Waldemar Siuda - Academia.edu (original) (raw)
Papers by Waldemar Siuda
Postepy Mikrobiologii, 2001
Aquatic Microbial Ecology
Climate change is one of the most severe threats for ecosystems worldwide. Lakes can be studied a... more Climate change is one of the most severe threats for ecosystems worldwide. Lakes can be studied as indicators of climate change. The prokaryotic compartment of lakes is affected by climate change, and the metabolic processes of prokaryotes could both attenuate or exacerbate the negative impacts of climate change on the ecosystem. However, in contrast to studies on the impact of global warming on eukaryotes, prokaryotes have been rarely studied in the context of climate change. In our study, we tested the impact of short-term temperature increases on taxonomic and physiological bacterial diversity and their relationships. We conducted an experiment with different temperature treatments using mesocosms filled with lake water from the same water reservoir. We monitored physicochemical parameters for 2 wk and examined taxonomic diversity using Illumina next-generation sequencing and metabolic diversity using 31 carbon sources by the Biolog EcoPlate® method. We showed that a continuous i...
Postepy Mikrobiologii, 2007
Polish Journal of Ecology
The distribution, concentrations and origin of urea were studied in surface and profundal waters ... more 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 assimilat...
Polish Journal of Microbiology, 2006
Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers ... more Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 micromol l(-1). Maximal potential ureolytic activity (V(max)) ranged from 0.2 to 7.0 micromol l(-1) h(-1). The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto- and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilim...
Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagroze... more Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagrozeniem dla wod powierzchniowych środowiska przyrodniczego Wielkich Jezior Mazurskich (WJM) jest ich postepująca eutrofizacja. Choc wzrost zyzności (trofii) jest przejawem naturalnej ewolucji wszystkich zbiornikow wodnych, to przyspieszona eutrofizacja poludniowej cześci systemu WJM obserwowana w drugiej polowie XX wieku byla efektem szeroko pojetej aktywności czlowieka. Tempo procesow eutrofizacyjnych jest funkcją ilości substancji biogennych zgromadzonych w ekosystemach wodnych. Analiza danych historycznych dokumentujących zmiany calkowitego stezenia fosforu (PT) w wodach poludniowej cześci systemu WJM pozwolila wyodrebnic trzy wyraźnie zroznicowane etapy ewolucji tworzących go jezior: (i) okres do roku 1995, charakteryzujący sie szybką eutrofizacja i, zwlaszcza w jego schylku, wystepującymi okresowo gwaltownymi zaburzeniami homeostazy wod jeziornych; (ii) lata 1995–2005, w ktorych procesy eutrofizacyjne ulegly gwaltownemu spowolnieniu, a nawet odwroceniu (de-eutrofizacja) oraz; (iii) lata 2005–2011, w ktorych korzystne tendencje z lat 1995–2005 ulegly wyhamowaniu. W artykule poddano analizie przyczyny, mechanizmy i skutki zmian trofii jezior poludniowej cześci systemu WJM. Określono punkty krytyczne systemu decydujące o dynamice tych zmian. Wskazano potencjalne zagrozenia dla jakości wod WJM, a takze sformulowano szereg zalecen dotyczących ochrony ich zasobow wodnych oraz zlewni
Polish Journal of Ecology, 2013
Polish journal of microbiology, 2006
Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers ... more Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 micromol l(-1). Maximal potential ureolytic activity (V(max)) ranged from 0.2 to 7.0 micromol l(-1) h(-1). The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto- and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilim...
Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagroze... more Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagrozeniem dla wod powierzchniowych środowiska przyrodniczego Wielkich Jezior Mazurskich (WJM) jest ich postepująca eutrofizacja. Choc wzrost zyzności (trofii) jest przejawem naturalnej ewolucji wszystkich zbiornikow wodnych, to przyspieszona eutrofizacja poludniowej cześci systemu WJM obserwowana w drugiej polowie XX wieku byla efektem szeroko pojetej aktywności czlowieka. Tempo procesow eutrofizacyjnych jest funkcją ilości substancji biogennych zgromadzonych w ekosystemach wodnych. Analiza danych historycznych dokumentujących zmiany calkowitego stezenia fosforu (PT) w wodach poludniowej cześci systemu WJM pozwolila wyodrebnic trzy wyraźnie zroznicowane etapy ewolucji tworzących go jezior: (i) okres do roku 1995, charakteryzujący sie szybką eutrofizacja i, zwlaszcza w jego schylku, wystepującymi okresowo gwaltownymi zaburzeniami homeostazy wod jeziornych; (ii) lata 1995–2005, w ktorych proces...
