HR: 11:50h
AN: OS12A-07    [Abstracts]
TI: High resolution coral records of reactive and micronutrient trace metals: Monitoring biological responses to flood plumes.
AU: * Wyndham, T D
EM: timothy.wyndham@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Mills Rd, Canberra, ACT 0200 Australia
AU: McCulloch, M T
EM: malcolm.mcculloch@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Mills Rd, Canberra, ACT 0200 Australia
AU: DeCarlo, E H
EM: edecarlo@soest.hawaii.edu
AF: Department of Oceanography, University of Hawaii, 1000 Pope Rd, Honolulu, HI 96822 United States
AB: The influences of flood plumes on the coastal ocean are difficult to investigate because they are intermittent, transient and highly variable in nature. The application of trace metals in coral carbonates as proxy recorders of marine environmental conditions has been demonstrated as an excellent method for overcoming these difficulties. Coral records of trace metals have been widely used to provide historical records of physical impacts of flood plumes such changing salinity ($\delta$O$^{18}$), sediment load (Ba) and anthropogenic inputs such as heavy metal pollution (eg. Pb, Cd). Despite successful applications to physical properties, the use of coral records to monitoring the biologic responses to these changing environmental conditions has proved more difficult. With improvements in analytical techniques however, it is now possible to investigate coral records of reactive (rare earth elements) and micronutrient (eg Mn, Zn and Cu) trace metals, which can be used to more widely explore the biogeochemical implications of flood plumes to the coastal ocean. We have obtained high resolution temporal records of rare earth elements, Cu, Zn, Mn and Sn, from corals from two locations, (1) near Townsville on the Great Barrier Reef (GBR) and (2) Kaneohe Bay on Oahu, Hawaii. Both of these locations often display large phytoplankton blooms following flood events, providing a good opportunity to test the idea that coral records can be used to monitor the biological response to flood plumes. These coral records show significant responses to flood plumes that can only be attributed to biogeochemical cycling that occurs as a result of the flood plume influence, rather than the flood plume itself. Thus a mechanism for exploring the biological response to flood plumes is provided. It has generally proven difficult however, to interpret these coral records without a good understanding of the coastal processes. Therefore we also include evidence from direct trace metal measurements of a coastal Trichodesmium bloom on the GBR and data from experimental blooms using Kaneohe Bay seawater, induced by nutrient addition. Using this information we discuss the implications for the application of coral records to long term monitoring of biologic responses to flood plumes.
DE: 4805 Biogeochemical cycles (1615)
DE: 4808 Chemical tracers
DE: 4875 Trace elements
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting