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Floodplain Lakes (floodplain + lake)
Selected AbstractsSpatial variation of metals and acid volatile sulfide in floodplain lake sedimentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2003Corine van Griethuysena Abstract In risk assessment of aquatic sediments, much attention is paid to the immobilizing effect of acid volatile sulfide (AVS) on trace metals. The difference of AVS and simultaneously extracted metals (SEM) gives an indication of metal availability. In floodplain sediments, where changing redox conditions occur. AVS may play a major role in determining variation in metal availability. The importance of spatial heterogeneity has been recognized in risk assessment of trace-metal-polluted sediments. However, little is known about spatial variation of available metal fractions. We studied spatial variability of sediment, environmental conditions, total contaminant concentrations, and available metals (as SEM-AVS or SEM-AVS/fOC) in a floodplain lake. The top 5 cm of sediment was sampled at 43 locations. Data were analyzed with correlation and principal component analysis as well as with geostatistical methods. Trace metal and SEM concentrations and most sediment characteristics were more or less constant within 10%. In contrast, AVS concentrations were much more variable and showed a strong spatial dependence due to differences in lake depth, total sulfur pools, and redox potential (Eh), which resulted in crucial differences in trace-metal availability within the lake. The spatial pattern of SEM-AVS deviates from total or normalized trace-metal patterns. This particularly has implications for risk assessment of sediments prone to dynamic hydrological conditions, where AVS concentrations are also variable in time. [source] Effect of Campsurus notatus on NH+4, DOC Fluxes, O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment-Water Interface of an Amazonian Lake Impacted by Bauxite TailingsINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2003João José Fonseca Leal Abstract The aim of this study was to evaluate the influence of Campusurus notatusEaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH4+) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment-water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment-water interface. The cores were incubated with 0 to 2,388 ind m,2 of Campsurus notatus nymphs, and the changes in NH4+, DOC, O2 concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p < 0.05, multiple regression) and oxygen uptake (F = 11.8, p < 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two-way ANOVA, p < 0.05) in bacterial production (0.44 ,g C l,1 h,1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH4+) at the sediment-water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production. [source] Lake age and water level affect the turbidity of floodplain lakes along the lower RhineFRESHWATER BIOLOGY, Issue 3 2003F. C. J. M. Roozen SUMMARY 1. We sampled a set of 93 lakes situated in the floodplains of the lower River Rhine in search for morphometric and other factors that explain their variation in clarity. 2. Lakes with a drop in summer water level were less turbid at the time of sampling, mainly because of a lower concentration of inorganic suspended solids (ISS). 3. We also found that older lakes were more turbid than younger lakes and that this was largely because of an increase in phytoplankton. 4. Water clarity was positively related to lake depth and the presence of vegetation. 5. Model calculations indicated that the underwater light climate was strongly affected by chlorophyll and ISS, the latter being the dominant factor affecting Secchi depth. Dissolved organic carbon (DOC) was less important. 6. The high concentration of ISS suggests that intensive resuspension occurs in most of the lakes. Using a simple wave model, and assuming that vegetation protects sediments against resuspension, we could eliminate wind resuspension as an important process in 90% of the lakes, leaving resuspension by benthivorous fish as probably the most important factor determining transparency. 7. Chlorophyll a concentration showed a strong positive correlation to ISS concentration, suggesting that resuspension may also have a positive effect on phytoplankton biomass in these lakes. 8. In conclusion, in-lake processes, rather than river dynamics, seem to be driving the turbidity of floodplain lakes along the lower River Rhine. [source] The riverscape of Western Amazonia , a quantitative approach to the fluvial biogeography of the regionJOURNAL OF BIOGEOGRAPHY, Issue 8 2007Tuuli Toivonen Abstract Aim, To provide a quantitative spatial analysis of the riverscape (open-water bodies and their surrounding areas) of the Western Amazonian lowlands using a consistent surface of remotely sensed imagery. Taking into account the essential significance of fluvial environments for the Amazonian biota, we propose that an enhanced understanding of the Amazonian riverscape will provide new insight for biogeographical studies in the region and contribute to the understanding of these megadiverse tropical lowlands. Location, An area of 2.2 million km2 covering the Western Amazonian lowlands of the Andean foreland region, i.e. the upper reaches of the Amazon river system. Areas in Colombia, Venezuela, Ecuador, Peru, Brazil and Bolivia between longitudes 83 °W and 65 °W and latitudes 5 °N and 12 °S are included. Methods, A mosaic of 120 Landsat TM satellite images was created with 100-m resolution, and water areas of over 1 ha in size or c. 60 m in width were extracted using a simple ratio threshold applicable to a large set of data. With this method, 99.1% of the water areas present in 30-m imagery were mapped with images with 100-m resolution. Water pixels of distinct river segments were assigned to river classes on the basis of their channel properties, and islands and lakes were distinguished separately and classified. Measures of water patterns such as structure, composition, richness and remoteness were provided for various spatial units. Riverine corridors were computed from the open-water mask by outer limits of active channels and floodplain lakes. Analytical results are shown as both thematic maps and statistics. Results, A total of 1.1% of Western Amazonia is covered by open-water bodies over 1 ha in size or 60 m in width. River-bound waters comprise 98% of the total water surface. Whilst isolated lakes are scarce, river-bound oxbow and backchannel lakes are plentiful, comprising 17.5% of all waters. They are particularly frequent along meandering channels, which dominate both in area and length. The riverine corridors including active channels and floodplain lakes cover 17% of the land area. The average distance from any point of land to the nearest water is 12 km. Geographically speaking, the distribution of waters is uneven across the region, and the detailed characteristics of the riverscape are geographically highly variable. Three major, fluvially distinct regions can be identified: central Western Amazonia, the south, and the north-east. The proportional surface areas of the riverine corridors, numbers of lakes, sizes of islands and their distributions depend largely on the types and sizes of the rivers. Main conclusions, Our results support the notion of Western Amazonia as a dynamic, highly fluvial environment, highlighting and quantifying considerable internal variation within the region in terms of fluvial patterns and the processes that they reflect and control. Biogeographically, the variety of types of fluvial environments and their characteristics are important constituents of what influences the distribution of species and dynamics of terrestrial habitats. Spatially consistent riverscape data can serve as a consistent and scalable source of relevant information for other biogeographical approaches in the region. [source] On the occurrence of the Asiatic cyprinid Pseudorasbora parva in the NetherlandsJOURNAL OF FISH BIOLOGY, Issue 5 2006B. J. A. Pollux A large scale inventory along the Meuse River (the Netherlands), showed that floodplain lakes function as spawning, nursery and adult habitats, while the main river channel merely serves as a dispersal corridor for adult Pseudorasbora parva, one of the most successful invasive fish species that have colonized Europe. [source] | ||||||||||