Light curves. Recorded light curves using PAM fluorometry: relative photosynthetic electron transport rates (rel. ETR) as a function of irradiance (measured as photosynthetic active radiation PAR) for sponge individuals growing in close proximity on the same transect. □ Phyllospongia sp. containing Candidatus Synechococcus spongiarum; ○ Psammastra sp. containing "Candidatus Synechococcus spongiarum"; △ Spongia sp. containing Synechocystis trididemni like symbionts; × Cymbastela marshae containing Oscillatoria sp., + Mycale sp. 2 containing a Rhodophyte and * unidentified Calcarea species containing a Synechococcus sp.