HR: 0830h
AN: B31D-0324    [PDF]
TI: Examination of an Oligocene Lacustrine Ecosystem Using C and N Stable Isotopes
AU: * Schweizer, M K
EM: mschweiz@princeton.edu
AF: Carnegie Inst. of Wash. Geophysical Laboratory, 5251 Broad Branch Rd NW, Washington, DC 20015 United States
AU: * Schweizer, M K
EM: mschweiz@princeton.edu
AF: Princeton University, Department of Geosciences, Princeton, NJ 08544 United States
AU: Wooller, M J
EM: ffmjw@uaf.edu
AF: Carnegie Inst. of Wash. Geophysical Laboratory, 5251 Broad Branch Rd NW, Washington, DC 20015 United States
AU: Wooller, M J
EM: ffmjw@uaf.edu
AF: University of Alaska, Fairbanks, Stable Isotope Lab 525 Duckering Building, Fairbanks, AK 99775 United States
AU: Toporski, J
EM: j.toporski@gl.ciw.edu
AF: Carnegie Inst. of Wash. Geophysical Laboratory, 5251 Broad Branch Rd NW, Washington, DC 20015 United States
AU: Fogel, M
EM: m.fogel@gl.ciw.edu
AF: Carnegie Inst. of Wash. Geophysical Laboratory, 5251 Broad Branch Rd NW, Washington, DC 20015 United States
AU: Steele, A
EM: a.steele@gl.ciw.edu
AF: Carnegie Inst. of Wash. Geophysical Laboratory, 5251 Broad Branch Rd NW, Washington, DC 20015 United States
AB: Stable isotopes of C and N are used to reconstruct the fossil Oligocene (25.8Ma) ecosystem at Lake Enspel, Westerwald, Germany. Enspel was a steep-sided, deep maar lake with anoxic bottom waters. Upon dying, terrestrial and aquatic organisms sank into the sediment where they were colonized by bacteria. These bacteria quickly became fossilized, preserving morphological detail and large amounts of organic matter from the original macroorganism. Carbon and nitrogen are sufficiently preserved in these fossils to permit stable isotope analysis. Stable isotopic signatures identify several trophic levels, including primary producers (terrigenous and aquatic plants, diatoms), primary consumers (tadpoles, some insects), and secondary consumers (carnivores such as fish). Primary producers are associated with depleted d13C and d15N values, primary consumers such as flies are one trophic shift higher, and fish are another shift higher. Signatures for the fish species show heavy-isotope enrichment correlated with increasing length, indicating an increasingly carnivorous diet. This study marks the first attempt to reconstruct a complete fossil ecosystem using stable isotope analysis, and confirms that techniques used to study modern food webs can be applied to extinct webs as well.
DE: 1055 Organic geochemistry
DE: 1694 Instruments and techniques
DE: 4803 Bacteria
DE: 4870 Stable isotopes
DE: 9820 Techniques applicable in three or more fields
SC: Biogeosciences [B]
MN: 2003 Fall Meeting