Differential impacts of alternate primary producers on carbon cycling

Abstract Disturbance impacts the spatial distribution of primary producers, which can have cascading effects on ecosystem function. The lower‐intertidal zone rocky shores Pacific Northwest is one such place where wave energy creates a mosaic‐like between two assemblages: surfgrass ( Phyllospadix scouleri ) meadows and macroalgal forests dominated by kelp. We simulated disturbance experimentally removing patches monocultures, resulting in assemblage with increased diversity, biomass, net productivity following year. Although had higher C:N compared to assemblages, assemblages achieved fixed carbon at faster rate, released more dissolved organic (DOC) during photosynthesis. Thus, despite similar standing amounts carbon, turnover—from fixation DOC release. Comparative photophysiology indicated that surfgrasses competitive advantage over other macrophytes low light levels, allowing them persist when reduced. Unexpectedly, this system potential for sequestration monocultures were replaced diverse macroalgae.