ISSN:0020-9309    

DOI:10.1002/iroh.19910760102

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractWe examined reproductive responses of the cladoceranDaphnia parvulato algal assemblages from the Potomac River, during and after Cyanobacterial blooms. Algal assemblages were manipulated by filtration, dilution, or additions of nutritious algae, in order to determine causes for growth inhibition. There was no evidence for lethal toxic effects or food limitation of population growth rates during the algal bloom, although growth was food limited later in the year. However, growth rates were lower in the experiment conducted during the Cyanobacteria bloom than in later experiments, and the results suggest an inhibitory factor associated with the particulate material. Results from filtered treatments indicate that picoplankton present in hypereutrophic waters can supportDaphniagrowth and reproduction.

ISSN:0020-9309    

DOI:10.1002/iroh.19910760103

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractThe zooplankton community in the highly eutrophic Lake Kasumigaura was investigated and its relation to a bloom ofMicrocystiswas analyzed. The zooplankton community was dominated by small cladocerans, whose biomass and production became highest in summer, whenMicrocystisbloomed. The high cladoceran production is considered to depend on the production of colonialMicrocystis, because the production of nannoplankton was apparently too low to ensure the cladoceran production.Microcystiscells were unsuitable as food for the cladocerans inhabiting Lake Kasumigaura, but became utilizable when decomposed. DecomposedMicrocystismay be the main food for Cladocera in the lake in summer. High water temperatures occurring in summer probably promoted decomposition of theMicrocystis, leading to increased production of the small cladocerans.

ISSN:0020-9309    

DOI:10.1002/iroh.19910760104

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractIngestion rates where estimated for daphnids,Cyclopsspp. andBosmina (Eubosmina) coregoni thersitesfed hepatotoxic and non‐toxicM. aeruginosaeither separate or mixed with the readily available food algaAnkistrodesmus falcatus. The ingestion rates of hepatotoxic strains ofM. aeruginosaare very low compared with those ofA. falcatusor non‐toxicM. aeruginosaHUB 5‐3 fed toDaphnia magnaorD. longispina. However, a close relationship between ingestion rate of differentM. aeruginosastrains and their toxicity could not be observed. Addition of the toxic strainM. aeruginosaHUB 5‐2‐4 reduces the ingestion rates ofA. falcatusprogressively due to increased food rejection byD. magna. Additionally, the assimilation efficiency ofM. aeruginosaHUB 5‐2‐4 is two times lower compared withA. falcatusandM. aeruginosaHUB 5‐3 leading to st

ISSN:0020-9309    

DOI:10.1002/iroh.19910760105

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractThree strains ofMicrocystiswhen supplied toDaphniain mixtures withScenedesmusdiffered in their power to inhibit filtering rates. The axenic strain PCC 7806 had the strongest effect (93% inhibition with 50%Microcystisin the food). This strain was toxic to daphnids sinceDaphniadied faster under these conditions than without any food. Strain PCC 7806 also exhibited strong toxicity against mice (LD5022 mg/kg). When the toxicity againstDaphniaand mice was tested with cells ofMicrocystisPCC 7806 which has been subjected to various extraction procedures, the extraction of freeze‐thawed cells with water slightly reduced the mouse toxicity, eliminatedDaphniatoxicity and reduced the inhibition of the filtering rate. After treatment with a lipophilic solvent, the cells of PCC 7806 still showed low mouse toxicity, but no longer inhibition of the filtering rate and no toxicity toDaphnia. Thus, our data suggest thatDaphniatoxicity and inhibition of the filtering rate are caused by different compounds, but we cannot rule out the possibility that the factors toxic to mice and inhibitory to the filtering rate are identica

ISSN:0020-9309    

DOI:10.1002/iroh.19910760106

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractSummer blooms ofAphanizomenon flos‐aquaevar.flos‐aquaeaccompanied by dense populations ofDaphniawere common in fish ponds of the district Blatná in 1950s‐1960s. Changes in management (increased stocking densities, decreased usage of superphosphate as fertilizer) made this type of plankton less frequent. The present study documents this trend and suggests explan

