BIODEGRADATION DE LA TRAME ORGANIQUE DES COQUILLES DE MOLLUSQUES EN MILIEU MARIN: ACTION DES MICROORGANISMES ENDOLITHES (1)
Laboratoire de Morphologie, Systématique et Écologie animales, Université de Liège, 22, Quai Van Beneden, B-4020 Liège (Belgique)
Laboratoire de Morphologie, Systématique et Écologie animales, Université de Liège, 22, Quai Van Beneden, B-4020 Liège (Belgique)
Abstract
The organic matric of dead Mollusk shells do not accumulate on a large scale in marine sediments from 0 to 5000 meter deep (at least in "normal" sedimentary conditions). All organic components of extracrystalline sheaths are quickly weathered, at first, presumably by extracellularly secreted hydrolytic enzymes of microorganisms living in the upper layers of sediments, then by microborers and chasmolithic organisms living in close contact with those org-ilnic sheaths. We verified that these organisms are able to secrete the enzymes needed to hydrolyse the organic complexes screened within calcified crystallites of Mollusk shells, and that the enzymes (chitinase and preteolytic enzymes) are actually secreted within weathering shells.
So we can conclude that there is little probability that shelly sands and gravels constitute huge "biogenic polymers" traps. AIl these polymers are generally hydrolysed during the first diagenetic events and thus are used as energy source by many detritus ·feeders, limivorous organisms and indirectly by suspension feeders living at sediment-water interface.