Aquatic Sciences Meeting, Albuquerque 2001

SS21 Ultraviolet Radiation and the Aquatic Biota (Disciplinary Connections)

Date: Wednesday, February 14, 2001, Time: 3:45:00 PM

Location: Galisteo

Padeletti, A, T, Lehigh University, Bethlehem, USA, atp3@lehigh.edu

Leech Dina, D, M, Lehigh University, Bethlehem, USA, dml2@lehigh.edu

Williamson Craig, C, E, Lehigh University, Bethlehem, USA, cew0@lehigh.edu

LIGHT INTENSITY AS WELL AS WAVELENGTH INFLUENCES THE VERTICAL MOVEMENTS OF DAPHNIA IN SITU

Both intensity and spectral composition of light have been shown to be important in the vertical migration and associated behavioral responses of zooplankton. We examined the vertical movements of Daphnia in acrylic columns that transmitted full solar radiation (UV+ treatment) or filtered UV-B and short-wavelength UV-A radiation (UV- treatment). Columns were suspended in the epilimnion of two high UV lakes at varying times of day and cloud cover. In general, Daphnia tended to avoid the surface waters in the UV+ treatment but showed preference for the surface waters in UV- treatment. In some case, however, Daphnia avoided the surface in both light treatments. Higher light intensities (less cloud cover) were observed on these dates. We propose that light intensity as well as wavelength are important in determining the vertical distribution of Daphnia in high UV systems. Preliminary data suggest that light intensities greater than 680-800 W/m2 invoke negative phototaxis in Daphnia in nature. Further investigations are needed to better understand these behavioral responses to light intensity and wavelength.

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Aquatic Sciences Meeting, Albuquerque 2001

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