Publications by authors named "Sergio Ribeiro Guevara"

38 Publications

Validating an Evaporative Calibrator for Gaseous Oxidized Mercury.

Sensors (Basel) 2021 Apr 3;21(7). Epub 2021 Apr 3.

Jožef Stefan International Postgraduate School, Jamova Cesta 39, 1000 Ljubljana, Slovenia.

Understanding atmospheric mercury chemistry is the key for explaining the biogeochemical cycle of mercury and for improving the predictive capability of computational models. Increased efforts are being made to ensure comparable Hg speciation measurements in the air through establishing metrological traceability. While traceability for elemental mercury has been recently set, this is by no means the case for gaseous oxidized mercury (GOM). Since a calibration unit suitable for traceable GOM calibrations based on evaporation of HgCl solution was recently developed, the purpose of our work was to extensively evaluate its performance. A highly specific and sensitive Hg radiotracer was used for validation over a wide range of concentrations. By comparing experimental and calculated values, we obtained recoveries for the calibration unit. The average recoveries ranged from 88.5% for 1178 ng m HgCl gas concentration to 39.4% for 5.90 ng m HgCl gas concentration. The losses were due to the adsorption of oxidized Hg on the inner walls of the calibrator and tubing. An adsorption isotherm was applied to estimate adsorption enthalpy (ΔH); a ΔH value of -12.33 kJ mol was obtained, suggesting exothermal adsorption. The results of the calibrator performance evaluation suggest that a newly developed calibration unit is only suitable for concentrations of HgCl higher than 1 µg m. The concentration dependence of recoveries prevents the system from being used for calibration of instruments for ambient GOM measurements. Moreover, the previously assessed uncertainty of this unit at µg m level (2.0%, k = 2) was re-evaluated by including uncertainty related to recovery and was found to be 4.1%, k = 2. Calibrator performance was also evaluated for HgBr gas calibration; the recoveries were much lower for HgBr gas than for HgCl gas even at a high HgBr gas concentration (>1 µg m). As HgBr is often used as a proxy for various atmospheric HgBr species, the suitability of the unit for such calibration must be further developed.
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http://dx.doi.org/10.3390/s21072501DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8038396PMC
April 2021

Trace elements in subantarctic false killer whale (Pseudorca crassidens) tissues, including the skin as an offshore bioindicator.

Environ Sci Pollut Res Int 2021 Jun 20;28(24):31746-31757. Epub 2021 Feb 20.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, Av. Bustillo, 8500, Bariloche, Argentina.

On a global scale, cetaceans are recognized well indicators of marine ecosystem health. Trace elements accumulate in their bodies and potentially constitute a toxicological threat. Here, the concentrations of essential Se; unknown physiological elements Br, Rb, Cs, Ni, and Sr; and pollutants arsenic, Cd, Hg, and Ag were assessed in the skin of false killer whales (Pseudorca crassidens) stranded at Estrecho de Magallanes, South America, and next, tissue comparisons and relationships between elemental concentrations in the skin and internal tissues (liver, kidney, spleen, lung, skeletal muscle, and testis) were assessed. Results showed elemental concentration variations among tissues. Selenium concentration was found to be higher in the liver 398 (75) μg g dry weight (DW) (standard deviation in parenthesis), followed by skin. Rubidium and Br concentrations were higher in testis 7.92 (0.42) and 99.1 (5.4) μg g DW, respectively, and Cs in muscle 0.36 (0.12) μg g DW, while Ni concentrations range (<0.05-0.91 μg g DW) did not show differences among tissues. Cadmium and arsenic were found to be higher in kidneys, 71.2 (17.6) and 2.54 (1.77) μg g DW, respectively, while Hg was highest in the liver 1068 (234) μg g DW. Concerning inter-tissue relationships, a positive skin-to-kidney and skin-to-muscle correlations were observed for Cs concentrations, and also Hg showed positive skin-to-spleen, skin-to-kidney, and skin-to-testis correlations, which support its use as potential offshore marine biomonitor.
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http://dx.doi.org/10.1007/s11356-021-12890-1DOI Listing
June 2021

Stranded false killer whales, Pseudorca crassidens, in Southern South America reveal potentially dangerous silver concentrations.

Mar Pollut Bull 2019 Aug 3;145:325-333. Epub 2019 Jun 3.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, Avenida Bustillo 9500, Bariloche, Argentina.

Silver (Ag) is a non-essential metal known to bioaccumulate in aquatic organisms. We determined Ag concentrations in five false killer whales stranded in South America. Silver concentrations (in dry weight basis) range as 6.62-10.78 μg g in liver, 0.008-7.41 μg g in spleen, 0.004-5.71 μg g in testis, 0.757-1.69 μg g in kidney, 0.011-0.078 μg g in lung and < 0.01-0.038 μg g in muscle, whereas in the single samples of uterus and ovary were 0.051 and 0.023 μg g; respectively. Overall, Ag concentration in liver and kidney exceeded the cetacean toxic thresholds, proposed as "unhealthy concentrations" and "critically dangerous" in liver and kidney. These results warrant further eco-toxicological studies, to examine biological effects of elevated silver levels for individuals and to assess the species' conservation status with respect to marine pollution.
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http://dx.doi.org/10.1016/j.marpolbul.2019.05.047DOI Listing
August 2019

The microbial mercury link in oligotrophic lakes: Bioaccumulation by picocyanobacteria in natural gradients of dissolved organic matter.

Chemosphere 2019 Sep 8;230:360-368. Epub 2019 May 8.

Grupo de Ecología de Sistemas Acuáticos a Escala de Paisaje, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA, UNComahue-CCT Patagonia Norte CONICET), Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina.

Andean Patagonian lakes are oligotrophic systems characterized by low dissolved organic carbon (DOC) levels and moderate to high Hg concentration that determine naturally high Hg/DOC ratios and bioavailability. In these lakes, microbial food webs are extremely important in Hg trophodynamics, being that the picophytoplankton fraction is a major entrance path of Hg into pelagic food webs. This study analyzed the bioaccumulation of Hg by the picocyanobacteria Synechococcus sp. using the radiotracer Hg and water from four Andean Patagonian lakes presenting a natural gradient of DOM concentration and quality. Hg bioaccumulation by Synechococcus was calculated as the uptake of Hg per biovolume unit (volume concentration factor VCF; pL μm). Hg uptake showed a wide variation (13 < VCF< 300 pL μm) in the natural DOC gradient tested (0.7-4 mg L; Hg/DOC ratio: 1.8-14 ng mg). The bioaccumulation of Hg in Synechococcus decreased exponentially with DOC concentration. Differences in the quality of dissolved organic matter (DOM) among lake water influenced also Hg bioaccumulation. Naturally degraded DOM, with low molecular weight/size, promoted higher Hg uptakes in Synechococcus compared to humic DOM, rich in high molecular weight/size aromatic compounds, that retained Hg in the dissolved phase. In Andean Patagonian lakes picocyanobacteria are pivotal organisms in the Hg cycling, taking dissolved Hg and transferring it to pelagic food webs, as well as fueling the benthic Hg pathway through sedimentation.
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http://dx.doi.org/10.1016/j.chemosphere.2019.04.186DOI Listing
September 2019

Zinc in an ultraoligotrophic lake food web.

