Hernán Gaete

Assessment of catalase activity, lipid peroxidation, chlorophyll-a, and growth rate in the freshwater green algae Pseudokirchneriella subcapitata exposed to copper and zinc

In this work, the effect of copper and zinc on green alga Pseudokirchneriella subcapitata was evaluated through catalase activity, lipid peroxidation by TBARS essay, growth rate, and the chlorophyll-a concentration. Catalase activity increased significantly (P < 0.05) in comparison to the control at 0.1 mg L -1 copper and 0.075 mg L -1 zinc, whereas the damage to the cell membrane expressed as nmols/10 6 cell of malondialdehyde increased significantly (P < 0.05) at 0.025 mg L -1 copper and 0.1 mg L -1 zinc. On the other hand, a significant (P < 0.05) decrease in chlorophyll-a concentration was found at 0.075 mg L -1 of both metals. The results showed that catalase activity, lipid peroxidation, and chlorophyll-a concentration were more sensitive to metals than the growth rate.

Evaluación de la toxicidad de cobre en suelos a través de biomarcadores de estrés oxidativo en eisenia foetida

Copper toxicity in soil was evaluated using biomarkers of oxidative stress (catalase enzyme activity, superoxide dismutase and lipid peroxidation) in the earthworm Eisenia foetida. Agricultural topsoils from mining areas of the Aconcagua river basin were collected. Total copper concentrations were in the range of 94-959 mg kg-1, while the exchangeable copper concentrations were in the range of 46-2225 µg kg-1. Earthworms exposed to soil with exchangeable copper concentrations above 32 µg kg-1 showed an increase in catalase activity. Parameters of antioxidant activity were more sensitive than the weight change and thus can be used as appropriate biomarkers in Eisenia foetida.

Evaluación de la calidad de las aguas del estero Limache (Chile central), mediante bioindicadores y bioensayos

The water quality in the Limache stream was evaluated at five sampling stations during the pe- riod of low water flow. At each station, aquatic macroinvertebrates were collected and the following parame- ters were measured in situ: pH, conductivity, dissolved oxygen, and total dissolved solids. The biological oxy- gen demand, total phosphorus, and total nitrogen were determined in the laboratory. Water toxicity was deter- mined through toxicity bioassays with the microalga Pseudokirchrneriella subcapitata. Thirty-three macroin- vertebrate families were found and the dominant taxa were Dugessidae, Oligochaeta and Chironomidae. A significant correlation was found among the Family Biotic Index ChFBI, conductivity, and total dissolved solids (r = 0.92; p < 0.05). Species diversity was lowest, as was the growth rate of P. subcapitata, at the sta- tions with the greatest anthropogenic activity and in the discharge zone of a domestic wastewater treatment plant.

Thresholds of arsenic toxicity to Eisenia fetida in field-collected agricultural soils exposed to copper mining activities in Chile

Several previous studies highlighted the importance of using field-collected soils-and not artificially-contaminated soils-for ecotoxicity tests. However, the use of field-collected soils presents several difficulties for interpretation of results, due to the presence of various contaminants and unavoidable differences in the physicochemical properties of the tested soils. The objective of this study was to estimate thresholds of metal toxicity in topsoils of 24 agricultural areas historically contaminated by mining activities in Chile. We performed standardized earthworm reproduction tests (OECD 222 and ISO 11268-2) with Eisenia fetida. Total soil concentrations of Cu, As, Zn, and Pb were in the ranges of 82-1295 mg kg(-1), 7-41 mg kg(-1), 86-345 mg kg(-1), and 25-97 mg kg(-1), respectively. In order to differentiate between the effects of different metals, we used regression analysis between soil metal concentrations and earthworm responses, as well as between metal concentrations in earthworm tissues and earthworm responses. Based on regression analysis, we concluded that As was a metal of prime concern for Eisenia fetida in soils affected by Cu mining activities, while Cu exhibited a secondary effect. In contrast, the effects of Zn and Pb were not significant. Soil electrical conductivity was another significant contributor to reproduction toxicity in the studied soils, forcing its integration in the interpretation of the results. By using soils with electrical conductivity ≤ 0.29 dS m(-1) (which corresponds to EC50 of salt toxicity to Eisenia fetida), it was possible to isolate the effect of soil salinity on earthworm reproduction. Despite the confounding effects of Cu, it was possible to determine EC10, EC25 and EC50 values for total soil As at 8 mg kg(-1), 14 mg kg(-1) and 22 mg kg(-1), respectively, for the response of the cocoon production. However, it was not possible to determine these threshold values for juvenile production. Likewise, we were able to determine EC10, EC25 and EC50 of earthworm tissue As of 38 mg kg(-1), 47 mg kg(-1), and 57 mg kg(-1), respectively, for the response of the cocoon production. Finally, we determined the no-observed effect concentration of tissue As in E. fetida of 24 mg kg(-1). Thus, earthworm reproduction test is applicable for assessment of metal toxicity in field-collected soils with low electrical conductivity, while it might have a limited applicability in soils with high electrical conductivity because the salinity-induced toxicity will hinder the interpretation of the results.

