INIBIOMA   20415
INSTITUTO DE INVESTIGACIONES EN BIODIVERSIDAD Y MEDIOAMBIENTE
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Biogeochemistry of the volcanic acidic waters at the Andean Volcan Copahue (Argentina)
Autor/es:
WENDT-POTTHOFF, K.; BAFFICO, G.; KOSCHORRECK, M.
Lugar:
Colonia, Alemania
Reunión:
Congreso; Goldschmidt 2007; 2007
Resumen:
The naturally acidic water system
near the active Volcan Copahue consists of the Copahue Crater Lake, the Upper
Rio Agrio which flows into Lake Caviahue, and the Lower Rio Agrio below Lake Caviahue.
The crater lake and most of the Upper Rio Agrio are extremely acidic (pH ≈0-1.6)
with oxidizing conditions and poor colonization, mostly by wellknown acidophilic
bacteria and algae. In the lower part of the system before inflow into Lake Caviahue,
microbial biomass, oxygen penetration and oxygen consumption in the sediments were
similar to non-extreme aquatic habitats [1]. Lake Caviahue
has a pH similar to acidic pit lakes (pH 2.2 2.7), but lower iron and higher
phosphorus concentrations [2]. Sedimentation of algae is higher than in acidic
pit lakes due to different algal communities and volcanic ash input. This results
in better degradable organic carbon compounds in the sediments compared to pit
lakes. Microbial sulfate reduction proceeds in Lake Caviahue sediments at
pH<3 [3], and methanogenesis occurs in deeper layers below 25 cm. Below Lake Caviahue,
the Lower Rio Agrio is gradually diluted and neutralized by tributaries,
thereby shifting from a chemotrophic system dominated by Fe-S-Al
biogeochemistry to an organotrophic system dominated by heterotrophic processes.
Epilithic biofilms are an important habitat throughout, and we assumed that
respiration would increase with increasing pH. In contrast to this, we obtained
a minimum curve for biomass, respiration and photosynthesis with lowest values
at a site with massive mineral precipitations. This indicates that physical
stress is a more important regulatory factor for the biocoenosis than pH. We also
observed considerable interannual variations in physicochemical conditions and
high diurnal fluctuations of temperature and discharge in this part of the
river. These fluctuations may represent a stronger stress for the biota than more
acidic but stable conditions.
References
[1] Wendt-Potthoff K. and
Koschorreck M. (2002) Microb. Ecol.
43, 92-106.
[2] Pedrozo F. et
al. (2001) Hydrobiologia 452, 129-137.
[3] Koschorreck M., Wendt-Potthoff
K., and Geller W. (2003) Environ. Sci. Technol. 37, 1159-1162.