Environ Sci Pollut Res Int 2018 Jun 21;25(16):15422-15435. Epub 2018 Mar 21.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, 8400, Bariloche, Argentina.

Zinc (Zn) bioaccumulation and trophic transfer were analyzed in the food web of Lake Nahuel Huapi, a deep, unpolluted ultraoligotrophic system in North Patagonia. Benthic macroinvertebrates, plankton, and native and introduced fish were collected at three sites. The effect of pyroclastic inputs on Zn levels in lacustrine food webs was assessed by studying the impact of the eruption of Puyehue-Cordón Caulle volcanic complex (PCCVC) in 2011, by performing three sampling campaigns immediately before and after the PCCVC eruption, and after 2 years of recovery of the ecosystem. Zinc trophodynamics in L. Nahuel Huapi food web was assessed using nitrogen stable isotopes (δN). There was no significant increase of Zn concentrations ([Zn]) in L. Nahuel Huapi biota after the PCCVC eruption, despite the evidence of [Zn] increase in lake water that could be associated with volcanic ash leaching. The organisms studied exhibited [Zn] above the threshold level considered for dietary deficiency, regulating Zn adequately even under a catastrophic situations like PCCVC 2011 eruption. Zinc concentrations exhibited a biodilution pattern in the lake's food web. To the best of our knowledge, present research is the first report of Zn biodilution in lacustrine systems, and the first to study Zn transfer in a freshwater food web including both pelagic and benthic compartments.
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http://dx.doi.org/10.1007/s11356-018-1725-8DOI Listing
June 2018

High status of mercury and selenium in false killer whales (Pseudorca crassidens, Owen 1846) stranded on Southern South America: A possible toxicological concern?

Chemosphere 2018 May 10;199:637-646. Epub 2018 Feb 10.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, Av E. Bustillo km 9.500, Bariloche, Argentina.

The study was carried out to determine Hg and Se concentrations in false killer whales stranded on the Estrecho de Magallanes, Chile, South America. Tissue samples of five mature specimens were analyzed (two females and three males). Mean Hg concentration in liver 1068 (234) μg g dry weight (DW) (standard deviation in parenthesis) was markedly higher than those in kidney 272 (152) μg g DW, lung 423 (325) μg g DW, spleen 725 (696) μg g DW, muscle 118 (94) μg g DW and testicle 18.0 (2.8) μg g DW. Mean Se concentration in liver, 398 (75) μg g DW, was higher than those in kidney 162 (69) μg g DW, lung 128 (84) μg g DW, spleen 268 (245) μg g DW, muscle 47 (38) μg g DW and testicle 25.4 (2.1) μg g DW. Positive correlations were found between Hg and Se molar concentrations in muscle, lung, spleen and kidney. Molar ratio of Se/Hg in liver, lung and muscle were <1, but those in kidney and testicle were markedly >1 suggesting a Se protection against Hg toxicity. In all the examined specimens Hg values exceeded the toxic thresholds defined for hepatic damage in marine mammals, with Se/Hg molar ratios below 1 implying limited protective action of Se. Generally, our results showed that individuals are carrying a significant burden, reflecting a high exposure to this toxic metal. This constitutes the first report on Hg and Se levels for a large subantarctic odontocete in South America region, providing insights into their contamination status and with information to the understanding of possible impacts on wild populations.
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http://dx.doi.org/10.1016/j.chemosphere.2018.02.046DOI Listing
May 2018

Inorganic mercury (Hg) accumulation in autotrophic and mixotrophic planktonic protists: Implications for Hg trophodynamics in ultraoligotrophic Andean Patagonian lakes.

Chemosphere 2018 May 8;199:223-231. Epub 2018 Feb 8.

Grupo de Ecología de Sistemas Acuáticos a Escala de Paisaje, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA, UNComahue-CONICET), Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina.

Microbial assemblages are typical of deep ultraoligotrophic Andean Patagonian lakes and comprise picoplankton and protists (phytoflagellates and mixotrophic ciliates), having a central role in the C cycle, primary production and in the incorporation of dissolved inorganic mercury (Hg) into lake food webs. In this study we evaluated the mechanisms of Hg incorporation in hetero- and autotrophic bacteria, in the autotrophic dinoflagellate (Gymnodinium paradoxum) and in two mixotrophic ciliates (Stentor araucanus and Ophrydium naumanni) dominating the planktonic microbial assemblage. The radioisotope Hg was used to trace the Hg incorporation in microbiota. Hg uptake was analyzed as a function of cell abundance (BCF: bioconcentration factor), cell surface (SCF: surface concentration factor) and cell volume (VCF: volume concentration factor). Overall, the results obtained showed that these organisms incorporate substantial amounts of dissolved Hg passively (adsorption) and actively (bacteria consumption or attachment), displaying different Hg internalization and therefore, varying potential for Hg transfer. Surface area and quality, and surface:volume ratio (S:V) control the passive uptake in all the organisms. Active incorporation depends on bacteria consumption in the mixotrophic ciliates, or on bacteria association to surface in the autotrophic dinoflagellate. Hg bioaccumulated by pelagic protists can be transferred to higher trophic levels through plankton and fish feeding, regenerated to the dissolved phase by excretion, and/or transferred to the sediments by particle sinking. In ultraoligotrophic Andean Patagonian lakes, picoplankton and planktonic protists are key components of lake food webs, linking the pelagic and benthic Hg pathways, and thereby playing a central role in Hg trophodynamics.
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http://dx.doi.org/10.1016/j.chemosphere.2018.02.035DOI Listing
May 2018

Mercury in a stream-lake network of Andean Patagonia (Southern Volcanic Zone): Partitioning and interaction with dissolved organic matter.

Chemosphere 2018 Apr 12;197:262-270. Epub 2018 Jan 12.

Laboratorio de Análisis por Activación Neutrónica, Comisión Nacional de Energía Atómica, Centro Atómico Bariloche, Av. Bustillo km 9.5, 8400 Bariloche, Argentina.

