Stoichiometric constraints, UVR and the response of herbivores to global change

ESTEBAN BALSEIRO; CECILIA LASPOUMADERES; MARÍA SOL SOUZA; BEATRIZ MODENUTTI

Toronto

Congreso; Conference on Biological Stoichiometry; 2015

Global change affects glacier recession, which in turn affects glacial clay load to lakes. This brings changes in lake transparency, and modifies the Light:Nutrient ratio of the lakes and consequently the C:P ratio, hence the food quality for herbivores. We took advantage of a light gradient due to glacial clay load, and test the hypothesis that stoichiometric constraints would determine the capacity of herbivores to respond to UVR generated oxidative stress. We carried out laboratory and field studies in Lake Mascardi (Patagonia, Argentina) that receives waters from glaciers of Tronador Mountain. In the light gradient we examined the change in sestonic C:P ratio analyzing how these changes in food quality and UVR drove the antioxidant response in Daphnia. In addition we explored how the glacial clay itself affected the antioxidant enzymatic activity and respiration rates. We found that along the gradient, the food quality decreases and the underwater UVR increases, so the oxidative stress. In addition, the glacial clay affected respiration, and someantioxidant enzyme activities. The interaction of these factors reduces the fitness of a high P demanding species, and changes in glacial recession rates (turbid and clear years) will modulate the overall ecological fitness of Daphnia.