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Surface microlayer in lakes of different trophic status : nutrients concentration and accumulation

Hillbricht-Ilkowska A., Kostrzewska-Szlakowska I.

Polish Journal of Ecology

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2004

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Vol. 52, nr 4

461-478

EN

In humic, mesotrophic and eutrophic lakes (Masurian Lakeland, Poland) 100-200 samples of water were taken with the Larsson' plate from 0.5 mm surface microlayer (SM) and compared with the subsurface water (SSW). The concentrations of dissolved (in filtered water) and total (unfiltered) Kjeldahl nitrogen (organic and ammonium) (DKN, TKN) and phosphorus (DP,TP) were measured and the concentration of their particulate (sestonic) forms (PON, PP) estimated. The enrichment (accumulation) factor (Ef) values were calculated as the ratio of nutrients concentration in SM versus SSW. Accumulation of nutrients in SM was a common phenomena in the studied lakes. However, it occurred more frequently (close to 100% of samples) for TKN than for TP (60-70%) as well as generally more frequently in humic lake than in other lakes. Mean values of EF for TKN were 2.6, 2.2 and 1.6 respectively for the humic, meso- and eutrophic lakes but the accumulation values for TP were lower - 2.3, 2.1 and 1.5 respectively for above lakes (the differences between concentrations in both layers as well as between lakes are significant). It means that in avverage the concentration of N and P in SM is at least two times greater than in SSW in humic and mesotrophic lakes. Accumulation of particulate forms of nutrients (PP, PKN) in SM is less ffrequent but the respective values of EF are higher comparing with the total content of these nutrients and again higher for nitrogen than phosphorus. The higher values of the weight ration N:P (33-76) in seston were found in SM in comparison with SSW (24-56) as well as higher contribution of particulate (sestonic) N (PON) to its total content in respective layer. Generally higher values of these two indices were found in both layers of humic lake than in other lakes. No significant differences were found for the Ef values calculated for spring and summer periods (Expected to differ in organic matter production and algae biomass) as well as for different sites (open water, shore region) in the lakes. It was concluded that the humic substances of allochthonous origin (mostly refractory and of high molecular weight) possibly predominate in the surface microlayer of the humic lake and support the stability and specificity of this layer in comparison with deeper water layer as well as in comparison with the meso- and eutrophic lakes. In highly productive, eutrophic lake, the surface microlayer is less distinct and stable possibly because of relatively greater role in situ autochthonous production of labile organic matter which shows low affinity to the air-water interface. The surface microlayer in mesotrophic lake displays somehow intermediate properties in comparison with humic and eutrophic lakes.

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Riparian zones : where biogeochemistry meets biodiversity in management practice

Décamps H., Pinay G., Naiman R. J., Petts G. E., McClain M. E., Hillbricht-Ilkowska A., Hanley T. A., Holmes R. M., Quinn J., Gibert J., Planty Tabacchi A.-M., Schiemer F., Tabacchi E., Zalewski M.

Polish Journal of Ecology

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2004

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Vol. 52, nr 1

3-18

EN

Riparian zones are well known for their inherent ecological properties related to biogeochemical cycles, biodiversity, and catchment management. The international MAB/UNESCO programme which was running between 1988 and 1998 was related to the land/water ecotones, mainly riparian zones. This article, inspired by this programme - seeks to highlight the role of riparian processes on biogeochemical cycles and biodiversity under different climatic conditions. Their role is investigated by focusing on: 1) the lateral ecotone between land and water systems, 2) their longitudinal corridor structure and, 3) the drywet cycles. This information is then used to suggest the value of riparian zones in landscape management. We emphasize the key roles of the ecotonal structure, longitudinal connectivity and timing of the occurrence of wet-dry cycles for riparian zones to process nitrate fluxes and to maintain high levels of biodiversity at the landscape scale. In the context of the worldwide transformations of flow regimes, the deterioration of water quality and loss of biodiversity, restoring riparian zones is both a key objective and a formidable challenge that implies envisioning the consequence of management actions on the long term, considering entire river basins, and paying attention to the other environmental, regional and global changes.

