Mesophotic zones have been identified as potential refuges for marine species threatened by climate change, yet their role in sustaining kelp forests remains understudied. Mesophotic kelp populations are increasingly being discovered globally, particularly in tropical and subtropical regions, but given the challenges of accessing waters deeper >40 m, their ecology remains poorly understood. We conducted an innovative field study to characterize Eisenia kelp populations across diverse mesophotic habitats in the Galapagos, examining on how seasonal oceanographic variation and depth shape their ecology and persistence. Mounting a stereo-video camera system and robotic claw on remotely operated vehicles we video surveyed and sampled three kelp forests in the archipelago during the region’s cold and warm season. Their oceanographic environment was monitored via water nutrient analyses and CTD casts with a PAR sensor. Preliminary analysis revealed that kelp populations across the archipelago exhibit significantly different persistence patterns, strongly influenced by local oceanographic conditions and depth. Populations in the western region at 20–40 m were dominated by young, small thalli, while those in the central region at 50–70 m, despite extremely low light levels, consisted of longer-lived individuals, significantly larger thalli, and a complete range of age groups. These differences were linked to higher seasonal fluctuations in temperature and nutrients at shallower western sites, while deeper eastern sites experienced more stable conditions below a persistent thermocline. Our study provides evidence that deep mesophotic habitats offer stable environments conducive to the growth and survival of foundational species like kelps, highlighting their potential as critical climate refuges.

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