Chlorophyll a fluorescence measurements were performed using a Fast Repetition Rate fluorometer (FRRf) coupled to a FastAct Laboratory system (FastOcean PTX, both from Chelsea Technologies Group at the start and the end of the experiment. The excitation wavelengths of the fluorometer's LEDs were 450 nm, 530 nm and 624 nm and the light intensity was automatically adjusted between 0.66–1.2 x 1022 photons m-2 s-1. The parameters were determined after 10 min of dark acclimation.