FIG. 5.

CLSM micrographs of cryosections showing the structural development of the biofilm xz plane in slow flows (a to d) and fast flows (e to i). (a) Coalescing microcolonies of a 4-day-old largely bacterial biofilm; (b) a relatively compact biofilm (12 days) with finger-like protuberances and the first appearance of algal cells; (c) mature biofilm (17 days) with elongated algal cells bridging a possibly quasihexagonal void; (d) 24-day-old biofilm with distinct structural differentiation into a base layer and a canopy; (e and f) images showing initial microcolonies with filamentous bacterial cells in initial biofilms (at 3 and 6 days, respectively); (g and h) images showing the structural differentiation into a base layer and a diatom-rich canopy (g) and clear microstratification with a ConA-EPS-rich layer (h); (i) cross-section of ridge-like structure with void, possibly resulting from metazoan burrowing. Note the arcade-like void system within the base layer of mature biofilms (c and h).