Patterns and drivers of beta diversity of subtidal macrobenthos community on the eastern coast of Laizhou Bay

Abstract

Aims: The formation and maintenance mechanism of the beta diversity pattern of biological communities have always been the focus and core of community ecology. However, the patterns and drivers of the beta diversity in marine ecosystems are still unclear, especially in marine benthic ecosystems in China. By studying the relationship of beta diversity (taxonomic-and functional trait-based) and its turnover and nestedness components of subtidal macrobenthos communities with environmental variables and spatial distance, we aimed to reveal the underlying processes of community assembly on the eastern coast of Laizhou Bay and provide guidance for studying the beta diversity of macrobenthos communities in other regions. Methods: We sampled the macrobenthic organisms and corresponding environmental data (e.g., water temperature, salinity, dissolved oxygen, and sediment factors) at 15 stations in the subtidal zone on the eastern coast of Laizhou Bay. We collected six biological traits i.e., adult body size, habitat position, living habit, mobility, feeding habit and AZTI’s marine biotic index (AMBI) ecological groups for all sampled macrobenthos species. We calculated the taxonomic and functional trait beta diversity of macrobenthic communities and quantified the relative contributions of turnover and nestedness to beta diversity. In addition, the Mantel test and multiple regression on distance matrices (MRM) analysis were employed to determine the effect of environmental variables and spatial distance on the taxonomic and functional trait beta diversity and their components of macrobenthic communities. Results: We recorded 75 macrobenthos species in the study area, which was dominated by polychaetes (61.33%), followed by crustaceans (17.33%) and mollusks (14.67%). Both the taxonomic and functional beta diversity of macrobenthic communities on the eastern coast of Laizhou Bay were high and dominated by the turnover component. This indicates that there were large differences in the composition of species and functional traits of the macrobenthos in the study area, which were caused by the replacement of species and/or functional traits in space or between communities. (2) Spatial geographical distance had no significant effect on the taxonomic and functional beta diversity and their components of macrobenthic communities (Mantel test, P > 0.05), indicating that the impact of dispersal limitation on macrobenthic communities was small. (3) Multiple regression on distance matrices (MRM) analysis showed that sediment-related environmental factors, namely total organic matter (TOM) and silt content, are the main factors driving the taxonomic beta diversity of macrobenthic communities, while the functional trait beta diversity was significantly affected by TOM. Conclusion: Our results support that environmental filtrating was the dominant ecological process structuring macrobenthic communities, both in taxonomic and functional trait composition, in the subtidal zone on the eastern coast of Laizhou Bay. These findings highlight the need to examine both taxonomic and functional diversity to understand the mechanisms that govern the assembly of macrobenthos communities in subtidal zones. In addition, this study may have profound implications for understanding the macrobenthos community assembly in other sea areas in China.