Microbes in caves: agents of calcite corrosion and precipitation - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 11

Fig. 3. SEM photomicrographs showing etch features on substrates in twilight zone of caves. Figure 3a, b, c, g fromOld
Man Village Cave, Grand Cayman; Figure 3d from Bats Cave, Cayman Brac; Figure 3e, f, h, i from Hospital Cave,
Cayman Brac. (a) Spikey calcite partly covered by mat formed of spores and filaments. (b, c) Spiky calcite beneath
biofilm formed of mucus and rod-shaped microbes. (d) Irregularly etched surface covered by rod-shaped microbes.
(e, f ) Blocky calcite partly covered by microbial mat. (g) Biofilm on partly etched calcite crystal. (h, i) Residue
micrite formed by microbial breakdown of calcitic substrate.

flowing over such substrates may transport these
grains elsewhere.

of calcite crystals involved in such calcification
is variable. Geitleria calcarea, a cyanobacterium
that thrives under low light conditions (Friedmann
1979; Davis & Rands 1981; Abdelahad &
Bazzichellia 1988) has been found in the twilight
zone of caves in Israel, Romania, Yugoslavia,
Florida, Cook Islands (Friedmann 1979), France
(Bourrelly & Dupuy 1973; Cout´ 1982; Leclerq
et al. 1983), Spain (Gracia Alonso 1974), Italy
(Abdelahad & Bazzichellia 1988), the Bahamas
(Davis & Rands 1981), and the Cayman Islands
(Jones & Kahle 1986, 1993). Davis and Rands
(1982) also reported Hapalosiphon intricatus with
calcified sheaths from the humid, poorly illuminated
parts of Orange Lake cave in Florida.
Calcified Geitleria found on the walls of cavities
in a breccia that fills a sinkhole on the southeast
coast of Grand Cayman are encrusted with
complex three-dimensional calcite dendrite crystals

Microbial construction of calcitic
substrates

Constructive processes include microbe calcifica-
tion, trapping and binding by filamentous microbes,
and/or mineral precipitation (Ca˜averas et al. 2001;
Jones 2001).

Microbe calcification

When microbes are replaced and/or encrusted by
calcite, they become part of the substrate (e.g.
Jones &Motyka 1987; Ari˜o et al. 1997; Gradzinski
1999; Ca˜averas et al. 2001; Gradzinski 2001;
Baskar et al. 2007; Baskar et al. 2009). The type