ABSTRACT
The Agrio-Caviahue is a natural stream-lake system composed of the Upper Agrio River (UAR) -Lake Caviahue-Lower Agrio River (LAR). The system has a broad pH gradient from extremely acid in the hot spring to almost neutral pH only 60 km downstream the source, and varies as a function of the distance. The aim of this study was to analyze the dynamics of the dissolved organic matter (DOM) of this extreme system. For that matter, an absorbance and fluorescence-based characterization was performed on natural water samples and hydrophobic resin DOM extracts during different seasons in nine sampling stations. Between August and December, the hydrological connectivity is maximum due to precipitation and snowmelt, respectively. During these months, the stream that exits the lake governs the chemical characteristics downstream mainly in the period of high connectivity. In contrast, in the dry season when the flow of LAR is minimum, the two major affluents of this river influence its pH and DOM features, and deliver inputs of humified DOM from the wetlands where the tributaries are born. DOM was characterized by having low absorbance. The PARAFAC analysis of the fluorescent DOM (FDOM) validated three fluorescent components in the natural samples (with humic and non-humic features), two of which were also recorded in the extracts, meaning that no additional hydrophobic components were missed under the limit of detection of the fluorometer. The unique features of Agrio-Caviahue DOM resemble those found in DOM from Yellowstone hot springs, both acid and alkaline.
ABSTRACT
Phosphorus (P) is an essential nutrient for algal growth and its increase in water bodies produces eutrophication. On the other hand, sediments play an essential role in the processes of transformation and accumulation of P in aquatic systems. pH became a major factor to control the availability of P bound sediment not only for algal utilization and the consequent eutrophication of lakes but also for P precipitation to sediment. Most studies focused on the effect of pH on P release from sediments were performed in laboratories where the pH gradient was simulated by adding hydrochloric acid solutions or sodium hydroxide. The aim of this paper is to evaluate the effect of pH on sediment P dynamics (release/uptake) in a river (River Agrio, Argentina) with a natural pH gradient (1.5-6.7) both in water and in sediments. The results obtained showed that: all chemical species analyzed in water decreased according to pH-gradient increase; pH affects sediment P retention capacity, demonstrating that P retention capacity is lower at high pH; P retention capacity is different dependent on the time of year: in fall, the average retention coefficient (R) was 41; in winter, the average R was 38; and in summer, the average R was 46. It was found that sediment P, in all the pH gradient, was controlled, mainly, by the oxyhydroxides of Fe and Al and, to a lesser extent, by the Organic Matter and not by Ca as would be expected in higher pH sediments.
Subject(s)
Geologic Sediments/chemistry , Phosphorus/chemistry , Water Pollutants, Chemical/chemistry , Hydrogen-Ion Concentration , Phosphorus/analysis , Rivers , Water Pollutants, Chemical/analysisABSTRACT
The application of trait-based approaches has become a widely applied tool to analyse community assembly processes and dynamics in phytoplankton communities. Its advantages include summarizing information of many species without losing essentials of the main driving processes. Here, we used trait-based approaches to study phytoplankton temporal succession in a subtropical reservoir. We applied a combined approach including morphological traits (i.e. volume, surface) and functional clustering of species (morphology-based functional groups (MBFG) and Reynolds' groups) and related the clustering of species with the environment. We found that this reservoir is characterized by a low richness and a bimodal distribution of phytoplankton biomass. Taxonomic and functional classifications were coincident, and the dominant species and groups biomasses were explained by the same group of variables. For instance, group X2, MBFG V and Carteria sp. biomasses were explained by: pH, Secchi disk depth, N-NH4; while group B, MBFG VI and Cyclotella ocellata biomasses were explained by stability of the water column, incident solar radiation, Secchi disk depth and N-NH4. From our results, we state that functional and taxonomic classifications are complementary rather than opposed approaches, and their specific uses depend exclusively on the aim of the study and the characteristics of the environment under evaluation. Our work is the first description of phytoplankton dynamics in a reservoir in the arid central western Argentina (Cuyo region).
Subject(s)
Environmental Monitoring , Phytoplankton/classification , Argentina , Biomass , Diatoms/classification , Diatoms/growth & development , Environment , Phytoplankton/growth & development , Seasons , Water Pollution/analysisABSTRACT
Irradiation of natural water samples with natural or artificial UVR typically results in a progressive loss of color and decreased absorbance; a process often referred to as photobleaching. In a typical photobleaching experiment, samples are exposed to a relatively constant level of artificial or natural UVR. However, under most natural situations, the vertical mixing of the water within the upper mixed layer results in strong and periodic fluctuations in UV irradiance. In this paper, we present the results of an experiment in which natural lake water was exposed to solar radiation in quartz tubes that were incubated either at fixed depths or rotating within the water column. We found differences between rotating and fixed samples in (i) photobleaching, (ii) nutrient release, and (iii) subsequent use by algae and bacteria. The evidence presented in this study demonstrated that photochemical processes might be affected by vertical water motion. The reasons for such differences remain largely unknown. Although we offer a potential explanation for such differences, our proposed mechanism is based on a post-hoc analysis of the data and should be taken solely as a working hypothesis for future research.
Subject(s)
Ultraviolet Rays , Water , Biological Assay , Organic Chemicals/radiation effects , PhotochemistryABSTRACT
La cría de salmónidos en jaulas flotantes en el embalse Alicurá es una actividad productiva que debe ser controlada a fin de minimizar sus consecuencias contaminantes y obtener una producción sostenida en el tiempo
Subject(s)
Argentina , Pollution of Lakes and Impoundments , AquacultureABSTRACT
La cría de salmónidos en jaulas flotantes en el embalse Alicurá es una actividad productiva que debe ser controlada a fin de minimizar sus consecuencias contaminantes y obtener una producción sostenida en el tiempo
Subject(s)
Aquaculture , Argentina , Pollution of Lakes and ImpoundmentsABSTRACT
Dentro del área del reservorio de AlicurA se estudiaron los efectos sobre la calidad del agua, generados por la piscicultura intensiva en jaulas flotantes que se lleva a cabo en esa zona. Se plantearon las estrategias para la diagnosis, seguimiento y reducción del impacto causado por las actividades. Se hicieron modelos para lograr armonía de crecimiento entre la piscicultura y el ambiente
Subject(s)
Water Quality , Fishes , Aquaculture , Environment , CongressABSTRACT
En este trabajo se presentan resultados del monitoreo bimestral que se realizó sobre la calidad del agua y los peces en el reservorio del Embalse Piedra del Aguila
Subject(s)
Water Quality , Fishes , Hydroelectric Energy , CongressABSTRACT
Se aguparon los reservorios en la cuenca del Río Negro de acuerdo con los mecanismos que regulan su estado trófico
Subject(s)
Eutrophication , Nutrients , Plankton , CongressABSTRACT
Los lagos y embalses reciben distintos aportes que van enriqueciendo sus aguas en un proceso que lleva a la eutroficación, lo que se traduce en una alta productividad de las algas. Todo ello trae aparejada una alteración pronunciada de la calidad del agua. El programa que se expone prevé lograr el manejo de la calidad del agua partiendo de un diagnóstico de la situación actual y la aplicación de modelos predictivos en base a carga de nutrientes, con el fin de regular los aportes antrópicos y poderlos ubicar en los niveles admisibles