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River-lake system as mosaic pattern of landscape patches and their transition zones (ecotones)

Hillbricht-Ilkowska A., Węgleńska T.

Polish Journal of Ecology

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2003

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Vol. 51, nr 2

163-174

EN

A river-lake system (i.e. a river flowing through the lakes) can be perceived as a system of lentic (lake) and lotic (river sections) landscape "patches" and the transitory zones between them. In this system transport and exchange of matter and biological information take place. Taking the Krutynia river (Masurian Lakeland, Poland) and its lakes as an example, transport of different biologically active compounds (like phosphorus) and non-active substances (like chlorides) was characterized. Phosphorus retention was estimated in successive "patches" of the system. The biotic structure and function of the river-lake-river transitory zones were described. They are the places where the particles selection and sedimentation of matter transported in the system take place as well as they are the sites where the selection and exchange of planktonic organisms of different size and reproduction strategy occur.

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River-lake system in a mosaic landscape; main results and some implications for theory and practice from studies on the river Jorka system (Masurian Lakeland, Poland)

Hillbricht-Ilkowska A.

Polish Journal of Ecology

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2002

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Vol. 50, nr 4

543-550

EN

The basic results and conclusions of multi-year studies (described in detail in previous papers) on the river-lake system in the lakeland region of north-eastern Poland are shortly presented in relation to the selected general ecological problems. The study area was proved to be representative of the mosaic landscape structure and of the river-lake system as a trophic continuum with the spatial pattern of human impact established a century ago. Generally low export rates of nutrients and relatively low input to the lakes were found as typical of the region. However, year-toyear variation in nutrient export from the lake watersheds was high, mostly related to the discharge variation, and highest in the vernal period; the highest values were found for polluted fragments of the watershed. The long-term relative stability of in-lake trophic conditions was found and their basic relation to the lake position in the river system. The role of wetlands (isolated patches and the zones close to lakes) in diminishing the nutrient input was proved and their vegetation was described. Some consequences of the possible global warming and decrease in discharge and water table in the region were pointed out, such as the pulsing (concentrated in the freshet period) system of water and nutrient supplying, sink or source function of lakes in the river system (positive or negative nutrient retention in successive lakes), change in eutrophication rate, and its symptoms. The main implications for watershed management in the lakeland region are indicated.

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Nutrient loading and retention in lakes of the Jorka river system (Masurian Lakeland, Poland) : seasonal and long-term variation

Hillbricht-Ilkowska A.

Polish Journal of Ecology

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2002

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Vol. 50, nr 4

459-474

EN

The nutrient (TP, N-NO3, TKN - Kjeldahl nitrogen) loading to lakes (from river, precipitation, direct catchment) and in-lake retention were calculated for five successive lakes of the river-lake system typical of the mosaic, hilly lakeland region (the Jorka system, Masurian Lakeland). The annual values of loading for TP and TN were mostly not higher 1.0 and 15.0 g m^-2 lake area, respectively and rather low compared to other river-lake systems in the lakeland region. However, these values as well as nutrient in-lake retention decreased in 1997-1998 (warm and dry years) compared with 1978 and 19996, together with the decrease in discharge and exchange rate of lake water. In selected cases the retention of TP and TKN became negative which means that the lake functioned as the source of nutrients for downstream fragments of the system. The retention of nitrate-nitrogen was usually positive - lakes remained effective sites for its removal (denitrification). The possible changes in functioning of small catchments and chains of shallow, eutrophic lakes under the conditions of global warming are discussed.

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Links between landscape, catchment basin, wetland, and lake : the Jorka river-lake system (Masurian Lakeland, Poland) as the study object

Hillbricht-Ilkowska A.

