Living in transparent lakes: low food P:C decreases antioxidant response to UVR in zooplankton

BALSEIRO, E. SOUZA, S. Y MODENUTTI, B

Niza

Congreso; ASLO; 2009

Stoichiometric constraints are important in regulating organism growth and nutrient cycling in food webs. Considering the importance of C:N:P stoichiometry in protein-synthesis, UVR antioxidant enzymes would be also affected by food quality. We analyze this effect in a laboratory experiment with Daphnia commutata, examining the effect of food C:P ratio on the response of antioxidant enzymes to UVR. Neonates were reared in three different C:P ratio Chlamydomonas reinhardtii cultures, and then a subsample of each treatment exposed to ultraviolet radiation (UVA340) in order to analyze if these stoichiometric constraints limit enzymatic defenses against oxidative stress cause by UVR. After 12 days the C:P ratio of the Daphnia reared in the lowest food quality was significantly higher than that of individuals reared in good quality food. Total Glutathione S-Transferases (GST) and Catalase (CAT) showed higher activities in UVR exposed treatments, however, in all cases resulted in an inverse relationship with food C:P ratio. Thus, food quality (in terms of elemental ratios) imposes another bottleneck for zooplankton grazers, since UVR would interact with food quality affecting fitness.