JPR Advance Access originally published online on March 27, 2008
Journal of Plankton Research 2008 30(7):817-827; doi:10.1093/plankt/fbn041
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Dual control of the levels of photoprotective compounds by ultraviolet radiation and temperature in the freshwater copepod Boeckella antiqua
1 Laboratorio de Fotobiología, Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, (8400) San Carlos de Bariloche, Río Negro, Argentina 2 Laboratorio de Ecología y Fotobiología Acuática, Instituto de Investigaciones Biotecnológicas, Instituto Tecnológico de Chascomús (IIB-INTECH), CC 164 (B7130IWA) Chascomús, Buenos Aires, Argentina
* CORRESPONDING AUTHOR: dieguezmc{at}gmail.com
Received on January 18, 2008; accepted on March 17, 2008
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Abstract |
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Photoprotective compounds (PPCs), such as carotenoids and mycosporine-like amino acids (MAAs), confer photoprotection to aquatic organisms against harmful ultraviolet-B (UVB) radiation. The natural variability of these compounds in zooplankton has been related to temperature, radiation and diet, but the ultimate mechanisms regulating the observed patterns in the field are still unclear. In this study, we analysed the variability of carotenoids and MAAs in a population of the calanoid copepod Boeckella antiqua in a shallow pond located in Northern Patagonia (Argentina). During our field survey, carotenoids and MAAs in B. antiqua varied without a clear seasonal pattern. Nevertheless, both groups of PPCs reached their maxima during spring and minima during summer. Inverse relationships were found between carotenoid concentrations versus temperature and irradiance. For MAAs, the same relationships were not significant. Tolerance experiments showed that mortality of B. antiqua was significantly influenced both by temperature and UVB dose, being more vulnerable at high temperature. We further investigated the effect of radiation regime and temperature on the bioaccumulation of PPCs in controlled laboratory experiments. We found that the concentrations of PPCs could be experimentally modified by manipulating radiation exposure and temperature. In addition, by breaking down the bioaccumulation processes into uptake and elimination, we were able to show that (i) the uptake rate was stimulated by photosynthetically active radiation (PAR)+UVA exposure and (ii) both uptake and elimination rates increased with temperature. Thus, the net accumulation (i.e. the balance between uptake and elimination), which ultimately dictates the concentration observed in an animal, could be either positive or negative depending on the specific combination of radiation exposure and temperature. The dual regulation of PPCs by radiation exposure and temperature should be considered in future efforts to reconstruct or predict the photoprotective responses of aquatic organisms to the past or future climate scenarios.
Corresponding editor: John Dolan