Polish Journal of Ecology

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2002

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Vol. 50, nr 4

411-425

EN

The concepts and assumptions related to the landscape ecology, functioning of catchment basins, and eutrophication of lakes adopted in the presented studies are discussed. These studies concern: lake as a landscape component, importance of the patch pattern in the catchment, processes related to nutrient export, transformations and retention in lakes, specific problems of lake chains (river-lake systems), wetlands as lake-land ecotones responsible for nutrient removal, and other problems. Specific questions for the present studies (like long-term changes) and the study goals were indicated. General characteristics of the river-lake system under study (river Jorka on the Masurian Lakeland, north-eastern Poland), climatic conditions in the study periods, and the scope of the studies are shortly presented with reference to the particular papers in the volume.

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Eutrophication rate of lakes in the Jorka river system (Masurian Lakeland, Poland) : long term changes and trophic correlations

Hillbricht-Ilkowska A.

Polish Journal of Ecology

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2002

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Vol. 50, nr 4

475-487

EN

No trends were found in long-term variation (between the 1970s and the 1990s) of basic trophic parameters (TP, TN, chlorophyll concentration, algal biomass, and water transparency) in five lakes of the river-lake system typical of a lakeland, hilly area (the Jorka river system, Masurian Lakeland). Recently, this lake chain maintains the historically developed trophic differentiation between deep, mesotrophic lake close to headwaters and shallow, eutrophic lake close to the outlet of the river. The only change found is the replacement of cyanobacteria dominating in the 1970s by dinoflagellates dominating in the 1990s. A strong correlation was found between TP loading to lakes and in-lake TP concentration in spring periods, however no correlation existed between TP and other trophic indices. On the other hand, the interrelations between SD, chlorophyll, and algal biomass were highly significant in summer periods and marginally significant in spring periods. This pattern was also found in other groups of lakes in the region. It is concluded that in hilly lakeland region, the river-lake systems draining small mosaic catchments are resistant to the further eutrophication (low nutrient loading, no point sources) and for this reason they tend to maintain the trophic conditions developed in the remote past.

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Long term effects of liming in a humic lake : ecosystem processes, biodiversity, food web functioning (Lake Flosek, Masurian Lakeland, Poland)

Hillbricht-Ilkowska A., Dusoge K., Ejsmont-Karabin J., Jasser I., Kufel I., Ozimek T., Rybak J.I., Rzepecki M., Węgleńska T.

Polish Journal of Ecology

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1998

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Vol. 46, no 4

347-415

EN

The chemical composition of water and bottom sediments, productivity and decomposition rates as well as the biodiversity and food web functioning (organic suspension, edible algae, bacterio-detrivores, herbivores, grazers, predators) in plankton and benthos were analysed in humuc, weakly acid, mid-forest lake surrounded by peatmoss Sphagnum (Lake Flosek, Masurian Lakeland, Poland) before and 1-4 and 20-23 years after application of powdered lime. Calcium content and pH in water and sediment raised permanently. High water quality variables were main-tained after liming (low production, algal biomass, chlorophyll and nutrient concentration, low release rate of phosphorus from the sediments). Decomposition rate of organic matter increased significantly. The species richness and diversity of algae, rotifers, crustacean and benthic invertebrates increased at least twice as well as the abundance of bacterio-detrivores in plankton (small rotifers) and benthos (chironomids) and herbivores (big daphnids, diaptomids) in plankton. The distinct succession in species composition was observed in many taxa. The predators like larvae of Chaoborus, cyclopids and predatory rotifers became very abundant after 20 years since liming. No evident peatmoss mat spreading over the lake table has been observed since liming but also no detrimental effect on peatmoss surrounding the lake. It was concluded that the moderate liming affects first of all the biodiversity of lake biota then it stimulates the mobilisation of the lake which eventually lead to the greater and more stable complexity of trophic links. The species-rich and top-down controlled food web was installed in the limed lake without interfering with high quality of lake waters (low-productive, high-transparent) and unique, natural values of its surroundings.However, a slight increase in nutrient concentration after 22-23 years was observed which could be related to more efficient recycling mechanism in lake (due to abundant big components in plankton and benthos) or to eutrophication.