Chimeneas hydrotermales y las ciudades perdidas abisales

In the deepest areas of the ocean, thousands of meters below the photic depth, hydrothermal fields  rises their impresive gothic-like structures. These phantasmagoric landscapes host an unexpected biological diversity, well-adapted to live in such extreme environments. The biological communities living in these abissal oasis are supported by the tireless productive activity of bacteria and archea, and some scientific evidences point out that life could have its origin within these habitats. Let’s venture deeper into these incredible ecosystems.En las zonas más profundas del océano, a miles de metros por debajo de las capas de agua iluminadas por el sol, levantan sus impresionantes estructuras góticas las surgencias hidrotermales. El paisaje fantasmagórico que dibujan alberga una sorprendente diversidad biológica, adaptada a la vida en estos ambientes extremos. Las comunidades que habitan estos oasis del abismo están soportadas por la incansable actividad productiva de bacterias y arqueas, y algunas evidencias apuntan a que la vida pudo comenzar en estos crisoles. Adentrémonos un poco más en estos increíbles ecosistemas

Temporal and spatial variations in the quality of water in El Gergal Reservior, Seville, Spain

It is often difficult to define ‘water quality’ with any degree of precision. One approach is that suggested by Battarbee (1997) and is based on the extent to which individual lakes have changed compared with their natural ‘baseline’ status. Defining the base-line status of artificial lakes and reservoirs however, is, very difficult. In ecological terms, the definition of quality must include some consideration of their functional characteristics and the extent to which these characteristics are self-sustaining. The challenge of managing lakes in a sustainable way is particularly acute in semi-arid, Mediterranean countries. Here the quality of the water is strongly influenced by the unpredictability of the rainfall as well as year-to-year variations in the seasonal averages. Wise management requires profound knowledge of how these systems function. Thus a holistic approach must be adopted and the factors influencing the seasonal dynamics of the lakes quantified over a range of spatial and temporal scales. In this article, the authors describe some of the ways in which both long-term and short-term changes in the weather have influenced the seasonal and spatial dynamics of phytoplankton in El Gergal, a water supply reservoir situated in the south of Spain. The quality of the water stored in this reservoir is typically very good but surface blooms of algae commonly appear during warm, calm periods when the water level is low. El Gergal reservoir is managed by the Empresa Municipal de Abastecimiento y Saneamiento (EMASESA) and supplies water for domestic, commercial and industrial use to an area which includes the city of Seville and twelve of its surrounding towns (ca. 1.3 million inhabitants). El Gergal is the last of two reservoirs in a chain of four situated in the Rivera de Huelva basin, a tributary of the Guadalquivir river. It was commissioned by EMASESA in 1979 and since then the company has monitored its main limnological parameters on, at least, a monthly basis and used this information to improve the management of the reservoir. As a consequence of these intensive studies the physical, chemical and biological information acquired during this period makes the El Gergal database one of the most complete in Spain. In this article the authors focus on three ‘weather-related’ effects that have had a significant impact on the composition and distribution of phytoplankton in El Gergal: (i) the changes associated with severe droughts; (ii) the spatial variations produced by short-term changes in the weather; (iii) the impact of water transfers on the seasonal dynamics of the dinoflagellate Ceratium

Primer C-Hydrochange workshop sobre métodos y técnicas de medida de flujos de CO2 y CH4 en lagos y embalses

La distribución de la reservas de carbono (C) entre compartimentos del Sistema Tierra constituye uno de los principales temasde estudio de la biogeoquímica moderna. Lagos y embalses des-empeñan un papel importante en los intercambios globales de Cmediante la regulación del transporte de este elemento desde loscontinentes hasta los océanos. [...

