JPR Advance Access published online on December 1, 2005
Journal of Plankton Research, doi:10.1093/plankt/fbi108
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1 Department of Earth and Environmental Sciences, 31 Williams Drive, Lehigh University, Bethlehem, Pennsylvania 18015-3188, USA
* To whom correspondence should be addressed. Zooplankton tolerant to ultraviolet radiation (UVR) could be indirectly affected by UVR through interactions with UV-sensitive species in the same ecosystem. In Lake Giles, Pennsylvania, USA, the calanoid copepod Leptodiaptomus minutus is more UVR-tolerant than the cohabiting species Daphnia catawba and Cyclops scutifer. We asked if L. minutus is affected by UV- induced mortality of a food competitor (D. catawba) or a predator of its nauplii (C. scutifer). We conducted two in situ enclosure experiments with six treatments: L. minutus alone, L. minutus + Daphnia, and L. minutus + Cyclops in the presence and absence of UVR. There were few differences in survival among treatments in Experiment 1, which had enhanced food and a cumulative UVR (320 nm) dose of 9.3 kJ m-2. In Experiment 2, which had ambient food and a UVR (320 nm) dose of 20.0 kJ m-2, L. minutus survival and reproduction were higher in the +UVR compared to -UVR, regardless of competitors or predators. Chlorophyll a in Experiment 2 was higher in the +UVR than -UVR. While interactions between zooplankton species of differing UVR tolerances is potentially important, these results instead demonstrate that the beneficial UVR effect on L. minutus is independent of concurrent detrimental UVR effects on competitors and predators. Further research on the phytoplankton community is necessary to determine if UVR alleviates bacterial competition, increases nutrient availability, or affects phytoplank ton by other mechanisms. Communicating Editor: KJ Flynn
Received September 1, 2005
Accepted November 24, 2005
Article
Positive effects of UV radiation on a calanoid copepod in a transparent lake: do competition, predation, or food availability play a role?
Sandra L. Cooke 1 *
and
Craig E. Williamson 2
2 Department of Earth and Environmental Sciences, 31 Williams Drive, Lehigh University, Bethlehem, Pennsylvania 18015-3188, USA; Present address: Department of Zoology, 212 Pearson Hall, Miami University, Oxford, Ohio 45056, USA
Sandra L. Cooke, E-mail: sac6{at}lehigh.edu
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