Table 2.

Cyanobacterial morphotypes distinguished in the four crusts

Morphotype (main characteristics)Assignment per Geitler (19)Abundancea in
Sandy soilShaleGypsumSilt
Ensheathed, bundle-forming filaments, nonheterocystous; trichomes 4–6 μm wide; no constrictions at cross-walls; cells quadratic, 5–7 μm long; necridia present; apical cells with calyptra M. vaginatus(Gomont)++++++++++
Ensheathed, bundle-forming filaments, nonheterocystous; trichomes 2.5–5 μm wide; cells 2.5–4 μm wide; slightly constricted at cross-walls; apical cells conical; sheath colorless or with scytonemin Schizothrix spp.+++++++
Single filaments, nonheterocystous; trichomes 1.2–2.5 μm wide; barrel-shaped, isodiametric cells; round apical cells Phormidium spp.++++
Heterocystous filamentous; lamellated, brown sheath; filaments 10–15 μm wide; trichomes 8–11 μm wide; cells disc-shaped, 3–5 μm wide; terminal and intercalary heterocysts Scytonemasp.+++++++
Heterocystous filamentous; short chains of spherical cells, 3.5–5 μm in diam; confluent gel holds trichome masses in spherical dark-brown colonies 90–500 μm in diam Nostoc sp.++++++
Heterocystous, disorderly masses of cells forming spherical colonies with tight, clored sheaths; upon cultivation, filaments with true branching formed; cells 3.5–7 μm wide Chlorogloeopsissp.+
  • a ++++, dominant; +++, very common; ++, common; +, present; −, not detected.