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Aim: Considered one of ecology's laws, the species‐area relationship (SAR) is among the most intensively studied ecological phenomena, yet the mechanisms through which the SAR arises and under what circumstances remain poorly understood. Here, we experimentally test the effects of area alone in the absence of commonly invoked mechanistic drivers of the SAR in both sub‐tidal bay and inter‐tidal marsh habitats. Location: Louisiana, U.S.A. Taxon: Invertebrate macrofauna. Methods: To determine if surface area alone may generate the SAR, we conducted a small‐scale, ephemeral habitat island experiment in a subtidal soft‐bottom bay and in an intertidal soft‐bottom coastal salt marsh. Cellulose sponge habitat islands of varying surface areas, but with constant energy content and habitat diversity, were deployed in each location to isolate the effects of surface area on the SAR in the absence of species‐energy relationships and habitat diversity. Results: Area alone, likely through passive sampling, generated significant SARs in both habitats, with the salt marsh producing the strongest relationship, likely due to differential physical structuring between habitats. Communities of low surface area sponges were generally nested within those of high surface area sponges, and dispersal limitation may have increased the importance of nestedness relative to species replacements in structuring communities between habitats. Main Conclusions: That area alone, in the absence of covariates such as energy availability and habitat diversity may, significantly impact the species richness of experimental and ephemeral marine benthic habitat island communities. Our methodology may provide a new avenue for SAR research, allowing for the isolation and simultaneous testing of potential drivers through the physical manipulation of ephemeral habitats. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Climate change is shifting community structure and biodiversity on a global scale, in part due to alterations of chemical and thermal energy availability. These changes may impact ecosystem functioning through their influence on functional diversity. We investigate patterns of functional diversity, functional niches, and functional traits in bivalve communities across the energetic gradient of the deep Atlantic Ocean. We use the functional traits feeding type, tiering, and motility level to define the axes of functional space and the unique combinations of these traits as functional niches. We find that increased energy affords new species, added into functional space through niche expansion rather than niche packing. Underlying this pattern are complex dynamics of gains and losses of individual functional niches, with few adapted to the low- and high-energy extremes, and most occurring at intermediate energy. Adaptive qualities of specific traits are evidenced by those functional niches occurring at energetic extremes. Tradeoffs between these traits within the intermediate energy zone underlie an increased coexistence of functional niches, which in turn drives a unimodal pattern of functional niches and expansion of used functional space. This work suggests that energy-limited communities may be especially vulnerable to continued shifts in food availability through the Anthropocene.