Fig. 6.

The effect of foraminiferal calcite on the emitted fluorescence signal after subsequent excitations. (A) Example of a specimen incubated in HPTS dissolved in seawater and photographed 1: with transmitted light, 2: at the first excitation optimum, and 3: at the second excitation optimum. 4: The resulting pH-image after dividing the images from (2) and (3). (B) Example of an empty test incubated with HPTS, rinsed with seawater, and photographed in the same order as done for (A). (Scale bar, 100 μm.)