Polish Journal of Ecology, 2013
Extracellular enzymes occur- ring in aquatic environment are heterogeneous in respect to their or... more Extracellular enzymes occur- ring 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' en- zymes produced by heterotrophic organisms in order to obtain organic carbon, and mostly 'phy- toplankton-bacterial-origin' enzymes, which are produced by autotrophic and heterotrophic or- ganisms, 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 ('finger- prints') calculated on the basis of activity of sev- eral 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 microorgan- isms present in these lakes. For the study we selected four l...
The heterotrophic activity of aquatic bacteria was measured by incorporation of 3H-thymidine, upt... more The heterotrophic activity of aquatic bacteria was measured by incorporation of 3H-thymidine, uptake of 14C-sodium acetate and mineralization of 14C-acetate. The temperature of water, oxygen content and concentration of chlorophyll a were also measured in the studied lakes. The obtained results of the studied processes in the surface layer and epilimnion were distinguished by negative correlation coefficients. A distinctive feature is the relation between chlorophyll a concentration in the water bodies and heterotrophic activity of bacteria. This indicates a negative dependence between these processes and phytoplankton activity in the photic zone. In contrast a positive relationship between phytoplankton activity and heterotrophic activity of bacteria was found in the metalimnion and hypolimnion of the studied lakes.
Polish River Basins and Lakes – Part I, 2019
One of the greatest threats to water quality is accelerated eutrophication, resulting from human ... more One of the greatest threats to water quality is accelerated eutrophication, resulting from human activity, like the high intensity of tourism, surface runoffs from fertilized fields, and municipal pollution. Water eutrophication manifests as excessive growth of phytoplankton caused by overabundant nitrogen, phosphorus, and other nutrient supply which causes deterioration of water quality related to the amount of bacterial biomass in eutrophicated water reservoirs. The Great Mazurian Lake System (GMLS) is a chain of lakes located in mesoregion of the Great Mazurian Lakes in the Northeastern Poland. All lakes of the GMLS are connected by natural or artificial channels built in the eighteenth and nineteenth centuries and nowadays create widely spilled, long (the easiest route from northern to southern edge is about 110 km) gutter unique on the scale of the continent. The lakes of GMLS are of glacial origin. During the last five decades, all lakes of the GMLS passed different levels of ...
Koniecznośc poprawienia przez Polske do roku 2015 stanu jakości wod powierzchniowych, jak rowniez... more Koniecznośc poprawienia przez Polske do roku 2015 stanu jakości wod powierzchniowych, jak rowniez coraz wieksza uwaga jaką spoleczności lokalne przywiązują do poprawy walorow krajobrazowych, rekreacyjnych i uzytkowych stawow, zalewow i jezior spowodowala w ostatnich kilku latach gwaltowny wzrost zainteresowania nie tylko ochroną lecz rowniez rekultywacją zbiornikow wodnych. Poniewaz glowną przyczyną zlej jakości ich wod jest przyspieszona eutrofizacja, dzialania rekultywacyjne skupiają sie przede wszystkim na ograniczaniu i likwidowaniu uciązliwych skutkow tego procesu. W artykule dedykowanym wszystkim zainteresowanym „leczeniem” chorych zbiornikow wodnych, a zwlaszcza urzednikom administracji lokalnej odpowiedzialnym za stan środowiska naturalnego gminy, powiatu czy wojewodztwa przedstawiono aktualny stan wiedzy dotyczącej teoretycznych podstaw roznorodnych technik rekultywacyjnych pozwalających na ograniczanie i czasowe cofniecie procesow degradacji plytkich ekosystemow wodnych. S...
