Antonella C. Almeida Saa1, Jose Miguel Sandoval Gil1, Jose Antonio Zertuche-González1, Ricardo Cruz-López1, Schery Umanzor2, Raquel Muñiz-Salazar3, Paula Bonet Melia1, Jessica Anayansi García Pantoja1, Laura K. Rangel Mendoza1, Leonardo Ruiz Montoya1, Jose Manuel Guzmán Calderón1, Alejandra Ferreira Arrieta1
1Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas, Ensenada 22860, Baja California, México
2College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska 99801, Unites States of America
3Universidad Autónoma de Baja California, Escuela de Ciencias de la Salud, Ensenada 22800, Baja California, México
Marine heatwaves (MHWs) associated with climate change threaten the productivity and distribution of kelps worldwide. In the Northeast Pacific, kelps find their southernmost distribution boundary in the Baja California peninsula. Here, MHWs have been associated to severe alteration of kelps populations, although specific temperature-kelp´s physiology interactions remain poor understood. Adaptation to different local thermal regimes is among the primary factors that can determine kelps’ physiological tolerance and resilience capacities under thermal stress. In this study, we assessed for the first time the physiological plasticity, stress responses, and recovery capacities of Pterygophora californica exposed to a simulated MHW and recovery conditions. Controlled experiments were conducted in outdoor mesocosm systems using adult sporophytes collected from shallow (10 m) and deep (25 m) populations, presumably adapted to different temperature regimes. Variables measured included photobiology, oxidative stress, nutrient content (nitrogen, carbohydrates), nitrogen uptake kinetics and growth. Results showed different response patterns between the shallow and deep populations at the exposure and recovery phases. Photosynthesis and nitrate uptake rates were positively affected by temperature in both populations, while only shallow water sporophytes showed oxidative damage and diminished vegetative growth with increased temperature. Elevated thermal tolerance exhibited by deep sporophytes could be related to deep population refugia; this opens the window to potential uses in restoration efforts for this species.