Author(s): Stuart G Wakeham
Organic matter that is deposited in aquatic sediments is subject to an intense diagenetic reactor that determines how much organic carbon is eventually preserved in sediments. The balance between organic matter degradation and preservation has immense consequences for the global carbon and oxygen cycles. A diverse set of hypotheses regarding the controls on organic matter degradation/preservation have received considerable attention over the past decade, most often revolving around the relative roles of bottom water and pore water oxygen and the rate of organic matter delivery to the sediments. These overriding hypotheses have in turn spawned numerous other hypotheses on specific topics. In this review, we discuss four important controls that impact on the degradation and subsequent preservation of organic matter in aquatic sediments. Our focus areas are: (1) the chemical nature of the organic substrate; (2) the potential influence of matrix on preservation; (3) the role of redox effects in degradation; and (4) the effects of physical mixing of sediments. Although we have divided our discussion under these headings, it will immediately become apparent that these subsections are at best arbitrary and that the four factors are indeed intimately related.