This report describes the relationship between microbial enzymatic activities (aminopeptidase, es... more This report describes the relationship between microbial enzymatic activities (aminopeptidase, esterase, and alkaline phosphatase) and the trophic state index of the studied lakes. Pelagic surface water samples were collected from nineteen lakes (Mazurian Lake District, northeastern Poland), characterized by different degrees of eutrophication, during spring homothermy and summer thermal stratification periods in 1999 and 2000. Aminopeptidase and esterase activities of microbial assemblages in unfiltered water samples were positively proportional to the trophic conditions of the studied lakes and both enzymes significantly correlated with Carlson's trophic state index of lakes. No correlation between alkaline phosphatase activities and the trophic state index of the studied lakes was found. This study showed that the selected parameters of microbial activity are very useful for the rapid determination of actual trophic conditions in lake ecosystems.
This report describes the relationship between microbial enzymatic activities (aminopeptidase, es... more This report describes the relationship between microbial enzymatic activities (aminopeptidase, esterase, and alkaline phosphatase) and the trophic state index of the studied lakes. Pelagic surface water samples were collected from nineteen lakes (Mazurian Lake District, northeastern Poland), characterized by different degrees of eutrophication, during spring homothermy and summer thermal stratification periods in 1999 and 2000. Aminopeptidase and esterase activities of microbial assemblages in unfiltered water samples were positively proportional to the trophic conditions of the studied lakes and both enzymes significantly correlated with Carlson's trophic state index of lakes. No correlation between alkaline phosphatase activities and the trophic state index of the studied lakes was found. This study showed that the selected parameters of microbial activity are very useful for the rapid determination of actual trophic conditions in lake ecosystems.
Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers ... more Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 µmol l 1. Maximal potential ureolytic activity (V max) ranged from 0.2 to 7.0 µmol l 1 h 1. The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto-and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilimnetic water samples the bulk of the ureolytic activity originated from seston-attached bacteria. However, a positive, statistically significant correlation between ureolytic activity and chlorophyll a (Chl a) concentrations suggests that phytoplankton may also be responsible for at least a some of the observed ureolytic activity in the highly eutrophic Great Mazurian Lakes.
Postepy Mikrobiologii, 2001
Aquatic Microbial Ecology
Climate change is one of the most severe threats for ecosystems worldwide. Lakes can be studied a... more Climate change is one of the most severe threats for ecosystems worldwide. Lakes can be studied as indicators of climate change. The prokaryotic compartment of lakes is affected by climate change, and the metabolic processes of prokaryotes could both attenuate or exacerbate the negative impacts of climate change on the ecosystem. However, in contrast to studies on the impact of global warming on eukaryotes, prokaryotes have been rarely studied in the context of climate change. In our study, we tested the impact of short-term temperature increases on taxonomic and physiological bacterial diversity and their relationships. We conducted an experiment with different temperature treatments using mesocosms filled with lake water from the same water reservoir. We monitored physicochemical parameters for 2 wk and examined taxonomic diversity using Illumina next-generation sequencing and metabolic diversity using 31 carbon sources by the Biolog EcoPlate® method. We showed that a continuous i...
Postepy Mikrobiologii, 2007
Polish Journal of Ecology
The distribution, concentrations and origin of urea were studied in surface and profundal waters ... more 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 assimilat...
Polish Journal of Microbiology, 2006
Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers ... more Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 micromol l(-1). Maximal potential ureolytic activity (V(max)) ranged from 0.2 to 7.0 micromol l(-1) h(-1). The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto- and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilim...
Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagroze... more Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagrozeniem dla wod powierzchniowych środowiska przyrodniczego Wielkich Jezior Mazurskich (WJM) jest ich postepująca eutrofizacja. Choc wzrost zyzności (trofii) jest przejawem naturalnej ewolucji wszystkich zbiornikow wodnych, to przyspieszona eutrofizacja poludniowej cześci systemu WJM obserwowana w drugiej polowie XX wieku byla efektem szeroko pojetej aktywności czlowieka. Tempo procesow eutrofizacyjnych jest funkcją ilości substancji biogennych zgromadzonych w ekosystemach wodnych. Analiza danych historycznych dokumentujących zmiany calkowitego stezenia fosforu (PT) w wodach poludniowej cześci systemu WJM pozwolila wyodrebnic trzy wyraźnie zroznicowane etapy ewolucji tworzących go jezior: (i) okres do roku 1995, charakteryzujący sie szybką eutrofizacja i, zwlaszcza w jego schylku, wystepującymi okresowo gwaltownymi zaburzeniami homeostazy wod jeziornych; (ii) lata 1995–2005, w ktorych procesy eutrofizacyjne ulegly gwaltownemu spowolnieniu, a nawet odwroceniu (de-eutrofizacja) oraz; (iii) lata 2005–2011, w ktorych korzystne tendencje z lat 1995–2005 ulegly wyhamowaniu. W artykule poddano analizie przyczyny, mechanizmy i skutki zmian trofii jezior poludniowej cześci systemu WJM. Określono punkty krytyczne systemu decydujące o dynamice tych zmian. Wskazano potencjalne zagrozenia dla jakości wod WJM, a takze sformulowano szereg zalecen dotyczących ochrony ich zasobow wodnych oraz zlewni
Polish Journal of Ecology, 2013
Polish journal of microbiology, 2006
Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers ... more Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 micromol l(-1). Maximal potential ureolytic activity (V(max)) ranged from 0.2 to 7.0 micromol l(-1) h(-1). The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto- and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilim...
Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagroze... more Wobec braku w regionie duzych i uciązliwych dla środowiska zakladow przemyslowych glownym zagrozeniem dla wod powierzchniowych środowiska przyrodniczego Wielkich Jezior Mazurskich (WJM) jest ich postepująca eutrofizacja. Choc wzrost zyzności (trofii) jest przejawem naturalnej ewolucji wszystkich zbiornikow wodnych, to przyspieszona eutrofizacja poludniowej cześci systemu WJM obserwowana w drugiej polowie XX wieku byla efektem szeroko pojetej aktywności czlowieka. Tempo procesow eutrofizacyjnych jest funkcją ilości substancji biogennych zgromadzonych w ekosystemach wodnych. Analiza danych historycznych dokumentujących zmiany calkowitego stezenia fosforu (PT) w wodach poludniowej cześci systemu WJM pozwolila wyodrebnic trzy wyraźnie zroznicowane etapy ewolucji tworzących go jezior: (i) okres do roku 1995, charakteryzujący sie szybką eutrofizacja i, zwlaszcza w jego schylku, wystepującymi okresowo gwaltownymi zaburzeniami homeostazy wod jeziornych; (ii) lata 1995–2005, w ktorych proces...
Polish Journal of Ecology, 2013
Extracellular enzymes occur- ring in aquatic environment are heterogeneous in respect to their or... more Extracellular enzymes occur- ring 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' en- zymes produced by heterotrophic organisms in order to obtain organic carbon, and mostly 'phy- toplankton-bacterial-origin' enzymes, which are produced by autotrophic and heterotrophic or- ganisms, 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 ('finger- prints') calculated on the basis of activity of sev- eral 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 microorgan- isms present in these lakes. For the study we selected four l...
The heterotrophic activity of aquatic bacteria was measured by incorporation of 3H-thymidine, upt... more The heterotrophic activity of aquatic bacteria was measured by incorporation of 3H-thymidine, uptake of 14C-sodium acetate and mineralization of 14C-acetate. The temperature of water, oxygen content and concentration of chlorophyll a were also measured in the studied lakes. The obtained results of the studied processes in the surface layer and epilimnion were distinguished by negative correlation coefficients. A distinctive feature is the relation between chlorophyll a concentration in the water bodies and heterotrophic activity of bacteria. This indicates a negative dependence between these processes and phytoplankton activity in the photic zone. In contrast a positive relationship between phytoplankton activity and heterotrophic activity of bacteria was found in the metalimnion and hypolimnion of the studied lakes.
