摘要:

AbstractThe microcrustacean and rotifer communities associated with submerged aquatic plants were studied over a three‐year period in a series of experimental ponds, created within a fenland drainage ditch. Seasonal abundance and spatial distributions were assessed. The ponds contained a varying amount of vegetation, dominated either byCeratophyllum demersumorStratiotes aloidesand this had consequences for the ponds' animal communities. Increasing densities ofCeratophyllumwere associated with increases in weed‐associated entomostracans whereas increases inStratiotesled to a general decrease in associated animals. Increases in both plant species led to reductions in abundance ofDaphnia, but to differing amounts. A relatively low density plant population in the presence of zooplanktovorous fish did not provide a refuge from predation for large‐bodied Clad

ISSN:0020-9309    

DOI:10.1002/iroh.19900750202

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractThe species composition, number, biomass and phosphorus excretion rate (PER) of zooplankton (Crustacea and Rotatoria) in 8 mesotrophic and eutrophic lakes were studied.PERwere calculated using specific expenditures on metabolism estimated from the oxygen uptake, phosphorus content in zooplankton and field observations of number and biomass of planktonic Rotatoria and Crustacea. The zooplankton biomass andPERincreased from mesotrophic to eutrophic lakes. The values ofPERwere compared with primary production and spring phosphorus concentration. The relative significance of zooplankton in phosphorus cycling declined with increasing trophic category of lakes.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750203

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractBy chemical analyses at the eutrophic Wallersee (Austria) a considerable precipitation of calcite during autumn overturn was found. It is a pure anorganic calcite precipitation, caused by the loss of free carbonic acid to the atmosphere during the mixing of epilimnic and hypolimnic water.An essential coprecipitation of phosphorus with the anorganic calcite precipitation could be shown by calcium and phosphorus balances and by SEM investigations.During the epilimnic biogenic calcite precipitation (in summer) phosphorus coprecipitation makes 0.19% of the calcium fallout. Phosphorus coprecipitation increases up to 0.42 % during the anorganic calcite precipitation when autumn overturn takes place. With respect to the total phosphorus sedimentation in the lake 25 % are coprecipitated with calcite.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750204

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractEnclosures open to the sediments and the atmosphere were used to elucidate the response of algae and bacteria to the nutrient enrichment from fish in the mesotrophic area of Lake Balaton. Active transformation between the forms of nitrogen was observed especially in the enclosure with fish. Both nitrogen and phosphorus values were influenced by fish. Changes in nutrient dynamics, composition and biomass of algae and bacterial production were measured. It has been shown that benthivorous fish with a biomass illustrative of the most eutrophic part of the lake were able to generate high bacterial production rate and a strong outburst of blue‐green

ISSN:0020-9309    

DOI:10.1002/iroh.19900750205

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo experiments (I and II) were performed in drainable ponds. Yellow eelsAnguilla anguilla(L.) were stocked in early June at three biomasses: 10, 20 and 60 kg · ha−1in experiment I; and 10, 20 and 40 kg · ha−1in experiment II. The mean body weights were 27.0 and 24.2 g respectively. Glass eels were stocked only in experiment II at equal densities of 1600·ha−1. In both experiments each biomass of yellow eel was combined in a factorial design with three cyprinid communities differing in biomass and in species‐ and size‐composition. The ponds were drained in autumn. The final body weights at draining ranged from 25.9 to 63.6 g for yellow eel and from 3.9 to 8.8 g for glass eel. The final body weights of yellow eel and of glass eel decreased with increasing biomass of yellow eel. No significant relation was found between the breamAbramis brama(L.) biomass and the growth of eel. The growth rates of yellow eel and glass eel were positively correlated in experiment II. At higher biomasses of yellow eel the percentage females decreased slightly. The recapture rates of yellow eel in experiments I and II amounted to 69.4 ± 9.8 % and 92.2 ± 4.9% (mean ±sd) respectively. The lower recapture rates in experiment I were caused by the inappropriate draining technique used. The glass eels were recaptured with 75.0·5.6% efficiency. The maximum net production of yellow eel occurred at a biomass of 20–40kg·ha−1and a

