Figure 3

Dynamics of daytime coral skeletal extension of Acropora eurystoma recorded under different light treatments: ambient photoperiod (a–c), 12hLight/12hDark ("L" stands for light, 7:00 am to 7:00 pm; "D" stands for darkness, 7:00 pm to 7:00 am), constant light (d–f) (L/L) and constant darkness (g–i) (D/D). Horizontal plot above each set of images shows ⁸⁶Sr labeling pulses (yellow boxes: 7:00 am to 7:00 pm), 36 h intervals of growth in unlabeled seawater with normal isotopic abundance and duration of 12Light/12hDark photoperiod, constant light and constant darkness conditions. During the ambient normal photoperiod (a–c) and constant light (d–f) regimes, all 5 labels (L1–L5) are visible. During constant darkness treatments (3 last labelling events) only 3 labeling events are detectable. There is clear distinction between continuous labeling in fast skeleton extension region, which consists mostly of rapid accretion deposits and disrupted, "crescent" labeling in thickening deposits (shingles) region. NanoSIMS ⁸⁶Sr/⁴⁴Ca isotope mosaic maps. (a,d,g), SEM images of polished and etched samples. (b,e,h) and NanoSIMS and SEM images overlaid (c,f,i). Yellow dashed arrows (a,d,g) mark fast growing regions where Rapid Accretion Deposits (RAD’s) are mostly located. Red rectangles (f) mark regions where RAD are particularly clearly labeled.