Macroalgae drive the largest CO₂ flux fixed globally by marine macrophytes. Most of the resulting biomass is exported through the coastal ocean as detritus and yet almost no field measurements have verified its potential net sequestration in marine sediments. This gap limits the scope for the inclusion of macroalgae within blue carbon schemes that support ocean carbon sequestration globally, and the understanding of the role their carbon plays within distal food webs. Here, we pursued three lines of evidence (eDNA sequencing, Bayesian Stable Isotope Mixing Modeling, and benthic‐pelagic process measurements) to generate needed, novel data addressing this gap. To this end, a 13‐month study was undertaken at a deep coastal sedimentary site in the English Channel, and the surrounding shoreline of Plymouth, UK. The eDNA sequencing indicated that detritus from most macroalgae in surrounding shores occurs within deep, coastal sediments, with detritus supply reflecting the seasonal ecology of individual species. Bayesian stable isotope mixing modeling [C and N] highlighted its vital role in supporting the deep coastal benthic food web (22–36% of diets), especially when other resources are seasonally low. The magnitude of detritus uptake within the food web and sediments varies seasonally, with an average net sedimentary organic macroalgal carbon sequestration of 8.75 g C·m⁻²·yr⁻¹. The average net sequestration of particulate organic carbon in sediments is 58.74 g C·m⁻²·yr⁻¹, the two rates corresponding to 4–5% and 26–37% of those associated with mangroves, salt marshes, and seagrass beds, systems more readily identified as blue carbon habitats. These novel data provide important first estimates that help to contextualize the importance of macroalgal‐sedimentary connectivity for deep coastal food webs, and measured fluxes help constrain its role within global blue carbon that can support policy development. At a time when climate change mitigation is at the foreground of environmental policy development, embracing the full potential of the ocean in supporting climate regulation via CO₂ sequestration is a necessity.

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相连的大型藻类沉积系统：沿海深海中的蓝碳和食物网

大型藻类驱动最大的CO ₂排放由海洋大型植物在全球范围内固定的通量。产生的大部分生物质以碎屑的形式通过沿海海洋出口，但几乎没有现场测量结果证明了其潜在的净沉积物在海洋沉积物中的吸收。这种差距限制了将大型藻类纳入支持全球范围内海洋碳固存的蓝色碳计划中的范围，并限制了其在远端食物网中所起的作用的理解。在这里，我们采用了三条证据线（eDNA测序，贝叶斯稳定同位素混合模型以及底栖-上浮过程测量）来生成需要的新颖数据，以弥补这一空白。为此，在英吉利海峡和英国普利茅斯周围的海岸线的一个深海沿岸沉积地点进行了为期13个月的研究。eDNA测序表明，周围海岸大多数大型藻类的碎屑都发生在深海沿海沉积物中，碎屑的供应反映了单个物种的季节性生态。贝叶斯稳定同位素混合模型[C和N]强调了其在支持深海底栖食物网（占饮食的22–36％）中的重要作用，特别是在其他资源季节性不足的情况下。食物网和沉积物中碎屑的吸收量随季节变化，平均沉积净有机大藻类净碳固存量为8.75 g C·m 特别是在其他资源季节性不足的情况下。食物网和沉积物中碎屑的吸收量随季节变化，平均沉积净有机大藻类净碳固存量为8.75 g C·m 特别是在其他资源季节性不足的情况下。食物网和沉积物中碎屑的吸收量随季节变化，平均沉积净有机大藻类净碳固存量为8.75 g C·m^-2 ·yr ^-1。沉积物中颗粒有机碳的平均净螯合为58.74 g C·m ^-2 ·yr ^-1，这两个比率分别对应于红树林，盐沼和海草床的比率的4–5％和26–37％，系统更容易被识别为蓝碳栖息地。这些新颖的数据提供了重要的初步估计，有助于将宏观藻类-沉积物连通性对深海沿海食物网的重要性进行情境化，而测得的通量有助于将其作用限制在可以支持政策制定的全球蓝碳中。在减缓气候变化成为环境政策制定的重中之重之际，要充分利用海洋在通过CO支持气候调节方面的全部潜力₂隔离是必要的。