Sterols zooplanktonic

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). 

Compound-specific A C values for 31 different lipid biomarker molecules are shown in Figure 8 for sedimentary horizons corresponding to pre-bomb (before ad 1950) and post-bomb (1950-1996) eras. These organic compounds represent phytoplank-tonic, zooplanktonic, bacterial, archaeal, terrestrial higher plant, and fossil carbon sources. The lipid classes include long-chain n-alkanes, alkanoic (fatty) acids, -alcohols, C30 mid-chain ketols and diols, sterols, hopanols, and C40 isoprenoid side chains of the ether-linked glycerols of the Archaea. 

Walters JM, Cain RB, Higgins IJ, Corner EDS (1979b) Cell-free benzo[a]pyrene hydroxylase activity in marine zooplankton. J Mar Biol Assoc UK 59 553-563 Walton MJ, Pennock JF (1972) Some studies on the biosynthesis of ubiquinone, isoprenoid alcohols, squalene and sterols by marine invertebrates. Biochem J 127 471-479... 

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