Aquatic Sciences Meeting, Albuquerque 2001

SS21 Ultraviolet Radiation and the Aquatic Biota (Disciplinary Connections)

Date: Wednesday, February 14, 2001, Time: 2:00:00 PM

Location: Galisteo

Sardina, T, J, Temple University, Philadelphia, USA, formalcharge@hotmail.com

Sanders, R, W, Temple University, Philadelphia, USA, rsanders@nimbus.temple.edu

PHOTOENZYMATIC REPAIR BY A FRESHWATER CILIATE EXPOSED TO UV-B RADIATION: EFFECTS OF UV-B INTENSITY AND TEMPERATURE

UV-B radiation can cause direct damage to the DNA of organisms in surface waters of oligotrophic environments. Photoenzymatic repair (PER), a major mechanism for reversing this damage, is dependent on an enzyme (photolyase) plus UV-A and visible light. To examine PER in a ciliate from an oligotrophic lake, treatments were either: 1) exposed simultaneously to UV-B plus UV-A and visible wavelengths; or 2) had the repair wavelengths blocked. Experiments were run at three UV-B intensities and at three temperatures. Blocking repair radiation in UV-B exposed treatments typically resulted in 100% mortality. Treatments receiving UV-B plus repair radiation always had lower population growth than dark controls, while those exposed to higher UV-B intensities had reduced growth rates relative to low UV-B treatments. PER rescued populations at a higher UV-B intensity at 20C and 25C relative to 15C. However, growth rates at 25C were reduced relative to those exposed to the same UV-B intensities at 20C. PER appears to be an important mechanism adapting this ciliate to a high UV environment, but cannot sustain populations at the maximum expected surface UV-B exposure.

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Aquatic Sciences Meeting, Albuquerque 2001

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