Assessment of microfossil paleoproxy signatures
Dinoflagellate signatures preserved in sediments can serve as proxies for past trophic status, sea surface salinity (SSS), and potential sea-ice extent. However, micropaleontological studies of past dinoflagellate communities is often limited because the majority of dinoflagellates does not make cysts, or the cysts exhibit poor preservation characteristics. Similarly, lipid biomarker (“dinosterol”) based assessment of dinoflagellate productivity is of insufficient sensitivity. In collaboration with the Royal Netherlands Institute for Sea Research (Royal NIOZ) we conducted the first down-core comparison of paleogenetic, lipid, and cyst-based dinoflagellate signatures in OM-rich Holocene sediments from Ellis Fjord (Antarctica). This study revealed that while dinocysts were extremely rare, paleogenetic signatures revealed substantial diversity in dinoflagellate species, and recorded a shift towards a predominance of the sea-ice dinoflagellate Polarella glacialis at ~1850 calendar years before the present (cal a BP), indicative for a colder climate with more extensive ice cover. Notably, the latter organism does not produce dinosterol and hence was absent from the lipid-based dinoflagellate record (Boere et al., 2009).
This publication resulted in a recent collaboration with Prof. Henk Brinkhuis and Dr. Francesca Sangiorgi from the University of Utrecht, Netherlands. With access to a 180 m-long IODP core spanning 18,000 years of deposition we reconstructed Holocene dinoflagellate communities as proxies for past environmental conditions in eastern Antarctica using a paired analysis of organic-walled dinocysts and Ion Torrent PGM sequencing of short, preserved dinoflagellate genetic markers. This project is ongoing.