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

Nature Publishing Group

Año: 2017 vol. 7

Nutrient inputs andultraviolet radiation (UVR) are global factors affecting the structure andfunctioning of aquatic ecosystems, particularly clear-water ecosystems. Weperformed experiments in two model lakes highly exposed to UVR fluxes in orderto test the effect that future increases in mineral nutrients transported bydust aerosol might exert on primary producers depending on the likelihood ofatmospheric inputs. Lake La Caldera (Northern Hemisphere) has been receivingrecurrent dust inputs from the Sahara Desert while lake Los Cántaros (SouthernHemisphere) has been less affected by dust aerosol. UVR × Nutrient synergistically stimulated primary production(PP), chlorophyll a (Chl a), with a smaller increase in phytoplanktonic biomass in La Caldera, butnot in Los Cántaros, where nutrient addition unmasked the UVR inhibitory effecton phytoplankton. The proportional decrease of mixotrophic nanoflagellates(MNFs) after the nutrient pulse (in Los Cántaros) and the long-term decline ofMNFs in La Caldera associated with the increase in aerosol-dust intrusions fromthe Sahara during the last 40 years suggest that a future scenario ofintensified aerosol events from desert and desertified areas would not onlyreduce functional diversity with the decline of MNFs, but would ultimatelyalter the C flux towards the grazing chain in oligotrophic ecosystems.