Barksdale Mary Bryan, Hein Christopher J, Kirwan Matthew L
Virginia Institute of Marine Science, William & Mary, P.O. Box 1346, Gloucester Point, VA, 23062, USA.
Nat Commun. 2023 Dec 19;14(1):8425. doi: 10.1038/s41467-023-42942-8.
Landward migration of coastal ecosystems in response to sea-level rise is altering coastal carbon dynamics. Although such landscapes rapidly accumulate soil carbon, barrier-island migration jeopardizes long-term storage through burial and exposure of organic-rich backbarrier deposits along the lower beach and shoreface. Here, we quantify the carbon flux associated with the seaside erosion of backbarrier lagoon and peat deposits along the Virginia Atlantic Coast. Barrier transgression leads to the release of approximately 26.1 Gg of organic carbon annually. Recent (1994-2017 C.E.) erosion rates exceed annual soil carbon accumulation rates (1984-2020) in adjacent backbarrier ecosystems by approximately 30%. Additionally, shoreface erosion of thick lagoon sediments accounts for >80% of total carbon losses, despite containing lower carbon densities than overlying salt marsh peat. Together, these results emphasize the impermanence of carbon stored in coastal environments and suggest that existing landscape-scale carbon budgets may overstate the magnitude of the coastal carbon sink.
沿海生态系统为应对海平面上升而向陆地迁移正在改变沿海碳动态。尽管这些地貌能迅速积累土壤碳，但障壁岛的迁移会危及长期碳储存，因为富含有机物的后滨沉积物会在低潮滩和滨面被掩埋和暴露。在此，我们量化了弗吉尼亚大西洋沿岸后滨泻湖和泥炭沉积物向海侵蚀所产生的碳通量。障壁岛海侵每年导致约26.1千兆克有机碳的释放。近期（公元1994 - 2017年）的侵蚀速率比相邻后滨生态系统的年土壤碳积累速率（1984 - 2020年）高出约30%。此外，尽管厚层泻湖沉积物的碳密度低于上覆盐沼泥炭，但滨面侵蚀造成的碳损失占总碳损失的80%以上。这些结果共同强调了沿海环境中储存碳的不稳定性，并表明现有的景观尺度碳预算可能高估了沿海碳汇的规模。
