Wyniki wyszukiwania - Biblioteka Nauki

1

Nanoflagellates in the Gdańsk Basin: coexistence between forms belonging to different trophic types

100%

Rychert K.

Oceanologia

|

2006

|

tom 48

|

nr 2

EN

Nanoflagellates are important bacterivores, but their role is often underestimated because forms capable of phagotrophy and containing chlorophyll (mixotrophs) are excluded from analyses. Research conducted in the coastal zone of the Gdańsk Basin (Baltic Sea) revealed seasonal changes in the relationship between the biomasses of small (1–8 μm) nanoflagellates with (NFChl+) and without chlorophyll (NFChl–). Three distinct patterns were distinguished: (i) spring, when the biomass of NFChl+ was lower than that of NFChl–, (ii) summer and autumn, when NFChl+ were dominant (about 90%), and (iii) late autumn and winter, when the prevalence of NFChl+ was lower (71–79%). Additional studies showed the existence of spatial differences in the composition of the nanoflagellate community. These spatial differences were not shaped by freshwater input. The possible importance of mixotrophic forms in the Gdańsk Basin is discussed.

2

Biomass distribution and dynamics and food web relations in psammon community of a eutrophic lake

84%

Kalinowska K. , Ejsmont-Karabin J. , Gorelysheva Z. , Rybak J. I.

|

tom 60

|

nr 3

EN

Organisms living in submerged sand along the shore and below the water’s edge in freshwater lake beaches create community called hydropsammon (see Fig. 1 in Preface). Trophic relations between psammon food web components are essential in energy flow, nutrient cycling and functioning of aquatic environments. The seasonal changes in algal, bacterial, nanoflagellate, ciliate, rotifer and crustacean biomass were investigated in hydroarenal (submerged sand) of the eutrophic Lake Mikołajskie (Poland). Sampling cores were taken once or twice a month since April till October 2005 from three layers: adjacent water layer (AWL), layer of water and sand from the transitory level (EPIH – epihydroarenal) and slice of sand (ENDOH – endohydroarenal). The meanannual phytopsammon biomass was extremely high in all microlayers. Bacterial biomass was the highest in the ENDOH. Biomass of nanoflagellates was 4 to 8 times lower than that of bacteria and was the highest in the AWL. The highest mean annual biomass of ciliates was recorded in the EPIH, whereas rotifers dominated in the ENDOH. In contrast, average biomass of Crustacea was the highest in the AWL. Crustaceans dominated heterotrophic biomass in the AWL and EPIH (92 and 54% of the total biomass, respectively) whereas bacteria definitely prevailed in the ENDOH (57%). The ratios of autotrophic to heterotrophic biomass and prey to predator biomass as well as trophic relations between the studied groups of psammon organisms differed clearly among microlayers. The AWL was characterised by the lowest autotrophic/heterotrophic and predator/prey biomass ratios (about 2) and significant positive correlations between nanoflagellates and ciliates as well as between protists and both rotifers and copepods. The highest autotrophic/heterotrophic and predator/prey biomass ratio (14 and 40, respectively) and lack of correlations was found in the ENDOH. These results may suggest that the pressure of consumers was weaker in the hydroarenal layers than in the AWL. In addition, it seems that psammon ciliates, rotifers and crustaceans inhabiting the ENDOH were probably limited by factors other than food availability. In contrast to the pelagic ecosystems, autotrophic biomass exceeded heterotrophic biomass, especially in the ENDOH.

3

Bacteria, nanoflagellates and ciliates as components of the microbial loop in three lakes of different trophic status

84%

Kalinowska K.

