Reorganization of Southern Ocean Plankton Ecosystem at the Onset of Antarctic Glaciation

Abstract

The circum-Antarctic Southern Ocean is an important region for global marine food webs and carbon cycling because of sea-ice formation and its unique plankton ecosystem. However, the mechanisms underlying the installation of this distinct ecosystem and the geological timing of its development remain unknown. Here, we show, on the basis of fossil marine dinoflagellate cyst records, that a major restructuring of the Southern Ocean plankton ecosystem occurred abruptly and concomitant with the first major Antarctic glaciation in the earliest Oligocene (~33.6 million years ago). This turnover marks a regime shift in zooplankton-phytoplankton interactions and community structure, which indicates the appearance of eutrophic and seasonally productive environments on the Antarctic margin. We conclude that earliest Oligocene cooling, ice-sheet expansion, and subsequent sea-ice formation were important drivers of biotic evolution in the Southern Ocean.

Links between CO<sub>2</sub>, glaciation and water flow: reconciling the Cenozoic history of the Antarctic Circumpolar Current

“…In addition, the Antarctic glaciation cools the continent and the surrounding ocean, leading to an increase in sea ice formation (DeConto et al, 2007;Goldner et al, 2014;Houben et al, 2013). Our results support the development of a proto-ACC of moderate intensity following the buildup of the ice sheet, roughly coeval with the EO (Eocene-Oligocene) transition onset of the ACC suggested by, e.g., Latimer and Filippelli (2002), Diekmann et al (2004) and more recently Borrelli et al (2014).…”

Stratigraphic calibration of Oligocene–Miocene organic-walled dinoflagellate cysts from offshore Wilkes Land, East Antarctica, and a zonation proposal

“…The latter means that the distribution of many dinocyst taxa found in Southern Ocean sediments is restricted to that region (e.g. Zonneveld et al, 2013;Houben et al, 2013). These typical Southern Ocean assemblages were essentially established during the Eocene-Oligocene transition, in conjunction with the onset of major Antarctic cryosphere growth .…”

“…Reworked Eocene taxa dominate the palynological assemblages in the lowermost 30 m of the Oligocene (Cores 95R to 93R; Houben et al, 2013). In the lower Oligocene, the percentage of reworked elements decreases to around 10-15 % of the total palynomorph count .…”

“…Studies on Oligocene-Neogene dinocyst assemblages have been carried out on sediment cores from Prydz Bay (Hannah, 2006;Warnaar, 2006;Houben et al, 2013), Cape Roberts (Hannah et al, 1998(Hannah et al, , 2000(Hannah et al, , 2001a, within the Cenozoic Investigation in the Western Ross Sea (CIROS) program (Hannah, 1994(Hannah, , 1997, the Antarctic Geological Drilling (ANDRILL) program in the Ross Sea (Warny et al, 2009), and Ocean Drilling Program (ODP) Site 696 in the Weddell Sea (Warnaar, 2006;Houben et al, 2013). Further north in the Southern Ocean, dinocyst records have been generated from ODP Site 1168 (Brinkhuis et al, 2003a) and Deep Sea Drilling Project (DSDP) Site 511 (Goodman and Ford Jr., 1983;Houben et al, 2011).…”

Untitled

“…Micropaleontological, geochemical, and sedimentological records from drill cores from all Expedition 374 sites will provide reconstructions of changing regional surface conditions (e.g., sea ice, surface stratification, sea-surface temperatures [SSTs], polynya mixing, glacial meltwater discharge, nutrient uptake, and supercooling of dense waters by ice shelves) proximal to Antarctica's ice sheets (e.g., Houben et al, 2013;Levy et al, 2016;McKay et al, 2012a;Shevenell et al, 2011) and thus AASW (and SCW) formation. Additionally, downslope currents resulting from the transfer of High-Salinity Shelf Water into the abyssal ocean can also be assessed (and distinguished from ASC flow) by integrated facies analysis, geochemistry, micropaleontology, and seismic profiles (e.g., Caburlotto et al, 2010;Hepp et al, 2006;Lucchi and Rebesco, 2007) at primary Sites RSCR-11A and RSCR-02B.…”