh zones.

Keywords: Environmental factors; Macrobenthos; Management implication; Saltmarsh; Topographic gradients; Vegetation.