Algae & Cyanobacteria (A-Codes)

The A-Codes are the ATH Codex family cataloguing algal and cyanobacterial colonisers of the built environment — the pioneer phototrophs of biofilm succession. Green algae such as Trentepohlia (whose haematochrome carotenoid shields produce the characteristic red-orange staining) and desiccation-tolerant cyanobacteria such as Gloeocapsopsis (poikilohydric extremophiles able to survive total drying) establish on damp, shaded or nutrient-loaded surfaces, forming the first living layer that conditions a substrate for lichens, mosses and fungi. Within the COSMOS engine each organism is indexed by substrate affinity and by the time-of-wetness window that triggers establishment. On glazing, render and masonry they present as green or black filming, or red blooms on porous render. Because pioneer algae bind electrostatically rather than chemically dissolving the surface, they are cleared with ionic-displacement pure-water washing and a biostatic finish that interrupts re-establishment.