SORPTIVE PRESERVATION OF LABILE ORGANIC-MATTER IN MARINE-SEDIMENTS

ORGANIC matter preserved in marine sediments provides a molecular reco rd of marine biological processes(1), accounts for approximately 20% o f all carbon burial(2) and plays a key role in balancing the long-term flux of oxygen to the atmosphere(3). Only recently has it been apprec iated that more than 90% of the organic matter preserved in most marin e sediments is intimately associated with mineral surfaces(4). Little is known, however, of the effect that sorption to mineral surfaces mig ht have in controlling either the lability or-quantity of-organic matt er in the marine sedimentary record. The preserved organic material co uld be either intrinsically stable, or stabilized through interactions with mineral matrices. We show here that sorption of organic matter t o mineral surfaces in marine sediments stabilizes the component molecu les, slowing remineralization rates by up to five orders of magnitude. Sorptive protection can therefore account for the enigmatic preservat ion of intrinsically labile molecules such as amino acids and simple s ugars in marine deposits(5,6) and links the preservation of organic ca rbon in marine sediments to the deposition of mineral surfaces.