Molecular response mechanisms of copepods to UV radiation

Ultraviolet radiation (UVR) plays an important ecological role in many mountain lakes because of the high water transparency of these aquatic systems and the natural increase of UVR fluxes with elevation. In response to UVR, both negative effects, such as increased mortality and decreased reproduction, and a variety of adaptive strategies to cope with high UVR doses (e.g., avoidance, sunscreening) have been found in freshwater zooplankton, which play a key role in pelagic food webs. Responses on a molecular level, however, are barely investigated in these organisms, calling for the need to better understand UV-induced molecular processes. The goal of the proposed study is to provide insight into the role of several UV-induced molecular stress responses and defense mechanisms in freshwater copepods (crustaceans). One crucial aim is to investigate whether copepods living in aquatic environments with significant UV stress show a different or increased molecular stress response compared to copepods from ecosystems with little UV stress. During this three-year project we will examine the functional response of UV-induced stress proteins, seasonal changes in endogenous stress protein levels, depth- dependent variations and diurnal cycles of UV-induced DNA damage and radical scavenger enzymes, respectively. The proposed research will integrate field studies and in situ experiments using a range of photobiological, ecological, and molecular biological techniques (e.g., metabolic in vivo radiolabeling, western blotting, comet assay). The study will focus on the life stage-specific responses of two copepod species, Cyclops abyssorum tatricus and Acanthodiaptomus denticornis, which are predominant in many mountain lakes of the Eastern Alps, but differ in their photoprotective strategies. The proposed study will reveal more precise localization of UV-induced sublethal impairments, and the results of the project will offer new information about fundamental molecular processes. We believe that understanding UV stress and the molecular response mechanisms of alpine freshwater organisms to protect themselves from UVR is a crucial step for assessing the ecological impact of the anticipated increase in UV-B fluxes during the next decades.