MODENUTTI Beatriz Estela
Resource versus consumer regulation of phytoplankton: testing the role of UVR in a Southern and Northern hemisphere lake
VILLAR-ARGAIZ, M.; BALSEIRO, E. G.; MODENUTTI, B. E.; SOUZA, M. S.; BULLEJOS, F. J.; MEDINA-S?NCHEZ, J. M.; CARRILLO, P.
Lugar: Berlin; Año: 2017
Models predict thatphytoplankton is bottom- up regulated by resources and top-down controlled byconsumers. However, how the strength of these controls varies with UV radiation(UVR) is not well known. In this study, we test the hypothesis that the phosphorus(P) content of phytoplankton affects the role that UVR exerts strengthening orweakening the resource and consumer control on distinct stoichiometric andfunctional phytoplankton traits. To accomplish this, we coupled field meso- andmicrocosms in a split-plot design using UVR treatments at the plot level andnutrients and zooplankton (presence/ absence) at the subplot level, in twomountain lakes characterized by their P-sufficient (La Caldera) and P-deficientphytoplankton (Los Ca´ntaros). We found that the addition of nutrientsdecreased phytoplankton C:P in both lakes, but enhanced primary production andchlorophyll a only under UVR in La Caldera. Also, theeffects of zooplankton on phytoplankton varied between lakes and UVRconditions, and increased primary production and chlorophyll a under UVR in La Caldera, but not in Los Ca´ntaros.These results suggest that differences in the stoichiometric aspects associatedwith the P content in phytoplankton play a key role in how UVR affects resourceand consumer controls, with much weaker effects in P-deficient food webs.