Food availability in fjords is unusual among deep-sea environments due to the increased availability of nutritional sources that are comparatively rare in the open sea, such as influxes of macrophytodetritus and terrestrial organic matter. In open waters, these deep-sea ‘organic falls’ have been shown to increase beta diversity in comparison to surrounding, unenriched sediments, and support a range of specialised fauna. There has been unprecedented loss of coastal kelp forests in Norway and this is likely to greatly reduce the transfer of an important carbon subsidy to deep-sea communities in Norwegian fjords. In contrast, progress in terrestrial land management and reforestation has resulted in a large increase in the area covered by boreal forests. With such an expansion in forests fringing deep Norwegian fjords, an increase in the transport of wood material and forest detritus to these deep-sea habitats seems inevitable. Benthic landers containing experimental substrates (wood blocks and kelp parcels) were deployed for 10 months at a depth of 530 m in Osterfjorden, and stable isotope analysis (¹³C, ¹⁵N) was used to investigate and compare trophic relationships between wood and kelp substrates and the macrofauna that colonised them. Trophic shift analyses showed a dependence on kelp either as a direct dietary source or a primary source of carbon in most of the fauna analysed, whereas there was little evidence of wood providing an importance dietary subsidy. Modelling analyses showed that kelp detritus comprised a large percentage of the diet of all of the taxa collected from the kelp samples, and several from the wood samples. Ontogenetic trophic changes (i.e., differences in δ¹³C or δ¹⁵N depending on animal size) were seen in several of the taxa analysed, revealing changes in dietary preference and increasing trophic level as a function of size/age. This study provides evidence of the importance of kelp in the trophic ecology of communities living at the Norwegian deep-sea floor. The continued loss of kelp from shallow, coastal systems may have profound effects for these communities as they face a reduction in this important subsidy.

在深海环境中，峡湾的食物供应量是不寻常的，这是由于营养资源的供应量增加，而在海洋中这种营养资源的供应量相对较少，例如大型植物碎屑和陆生有机质的涌入。在开阔水域中，与周围未富集的沉积物相比，这些深海“有机瀑布”已显示出增加β多样性，并支持一系列特殊动物。挪威沿海海带森林遭受了前所未有的损失，这很可能会大大减少重要的碳补贴向挪威峡湾深海社区的转移。相反，陆地土地管理和植树造林的进展导致北方森林覆盖面积大大增加。随着森林的扩展，在挪威深峡湾的边缘，木材材料和森林碎屑向这些深海生境的运输增加似乎是不可避免的。在Osterfjorden的530 m深度处，将装有实验性底物（木块和海带包裹）的底栖着陆器部署了10个月，并进行了稳定的同位素分析（¹³ C，¹⁵ N）用于研究和比较木材和海带基质与定居在其上的大型动物之间的营养关系。营养变化分析表明，在大多数被分析的动物区系中，海带作为直接的饮食来源或主要的碳来源都依赖海带，而几乎没有证据表明木材可以提供重要的饮食补贴。建模分析表明，从海带样品中收集的所有分类单元的饮食中，海带碎屑占饮食的很大一部分，而从木材样品中收集的则占海藻碎屑的大部分。个体发育营养改变（即，在δ差异¹³ C或δ ¹⁵N取决于动物的大小）在所分析的几种分类中都可见到，揭示了饮食偏好的变化和营养水平随大小/年龄的变化。这项研究提供了海带在生活在挪威深海海底社区的营养生态中的重要性的证据。由于这些重要补贴的减少，沿海浅海系统持续损失的海带可能对这些社区产生深远的影响。