Bioaccumulation of photoprotective compounds and Mortality patterns in cold-adapted calanoid Copepods from North Patagonia: synergetics effects of UV radiation and temperatura

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

Norrtälje

Workshop; GLEON 7; 2008

GLEON (Global Lake Ecological Observatory Network)

Climate change is likely to impact aquatic ecosystems in the Patagonia region of Southern South america through different mechanisms: i) direct increase in UV due to ozone depletion, ii) direct effect on water temperature and iii) indirect effects of temperature on tolerance of organisms to UV and changes in the radiation environment mediated by changes in DOC levels. The identification of biological processes influenced by UV exposure and temperature in predictable ways will improve our appreciation of their combined effects on freshwaters. Cold adapted populations of the genus Boeckella are common in freshwaters of South America and may be suitable sentinels of climate change since they also occur in lakes and ponds highly exposed to RUV. In this work we focus in two species of Boeckella, B. antiqua that is restricted to few sites in Northwestern Patagonia and B. gracilis, which has a broad distribution from 31ºS 64ºW to 49ºS 72ºW. We analyse the combined effects of RUV and warming on the bioaccumulation of the photoprotective compounds MAAs (mycosporine-like amino-acids) and on species survivorship. Our result indicate that photoprotection by MAAs in B. antiqua and B. gracilis increase with temperature and exposure to UV radiation. The accumulation of MAAs could be dissected out into uptake and elimination processes, both of which are strongly and predictably influenced by UV and temperature. Bioaccumulation rates of MAAs increase with temperature. The patterns found in both species seem to point out alternative photoprotective strategies. B. gracilis bears high amounts of constitutive MAAs which are stable while MAAs concentration in B antiqua is more plastic perhaps compensating its lower amounts of contitutive pigments. These patterns may reflects also specific adaptation to environmental seasonality. In fact, B. antiqua inhabiths semi and permanent ponds and must adjust photoprotection to a wide temperature gradient. B. gracilis dwells in ponds with a winter hydroperiod bearing high levels of constituve MAAs which readly provide photoprotection at a narrower temperature range. Survivorship of Boeckella antiqua and B. gracilis was found to be significantly conditioned by temperature and UV radiation. Temperatures beyond 12 ºC pose a bottle neck for both species and increase UV impact. The bioaccumulation of photoprotective compounds and survivorship of clod adapted zooplanktonic species could be used to asses the potencial effects of warming and increased UV exposure due to climate change.