ABSTRACT: Kelps are highly productive macroalgae that form habitats along one-quarter of the worlds’ coastlines. Emerging evidence suggests that kelps have the potential to sequester carbon through the export of detritus to deep marine sinks, yet how much of this detrital carbon is remineralized through grazing and microbial decomposition before it reaches these sinks remains a critical knowledge gap. We measured decay of Laminaria hyperborea detritus in shallow kelp forests (10 m) and adjacent deep fjords (300 m), and experimentally tested the effect of temperature and oxygen conditions similar to those at these habitats in ex situ experiments. Initial decay rate (k) was high (-0.107 to -0.183 d^-1) with 40-60% of the original carbon biomass being lost within few weeks, after which decay rates slowed down (k = -0.009 to -0.038 d^-1). Temperature had little effect on the rate and extent of decomposition within the temperature range tested (4-10°C). Blade detritus decomposed almost completely in 300 d under aerobic conditions. Anaerobic decay of both blade and stipe detritus ceased, in contrast, after 150-200 d, leaving 20-30% of the initial biomass to decompose extremely slowly or not at all. Decomposition was followed by changes in chemical composition; C:N ratios increased substantially, while mannitol and phenolics disappeared almost completely from the detritus matrix. Slow and incomplete anaerobic decomposition suggest that the potential for long-term burial and sequestration of kelp carbon will be enhanced if detritus is exported to nearby deep areas with permanent or periodic hypoxia near the bottom.

中文翻译：

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海藻碎屑的不完全厌氧分解提高了固碳潜力

摘要：海带是高产的大型藻类，形成了世界四分之一海岸线上的栖息地。新兴证据表明，海藻有可能通过将碎屑输出到深海海槽中而将碳封存，但是，通过放牧和微生物分解将这些碎屑碳重新矿化之前，海藻仍然是一个关键的知识缺口。我们在浅海带森林（10 m）和邻近的深峡湾（300 m）中测量了海带海带碎屑的衰减，并在异地实验中实验测试了与这些生境相似的温度和氧气条件的影响。初始衰减率（k）高（-0.107至-0.183 d ^-1），原始碳生物量的40-60％在几周内损失了，此后衰减速率减慢了（k = -0.009至-0.038 d ^-1）。在测试的温度范围（4-10°C）内，温度对分解的速率和程度影响很小。在有氧条件下，叶片碎屑在300天内几乎完全分解。相反，叶片和刀柄碎屑的厌氧性腐烂在150-200 d后就停止了，剩下20-30％的初始生物质非常缓慢地分解或根本不分解。分解后化学成分发生变化。C：N比大大增加，而甘露醇和酚类物质几乎完全从碎屑基质中消失。缓慢而不完全的厌氧分解表明，如果碎屑出口到附近底部具有永久性或周期性缺氧的深部区域，则长期埋葬和隔离海带碳的潜力将会增加。