Quantifying spatial and temporal dynamics of organic matter (OM) is critical both for understanding ecosystem functioning and for predicting impacts of landscape change. To determine the influence of different habitats and coarse particulate OM (CPOM) types upon floodplain OM dynamics, we quantified aerial input, lateral surface transfer, and surface storage of CPOM over an annual cycle on the near-natural floodplain of the River Tagliamento in NE-Italy. Using these data, we modelled floodplain leaf dynamics, taking account of the spatial distribution and hydrologic connectivity of habitats, and using leaf storage as a response variable. Mean aerial CPOM input to the floodplain was similar from riparian forest and islands, but surface transfer was greater from islands, supporting the suggestion that these habitats act as “islands of fertility” along braided rivers. Leaves were the lateral conveyor of energy to more open parts of the floodplain, whereas CPOM was mainly stored as small wood in vegetated islands and riparian forest. Simulating the loss of habitat diversity (islands, ponds) decreased leaf storage on the whole floodplain, on exposed gravel and in large wood accumulations. In contrast, damming (loss of islands, ponds and floods plus floodplain overgrowth) greatly increased storage on exposed gravel. A random shuffle of habitats led to a storage increase on exposed gravel, while that in large wood accumulations and ponds declined. These results disentangle some of the complexities of CPOM dynamics in floodplain ecosystems, illustrate the value of models in understanding ecosystem functioning at a landscape level, and directly inform river management practice. 相似文献
Mogan Lake is the largest recreational area near Ankara, which is the capital city of Turkey. Increased macrophyte growth in the water body and the present levels of urban development within the catchment are reflected in declining water quality and aesthetic deterioation. A study of the water quality of the lake was undertaken to quantify the variation of phosphorus, nitrogen, and chlorophyll-a concentrations during ice-free seasons from 1992 to 1994. Its total phosphorus and chlorophyll-a concentrations indicate a meso-eutrophic status. The total phosphorus budget of Mogan Lake was measured for a period of 22 months. The estimation of nutrient loading using Dillon-Rigler nutrient budget shows that an artificial load caused too high phosphorus inputs. The management implications of phosphorus loading and budget are discussed. 相似文献
The aquatic vegetation of ?í?ov Lake in the Danube floodplain, which is listed in the Ramsar Convention, was investigated to address three main questions: (1) how have landscape composition and the structures of the lake and its buffer zone changed from the mid-20th century; (2) how have species richness and the abundance of the aquatic macrophyte assemblage in this lake ecosystem changed over the last 34 years; and (3) which landscape metrics can best explain these temporal changes for floating-leaved macrophytes? Two methodological approaches, remote sensing and botanical field surveys, were applied. Historical (1949, 1970, 1990) and contemporary (2006) aerial photographs were analysed to determine land cover. Landscape configuration and structure were analysed using eight landscape metrics selected in advance to measure spatio-temporal changes and the fragmentation of the lake ecosystem and its corresponding buffer zone. The species diversity, abundance and distribution of true aquatic macrophytes were surveyed eleven times in five survey stretches between 1973 and 2007.At the landscape level, a decrease in the area covered by floating-leaved macrophytes, as well as an increase in open water surface and fragmentation of the land cover classes in the lake ecosystem, were recorded from 1949 to 2006. Overall, 30 true aquatic macrophytes were found from 1973 to 2007. Species richness did not change considerably, but the abundance of aquatic species fluctuated over the years. Three groups of true aquatic vegetation, based on common structural characteristics, were found in 1973–1983, 1989–2002, and 2004–2007 over the last 34 years. The landscape metrics NP, PD, LPI, and SHDI, which all express patterns of landscape fragmentation mostly indicate temporal changes in floating-leaved macrophytes. 相似文献
Aquatic macrophytes produce large amounts of organic matter and have an essential structuring role in floodplains. This process highlights the importance of this community to aquatic biodiversity maintenance. We investigated the role of a flood disturbance on the response of macrophyte assemblages in regional and local structuring in the Upper Paraná River floodplain. Plant species were recorded before (November 2006) and after (March 2007) an uncommon increase in water level caused by the El Niño South Oscillation, which is considered a disturbance. Samples were taken in lakes and backwaters located in the floodplain and connected to three distinct rivers (that differentiate three sub-systems). Species richness and the assemblage structure of macrophyte patches underwent significant changes after the flood disturbance, depending on the specific sub-system (rivers) to which the lakes were connected. In addition, flood disturbance had a strong impact on community organization at the local scale. However, regionalization with respect to sub-systems remained significant after the flood disturbance. Our results emphasize the importance of connection to the river on macrophyte community composition and richness, and suggest that flood events in the Upper Paraná River floodplain disrupt community organization only at fine (local) scales. 相似文献
