Determination of seston alkalinity in natural waters

Fil: Conzonno, Víctor Hugo. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Mechanisms involved in the proliferation and distribution of phytoplankton in the Patagonian Sea, Argentina, as revealed by remote sensing studies

Studies about the mechanisms that control the dynamics of phytoplankton in terms of surface chlorophyll patches by means of remote sensing information were encouraged in the Patagonian Sea (South Atlantic Ocean). Over this sea, circulation of the Patagonian Current and Malvinas Current, originated in the Circumpolar Antarctic Current, has much to do in the distribution of algal biomass. The study confirms the existence of three ecosystems: Coastal system, Shelf waters system and Shelf break. In the former, algal blooms are detected mostly between March and August. Later, the patches move inside the shelf area, the second ecosystem, towards NNE direction from approximately August to December under the influence of the Patagonian Current to reach the Malvinas Current, which circulates along the shelf break. The third ecosystem, Malvinas system, may be divided into the Malvinas Islands, where an intense algal bloom from December to January could be verified, and the Malvinas Current that shows a high concentration of algal pigment in the same period, although evidences support the hypothesis that the latter has mainly an allochthonous character. At about 37°S–39°S and 53°W–56°W, variable position, the confluence between Malvinas Current and Brazil Current takes place. As a result, the chlorophyll that functions as a tracer indicates that the impact has the characteristics of being an elastic collision, since the Malvinas Current identity was preserved afterwards. Special events, such as the climatic conditions that prompt changes in the annual behavior of the phytoplankton distribution, are discussed.Laboratorio de Investigación de Sistemas Ecológicos y AmbientalesFacultad de Ciencias Naturales y Muse

Dissolved organic matter in Chascomús Pond (Argentina) : Influence of calcium carbonate on humic acid concentration

Water chemistry of the Chascomus Pond (Province of Buenos Aires, Argentina) was studied during a year characterized by low precipitation. Supersaturation of calcium carbonate up to a calcite saturation index of about 20 in spring and summer was observed, together with a diminution of the concentration of dissolved organic matter, in particular humic substances (HS). These results suggested an adsorption between organic matter and calcium carbonate which should influence the growth of calcium carbonate crystals. A preferential removal of higher molecular weight HS was observed by gel permeation chromatography experiments.Instituto de Limnología "Dr. Raúl A. Ringuelet"Universidad de Buenos Aire

Dissolved organic matter in Chascomús Pond (Argentina) : Influence of calcium carbonate on humic acid concentration

Water chemistry of the Chascomus Pond (Province of Buenos Aires, Argentina) was studied during a year characterized by low precipitation. Supersaturation of calcium carbonate up to a calcite saturation index of about 20 in spring and summer was observed, together with a diminution of the concentration of dissolved organic matter, in particular humic substances (HS). These results suggested an adsorption between organic matter and calcium carbonate which should influence the growth of calcium carbonate crystals. A preferential removal of higher molecular weight HS was observed by gel permeation chromatography experiments.Instituto de Limnología "Dr. Raúl A. Ringuelet"Universidad de Buenos Aire

Annual eyele and spatial heterogeneity of autotrophic and heterotrophic processes, and physicochemical features of Río Tercero Reservoir, Córdoba, Argentina

