IntroductionSeaweed aquaculture production is expanding globally but threatened by increasing climate stressors, including extreme events. Ocean-based aquaculture is especially vulnerable to marine heatwaves, which can rapidly raise temperatures above the physiological limits of organisms, including macroalgae. While several interventions to increase aquaculture’s resilience to climate impacts are being explored across different scales, ‘priming’-exposing an earlier stage of an organism to a mild stressor to prepare the individual for future stress-has emerged as a possible species adaptation for seaweeds that maintains genetic diversity but hardens individuals to stressors later in life. California has a developing seaweed sector while also experiencing some of the most extreme marine heatwave conditions on record.MethodsUsing laboratory thermal experiments, we explored temperature impacts and potential priming effects on giant kelp, Macrocystis pyrifera, an important foundation species along the West Coast of the United States. Our trials focused on the juvenile sporophyte stage grown on miniaturized aquaculture spools. First, we determined the baseline reaction norms of the local M. pyrifera (5 to 30 °C) at the outplanting stage. Next, we tested if priming (with heat and/or nutrients) in a hatchery setting prepares M. pyrifera for outplanting to a marine heatwave. We measured growth, survival, photosynthetic function (Fv/Fm), and carbon and nitrogen assimilation via isotopes.ResultsWe found temperatures above 20 °C had significant negative impacts on all metrics of performance of unprimed juvenile sporophytes, with conditions closer to 10 °C more favorable. Further, we determined heat priming in conjunction with hatchery level (i.e., elevated) nutrients resulted in overall increased performance when exposed to a simulated marine heatwave (18 °C) at outplanting.DiscussionThese findings support the continued exploration of priming as a tool for climate resilience and can inform current hatchery practices for aquaculture practitioners looking to improve crop outcomes for this species.