Bacterioplankton responses to vertical mixing, ultraviolet radiation, nutrients and CO2 along an optical gradient in Mediterranean lakes

REDONDO-HASSELERHAM, P; CABRERIZO, M.; CARRILLO, P.; HELBLING, E. W.; VILLAFAÑE, V. E.; VILLAR-ARGAIZ , M.; MEDINA-SÁNCHEZ, J. M.

Granada

Congreso; Aquatic Sciences Meeting, Association for the Sciences of Limnology and Oceanography; 2015

ASLO

As a consequence of global change, alterations in vertical mixing patterns have been predicted for the Mediterranean Region, exposing bacterioplankton to different fluctuant radiation regimes. Furthermore, increases in nutrient availability, atmospheric CO<sub>2<sub> concentration and ultraviolet radiation fluxes (UVR) are also expected. This study analyzes the individual and interactive effects of these global change factors on heterotrophic bacterial production (BP, measured as thymidine incorporation) along an optical gradient (K<sub>320nm<sub> from <0.4 to >2 m<sup>- 1<sup>) in lakes from Southern Spain, paying special attention to patterns of photoinhibition by UVR in interaction with the other studied factors. Our results show that, in a global change scenario characterized by a mixing layer subjected to fluctuant UVR regime and augmented levels of CO<sub>2<sub> and/or nutrients, a higher photoinhibition will occur, although this effect will be attenuated in less UVRtransparent lakes. In contrast, in a global change scenario characterized by a mixing layer subjected to less fluctuant UVR regime and augmented levels of CO<sub>2<sub> and/or nutrients, photoinhibition will be attenuated, although BP will be more affected by UVR in less UVR-transparent lakes.