Data from: Effects of small-scale, shading-induced seagrass loss on blue carbon storage: Implications for management of degraded seagrass ecosystems

1. Seagrass meadows are important global ‘blue carbon’ sinks. Despite a 30% loss of seagrasses globally during the last century, there is limited empirical research investigating the effects of disturbance and loss of seagrass on blue carbon stocks. 2. In this study, we hypothesised that seagrass loss would reduce blue carbon stocks. Using shading cloth, we simulated small-scale die-offs of two subtropical seagrass species, Halodule wrightii and Thalassia testudinum, in a dynamic northern Gulf of Mexico lagoon. The change in quantity and quality of sediment organic matter and organic carbon were compared among kill, control and bare plots before the kill treatment, shortly after the kill treatment and 11 months after the kill treatment. 210 Pb age dating was performed on bare and Thalassia plots at 11 months to evaluate the impact of sediment erosion in the absence of vegetation. 3. The small-scale die-off led to a 50-65% organic matter (OM) loss in the sediment in the top 8 cm of Halodule plots. Thalassia plots lost significant portions OM (50%) and organic carbon (C; 21-47%) in only the top 1 cm of sediment. The 210 Pb profiles indicated Thalassia die-off reduced the C sequestration rate by 10%, in addition to a loss of ~1 years’ worth of C stocks (~22 g m-2<). Furthermore, analyses on O Morg quality indicated a loss of labile OM/C and enhanced remineralisation by microbes. 4. Synthesis and applications: This study provides empirical evidence that small-scale shading-induced seagrass die-offs can reduce seagrass carbon sequestration capacity and trigger losses of blue carbon stocks. While the losses recorded here are modest, these losses in blue carbon storage capacity are notable due to the proximity of shading structures (for example, boat docks) to seagrass habitats. Thus, policies to avoid or protect seagrass habitats from common small-scale, shading disturbances are important for optimising both carbon sequestration capacity and coastline development and management.17-Nov-2017

1. 海草床（seagrass meadows）是全球重要的“蓝碳（blue carbon）”汇。尽管上个世纪全球海草资源流失达30%，但针对海草受干扰及消亡对蓝碳储量影响的实证研究仍相对匮乏。
2. 本研究提出假说：海草消亡会降低蓝碳储量。研究人员借助遮光布，在墨西哥湾北部一座动态潟湖中模拟了两种亚热带海草物种——莱特氏海菖蒲（Halodule wrightii）与海龟草（Thalassia testudinum）的小规模枯萎事件。分别在处理前、处理后即刻以及处理后11个月，对比了枯萎样地、对照组与裸地区沉积物有机质（organic matter, OM）与有机碳的数量及质量变化。处理后11个月时，研究人员对裸地区与海龟草样地开展了铅210（210Pb）年代测定，以评估无植被覆盖下的沉积物侵蚀影响。
3. 小规模枯萎事件使得莱特氏海菖蒲样地0~8cm表层沉积物中的有机质损失达50%~65%。海龟草样地仅在0~1cm表层沉积物中出现了显著的有机质损失（50%）与有机碳损失（21%~47%）。铅210年代剖面结果显示，海龟草枯萎不仅造成了约合1年碳储量的碳损失（约22 g·m⁻²），还使碳固存速率降低了10%。此外，有机质质量分析表明，易降解有机质/有机碳发生流失，同时微生物的矿化作用显著增强。
4. 综合与应用：本研究通过实证证实，小规模遮光诱导的海草枯萎事件会削弱海草的碳固存能力，并引发蓝碳储量损失。尽管本次研究记录的损失幅度较为温和，但由于遮光设施（例如船坞）与海草生境距离较近，这类蓝碳储存能力的损失仍不容忽视。因此，制定政策以规避或保护海草生境免受常见的小规模遮光干扰，对于优化碳固存能力以及海岸线开发与管理均具有重要意义。2017年11月17日