Organic matter bioturbation

Aller RC. 1994. Bioturbation and remineralization of sedimentary organic-matter-effects of redox oscillation. Chemical Geology 114 331-345. 

H -Cation Exchange. This section summarizes the results of laboratory analyses performed on LRL sediments to measure the total, organically bound, and exchangeable concentrations of base cations contained therein. We discuss mineral weathering and decomposition of organic matter with respect to the production of cations and estimate the possible contribution of H+ -cation exchange to water-column chemistry and the generation of alkalinity (IAG). Other sediment processes that may influence interpretation of data, such as bioturbation, are also discussed. 

Fauna also influence soil carbon cycling. Bioturbation mixes and aerates soil, physically breaks down litter, creates flow paths for water in soil, and can reduce surface litter stocks and enhance erosion (Bohlen et al., 2004). For example, along a gradient of European earthworm (Lumbricus terrestris) colonization in a deciduous forest of northern Michigan, earthworms are associated with a decrease in litter-layer thickness, apparently mixing some forest floor organic matter into the mineral soil. Thus, fauna can create spatial patterns in SOM stocks. 

Early diagenesis is typically described as a steady-state phenomenon however, unless very long-term geological timescales are considered, steady-state conditions are generally not common in shallow turbid environments such as estuaries. There are many factors that contribute to these non-steady-state conditions, such as variations in sedimentation rate, inputs of organic matter, chemistry of bottom waters and sediments, bioturbation rates, and resuspension (Lasagna and Holland, 1976). Consequently, numerous attempts... 

Sulfate reduction occurs mainly in sediments, with rates controlled by the quality and quantity of organic matter, S042- availability, bioturbation, abundance of dissolved O2 in overlying waters, rates of sulfide reoxidation, and availability of iron-sulfide minerals. 

Signatures of bulk C profiles in sediments are also commonly used to make inferences about the efficiency of organic matter remineralization in sediments. For example, in sediments that are highly bioturbated (physically reworked) with high O2 exposure, such as... 

Hartmann S observed that the worm traces are depleted in Mn, Ni, Cu, and Zn in comparison to the surrounding sediment. His opinion is that the decomposition of organic matter cannot lower the redox potential so far that dissolution of manganese takes place, except in locally limits) patches where organic matter is higher because of bioturbation. 

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