The use of organic proxies as a way of reconstructing ancient climates and environmental conditions is well-established in paleoclimatology, paleoecology, and paleogeography. The measurement of stable isotopes and trace metals in microfossil shells are, for example, one of the most recurrent techniques used to assess the geochemical conditions of early ecosystems and the configuration of ancient ecotones. Simply put, the environmental conditions upon which early microorganisms have developed influence the geochemical composition of their organic hard structures, structures that, when fossilized, retain and transport valuable information about the climates and ecosystems of the past. Foraminifers shells (known as tests) are most recurrently used, but other fossilizable structures are useful and have been gaining wider interest and application. Dinoflagellate cysts are a dormant (resting) stage of the dinoflagellate life cycle with resistance characteristics, easily found in the fossil record. They have been used since the late 1970s as environmental paleoproxies.
This study explores new data on dinoflagellate cysts (dinocysts) paleoecology (Pliocene-Pleistocene boundary) in order to provide several clues into how the ecological restrictions of dinoflagellate species might be used as a proxy for the environmental conditions of deposition in the North Atlantic area. The international team of researchers that authors the study reports that, based on their analysis, the dinocyst burial flux (a well-established proxy for paleoproductivity) appears to be seasonality determined, a conclusion that might lead to the broadening of the proxy’s applicability and significance.
Four contributes into the paleoecology of dinocyst species are then given, to broaden understanding on how particular species might be useful as climate proxies in the Pliocene-Pleistocene boundary:
• The cold water species Pyxidinopsis braboi is reported as having a SST optimum between 11.7 and 13.8 °C.
• Habibacysta tectata is identified as a cool-tolerant rather than a cold water indicator, as previously thought.
• Nematosphaeropsis labyrinthus is found to thrive in Early Pleistocene transitional conditions.
• Finally, in this study, Bitectatodinium tepikiense is linked to increases in seasonality.
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Title: “Dinoflagellate cyst paleoecology during the Pliocene–Pleistocene climatic transition in the North Atlantic”
Authors: Jan A.I. Hennissena, Martin J. Heada, Stijn De Schepperd, & Jeroen Groenevelde
Publisher: Palaeogeography, Palaeoclimatology, Palaeoecology
Read it online: article page.
“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.”
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