Vulnerability of mixotrophic algae to nutrient pulses and UVR in an oligotrophic Southern and Northern Hemisphere lake

CARRILLO, P.; MEDINA-SÁNCHEZ, J. M.; VILLAR-ARGAIZ, M.; BULLEJOS, F. J.; DURÁN, C.; BASTIDAS-NAVARRO, M.; SOUZA, M. S.; BALSEIRO, E. G.; MODENUTTI, B. E.

Scientific Reports

Springer NAture

Año: 2017 vol. 7

Nutrient inputs and ultraviolet radiation (UVR) are global factors affecting the structure and functioningof aquatic ecosystems, particularly clear-water ecosystems. We performed experiments in twomodel lakes highly exposed to UVR fluxes in order to test the effect that future increases in mineralnutrients transported by dust aerosol might exert on primary producers depending on the likelihoodof atmospheric inputs. Lake La Caldera (Northern Hemisphere) has been receiving recurrent dustinputs from the Sahara Desert while lake Los Cántaros (Southern Hemisphere) has been less affectedby dust aerosol. UVR × Nutrient synergistically stimulated primary production (PP), chlorophyll a (Chla), with a smaller increase in phytoplanktonic biomass in La Caldera, but not in Los Cántaros, wherenutrient addition unmasked the UVR inhibitory effect on phytoplankton. The proportional decrease ofmixotrophic nanoflagellates (MNFs) after the nutrient pulse (in Los Cántaros) and the long-term declineof MNFs in La Caldera associated with the increase in aerosol-dust intrusions from the Sahara duringthe last 40 years suggest that a future scenario of intensified aerosol events from desert and desertifiedareas would not only reduce functional diversity with the decline of MNFs, but would ultimately alterthe C flux towards the grazing chain in oligotrophic ecosystems.