Testing the mechanisms of impact of the Puyehue-Cordón Caulle mega-eruption on Patagonian lakes

ESTEBAN BALSEIRO; BEATRIZ MODENUTTI; JAMES ELSER; MARCELA BASTIDAS NAVARRO; CECILIA LASPOUMADERES; FLORENCIA CUASSOLO; MARÍA SOL SOUZA

Otsu

Congreso; 2012 ASLOAquatic Sciences Meeting: voyages of discovery; 2012

Association for the Sciences of Limnology and Oceanography (ASLO)

The recent eruption (June 2011) in the Puyehue-Cordón Caulle Volcanic Complex ejected massive amounts of ash and pumice into the surrounding Andean lakes. The event brought about increases in P concentrations, decreases in solar irradiation in the surface layers, and increased phytoplankton biomass (chlorophyll a) in the impacted lakes. To test the mechanisms of these responses, we performed a series of laboratory and outdoor experiments. First we tested the effects of nutrients in combination with ashes on chlorophyll a concentration. Then, we carried out a full factorial design of the combined effect of nutrient and different intensities of full solar radiation (including UV) and photosynthetically active radiation. The results suggest that the observed post-eruption increases in chlorophyll a were not merely a consequence of increased nutrient loading from ash inputs because also of reduced light intensity (especially ultraviolet radiation). The combined effects of ash sedimentation, nutrient consumption during the growing season, and increasing irradiance (particularly UV) are likely contributing to the observed recoveries of the lakes towards their pre-eruption conditions.