The Impact of Seagrasses Disappearance on the Marine Phosphorus Cycle

Seagrasses are marine plants that play a crucial role in climate change mitigation through carbon sequestration. This process relies heavily on nutrients, e.g., phosphorus (P), which is often limiting in marine environments. However, the complex dynamics between seagrasses and P reservoirs remain poorly understood. Moreover, seagrasses are rapidly disappearing worldwide at alarming rates, making it crucial to study their impact on the marine P cycle, particularly in light of their decline. Here, we investigate P speciation in seagrass-influenced sediments, bioavailability, and transformations during seagrasses decomposition. The P distribution within the plant exhibits correlation with elongation as the young leaves contain more P than the old leaves, indicating the plant’s P allocation efficiency. This is further explored in decomposition experiments which reveal that aboveground biomass releases more P than belowground biomass. These findings underscore the critical influence of seagrass on P dynamics amid global seagrass decline.