Temperature sensitivity of marine macroalgae for aquaculture in China

Macroalgae aquaculture faces grand challenges from extreme temperature events in the context of global warming. For mapping aquaculture areas and assessing potential risks, it is urgent to evaluate the thermal sensitivity of commercially and ecologically important macroalgae. In the present study, thermal tolerance of commercial macroalgae species in China and sea surface temperature (SST) under current conditions and three Shared Socioeconomic Pathways (SSP1-2.6, SSP3-7.0, SSP5-8.5) scenarios in 2050 were collected for calcu-lating thermal safety margin (TSM), an index of thermal sensitivity, for each species in the aquaculture area. Our results indicated that a few species were particularly sensitive to current conditions, and the kelp Saccharina japonica and Ulva pertusa were the most sensitive species to heat and cold stress, respectively. As indicated by the regional thermal sensitivity (RTS) (i.e., the mean of TSMs for all species in each grid cell), the commercial macroalgae located in southern China (20-25 degrees N) were more sensitive to heat stress, while the commercial macroalgae located in the regions of 27-40 degrees N was more sensitive to cold stress. Commercial macroalgae nearby the Yangtze River Estuary (similar to 30 degrees N) were sensitive to both heat and cold stress. Under the three SSP scenarios, macroalgae aquaculture would be more sensitive to heat stress, and the impacts from cold stress would relatively weaken in 2050. Our findings provide crucial information for the management of macroalgae aquaculture and for climate change mitigation and adaptation in China.