Dinoflagellate cyst paleoecology during the Pliocene–Pleistocene climatic transition in the North Atlantic

Dinoflagellate cysts (dinocysts) are widely used as tracers of sea surface conditions in late Quaternary marine records. However, paleoenvironmental reconstructions across the Pliocene–Pleistocene climatic transition and beyond are limited because the hydrologic conditions influencing assemblage compositions may not have a modern analogue, and the ecological optima of extinct dinocyst species are not well known. From a study of two cored sites in the central and eastern North Atlantic, we bypass these issues by statistically analyzing the variations in dinocyst assemblage composition and comparing the results directly to paleoecological parameters (δ18Obulloides, δ18Osalinity, and geochemical proxies for sea surface temperature [SST]) derived from the planktonic foraminifer Globigerina bulloides recovered from the same samples as the dinocysts. Through canonical correspondence analysis we demonstrate the co-variation of seasonality and dinocyst paleoproductivity. We show that Pyxidinopsis braboi is a cold tolerant species with an optimum SST between 12 and 14 °C. We extend the use of Nematosphaeropsis labyrinthus as an indicator of transitional climatic conditions to the Pliocene, we offer evidence for the correlation of Bitectatodinium tepikiense and Filisphaera microornata to high seasonality, and we reiterate an apparent link between Spiniferites mirabilis and eastern North Atlantic water masses. Finally, we confirm that Habibacysta tectata is cold-tolerant rather than a strictly cold-water indicator, that Operculodinium? eirikianum is a cold-intolerant species favoring outer neritic environments, and that Ataxiodinium confusum and Invertocysta lacrymosa are both warm-water species