Siliceous particles (30 to 100 µm) collected from freshwater peat deposits in the Okefenokee swamp show extensive effects of bioerosion. When viewed with the SEM these effects include: (1) depressions (similar to those produced by diatoms); (2) perforations (holes 2 µm in diameter); and (3) borings (holes > 2 µm in diameter). These features are most likely to be of biological origin because of their smooth surfaces and the consistency of the geometry of the cavities. The delicate nature of the eroded grains dictates that the biological agents responsible must have lived in the peat-forming environment. For example, monaxon sponge spicules have lost as much as half their original mass through hundreds of tubular microborings, rendering them far too fragil for transport. Heretofore, microborings have been observed to commonly occur on carbonate substrates, and in only two cases has bioerosion been reported in siliceous sediments in a marine environment. Our observations show that freshwater organisms are also capable of boring/dissolving silica, and that this form of degradation may play a major role in silicon mobility within peat-forming environments.

End_of_Article - Last_Page 543------------