The influence of flushing on nutrient dynamics, composition and densities of algae and transparency in Veluwemeer, The Netherlands (original) (raw)
Related papers
Freshwater Biology, 2005
1. The responses of nutrient concentrations, plankton, macrophytes and macrozoobenthos to a reduction in external nutrient loading and to contemporary climatic change were studied in the shallow, moderately flushed Lake Mü ggelsee (Berlin, Germany). Weekly to biweekly data from 1979 to 2003 were compared with less frequently collected historical data. 2. A reduction of more than 50% in both total phosphorus (TP) and total nitrogen (TN) loading from the hypertrophic to the eutrophic period (1997)(1998)(1999)(2000)(2001)(2002)(2003) was followed by an immediate decline in TN concentrations in the lake. TP concentrations only declined during winter and spring. During summer, phosphorus (P) release from the sediments was favoured by a drastic reduction in nitrate import. Therefore, Mü ggelsee acted as a net P source for 6 years after the external load reduction despite a mean water retention time of only 0.1-0.16 years. 3. Because of the likely limitation by P in spring and nitrogen (N) in summer, phytoplankton biovolume declined immediately after nutrient loading was reduced. The formerly dominant cyanobacteria (Oscillatoriales) Limnothrix redekei and Planktothrix agardhii disappeared, but the mean biovolume of the N 2 -fixing species Aphanizomenon flosaquae remained constant. 4. The abundance of Daphnia spp. in summer decreased by half, while that of cyclopoid copepod species increased. Abundances of benthic macroinvertebrates (mainly chironomids) decreased by about 80%. A resource control of both phytoplankton and zooplankton is indicated by significant positive correlations between nutrient concentrations and phytoplankton biovolume and between phytoplankton and zooplankton biomass. 5. Water transparency in spring increased after nutrient reduction and resulted in recolonisation of the lake by Potamogeton pectinatus. However, this process was severely hampered by periphyton shading and grazing by waterfowl and fish. 6. Water temperatures in Mü ggelsee have increased in winter, early spring and summer since 1979. The earlier development of the phytoplankton spring bloom was associated with shorter periods with ice cover, while direct temperature effects were responsible for the earlier development of the daphnid maximum in spring.
The effects of reduced phosphorus and nitrogen loading on phytoplankton in Mondsee, Austria
Hydrobiologia, 1992
Following restoration measures (ring canalization, treatment plant with phosphorus precipitation), phosphorus loading declined step-wise from 26.21 t year-' to 9.18 t year-' during the period 1979-1984 while P-retention increased from 48% to 78%. Phosphorus loading was poorely correlated with precipitation. Inorganic nitrogen load, largely NO,-N, did not decline but was significantly correlated with precipitation (r = 0.95) throughout the investigation period (1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989).
Aquatic Ecology, 2015
The Borderlakes are a chain of ten shallow, largely artificial, interconnected lakes in the Netherlands. The ecological recovery of the central Borderlakes (viz. lake Veluwe and Wolderwijd) has been well documented. These lakes shifted from a eutrophic, Planktothrix dominated state in the 1970s to a clear state in 1996. Around 2010, the formerly hypertrophic, southern Borderlake Eem also reached a clear state, but at considerably higher nutrient levels. In this paper, monitoring data are used to compare these changes and identify the differences in driving processes and their consequences. The 1996 shift in Lake Veluwe was linked to increased fishery for benthivorous Bream, followed and stabilized by increase in Zebra Mussels and charophytes. Nutrients in Lake Eem decreased as well and Planktothrix disappeared here too in 1996, despite relatively high TP concentrations which remained stable over time.