Lake Nahuel Huapi (NH) is a large, ultraoligotrophic deep system located in Nahuel Huapi National Park (NHNP) and collecting a major headwater network of Northwestern Patagonia (Argentina). Brazo Rincón (BR), the westernmost branch of NH, is close to the active volcanic formation Puyehue-Cordón Caulle. In BR, aquatic biota and sediments display high levels of total Hg (THg), ranging in contamination levels although it is an unpolluted region. In this survey, Hg species and fractionation were assessed in association with dissolved organic matter (DOM) in several aquatic systems draining to BR. THg varied between 16.8 and 363 ng L, with inorganic Hg (Hg) contributing up to 99.8% and methyl mercury (MeHg) up to 2.10%. DOC levels were low (0.31-1.02 mg L) resulting in high THg:DOC and reflecting in high Hg availability for binding particles (partitioning coefficient log K up to 6.03). In streams, Hg fractionation and speciation related directly with DOM terrestrial prints, indicating coupled Hg-DOM inputs from the catchment. In the lake, DOM quality and photochemical and biological processing drive Hg fractionation, speciation and vertical levels. Dissolved gaseous Hg (Hg) reached higher values in BR (up to 3.8%), particularly in upper lake layers where solar radiation enhances the photoreduction of Hg and Hg-DOM complexes. The environmental conditions in BR catchment promote Hg binding to abiotic particles and bioaccumulation and the production of Hg, features enhancing Hg mobilization among ecosystem compartments. Overall, the aquatic network studied can be considered a "natural Hg hotspot" within NHNP.
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http://dx.doi.org/10.1016/j.chemosphere.2018.01.048DOI Listing
April 2018

Bioindication of mercury, arsenic and uranium in the apple snail Pomacea canaliculata (Caenogastropoda, Ampullariidae): Bioconcentration and depuration in tissues and symbiotic corpuscles.

Chemosphere 2018 Apr 26;196:196-205. Epub 2017 Dec 26.

IHEM, CONICET, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina; Universidad Nacional de Cuyo, Facultad de Ciencias Médicas, Instituto de Fisiología, 5500 Mendoza, Argentina; Universidad Nacional de Cuyo, Facultad de Ciencias Exactas y Naturales, Departamento de Biología, 5500 Mendoza, Argentina. Electronic address:

Pomacea canaliculata is a mollusk potentially useful as a biomonitor species of freshwater quality. This work explores the ability of snail tissues and symbiotic corpuscles to bioconcentrate and depurate mercury, arsenic, and uranium. Adult snails cultured in metal-free reconstituted water were exposed for eight weeks (bioaccumulation phase) to water with Hg (2 μgL), As (10 μgL), and U (30 μgL) and then returned to the reconstituted water for other additional eight weeks (depuration phase). Elemental concentrations in digestive gland, kidney, symbiotic corpuscles and particulate excreta were determined by neutron activation analysis. The glandular symbiotic occupancy was measured by morphometric analysis. After exposure, the kidney showed the highest concentration of Hg, while the digestive gland accumulated mainly As and U. The subcellular distribution in symbiotic corpuscles was ∼71%, ∼48%, and ∼11% for U, Hg, and As, respectively. Tissue depuration between weeks 8 and 16 was variable amongst elements. At week 16, the tissue depuration of U was the highest (digestive gland = 92%; kidney = 80%), while it was lower for Hg (digestive gland = 51%; kidney = 53%). At week 16, arsenic showed a differential pattern of tissue depuration (digestive gland = 23%; kidney = 88%). The symbiotic detoxification of the three elements in excreta was fast between weeks 8 and 10 and it was slower after on. At the end of the depuration, each element distributed differentially in digestive gland and symbiotic corpuscles. Our findings show that symbiotic corpuscles, digestive gland and kidney P. canaliculata are sensitive places for biomonitoring of Hg, As and U.
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http://dx.doi.org/10.1016/j.chemosphere.2017.12.145DOI Listing
April 2018

Silver bioaccumulation in chironomid larvae as a potential source for upper trophic levels: a study case from northern Patagonia.

Environ Sci Pollut Res Int 2018 Jan 4;25(2):1921-1932. Epub 2017 Nov 4.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, 8400, Bariloche, Argentina.

Silver (Ag) is a pollutant of high concern in aquatic ecosystems, considered among the most toxic metallic ions. In lacustrine environments, contaminated sediments are a source of Ag for the food web. Chironomidae (Insecta: Diptera) are the most abundant, diverse, and representative insect groups in aquatic ecosystems. Chironomid larvae are closely associated to benthic substrates and link primary producers and secondary consumers. Given their trophic position and their life habits, these larvae can be considered the entry point for the transference of Ag, from the benthic deposit to the higher trophic levels of the food web. Previous studies in lakes from Nahuel Huapi National Park (Northern Patagonia) showed Ag enrichment over background levels (0.04-0.1 μg g dry weight) both in biota (bivalves and fish liver) and sediments from sites near human settlements. The aim of this study was to analyze the role of chironomids in the transference of Ag from the benthic reservoir of Lake Moreno Oeste to the food web. The concentration of Ag in chironomid larvae tissue ranged from 0.1 to 1.5 μg g dry weight, reaching a bioaccumulation factor up to 17 over substrates and depending on the associated substrate type, feeding habitats, larval stage, and season. The main Ag transfer to higher trophic levels by chironomids occurs in the littoral zone, mostly from larvae inhabiting submerged vegetation (Myriophyllum quitense) and sediment from vegetated zones. This study presents novel evidence of the doorway role played by chironomid larvae in Ag pathways from the sediments into food webs of freshwater ecosystems.
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http://dx.doi.org/10.1007/s11356-017-0656-0DOI Listing
January 2018

Species- and habitat-specific bioaccumulation of total mercury and methylmercury in the food web of a deep oligotrophic lake.

Sci Total Environ 2018 Jan 8;612:1311-1319. Epub 2017 Sep 8.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo 9500, 8400 Bariloche, Argentina.

Niche segregation between introduced and native fish in Lake Nahuel Huapi, a deep oligotrophic lake in Northwest Patagonia (Argentina), occurs through the consumption of different prey. Therefore, in this work we analyzed total mercury [THg] and methylmercury [MeHg] concentrations in top predator fish and in their main prey to test whether their feeding habits influence [Hg]. Results indicate that [THg] and [MeHg] varied by foraging habitat and they increased with greater percentage of benthic diet and decreased with pelagic diet in Lake Nahuel Huapi. This is consistent with the fact that the native creole perch, a mostly benthivorous feeder, which shares the highest trophic level of the food web with introduced salmonids, had higher [THg] and [MeHg] than the more pelagic feeder rainbow trout and bentho-pelagic feeder brown trout. This differential THg and MeHg bioaccumulation observed in native and introduced fish provides evidence to the hypothesis that there are two main Hg transfer pathways from the base of the food web to top predators: a pelagic pathway where Hg is transferred from water, through plankton (with Hg in inorganic species mostly), forage fish to salmonids, and a benthic pathway, as Hg is transferred from the sediments (where Hg methylation occurs mostly), through crayfish (with higher [MeHg] than plankton), to native fish, leading to one fold higher [Hg].
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http://dx.doi.org/10.1016/j.scitotenv.2017.08.260DOI Listing
January 2018

Variations in anthropogenic silver in a large Patagonian lake correlate with global shifts in photographic processing technology.

Environ Pollut 2017 Apr 10;223:685-694. Epub 2017 Feb 10.

Laboratorio de Análisis por Activación Neutrónica (LAAN), Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 Bariloche, Argentina.

