Data from: evaluating the use of lake sedimentary DNA in palaeolimnology: a comparison with long-term microscopy-based monitoring of the phytoplankton community

Palaeolimnological records provide valuable information about how
phytoplankton respond to long-term drivers of environmental change.
Traditional palaeolimnological tools such as microfossils and pigments are
restricted to taxa that leave sub-fossil remains, and a method that can be
applied to the wider community is required. Sedimentary DNA (sedDNA),
extracted from lake sediment cores, shows promise in palaeolimnology, but
validation against data from long-term monitoring of lake water is
necessary to enable its development as a reliable record of past
phytoplankton communities. To address this need, 18S rRNA gene amplicon
sequencing was carried out on lake sediments from a core collected from
Esthwaite Water (English Lake District) spanning ~105 years. This sedDNA
record was compared with concurrent long-term microscopy-based monitoring
of phytoplankton in the surface water. Broadly comparable trends were
observed between the datasets, with respect to the diversity and relative
abundance and occurrence of chlorophytes, dinoflagellates, ochrophytes and
bacillariophytes. Up to 20% of genera were successfully captured using
both methods, and sedDNA revealed a previously undetected community of
phytoplankton. These results suggest that sedDNA can be used as an
effective record of past phytoplankton communities, at least over
timescales of less than 100 years. However, a substantial proportion of
genera identified by microscopy were not detected using sedDNA,
highlighting the current limitations of the technique that require further
development such as reference database coverage. The taphonomic processes
which may affect its reliability, such as the extent and rate of
deposition and DNA degradation, also require further research.