Gustavo Baffico

First results on the water chemistry, algae and trophic status of an Andean acidic lake system of volcanic origin in Patagonia (Lake Caviahue)

The acidic caldera lake Caviahue (Patagonia, Argentina) and its main tributaries were studied on two dates during September 1998. The main results are: The acidity of the Lake Caviahue (pH: 2.56, acidity: >5 mmol H+ l−1) is controlled by the extremely acidic Upper Rio Agrio (pH: 1.78, acidity: >20 mmol H+ l−1). The high sulphate contents of both the river and the lake can be attributed to sulphuric acid generated by the uptake of sulphurous gases in the crater lake of Copahue Volcano at approximately 2800 m a.s.l. The high concentrations of both Fe and trace metals (e.g. Cr, Ni, Zn) in Lake Caviahue originate from sulphur–acid interactions with the predominantly volcanic geology of the catchment area. The P-rich andesitic geology influences both the Upper and Lower Rio Agrio and Lake Caviahue. Both were found to have high phosphorus concentrations (300–500 μg P l−1) indicative of a high potential for eutrophication. The plankton community consisted of bacterioplankton, phytoplankton and rotifers. The phytoplankton was dominated by one green alga, Keratococcus raphidioides (>90% of total abundance) followed by a green sphaerical and Chlamydomonas sp. The total phytoplankton density was about 15 000 cells ml−1 in the upper 10 m of the water column. Rotifers were represented by one bdelloid species and their abundance was highly variable (360–4040 ind l−1) in the water columm. In the Upper and Lower Rio Agrio, the epilithic community was dominated by one chloroccocal species and two species of Ulothricales. According to trophic categories based on phytoplankton density and TP concentration, Lake Caviahue can be classified as mesotrophic/eutrophic. However, chlorophyll a concentrations observed were not in agreement with this state.

Variations in the periphytic community structure and dynamics of Lake Nahuel Huapi (Patagonia, Argentina)

Little is known about periphyton community in Patagonia and the influence that urban development has on a particular water body. Lake Nahuel Huapi is located in a National Park with little industrial or agricultural activity in the basin, but it is influenced by urban discharges from San Carlos de Bariloche, a town of 80 000 inhabitants located on its south shore. Variations in structure and dynamics of the periphyton community in Lake Nahuel Huapi were studied during 1 year, to examine the influence of urban discharges on this community. Periphyton samples were collected on the shoreline of the lake and evaluated for biomass (as chlorophyll a concentration) and cell density of the main algal groups, at sites with and without urban influence. Results indicated the major influence of pollution from urban sources on periphyton at the most impacted sites, as well as the effect of different local events at each site (degree of contamination, type of coast, wind exposure, etc.). Higher biomass and cell densities at contaminated sites were evident, but the variation of main algal groups through the year was similar in all the sites. Periphyton in Lake Nahuel Huapi proved to be an important bioindicator of urban impacts on this water body.

First record of the invasive algae Didymosphenia geminata in the Lake Nahuel Huapi: Argentina, Patagonia

Fil: Beamud, Sara Guadalupe. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion en Biodiversidad y Medioambiente; Argentina

The acidic waters of Rio Agrio and Lago Caviahue at Volcan Copahue, Argentina

Many active volcanoes are sources of highly acidic waters that originate from volatile mineral acids. Several crater Iakes and volcanic acid brines were chemically characterized (VAREKAMP et al. 200 l), showing a broad spectrum of dissolved elements, many heavy metals, and high temperatures (for more information on crater lakes and constraints in their physical and chemical properties see PASTERNACK & VAREKAMP 1997, VAREKAMP et al. 2000; for volcanoes and activities see JENSEN 2002). eopahue Volcano in Argentina has a crater lake near the summit at 2 700 m a.s.l. Ri o Agri o i s an acidic river emerging from a geothermic source below the crater lake at the flank of eopahue volcano (DE MooR et al. 2003). The 13-km Upper Ri o Agri o flows in to a glacial finger-lake, Lake eaviahue (l 600 m a. s. l.), the outflow o f which is the Lower Ri o Agri o. The system o f river stretches an d lakes ( Fig. l) shows an acidity gradient from p H O to 7 (PEDROZO et al. 200 I). The extreme chemistry along this gradient o f acidity was studied with an additional focus on microbiology and planktonic and epilithic algae.

Evaluation of native acidophilic algae species as potential indicators of polycyclic aromatic hydrocarbon (PAH) soil contamination

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that are potentially carcinogenic, are widely distributed in the environment, and accumulate in soils. The peroxydisulfate anion strategy for the remediation of PAH-contaminated soils has attracted widespread interest, despite its negative effects on soil microbial activity as a result of oxidative stress and a decrease in pH of the soil caused by the treatment. The acidification caused by the process can itself affect the growth of the normal flora, regardless of the presence of PAHs. For this reason, it is necessary to identify microorganisms that are capable of developing in acidic environments and are sensitive to the presence of PAHs. The objective of the present study was to identify native acidophilic/acid-tolerant algae isolated from the Agrio River-Lake Caviahue system, Argentina, that could possibly be used as bioindicators of soil PAH contamination. Two of the three acidophilic species assayed were identified as potential bioindicator species. Cyanidium caldarium and Euglena mutabilis were responsive to PAH contamination in the tested soils, while the response of Keratococcus rhaphidioides was dependent on the type of soil. The use of acidophilic and cosmopolitan species, such as C. caldarium and E. mutabilis, as bioindicators is a promising first step for assays of PAH contamination in soils.

Photosynthetic performance associated with phosphorus availability in mats of Didymosphenia geminata (Bacillariophyceae) from Patagonia (Argentina and Chile)

Abstract: Recently reported blooms of Didymosphenia geminata from rivers in Argentinean and Chilean Patagonia, together with non-typical blooms reported from lake systems, have the potential to alter community and ecosystem dynamics of aquatic environments in the region. In an effort to quantify key aspects of ecosystem function of D. geminata mats in Patagonia, we describe for the first time photosynthesis–irradiance (P-E) curves of this species, associated P-E parameters (R, Pmax and α) and their relationship to other functional (alkaline phosphatase activity [APA] enzyme activity and chlorophyll a) and environmental variables (soluble reactive and organic phosphorous, electrical conductivity). Mats of D. geminata from lakes and rivers representing east and west sides of the Andes from 40°S to 46°S (i.e. much of current known distribution) varied mostly in the α and Pmax parameters of P-E curves. Southern systems showed a higher α and lower Pmax parameters than more northern sites on the east slope of the cordillera. None of the P-E curves showed photoinhibition. P-E parameters for the two lakes fell within the range of values for riverine mats; although, soluble reactive P was notably higher in the lakes. We used two different statistical approaches to evaluate associations across environmental, functional or P-E parameters, finding a strong relation between APA and Pmax and a weak one between soluble reactive phosphorus, pH, dissolved organic phosphorus and functional parameters. Our results do not contradict previous observations on the importance of P availability in communities of D. geminata; although the variability in response across P-E parameters suggests a more complex mechanism of regulation than implied in the existing literature.

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

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.