Towards understanding the abundance of non-pollen palynomorphs: A comparison of fossil algae, algal pigments and sedaDNA from temperate lake sediments

Given the increased interest in non-pollen palynomorphs (microscopic objects other than pollen identified from pollen slides) in palaeoecological studies, it is necessary to seek a deeper understanding of the reliability of these results. We combined quantitative information of algal pigments and sedimentary ancient DNA (sedaDNA) of phylotaxonomical resolution to validate the richness and abundance of fossil algae in the sediment of a small temperate lake. For the first time, fossil and sedaDNA algae data were combined in a composite data-set and used to reconstruct algae turnover rates over the last 14,500 years. This comparison serves as both an example of how fossil algae can be used to answer various research questions and as a method of revealing to what extent we can rely on palaeoecological interpretations based solely on the fossil algae record from pollen slides.