Global Review of Blue Carbon Ecosystem Microbial Communities.

Microbial communities underpin biogeochemical processes in Blue Carbon Ecosystems (BCEs); however, a comprehensive review of geographic patterns in microbial diversity, microbial functions, and distribution is currently lacking. Here, for the first time, we have analysed 70 years (1930-2020) of archaeal, bacterial, and fungal diversity and functions in mangrove, saltmarsh, and seagrass ecosystems to elucidate publication and geographic trends in reporting data in BCEs and to identify knowledge gaps. Of the 649 journal articles analysed, research on BCE microbial communities has focused overwhelmingly on assessing bacterial richness and functions in BCEs. Our gap analysis revealed that only ~25%-50% of the countries that have BCEs have been represented, suggesting that our understanding of archaeal, bacterial, and fungal geographic diversity in BCEs is still incomplete. In the context of taxonomic-based limitations in our study's approach, we have identified gaps of knowledge in archaeal and fungal sediment biodiversity in saltmarsh and seagrass ecosystems. This significantly impacts our ability to forecast ecosystem services amid current and future human and climate pressures in BCEs. The results from this synthesis could serve as a useful reference for microbial baseline data and research trends in BCEs to develop novel hypothesis-testing research.