Global Patterns on Nutrient Release During Leaf Litter Decomposition in Blue Carbon Ecosystems

Nutrient release during litter decomposition is the mineralization of organically bound nutrients into inorganic and soluble forms. However, it remains unknown whether warming increases macro-nutrient release during leaf litter decomposition. Through a global meta-analysis, we incorporated the relationships between nutrient release rate constants (k_NP) and leaf litter decomposition rate constants in coastal blue carbon ecosystems (BCE) into numerical models to forecast nutrient release. Average k_NP ranged from 0.006 to 0.035 d⁻¹ for nitrogen and 0.003–0.019 d⁻¹ for phosphorus with lower values in temperate than (sub)tropical zones. Our findings suggest that nutrient release during leaf litter decomposition will increase with rising temperatures under two scenarios: the IPCC representative concentration pathway 8.5 and the IPCC 1.5–4°C warming compared with the pre-industrial period. Leaf litter nutrient release in mangrove forests and tidal marshes is more sensitive to warming than that in seagrass beds. Leaf litter processing and consumption by benthic fauna during decomposition will lead to lower nutrient release in 2100 compared to 2050 due to global warming. We conclude that warming will intensify, while decreased macrobenthos activity will reduce, leaf litter nutrient release.