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Dual control of the levels of photoprotective compounds by UVR and temperature in freshwater copepods
PATRICIA PÉREZ; MARÍA DEL CARMEN DIEGUEZ; MARCELA FERRARO; HORACIO ZAGARESE
Conferencia; Global Environmental Changes: Regional Challenges; 2006
Diversitas, IGBP, IHDP adn WCRP
Photoprotective compounds (PPCs) are ubiquitous chemicals in aquatic organisms. On an evolutionary time scale, the acquisition PPCs is regarded as a precondition for the colonization of ultraviolet (UV) exposed habitats. Based on the premise that PPCs are produced in response to UV radiation, several authors have attempted reconstructions of recent past (103 years) UV radiation environments from analyses of fossil PPCs in sediment cores. However, at shorter time scales, the mechanism capable of explaining the natural variation of PPCs concentration in planktonic animals has remained elusive for nearly a century. In fact, although higher PPCs concentrations enhance the survival of zooplankton exposed to high irradiances, field studies often show maximum PPCs concentrations in winter, lack of significant relationships with irradiance and strong inverse relationships with temperature. In this paper we confirm that UV radiation triggers the acquisition of PPCs, but demonstrate that temperature controls their uptake and elimination rates. Our findings have profound implications for understanding future climate scenarios, as well as for the reconstruction of past UV climatology. The general trend showing that PPCs concentrations are expected to decrease with temperature tacitly implies that global warming may jeopardize the effectiveness of PPCs to counteract the damaging effects of increased UV exposure due to both stratospheric ozone depletion or decrease in the organic matter inputs on account off climate warming. Moreover, an increase in temperature may, by itself, generate photo-toxicity stress in cold adapted populations.