Rhodolith/Maërl Bed Coexisting with a Macrocystis pyrifera Kelp Forest in the Beagle Channel (Onashaga, Argentina)

Rhodolith/maërl beds are biogenic habitats formed by free-living coralline algae, recognized for their ecological importance and global distribution. Along the Argentine coastline, the published literature lacks visual field documentation of rhodolith/maërl beds, despite historical reports of rhodolith-forming species. Here, we present visual records of a rhodolith/maërl bed in the Argentine Beagle Channel, associated with an extensive Macrocystis pyrifera kelp forest (~150 m from shore). Two perpendicular swimming transects allowed confirmation of a minimum spatial extent exceeding 40 × 40 m (>1600 m2). Underwater imagery reveals continuous rhodolith cover over unconsolidated sediments, highlighting a knowledge gap in the regional distribution of these habitats in southern South America.