Polish River Basins and Lakes – Part I, 2019
One of the greatest threats to water quality is accelerated eutrophication, resulting from human ... more One of the greatest threats to water quality is accelerated eutrophication, resulting from human activity, like the high intensity of tourism, surface runoffs from fertilized fields, and municipal pollution. Water eutrophication manifests as excessive growth of phytoplankton caused by overabundant nitrogen, phosphorus, and other nutrient supply which causes deterioration of water quality related to the amount of bacterial biomass in eutrophicated water reservoirs. The Great Mazurian Lake System (GMLS) is a chain of lakes located in mesoregion of the Great Mazurian Lakes in the Northeastern Poland. All lakes of the GMLS are connected by natural or artificial channels built in the eighteenth and nineteenth centuries and nowadays create widely spilled, long (the easiest route from northern to southern edge is about 110 km) gutter unique on the scale of the continent. The lakes of GMLS are of glacial origin. During the last five decades, all lakes of the GMLS passed different levels of ...
Koniecznośc poprawienia przez Polske do roku 2015 stanu jakości wod powierzchniowych, jak rowniez... more Koniecznośc poprawienia przez Polske do roku 2015 stanu jakości wod powierzchniowych, jak rowniez coraz wieksza uwaga jaką spoleczności lokalne przywiązują do poprawy walorow krajobrazowych, rekreacyjnych i uzytkowych stawow, zalewow i jezior spowodowala w ostatnich kilku latach gwaltowny wzrost zainteresowania nie tylko ochroną lecz rowniez rekultywacją zbiornikow wodnych. Poniewaz glowną przyczyną zlej jakości ich wod jest przyspieszona eutrofizacja, dzialania rekultywacyjne skupiają sie przede wszystkim na ograniczaniu i likwidowaniu uciązliwych skutkow tego procesu. W artykule dedykowanym wszystkim zainteresowanym „leczeniem” chorych zbiornikow wodnych, a zwlaszcza urzednikom administracji lokalnej odpowiedzialnym za stan środowiska naturalnego gminy, powiatu czy wojewodztwa przedstawiono aktualny stan wiedzy dotyczącej teoretycznych podstaw roznorodnych technik rekultywacyjnych pozwalających na ograniczanie i czasowe cofniecie procesow degradacji plytkich ekosystemow wodnych. S...
This report describes the relationship between microbial enzymatic activities (aminopeptidase, es... more This report describes the relationship between microbial enzymatic activities (aminopeptidase, esterase, and alkaline phosphatase) and the trophic state index of the studied lakes. Pelagic surface water samples were collected from nineteen lakes (Mazurian Lake District, northeastern Poland), characterized by different degrees of eutrophication, during spring homothermy and summer thermal stratification periods in 1999 and 2000. Aminopeptidase and esterase activities of microbial assemblages in unfiltered water samples were positively proportional to the trophic conditions of the studied lakes and both enzymes significantly correlated with Carlson's trophic state index of lakes. No correlation between alkaline phosphatase activities and the trophic state index of the studied lakes was found. This study showed that the selected parameters of microbial activity are very useful for the rapid determination of actual trophic conditions in lake ecosystems.
This report describes the relationship between microbial enzymatic activities (aminopeptidase, es... more This report describes the relationship between microbial enzymatic activities (aminopeptidase, esterase, and alkaline phosphatase) and the trophic state index of the studied lakes. Pelagic surface water samples were collected from nineteen lakes (Mazurian Lake District, northeastern Poland), characterized by different degrees of eutrophication, during spring homothermy and summer thermal stratification periods in 1999 and 2000. Aminopeptidase and esterase activities of microbial assemblages in unfiltered water samples were positively proportional to the trophic conditions of the studied lakes and both enzymes significantly correlated with Carlson's trophic state index of lakes. No correlation between alkaline phosphatase activities and the trophic state index of the studied lakes was found. This study showed that the selected parameters of microbial activity are very useful for the rapid determination of actual trophic conditions in lake ecosystems.
Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers ... more Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 µmol l 1. Maximal potential ureolytic activity (V max) ranged from 0.2 to 7.0 µmol l 1 h 1. The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto-and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilimnetic water samples the bulk of the ureolytic activity originated from seston-attached bacteria. However, a positive, statistically significant correlation between ureolytic activity and chlorophyll a (Chl a) concentrations suggests that phytoplankton may also be responsible for at least a some of the observed ureolytic activity in the highly eutrophic Great Mazurian Lakes.