A high proportion of the kelp Laminaria hyperborea production is exported from kelp forests following seasonal storms or natural annual old blade loss. Transport of drifting kelp fragments can lead to temporary accumulations in benthic subtidal habitats. We investigated the degradation processes of L. hyperborea in a low subtidal sandy bottom ecosystem by setting up a 6‐month cage experiment to simulate accumulations of kelp fragments on the seafloor. We monitored temporal changes in biomass, nutritional quality (C:N ratio), respiration, quantum efficiency of photosystem II (F_v/F_m), bacterial colonization, and chemical defense concentrations. Biomass decomposition started after 2 weeks and followed a classic negative exponential pattern, leading to 50% degradation after 8 weeks. The degradation process seemed to reach a critical step after 11 weeks, with an increase in respiration rate and phlorotannin concentration in the tissues. These results likely reflect an increase in bacterial activity and a weakening of the kelp cell wall. After 25 weeks of degradation, only 16% of the initial biomass persisted, but the remaining large fragments looked intact. Furthermore, photosystems were still responding to light stimuli, indicating that photosynthesis persisted over time. Reproductive tissues appeared on some fragments after 20 weeks of degradation, showing a capacity to maintain the reproductive function. Our results indicate that L. hyperborea fragments degrade slowly. As they maintain major physiological functions (photosynthesis, reproduction, etc.) and accumulate on adjacent ecosystems, they may play a long‐term ecological role in coastal ecosystem dynamics.

中文翻译：

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降解动力学和与海带（海藻科）海带碎片积累相关的过程：原位实验方法。

海带高比例的北方海带产量从海带森林下面的季节性风暴或自然年的老叶片损失出口。海带碎片的运输可能导致底栖潮间带栖息地的临时积累。我们通过建立一个为期6个月的笼子实验来模拟海藻碎片在海底的积累，研究了低潮带下沙质底生态系统中高产李斯特菌的降解过程。我们监测了生物量，营养质量（C：N比），呼吸作用，光系统II（F _v / F _m），细菌定植和化学防御浓度。生物质分解在2周后开始，并遵循经典的负指数模式，在8周后导致50％的降解。11周后，降解过程似乎达到了关键的一步，呼吸速率增加，组织中的邻苯二酚浓度增加。这些结果可能反映了细菌活性的增加和海带细胞壁的减弱。降解25周后，只有16％的初始生物质得以保留，但其余的大碎片看上去完好无损。此外，光系统仍对光刺激作出反应，表明光合作用随时间持续存在。降解20周后，一些碎片上出现了生殖组织，显示出维持生殖功能的能力。L. hyperborea片段降解缓慢。由于它们维持主要的生理功能（光合作用，繁殖等）并在邻近的生态系统中积累，因此它们可能在沿海生态系统动态中发挥长期的生态作用。