Hydraulic management drives heat budgets and temperature trends in a Mediterranean reservoir

By contrast to the more regular and predictable temperate lakes, heat budgets and temperature dynamics in Mediterranean reservoirs are characterized by a marked interannual variability. In the present paper, the heat content, annual Birgean heat budget (ABHB), and thermal structure of Sau Reservoir were examined during a period of hypolimnetic withdrawal between 1980 and 1985, and during a period of withdrawal at intermediate depths between 1996 and 2003. The two study periods were also characterized by a wide range of stored water volume fluctuations. Results were used to develop and validate an empirical model to predict annual and monthly heat dynamics statistics and mixed layer depth as a function of hydraulic management parameters such as water volume and selective withdrawal depth. During the hypolimnetic withdrawal period elevated ABHB and deep mixed layer depths were recorded in the reservoir, which behaved as a heat trap. By contrast, intermediate depth withdrawal promoted a shallower and more stable thermocline, thus increasing the cold hypolimnetic water volume and decreasing heat content and ABHB. The study reveals that hydraulic management constitutes the main driver of the heat and thermal dynamics in reservoirs with multiple withdrawal outlets. By contrast with the increasing temperature trends recorded in many natural lakes, the hydraulic management in Sau Reservoir induced a progressive reduction in water temperature and heat content in the system, thus partially counteracting the possible deleterious effects of global warming. Our intensive study in a single, highly‐dynamic ecosystem constitutes a new approximation to the study of thermal structure and heat dynamics in water bodies

Nutrient fluxes through boundaries in the hypolimnion of Sau reservoir : expected patterns and unanticipated processes

By contrast to many natural lakes, the summer hypolimnion in advection-dominated systems like canyon-shaped reservoirs is not isolated from direct inputs from the river. This has important implications in the evolution of limnological features of the hypolimnion through the stratified period, especially if the river water directly plunges as a density current into the hypolimnion as a consequence of temperature differences. Taking the Sau Reservoir (Spain) as a prototype for this kind of systems, we present data from 11 years of monitoring to show how the river water entering the reservoir during summer is the main factor determining hypolimnetic nutrient concentrations. The empirical regression approach used all through the paper also stressed the effect of the improvement in water quality experienced by the river during the studied period on the improvement of the water quality stored in the summer hypolimnion of the reservoir. Since the change in river water quality was the consequence of the implementation of remediation measures at the basin scale, we advocate these solutions to manage reservoir eutrophication problems in this type of systems, which, in addition, had other unexpected benefits for the hypolimnetic water quality in Sau Reservoir.A diferencia de muchos lagos naturales, el hipolimnion que se forma en verano en sistemas dominados por la advección, como los embalses que inundan valles profundos y estrechos, no está aislado de las entradas directas desde el río. Esto tiene importantes implicaciones en la evolución de las características limnológicas del hipolimnion durante el periodo de estratificación, especialmente si el agua del río entra al embalse como una corriente de densidad directamente en el hipolimnion debido a diferencias de temperatura. Tomando el Embalse de Sau (España) como prototipo de este tipo de sistemas, mostramos 11 años de datos de un programa de monitoreo para ejemplificar cómo el agua del río que entra en verano al embalse es el factor determinante de la concentración de nutrientes en el hipolimnion. La aproximación de regresión empírica utilizada en el artículo también puso de manifiesto el efecto de la mejora en la calidad del agua que sufrió el río durante el periodo de estudio en la mejora del agua del agua embalsada en el hipolimnion. Ya que esta mejora en el río fue consecuencia de la implementación de medidas de restauración a nivel de la cuenca, promovemos estas soluciones para la gestión de problemas de eutrofización en este tipo de sistemas, que por otra parte mostraron ventajas inesperadas en el caso del hipolimnion del Embalse de Sau

High-resolution automatic water quality monitoring systems applied to catchment and reservoir monitoring

Automatic recording instruments provide the ideal means of recording the responses of rivers, lakes and reservoirs to short-term changes in theweather. As part of the project ‘Using Automatic Monitoring and DynamicModelling for the Active Management of Lakes and Reservoirs’ (LIFE98ENV/UK/000607), a family of three automatic monitoring stations weredesigned by engineers at the Centre for Ecology and Hydrology inWindermere to monitor such responses. In this article, we describe thisinstrument network in some detail and present case studies that illustratethe value of high resolution automatic monitoring in both catchment andreservoir applications