Seasonal ecosystem metabolism across shallow benthic habitats measured by aquatic eddy covariance

Shallow benthic habitats are hotspots for carbon cycling and energy flow, but metabolism (primary production and respiration) dynamics and habitat-specific differences remain poorly understood. We investigated daily, seasonal, and annual metabolism in six key benthic habitats in the Baltic Sea using ~ 2900 h of in situ aquatic eddy covariance oxygen flux measurements. Rocky substrates had the highest metabolism rates. Habitat-specific annual primary production per m ² was in the order Fucus vesiculosus canopy > Mytilus trossulus reef > Zostera marina canopy > mixed macrophytes canopy > sands, whereas respiration was in the order M. trossulus > F. vesiculosus > Z. marina > mixed macrophytes > sands > aphotic sediments. Winter metabolism contributed 22–31% of annual rates. Spatial upscaling revealed that benthic habitats drive > 90% of ecosystem metabolism in waters ≤5 m depth, highlighting their central role in carbon and nutrient cycling in shallow waters.