KWRRI Research Reports


The possibility that pollution might deplete the stratospheric ozone layer and intensify solar UV at the earth's surface focuses attention on the role of solar UV in the various ecosystems at the earth's surface. Previous studies suggested that solar UV might contribute to bacterial die off in wastewater and the studies reported here were directed toward elucidating the action of solar UV in "natural" waters.

It has been assumed that solar UV action on aquatic ecosystems can be evaluated (using proper models) on the basis of the following four independently measurable quantities: I) the intensity of solar UV at the water surface, 2) the attenuation of the UV in the water column, 3) the position of the critical organisms in the water, and 4) the sensitivity of the individual organisms to solar UV exposure. These four factors have been investigated on a continuing basis and the results of measurements have been utilized along with special field and laboratory experiments to assess UV-B actions.

Field work has focused on the succession of organisms, their locations in the water column, a,d under more controlled conditions, the killing of E. coli by natural sunlight. Laboratory work has included studies of UV-B lethality, its ability to stimulate positioning responses, and its depression of the photosynthetic activity of algae. Laboratory and field observations have been interpreted through models and our results are consistent with the hypothesis that solar UV is a significant agent for the aquatic microorganisms we have tested.

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Funding Information

The work on which this report is based was supported in part by funds provided by the Office of Water Resources Research and Technology, United States Department of the Interior, as authorized under the Water Resources Act of 1964.