DIAZ VILLANUEVA veronica
congresos y reuniones científicas
Sunlight effect changes a detritus - invertebrate interaction
ALBARIÑO, RICARDO; DÍAZ VILLANUEVA, VERÓNICA; CANHOTO, CRISTINA
Congreso; Plant Litter Processing in Freshwaters; 2008
Current ecological models describing coarse organic matter dynamics in streams do not consider direct sunlight effects on leaf litter conditioning, breakdown and transference throughout the food webs. The aim of this study was to evaluate the effects of two light intensities (shaded and unshaded) on leaf litter colonization by stream microorganisms and its resulting quality as food for a detritus consumer, the shredder Klapopteryx kuscheli. Leaf litter was conditioned for two months in an open reach of a second order stream of the Andes in Patagonia (South America) using litter bags exposed to or sheltered from direct sunlight. Leaves were used to perform laboratory experiments to test the effect of light treatment on larval consumption, growth, efficiency of food conversion (ECI) and feeding preference for leaf litter treatments. Leaf litter of the unshaded treatment had three times more Chl-a than those of the shaded treatment (t-test, p=0.0006), 50% less fungi biomass (t-test, p=0.014) and no differences in bacterial abundance (t-test, p=0.573). Although larvae did not prefer any food (t-test, p=0.535) and fed at the same rate on both leaf litter treatments (t-test, p=0.554), they attained a two-fold growth rate (twelve days experiment; t-test, p=0.020) and ECI (t-test, p=0.004) on the shade-conditioned food resource. Our study emphasizes the importance of considering sunlight incidence in detritus-based food webs as sunlight may alter pathways of matter and energy transference. Riparian modification induced by human activities in forested catchments increases the potential for sunlight effects on detritus dynamics.