Prokaryotic richness and diversity increased during Holocene glacier retreat and onset of an Antarctic Lake

Knowledge about biodiversity changes during transitions from glacial landscape to lake formation is limited to contemporary studies. Here, we combined analyses of lithology, chronology and geochemistry with sedimentary ancient DNA metabarcoding to assess such transition in maritime Antarctica. We inferred three paleoenvironmental stages covering the Holocene glacier retreat process. From 4900 to 3850 years before the present, we found the lowest prokaryotic richness/diversity, with bacterial taxa indicators associated to soil and terrestrial environments. From 3850 to 2650 years before the present, a higher carbon content, higher Carbon/Nitrogen variability, increased species richness/diversity, and prokaryotic taxa indicators of long-term energy starvation were detected. Finally, from 2650 to 1070 years before the present, we inferred the onset of a genuine lacustrine environment holding stable Carbon/Nitrogen ratios and the highest prokaryotic diversity, with known aquatic bacterial taxa. Our study unveils for the first time the evolution from a glacier-covered to a freshwater lake through a millennial scale.