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Geiger, E. F., University of Delaware, Lewes, USA, egeiger@udel.edu
Cimino, M. A., University of Delaware, Lewes, USA, mcimino@udel.edu
MacDonald, D. ., University of Delaware, Lewes, USA, uri@udel.edu
Oliver, M. J., University of Delaware, Lewes, USA, moliver@udel.edu
Luther, G. W., University of Delaware, Lewes, USA, luther@udel.edu

DETERMINATION OF PHYTOPLANKTON PHYSIOLOGY FROM THE OXIC THROUGH THE ANOXIC ZONE IN THE CHESAPEAKE BAY USING IN SITU FIRE FLUOROMETRY AND VOLTAMMETRY

The Chesapeake Bay has high concentrations of sulfide at depth due to seasonal hypoxia/anoxia in the upper and middle regions of the bay. The most pronounced oxygen depletion is in late July through August. Short-term (2-4 hour) mixing processes due to tides can dramatically change the chemical structure and extent of the oxic/suboxic/sulfidic zones. We observed the effect of this rapidly changing chemical structure on phytoplankton physiology from July 26th to July 29th 2011 at a station just south of the Chesapeake Bay Bridge. We measured cell physiology and PAR with a newly developed in situ FIRe while simultaneously measuring H2S and O2 with in situ voltammetry. As measurements were made in real time, water was pumped from the same depth for the shipboard determination of cell size distribution and nutrients (NO3- and PO4-). At the surface, Fv/Fm values followed a regular day/night cycle whereas mid-day values decreased due to non-photochemical quenching. Fv/Fm dropped to zero in the suboxic/sulfidic zone indicating there were no organisms utilizing photosystem II at these depths. This coincided with decreasing cell size with depth

Oral presentation

Session #:148
Date: 2/21/2012
Time: 15:00
Location: Room 151

Presentation is given by student: Yes