Anthropogenic stressors are impacting the structure and function of natural ecosystems worldwide. Functionally important soft-sediment ecosystems in estuaries are under threat from multiple stressors, including sea-level rise. Understanding and predicting the impacts of sea-level rise on benthic communities is an important challenge. Here we provide the results of a global meta-analysis, based on more than 900 data points worldwide, analysing the relationships between environmental variables, macrofauna community, and ecosystem function metrics from estuarine intertidal and subtidal zones. Intertidal and subtidal zones in estuaries were found to be significantly different in terms of macrobenthic community composition and ecosystem function. The differences in the relationships between environmental variables, macrofauna community composition, and ecosystem function indicates a complex set of relationships that are likely to be impacted by periodic exposure to air (intertidal) versus permanent inundation (subtidal). These results indicate that physical setting (intertidal or subtidal) impacts a hierarchy of processes influencing ecosystem function, altering not only individual variables but interactions and feedback mechanisms. We found that the limiting effects of sediment mud and organic content on macrobenthic communities varied between intertidal and subtidal zones, where richness and abundance were limited at lower levels of mud in the intertidal relative to the subtidal. We found that measures of macrofaunal may richness and abundance, as drivers of oxygen production and consumption, had different driver-response relationships in intertidal and subtidal zones. These differences in driver-response mechanisms between sedimentary environment, macrobenthic communities, and ecosystem functions based on physical setting suggest that, as intertidal zones transition to subtidal with increasing sea level rise, the net functions of estuaries could be fundamentally altered as structuring and feedback mechanisms adapt. This may lead to a net change in estuarine functioning worldwide, potentially reducing important ecosystem services such as food provisioning, nitrogen cycling and resilience to stressors. • >900 globally distributed datapoints from >280 journal articles • Intertidal zones host more abundant but less taxa-diverse macrofauna communities than subtidal zones • Macrofaunal richness and abundance show contrasting relationships with oxygen production and consumption in intertidal compared with subtidal zones. • Relationships between environment, community composition and ecosystem function metrics are complex and context dependent • Sea-level rise will likely impact macrofaunal communities and ecosystem function in estuaries around the world
Petersen et al. (Fri,) studied this question.