Abstract
The presence of consumer organisms in
ancient ecosystems has been indicated
mainly by the occurrence of fossilized
mineral skeletons. In comparison with
primary producers and bacteria, nonphotosynthetic
enkaryotic organisms are
minute contributors to organic carbon
preserved in sediments. In principle,
however, organic compounds produced
by heterotrophs have the potential to
enter the sedimentary record. The biomass
of respiring heterotrophs is
enriched in
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