Topographic and hydrodynamic complexity in submarine canyons promotes steep gradients in food availability and geophysical parameters which affect ecological assemblages and beta diversity. While habitat heterogeneity in submarine canyons is known to support diverse and abundant megafaunal communities, due to difficulty in sampling little is known about infaunal communities adjacent to hard substrate habitats, their contribution to canyon assemblages, and overall deep-sea diversity. Sediments were collected in three distinct habitat types: within Norfolk Canyon (western Atlantic) adjacent to hard substrate habitats including canyon walls and large boulders, along the main axis of the canyon, and on the adjacent continental slope to quantify macrofaunal (>300 μm) density, diversity and community composition, and sediment geochemical parameters including grain size, organic content, and stable isotope composition. While macrofaunal densities were similar among habitats sampled at comparable depths, diversity was higher near the hard substrate environments. Discrete communities were present in each habitat type, while annelid functional composition was similar between hard substrate adjacent and canyon axis habitats. Although diversity and abundance of hard substrate adjacent sediment communities did not change with depth, communities were driven by sediments with low organic matter content, whereas canyon and slope community assemblages were best explained by depth and higher organic content. Beta diversity among hard substrate adjacent sediments and canyon axis communities was high, with 27% of canyon taxa and 10% of regional taxa only occurring in hard substrate habitats. Given the thousands of submarine canyons worldwide, our results highlight the overall importance of substrate habitat heterogeneity within canyons in supporting deep-sea benthic diversity and suggest that both within-canyon and regional diversity are underestimated.

海底峡谷的地形和水动力复杂性促进了粮食供应和地球物理参数的陡峭梯度，从而影响了生态组合和贝塔多样性。虽然已知海底峡谷中的栖息地异质性支持多样化和丰富的巨型动物群落，但由于采样困难，人们对与硬质基质栖息地相邻的非动物群落，它们对峡谷组合的贡献以及整个深海多样性知之甚少。在三种不同的栖息地类型中收集了沉积物：沿着峡谷的主轴线，在诺福克峡谷（西大西洋）内，毗邻硬质基质栖息地（包括峡谷壁和大石块），沿着峡谷的主轴线，以及在相邻的大陆坡上量化了大型动物（> 300μm）密度，多样性和社区组成，沉积物地球化学参数，包括粒度，有机物含量和稳定的同位素组成。虽然在可比较深度的栖息地中大型动物的密度相似，但在硬质底物环境附近的多样性更高。每种生境类型中都存在离散的群落，而邻近硬质底物的生境和峡谷轴生境之间的突触功能组成相似。尽管硬质基底沉积物群落的多样性和丰度没有随深度变化，但群落是由有机质含量较低的沉积物驱动的，而峡谷和斜坡群落的组合最好由深度和较高的有机质来解释。邻近沉积物和峡谷轴社区的硬质基质中的β多样性很高，其中27％的峡谷分类单元和10％的区域分类单元仅发生在坚硬的基质栖息地中。鉴于全球范围内有数以千计的海底峡谷，我们的结果突出了峡谷内底物栖息地异质性在支持深海底栖生物多样性方面的总体重要性，并表明低估了峡谷内和区域内的多样性。