摘要:

SUMMARY.1. Measurements of oxygen, pH, phosphate, nitrate, nitrite, hydroxylamine. ammonium and sulphide were made in four Ethiopian crater lakes during 1964, 1965 and 1966 at fairly regular intervals. The seasonal pattern of the dynamics of these chemical constituents is described for depth and time and relates closely to the pattern of thermal stratification and mixing previously described.2. Interactions between the chemical constituents are examined and comparisons are made between the four lakes which differ widely in their depth, exposure to wind and standing crops of phytoplankton.3. The vertical distribution of the chemical constituents is used to help define the limits of circulation of surface waters and the need to understand the seasonality of chemical stratification in relating climatic, morphometric and biological events, especially in tropical lakes, is stressed.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00176.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Gut contents ofMesocyclops edaxconsisted of rotifers. cladocerans, copepods and algae, the importance of each varying seasonally.2. Functional response experiments using two soft‐bodied rotifers as prey showed an increase in ingestion rate with increasing prey density up to a threshold, followed by a decline.3. Enclosure experiments with natural assemblages of prey from two lakes indicated thatMesocyclops edaxis a selective feeder and may ingest fifty or more prey per predator per day, accounting for up to 17% of the standing crop of its preferred prey species per day in natur

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00177.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Concentrations of cadmium are reported for twenty largely unpolluted freshwaters in north‐western England. They range from 15 to 117 ng l−1total Cd in the rivers and streams and from 18to51 ng l−1in the lakes, lying on the low side of values reported in the literature. The care required to obtain reliable data is stressed.2. A comparison is made between the fraction of Cd found to be particulate (>0.2 μm) and that which is calculated to be adsorbed on particulate matter. This provides further insight into the speciation of Cd, as well as a test of the application of a simple adsorption model to the prediction of the observed speciation.3.The adsorption model is found to be a poor predictor of the measured fraction of particulate Cd. Possible reasons for this are explored and the potentially important role of slow desorption kinetics is emph

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00178.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. The waters of Opi Lake were very dilute (15–24 μS cm−1at 25°C) and somewhat acid (pH 6.0–6.5), probably a result of the highly leached lateritic soils in its small drainage basin.2. Annual minimum water temperatures were recorded during the early dry season, not during the rainy season as has been observed in most other West African water bodies. This was attributed to the influence of the Harmattan winds on the lake and the absence of pronounced rainy season flooding, as might occur in reservoirs.3. A diel cycle of daytime thermal stratification and complete or near‐complete night‐time destratification occurred throughout the year.4. During the dry season, when prevailing winds were strong and lake depth shallow, night‐time destratification was accompanied by deep circulation. In the rainy season, when prevailing winds were weak and lake depth was greatest, deep vertical circulation apparently did not take place, as evidenced by anoxia in near‐bottom waters. This is the reverse of the pattern seen in many

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00179.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Concentration of total bacteria, and heterotrophic activity (as turnover rate for glucose assimilation), in the water of an intermittent spring‐fed calcareous headstream, increased with distance from the source to 1600 m.2. This increase was gradual rather than stepwise and might be due to release of bacteria from submerged vegetation and the stream bed, and to input of terrestrial bacteria with groundwater.3. The increment per unit length of stream was greatest in summer when aquatic vegetation was most abundant and discharge was low.4. When the stream was partly dry, isolated peaks of suspended bacteria occurred and there was no regular downstream increase.5. A lesser spring which upwelled into a natural basin consistently contained more suspended bacteria than the principal source, which was an artificial culver

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00180.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Laboratory and field data indicate thatCloeon trianguliferMcDunnough has at least three generations per year in White Clay Creek (Pennsylvania, U.S.A.).2. The duration of the egg stage ranged from 5 days at 30°C to about 90 days at 10°C.3. Larvae completed development (i.e. first instar to adult) in 27 days at 25°C, 45 days at 20°C, and 179 days at 10°C on an algal diet dominated by diatoms.4. Larvae reared on hickory leaves completed development in 30 days at 25°C but died prior to metamorphosis at 10, 15 and 20°C.5. Adult size (i.e. body length, wing length and dry mass) and fecundity were inversely related to rearing temperature for all laboratory and field experiments.6. The significant interaction of food quality and temperature suggest that these factors may be important in understanding geographic variation in the life history ofC. triang

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00181.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Natural population sinking rates were calculated by fitting an exponential regression to 6 years’observations on declining crops ofMelosira italica subarcticaO. Müll. andStephanodiscus astraea(Ehr.) Grun.2. Losses were described by an exponential model which yielded still water sinking rates of 0.86 md−1forM. italicaand 0.45md−1forS. astraea.3. Laboratory measurements of the sinking rate of natural populations showed that the rate increased abruptly from less than 0.2 m d−1in growing populations to 0.4 m d−1after silica depletion.4. The measured sinking rate ofS. astraeaagreed well with that observed in the field. Where as populations ofM. italicaappeared to sink more quickly in the lake than could be accounted for by laboratory ob

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00182.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Spine development in a clone of unspinedKeratella cochleariswas promoted by a water soluble factor released by the copepodsTropocyclops prasinusandMesocyclops edaxand by the predatory rotiferAsplanchna priodonta.Between 9 and 55% ofK. cochlearispopulations cultured in predator‐conditioned media responded to the inducing chemical.2. TheK. cochlearisform possessing a posterior spine of medium length was much less susceptible to predation by smallTropocylopsandAsplanchnathan the form lacking the posterior spine. These predators consistently selected the unspined form over the spined form when offered equal densities of each. However, both spined and unspined forms were equally susceptible to predation by largeMesocyclops.3. The phenotypic variation of offspring produced from induced unspinedKeratellafemales encompassed much of the variation reported for the taxon in North America. These morphotypes are similar to the variation of forms reported for theK. cochlearistecta series known from Europe. We suggest that the North American morphotypes be identified in studies of this species because the presence of the posterior spine can greatly affect predator selectivit

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00183.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. The microdistribution of three species of insect predators in a Swedish stream was assessed using a multivariate statistical approach. Both abiotic factors and factors pertaining to the prey community were included in the analysis.2. The factors most strongly correlated to the distribution of largeDinocras cephaloteswere the densities of case less caddis larvae (Wormaldiasp. andHydropsyche siltalai) and the median weight of stonefly prey. For smallD. cephalotes, the density ofH. siltalaiand the percentage of moss cover were most important.Isoperla grammaticashowed a significant correlation to blackfly density.Rhyacophila nubilaoccurred predominantly in patches with high prey biomass and with high densities and median weight of case less caddis larvae.3. It was concluded that the quantity and quality of the prey, such as size, availability and species, influenced the predators’microdistribution. The distributional pattern differed between species of predators and was probably related to their different hunting strategie

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00184.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Book reviewed in this article:Carmouze, J.P., Durand, J.R.&Leveque, C. (1983)Lake Chad. Monographiea BiologicaeSaether, O. A. (1980)Glossary of Chironomid Morphology Terminology (Diptera: Chironomidae).Ashe, P. (1983)A Catalogue of Chironomid Genera and Subgenera of the World including Synonyms (Diptera: Chironomidae).Wiederholm, T. (Ed.) (1983)Chironomidae of the Holarctic Region. Keys and Diagnoses. Part L Larvae.Saether, O.A.&Sublette, J.E. (1983)A Review of the Genera Diothrix n.gen., Georthocladius Strenzke, Parachaetocladius Wülker and Pseudorthocladius Goetghebuer (Diptera: Chironomidae, Orthocladiinae)

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00185.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY