Volcanic nutrient inputs and trophic state of Lake Caviahue, Patagonia, Argentina

PEDROZO, F.; TEMPORETTI, P.; BEAMUD, G.; DIAZ, M.

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

Año: 2008 vol. 178 p. 205 - 212

0377-0273

The strategies for eutrophication control, remediation, and policy management are often defined for neutral to alkaline freshwater systems, as they are most suitable for human use. The influence of nutrients on eutrophication in a naturally-acidic lake is poorly known. The main purpose of the present work is to evaluate the significance of volcanic nutrients in the control of the trophic state of the acidic Lake Caviahue, located at North Patagonia, Argentina. Acidicwater systemswere most studied on artificial acidified lakes, such as mining lakes in Germany or pit lakes in the United States. Lake Caviahue received a very high P load (42–192 ton P/yr) and low N load (14 ton N/yr), mainly as ammoniumwith quite low N:P ratios (b1.0). The magmatic activity of the Copahue volcano represents the main natural contribution of nutrients and acidity to the Lake Caviahue. The lake is oligotrophic in terms of CHLa. Neither the transparency nor the nutrient, dissolved or particulate, contents are to date representative of the trophic state of the lake.High P loads donot imply the eutrophication of the lake.We suggest thatnitrogenand not phosphorus represents the key control nutrient in volcanically acidified lakes as TON was better related to CHLa observed (0.13–0.36 mg/m3) in the lake. The pH increased around one unit (pH 2.0–3.0) during the last five years suggesting that the lake has not yet returned to a stable state