At the beginning of the 21st century, digital imaging technology replaced the traditional silver-halide film photography which had implications in Ag contamination. Lake Nahuel Huapi is a popular Patagonia tourist destination impacted by municipal silver (Ag) contamination from photographic processing facilities since 1990's. Silver concentrations in a dated sediment core from the lake bottom showed a 10-fold increase above background levels in the second half of the 20th century, then a decrease. This trend corresponds well with published annual global photography industry demand for Ag, which clearly shows the evolution and replacement of the traditional silver-halide film photography by digital imaging technology. There were significant decreases in Ag concentrations in sediments, mussels and fish across the lake between 1998 and 2011. Lower trophic organisms had variable whole-body Ag concentrations, from 0.2-2.6 μg g dry weight (DW) in plankton to 0.02-3.1 μg g DW in benthic macroinvertebrates. Hepatic Ag concentrations in crayfish, mussels and predatory fish were significantly elevated relative to muscle which often have Ag concentrations below the detection limit (0.01-0.05 μg g DW). Trophodynamic analyses using δN and whole-body invertebrate and muscle Ag concentrations indicated food web biodilution trends. High sedimentation rates in conjunction with the reduction of silver waste products discharged to the lake, as a result of the change to digital image processing technologies, are resulting in unplanned but welcome remediation of the Ag contamination in Lake Nahuel Huapi.
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http://dx.doi.org/10.1016/j.envpol.2017.02.003DOI Listing
April 2017

Mercury and selenium in the food web of Lake Nahuel Huapi, Patagonia, Argentina.

Chemosphere 2017 Jan 30;166:163-173. Epub 2016 Sep 30.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo 9500, 8400 Bariloche, Argentina.

Despite located far from point sources of Hg pollution, high concentrations were recorded in plankton from the deep oligotrophic Lake Nahuel Huapi, located in North Patagonia. Native and introduced top predator fish with differing feeding habits are a valuable economic resource to the region. Hence, Hg and Se trophic interactions and pathways to these fish were assessed in the food web of this lake at three sites, using stable nitrogen and carbon isotopes. As expected based on the high THg in plankton, mercury did not biomagnify in the food web of Lake Nahuel Huapi, as most of the THg in plankton is in the inorganic form. As was observed in other aquatic systems, Se did not biomagnify either. When trophic pathways to top predator fish were analyzed, they showed that THg biomagnified in the food chains of native fish but biodiluted in the food chains of introduced salmonids. A more benthic diet, typical of native fish, resulted in higher [THg] bioaccumulation than a more pelagic or mixed diet, as in the case of introduced fish. Se:THg molar ratios were higher than 1 in all the fish species, indicating that Se might be offering a natural protection against Hg toxicity.
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http://dx.doi.org/10.1016/j.chemosphere.2016.09.085DOI Listing
January 2017

Heavy metal and trace elements in riparian vegetation and macrophytes associated with lacustrine systems in Northern Patagonia Andean Range.

Environ Sci Pollut Res Int 2016 Sep 3;23(18):17995-8009. Epub 2016 Jun 3.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, 8400, Bariloche, Argentina.

Vegetation associated with lacustrine systems in Northern Patagonia was studied for heavy metal and trace element contents, regarding their elemental contribution to these aquatic ecosystems. The research focused on native species and exotic vascular plant Salix spp. potential for absorbing heavy metals and trace elements. The native species studied were riparian Amomyrtus luma, Austrocedrus chilensis, Chusquea culeou, Desfontainia fulgens, Escallonia rubra, Gaultheria mucronata, Lomatia hirsuta, Luma apiculata, Maytenus boaria, Myrceugenia exsucca, Nothofagus antarctica, Nothofagus dombeyi, Schinus patagonicus, and Weinmannia trichosperma, and macrophytes Hydrocotyle chamaemorus, Isöetes chubutiana, Galium sp., Myriophyllum quitense, Nitella sp. (algae), Potamogeton linguatus, Ranunculus sp., and Schoenoplectus californicus. Fresh leaves were analyzed as well as leaves decomposing within the aquatic bodies, collected from lakes Futalaufquen and Rivadavia (Los Alerces National Park), and lakes Moreno and Nahuel Huapi (Nahuel Huapi National Park). The elements studied were heavy metals Ag, As, Cd, Hg, and U, major elements Ca, K, and Fe, and trace elements Ba, Br, Co, Cr, Cs, Hf, Na, Rb, Se, Sr, and Zn. Geochemical tracers La and Sm were also determined to evaluate contamination of the biological tissues by geological particulate (sediment, soil, dust) and to implement concentration corrections.
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http://dx.doi.org/10.1007/s11356-016-6811-1DOI Listing
September 2016

Hepatic and renal metallothionein concentrations in Commerson's dolphins (Cephalorhynchus commersonii) from Tierra del Fuego, South Atlantic Ocean.

Mar Pollut Bull 2016 Jul 10;108(1-2):263-7. Epub 2016 Apr 10.

Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina; Toxicología Ambiental, Instituto de Investigaciones Marinas y Costeras (IIMyC), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350, (CP 7600) Mar del Plata, Argentina.

The Commerson's dolphin is the most common endemic odontocete of subantarctic waters of Tierra del Fuego, Argentina incidentally caught in fishing nets. The species is classified as "Data Deficient" by the IUCN. Metallothioneins (MTs) are considered as suitable biomarkers for health and environmental monitoring. The aims of the study were to assess MT concentrations in the liver and kidney of bycaught specimens. Moreover, correlations with Zn, Se, Cd, Ag and Hg, and the molar ratios of MT:metals were estimated to evaluate if there is an indication of their respective protective role against metal toxicity in tissues. Hepatic and renal MT concentrations were similar, ranging from 11.6 to 29.1nmol·g(-1) WW, and Kidney/Liver ratios ranging from 0.73 to 1.93 corresponded to normal ranges. Results suggest that MTs are related to physiological ranges for the species. This information constitutes the first MT report on Commerson's dolphins and possibly considered as baseline for species' conservation.
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http://dx.doi.org/10.1016/j.marpolbul.2016.03.061DOI Listing
July 2016

Historical records of mercury in southern latitudes over 1600 years: Lake Futalaufquen, Northern Patagonia.

Sci Total Environ 2016 May 22;553:541-550. Epub 2016 Mar 22.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, 8400 Bariloche, Argentina; Instituto Balseiro, UNCu, Argentina.

