Jose Miguel Sandoval-Gil1, Lydia B. Ladah2, Jose Antonio Zertuche-González1, Laura K. Rangel-Mendoza1, Jose Manuel Guzmán-Calderón1, Alejandra Ferreira-Arrieta1, Víctor F. Camacho-Ibar1
1Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas, Ensenada 22860, Baja California, México
2 Department of Biological Oceanography, CICESE, Ensenada, Baja California, Mexico
Understanding the biological plasticity of kelps at their distributional boundaries is critical for predicting their responses to climate change responses. Shallow-water thermal stress can result in widespread mortality, especially at lower latitudes where the incidence of thermal anomalies can be extreme. The in situ management strategy of transplanting sporophytes to deeper waters when substrate is not naturally colonized can protect against shallow thermal stress by taking advantage of deeper cooler refugia, allowing for population survival and recolonization when optimum conditions return. However, artificial deep refugia also provides challenges, such as light limitation for photosynthesis. This study tested an artificial deep refugia for Eisenia (=Ecklonia) arborea, near its southern latitudinal limit (Baja California Sur, Mexico). Eisenia arborea is the stipitate kelp distributed furthest south in the northeast Pacific where populations are often exposed to higher temperatures than the rest of the range. Intertidal E. arborea sporophytes were transplanted below the thermocline to 7 and 15 m depth (50% to 90% of surface irradiance), and their short-term physiological responses were examined (photobiology, oxidative stress, nutrient content and nitrate uptake kinetics). Eisenia arborea exhibited photoacclimatory adjustments to reduced light availability, with increased photosynthetic efficiency and reduced non-photochemical quenching. Nitrate uptake rates decreased with depth, yet were maintained at lower nitrate availability (< 2 µM) sustaining optimum tissue nitrogen content. No sign of oxidative damage was detected. Our results suggest potential for the use of artificial deep refugia in the framework of kelps conservation and restoration strategies under climate change.