Strzeszynskie Lake was formerly a slightly eutrophic (meso-eutrophic) water body. The aim of the current research was to define variables on both spatial and seasonal internal phosphorus loading from bottom sediments at five stations located in zones varying in depth, oxygenation, macrophyte presence, and uses of the neighboring catchment area. Ex situ experiments done with the use of intact bottom sediment cores have shown that the highest phosphorus release occurred in the deepest part of the lake and reached 3.6?mg?P/m2d under anoxic conditions during summer thermal stratification. In turn, the internal loading from littoral sediments, which were well aerated all year round, was clearly lower. Furthermore, phosphorus accumulation in the bottom sediment was observed to reach a maximum of 1.45?mg?P/m2 d in autumn. A comparison of the internal loading intensity in lake zones with different land uses of the neighboring catchment area has shown slightly higher values at stations adjacent to the forest catchment area than those used for recreation. Changes in the land use of the catchment area of Strzeszynskie Lake, especially the increase in impermeable surfaces, have led to an increased inflow of external loads after heavy rains, resulting in deterioration in water quality and a delayed increase in internal loading. 相似文献
Surface waters in western Canada often experience eutrophication-related problems with water quality, specifically high internal phosphorus loading rates and excessive phytoplankton and macrophyte production, that lead to water column anoxia and restricted fisheries habitat. A group of researchers from across Canada were involved for a seven-year period in cooperative programs for surface water quality management in western Canada, based at the University of Alberta. This paper summarises information on two techniques, hypolimnetic oxygenation and lime (Ca2CO3 and Ca(OH)2) application, used in western Canada (specifically, the province of Alberta) to manage eutrophication in standing waters (lakes and reservoirs). 相似文献
Total phosphorus and its main forms: dissolved mineral, dissolved organic, particulate organic and particulate mineral in the vertical water column of three subalpine lakes of various types in Italy, has been estimated during the winter-vernal season. The range of variation in the phosphorus content in these waters was as follows: total phosphorus 16 ± 2860 μg/1 PO4, dissolved mineral phosphorus 4 ± 1040 μg/l PO4, dissolved organic phosphorus 1 ± 160μg/l PO4, particulate organic phosphorus 0 ± 290 μg/l PO4 and particulate mineral phosphorus 1 ± 100 μg/l PO4, Generally the content of total phosphorus and dissolved mineral phosphorus (phosphates) increased with the degree of eutrophy with the depth and with the progress of the vernal season towards the summer stagnation time. The amount of phosphates increased in water with the depletion of oxygen, both in the verical water column and with the progress of stagnation time. The amounts of dissolved organic phosphorus decressed with the depth of the vertical water column whereas the dissolved mineral phosphorus increased. The development of the particulate organic phosphorus stratification in the vertical water column was clearly visible in the eutrophic lake. The quantities of total phosphorus and its main component, dissolved mineral phosphorus, decreased evidently from January to May in all three lakes, mostly in the eutrophic lake. The reason of this decrease is sorption by lake sediments and to a certain degree sedimentation of phosphorus sorbed by ferric hydroxide. The increase of dissolved mineral phosphorus and that of total phosphorus in the vertical water column and with the progress of summer stagnation had as a reason the liberation of phosphorus from sediments, and not so much decomposition of sedimentating plankton or dissolved organic phosphorus. The share of single (mean) values of phosphorus forms in the total phosphorus was as follows: In the oligotrophic lake the share of particulate mineral phosphorus was extremely high in March (21% of the total), probably because of the inflow of the melting waters from the drainage area. The development of vertical stratification in waters of three subalpine Italian lakes at the end of the vernal season (May) indicates the quantitative prevailing of dissolved mineral phosphorus with its increase with the depth and domination of dissolved organic phosphorus in the trophogenic zone. 相似文献
This 10-year field data study explores the relevance of water level fluctuations in driving the shift from a free-floating plant (FFP) to a phytoplankton dominated state in a shallow floodplain lake from the Lower Paraná River. The multi-year natural flood pulse pattern in the Lower Paraná River drove the ecosystem regime from a FFP-dominant state during very high waters (1998–1999) to absolute phytoplankton prevalence with blooms of nitrogen fixing Cyanobacteria during extreme low waters (2008–2009). Satellite images support the observed changes over the decade and show the decrease of the surface lake area covered by FFP as well as the modification of the spectral firm in open waters, which documents the significant increases in phytoplankton chlorophyll a concentrations. We discuss the possibility that, despite a slow eutrophication in these highly vegetated systems, water level changes and not nutrients account for the shift from a floating macrophyte community to phytoplankton dominance. Cyclic shifts may occur in response to the seasonal floodpulse, but more strongly, as indicated by our results, in association to the extreme drought and flood events related to the El Niño Southern Oscillation, which is linked to discharge anomalies in the Paraná River. 相似文献