ISSN:0020-9309    

DOI:10.1002/iroh.19910760107

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effect of toxic and of filamentous blue‐green algae on feeding and population growth of the rotiferBrachionus rubenswas investigated in laboratory experiments. A toxic strain ofMicrocystis aeruginosawas ingested, but rotifers cultured withMicrocystisdied faster than nonfed controls. The rigid filaments ofCylindrospermopsis raciborskiiwere not ingested, reduced the ingestion of simultaneously offered algae, and depressed population growth rates. The soft filaments ofAnabaena flos‐aquaewere ingested at a moderate rate, did not reduce ingestion of other algae, and were used as an additional food in population growth experime

ISSN:0020-9309    

DOI:10.1002/iroh.19910760108

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractNauplii and immature copepodites ofBoeckella triarticulata, B. hamataandB. dilatatawere tested for their ability to survive and grow on monospecific diets of four species of filamentous cyanobacteria,Cyclotella (Cy)andCryptomonas (Cr)at 2 mg dry weight 1−1.Crsupported the development from nauplius to adult of all three calanoid species; complete development on other diets occurred only inB. dilatataonCyandAnabaena oscillarioides (Ao). Differences between nauplii and copepodites ofB. dilatataandB. hamatain survivorship and development on diets ofCy, Anabaena flos‐aquae (Af), AoandNostocsp. 2 (N2) imply ontogenetic shifts in resource utilization with developmental phase. Ranked in order of their ability to support the development of juvenile boeckellids the foods wereCr>Cy>Ao>N2>Af>Nostoc calcicola= no f

ISSN:0020-9309    

DOI:10.1002/iroh.19910760109

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractBy means of laboratory experiments and field investigations in Lake Zürich, the influence of extracellular algal products on the surface tension of water was investigated. Of interest to us was the question of whether a reduction in the surface tension, i.e. surface pressure, is dependent on (i) algal species or phytoplankton and phytoneuston community, (ii) the growth phase of the species or community concerned, and (iii) the abundance or concentration of phytoplankton and phytoneuston biomass. A dependence was ascertained in the case of the first two points. The laboratory experiments showed that extracellular products originating from diatoms give rise to a distinctly higher surface pressure than those originating from green and blue‐green algae; and that the change in surface pressure occurs during the later part of the stationary algal growth phase. In Lake Zürich, high values of surface pressure were measured at the time of the collapse of the diatom bloom, and comparatively low values during the period of dominance of the blue‐green algaOscillatoria rubescensin the winter months. Changes in surface pressure established during the course of a year can thus be explained partly in terms of the phytoplankton and phytoneuston succe

ISSN:0020-9309    

DOI:10.1002/iroh.19910760110

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY

摘要:

AbstractWaigani Lake, near Port Moresby, Papua New Guinea and Barton Broad, Norfolk, England are both shallow lakes nutrient‐enriched from sewage effluent disposal. In Waigani Lake phytoplankton biomass varied seasonally with lower levels (100‐200 mg chlorophyll α m−3) during the wet season increasing to over 400 mg chlorophyll α m−3at the end of the dry season. Secchi disc depths varied between 0. 11 and 0. 34 m. Phytoplankton productivity in Waigani Lake was very high throughout the year (range:Amax4,370‐21,000 mg O2m−3h−1) but production was lower during the wet season (range:Amax4,370‐12,700 mg O2m−3h−1). High surface productivity was recorded from August to December except on sampling days when the weather was overcast. Productivity throughout the year declined rapidly with depth. Algal biomass in Barton Broad varied from 3‐10 mg chlorophyll α m−3in winter but increased in spring and was very high in summer (200‐500 mg chlorophyll α m−3). Secchi disc depth varied from 0.21 m in August 1976 to 1.76 m in December. Phytoplankton production in Barton Broad was low in winter (range:Amax247‐1,250 mg O2m−3h−1) but increased markedly in spring and summer with the highest rate (Amax6,850 mg O2m−3h−1) being recorded in August. Surface inhibition was observed during summer except when the weather was overcast. Seasonality in nutrients and phytoplankton in Waigani Lake appear to be related to rainfall. Nutrient concentrations in Barton Broad are more closely related to phytoplankton activity which, in turn, corre

ISSN:0020-9309    

DOI:10.1002/iroh.19910760111

出版商:Akademie Verlag, Berlin    

年代:1991

数据来源: WILEY