Dual control of the levels of photoprotective compounds by ultraviolet radiation and temperature in the freshwater copepod Boeckella antiqua

PATRICIA ELIZABETH GARCÍA; ALEJANDRA PATRICIA PÉREZ; MARÍA DEL CARMEN DIÉGUEZ; MARCELA ANDREA FERRARO; HORACIO ERNESTO ZAGARESE

JOURNAL OF PLANKTON RESEARCH

Oxford University Press

Lugar: Oxford; Año: 2008 vol. 30 p. 817 - 827

0142-7873

Photoprotective compounds (PPCs), such as carotenoids and mycosporine-like aminoacids (MAAs), confer photoprotection to aquatic organisms against harmful ultraviolet-B (UV-B) radiation. The natural variability of these compounds in zooplankton has been related to temperature, radiation and diet, but the ultimate mechanisms regulating the observed field patterns are still unclear. In this study we analyzed the variability of carotenoids and MAAs in a population of the calanoid copepod Boeckella antiqua of 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 PPCs reached their maxima during spring and minima during summer. Inverse relationships were found between carotenoid concentrations vs. 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 UV-B 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 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 to 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.