Microbial-driven nitrogen cycle in coastal wetlands: Biodiversity, threats, and restoration strategies

Coastal wetlands serve as critical microbial reservoirs that bridge terrestrial and marine ecosystems and play an indispensable role in nitrogen cycling and in mitigating eutrophication. However, these essential functions are increasingly threatened by anthropogenic pressures and climate change. This review elucidates current research on the complex relationships among microbial diversity, nitrogen dynamics, and nitrogen transformation processes, emphasizing the importance of conserving and restoring microbial functions in coastal wetlands. In particular, the interdependence of microbial diversity, nitrogen cycle stability, and ecosystem health is highlighted, as a deeper understanding of these relationships is fundamental to developing effective conservation and restoration strategies. Beyond cataloging the diversity, this review develops a mechanistic framework that connects enzyme kinetics, electron-stoichiometric competition among denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anammox, and micro-scale redox structuring to ecosystem-scale nitrogen fluxes. Finally, potential threats to coastal wetland microbial communities and potential restoration strategies are highlighted to inform evidence-based policies to protect coastal wetlands.