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

PATRICIA E., GARCIA; PEREZ, A. P.; DIEGUEZ, M. C.; FERRARO, M. A.; ZAGARESE, H. E.

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 regulation 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 withput a clear seasonal pattern. Nevertheless, both groups of PPCs reached their maxima during spring and minima during summer. Inverse relationship 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 futher investigated the effect of radiation regime and temperature on the bioaccumulation of PPCs in controlled laboratory experiments. We found that the concentration 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 oncreased 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 recontruct or predict the photoprotective responses of aquatic organisms to the past or future climate scenarios.