Figure 1: Optical properties of picocyanobacteria, marine and heterotrophic bacteria DOM.

Ultraviolet–Vis absorption and EEM fluorescence spectra of (a,b) Synechococcus-derived SPE-DOM, (c,d) Prochlorococcus-derived SPE-DOM, (e,f) SPE-DOM collected from the Sargasso Sea (BATS at 4,530 m depth) in August 2013 and (g,h) heterotrophic bacterium R. pomeroyi-derived SPE-DOM. Note: cell density was different in each culture and preclude a direct comparison of fluorescence intensity, and hence the given ultraviolet–Vis and EEM data are only intended to compare peak shapes and not intensities.