Drivers of ecosystem metabolism in temperate kelp forests: A high‐resolution aquatic eddy covariance study

Abstract Kelp forests are highly productive coastal ecosystems that sustain organic carbon cycling and diverse food webs; however, their ecosystem metabolism remains insufficiently quantified due to a lack of suitable in situ methods. In this study, the aquatic eddy covariance technique was used to quantify oxygen (O 2 ) flux and net ecosystem metabolism in Ecklonia cava forests along Jeju Island, Korea. We also applied partial least squares regression to assess the relative influence of environmental conditions and canopy‐structure metrics on O 2 flux variability. During the daytime, O 2 flux variability was primarily associated with hydrodynamic conditions and light, whereas at night, the relative importance of canopy density increased, together with temperature. This interplay between drivers was reflected in metabolic shifts of E. cava forests: net ecosystem metabolism was positive under dense canopies during periods of favorable light and hydrodynamic conditions but shifted toward negative values under elevated water temperature and canopy degradation. Our results demonstrate that metabolic regulation in structurally complex kelp forests is driven by a dynamic coupling of hydrodynamic forcing and biological phenology. These findings provide a critical mechanistic basis for assessing the metabolic resilience of temperate kelp forests and evaluating their potential role as nature‐based solutions for carbon sequestration in a rapidly changing ocean.