Wyniki wyszukiwania - BazTech

1

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

|

2016

|

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.

2

Fading out of the trophic cascade at the base of the microbial food web caused by changes in the grazing community in mesocosm experiments

Jasser I., Kostrzewska-Szlakowska I.

Oceanological and Hydrobiological Studies

|

2012

|

Vol. 41, No. 1

1-11

EN

Biomanipulation of consumer populations can have strong top-down impacts on the composition and biomass of lower trophic levels. In this paper, we assess how changes in crustaceans' biomass influence classical grazing and the microbial food web in an oligo-mesohumic, low-pH lake (Mazurian Lake District, Poland). Removal of mesozooplankton from the experimental mesocosms created a gradient of crustacean biomass resulting in the biomass increase of rotifers, phytoplankton and protozooplankton, while autotrophic eukaryotic picoplankton (eu-APP) and bacteria were not affected. The strongest modifications concerned the rotifer biomass and phytoplankton community structure. Our results imply that the trophic cascade generated in the experiment did not extend to bacteria and eu-APP.

3

Experimental approach for studying interrelationships between macroarthropods, soil biota, decomposion rate of litter and organic matter accumulation in soil

Kajak A.

Polish Journal of Ecology

|

2000

|

Vol. 48, nr 4

263-269

EN

The paper presents experimental design applied to analyse the role of macroarthropods patrolling soil surface on decomposition rate of grass litter (Dactylis glomerata). In the experiment density of micro- and mesofauna and microbial abundance in mesocosms accessible (open - O) and not accessible (closed - C) for large arthropods was compared. Mass loss of litter, mineralization rate of carbon and nitrogen, humus acid storage in sandy substratum underlying litter was estimated also. Results are presented in several papers. Effect of exclosures on the intensity of surface patrolling by macroarthropods and on their density in mesocosms in also presented.

4

Environmental conditions and plant biomass in a field experiment : biomanipulation of macroarthropods

Szanser M.

Polish Journal of Ecology

|

2000

|

Vol. 48, nr 4

271-281

EN

Changes of environmental conditions in mesocosms differentiated in the accessibility for epigean arthropods (closed and open for animals) were compared on a meadow of the Arrhenatheretalia order. In general, moisture of the exposed litter and of the underlying substrate did not differ between the open and closed treatments. Plant biomass, considered as an index of the environmental conditions, did not differentiate the two mesocosm types, either aboveground (total and subdivided into dead and living) or belowground. The open mesocosms were characterised by higher weight of fragmented plant material and of invertebrate faeces than the closed treatment.