Mercury is released to the environment from natural and anthropogenic sources, and through atmospheric transport is distributed globally. Lake Futalaufquen (42.8°S) is an oligotrophic lake located in Los Alerces National Park (Northern Patagonia), providing a remote and unpolluted study system. A lacustrine sedimentary sequence revealed 1600 years of Hg deposition, identifying natural baselines and marked peaks not correlated with long-range atmospheric transport. Organic matter and catchment erosion were discarded as Hg drivers. Natural background, pre-1300 CE Hg concentrations, ranged between 27 and 47 ng g(-1) (accumulation rates from 8 to 15μg m(-2) y(-1)). From 1300 CE on, the Hg background profile did not follow the generally increasing Hg pattern observed in both Southern and Northern Hemisphere since pre-industrial times. It was not until the last century that a 1.6-fold increase is observed in the Hg accumulation rate, considered among the lowest increments in southern South America. Noteworthy local/regional sources of Hg for this area, along with global transport, are forest fires and volcanic activity. Between approx. 1340 and 1510 CE, sharp increase in Hg concentration and accumulation rate (up to 204 ng g(-1) and 51 μg m(-2) y(-1), respectively) were clearly associated with extended fire episodes. Furthermore, high Hg peaks during the last 300 years were associated with volcanic eruptions in northernmost Patagonia together with fairly irregular fire episodes, caused by anthropogenic burning by settling population in the Andes.
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http://dx.doi.org/10.1016/j.scitotenv.2016.02.114DOI Listing
May 2016

Natural origin arsenic in aquatic organisms from a deep oligotrophic lake under the influence of volcanic eruptions.

Chemosphere 2016 Feb 19;144:2277-89. Epub 2015 Nov 19.

Laboratorio de Análisis por Activación Neutrónica (LAAN), Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 Bariloche, Argentina.

Volcanic eruptions are recognized sources of toxic elements to freshwater, including arsenic (As). In order to study the short term changes in the bioaccumulation of naturally occurring As by aquatic organisms in Lake Nahuel Huapi (Argentina), located close to the Puyehue-Cordón Caulle volcanic complex (PCCVC), we described As concentrations at different trophic levels and food web transfer patterns in three sites of the lake prior to the last PCCVC eruption (June 2011), and compared As concentrations in biota before and after the eruption. The highest As concentrations and greater variations both between sites and position in the water column, were observed in phytoplankton (3.9-64.8 µg g(-1) dry weight, DW) and small zooplankton (4.3-22.3 µg g(-1) DW). The pattern of As accumulation in aquatic organisms (whole body or muscle) was: primary producers (phytoplankton) > scrapper mollusks (9.3-15.3 µg g(-1) DW) > filter feeding mollusks (5.4-15.6 µg g(-1) DW) > omnivorous invertebrates (0.4-9.2 µg g(-1) DW) > zooplankton (1.2-3.5 µg g(-1) DW) > fish (0.2-1.9 µg g(-1) DW). We observed As biodilution in the whole food web, and in salmonids food chains, feeding on fish prey; but biomagnification in the food chain of creole perch, feeding on benthic crayfish. The impact of the 2011 PCCVC eruption on the As levels of biota was more evident in pelagic-associated organisms (zooplankton and planktivorous fish), but only in the short term, suggesting a brief high bioavailability of As in water after ash deposition. In benthic organisms As variations likely responded to shift in diet due to coverage of the littoral zone with ashes.
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http://dx.doi.org/10.1016/j.chemosphere.2015.10.092DOI Listing
February 2016

The skin of Commerson's dolphins (Cephalorhynchus commersonii) as a biomonitor of mercury and selenium in Subantarctic waters.

Chemosphere 2015 Nov 7;138:735-43. Epub 2015 Aug 7.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche-Comisión Nacional de Energía Atómica (CAB-CNEA), Av. E. Bustillo 9500, 8400 Bariloche, Argentina. Electronic address:

The skin of bycaught Commerson's dolphins was tested for mercury (Hg) and selenium (Se) biomonitoring in Subantarctic environments. The correlation of levels detected in the skin with those found in internal tissues - lung, liver, kidney and muscle - was assessed to evaluate how skin represents internal Hg and Se distribution for monitoring purposes. Mercury in skin had a concentration range of 0.68-3.11 μg g(-1) dry weight (DW), while Se had a higher concentration range of 74.3-124.5 μg g(-1) DW. There was no significant correlation between selenium levels in any of the analyzed tissues. Thus, the skin selenium concentration did not reflect the tissular Se levels and did not provide information for biomonitoring. The lack of correlation is explained by the biological role of Se, provided that each tissue regulates Se levels according to physiological needs. However, the skin Hg level had significant positive correlation with the levels in internal tissues (ANOVA p<0.05), particularly with that of muscle (R(2)=0.79; ANOVA p=0.0008). Thus, this correlation permits the estimation of Hg content in muscle based on the multiplication of skin biopsy levels by a factor of 1.85. Mercury bioindication using skin biopsies is a non-lethal approach that allows screening of a large number of specimens with little disturbance and makes possible an adequate sampling strategy that produces statistically valid results in populations and study areas. The correlation between Hg levels in the skin and internal tissues supports the use of the epidermis of Commerson's dolphins for Hg biomonitoring in the waters of the Subantarctic, which is a poorly studied region regarding Hg levels, sources and processes.
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http://dx.doi.org/10.1016/j.chemosphere.2015.07.026DOI Listing
November 2015

Incorporation of inorganic mercury (Hg²⁺) in pelagic food webs of ultraoligotrophic and oligotrophic lakes: the role of different plankton size fractions and species assemblages.

Sci Total Environ 2014 Oct 15;494-495:65-73. Epub 2014 Jul 15.

Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA, UNComahue-CONICET), Quintral 1250, 8400 San Carlos de Bariloche, Río Negro, Argentina.

In lake food webs, pelagic basal organisms such as bacteria and phytoplankton incorporate mercury (Hg(2+)) from the dissolved phase and pass the adsorbed and internalized Hg to higher trophic levels. This experimental investigation addresses the incorporation of dissolved Hg(2+) by four plankton fractions (picoplankton: 0.2-2.7 μm; pico+nanoplankton: 0.2-20 μm; microplankton: 20-50 μm; and mesoplankton: 50-200 μm) obtained from four Andean Patagonian lakes, using the radioisotope (197)Hg(2+). Species composition and abundance were determined in each plankton fraction. In addition, morphometric parameters such as surface and biovolume were calculated using standard geometric models. The incorporation of Hg(2+) in each plankton fraction was analyzed through three concentration factors: BCF (bioconcentration factor) as a function of cell or individual abundance, SCF (surface concentration factor) and VCF (volume concentration factor) as functions of individual exposed surface and biovolume, respectively. Overall, this investigation showed that through adsorption and internalization, pico+nanoplankton play a central role leading the incorporation of Hg(2+) in pelagic food webs of Andean lakes. Larger planktonic organisms included in the micro- and mesoplankton fractions incorporate Hg(2+) by surface adsorption, although at a lesser extent. Mixotrophic bacterivorous organisms dominate the different plankton fractions of the lakes connecting trophic levels through microbial loops (e.g., bacteria-nanoflagellates-crustaceans; bacteria-ciliates-crustaceans; endosymbiotic algae-ciliates). These bacterivorous organisms, which incorporate Hg from the dissolved phase and through their prey, appear to explain the high incorporation of Hg(2+) observed in all the plankton fractions.
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http://dx.doi.org/10.1016/j.scitotenv.2014.06.138DOI Listing
October 2014

Source and trophic transfer of mercury in plankton from an ultraoligotrophic lacustrine system (Lake Nahuel Huapi, North Patagonia).

