The objective of this study was to disentangle the effects of components of diversity and primary productivity within subarctic intertidal macroalgal communities. This study was done using common abundant macroalgal species occurring naturally together in the mid-low intertidal zone (48°37'42.5'' N, 68°11'55.7'' W) of the St. Lawrence Estuary, near the municipality of Sainte-Flavie (Quebec, Canada). We used two canopy species (genus Fucus sp.) and four of their associated subcanopy species to build realistic assemblages having four different levels of richness, two levels of evenness, and five levels of abundance. The productivity variables of respiration (R), net (NPP), and gross primary production (GPP) of these assemblages were measured in mesocosms (0.09 m²) during summer 2012 and 2013.

The data includes measurements from mesocoms. Three variables are shown: Net primary production, respiration and gross primary production. All units are mmol CO₂ m⁻² h⁻¹ per gram wet weight of macroalgae. Several columns indicate the type of assemblage from which the measurements were taken.