Metales pesados y toxicidad de aguas del Río Aconcagua en Chile

The toxicity of surface waters in a zone with mining activity in the Aconcagua River was determined through growth inhibition bioassays of Pseudokirchneriella subcapitata, and correlated with heavy metal concentrations. Results show that the waters near the discharge of the mining effluent displayed toxicity during all periods of study; the molybdenum and copper concentration exceeded the norms of water quality. The correlations between the concentrations of metals and the growth rate of P. subcapitata varied in the different periods of the study; inverse and significant correlations with copper stand out in some periods.

Assessment of oxidative stress and bioaccumulation of the metals Cu, Fe, Zn, Pb, Cd in the polychaete Perinereis gualpensis from estuaries of central Chile

The estuaries of the Aconcagua and Maipo Rivers of central Chile are receptors of residues that contain metals from anthropic activities including agriculture, mining and smelters, which have different levels in the two basins. This study postulates that the exposition to metals is different in the two estuaries and that their sediments contain bioavailable chemical agents that produce oxidative stress. The aim of the study was to evaluate the effect of estuarine sediments on the polychaete Perinereis gualpensis using oxidative stress biomarkers and to determine the metal concentrations in sediments and their accumulation in P. gualpensis. Sediments and organisms were collected in December 2015 and January 2016 in the estuaries. The Catapilco estuary was used as control, since its basin has little anthropic activity. The metal concentrations of Fe Cu, Pb, Zn and Cd were determined in tissues of the organisms and in sediments. The granulometry, conductivity, redox potential, pH and organic matter in sediments were determined, as well as catalase activity and lipid peroxidation. The results show that the concentrations of metals in sediments were higher in the estuary of the Aconcagua River: Cu: 48 ± 2μgg-1; Fe: 154 ± 19mgg-1, Pb: 20 ± 3μgg-1 and Zn: 143 ± 20μgg-1. In tissues, Pb and Fe were higher in the estuary of the Maipo River, while Cd was detected only in the Catapilco River mouth. Catalase activity was greater in the estuary of the Aconcagua River and lipid peroxidation in the estuary of the Catapilco River. Significant regressions were found between biomarkers of oxidative stress and metal concentrations in tissues of P. gualpensis. In conclusion, the sediments of the studied estuaries contain bioavailable chemical agents that provoke oxidative stress in P. gualpensis, which may be a risk for the benthic communities of these ecosystems. This species is proposed to monitor metals bioavailability and oxidative stress in estuarine sediments.

MODELACIÓN DE LA DISPERSIÓN DE ANHÍDRIDO SULFUROSO EN LA COMUNA DE LA COMUNA DE PUCHUNCAVÍ UTILIZANDO EL PROGRAMA ISC3

The present work evaluates the atmospheric dispersion model ISC3 in Puchuncavi, Chile, modelling the emissions of SO 2 coming from the five stations that mak...

Efecto de la radiación ultravioleta B en la producción de polifenoles en la microalga marina Chlorella sp.

Marine algae are an important source of antioxidant compounds (phenols and polyphenols), generated as defense mechanisms against stress factors (UV radiation, temperature, herbivory). The aim of this study was to evaluate the strategy of adaptation to the effect of ultraviolet B radiation (UV-B, 280-315 nm) in the marine microalga Chlorella sp. through, the production of polyphenols and total antioxidant capacity. Chlorella sp. cultures were exposed to UV-B radiation (470 μW cm -2 ) over increasing time periods. We evaluated the total antioxidant capacity DPPH, total polyphenols, chlorophyll-a and b, and cell densities in exposed and unexposed cultures. The results indicated that UV-B caused a decrease in cell density in cultures irradiated for the first time (1st stage), with a significant increment (P < 0.05, lower than the control) in the 2nd and 3rd stages only through the 4th stage (day 7), corresponding to a dose of 16,920 J m -2 . The production of total phenols increased significantly (P < 0.05) for the IVth extract with respect to the control, confirming that the exposure to UV-B caused a reaction in the microalgae, generating higher levels of photoprotector substances. Total antioxidant capacity and total polyphenols did not show a significant correlation (R 2 = 0.72) due to the lack of specificity of the DPPH assay for this type of antioxidant, but a very similar trend was observed. Although the amounts of antioxidant compounds were not high, their synthesis corresponded to the

Daño oxidativo en la microalga Pseudokirchneriella subcapitata expuesta a aguas receptoras de un efluente minero en del Río Blanco (V Región, Chile)

In this investigation antioxidant response and toxicity of metals in receiving water effluent miner in the Blanco river in Pseudokirchneriella subcapitata was assessed. The catalase activity, lipid damage through Tbars, the growth rate of was determined. The result showed an inhibition of the growth rate of P. subcapitata which correlated with increased catalase activity and the lipid liperoxidation. These responses were correlated with the concentrations of copper and iron.