Particle bioturbation

The ratio of l> j /hbio represents an effective mass transfer coefficient, Thoms [5] report 38 measiuements in freshwater systems for which this ratio can be calculated. The average value is 130 cm/year and about 60% of the measurements exceed 1 cm/year and 90% exceed 0.1 cm/year. In shallow waters such as would be observed nearshore, Boudreau [7] provided correlations between biotiubation and depth that suggest a 2.54 and 29.5 cm/year effective particle mass transfer coefficient. A value of 1 cm/year appears to be a reasonably conservative estimate of the effective particle bioturbation mass transfer coefficient in a clean shallow system, such as the top of a nearshore sediment cap. A coefficient of the order of 1 cm/year or more has also been observed by Thibodeaux [8]. 

SdAV, sediment side particle bioturbation — (pgKi)D /h Db/h... 

McCall, P.L., G. Matisoff, X. Wang, and J.A. Robbins. 2010. Particle bioturbation by the marine bivalve Yoldia limatida (Say), in press. 

Green MA. Aller RC, Cochran JK, Lee C, Aller JY (2002). Bioturbation in shelf/slope sediments off Cape Hatteras, North Carolina The use of " Th, Chl-a, and Br to evaluate rates of particle and solute transport. Deep-Sea Res 1149(20) 4627-4644... 

A particularly important consequence of bioirrigation and bioturbation is the introduction of relatively 02-rich bottom water into the sediments. This enhancement in O2 supply is analogous to the aeration of soil by earthworms. Bioturbation can occur as deeply as 1 m below the sediment surface, but is most intense in the top 10 cm. The depth of O2 penetration is also strongly influenced by the flux of sedimenting POM. High accumulation rates of organic-rich particles can fuel bacterially mediated aerobic respiration supporting rates of O2 removal that exceed the benthic animals abilities to reaerate the sediments. In this case, anoxic conditions result. Since animals require O2, bioturbation does not occur in anoxic sediments. Thus, the effects of bioturbation are limited to the oxic portion of the sediments. 

The geographic distribution of opal in the surfece sediments is controlled by (1) the local rain rate of biogenic silica, (2) the degree of its preservation in the sediments, and (3) the relative rate of accumulation of other types of particles. Preservation is promoted by rapid burial as this isolates BSi from seawater. But if the BSi is buried by other particle types, the relative contribution of BSi to the sediment is diluted. This dilution effect causes the BSi content of most continental margin sediments to be low despite high rain rates. Preservation efficiency is also dependent on (1) the intensity of bioturbation and suspension feeding and (2) the various factors that control... 

Aller, R.C., Aller, J.Y., and Kemp, P.F. (2001) Effects of particle and solute transport on rates and extent of remineralization in bioturbated sediments. In Organism-Sediment Interactions (Aller, J.Y., Woodin, S.A., and Aller, R.C., eds.), pp. 315-334, University of South Carolina Press, Columbia, SC. 

Kure, L.K., and Forbes, T.L. (1997) Impact of bioturbation by Arenicola marina on the fate of particle-bound fluoranthene. Mar. Ecol. Prog. Ser. 156, 157-166. 

Tritium profiles are commonly interpreted with the basic premise that the soil is a uniform medium, with a spongelike structure, through which water infiltrates. However, short-circuit flow through conduits such as cracks, bioturbations, or decayed root channels must also be considered. Cracks, or rodent holes, are efficient intake points of runoff, and occasionally they become filled with coarse particles, providing routes of relatively high conductivity. When a soil profile builds up, these coarsely repacked channels... 

Bioturbation and particle transport in California slope sediments a radiochemical approach. J. Mar. Res. 57, 335-355. 

Wheatcroft R. A. (1992) Experimental tests for particle size-dependent bioturbation in the deep ocean. Limnol. Oceanogr. 37, 90-104. 

These diagenetic models have proven effective in understanding the effects of various sedimentary processes on silica dynamics in the seabed (Johnson, 1976 Ragueneau et al., 2000). For example, the effect of bioturbation by benthic fauna on pore-water silicate profiles has been examined (Schinck and Guinasso, 1978). Higher intensities of bioturbation lead to higher asymptotic silicate values at depth because the benthic fauna are mixing down particles from the surface... 

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