Aquatic Sciences Meeting, Albuquerque 2001

SS21 Ultraviolet Radiation and the Aquatic Biota (Disciplinary Connections)

Date: Wednesday, February 14, 2001, Time: 10:30:00 AM

Location: Galisteo

Xenopoulos, M, A, University of Alberta, Edmonton, Canada, max@ualberta.ca

Leavitt, P, R, University of Regina, Regina, Canada, leavitt@uregina.ca

Schindler, D, W, University of Alberta, Edmonton, Canada, d.schindler@ualberta.ca

THE EFFECT OF WATER COLUMN MIXING AND AMBIENT UVR ON PHYTOPLANKTON PIGMENT CONCENTRATIONS IN BOREAL LAKES.

Planktonic algae can physiologically adjust to high UVR by altering their pigment content. For example, some species increase their carotenoid content and others produce UVR absorbing pigments such as scytonemin. We investigated the influence of ambient UVR and water column mixing on the planktonic concentration of pigments in 5 boreal lakes from the Experimental Lakes Area (Ontario, Canada), over two years. The 5 lakes (L224, L225, L227, L302S, L305) differed in their transparency and physico-chemical characteristics. Sampling intervals varied from daily to every three days. Pigments were measured using HPLC. The Lake number (a non-dimensional parameter) was used as a mixing indicator. High concentrations of UVR absorbing pigments were only found in the highly eutrophic L227. Pigments from biomass-dominent chrysophytes (fucoxanthin) and total algae (chlorophyll a) were negatively correlated with UVR exposure, particularly in L302S, a previously acidified lake. Preliminary results indicate that ratios of chlorophyll (a, b or c) to carotenoids were not always influenced by UVR. A reduction of 20-50% in chlorophylls and most carotenoids was seen in periods of very low mixing and high UVR in all lakes studied except L227 and L225 (a high DOC lake).

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Aquatic Sciences Meeting, Albuquerque 2001

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