Aquatic Sciences Meeting, Albuquerque 2001

SS21 Ultraviolet Radiation and the Aquatic Biota (Disciplinary Connections)

Date: Wednesday, February 14, 2001, Time: 11:45:00 AM

Location: Galisteo

Cullen, J, J, Dalhousie University, Halifax, Canada, John.Cullen@Dal.CA

Davis, R, F, Dalhousie University, Halifax, Canada, Richard.Davis@Dal.CA

Huot, Y, , Dalhousie University, Halifax, Canada, yhuot@is2.dal.ca

Lehmann, M, K, Dalhousie University, Halifax, Canada, mlehmann@is2.dal.ca

PARAMETERIZATION OF WATER COLUMN PHOTOSYNTHESIS AND ITS INHIBITION BY UV RADIATION

Numerical procedures and biological data are now available for calculating water column photosynthesis and its inhibition by UV as a function of location, time, water clarity (spectral attenuation), cloudiness, stratospheric ozone, and biological sensitivity to UV. These fully-spectral models are cumbersome however, so sensitivity analysis to answer important questions is somewhat complicated and constrained by the choice of factors that are manipulated. To simplify analyses, we started with a published approach (W.F. Vincent et al.) and developed parameterizations of spectral irradiance and attenuation. Four dimensionless parameters are calculated: 1) spectral transparency, weighted according to the spectral shape for photosynthetically utilizable radiation (T*PUR); 2) transparency weighted for photosynthetically inhibiting radiation (T*PIR); 3) surface PUR scaled to the saturation irradiance for photosynthesis (E*PUR); and 4) surface irradiance weighted for PIR (E*PIR). Simple power functions of these parameters reproduce almost exactly the results of a full-spectral numerical model of water column photosynthesis and its inhibition by UV for a broad range of water types and solar angles. The dimensionless parameters can be derived from measurements of ocean color and published functions describing photosynthesis and inhibition.

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Aquatic Sciences Meeting, Albuquerque 2001

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