Search results for "lake"
showing 10 items of 369 documents
Zirconium and hafnium fractionation and distribution of Rare Earth Elements in neutral–alkaline waters: Case study of Lake Van hydrothermal system, T…
2021
International audience; We investigated the distribution of Zr, Hf, and rare earth elements (REE) as the sum of lanthanides plus Y in the hydrothermal system in the Lake Van area of south-eastern Turkey. This system is characterised by water with variable pH in alkaline conditions resulting from hydrothermal CO2 upraise and neoformation of calcite minerals in near equilibrium with the interacting waters. Zr, Hf, and REE determinations were carried out for aqueous phases and suspended solids in lake water and surrounding thermal springs. We found that dissolved Hf is partitioned relative to Zr during calcite formation and that such fractionation is a function of the Ca2+ activity in warm wat…
Geochemical evidence for arsenic cycling in living microbialites of a High Altitude Andean Lake (Laguna Diamante, Argentina)
2020
Arsenic is best known as an environmental toxin, but this element could also serve as a metabolic energy source to certain microorganisms. Moreover, As cycling may have driven microbial life on early Earth prior to oxygenation of the atmosphere. Still, little is known about the arsenic cycling processes occurring in the presence of microorganisms and the possible traces that could be preserved in the rock record. To advance our understanding of this we studied the geochemical proxies of microbial As metabolism in living microbialites from Laguna Diamante, a likely Precambrian ecosystem analogue (Catamarca, Argentina). In this study, we show that the coexistence of As(III) and As(V) strongly…
Erosion en milieu sableux cultivé au Niger : dynamique actuelle et passée en liaison avec la pression anthropique et les changements climatiques
2011
Sahelian ecosystems, especially those installed on sandy soils react very quickly and intensely to small climatic changes. In this semi-arid area, wind erosion which occurs mainly on cultivated millet fields and is threatening the sustainable use of land resources. Furthermore, the rapid population growth and the severe droughts of the twentieth century have had important impacts on ecosystems. To better manage this fragile environment, it is important first to understand how it works. This thesis was included in the framework of the AMMA project (African Monsoon Multidisciplinary Analyses) and was in the heart of a CORUS 2 (Coopération pour la Recherche Universitaire et Scientifique) progr…
Chara hispida beds as a sink of nitrogen: Evidence from growth, nitrogen uptake and decomposition
2007
8 pages, and tables stadistics, and figures.
Transportation of complexing agents released by pulp and paper industry: A Finnish lake case
1996
Complexing agents (EDTA, DTPA) are used to bind metal ions in pulp and paper industry. Their role will increase significantly when the total chlorine free (TCF) processes will be applied to a larger extent. EDTA and DTPA were analysed in the waters from the southern part of the Lake Saimaa (SE Finland) influenced by the effluents of three pulp and paper mills. The samples were collected at different distances from the points of emission. The results of analyses suggest that EDTA can persist in lake water and is able to propagate for considerable distances, while DTPA can be detected only in the near surroundings of the site of release. Some EDTA was found even in the sampling points that we…
Catastrophic effects of sand mining on macroinvertebrates in a large shallow lake with implications for management
2019
Sand mining is a human activity that is increasing in inland waters and has profound effects on entire aquatic ecosystems. However, current knowledge of the effects of sand mining on freshwater lake ecosystems remains limited, especially for biotic communities. Here, we investigated the responses of macroinvertebrates to indiscriminate sand mining in a large shallow lake of China. Our results indicated that sand mining significantly increased the content of suspended particulate matter, total nitrogen, total phosphorus and chlorophyll a in the water column both in the sand mining area and the area adjacent to the dredging activities. While there was significantly lower total nitrogen and th…
Comparison of thermal stratification, light attenuation and Chlorophyll-a dynamics between the ends of Lake Tanganyika
2002
Thermal structure, light attenuation, and chlorophyll-a dynamics within the upper 100 m at the northern and southern ends of Lake Tanganyika were measured from August 1995–July 1996. Pronounced variability of thermal structure in time, depth and region were observed. During the dry windy season (June–September), the water column in the south was largely isothermal down to 100 m, while in the north stratification was detectable. Subsequently, in October, cessation of winds coincided with a reestablishment and strengthening of thermal stratification in the south, and a distinct rise of a weakened thermocline in the north was accompanied by an increase in epilimnetic concentrations of dissolve…
A practical approach to improve the statistical performance of surface water monitoring networks
2019
The representativeness of aquatic ecosystem monitoring and the precision of the assessment results are of high importance when implementing the EU’s Water Framework Directive that aims to secure a good status of waterbodies in Europe. However, adapting monitoring designs to answer the objectives and allocating the sampling resources effectively are seldom practiced. Here, we present a practical solution how the sampling effort could be re-allocated without decreasing the precision and confidence of status class assignment. For demonstrating this, we used a large data set of 272 intensively monitored Finnish lake, coastal, and river waterbodies utilizing an existing framework for quantifying…
Cladosporinone, a new viriditoxin derivative from the hypersaline lake derived fungus Cladosporium cladosporioides
2015
A new cytotoxic viriditoxin derivative, cladosporinone (1), along with the known viriditoxin (2) and two viriditoxin derivatives (3 and 4) were obtained from the fungus C ladosporium cladosporioides isolated from the sediment of a hypersaline lake in Egypt. The structure of the new compound (1) was determined by 1D and 2D NMR measurements as well as by high-resolution ESIMS and electronic circular dichroism spectroscopy. All isolated compounds were studied for their cytotoxicity against the murine lymphoma cell line L5187Y and for their antibiotic activity against several pathogenic bacteria. Viriditoxin (2) was the most active compound in both bioassays. Compound 1 also exhibited strong cy…
Nitrate uptake rates in freshwater plankton: the effect of food web structure
2008
9 pages, 3 figure, 1 table