Lake Caviahue: an extreme environment as a potential sentinel for nutrient deposition in Patagonia

Abstract

The objective of this study was to determine if extreme acidic Lake Caviahue could be used as a sentinel of atmospheric deposition hypothesizing that the physiological state of algae will be the indicator parameter. The lake was sampled from 2000 to 2015 in order to determine chlorophyll concentration, algae abundance and phytoplankton in vivo fluorescence as a way to evaluate the physiological state of algae. Development and physiological state of phytoplankton in different seasons was related to concentration and dynamics of nutrients in the lake. Laboratory experiments of Keratococcus rhaphidiodes to nitrogen (N) enrichment confirmed that an increase in nutrient content enabled a better physiological state of algae (e.g. higher chlorophyll per cell). Therefore, under the projected scenarios of climate change, the increase of available N through the increase in deposition and the increase of dissolved inorganic carbon, as consequence of higher atmospheric CO2, will compensate the natural nutrient constraints observed in the phytoplankton of the lake. The effect that the atmospheric CO2 has on the DIC, and this on algal development, as well as the influence that N has on algal growth, make Lake Caviahue an interesting sentinel of nutrient deposition at regional level.