Climate change challenges and opportunities for seaweed aquaculture in California, the United States

Seaweed aquaculture in California, the United States, is at an early stage of development. The coastal climate and growing season contrast with the cold-temperate, where most seaweed cultivation in the US occurs. Climate change is warming coastal waters on average and increasing the frequency of marine heatwaves (MHWs). In California, those changes co-occur with predicted seasonal changes in upwelling. Warm, low nutrient events cause diebacks of wild Macrocystis pyrifera, and other wild-harvested species. Aquaculture can replace wild-harvested seaweeds and expand supplies of California-grown seaweeds, if cultivation is developed with climate-change resilience. We consider wild-harvested species for traits expected to increase climate resilient productivity. Golden kombu, Laminaria farlowii, was selected for test cultivation. Early life stages were successfully grown. Sporophyte growth rates were higher in summer than winter, confirming Golden kombu as a summer crop in California. Based on projections of change in upwelling intensity and season in California, we suggest a physiological screening approach for resilience to conditions expected in different regions of coastal California by mid-to-late 21st century.