ABSTRACT: Coastal habitats dominated by marine macroalgae typically exhibit high rates of primary productivity and play a key role in local and regional carbon cycles and stores. In temperate regions, large brown algae (i.e. kelps and fucoids) contribute significantly to macroalgal primary production, most of which is exported from source habitats as detritus. The ultimate fate of this detritus and the processes controlling detrital pathways into food webs and carbon cycles remain poorly understood. Based on field surveys, we quantified the biomass of kelp-derived detritus (wrack) at sandy and pebble-dominated shores in Ireland and conducted a manipulative field experiment to test for inter-specific differences in detritus degradation rates and the effect of macroinvertebrate detritivores. Overall, accumulated wrack biomass was similar on all shores but varied temporally depending on habitat type. Degradation rates and the nutritional (C:N) and chemical (polyphenol concentrations) properties differed among kelp species. Interestingly, exclusion of macroinvertebrate detritivores did not affect kelp degradation rates, C:N ratios or polyphenol content. Our findings show that rates of macroalgal breakdown differ among kelp species and that, in contrast to other aquatic systems, macroinvertebrates appear to play a very limited role in the breakdown of these marine detrital subsidies, suggesting a key role for meiofauna and microbes in detritus processing. Increasing recognition for the role of detritus in coastal food webs and carbon cycles warrants a better understanding of the mechanisms underpinning degradation rates.

中文翻译：

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海滩铸造海带（残骸）沉积的时空变异性和降解率的种间差异

摘要：以海洋大型藻类为主的沿海栖息地通常表现出较高的初级生产力，并在当地和区域碳循环和储存中发挥关键作用。在温带地区，大型褐藻（即海带和岩藻藻类）对大型藻类初级生产有显着贡献，其中大部分作为碎屑从来源栖息地输出。这种碎屑的最终命运以及控制碎屑进入食物网和碳循环的过程仍然知之甚少。基于实地调查，我们量化了爱尔兰以沙质和卵石为主的海岸的海带衍生碎屑（残骸）的生物量，并进行了操纵性现场实验，以测试碎屑降解率的种间差异和大型无脊椎动物碎屑的影响。总体，所有海岸上累积的残骸生物量都相似，但随栖息地类型的不同而随时间变化。海带种类之间的降解率和营养（C:N）和化学（多酚浓度）特性不同。有趣的是，排除大型无脊椎动物碎屑不会影响海带降解率、C:N 比或多酚含量。我们的研究结果表明，大型藻类分解率因海带物种而异，并且与其他水生系统相比，大型无脊椎动物在这些海洋碎屑补贴的分解中发挥的作用似乎非常有限，这表明小型动物和微生物在碎屑加工中的关键作用. 越来越多地认识到碎屑在沿海食物网和碳循环中的作用，需要更好地了解支持降解率的机制。