HR: 15:20h
AN: PP43D-06    [Abstracts]
TI: Biomarker Constraints on Arctic Surface Water Conditions During the Middle Eocene
AU: * Speelman, E N
EM: e.speelman@geo.uu.nl
AF: Utrecht University, Faculty of Geosciences, Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Reichart, G
EM: reichart@geo.uu.nl
AF: Utrecht University, Faculty of Geosciences, Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Brinkhuis, H
EM: brinkhuis@bio.uu.nl
AF: Utrecht University, Faculty of Sciences, Department of Biology, Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Utrecht University, Faculty of Geosciences, Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 4, 't Horntje (Texel), 1797 SH, Netherlands
AU: de Leeuw, J M
EM: deleeuw@nioz.nl
AF: Utrecht University, Faculty of Geosciences, Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AU: de Leeuw, J M
EM: deleeuw@nioz.nl
AF: Royal Netherlands Institute for Sea Research (NIOZ), Landsdiep 4, 't Horntje (Texel), 1797 SH, Netherlands
AU: van Kempen, M
EM: M.vankempen@science.ru.nl
AF: Radboud University Nijmegen, Institute for Water and Wetland research, Corneniuslaan 4, Nijmegen, 6525 HP, Netherlands
AB: Through analyses of unique microlaminated sediments of Arctic drill cores, recovered from the Lomonosov Ridge in the central Arctic Ocean during Integrated Ocean Drilling Program (IODP) Expedition 302, it has been shown that enormous quantities of the free floating freshwater fern \textit {Azolla} grew and reproduced in situ in the Arctic Ocean during the middle Eocene (Brinkhuis et al., Nature, 2006).The presence of the freshwater fern Azolla, both within the Arctic Basin and in all Nordic seas, suggests that at least the sea surface waters were frequently dominated by fresh- to brackish water during an interval of at least 800 kyr. However, to which degree the Arctic Basin became fresh and what the consequences of these enormous Azolla blooms were for regional and global nutrient cycles is still largely unknown. Comparing samples of extant Azolla, including its nitrogen fixing symbionts, with samples from the Arctic Azolla interval revealed the presence of a group of highly specific biomarkers. These biomarkers are closely related to similar organic compounds that have been suggested to play a crucial role in the biogeochemistry of nitrogen fixing bacteria. This finding, therefore, potentially implies that this symbioses dates back to at least the middle Eocene. Furthermore, this particular symbiosis was probably crucial in triggering basin wide Azolla blooms. We now aim to measure compound specific stable hydrogen isotope values of these biomarkers which should provide insight into the degree of mixing between high salinity (isotopically heavy) deeper and low salinity surface water (isotopically light). The results of these compound specific isotope analyses will be extrapolated using calibrations from controlled growth experiments and subsequently evaluated using climate modeling experiments.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1055 Organic and biogenic geochemistry
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4928 Global climate models (1626, 3337)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting