Palaeoproductivity and post-depositional aerobic organic matter decay reflected by dinoflagellate cyst assemblages of the Eastern Mediterranean S1 sapropel

In this study, the coccolith compositions of 213 surface sediment samples from the South Atlantic and Southern Ocean were analysed with respect to the environmental parameters of the overlying surface waters. From this data set, the abundance patterns of the main species and their ecological affinities were ascertained. In general, Emiliania huxleyi is the most abundant species of the recent coccolith assemblages in the study region. However, the lower photic zone taxa, composed of Florisphaera profunda and Gladiolithus flabellatus often dominate the assemblages between 20°N and 30°S. If E. huxleyi is excluded, Calcidiscus leptoporus and F. profunda become the most abundant species, each dominating discrete oceanographic regimes. While F. profunda is very abundant in the sediments underneath warmer, stratified surface waters with a deep nutricline, Calcidiscus leptoporus is encountered in high-productivity environments. Furthermore, the results of a canonical correspondence analysis reveal affinities of Gephyrocapsa spp., Helicosphaera spp. and Coccolithus pelagicus for intermediate to higher nutrient conditions in a well-mixed upper water column. In contrast, Gladiolithus flabellatus seems to be associated with high temperatures and salinities under low-nutrient conditions. Based on the relative abundances of Calcidiscus leptoporus, F. profunda, Gladiolithus flabellatus, Helicosphaera spp., Umbilicosphaera foliosa, Umbilicosphaera sibogae and a group of subordinate subtropical species, six surface sediment assemblages have been identified, which reflect the distribution and characteristics of the overlying surface waters. Their distribution appears to be mainly a function of the relative position of the nutricline and thermocline in the overlying photic zone.

Coccolith distribution patterns in South Atlantic and Southern Ocean surface sediments in relation to environmental gradients

High-resolution, well-dated calcareous dinoflagellate cyst and organic carbon records from a 58 kyr sediment core (M35003-4) located southeast of the island of Grenada show that rapid and pronounced changes in cyst association and accumulation and organic carbon deposition occurred, controlled by (1) a significant southward shift in the position of the North Equatorial Current during the last glacial period and the Younger Dryas cold interval and (2) rapid changes in local productivity in marine isotopic stage 3 that are associated with variations in Orinoco River nutrient discharge and coastal upwelling strength. Prominent cyst accumulation peaks representing extremely oligotrophic and stratified thermocline conditions mimic the Greenland ice core and northern Atlantic Dansgaard/Oeschger stadials and Heinrich events. We provide new evidence for a coupled tropical/high-latitude Atlantic climate system during the last glacial period and suggest that changes in the zonality of the low-latitude winds may play an important role in modulating rapid interhemispheric climate variability.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000PA000582

Shifts in the position of the north equatorial current and rapid productivity changes in the western tropical Atlantic during the last glacial

Calcareous dinoflagellates are considered to be a monophyletic group of peridinoid taxa that have the potential to produce calcified exoskeletal structures during the life cycle, or that derive fro ...

Establishing an Agenda for Calcareous Dinoflagellate Research (Thoracosphaeraceae, Dinophyceae) including a nomenclatural synopsis of generic names

Calcareous dinoflagellate cysts in South and equatorial Atlantic surface sediments: diversity, distribution, ecology and potential for palaeoenvironmental reconstruction

Aanja Brune

Papers

Spatial distribution of calcareous dinoflagellate cysts in surface sediments of the Atlantic Ocean between 13°N and 36°S.