Recovery timeframe is a critical component in preserving carbon stocks in disturbed tropical seagrass meadows

Abstract

Seagrass meadows, though covering a small percentage of the ocean floor, play a critical role in marine carbon sequestration. However, the mechanisms behind this role remain uncertain due to challenges in mapping seagrass extent and flux, accounting for spatial variation in carbon storage, and incorporating site-specific histories. This study investigates the effects of short-term (≤10 years) seagrass loss on sediment carbon stocks within a large seagrass meadow in the Great Barrier Reef region. Using remote sensing data to construct a seagrass recovery timeline, combined with field sampling and assessments of ecological factors, we found higher sediment organic carbon in areas where seagrass coverage was retained throughout the study period. Carbon stock and sediment accumulation varied with Recovery stage and were influenced by ecological factors and the length of seagrass absence. Minimal differences in sedimentary carbon stocks were observed between retained areas and those recovering within 3–8 years, suggesting limited disturbance impacts on carbon storage when recovery occurs within this timeframe. However, significant differences in carbon stocks were observed between persistent meadow areas and sites where no seagrass recovery had occurred for ≥10 years. The study meadow contained an estimated 39,779 Mg C (to 1 m), with spatial variation linked to seagrass loss and recovery history, as well as ecological and environmental factors. Our findings offer context to the permanence of seagrass Blue Carbon during meadow loss and suggest sedimentary carbon stocks can largely persist in similar systems experiencing cycles of seagrass loss and recovery that occur over 3-to-8-year timeframes.