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The Relationship between Primary Production and Respiration in the Photic Zone of the Great Mazurian Lakes (GMLS), in Relation to Trophic Conditions, Plankton Composition and Other Ecological Factors

Siuda W., Kauppinen E. S., Kaliński T., Chróst R. J., Kiersztyn B.

Polish Journal of Ecology

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2017

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Vol. 65, nr 3

303--323

EN

The relation of primary production to respiration and dependence of both processes on various environmental factors were investigated in the surface waters of lakes of The Great Mazurian Lake System (GMLS) during summer seasons 2009-2011. Primary production and extracellular release was determined by 14C method, respiration (dark oxygen consumption) - by Winkler's method. Collected results allow to conclude that: (i) in all studied lakes primary production was primarily cyanobacterial, although in mesotrophic ones participation of eukaryotic phytoplankton in light CO2 fixation was more pronounced; (ii) in mesotrophic part of GMLS primary production was limited alternately by N and P availability and less dependent on N and P regeneration processes, whereas in southern, eutrophic lakes it was primarily fueled by regeneration of biogenic substances from organic compounds and strongly limited by N resources; (iii) although in photic zone of whole GMLS respiration was dominated by heterotrophic bacteria, in its mesotrophic part also participation of other plankton components in respiration processes was significant and, (iv) that in eutrophic lakes planktonic respiration was more dependent on low molecular weight products liberated enzymatically from organic substrates than on organic compounds released by primary producers. The mean production to respiration ratio, which varied from 2.11 to 2.60 in northern, and from 2.05 to 3.67 in southern lakes suggested that during period of investigations photic zones of lakes of both parts of GMLS were net autotrophic systems.

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The Role of Planktonic Organisms in Urea Metabolism in Lakes of Temperate Zone : Case Study

Siuda W., Chróst R. J., Kalinowska K., Ejsmont-Karabin J., Kiersztyn B.

Polish Journal of Ecology

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2016

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Vol. 64, nr 4

468--484

EN

Although urea is the simplest N-containing organic compound ubiquitous in all aquatic environments, its role in N-nutrition of planktonic biota and relevance for eutrophication of freshwater ecosystems is still insufficiently defined and often bypassed. The dynamics of production of autochthonous urea as well as maximal potential net ureolytic activity (net URA Vmax) of phyto- and bacterioplakton were studied in mesocosm experiment and verified during the field studies conducted in the Great Mazurian Lake system (GMLS). Analysis of the obtained results revealed that the proteins were the main autochthonous urea precursors. Urea concentration in the studied mesocosms and in GMLS surface waters was positively correlated with flagellate, ciliate and crustacean biomass and, less evidently, with bacterial biomass (BB). In surface waters of GMLS net URA Vmax, similarly as urea concentrations, increased with their trophic status. Analysis of correlation of potential ureolytic activity with chlorophylla, (Chla) BB and L-leucine aminopeptidase activity (AMP) in lakes of different trophic status suggests that although both groups of planktonic microorganisms participated in urea decomposition processes, in eutrophic ones bacterial decomposition of urea is more evident. In highly eutrophic lakes excess of phosphorus induced higher nitrogen requirement resulting in the increase in protein decomposition rate. Intensified protein degradation resulted faster urea production, which finally induced higher ureolytic activity of planktonic microorganisms. In profundal waters of GMLS potential ureolytic activity was distinctly lower than in surface waters. This was caused by low temperature of hypolymnetic waters, inhibitory effect of hydrogen sulphide and lack of phytoplankton, which is known as a primary urea consumer.

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Urea in lake ecosystem: the origin, concentration and distribution in relation to trophic state of The Great Mazurian Lakes (Poland)

Siuda W., Kiersztyn B.

Polish Journal of Ecology

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2015

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Vol. 63, nr 1

110--123

EN

The distribution, concentrations and origin of urea were studied in surface and profundal waters of meso-eutrophic and highly eutrophic parts of The Great Mazurian Lake System (GMLS) during spring – autumn period. Urea concentrations varied from 0.25 µM in surface layer to 3.36 µM in profundal zone of studied lakes and were in the range of concentrations noted in other non-polluted freshwater habitats. In the photic zone of lakes of GMLS Urea N made up to 10 % the total DON pool and often exceeded 2-3 times of NH4+-N concentrations. Pattern of changes in urea concentrations observed during three-years study excludes external urea input and suggests supplementation of lake waters with this compounds by phytoplankton decomposition processes. Generally, urea concentrations were negatively correlated with the trophic state index calculated from “algal” as well as from “bacterial” determinants. However, more detailed analysis showed that the relationships between production and assimilation of urea by various plankton components as well as the ecological role of this compound in meso- and eutrophic lakes could be different.

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Enzymatic fingerprints used for comparison of physiological diversity of microbial communities in clear-water and humic lakes

Siuda W., Jasser I., Kiersztyn B.

Polish Journal of Ecology

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2013

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Vol. 61, nr 4

715--728

EN

Extracellular enzymes occurring in aquatic environment are heterogeneous in respect to their origin and function, place, where they are located and their activity. They can be divided into mainly ‘bacterial-origin’ enzymes produced by heterotrophic organisms in order to obtain organic carbon, and mostly ‘phytoplankton-bacterial-origin’ enzymes, which are produced by autotrophic and heterotrophic organisms, and are responsible mainly for obtaining inorganic compounds. Enzymes activity provides information about microorganisms present in given environment and about their physiological state. We hypothesize that the patterns (‘fingerprints’) calculated on the basis of activity of several enzymes both mainly ‘bacterial-origin’ and mainly ‘phytoplankton-bacterial-origin’ may be used to characterise lake ecosystems in terms of the physiological structure of aquatic microorganisms present in these lakes. For the study we selected four lakes from Mazurian Lakes District in north-eastern Poland. Three of them were clear-water (lakes: Kuc, Mikołajskie, Tałtowisko) and ranged from oligotrophy to eutrophy, the fourth (Lake Smolak Duży) was slightly acidic (pH 5.2), highly productive and polyhumic. Activity of phosphatase (PA), L-leucine-aminopeptidase (AMP), β-glucosidase (B-Glu), esterase (EST), glucosaminidase (Glu-ami), glucuronidase (Glu-uro) and cellobiohydrolase (Cellob) were measured fluorometrically. The results were normalised and analysis of agglomerative clustering was performed to create an enzyme activity patterns characteristic for lakes. We found out that the enzymatic pattern reflected trophic differences between studied lakes. The patterns (‘fingerprints’) of enzymes were similar for three clear-water lakes, with urease (U–ase), AMP and EST dominating the overall enzymatic activity, but differed substantially for polyhumic lake, in which considerably high PA and saccharolytic enzyme activities were observed. We conclude that the analysis of enzymatic ‘fingerprints’ can be a useful tool to characterise lakes with respect to their trophic status and physiological diversity of microbial assemblages associated with each particular lake.