Abstract
We carried out the physicochemical characterization of extreme environments of acidic geothermal springs of the Copahue Thermal Complex, and isolated and cultivated algae used for therapeutic and medicinal purposes. Ecophysiological aspects, algal photosynthetic responses and potential toxicity of sediments were analysed. At the 15 sampling sites (pH: 2.0-6.7, conductivity: 283-3230 µS/cm, temperature: 22-60 °C), 11 Cyanobacteria species of a total of 24 algae were identified. The species richness was low with true inhabitants of highly acidic waters: Cyanidium caldarium, Euglena mutabilis, Chlamydomonas acidophila, Achnanthidium minutissimum, and Eunotia exigua, and cosmopolitan species of thermal springs: Mastigocladus laminosus, Leptolyngbia boryana and Phormidium tergestinum. All the species were well adapted to low light levels (15-55 µmol photon.m-2.s-1), and photosynthetic responses were similar to those in comparable environments. pH and temperature were important factors in algal distribution, and N:P relationship suggests that P is the limiting nutrient for algal growth. Fractions controlling P availability in the muds were those bound to organic matter, and Fe/Al oxyhydroxides. Healing muds have the ability to precipitate metals and would not be toxic. Cadmium and other potentially toxic metals were in very low concentrations and pose no risk for the human use as healing muds and bathing.
Highlights
The species richness was low with true inhabitants of highly acidic waters: Cyanidium caldarium, Euglena mutabilis, Chlamydomonas acidophila, Achnanthidium minutissimum, and Eunotia exigua, and cosmopolitan species of thermal springs: Mastigocladus laminosus, Leptolyngbia boryana and Phormidium tergestinum
La riqueza específica fue baja, con especies representativas de ambientes ácidos: Cyanidium caldarium, Euglena mutabilis, Chlamydomonas acidophila, Achnanthidium minutissimum y Eunotia exigua, y especies cosmopolitas de aguas termales: Mastigocladus laminosus, Leptolyngbia boryana y Phormidium tergestinum
Thermoacidic water bodies are extreme environments scattered on all continents and on many islands belonging to geologically active regions that have geothermal activity and low pH levels, characterized by waters that severely limit the growth of photoautotrophic organisms (Toplin et al 2008)
Summary
In each thermal environment of the CTC (Figure 1), basic in situ variables were measured and algae samples were taken from all of them. Water samples for chemical characterization were taken from Laguna Verde Oeste and Laguna de las Algas (full description in Supplementary Material). A full methodological description is given in Supplementary Material. Algae samples were taken with spatula and/or with a 10 μm pore plankton net according to the characteristics of each site (full description in Supplementary Material). Algal species were identified under a light microscope (magnification 400 and 1000×) and with specialized literature for each algal group (full description in Supplementary Material). 52 W1 the Centro Regional Universitario Bariloche (BCRU) (Universidad Nacional del Comahue, Argentina)
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