Wind-induced sediment resuspension as a potential factor sustaining eutrophication in large and shallow Lake Peipsi   总被引：1，自引：0，他引：1  

Olga Tammeorg  Juha Niemistö  Tõnu Möls  Reet Laugaste  Kristel Panksep  Külli Kangur 《Aquatic Sciences - Research Across Boundaries》2013,75(4):559-570

Using sediment traps, we aimed to elucidate the temporal and spatial variations in sediment fluxes in large and shallow Lake Peipsi, over the May to October 2011 period, and analyze the factors behind those variations. The effects of weather factors (mean and maximum wind velocity, water level and water temperature) on sediment resuspension and the concentrations of suspended solids (SS), total phosphorus (TP), soluble reactive phosphorus (SRP), and chlorophyll a (Chl a) were investigated. Moreover, the internal loading of TP due to sediment resuspension was determined. The sediment resuspension rates were significantly higher in the shallower waters than in the deeper parts of the lake. Resuspension was a major factor in sedimentation dynamics of the lake, which is presently subject to eutrophication. The rates of sediment resuspension followed the same pattern as gross sedimentation during the study period, and their respective values differed significantly between sampling dates. The highest resuspension rates were observed in September (mean 55.4 g dw m^?2 day^?1), when the impacts of wind events were particularly pronounced. Weather factors that were recorded approximately 2 weeks before water and sediment sampling affected the gross sedimentation and sediment resuspension. The water quality variables of SS, TP, SRP, Chl a were similarly affected. During the study, TP concentrations of the water were mainly determined by the resuspension of sediments containing a large pool of organic material. Although internal loading of TP due to resuspension was several times greater than external loading, external loading determines the amount of phosphorus that enters the lake and can be resuspended.  相似文献   

Holocene lake-level changes and their reflection in the paleolimnological records of two lakes in northern Estonia   总被引：1，自引：0，他引：1  

Jaan-Mati Punning  Mihkel Kangur  Tiiu Koff  Göran Possnert 《Journal of Paleolimnology》2003,29(2):167-178

Sediment cores from two neighbouring lakes (Viitna Linajärv and Viitna Pikkjärv) in northern Estonia were studied to determine lake-level fluctuations during the Holocene and their impact on biogeochemical cycling. Organic matter and pollen records dated by radiocarbon and radiolead indicated a water level rise in both lakes during the early Holocene (c. 10 000–8000 BP). A regression followed around 7500 BP and several transgressions occurred during the latter half of the Holocene, c. 6500 and 3000 BP. Human impact during the last centuries has caused short-term lake-level fluctuations and accelerated sediment accumulation in the lakes. The differences in water depth led to variations in sediment formation. During 10 000–8000 BP (Preboreal and Boreal chronozones) mineral-rich sediments with coloured interlayers deposited in L. Linajärv. These sediments indicate intensive erosion from the catchment and oxygen-rich lake, which favoured precipitation of iron oxides and carbonates. Fluctuations in water depth, leaching of nutrients from catchment soils and climatic changes increased the trophy of L. Linajärv around 6000 BP. The subsequent accumulation of gyttja, the absence of CaCO₃ and the decrease in both the C/N ratio and phosphorus content in the sediments also indicate anoxic conditions in the hypolimnion. The similarity in the development of L. Linajärv and L. Pikkjärv and their proximity made it possible to discern the impact of water depths changes on biogeochemical cycling in lakes.  相似文献   

Environmental factors influencing the biodeposition of the suspension feeding bivalve Dreissena polymorpha (Pallas): Comparison of brackish and freshwater populations     

Velda Lauringson  Evely Mlton  Jonne Kotta  Külli Kangur  Helen Orav-Kotta  Ilmar Kotta 《Estuarine, Coastal and Shelf Science》2007,75(4):459-467

Invasive suspension feeders have been particularly successful in shallow eutrophic estuarine and freshwater ecosystems. The impact of an invasive species is strong under favourable conditions. However, suboptimal feeding conditions may significantly reduce the impact to ambient environment. The invasive bivalve Dreissena polymorpha (Pallas) is able to colonize both fresh and brackish waterbodies. In an in situ experiment the seasonal variability in the biodeposition of D. polymorpha from fresh and brackish water populations was quantified at different temperature, salinity and chlorophyll a (Chl a) regimes. Salinity fluctuations in brackish water areas, temperature and water Chl a content were all important factors in the model of mussels' feeding. The results indicated that D. polymorpha fed significantly more in fresh than in brackish water. Mussels acclimated more easily to acute transfer from brackish to freshwater than vice versa. The biodeposition of zebra mussels increased with temperature and water Chl a content but these effects were less straightforward than that of salinity. The results suggest that the impact of D. polymorpha on recipient ecosystem is more pronounced in fresh than in brackish water environments.  相似文献