Sediment effects on interstitial faunal distribution in Brazilian sandy beaches: a multi-phylum approach

Context In sandy beaches, the interstitial system, i.e. spaces among sand grains, forms a habitat that supports a diversity of microorganisms, as meiofauna. The interstitial fauna exhibits wide richness and diversity. Sediment-specific impacts on these communities remain understudied from a broader perspective. Aims To describe the interstitial fauna by using a multi-phylum approach and to explore the influence of variations in sediment characteristics at both mesoscale (within a beach) and macroscale (among beaches). Methods We sampled 10 sandy beaches, performed granulometric analyses, and searched for potential associations between community assemblages and sediment characteristics. Key results Eight phyla were identified, exhibiting a patchy distribution pattern at the mesoscale. Coarse-, medium- and fine-sediment assemblages differed significantly. At the macroscale, phylum preference for sediment type (coarse, medium and fine) was observed, where annelids, flatworms and nemerteans were abundant in the coarse sediment, and nematodes in the fine sediment. Conclusions Sediment, along with other ecological factors, plays a role in determining the richness of interstitial assemblages. Not only grain size, but also sorting degree and skewness notably influence the abundance of interstitial communities. Implications Ecological studies of interstitial fauna from a broader perspective offer a more comprehensive understanding of interstitial communities and provide valuable insights into habitat preferences.