Polish Journal of Ecology

|

2004

|

tom 52

|

nr 1

EN

The major components of the microbial loop (dissolved organic carbon, bacteria, nanoflagellates and ciliates) were examined in three Polish lakes (Masurian Lakeland, North-Eastern Poland): highly eutrophic (Lake Ryƒskie), mesotrophic (Lake Kuc) and humic, acid (Lake Smolak Du˝y). Microbial loop was distinctly differentiated among studied lakes. In the eutrophic lake, the microbial loop was characterized by a wide variety of biotic components, great taxonomic, trophic and size differentiation of ciliates (dominated by bacterivorous and predatory taxa). Probably, in this lake autochthonous dissolved organic carbon (DOC) prevailed. In the mesotrophic lake, the microbial loop comprised fewer components and the taxonomic and trophic variability of ciliates (dominated mainly by bacterivorous and algivorous taxa) was smaller. This lake contained almost the same amount of DOC, but part of it was probably less available and allochthonous origin. Much of the DOC in the humic lake being poorly available (humic substances prevailed) and hence there were lower densities of bacteria and still lower of nanoflagellates and ciliates (dominated by large-sized mixotrophic and small- -sized bacterivorous species). The only significant correlation between bacteria and ciliates suggests that the food chain in this lake is short and that the high concentrations of DOC of allochthonous origin are not readily assimilated. Additionally, low pH values restricted growth of the studied groups of organisms and decomposition of DOC by bacteria. The number of significant correlations differed among lakes and in different temporal scales. In the eutrophic lake the relationships were stronger in both seasonal and diel cycle. Practically no relationships were found in the humic lakes in both scales. Generally, diel correlations were stronger than those in the seasonal scale.

4

Particle size selectivity of two marine ciliates - Balanion comatum Wulff and Strombidium sp.

67%

Rychert K.

Polish Journal of Ecology

|

2008

|

tom 56

|

nr 2

251-257

EN

Food selectivity of marine ciliates Balanion comatum Wulff and Strombidium sp. (mean size of cell 19 μm) were studied in situ during incubation with wheat starch particles as a surrogate food. Range of particles ingested by Balanion comatum was 1.25–7.50 μm with preference for 3.75 μm particles (statistically significant result). Strombidium sp. engulfed particles ranging from 1.25 μm to 5.00 μm also with preference for 3.75 μm particles. In the Baltic Sea size range of particles preferred by both ciliates is dominated by nanoflagellates.

5

Autotrophic versus heterotrophic production and components of trophic chain in humic lakes: the role of microbial communities

67%

Jasser I. , Kostrzewska-Szlakowska I. , Ejsmont-Karabin J. , Kalinowska K. , Weglenska T.

Polish Journal of Ecology

|

2009

|

tom 57

|

nr 3

423-439

EN

The ratio and rates of autotrophic and heterotrophic pathways of organic matter cycles constitute the basic functions of aquatic ecosystem and humic lakes are unique in this respect. The autotrophic and heterotrophic production, the food web structure and the role of microbial communities in three humic lakes (area 1.3–9.2 ha) were studied. The abundance of bacteria, autotrophic picoplankton (APP), nanoflagellates (NF), ciliates, phytoplankton, rotifer and crustacean zooplankton as well as chlorophyll a and primary (¹⁴C method) and bacterial production (³H–thymidine method) were measured. The lakes differed in humic matter content, water colour, pH and hydrology. Two lakes were acidic (pH 5.2–4.9) with different dissolved organic carbon (DOC) content: oligo/mesohumic – 7.1 mg C L⁻¹ , and polyhumic lake – 21 mg C L⁻¹. Due to draining of surrounding meadows, the third lake – formerly humic – experienced changes in the hydrological regime together with liming and fertilisation. Despite low DOC, the oligohumic lake resembled a low productive, typically humic, acidic lake with dominating bacterial production. The lake was characterised by the highest crustaceans biomass and very variable chlorophyll a concentration (between 1.5 and 71 mg Chl a m⁻³). The polyhumic lake had the highest mean and maximal chlorophyll a content but the lowest crustacean biomass, and functioned more like a eutrophic lake. The formerly humic lake had lost probably most of its humic features and experienced a eutrophication process that resulted in a food web structure typical of a shallow eutrophic pond-like environment. The mean chlorophyll a concentration there was at the same level as in an oligohumic lake, but the variability was much lower. This lake can be considered as an example of the posthumic lakes abundant in the managed wetland regions. Microbial communities were numerous in both humic lakes, with bacteria prevailing in microbial biomass in the oligo-humic and APP in the polyhumic lake. In the former humic lake the microbial communities, especially APP, seemed to play a lesser role, while the whole planktonic food web was more balanced. The results demonstrated that uncontrolled drainage and reclamation of wetland can be detrimental to biodiversity of small, mid-forest lakes. Although biodiversity in almost all plankton groups was the highest in the posthumic lake but this lake lacked rare species typical of humic acidic lakes like: Gonyostomum semen, Dictyosphaerium sphagnale from phytoplankton or Holopedium gibberum from crustacean zooplankton. Instead eurytopic species, common in eutrophic waters, were present.