Renata Dondajewska

Functioning of the Lake Rusałka ecosystem in Poznań (western Poland)

Functioning of the Lake Rusałka ecosystem in Poznań (western Poland) Lake Rusałka is a shallow, artificial, strongly eutrophic reservoir. Thermal stratification is weak and comprises only about 8% of the bottom surface. In summer, the epilimnion is oversaturated with oxygen due to intensive phytoplankton growth (chlorophyll a up to 80.2 μg l-1), while conditions in the hypolimnion are anaerobic. The high concentration of ammonium nitrogen and low N:P ratio stimulated intense growth of cyanobacteria in the period from June to November. The domination of rotifers in the metazooplankton and low diversity and biomass of benthic macroinvertebrates was the cause of low top-down pressure of these organisms on the phytoplankton. The most advantageous restoration measures were identified to improve water quality and make the recreational use of the lake possible.

Phosphorus release from the bottom sediments of Lake Rusałka (Poznań, Poland)

Phosphorus release from the bottom sediments of Lake Rusałka (Poznań, Poland) Experimental research conducted on bottom sediments from the eutrophic Lake Rusałka (Poznań, Poland) indicated that the phosphorus release process has a significant influence on the functioning of the ecosystem. Internal loading was very intense in the deepest part of the lake, where it reached up to 29.84 mg m-2 d-1 P under anaerobic conditions. This part of the lake, however, was insignificant to overall internal loading. The highest loading was from the lake shallows, which covered 92% of the bottom area. Total mean annual loading to the ecosystem was 1214.5 kg year-1 P, i.e., 3.31 g m-2 year-1 P.

Phytoplankton Composition and Abundance in Restored Maltański Reservoir under the Influence of Physico-Chemical Variables and Zooplankton Grazing Pressure

In this paper we present the effects of environmental factors and zooplankton food pressure on phytoplankton in the restored man-made Maltański Reservoir (MR). Two methods of restoration: biomanipulation and phosphorus inactivation have been applied in the reservoir. Nine taxonomical groups of phytoplankton represented in total by 183 taxa were stated there. The richest groups in respect of taxa number were green algae, cyanobacteria and diatoms. The diatoms, cryptophytes, chrysophytes, cyanobacteria, green algae and euglenophytes dominated in terms of abundance and/or biomass. There were significant changes among environmental parameters resulting from restoration measures which influenced the phytoplankton populations in the reservoir. These measures led to a decrease of phosphorus concentration due to its chemical inactivation and enhanced zooplankton grazing as a result of planktivorous fish stocking. The aim of the study is to analyse the reaction of phytoplankton to the restoration measures and, most importantly, to determine the extent to which the qualitative and quantitative composition of phytoplankton depends on variables changing under the influence of restoration in comparison with other environmental variables. We stated that application of restoration methods did cause significant changes in phytoplankton community structure. The abundance of most phytoplankton taxa was negatively correlated with large zooplankton filter feeders, and positively with zooplankton predators and concentrations of ammonium nitrogen and partly of phosphates. However, restoration was insufficient in the case of decreasing phytoplankton abundance. The effects of restoration treatments were of less importance for the abundance of phytoplankton than parameters that were independent of the restoration. This was due to the continuous inflow of large loads of nutrients from the area of the river catchment.

The bottom sediments of Lake Uzarzewskie - a phosphorus source or sink?

The bottom sediments of Lake Uzarzewskie - a phosphorus source or sink? Phosphorus release from bottom sediments studied in two zones of Lake Uzarzewskie differing in depth and water oxygenation displayed seasonal and spatial variability. The experiments indicated that the lake receives considerable internal loading, especially from the deeper, anaerobic, rarely-mixed part of the lake. Meanwhile, the shallow zone situated in the 0-3 m depth range, could be a sink for phosphorus during spring and a source during other seasons of the year. The total loading of phosphorus from the bottom sediments was over 950 kg year-1 P, and 83% of this amount originated from the deeper part of the lake. The mean release from this part was 24.89 mg m-2 d-1 P and the maximum in fall was 35.4 mg m-2 d-1 P.

An appraisal of changes in seasonal water quality during passage through a shallow reservoir in Western Poland

Following restoration changes in Antoninek Reservoir physico-chemical and biological processes in the water column and bottom sediments were measured to outline mechanisms of changes in nitrogen, phosphorus and organic matter concentrations during water flow through this reservoir. Intensive mineralisation of organic matter in the shallow sediments stimulated primary production and influenced increasing ammonia and nitrite nitrogen concentrations. Two main factors affected concentrations of phosphorus: (1) its presence in the external loads of river waters entering the reservoir, more important in the colder seasons as the water discharge was higher and (2) from the internal loads coming from bottom sediments. The quality of the river water during its flow through this reservoir improved for most parameters and seasons. However, concentrations of nutrients were still high in waters flowing out from the reservoir and in some months they were higher in the outflow than in waters entering the reservoir.

Internal phosphorus loading in selected lakes of the Cybina River valley

Internal phosphorus loading in selected lakes of the Cybina River valley The aim of this study was to assess the ability of bottom sediments to release or accumulate phosphorus. Ex situ experiments with the use of undisturbed sediment cores were done in 11 lakes situated in the Cybina River valley (Wielkopolska, Poland). Phosphorus release was observed both in aerobic and anaerobic conditions, however greater values were noted in the latter ones. Maximum values reached 41.4 mg m-2 d-1 P and 12.2 mg m-2 d-1 P in anaerobic and aerobic conditions, respectively.

Influence of stormwater runoff on macroinvertebrates in a small urban river and a reservoir

The impact of stormwater on benthic macroinvertebrates was studied in two annual cycles. Five small catchments drained by stormwater sewers to a small urban river and a small and shallow reservoir situated in its course were selected. These catchments were located in residential areas with single-family houses or blocks of flats as well as industrial areas, i.e., a car factory, a glassworks and showroom as well as the parking lots of a car dealer and servicing company. In addition to the five stations situated in the vicinity of the stormwater outlets, three stations not directly influenced by stormwater were also established. Macroinvertebrates were sampled in every season, four times per year. Both abundance and biomass were assessed. Stormwater from industrial areas associated with cars, whose catchments showed a high percentage of impervious areas, had the greatest impact on benthic macroinvertebrates. This was due to a large amount of stormwater and its contamination, including heavy metals. Stormwater outflow from residential multi-family houses exerted the least influence. Macroinvertebrates in the water reservoir were found to undergo more extensive changes than those in the river. The cascade of four reservoirs resulted in a marked improvement of water quality in the river, which was confirmed by species composition, abundance and biomass of macroinvertebrates and indicators calculated on their basis for the stations below the cascade in comparison to the stations above and in the first reservoir. These reservoirs replaced constructed wetlands or other measures, which should be undertaken for stormwater management prior to its discharge into urban rivers and other water bodies.

Total phosphorus and organic matter content in bottom sediments of lake under restoration measures with iron treatment

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.

Water level fluctuations in selected Wielkopolski National Park lakes in 2012 against changes noted in 2007-2008

Abstract 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.

The variability of phosphorus fractions in sediments of a shallow, restored Antoninek Reservoir (Poznań, Poland)

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.