Se observaron dos períodos marcados de estratificación estival y circulación invernal, en la concentración de oxígeno, temperatura, amonio, nitratos, ortofosfatos, bacterias y actividad bacteriana heterotrófica. La actividad y biomasa fitoplanctónica tuvieron distribuciones estacionales bimodales, con dos máximos, uno en primavera—verano y otro en invierno. El porcentaje de feopigmentos al total de pigmentos fotosintéticos fue muy importante (85—90 °/o) en enero, atribuible a descomposición fotoquímica y térmica de la clorofila. Condiciones de anoxia a los 15 metros y cerca del fondo (0,50 mg O2 l—1) durante el verano, y sobresaturación en el estrato eufótico en invierno, caracterizaron al oxígeno. También en los nutrientes se manifestó una variación estacional conspicua, teniendo los nitratos y ortofosfatos máximos (44 mg NO3—NI—l-10—2 y 36 ug PO34—P I—1) a profundidades y meses en los que la fotosíntesis y biomasa algal disminuyeron; por el contrario, las concentraciones fueron detectables en primavera—verano. Las fluctuaciones de la actividad bacteriana heterotrófica concuerdan con las de la autotrófica algal y su biomasa, con coeficientes de correlación significativos en ambos casos (P< 0,01). Las dos tasas se incrementaron en febrero—marzo. El aumento en la fotosíntesis y clorofila invernal no fue acompañado por la actividad bacteriana, sí por la densidad de bacterias heterotróficas. La relación entre el potencial heterotrófico y la numerosidad de bacterias no fue significativa, teniendo estos, máximos diferentes.Two marked periods of summer stratification and winter circulation of oxygen concentration, temperature, ammonia, nitratos, orthophosphates and bacterial heterotrophic activity were recorded at the Embalse Río Tercero Reservoir. Primary production and biomass of phytoplankton showed a bimodal distribution, with two peaks, one in spring-summer, the remainder in winter. The high proportion of phaeopigments in relation to total photosynthetic pigments that was observed in January is attributed to photochemical and thermal decomposition of chlorophyll. Oxygen depletion below 15 m depth (0.50 mg O2 I x) was observed during summer as well as oversaturation in the euphotic zone during winter. Nutrients also showed a conspicuous seasonal variation. Nitrates and orthophosphates exhibited the highest values (44 mg NO3—NI—l-10—2 y 36 ug PO34—P I—1) at depths and months ¡n which algal biomass and primary production decreased, while very low values were found during spring-summer. Heterotrophic bacterial activity was highly correlated to algal biomass and primary production as well. Both rates increased in February—March. It was not observed a significant correlation between heterotrophic potential and the number of bacteria.Instituto de Limnología "Dr. Raúl A. Ringuelet

Mechanisms involved in the proliferation and distribution of phytoplankton in the Patagonian Sea, Argentina, as revealed by remote sensing studies

Studies about the mechanisms that control the dynamics of phytoplankton in terms of surface chlorophyll patches by means of remote sensing information were encouraged in the Patagonian Sea (South Atlantic Ocean). Over this sea, circulation of the Patagonian Current and Malvinas Current, originated in the Circumpolar Antarctic Current, has much to do in the distribution of algal biomass. The study confirms the existence of three ecosystems: Coastal system, Shelf waters system and Shelf break. In the former, algal blooms are detected mostly between March and August. Later, the patches move inside the shelf area, the second ecosystem, towards NNE direction from approximately August to December under the influence of the Patagonian Current to reach the Malvinas Current, which circulates along the shelf break. The third ecosystem, Malvinas system, may be divided into the Malvinas Islands, where an intense algal bloom from December to January could be verified, and the Malvinas Current that shows a high concentration of algal pigment in the same period, although evidences support the hypothesis that the latter has mainly an allochthonous character. At about 37°S–39°S and 53°W–56°W, variable position, the confluence between Malvinas Current and Brazil Current takes place. As a result, the chlorophyll that functions as a tracer indicates that the impact has the characteristics of being an elastic collision, since the Malvinas Current identity was preserved afterwards. Special events, such as the climatic conditions that prompt changes in the annual behavior of the phytoplankton distribution, are discussed.Laboratorio de Investigación de Sistemas Ecológicos y AmbientalesFacultad de Ciencias Naturales y Muse

Ciclo Anual y Heterogeneidad Espacial de Procesos Autotróficos y Heterotróficos, y Caracteres Fisicoquímicos del Embalse Río Tercero, Córdoba, Argentina