Ecotoxicology 2014 Sep 21;23(7):1184-94. Epub 2014 May 21.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, 8400, Bariloche, Argentina.

The incorporation and trophic transfer of total and methyl mercury (THg, MeHg) were examined in three size classes of plankton (10-53, 53-200, and >200 μm size range) and a small planktivorous fish, Galaxias maculatus, from the large multi-branched Lake Nahuel Huapi (North Patagonia, Argentina). Three sites representing a large range of lake benthic-pelagic structures (based on depth and shoreline characteristics) and precipitation regimes were sampled. Nitrogen and carbon stable isotopes (δ(15)N, δ(13)C) were analyzed to assess Hg trophodynamics. Selenium concentrations were determined together with THg in order to consider its potential effect on Hg trophodynamics. High THg concentrations (0.1-255 µg g(-1) dry weight (DW)) were measured in plankton, largely in inorganic form (MeHg: 3-29 ng g(-1) DW, 0.02-7% of THg, in the two larger size classes). A trend of increasing THg concentrations, varying in two to three orders of magnitude, with decreasing plankton size was associated with precipitation measured prior to each sampling event. Passive adsorption of dissolved Hg(2+) from wet deposition and runoff is considered to be the principal Hg uptake mechanism at the base of the pelagic food web. Despite the initially high THg uptake in the smaller plankton classes, the transfer to G. maculatus, and consequently to the entire food web, is likely limited due to low proportion of MeHg to THg in plankton. Furthermore, evidence of G. maculatus with benthic feeding habits having higher impact on MeHg trophic transfer compared to the same species with more pelagic (e.g., zooplankton) feeding habits, was observed. Although there is a high THg uptake in plankton, limited amounts are incorporated in the entire food web from the pelagic compartment.
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http://dx.doi.org/10.1007/s10646-014-1260-4DOI Listing
September 2014

Influence of dissolved organic matter character on mercury incorporation by planktonic organisms: an experimental study using oligotrophic water from Patagonian lakes.

J Environ Sci (China) 2013 Oct;25(10):1980-91

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Bustillo km 9.5, 8400 Bariloche, Argentina.

Ligands present in dissolved organic matter (DOM) form complexes with inorganic divalent mercury (Hg2+) affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg2+ (the prevailing mercury species in the water column of these lakes) by the algae Cryptomonas erosa and the zooplankters Brachionus calyciflorus and Boeckella antiqua. Hg2+ accumulation was studied through laboratory experiments using natural water of four oligotrophic Patagonian lakes amended witht'97Hg2+. The bioavailability of Hg2+ was affected by the concentration and character of DOM. The entrance of Hg2+ into pelagic food webs occurs mostly through passive and active accumulation. The incorporation of Hg2+ by Cryptomonas, up to 27% of the Hg2+ amended, was found to be rapid and dominated by passive adsorption, and was greatest when low molecular weight compounds with protein-like or small phenolic signatures prevailed in the DOM. Conversely, high molecular weight compounds with a humic or fulvic signature kept Hg2+ in the dissolved phase, resulting in the lowest Hg2+ accumulation in this algae. In Brachionus and Boeckella the direct incorporation of Hg from the aqueous phase was up to 3% of the Hg2+ amended. The dietary incorporation of Hg2+ by Boeckella exceeded the direct absorption of this metal in natural water, and was remarkably similar to the Hg2+ adsorbed in their prey. Overall, DOM concentration and character affected the adsorption of Hg2+ by algae through competitive binding, while the incorporation of Hg2+ into the zooplankton was dominated by trophic or dietary transfer.
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http://dx.doi.org/10.1016/s1001-0742(12)60281-2DOI Listing
October 2013

A compilation of field surveys on gaseous elemental mercury (GEM) from contrasting environmental settings in Europe, South America, South Africa and China: separating fads from facts.

Environ Geochem Health 2014 Aug 31;36(4):713-34. Epub 2013 Dec 31.

Departamento de Ingeniería Geológica y Minera, Escuela Universitaria Politécnica de Almadén, Universidad de Castilla-La Mancha, Plaza M. Meca 1, 13400, Almadén, Spain,

Mercury is transported globally in the atmosphere mostly in gaseous elemental form (GEM, [Formula: see text]), but still few worldwide studies taking into account different and contrasted environmental settings are available in a single publication. This work presents and discusses data from Argentina, Bolivia, Bosnia and Herzegovina, Brazil, Chile, China, Croatia, Finland, Italy, Russia, South Africa, Spain, Slovenia and Venezuela. We classified the information in four groups: (1) mining districts where this contaminant poses or has posed a risk for human populations and/or ecosystems; (2) cities, where the concentration of atmospheric mercury could be higher than normal due to the burning of fossil fuels and industrial activities; (3) areas with natural emissions from volcanoes; and (4) pristine areas where no anthropogenic influence was apparent. All the surveys were performed using portable LUMEX RA-915 series atomic absorption spectrometers. The results for cities fall within a low GEM concentration range that rarely exceeds 30 ng m(-3), that is, 6.6 times lower than the restrictive ATSDR threshold (200 ng m(-3)) for chronic exposure to this pollutant. We also observed this behavior in the former mercury mining districts, where few data were above 200 ng m(-3). We noted that high concentrations of GEM are localized phenomena that fade away in short distances. However, this does not imply that they do not pose a risk for those working in close proximity to the source. This is the case of the artisanal gold miners that heat the Au-Hg amalgam to vaporize mercury. In this respect, while GEM can be truly regarded as a hazard, because of possible physical-chemical transformations into other species, it is only under these localized conditions, implying exposure to high GEM concentrations, which it becomes a direct risk for humans.
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http://dx.doi.org/10.1007/s10653-013-9591-2DOI Listing
August 2014

Differential mercury transfer in the aquatic food web of a double basined lake associated with selenium and habitat.

Sci Total Environ 2013 Jun 27;454-455:170-80. Epub 2013 Mar 27.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, 8400 Bariloche, Argentina.

Food web trophodynamics of total mercury (THg) and selenium (Se) were assessed for the double-basined ultraoligotrophic system of Lake Moreno, Patagonia. Each basin has differing proportions of littoral and pelagic habitats, thereby providing an opportunity to assess the importance of habitat (e.g. food web structure or benthic MeHg production) in the transfer of Hg and Se to top trophic fish species. Pelagic plankton, analyzed in three size classes (10-53, 53-200, and >200 μm), had very high [THg], exceeding 200 μg g(-1) dry weight (DW) in the smallest, and a low ratio of MeHg to THg (0.1 to 3%). In contrast, [THg] in littoral macroinvertebrates showed lower values (0.3 to 1.8 μg g(-1) DW). Juvenile and small fish species feeding upon plankton had higher [THg] (0.2 to 8 μg g(-1) muscle DW) compared to large piscivore fish species (0.1 to 1.6 μg g(-1) muscle DW). Selenium concentrations exhibited a much narrower variation range than THg in the food web, varying from 0.5 to 2.7 μg g(-1) DW. Molar Se:Hg ratios exceeded 1 for the majority of organisms in both basins, with most ratios exceeding 10. Using stable nitrogen isotopes as indicator of trophic level, no significant correlations were found with [THg], [Se] or Se:Hg. The apparent lack of biomagnification trends was attributed to elevated [THg] in plankton in the inorganic form mostly, as well as the possibility of consistent Se supply reducing the biomagnification in the food web of the organic portion of THg.
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http://dx.doi.org/10.1016/j.scitotenv.2013.03.008DOI Listing
June 2013

Mercury and selenium in subantarctic Commerson's dolphins (Cephalorhynchus c. commersonii).

