Beyond bioerosion - the last word?

marcos sience at
Fri Oct 5 12:25:20 EDT 2001

Dear colleques,

I d like to add a short calculation to the discussion: There are about 600
thousand square meter of coral rubble out there (number propably to low
since it accounts for tropical regions only). Every single piece of coral
rubble, from the supratidal down to 30m (and further) is bored by
microendolithic algae (see Gektidis 1999 for an example of a pacific
location). The removal of calciumcarbonate equals approx. 600g per
squaremeter per year (see Vogel et al. 2000 or Chazottes et al. 1995).

That makes it a 360 tons of carbonate per year that microborers dissolve
worldwide in coral rubble only. We will have to add microbioerosion of
living coral skeletons, consolidated carbon and carbonate sediments like
the ooid banks of the bahama platform. And these are the tropics, only. As
Mike pointed out there are the heterotrophs (boring fungi) that erode
carbonates in deep waters, high latitudes and propably 24h a day as well.

So, I would think that microbioerosion has to be included in any carbonate
budget model for reef systems worth speaking off. A CO2-calcification
model, as Bob mentions, is just one part of the equation. And even there,
microbioerosion should be considered as part of the model as well, maybe
as a conversion factor as it exists in oceanographic budgets. The reason
is simple: microbioerosion starts as soon as a carbonate surface is
exposed to the water. Biocalcification is never taking place without an
instant erosion of the freshly precipitated material. Our data show
measurable activity of microboring algae after 1 week of exposure.

Please excuse my english,

cheers, Marcos

Dr. Marcos Gektidis
Geologisch Paläontologisches Institut
Senckenberganlage 32-34
60054 Frankfurt am Main

    Bioerosion rates on coral reefs: interaction between macroborers, microborers
and grazers
    (Moorea, French Polynesia).- Palaeogeogr., Palaeoclim., Palaeoecol., 113:
189-198; Amsterdam.

GEKTIDIS, M. (1999):
    Cyanobacteria and associated microorganisms characterize coarse shoarline
carbonates of One Tree
    Island, Australia.- Marine Cyanobacteria (Charpy, L. & Larkum, A. W. D.,
editors), Bulletin de l´ Institut
    Océanographique, Monaco, special issue.

    Experimental studies on microbial bioerosion at Lee Stocking Island, Bahamas and
One Tree Island,
    Great Barrier Reef, Australia: Implications for paleoecological
reconstructions.- Lethaia, 33: 190-204,
    Oslo 2000.

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