A review of the ecological affinities of marine organic microfossils from a Holocene record offshore of Adélie Land (East Antarctica)

Abstract

Abstract. Integrated Ocean Drilling Program (IODP) Expedition 318 recovered a ∼ 170 m long Holocene organic-rich sedimentary sequence at Site U1357. Located within the narrow but deep Adélie Basin close to the Antarctic margin, the site accumulated sediments at exceptionally high sedimentation rates, which resulted in extraordinary preservation of the organic sedimentary component. Here, we present an overview of 74 different mainly marine microfossil taxa and/or types found within the organic component of the sediment, which include the remains of unicellular and higher organisms from three eukaryotic kingdoms (Chromista, Plantae, and Animalia). These remains include phytoplanktonic (phototrophic dinoflagellates and prasinophytes) and very diverse zooplanktonic (heterotrophic dinoflagellates, tintinnids, copepods) organisms. We illustrate each marine microfossil taxon or type identified by providing morphological details and photographic images, which will help with their identification in future studies. We also review their ecological preferences to aid future (palaeo)ecological and (palaeo)environmental studies. The planktonic assemblage shows a high degree of endemism related to the strong influence of the sea-ice system over Site U1357. In addition, we found the remains of various species of detritus feeders and bottom-dwelling scavengers (benthic foraminifers and annelid worms) indicative of high export productivity at Site U1357. This study shows the potential of organic microfossil remains for reconstructing past environmental conditions, such as sea-ice cover and (export) productivity.

Surface-circulation change in the Southern Ocean across the Middle Eocene Climatic Optimum: inferences from dinoflagellate cysts and biomarker paleothermometry

“…in Mediterranean sapropels (e.g., Sangiorgi et al, 2006;van Helmond et al, 2015;Zwiep et al, 2018), Cretaceous Oceanic Anoxic Event 2 shelf sediments (van Helmond et al, 2014) and the Holocene Adélie drift underlying a highly productive polynya system (Hartman et al, 2018). The average dinocyst concentrations at Site 1170 may be converted to average accumulation rates in the order of 10,000-80,000 cysts per cm 2 per yr.…”

Surface-circulation change in the southwest Pacific Ocean across the Middle Eocene Climatic Optimum: inferences from dinoflagellate cysts and biomarker paleothermometry

“…Along with the indirect inferences from modeling and heat distribution based on SST reconstructions, biogeographic patterns of surface-water plankton may be used as a tool to reconstruct surface-ocean circulation. In the Paleogene SO, high levels of endemism characterize a diverse range of fossil groups, including mollusks (Zinsmeister, 1979), radiolarians and diatoms (Harwood, 1991;Lazarus et al, 2008;Pascher et al, 2015), calcareous nannoplankton and planktonic foraminifera (Nelson and Cooke, 2001;Villa et al, 2008), and organic-walled dinoflagellate cysts (dinocysts) (Wrenn and Beckman, 1982;Wrenn and Hart, 1988;Bijl et al, 2011Bijl et al, , 2013a. The endemic dinocyst assemblage from the SO is traditionally referred to as "Transantarctic Flora" (Wrenn and Beckman, 1982).…”

Transport Bias by Ocean Currents in Sedimentary Microplankton Assemblages: Implications for Paleoceanographic Reconstructions

“…Impagidinium pallidum occurs in high abundance in polar regions, although low abundances in other regions have also been reported (Zonneveld et al, ). Finally, S. antarctica is only very high in abundance closer to Antarctica south of the polar front and within the sea ice zone (Prebble et al, ; Zonneveld et al, ), has been reported in high abundance in Holocene polynya‐derived drift sediments (Hartman et al, ) and is used as proxy for sea ice conditions for the geologic past (Bijl et al, ; Houben et al, ). However, S. antarctica also occurs in the sediment sample of station 3627 with 6.1%.…”