Ryszard Gołdyn

Food-web manipulation in the Maltański Reservoir

The Maltanski Reservoir (64 ha, mean depth 3.1 m) was emptied in September 1992, and all fish were harvested. Following refilling in the spring of 1993, fry of eel (Anguilla anguilla),pike (Esox lucius)and wels (Silurus glanis)were introduced, in total 236 fry ha–1. In 1994 the reservoir was additionally stocked with adult pike in spring (10 kg ha–1), with pike fry in summer (156 specimens ha–1), and pike and pikeperch (Stizostedion lucioperca)fry in the autumn (413 specimens ha–1). High water transparency and low concentration of chlorophyll-a were observed throughout 1993 except for a short period of water bloom caused by Aphanizomenonflos-aquaein summer. In the spring of 1994 only a short water bloom caused by diatoms was observed. Not only zooplankton grazing but also low phosphorus content limited the growth of phytoplankton biomass in this period. At the beginning of summer cladoceran biomass decreased, leading to a strong water bloom dominated by Planktothrix agardhii. During this event water transparency decreased to 0.3 m. This was a result of insufficient introduction of predatory fish, which could not ensure effective control of the rapidly increasing plankivorous fry numbers.

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.

Models of phosphorus turn-over in a hypertrophic lake: the Lake Swarzędzkie case study

Models of phosphorus turn-over in a hypertrophic lake: the Lake Swarzędzkie case study Phosphorus cycling between components of the ecosystem of the hypertrophic Lake Swarzędzkie was studied in 2000-2003. The results of this study revealed considerable seasonal variation in phosphorus cycling. The main sources of phosphorus load in winter were the tributaries, whereas in summer internal loading prevailed. However, the most effective source of SRP (soluble reactive phosphorus) for phytoplankton primary production in summer was its excretion by organisms from the microbial loop. The share of this source in the total phosphorus pool was 38%, whereas internal loading contributed 23.7%, external loading 16.3%, and regeneration by metazooplankton 22%. This exerted a significant influence on the functioning of the whole lake ecosystem. Limiting both external and internal phosphorus loading is recommended to facilitate water quality improvement in the lake.

Zooplankton phosphorus excretion in Swarzędzkie Lake (Western Poland) and its influence on phytoplankton

Zooplankton phosphorus excretion in Swarzędzkie Lake (Western Poland) and its influence on phytoplankton Zooplankton phosphorus excretion was studied in Swarzędzkie Lake in 2000-2002. Phosphorus excretion rates were high from spring through autumn, but low in winter. The highest value, 203.7 μgP 1-1 d-1 (vertical profile mean), was recorded in June 2000. The mean rate was 26.6 μgP 1-1 d-1 and was 10 times greater for rotifers than for both cladocerans and copepods. In most months, the calculated phosphorus excretion rate was greater than the sum of tributary external phosphorus loading and internal bottom sediment loading. Nevertheless, the influence of the zooplankton phosphorus excretion rate on yearly phytoplankton abundance, biomass and chlorophyll a was not statistically significant. Yearly variance in phytoplankton variables was best explained by a canonical variable composed of internal loading and zooplankton phosphorus excretion (total redundancy 32.8%).

Phytoplankton composition and physicochemical properties in Lake Swarzędzkie (midwestern Poland) during restoration: Preliminary results

Abstract This paper presents the preliminary results of a study of the phytoplankton structure and dynamics and physicochemical properties of Lake Swarzędzkie in 2011. The subject of the study is a shallow, elongated, post-glacial lake located in western Poland. The surface area is 93.7 ha with a maximum depth of 7.2 m. Its poor water quality led to the implementation of chemical and biological restoration procedures in an attempt to improve it. The highest concentration of total nitrogen was 13.07 mg l-1 N. Secchi depth (SD) was low in the summer with a minimum value of 0.5 m in September. The most abundant group of phytoplankton were cyanobacteria, and the maximum value of chlorophyll a concentration was 278.0 μg l-1. The dominant species were Pseudanabaena limnetica and Aphanizomenon gracile. Cyanobacteria were the most abundant phytoplankton until November. Maximum diatom, cryptophyte, and chrysophyte density was noted in the spring, and the most abundant were Nitzschia acicularis, Cryptomonas marssonii, Rhodomonas lacustris, Erkenia subaequiciliata, and Dinobryon sociale. One-hundred and thirty-six phytoplankton taxa belonging to nine taxonomic groups were identified in Lake Swarzędzkie. The highest number of taxa was noted among chlorophytes (57 taxa), cyanobacteria (19), diatoms (16), and chrysophytes (12), while other taxonomic groups were represented by smaller number of taxa.

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.

Environmental applications of ICP-MS for simultaneous determination of trace elements and statistical data analysis

Water samples collected from two lakes separated from each other by the cascade of four small lowland reservoirs were subjected to analyses in order to compare contamination levels in these ecosystems. Inductively coupled plasma mass spectrometry was used to determine eight elements: Al, As, Cd, Cr, Li, Mn, Sb, and Zn. Statistical methods were applied in order to assess the degree of self-purification of water, during its flow from Swarzędzkie Lake to Malta Lake. Obtained distinctly, lower concentrations of all studied elements in Malta Lake than in Swarzędzkie Lake indicated the role of self-purification processes, which occurred in the distance between these lakes.

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.