Abstract

Premise: Understanding the adaptive capacities of species over long timescales lies in examining the revived recent and millennia-old resting spores buried in sediments. We show for the first time the revival, viability, and germination rate of resting spores of the diatom Chaetoceros deposited in sub-seafloor sediments from three ages (recent: 0 to 80 years; ancient: similar to 1250 (Medieval Climate Anomaly) and similar to 6600 (Holocene Thermal Maximum) calendar year before present.Methods: Recent and ancient Chaetoceros spores were revived to examine their viability and germination rate. Light and scanning electron microscopy and Sanger sequencing was done to identify the species.Results: We show that similar to 6600 cal. year BP old Chaetoceros resting spores are still viable and that the vegetative reproduction in recent and ancient resting spores varies. The time taken to germinate is three hours to 2 to 3 days in both recent and ancient spores, but the germination rate of the spores decreased with increasing age. The germination rate of the recent spores was similar to 41% while that of the ancient spores were similar to 31% and similar to 12% for the similar to 1250 and similar to 6600 cal. year BP old resting spores, respectively. Based on the morphology of the germinated vegetative cells we identified the species as Chaetoceros muelleri var. subsalsum. Sanger sequences of nuclear and chloroplast markers identified the species as Chaetoceros muelleri.Conclusions: We identify a unique model system, Chaetoceros muelleri var. subsalsum and show that recent and ancient resting spores of the species buried in sediments in the Baltic Sea can be revived and used for long-term evolutionary studies.

Keywords

Baltic Sea; Chaetoceros muelleri var; subsalsum; germination rate; resting spore concentration; resurrection ecology

Published in

American Journal of Botany
2022, volume: 109, number: 1, pages: 67-82
Publisher: WILEY

Authors' information