Impact of Temperature on the Rate of Bull Kelp (Nereocystis luetkeana) Decomposition

Abstract

In the face of global climate change, macroalgal cultivation has emerged as a potential carbon dioxide removal (CDR) strategy. However, many key knowledge gaps exist about the true extent of macroalgal carbon sequestration, including the impacts of climate change. To assess whether elevated temperatures cause Nereocystis luetkeana blades to decay more rapidly, twelve 35 mm-diameter tissue disks were allowed to decay at 10-12 °C (ambient temperature treatment) and another 12 tissue disks were allowed to decay at 17-19 °C (elevated temperature treatment). After 7 days, the mean change in disk mass for the ambient temperature treatment was compared to the mean change in mass for the elevated temperature treatment. Samples at elevated temperatures were visibly flimsier and more diaphanous, which was correlated with a significantly greater decrease in mass. This finding suggests that brown algae decay more rapidly at elevated temperatures, which has important implications for how to maximize future macroalgal carbon sequestration as ocean temperatures rise.