ISSN:0020-9309    

DOI:10.1002/iroh.19900750206

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractChlorophylladeterminations were made on lakewater and algal samples by spectrophotometric, fluorometric and high performance liquid chromatographic methods. Acetone, methanol and ethanol solvents were evaluated for their ability to extract photosynthetic pigments fromScenedesmussp. cultures. Routinely used methods overestimated the chlorophyllaconcentrations present in the samples. Significant differences resulted when various standard equations were used to calculate chlorophyllaconcentrations. Acetone did not quantitatively extract chlorophyll pigments, even after 24 h. Mechanical disruption was found to be important in assuring complete extraction of the chlorophyll pigments.

ISSN:0020-9309    

DOI:10.1002/iroh.19900750207

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractSea‐surface microlayer and underlaying water samples were collected in the Bay of Marseilles (France) in order to study respiratory activity of microneuston and its possible influence on respiratory CO2production.Three methods were tested: Biochemical Oxygen Demand (BOD) as an estimation of community respiration, Electron Transport System activity (ETS) and14C‐Glucose uptake monitored by14C‐CO2liberation.BOD and ETS data clearly showed enhanced respiratory activities (up to 310 μl O2/l/h) in surface‐films as compared to underlaying waters; moreover the slope of the linear regression between these data led to R/ETS value of 0.689 and provides evidence for the presence of an important heterotrophic fraction within the microneuston.Though14C‐Glucose measurements showed only a slight trend for higher total activity (incorporation + respiration) in surface microlayers, significant enhancement of relative14C‐CO2production giving rise to CO2diffusion across air‐water interfac

ISSN:0020-9309    

DOI:10.1002/iroh.19900750208

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractWet weight standing crop of macrobenthic invertebrates from the Palos Verdes Shelf, California showed several major fluctuations from 1972 to 1986, mainly due to the bivalveParvilucina tenuisculptaand the echiuroidListriolobus pelodes.From 1972 to 1986 mean biomass was 285 g/m2. When this value was compared with standing crop from other shelves, Palos Verdesstanding crop fell within the range documented for the tropics to higher latitudes. There was a small decline with increased effects ofEl Ninoin 1983. When Palos Verdes standing crop was compared to the biomass portion of the Pearson‐Rosenberg SAB curve, it was concluded that their model is probably not applicable on this portion of the shelf. Finally, the long‐term data base provided the opportunity to propose several hypotheses. These concerned the potential effect ofL. pelodeson species diversity and hydrogen sulfide in the sediment and the influence ofL. pelodeson excess standing c

ISSN:0020-9309    

DOI:10.1002/iroh.19900750209

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractThe authors investigated the mycoflora and the environmental factors in the River Czarna Hańcza (10 stations) and its tributary River Marycha (1 station) as well as Lakes Hańcza (2 stations) and Wigry (2 stations) on the occurrence of various aquatic fungi.At the stations investigated the presence of 45 aquatic fungi species was noted. The following fungi, up to now unknown in Poland, were found:Monoblepharis hypogyna, Rozellopsis inflata, Cladolegnia eccentrica, Apostemidium guernisaci, Anguillospora gigantea, Geniculospora grandis, Clavariopsis aquatica, Lemonniera aquaticaandLemonniera terrestri

ISSN:0020-9309    

DOI:10.1002/iroh.19900750210

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY

摘要:

AbstractFine Structure of the Club Cells (Alarm Substance Cells) in the Epidermis ofAstyanax mexicanusFilippi 1853 (Characinidae, Pisces) and its Cave Forms “Anoptichthys”The club cells in the epidermis ofAstyanax mexicanusare of the same ultrastructure as those in other Ostariophysan fish. There are also no essential differences to be found between the club cells of epigeanAstyanax mexicanusand its cave forms “Anoptichthys”. Our findings correspond to former statements in that the function of the club cells producing and releasing alarm substances has been maintained in the cav

ISSN:0020-9309    

DOI:10.1002/iroh.19900750211

出版商:Akademie Verlag, Berlin    

年代:1990

数据来源: WILEY