Zooplankton fecal pellets sedimentation

There are, however, some problems in the direct application of such a ratio. First, relative high abundances of A7-sterols have been reported in Lake Kinneret, a normal marine salinity environment (39). Hence, A -sterols are obviously not restricted to organisms living in hypersaline environments. The relative abundance of A7- (and a8 14)-) sterols in hypersaline environments may be due to the absence of grazing zooplankton in these environments. In normal marine salinity environments A7- and A8(14)-sterols are selectively metabolised in the guts of zooplankton resulting in a selective preservation of A5-sterols in zooplankton fecal pellets, which are transported rapidly to the sediment (40,41). 

Prahl, F.G., and Carpenter, R. (1979) The role of zooplankton fecal pellets in the sedimentation of polycyclic aromatic hydrocarbons in Dabob Bay, Washington. Geochim. Cosmochim. Acta 44, 1967-1976. 

In this chapter, mechanisms of particle removal are limited to coagulation and sedimentation. Predictions of size distributions are obtained that are in reasonable agreement with measured size distributions from oceanic waters and digested sewage sludge. Sensitivity of the predictions to fluid turbulence and fluid density presents a plausible explanation for zones of higher particle concentration observed in the oceanic water column. The analysis does not include zooplankton fecal pellet production, particle breakup, or dissolution, nor does it directly incorporate biological productivity. 

As mentioned above, most oils are buoyant in water. However, in areas with high levels of suspended sediment, petroleum constituents may be transported to the river, lake, or ocean floor through the process of sedimentation. Oil may adsorb to sediments and sink or be ingested by zooplankton and excreted in fecal pellets that may settle to the bottom. Oil stranded on shorehnes also may pick up sediments, float with the tide, and then sink. Most of this process occurs from about 2 to 7 days after the spill. 

Species of the more soluble and kineticaUy labile Fe(II) redox state are intermittently present in seawater as a result of Fe(III) reduction by a variety of processes in different ocean environments. Chemical and/or microbial reduction of Fe(III) occurs on a large scale in anoxic basins and sediments (Sections 3.1.4 and 3.3.4) and on a microscopic scale within the fecal pellets of zooplankton. In the surface ocean reduction occurs via absorption of high visible-low UV light (photo-reduction) [51,59-65], and via biologically-mediated reactions at cell surfaces [12,66-68]. 

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