HR: 1330h
AN: B12B-0783    [PDF]
TI: Climate Change and Planktic Foraminiferal size Evolution
AU: * Schmidt, D N
EM: d.schmidt@gl.rhul.ac.uk
AF: Royal Holloway University of London, Department of Geology, Egham, TW20 0EX United Kingdom
AU: Kucera, M
EM: m.kucera@gl.rhul.ac.uk
AF: Royal Holloway University of London, Department of Geology, Egham, TW20 0EX United Kingdom
AU: Renaud, S
EM: Sabrina.Renaud@univ-lyon1.fr
AF: CNRS University Lyon, Centre de Paleontologie Stratigraphique et Paleoecologie FRE 2158 CNRS UCB Lyon 1 43 bd du 11 novembre, Villeurbanne, 69622 France
AU: Thierstein, H R
EM: thierstein@erdw.ethz.ch
AF: ETH Zrich, Geological Institute Sonneggstr. 5, 8092, Zurich Switzerland
AB: Planktic foraminifers are a major producer for pelagic carbonate since the late Cretaceous. The production of foraminiferal carbonate is related to the size, shape, and distribution of individual species. We have analysed size and shape of planktic foraminifers in relation to global environmental changes during the Neogene. Morphological changes may be a response to either geographical or temporal environmental changes. Alternatively, species might avoid climatic stress by shifting their distribution area. We have analysed the morphological response on two different time-scales (entire Neogene, late Quaternary) and at two taxonomic levels (species, family). On short time-scales (140 kyrs) Globorotalia truncatulinoides at three different locations in the South Atlantic had stable environmental preferences and reacted to the climatic changes by habitat tracking. This process of habitat tracking allows a species continued exploitation of its ecological niche despite environmental changes. During the Neogene, in contrast, a growth to gigantism from mid-Miocene to Recent was identified in tropical and subtropical foraminiferal assemblages, whereas in polar areas the size of foraminifers stayed rather stable over the entire time interval. The higher calcification rates leading to larger final size may have resulted in an increased export production of inorganic carbonates to the sea floor. The dominant environmental change throughout the Neogene is high latitude cooling. Despite the ecological and physiological evidence for a positive correlation of planktic foraminiferal test size with temperature today, we identify a more intricate mechanism of environmental forcing of foraminiferal size evolution in the geological record. We can demonstrate, that changes in surface water stratification, rather than temperature per se, had likely determined growth rates and test sizes of planktic foraminifers. Increases in size have occurred during times of strong vertical water stratification in low latitudes during polar cooling phases. Vertical surface water heterogeneity increases the number of ecological niches and thus allows for specific adaptations and, evidently, growth towards larger size. The onset of the dramatic size increase in planktic foraminifers falls within the Monterrey event, a rapid extraction of carbon from the Ocean-Atmosphere system through a massive deposition of organic carbon. Whether these two events are related and have a common cause is highly speculative at the moment, but it appears that global climatic changes certainly have influenced growth of planktic foraminifer tests and therefore carbonate deposition.
DE: 3030 Micropaleontology
DE: 4267 Paleoceanography
DE: 4806 Carbon cycling
DE: 4855 Plankton
SC: Biogeosciences [B]
MN: 2003 Fall Meeting