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The hydrochemical, physical-chemical, and biological dynamics were studied in the eastern waters of the gulf ofCariaco, where wind and precipitation patterns govern these processes to a significant degree. Average monthly values forboth surface and bottom waters were respectively as follows: temperature: 25.69 °C each; salinity: 35.41 and 35.75 units;density anomaly (ó-t): 23.43 and 23.84 kg/m3; oxygen concentration: 184.49 and 178.38 mmol/kg; pH: 7.98 and 7.94;nitrates: 3.18 and 4.22 μmol/L; nitrites: 0.45 and 0.60 μmol/L; ammonium: 1.25 and 1.39 μmol/L; total nitrogen: 25.28 and26.31 μmol/L. Phosphate concentrations between surface and bottom waters varied between 0.60 and 0.79 μmol/L, whereasthose of total phosphorus ranged from 2 to 170 μmol/L. Surface and bottom chlorophyll a concentrations ranged from 5.19to 4.33 mg/m3, respectively. ANOVA (P<0.05) did not reveal any significant variation between the values studied, but it didshow differences between the values for different months. Decomposition of organic matter was detected, as typified by bothoxygen utilization greater than 50 mmol/kg and denitrification (N*), which increased ammonium concentration and reducedthe pH during periods of upwelling relaxation. There was an imbalance between the maxima of chlorophyll a and those ofnutrients, which evidenced that phosphorus could be an inhibitor of phytoplankton production, especially during upwellingletup, when Readfield ratio increases from N:P = 16:1 up to N:P = 24:1.
The hydrochemical, physical-chemical, and biological dynamics were studied in the eastern waters of the gulf ofCariaco, where wind and precipitation patterns govern these processes to a significant degree. Average monthly values forboth surface and bottom waters were respectively as follows: temperature: 25.69 °C each; salinity: 35.41 and 35.75 units;density anomaly (ó-t): 23.43 and 23.84 kg/m3; oxygen concentration: 184.49 and 178.38 mmol/kg; pH: 7.98 and 7.94;nitrates: 3.18 and 4.22 μmol/L; nitrites: 0.45 and 0.60 μmol/L; ammonium: 1.25 and 1.39 μmol/L; total nitrogen: 25.28 and26.31 μmol/L. Phosphate concentrations between surface and bottom waters varied between 0.60 and 0.79 μmol/L, whereasthose of total phosphorus ranged from 2 to 170 μmol/L. Surface and bottom chlorophyll a concentrations ranged from 5.19to 4.33 mg/m3, respectively. ANOVA (P<0.05) did not reveal any significant variation between the values studied, but it didshow differences between the values for different months. Decomposition of organic matter was detected, as typified by bothoxygen utilization greater than 50 mmol/kg and denitrification (N*), which increased ammonium concentration and reducedthe pH during periods of upwelling relaxation. There was an imbalance between the maxima of chlorophyll a and those ofnutrients, which evidenced that phosphorus could be an inhibitor of phytoplankton production, especially during upwellingletup, when Readfield ratio increases from N:P = 16:1 up to N:P = 24:1.
Tolerancia a la anoxia y defensas antioxidantes en el mejillón verdeRESUMEN. Se estimó la sobrevivencia a la anoxia del mejillón verde Perna viridis después de siete días de exposición a 50 g L -1 de cadmio (Cd), seguido de un período de recuperación en el mar durante 21 días. En la glándula digestiva de los organismos experimentales se determinó los niveles de Cd acumulados, y marcadores de estrés oxidativo tales como: metalotioneínas (MT), glutatión reducido (GSH), peroxidación lipídica (TBARS) y las actividades de las enzimas catalasa (CAT), glutatión reductasa (GR) y glutatión-S-transferasa (GST). Los organismos expuestos a Cd mostraron una menor tolerancia al tratamiento anóxico, sin embargo una vez recuperados en el mar presentaron valores de sobrevivencia relativamente mayores en comparación a sus controles. Los organismos expuestos a Cd revelaron un incremento en la concentración de MT y la actividad de CAT, correlacionado al ingreso corporal de Cd. Los organismos transplantados al mar mostraron una disminución del metal acumulado, manteniendo niveles de MT incrementados. Los mejillones tratados y controles no exhibieron diferencias significativas en los marcadores de estrés oxidativo determinados (TBARS, GSH, GR y GST). El Cd acumulado posiblemente afectó algunas estrategias bioquímicas relacionadas con la tolerancia a la anoxia de P. viridis. Sin embargo, los altos niveles de MT en organismos pre-expuestos y posteriormente recuperados, podría condicionar la protección contra la toxicidad del Cd e indirectamente una mayor tolerancia a la anoxia. Palabras clave: Perna viridis, anoxia, cadmio, enzimas antioxidantes, glutatión reducido, lipoperoxidación, metalotioneínas. Anoxia tolerance and antioxidant defences in the green-lipped musselPerna viridis (Linnaeus, 1758) under acute cadmium exposure ABSTRACT. The survival to anoxia was measured from green-lipped mussel Perna viridis after of exposure to 50 µg L -1 cadmium (Cd) during seven days, followed by a recuperation period in the sea during 21 days. The levels of Cd, and oxidative stress biomarkers as metallothioneins (MT), reduced glutathione (GSH) and lipid peroxidation (TBARS), and maximal activities of catalase (CAT), glutathione reductase (GR) and glutathione-S-transferase (GST) were calculated in the digestive gland in experimental organisms. The Cd-exposed organisms showed an anoxia tolerance reduced; however, those organisms recovered in the sea showed a survival time to anoxia major in contrast to control organisms. The Cd-exposed organisms revealed a significant increase of MT and CAT correlated with Cd uptake. The Cd-preexposure and sea-transplanted mussels showed a significant reduction of metal accumulated, whereas the levels of MT was maintain heightened. Both, Cddepurated and non-depurated organisms did not exhibit significant differences among the biomarkers of oxidative stress: TBARS, GSH and enzymes tested. The uptake Cd possibly affected some biochemical mechanisms related to anoxia tolerance, however the high levels of MT in the pre...
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