Aquatic Sciences Meeting, Albuquerque 2001

CS24 Optics

Date: Tuesday, February 13, 2001, Time: 3:45:00 PM

Location: Sandia/Santa Ana

Westberry, T, K, ICESS, UCSB, Santa Barbara, USA, toby@icess.ucsb.edu

Siegel, D, A, ICESS, UCSB, Santa Barbara, USA, davey@icess.ucsb.edu

Phytoplankton natural fluorescence in the Sargasso Sea: Prediction of primary production rates or an index for eddy induced nutrient fluxes

Phytoplankton fluorescence has been proposed as a means of assessing biomass and primary production rates in laboratory, in situ, and satellite-based investigations. We present a time series of the quantum yield of phytoplankton fluorescence, PhiF, taken from the northwestern Sargasso Sea. We find that accounting for Raman and elastic scattering, as well as the conversion of planar to scalar irradiance is important for accurately computing PhiF. Predictions of depth-dependent and depth-integrated primary production rates using natural fluorescence are marginally successful (r^2 <= 50%), although they are comparable with results from global models for this region. Improvements are hindered by weak statistical relationships with other physical and biological parameters. Variability in PhiF occurs on both seasonal and episodic time scales. Seasonal variations show maxima in the surface layer during summer months and lower, more uniform values throughout the winter when deep mixing occurs. Episodic changes in PhiF associated with shoaling of isopycnals are observed during the summer which may be attributed to an 'eddy pumping' mechanism. These results suggest that determinations of Phif may be useful for assessing the nutritional status of phytoplankton populations.

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Aquatic Sciences Meeting, Albuquerque 2001

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