Modelling carbon dynamics in Posidonia oceanica using dynamic energy budget theory

Posidonia oceanica is a foundation species whose meadows structure Mediterranean coastal seascapes and drive key biogeochemical processes, ranking among the most productive and biodiverse ecosystems in the region. These meadows are also major sinks of blue carbon per unit area, yet their extent is declining due to eutrophication, mechanical damage, climate change, and invasive species. Understanding how the plant adjusts carbon fluxes to environmental conditions is therefore critical for both blue carbon accounting and meadow restoration. To this end, we developed the first ecophysiological model of P. oceanica based on dynamic energy budget (DEB) theory, explicitly accounting for carbon acquisition, loss, and internal redistribution as functions of environmental drivers. Implemented in the Julia high-performance programming language, the model adopts a multi-compartment structure (above- and below-ground), with environmentally dependent fluxes and full propagation of uncertainties. By coupling the model with Bayesian inference applied to high-resolution, multi-year time series of incident light, water transparency, and temperature, we demonstrate its ability to accurately reconstruct past carbon fluxes and project future dynamics. Our results show that the DEB framework not only improves mechanistic understanding of carbon metabolism in seagrasses but also provides actionable information for the restoration of P. oceanica meadows.