Far‐red light acclimation in <i>Phaeophila dendroides</i> (<scp>Ulvales, Ulvophyceae</scp>) isolated from a coral skeleton

SUMMARY The light environment within a coral skeleton is rich in far‐red light (FRL) but lacks photosynthetically active radiation. Nevertheless, various algal species have been detected in these photosynthetically severe environments. We isolated the filamentous green alga Phaeophila dendroides strain Sa‐1 (Ulvales, Ulvophyceae) from a coral skeleton ( Porites sp.) off Sesoko Island, Okinawa, Japan. This is the first Phaeophila strain to have been isolated from a coral skeleton. The strain grew under far‐red light‐emitting diodes (FRL‐LED) as a sole light source, as well as under white light, demonstrating that it can acclimate to FRL. We experimentally determined that cells grown under FRL‐LED alone absorbed the light by red‐shifted chlorophyll a associating with newly induced or modified light‐harvesting antenna complexes. This ability allows P. dendroides strain Sa‐1 to inhabit environments where FRL is dominant, such as the interior of coral skeletons or the surface of seaweed.