Biol Trace Elem Res 2013 Feb 7;151(2):195-208. Epub 2012 Dec 7.

Laboratorio de Ecología, Comportamiento y Mamíferos Marinos (LECyMM), Museo Argentino de Ciencias Naturales Bernardino Rivadavia (MACN-CONICET), Buenos Aires, Argentina.

Total mercury (THg) and selenium (Se) concentrations were determined in hepatic, renal, and muscle tissues of seven specimens of Commerson's dolphins incidentally captured in artisanal fisheries of Tierra del Fuego, Argentina, by instrumental neutron activation analysis. Liver yielded the mean highest concentration of THg 9.40 (9.92) μg g(-1) dry weight (DW) (standard deviation of the average in parenthesis); kidney and muscle showed similar values, ranging from 2.34 to 3.63 μg g(-1) DW. Selenium concentrations were similar in hepatic and renal tissues, with values from 13.62 to 14.56 μg g(-1) DW; the lowest concentration was observed in muscle, 4.13 (2.05) μg g(-1) DW. Among the specimens analyzed, the maximum concentrations of THg and Se were observed in the single adult female studied. An increasing age trend is observed for THg concentrations in tissues analyzed. The molar ratio of Se/Hg in the hepatic, renal, and muscle tissues were 8.7 (9.6), 13.2 (9.5), and 9.0 (11.4), respectively, suggesting Se protection against Hg toxicity. Silver concentrations in the three tissues were included, and the Se/(Hg + 0.5×Ag) molar ratio showed values closer to 1. Both Hg and Se concentrations in liver and kidney were comparable to those found in other small odontocetes from Argentine and Brazilian waters. This study constitutes the first joint description reported of Hg and Se concentrations in liver, kidney, and muscle of the Commerson's dolphin species.
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http://dx.doi.org/10.1007/s12011-012-9555-xDOI Listing
February 2013

Heavy metals and essential elements in Commerson's dolphins (Cephalorhynchus c. commersonii) from the southwestern South Atlantic Ocean.

Environ Monit Assess 2013 Jul 11;185(7):5375-86. Epub 2012 Nov 11.

Laboratorio de Ecología, Comportamiento y Mamíferos Marinos (LECyMM), Museo Argentino de Ciencias Naturales Bernardino Rivadavia (MACN-CONICET), Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina.

A survey of the elemental contents of K, Mg, Mn, Na, Cl, Br, Cs, Co, Rb, Fe, Zn, Al, Ti, V, As, Ag, Au and Cd in liver, kidney and muscle was performed in specimens of Commerson's dolphins (Cephalorhynchus c. commersonii) from subantarctic waters. The concentrations were determined by Instrumental Neutron Activation Analysis and the specimens derives from animals incidentally caught in artisanal fishing nets. Liver had the highest concentrations of Fe, 897(79) μg g(-1) DW (dry weight) (average; standard deviation in parenthesis), kidney had the highest Cd, 35 (24) μg g(-1) DW; Cl, 9,200 (1,700) μg g(-1) DW; Na, 6,800 (1,100) μg g(-1) DW and Br, 73(12) μg g(-1) DW; and muscle the highest Mg 954 (71) μg g(-1) DW. Potassium and Cs concentrations in muscle and kidney ranged in 12,510-13,020 and 0.230-0.252 μg g(-1) DW, respectively; Zn and Mn concentrations were similar in liver and kidney (117-122.1 and 3.66-16.5 μg g(-1) DW, respectively). Silver was high in liver 5.4(5.0) μg g(-1) DW and kidney 1.2(2.7) μg g(-1) DW. Gold, Rb, Co and As had no differences among tissues. Likewise, as in other odontocete species, the concentrations of essential elements showed little variation between the specimens analyzed, since they are regulated biochemically; however, heavy metals showed high variability. This study constitutes the first large description of the elemental composition in Commerson's dolphins from subantarctic waters of the South Atlantic Ocean.
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http://dx.doi.org/10.1007/s10661-012-2952-yDOI Listing
July 2013

Influence of precipitation, landscape and hydrogeomorphic lake features on pelagic allochthonous indicators in two connected ultraoligotrophic lakes of North Patagonia.

Sci Total Environ 2012 Jun 2;427-428:219-28. Epub 2012 May 2.

Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medio Ambiente (INIBIOMA, UNComahue-CONICET), Quintral 1250, R8400FRF Bariloche, Río Negro, Argentina.

We investigated the terrestrial influence on two chained deep ultraoligotrophic lakes of North Patagonia (Argentina) through the seasonal analysis of two pelagic allochthonous indicators: i) water color, as a proxy of allochthonous dissolved organic matter in lakes; and ii) the color to chlorophyll a ratio (Color:Chla), as an indicator of the relationship between allochthonous and autochthonous carbon pools. We also evaluated the potential transfer pathways of the allochthonous dissolved organic matter into the pelagic food webs of these deep lakes, including the natural zooplankton δ(13)C in the analysis. The dynamics of the allochthonous indicators were related to the precipitation regime, water level fluctuations, and hydrogeomorphic and catchment features of lakes Moreno East and Moreno West. The water color (absorbance at 440 nm) was extremely low (<0.28 m(-1)) in both lakes regardless of the season. However, precipitation and snowmelt regimes drove the increase and decrease of water color, respectively. A significant positive relationship between the zooplankton bulk δ(13)C with the water color would suggest an input of allochthonous organic carbon into the pelagic consumers. The incorporation of the dissolved allochthonous material into higher trophic levels is likely favored by the bacterivorous behavior of planktonic organisms, mixotrophic flagellates and ciliates, which dominate the pelagic food webs of these Patagonian lakes. Morphometric aspects, mainly the higher water residence time, led to lower values of allochthony in Moreno East compared to Moreno West, probably accentuated by its upper position in the lake chain. Overall, our results suggest that these allochthonous signals can bring insight into the magnitude of the interaction between terrestrial environments and lake ecosystems, even in extremely clear and ultraoligotrophic systems, such as the Andean Patagonian lakes.
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http://dx.doi.org/10.1016/j.scitotenv.2012.03.085DOI Listing
June 2012

Bioindication of volatile elements emission by the Puyehue-Cordón Caulle (North Patagonia) volcanic event in 2011.

Chemosphere 2012 Jul 1;88(5):584-90. Epub 2012 Apr 1.

Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Av. Bustillo km 9.5, Bariloche, Argentina.

