Fig. 1

CYPRO uptake and settlement process. (A) Conceptual model of settlement with the pigment CYPRO. (A-I) swimming coral larvae accumulate the red pigment CYPRO from the bottom of the well in darkness; (A-II) swimming larvae appear red due to the time-dependent accumulation of CYPRO within their ectodermal layer during the dark period, under light exposure the pigment CYPRO steadily degrades, the strong red color fades over time and with that releases a constant, µM level of H₂O₂ ⁵⁰. Ultimately, the larvae attach to the bottom of the well and proceeds with their metamorphosis into a sessile recruit; (A-III) in the following altering 12 h dark and 12 light phases the pigment CYPRO fades completely, and the larvae further develop into a sessile coral recruits. (B) During the initial dark phase of the experiments (first 12 h) the swimming coral larvae of all tested species visibly changed their color and appeared red (cf. CYPRO row). For comparison the pictures at the Control row show the normal coloration of the larvae (without CYPRO).