Lacustrine diatoms are used extensively as reliable conventional proxies in Holocene (within the last 10,000 years) paleoclimate studies. According to this 2010 paper:
(paleoclimate) Reconstructions based on all these methods rely on the general assumption that the environmental requirements of the fossil
diatom taxa used as bioindicators have remained constant during the
period considered and, consequently, are similar to those of their
closest living representatives. In this way, the environmental
information obtained from living organisms can be used as modern
analogous and extrapolated to the fossil record, particularly in
As abundant as they are in living form, diatoms are generally poorly (and unreliably) preserved in an older oceanic fossil record. Importantly, they evolve rather quickly making tracking chemical changes in a single species over time and space impossible. Bulk chemistries may be obtained from fossilized silicic masses and serve as rough indicators of overall diatom abundance and thus system health.
They are, however, used in novel ways: some diatoms live exclusively in sea ice and can be used to assess duration and distribution of that sea ice, itself a record of sea surface temperature (SST):
Diatoms in Arctic regions: Potential tools to decipher environmental changes
SIDEBAR. Diatoms as Sea Ice Proxies
By contrast, forams are well preserved in the fossil record, have a well calibrated evolutionary record, and as carbonates, contain important isotopes whose ratios are sensitive to SST.