The emission of volatile pollutants from the volcanic eruption of the Puyehue-Cordón Caulle complex (North Patagonia Andean Range) that started in June 4th, 2011, was investigated by bioindication means with the epyphytic fruticose lichen Usnea sp. The elemental composition of pooled samples made up with 10 lichen thalli were analysed by Instrumental Neutron Activation Analysis. Eleven sampling sites were selected within the impacted region at different distance from the volcanic source. Five sites were selected as they were already sampled in a previous study prior to the eruption. Two other new sampling sites were selected from outside the impacted zone to provide non-impacted baseline sites. The elements associated with the lichen incorporation of particulate matter (PM) of geological origin were identified by linear correlation with a geochemical tracer (Sm concentrations). The elements associated with PM uptake were Ce, Eu, Fe, Hf, La, Lu, Na, Nd, Sb, Sc, Se, Ta, Tb, Th, U, and Yb. Arsenic and Cs concentrations showed contributions exceeding the PM fraction in sites near the volcanic centre, also higher than the baseline concentrations, which could be associated with permanent emissions from the geothermal system of the Puyehue-Cordón Caulle complex. The lichen concentrations of Ba, Ca, Co, Hg, K, Rb, Sr, and Zn were not associated with the PM, not showing higher concentrations in the sites nearby the volcanic source or respect to the baseline values either. Therefore, there is no indication of the emission of volatile forms of these elements in the lichen records. The lichen records only identified Br volatile emissions associated with the Puyehue-Cordón Caulle complex eruption in 2011.
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http://dx.doi.org/10.1016/j.chemosphere.2012.03.037DOI Listing
July 2012

Apple snails and their endosymbionts bioconcentrate heavy metals and uranium from contaminated drinking water.

Environ Sci Pollut Res Int 2012 Sep 17;19(8):3307-16. Epub 2012 Mar 17.

Laboratorio de Fisiología (IHEM-CONICET), and Departamento de Morfología y Fisiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Casilla de Correo 33, 5500 Mendoza, Argentina.

Purpose: The differential ability of apple snail tissues, endosymbionts, and eggs to bioaccumulate several metals (Sb, As, Ba, Br, Zn, Cr, Fe, Hg, Se, and U) was investigated.

Methods: Metal concentrations were determined by neutron activation analysis in several tissues, endosymbionts, and eggs from mature apple snails cultured in either drinking water or reconstituted water (prepared with American Society for Testing and Materials type I water).

Results: The highest bioconcentration factors (BCFs) in the midgut gland were found for Ba, Zn, Se, As, U, Br, and Hg (in decreasing order), while the highest in the kidney were for Ba, Br, and Hg. The foot showed the highest BCFs for Ba, Hg, Br, and Se (in decreasing order). Calcified tissues (uterus, shell) and eggs showed low BCFs, except for Ba. Both C corpuscles and gland tissue showed statistically higher BCFs than K corpuscles for Ba, Fe, U, Br, and Sb. The concentration of most of the studied elements was significantly lower in tissues and endosymbionts obtained from snails cultured in reconstituted water instead of drinking water. Snails cultured in reconstituted water and then exposed or not to Hg, As, and U (at the maximum contaminant level allowed by the US Environmental Protection Agency) also resulted in high levels accumulated in midgut gland, endosymbionts and kidney.

Conclusions: Our findings suggest that the midgut gland (and the symbionts contained therein), the kidney, and the foot of Pomacea canaliculata may be useful bioindicators of Hg, As and U pollution in freshwater bodies and that the unrestricted use of ampullariid snails as human and animal food must be considered with caution.
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http://dx.doi.org/10.1007/s11356-012-0848-6DOI Listing
September 2012

Mercury methylation and reduction potentials in marine water: An improved methodology using 197Hg radiotracer.

Appl Radiat Isot 2012 Jan 28;70(1):46-50. Epub 2011 Jul 28.

National Institute of Biology, Marine Biology Station, Fornače 41, 6330 Piran, Slovenia.

A highly sensitive laboratory methodology for simultaneous determination of methylation and reduction of spiked inorganic mercury (Hg(2+)) in marine water labelled with high specific activity radiotracer ((197)Hg prepared from enriched (196)Hg stable isotope) was developed. A conventional extraction protocol for methylmercury (CH(3)Hg(+)) was modified in order to significantly reduce the partitioning of interfering labelled Hg(2+) into the final extract, thus allowing the detection of as little as 0.1% of the Hg(2+) spike transformed to labelled CH(3)Hg(+). The efficiency of the modified CH(3)Hg(+) extraction procedure was assessed by radiolabelled CH(3)Hg(+) spikes corresponding to concentrations of methylmercury between 0.05 and 4ngL(-1). The recoveries were 73.0±6.0% and 77.5±3.9% for marine and MilliQ water, respectively. The reduction potential was assessed by purging and trapping the radiolabelled elemental Hg in a permanganate solution. The method allows detection of the reduction of as little as 0.001% of labelled Hg(2+) spiked to natural waters. To our knowledge, the optimised methodology is among the most sensitive available to study the Hg methylation and reduction potential, therefore allowing experiments to be done at spikes close to natural levels (1-10ngL(-1)).
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http://dx.doi.org/10.1016/j.apradiso.2011.07.015DOI Listing
January 2012

Mercury in an ultraoligotrophic North Patagonian Andean lake (Argentina): concentration patterns in different components of the water column.

J Environ Sci (China) 2010 ;22(8):1171-8

LAAN-CNEA, CAB, Av. Bustillo Km 9.5, 8400, Bariloche, Argentina.

The deep, ultraoligotrophic piedmont lakes of Northern Patagonia (Argentina) are located in pristine and barely impacted areas, along a wide latitudinal range. Several studies have reported moderate to high total mercury (Hg) concentrations and contrasting methylmercury (CH3Hg+) production in different lake compartments. Sources of Hg for western Patagonian terrestrial and aquatic ecosystems are still not clear; while point sources can be ruled out and atmospheric deposition is a plausible source, along with contribution from active volcanic areas of the Andes. In this investigation, we reported a noticeably seasonal, spatial (between lake branches), and vertical (between water column strata) heterogeneity in the total Hg concentrations found in the pelagic zone of Lake Moreno. Sterile water samples taken in a depth profile of the lake showed moderate to high concentrations of CH3Hg+ in autumn with a decreasing trend with depth. Our results indicated that Hg is largely allocated in the plankton fraction between 10-53 microm; which dominated within the euphotic (epilimnetic) zone of the lake due to the high densities attained by two species of the dinoflagellate Gymnodinium. The 53-200 microm planktonic size fraction (comprising rotifers, ciliates and immature stages of crustaceans) and the > 200 microm fraction (calanoid copepods and cladocerans) were found to bear strikingly lower total Hg concentrations, suggesting that the magnification of Hg at the planktonic consumer level is negligible.
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http://dx.doi.org/10.1016/s1001-0742(09)60234-5DOI Listing
January 2011
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