Macrofaunal Biodiversity and Patch Mosaics on the Deep Gulf of Mexico Seafloor

Abstract

The deep-sea benthos often exhibit exceptional biodiversity. The patch-mosaic hypothesis proposes that this deep-sea diversity arises from varied microhabitats with prolonged temporal persistence filtering for distinctive communities thereby increasing beta-diversity. This study investigated environmental, community, and macrofaunal species turnover at four deep-sea sites (~2000 m) in the northern Gulf of Mexico. Using precise small-scale sampling with a ROV, we analyzed patterns across spatial scales from centimeters to approximately 400 km among 67 sediment cores. We examined the relationships between sedimentary carbon, sediment grain size, and macrofaunal alpha- and beta-diversity. Subsequently, we explored the role of these environmental properties and their spatial arrangement in shaping communities and species distributions. We observed a consistent trend where the overall abundance and diversity of a community increased with higher carbon but decreased with increasing grain size. Substantial faunal turnover was observed among cores, even at centimeter scales, with the contribution of centimeter-scale spatial distance rivaling that of 100-km scales in faunal dissimilarity. Similar to alpha-diversity, beta-diversity exhibited strong correlations with sediment carbon and grain size. The observed random spatial structure in grain size and carbon appear to translate into randomness in both community and species distribution. These findings align with the patch-mosaic model, underscoring the complexity of deep-sea ecosystems. These findings suggest an intricate relationship between sedimentary attributes, faunal composition, and spatial arrangement in the deep-sea benthos, shedding light on the mechanisms driving biodiversity in seemingly homogeneous environments.