Possible cause of sand clumping in our tanks, found in research.

[HighlandReefer]

Experimental observations on fungal diagenesis of carbonate
substrates
Kamal Kolo,1 Eddy Keppens,1 Alain Pre´at,2 and Philippe Claeys1
Received 22 March 2006; revised 10 September 2006; accepted 17 October 2006; published 27 January 2007
http://prog4.vub.ac.be/~dglg/Web/Claeys/Pubs/Kolo-etal-2007.pdf

From this article:

"Conclusions
[75] The role of fungi may be of great significance in the
diagenesis of carbonate rocks. In the present study, the
fungal interaction with carbonate substrates (thin sections
and rock chips) triggered specific diagenetic processes that
produced significant diagenesis of substrates’ petrography
and chemistry, in many aspects comparable to sedimentary
diagenesis. The diagenetic processes included substrate
dissolution, neo-mineral formation, biomineralization,
micritization, demicritization, grain-to-grain bridging,
cementation, replacement, open-space filling, porosity permeability
enhancement grain size alteration, concentric
zonation structures, isotopic fractionation, neo-substrate formation
and biostratification. These processes, driven by the
biochemical (organic acids) and biomechanical (growth
pressure) potency of fungi, introduced new textures and
structures, i.e., alveolar-honeycomb, mouldic-replacement
porosity, intergranular and intragranular porosity, whole
crystal replacement, and zonal-concentric structures. Original
carbonate cement was removed through a demicritization
process. A new type of micrite-size cement, named
here ‘‘biomineral cement’’, was formed between the grains
in the form of bridging-meniscus cement and as biomineralized
fungal hyphae. This new cement also lined
pores in similar mode to spar cement. Dolomite or calcite
crystals from the substrates were micritized by dissolution-
biomineral precipitation on their surfaces. Fungal
interaction produced ‘‘biological stratification’’ when
new substrates, totally composed of micrite-size biominerals
(mainly Ca- Mg- oxalates), were precipitated on the
original calcitic or dolomitic substrates.
[76] Fungal interaction significantly altered the isotopic
and mineralogical composition of the substrates. The isotopic
signature of the newly formed biominerals is considerably
different from the signature of the substrates,
suggesting a significant isotope fractionation. Compared
to the original unattacked surfaces, the d13C of the newly
formed minerals and attacked substrates show considerable
depletion while the d18O values show enrichment.
[77] Mineralogically, Ca and Mg were recycled from calcite
and dolomite into the newly formed biominerals:
weddellite, whewellite, glushinskite, protodolomite and
possibly struvite, where they filled voids, selectively precipitated
on grain boundaries, biomineralized fungal
hyphae, and also formed new substrates. This recycling
was selective and reflected the chemistry of the substrate.
Mg-biominerals (oxalates, protodolomite and possible
struvite) were only formed on dolomitic substrates, while
Ca-biominerals were formed on both calcitic and dolomitic
ones. Of particular significance was the formation of
‘protodolomite’ during fungal interaction with the dolomitic
substrate. The formation of this ‘‘protodolomite’’
may signal an unprecedented case of a sedimentary dolomite
being recycled within a fungal-carbonate substrate
environment.
[78] In the present study, the role of fungi in the diagenesis
of carbonate rocks significantly exceeded that of
simple surface bioweathering, the results approaching those
of sedimentary diagenesis, where petrography, mineralogy
and chemistry are changed. This role shows fungi to be
important players in the redistribution of metals, especially
Ca, Mg and C and reshaping rock surfaces."

[HighlandReefer]

The article referred to above, discusses fungal biomineralization on land. This article discusses the occurrence of fungal biomineralization in sea water:

In vitro formation of Ca-oxalates and the mineral glushinskite by fungal interaction with carbonate substrates and seawater (04/2005)
http://adsabs.harvard.edu/abs/2005BGD.....2..451K

From it:

"This study investigates the in vitro formation of Ca-oxalates and glushinskite through fungal interaction with carbonate substrates and seawater. In the first experiment, thin-sections prepared from dolomitic rock samples of Terwagne Formation (Carboniferous, Viséan, northern France) served as substrates. The thin sections placed in Petri dishes were exposed to fungi grown from naturally existing airborne spores. In the second experiment, fungal growth and mineral formation was monitored using only standard seawater (SSW) as substrate. Fungal growth media consisted of a high protein/carbohydrates and sugar diet with demineralised water for irrigation. Fungal growth process reached completion under uncontrolled laboratory conditions. The fungal interaction and attack on the carbonate substrates resulted in the formation of Ca-oxalates (weddellite CaC2O4·2(H2O), whewellite (CaC2O4·(H2O)) and glushinskite MgC2O4·2(H2O) associated with the destruction of the original substrate and its replacement by the new minerals. The seawater substrate resulted also in the formation of glushinskite and Ca-oxalates. Both of Ca and Mg were mobilized from the experimental substrates by fungi. The newly formed minerals and textural changes caused by fungal attack on the carbonate substrate were investigated using light and scanning electron microscopy (SEM-EDX), x-ray diffraction (XRD) and Raman spectroscopy. The results document the role of microorganisms in biomineralization, neo-mineral formation and sediment diagenesis. They also reveal the capacity of living fungi to interact with liquid substrates and precipitate new minerals. This work is the first report on the in vitro formation of the mineral glushinskite through fungal-carbonate and sea water substrates interactions processes."

[bertoni]

That's interesting, although I think this paper doesn't cover marine areas. I wonder whether we could be seeing similar effects, but from bacteria.

[HighlandReefer]

The second article does. I had just noticed the first research article only took place in land environments and looked further for marine environments and found the second article. :lol:

The bacteria can produce calcium carbonate organically, but I have not found that they produce the mineralization of different types of cements and glues that fungi do. Perhaps they do, but I can't find it in my searches so far. I would assume that the biomineralization produced by fungi is much stronger than that produced by bacteria, but further research found may disclose more about this. :)

This is one article I found:

Bacterial Induced Lithification of Microbial Mats
http://www.jstor.org/pss/3514973

[HighlandReefer]

Another aspect that may come into play, is that fungi grow their mycelium (primitive root type structures), deep into spaces that bacteria may not be able to grow or reach, which could lead to more biomineralization taking place deeper into the substrates and perhaps stronger bonding of the substrate (sand clumping in the case of our tanks).

[Genetics]

It wouldn't be surprising if both fungi and bacteria have there role in lithification.