Exploring preserved fossil dinoflagellate and haptophyte DNA signatures to infer ecological and environmental changes during deposition of sapropel S1 in the eastern Mediterranean

Abstract

[1] In this study we used a comparative multiproxy survey (fossil DNA, calcareous nannofossils, and lipid biomarkers) to test whether preserved genetic signatures provide an accurate view of haptophyte and dinoflagellate populations during deposition of the eastern Mediterranean sapropel S1 and the organic carbon-depleted oxidized marls flanking the S1 and to see if we could identify important environmental indicator species that did not fossilize and escaped previous microscopic identification. The marls above and below the S1 contained low concentrations of lipid biomarkers diagnostic for dinoflagellates and haptophytes (i.e., dinosterol and long-chain alkenones), but 500 base pair long ribosomal DNA fragments of these protists were below the detection limit. In contrast, dinoflagellate and haptophyte DNA could be recovered from the organic carbon-rich S1, but the most abundant sequences did not represent species that were part of the nannofossil (this study) or previously described dinocyst composition. The oldest section of S1 (9.8 to ∼814 C kyr B.P.) revealed a predominance of dinoflagellate phylotypes, which were previously only detected in anoxic Black Sea sediments. In the same section of the core, the most abundant haptophyte sequence showed highest similarity with uncultivated haptophytes that were previously shown to grow mixotrophically as predators of picocyanobacteria, an adaptation that promotes growth in oligotrophic marine waters. Sequences with highest similarities to clones found in marine surface waters predominated in the S1 after ∼8 14 C kyr B.P. We discuss whether the shifts in haptophyte and dinoflagellate populations inferred from the preserved DNA reflect known environmental changes that occurred during the formation of sapropel S1.

Comparative Molecular Microbial Ecology of the Spring Haptophyte Bloom in a Greenland Arctic Oligosaline Lake

“…Given that Lake BrayaSø has the highest sedimentary concentrations of alkenones ever reported (D’Andrea and Huang, 2005), the high cellular concentrations as estimated by our qPCR analysis is not surprising. Our results also agree with observations by Boere et al (2011) that alkenone concentrations can serve as a proxy for haptophyte cell numbers.…”

The windblown: possible explanations for dinophyte DNA in forest soils

“…Deposited in sediments, coccoid cells have the potential to preserve the local biodiversity like diaspores in a seed bank (Dale 1983). They can be considered either as old remnants from former aquatic and today terrestrial habitats (Boere et al 2011;Sønstebø et al 2010) or the result of random dispersal (Foissner 2006(Foissner , 2011 and subsequent loss in terrestrial habitats. However, the difference between the taxonomic assignments of the rainforest soil samples (see above) may indicate that the ability to form coccoid cells during life-history is not decisive for their terrestrial occurrence.…”

Paleoclimate and paleoceanography over the past 20,000 yr in the Mediterranean Sea Basins as indicated by sediment elemental proxies

“…A peak in the Mn/Al ratio marks the boundary between the top of the TOCrich sediment and the top of Ba-enriched layer (e.g., Thomson et al, 1995Thomson et al, , 1997. The paleoenvironmental conditions during S1 deposition are indicated by the other proxy element ratios described above, as discussed below (e.g., Sangiorgi et al, 2002;Schmiedl et al, 2010;Boere et al, 2011). Decreasing values of Zr/ Al, Si/Al and Ti/Al ratios indicate reduced aeolian input, while increasing K/Al and Mg/Al ratios provide evidence for increased fluvial-derived terrigenous material (e.g., Wehausen and Brumsack, 1999).…”