Watanabe (2026): Macroalgal and seagrass species generate variable amounts of recalcitrant dissolved organic carbon in coastal Japan
Kenta Watanabe, Masakazu Hori, Atsushi Kubo, Hirotada Moki and Tomohiro Kuwae, IN: Communications Earth & Environment, https://doi.org/10.1038/s43247-026-03600-1
Dissolved organic carbon released from marine macrophytes is an important carbon sequestration pathway, but its recalcitrant fraction remains poorly quantified. Here, the authors quantified dissolved organic carbon release rates and recalcitrance using empirical data from macroalgal and seagrass species across cold-temperate to subtropical coastal Japan. Dissolved organic carbon release rates ranged from 5 to 462 µmol g-DW−1 d−1, with similar averages between macroalgae and seagrasses. Using degradation dynamics simulated with a reactivity continuum model, they estimated the mean recalcitrant fractions over 100-year timescale as 25% (17–34%, 95% credible interval) for seagrasses and 14% (11–16%) for macroalgae, corresponding to 8% (4–12%) and 4% (3–6%) of annual net primary production, respectively.