Dual control of the levels of photoprotective compounds by UVR and temperature in freshwater copepods.

PATRICIA GARCÍA,; PATRICIA PÉREZ,; DEL CARMEN DIÉGUEZ, MARÍA; MARCELA FERRARO,; HORACIO ZAGARESE

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Año: 2008 vol. 30 p. 817 - 827

0142-7873

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 arestill unclear. In this study, we analysed the variability of carotenoids and MAAs in a populationof 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 clearseasonal pattern. Nevertheless, both groups of PPCs reached their maxima during spring andminima 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 bytemperature 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 temerature.In addition, by breaking down the bioaccumulation processes into uptake and elimination, wewere 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 ultimatelydictates 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.