Non-proportional preservation of algal and invertebrate remains in freshwater sediments: mitigating taphonomic bias

Investigators of the subfossil assemblages in lake sediments have repeatedly noted that their composition does not precisely correspond to the source communities. In this article we summarize published information related to the taphonomy of several model algal (diatoms, desmids, green algae), protozoan (testaceans, tintinnids) and invertebrate (sponges, bryozoans, chironomids, chaoborids, ceratopogonids, ostracods and cladocerans) groups inhabiting recent continental water bodies. We critically assess their significance as paleoecological indicators in light of the taphonomic processes acting in lacustrine sediments. Taphonomic biases can lead to misinterpretation of data obtained from the sedimentary record. The combined use of several paleoecological indicators can reduce such errors. However, such multi-proxy studies are quite labor-intensive and require the involvement of specialists in different groups of indicator organisms. We argue that taphonomic bias should be treated not only as a source of error but also as an interpretable feature of sediment records. Because organism groups differ in production, transport, deposition, and preservation, single-proxy reconstructions may confound ecological change with differential survival of remains. We therefore emphasize Smirnov's three-stage algae–zoological approach as a practical screening method: first characterizing the whole taphocenosis, then resolving zoogenic remains to major groups, and finally applying detailed taxonomic analysis to selected indicator taxa. This framework provides a low-cost way to choose appropriate proxies and interpret paleoecological signals in their taphonomic context.