The variability of phosphorus fractions in sediments of a shallow, restored Antoninek Reservoir (Poznań, Poland)
Spatial and temporal variability of phosphorus (P) fractions content in bottom sediments of a shallow preliminary reservoir was studied in Antoninek, situated in Poznań. Fractions were analyzed at least once in a season (more often in spring and summer) between August 2004 and November 2005 according to the fractioning protocol proposed by Psenner et al. (1988). Circa 10 cm thick sediment layers were collected from three study sites, situated along the main axis of the reservoir. The contribution of NH4Cl-P and BD-P, i.e. the most accessible fractions biologically was similar at all stations (usually below 10%). The share of other fractions increased according to the sequence NaOH-RP < NaOH-NRP < HCl-P < Res-P. Only at station 1 the amount of phosphorus related to organic matter was lower than with aluminum. The domination of Res-P fraction indicated that the main part of phosphorus in sediment is biologically unavailable, therefore the intensity of phosphorus loading from sediments shall be low. However, high organic matter content, noted in sediments of Antoninek Reservoir, determined great amount of NaOH-NRP fraction. Both parameters remained under the influence of mats of macroalgae, growing intensively in the reservoir during vegetation season. The role of sediments as a source of phosphorus for water column enlarged, due to increased organic matter decomposition, especially in periods of high water temperature in this shallow reservoir.
Katarzyna Kowalczewska-Madura, Renata Dondajewska and Ryszard Gołdyn
Total phosphorus and organic matter content in bottom sediments of lake under restoration measures with iron treatment
Rusałka Lake is a shallow, man-made, strongly eutrophicated reservoir, being a place of recreational activities for Poznan citizens. Restoration measures with the use of iron sulphate were conducted in years 2006-2007. Phosphorus and organic matter concentrations in lake sediments were analyzed in years 2005-2007 at two research stations (profundal and littoral) to determine its changes under the influence of restoration. Greater phosphorus concentrations were noted in profundal (max 1.55 mg P g-1 dry weight (DW)) than in littoral (max 0.98 mg P g-1 DW). An increase of P amount in sediment was observed after iron treatment. Among phosphorus fractions Res-P dominated, i.e. phosphorus biologically unavailable for organisms. Organic matter content reached 23.1% in profundal, while 14.8% in littoral. Its amount decreased in following years.
Michał Lorenc, Renata Dondajewska and Lech Kaczmarek
The results presented in this paper of water level fluctuations in selected lakes of Wielkopolski National Park have a preliminary character, contributing new information to the knowledge on this area. Five lakes situated in three distinct tunnel valleys were selected for research: Jarosławieckie, Góreckie, Budzyńskie, Witobelskie and Łódzko-Dymaczewskie. The water level was measured from December 2006 till January 2008 and from January till December of 2012 with ca. monthly frequency. An increase in the water stage was noted in the autumn-winter period, which was rather unusual. The comparison of years 2007 and 2012 indicated higher water levels in the latter. The amplitude of the water level was higher in flow-through lakes due to the reaction to precipitation in early spring as well as different catchment features. Specific water level fluctuations in Lake Góreckie are probably related to the influence of groundwater of the Wielkopolska fossil valley.
Renata Dondajewska, Ryszard Gołdyn, Beata Messyasz, Katarzyna Kowalczewska-Madura and Sławek Cerbin
Qualitative analyses of nitrogen and phosphorus loads reaching the lake ecosystem provide a basis for pollution control, which is of paramount importance in shallow lakes due to the rapid turn-over of matter and energy. The studies of both external and internal loading were conducted in Lake Łeknenskie, a very shallow, through-flow lake situated in Western Poland. Strong eutrophication is manifested in rich rush vegetation and a lack of submerged macrophytes as well as nitrogen and phosphorus concentrations (max 13.04 mg N dm−3 and 0.32 mg P dm−3, respectively). Constant domination of cyanobacteria in the phytoplankton community was noted in almost all seasons with a 98% share in summer, resulting in 20 cm water transparency and 223 μg dm−3 of chlorophyll-a. The zooplankton community was dominated by rotifers. The main source of nutrients was the River Nielba. Spatial external nutrient loading was 1.93 g P m−2 yr−1 and 77.55 g N m−2 yr−1. An even higher load of phosphorus was released from the bottom sediments, 2.18 g P m−2 yr−1. A comprehensive action plan is required, aiming at the reduction of both external and internal nutrient loading. A series of solutions regarding local environmental conditions should be applied in the lake catchment, including biogeochemical barriers, denitrification walls, artificial retention basins or wetlands, but most of all – improvement in the functioning of the wastewater treatment plant. Restoration is possible, however, protection measures reducing external loading should be undertaken prior to phosphorus inactivation in the water column and in the bottom sediments, supported by biological methods e.g. biomanipulation.