Elk Kelp, Pelagophycus porra, distribution limited due to susceptibility of microscopic stages to high light

►Transplanted P. porra exhibited no differences in survival or growth among depths. ►P. porra's macroscopic stages photoacclimated as they grew through the water column. ►P. porra's microscopic stages were unable to photoacclimate to higher light conditions. ►Vulnerability of microscopic stages to high light inhibits P. porra from shallower water.