Aquatic Sciences Meeting, Albuquerque 2001

SS21 Ultraviolet Radiation and the Aquatic Biota (Disciplinary Connections)

Date: Wednesday, February 14, 2001, Time: 10:45:00 AM

Location: Galisteo

Hiriart, V, P, INRS-Eau, University of Quebec, Quebec, Canada, veronique_hiriart@inrs-eau.uquebec.ca

Charlton, M, N, Environment Canada, N.W.R.I., Burlington, Canada, murray.charlton@cciw.ca

Greenberg, B, M, Biology Department, University of Waterloo, Waterloo, Canada, greenber@sciborg.uwaterloo.ca

Smith, R, E, Biology Department, University of Waterloo, Waterloo, Canada, rsmith@sciborg.uwaterloo.ca

THE IMPACT OF ULTRAVIOLET RADIATION ON AREAL PRIMARY PRODUCTION IN A LARGE LAKE: THE ROLE OF RECOVERY AND MIXING PROCESSES

A time- and wavelength-dependent model of photoinhibition was developed and calibrated for L. Erie (42 N) phytoplankton, and combined with a simple model of mixing processes. Both model and direct experiments indicated quick recovery (60-100% within 6 hours) from UVR-dependent photoinhibition, but inhibition was also rapid (up to 80% after 2 hours exposure). Areal (i.e. vertically-integrated) daily photoinhibition (PI-int) was higher for mixed than static conditions, yet neither PI-int nor the relative contribution of UVB (290-320 nm), UVA (320-400 nm) and PAR (400-700 nm) to PI-int varied strongly over a wide range of mixing strengths. PI-int for the lake as a whole averaged 13.3% loss of potential production for a typical sunny summer day (2.2% PAR, 9.9% UVA and 1.2% UVB). PI-int was always higher in shallower and turbid areas than in deeper and more transparent areas, and was especially high (18.5%) when shallow, temporary, thermoclines occurred. Sensitivity analysis showed that variations of both damage and recovery rates observed in L. Erie contributed equally to variations in PI-int, which ranged between extremes of 5% and 20%. UVA was consistently dominant in photoinhibition.

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Aquatic Sciences Meeting, Albuquerque 2001

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