PARENT SESSION
Symposium 13: Interdisciplinary Challenges in the Biogeosciences
Organized by: L Hedin and R Jackson
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Oglethorpe Auditorium.
The coevolution of elemental stoichiometry in the biogeosphere.
Falkowski, Paul1, 1 Rutgers, The State University of New Jersey, New Brunswick, NJ, US
ABSTRACT- The elemental stoichiometry of C,N,P,S and 13 trace elements varies in relation to phylogenetic affiliation in 16 species of marine phytoplankton representing extant taxa that sequentially evolved over 3 Ga, from the Archean through the Cenozic. Our analysis suggests that, whereas average elemental compositions emerge as a function of scale in aquatic ecosystems, taxon-specific compositions are readily inferred that correspond to evolutionary trends in the fossil record. The taxon-specific signatures cluster with plastid inheritance, but the genes responsible for the inherited bulk characteristics were transferred to the host-cells' genomes early in the symbiotic association. The light elements have left a geochemical imprint in the soluble phase of the oceans, while the trace element composition of the organisms is reflected in black shales and sapropels. This evolutionary trajectory was further modified by terrestrial ecosystems through the emergence and radiation of grazing mammals and the rise of grasses in the Cenozoic; processes that strongly influenced the weathering supply of essential elements such as P, Si, and Fe. Our results suggest that the mobilization, acquisition, and transformation of trace elements by marine photoautotrophs has imprinted lithospheric composition since the evolution of life on Earth.
Key words: stoichiometry