Rhodolith beds increase the seabed complexity and are hotspots of biodiversity. Despite the crucial ecosystem services provided by rhodoliths, they are threatened by global change and local anthropogenic impacts. In this study, conducted on one of the largest beds of calcareous algae in the world located on the continental shelf of eastern Brazil, we tested whether the higher complexity of the seabed within rhodolith beds could explain the spatial biodiversity patterns of free-living nematodes. Our results show that beds with the highest densities of rhodoliths are associated with higher sedimentary organic matter (OM) contents and by a different biochemical composition. The higher OM nutritional quantity and nutritional quality, as shown by higher biopolymeric C contents and higher values of the protein to carbohydrate ratio, respectively, were associated with higher abundance, biomass, and diversity of nematode genera, thus supporting our hypothesis. Though based on a correlative approach, the results of this study suggest that a decrease in density of rhodoliths caused by human impacts may affect benthic biodiversity and, consequently, the range of ecosystem services they provide.

红石床增加了海床的复杂性，是生物多样性的热点。尽管红石提供了重要的生态系统服务，但它们仍受到全球变化和当地人为影响的威胁。在这项研究中，我们在位于巴西东部大陆架的世界上最大的钙质藻类床之一上进行，我们测试了红石床内海床的更高复杂性是否可以解释自由生活线虫的空间生物多样性模式。我们的结果表明，红石密度最高的床与较高的沉积有机质 (OM) 含量和不同的生化成分有关。更高的 OM 营养量和营养质量，分别表现为更高的生物聚合 C 含量和更高的蛋白质与碳水化合物比值，与线虫属的更高丰度、生物量和多样性相关，从而支持我们的假设。虽然基于相关方法，但这项研究的结果表明，人类影响引起的红石珊瑚密度降低可能会影响底栖生物多样性，从而影响它们提供的生态系统服务范围。