Photoinhibition and photoacclimation of turf algal communities on a temperate reef, after in situ transplantation experiments

Abstract

The photophysiology of turf algal communities was studied in situ on a temperate reef off the coast of South Australia. Algal communities were grown on artificial substrate at depths of 2, 4, and 10 m. To investigate the response of the algal communities to changing light environments in both the short and long term, reciprocal transplantation experiments were conducted among these depths on a seasonal basis. The extent of photoinhibition was assessed every 3 h for the first 2 days following transplantation and then on a daily basis for 16 days after transplantation. Photosynthetic acclimation was assessed using photosynthesis–light curves obtained from transplanted and non-transplanted turfs after the acclimation period. Transplanted turfs responded very quickly to the light shift. Algae acclimated to low light (10 m depth) were highly susceptible to photoinhibition and photodamage, having greater decreases in maximum and effective quantum yields than turfs from shallower depths. Yield recovery and acclimation usually occurred very rapidly in algae from all depths (3–5 days), but were faster in spring and summer compared with winter. Changes in photosynthetic capacity (across seasons, depths, and after transplantation to a different depth) were accompanied by changes in respiration, so that the ratio of net to gross photosynthetic capacity (Pmnet : Pmgross) remained high and constant over the whole range of light levels. We discuss the possible acclimation strategies of turfs, taking into account the balance between photoacclimation, production, and growth strategy.