FIGURE 2. Photosynthetic microbial mat communities on microbialites.

From the following article:

Modern freshwater microbialite analogues for ancient dendritic reef structures

Bernard Laval, Sherry L. Cady, John C. Pollack, Christopher P. McKay, John S. Bird, John P. Grotzinger, Derek C. Ford and Harry R. Bohm

Nature 407, 626-629(5 October 2000)



a, Surface of shallow–intermediate facies mound contains rounded tufts of larger, purple-pigmented filamentous cyanobacteria (Oscillatoria sp. and Calothrix sp.; shown in b) that are surrounded by green-pigmented mat of filamentous cyanobacteria (Pseudoanabaena sp. and Fischerella sp.; shown in c). b, Scanning electron microscopy (SEM) photomicrograph of uncalcified aggregates of purple-pigmented bacteria on microbialite surface. SEM specimens were fixed, dehydrated, critical point dried and Ir coated. c, Loose networks of filamentous green-pigmented cyanobacteria often bind trapped sediment. d, Calcification of the cyanobacteria filaments and their extracellular matrix at the surfaces of the microbialites perpetuates microbialite growth by providing a lithified substrate for the development of subsequent microbial mats.