Spatiotemporal Variability in Subarctic Lithothamnion glaciale Rhodolith Bed Structural Complexity and Macrofaunal Diversity

Rhodoliths are non-geniculate, free-living coralline red algae that can accumulate on the seafloor and form structurally complex benthic habitats supporting diverse communities known as rhodolith beds. We combined in situ collections imagery to quantify variability, over 9 months at two sites, structural complexity biodiversity of a subarctic Lithothamnion glaciale bed. show unconsolidated framework is spatially heterogeneous, yet provides temporally stable habitat an abundant highly macrofauna encompassing 108 taxa dominated by brittle stars, chitons, bivalves, gastropods, polychaetes, sea urchins, stars. Specific components, including large bivalve shells, affect morphology resident macrofauna, with increasingly large, non-nucleated rhodoliths hosting higher macrofaunal density, biomass, diversity than shell-nucleated rhodoliths. The present study’s fine taxonomic resolution results strongly support notion beds hotspots. Their spatial temporal domains provide clear quantitative evidence under main influence biological forcing until sporadic unusually intense physical reworks it. Our findings suggest shallow (<20 m depth) vulnerable ongoing predicted increases frequency severity wave storms.