Characterizing the diversity and distribution of tropical coastal blue carbon using environmental DNA.

Tropical coastal blue carbon is stored in shallow-water ecosystems such as mangrove forests, seagrass meadows, and macroalgal beds. Carbon is also exported from these ecosystems offshore and into sediment pools as cellular organic carbon that comprises DNA, among other components. Environmental DNA (eDNA) has recently shown promise in the identification and quantification of macrophytes from coastal sediment and seawater. Here, we test an eDNA approach for detecting and characterizing tropical blue carbon, uncovering significant seasonal patterns in tropical coastal macrophyte communities with high site fidelity. Results underscore important environmental constraints on eDNA monitoring of tropical blue carbon, including high temperatures and rainfall, which can impact eDNA residence time and detection levels. There remains a critical need to improve reference DNA databases and protocols to more precisely characterize macrophyte communities. These findings contribute to the development of an eDNA-based monitoring system to track nearshore stocks and fluxes of tropical blue carbon.