Se observaron dos períodos marcados de estratificación estival y circulación invernal, en la concentración de oxígeno, temperatura, amonio, nitratos, ortofosfatos, bacterias y actividad bacteriana heterotrófica. La actividad y biomasa fitoplanctónica tuvieron distribuciones estacionales bimodales, con dos máximos, uno en primavera—verano y otro en invierno. El porcentaje de feopigmentos al total de pigmentos fotosintéticos fue muy importante (85—90 °/o) en enero, atribuible a descomposición fotoquímica y térmica de la clorofila. Condiciones de anoxia a los 15 metros y cerca del fondo (0,50 mg O2 l—1) durante el verano, y sobresaturación en el estrato eufótico en invierno, caracterizaron al oxígeno. También en los nutrientes se manifestó una variación estacional conspicua, teniendo los nitratos y ortofosfatos máximos (44 mg NO3—NI—l-10—2 y 36 ug PO34—P I—1) a profundidades y meses en los que la fotosíntesis y biomasa algal disminuyeron; por el contrario, las concentraciones fueron detectables en primavera—verano. Las fluctuaciones de la actividad bacteriana heterotrófica concuerdan con las de la autotrófica algal y su biomasa, con coeficientes de correlación significativos en ambos casos (P< 0,01). Las dos tasas se incrementaron en febrero—marzo. El aumento en la fotosíntesis y clorofila invernal no fue acompañado por la actividad bacteriana, sí por la densidad de bacterias heterotróficas. La relación entre el potencial heterotrófico y la numerosidad de bacterias no fue significativa, teniendo estos, máximos diferentes.Two marked periods of summer stratification and winter circulation of oxygen concentration, temperature, ammonia, nitratos, orthophosphates and bacterial heterotrophic activity were recorded at the Embalse Río Tercero Reservoir. Primary production and biomass of phytoplankton showed a bimodal distribution, with two peaks, one in spring-summer, the remainder in winter. The high proportion of phaeopigments in relation to total photosynthetic pigments that was observed in January is attributed to photochemical and thermal decomposition of chlorophyll. Oxygen depletion below 15 m depth (0.50 mg O2 I x) was observed during summer as well as oversaturation in the euphotic zone during winter. Nutrients also showed a conspicuous seasonal variation. Nitrates and orthophosphates exhibited the highest values (44 mg NO3—NI—l-10—2 y 36 ug PO34—P I—1) at depths and months ¡n which algal biomass and primary production decreased, while very low values were found during spring-summer. Heterotrophic bacterial activity was highly correlated to algal biomass and primary production as well. Both rates increased in February—March. It was not observed a significant correlation between heterotrophic potential and the number of bacteria.Instituto de Limnología "Dr. Raúl A. Ringuelet

Comparison of marine and river water humic substances in a Patagonian environment (Argentina)

Structural aspects of humic substances (HSs) in marine waters of Engaño Bay (Atlantic Ocean) and water from the Chubut River (Patagonia, Argentina) were compared. The HSs were isolated, purified, and analyzed using a multiple-method approach for structural characterization: elemental analysis, nuclear magnetic resonance (13C and 1H NMR), infrared spectroscopy (FTIR), UV-visible absorption and fluorescence. Similarities between the marine and freshwater components were evaluated on the basis of N and O contents, H/C and C/N atomic ratios, infrared bands from nitrogen-containing and carboxylic groups, percentage of functional groups obtained from NMR spectra, spectral slope coefficient of absorption spectra, absorbance ratios at 250 and 365 nm (E2/E3), aromaticity, excitation–emission matrices and fluorescence quantum yield. Both the Engaño Bay and Chubut River waters have HSs that are mainly composed of fulvic acids (FAs); although they are very similar, they may be distinguished from one another. Similarities include the predominance of aliphatic carbon content (low aromatic content); however, the water bodies differed in their content of proteins and carboxylic acids. The Engaño Bay FAs have mainly an aquatic origin; although the Chubut River FAs suggest a similar aquagenic origin, there is also evidence of contributions from pedogenic FAs.Fil: Scapini, Maria del Carmen. Universidad Nacional de la Patagonia; ArgentinaFil: Conzonno, Victor Hugo. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Investigacion en Sistemas Ecologicos y Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Balzaretti, Vilma Teresa. Universidad Nacional de la Patagonia; ArgentinaFil: Fernandez Cirelli, Alicia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin