Figure 2

Masks exhibited in the North Acropolis, Tikal, Guatemala. (A) West Mask (WM) heavily colonized by phototrophic biofilms. (B) East Mask (EM) devoid of phototrophic biofilms and appearing dry and in sound condition. Note that WM (A) is covered by two main types (phenomenologies) of biofilms: dry/dark (lower arrow) and mucilaginous black (upper arrow).