Habitat‐forming ecosystem engineers are the foundation of many marine ecosystems where they support diverse and productive food‐webs. A reduction in their patch size or density may affect the productivity, biodiversity and stability of these ecosystems. We determined the effects of different densities and patch sizes of Ecklonia radiata (the dominant kelp in southern Australia) on the secondary productivity, species richness, diversity and community structure of understory epifaunal invertebrates and how associated environmental covariates modified by kelp affected those patterns. We assessed sub‐canopy epifauna across 28 artificial reefs with transplanted E. radiata consisting of seven different patch sizes (0.12–7.68 m²) crossed with four kelp densities (0–16 kelp m⁻²) over two years. Epifaunal secondary productivity associated with both natural algal and standardised rope fibre habitats decreased with patch size and was elevated when kelp was absent, however, it was also high in natural habitat when there was a high density of kelp. Epifaunal productivity was positively associated with sub‐canopy light and water flow but negatively associated with the biomass of the dominant understory alga, Ulva sp. Epifaunal diversity declined with a reduction in reef size as did richness which correlated with a loss of algal species richness. Community structure of epifauna also differed between small and large reefs, between reefs with and without kelp, between rope habitats at the centre and at the edge of reefs, and within natural habitat between reefs supporting high and low densities of kelp. Overall, these results indicate complex effects of E. radiata decline on epifaunal communities, with high secondary productivity associated with dense kelp stands, but also areas without kelp that are dominated by turf algae. While the loss of standing kelp from rocky reefs may result in declines in epifaunal biodiversity, where turf algae replaces kelp, the reefs may still support high secondary productivity.

中文翻译：

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海带斑块的大小和密度影响表生动物的次级生产力和多样性

形成栖息地的生态系统工程师是许多海洋生态系统的基础，他们在其中支持多样化和生产性的食物网。它们斑块大小或密度的减小可能会影响这些生态系统的生产力，生物多样性和稳定性。我们确定了辐射密度（Ecklonia radiata）（澳大利亚南部的主要海藻）的不同密度和斑块大小对林下表层无脊椎动物的次生生产力，物种丰富度，多样性和群落结构的影响以及海藻修饰的相关环境协变量如何影响这些模式。我们评估子篷海底动物在28个人工鱼礁与移植E.辐射包括七个不同的贴片的尺寸（0.12-7.68米的²）在两年内以四种海带密度（0–16海带m ^-2）越过。与天然藻类和标准化绳索纤维栖息地相关的表观粪便次级生产力随斑块大小而降低，在海带不存在时提高，但在海藻密度高的自然栖息地中也较高。表生生产力与冠层下的光和水流量呈正相关，而与底层林下藻类Ulva的生物量呈负相关sp。表壳动物的多样性随着珊瑚礁大小的减少而减少，而丰富度则与藻类丰富度的丧失有关。表生动物的群落结构在大大小小的礁石之间，有和没有海藻的礁石之间，在礁石中心和边缘处的绳索栖息地之间以及在高密度和低密度海藻之间的自然栖息地内也不同。总体而言，这些结果表明辐射大肠埃希氏菌群落对表带群落的复杂影响，伴随着密集的海藻林以及不以海藻为生的草皮藻类占主导的地区，具有较高的次生生产力。虽然岩石礁石造成的海藻直立海带的丧失可能会导致表皮生物多样性的下降（用草皮藻代替海藻），但珊瑚礁仍可能支持较高的次级生产力。