Effect of volcanic eruption on nutrients, light, and phytoplankton in oligotrophic lakes.

MODENUTTI, B.E.; BALSEIRO, E.G.; ELSER, J.J.; BASTIDAS NAVARRO, M.; CUASSOLO, F.; LASPOUMADERES, C.; SOUZA, M.S.; DIAZ VILLANUEVA, V.

LIMNOLOGY AND OCEANOGRAPHY

AMER SOC LIMNOLOGY OCEANOGRAPHY

Lugar: New ; Año: 2013 vol. 58 p. 1165 - 1175

0024-3590

Volcanic eruptions that shape the earth’s surface can have major effect on ecosystems and, as naturalexperiments, can yield insights into ecological dynamics. On 04 June 2011, a mega-eruption in the Puyehuevolcanic complex (Chile) discharged massive amounts of ash and pumice. Using long-term data from five NorthAndean Patagonian lakes (Espejo, Correntoso, Nahuel Huapi, Gutie´rrez, and Mascardi) that received differinglevels of ash, we show that, in Lakes Espejo, Correntoso, and Nahuel Huapi, these inputs resulted in 1.5- to 8-foldincreases in total suspended solids, light extinction, phosphorus concentrations, and phytoplankton biomassrelative to pre-eruption conditions. Although ashes affected light scattering, the ultraviolet : photosyntheticallyactive radiation ratio remained , 0.30–0.35 in all the lakes and no changes were seen in dissolved organic carbonin the affected lakes post-eruption. Thus, no differential specific absorption of the different light wavelengthsoccurred due to ash input. The results of multiple regression analysis identified light extinction coefficient of PAR(KPAR) as the primary variable that was associated with variation in phytoplankton biomass (chlorophyll).Furthermore, incubation experiments demonstrated significant effects of photoinhibition on phytoplanktongrowth in these lakes at ambient pre-eruption light intensities. Thus, we infer that increased phytoplanktonbiomass following the eruption likely reflects nutrient (phosphorus) loading and attenuation of excessive lightintensities.