摘要:

SUMMARY.The life cycle ofPentapedilum uncinatumin the Tjeukemeer is briefly described. There are two generations of larvae per year in the mud substrate but only one generation per year in the sand substrate. Changes in chemical composition during the life cycle ofP. uncinatumare described, and the data indicate that such changes are not synchronized with particular larval instars but follow a predetermined development pattern for the production of an adult insect. Development appears to be the same in both male and female larvae which results in adult insects that have almost identical percentage composition of chemical substances, but proportionately greater growth in female larvae gives an adult insect that is almost twice as heavy as the male.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01433.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.The variation in the ratio (R) between cellular fluorescence of chlorophyll‐aand unit extractable chlorophyll‐awas examined with natural populations of phytoplankton and unialgal cultures. Photo‐inhibition ofin vivofluorescence was observed al high values of irradiance with natural populations and in algal cultures, except with blue‐green algae. If samples were dark‐adapted (<6 W m−2) before measurements were made, changes of fluorescence due to photo‐inhibition could be minimized. Measurements ofin vivofluorescence with dark‐adapted samples of phytoplankton, dominated by species showing large values of R, gave significant correlations (P<0.001) with determinations of chlorophyll‐aconcentration over periods of several weeks.The values for R for blue‐green algae were appreciably lower than for other algal groups. This, and their lack of photo‐inhibition effects at high irradiance values, are attributed to the association of most of chlorophyll‐awith photosystem I which fluoresces weakly compared to chlorophyll‐ain photosystem II. The significance of these findings for ecolog

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01434.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.Changes in bacterial populations and certain physical and chemical variables in Esthwaite Water between June and September 1975 were studied and compared with results obtained from 1972 to 1974 in the hypolimnia of Blelham Tarn and the Lund tubes. The counts of total bacteria ranged between 1 and 7 × 106ml−1and were highest in the anoxic hypolimnion. The bacterial genera examined in more detail constituted only a small percentage of this count and includedOchrobium(104ml−1),Naumanniella(103ml−1),Leptothrix(102ml−1),Planctomyces(103ml−1), andMetallogenium(102ml−1). The iron bacteria appear to grow best in the oxycline where there was not only sufficient oxygen for aerobic growth but also a plentiful supply of reduced iron.Planctomycesnumbers increased as the thermocline became depressed in September. The results from Blelham Tarn might be interpreted as further evidence of growth by iron bacteria in the absence of dissolved oxygen, but other explanations are possible. Examination of the results by multiple regression analysis showed that it was possible to explain a significant proportion of the bacterial variation (with the notable exception of thePlanctomycescounts) in spite of considerable intercorrelation of the regress

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.A total of 225 benthic samples was taken at various riffles along the Tongue River in Montana during three separate weekly intervals in 1975. For each sample, depth, current velocity, substrate microprofile, turbulence (Froude number), and the number and kind of species present were considered.The conditions of highest faunal diversity were 75–125 cm/s current velocity at 20–40cm depth. The optimum condition appeared to be 76 cm/s at a depth of 28 cm over medium cobble substrates.The centroids for optimum conditions of depth and current velocity for thirty‐six common macroinvertebrates are also presented.Representative diagrams of the tolerance ranges of some common invertebrate species are presented.Rhithrogena hageniEaton was chosen as the indicator species since its tolerances closely matched those of the highest community diversity. The presence ofRhithrogenain future samples would indicate maintenance of adequate flow conditions for the present benthic community.A method for applying these data to produce a minimum flow recommendation is discussed. If the optimum conditions can be plotted on composite hydrologic maps of depth and velocity in riffle areas at various discharges, one can predict the discharge at which the optimum conditions are eliminated and, thus, the recommended minimum disc

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.The effects of a sewage effluent in Moat Brook, Staffordshire, were determined from regular collections of water and biological samples from directly comparable stations above and below the sewage outfall.The eutrophic conditions below the outfall result in the replacement ofPolypedilum laetumbyChironomus riparius(except in the spring) as the dominant member of the Chironominae. Continuous recruitment of first instar larvae to the population ofC. ripariusin summer and autumn results in much overlap of generations, but emergence trap captures suggest at least five generations in the year.The usefulness ofC. ripariusas an indicator of enriched conditions in lotic ecosystems should be considered in relation to oviposition behaviour and the occurrence and seasonal variation in density of the adults and aquatic stages (including the more conspicuous third and fourth instar larvae).

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.In the summer of 1971 the village of Grasmere was converted from septic tank to mains drainage with sewage treatment at an activated sludge plant. The effluent was discharged into the River Rothay, the main inflow of a nearby small lake (Grasmere). This paper describes some of the effects on the lake. The mean areal hypolimnetic oxygen deficit increased from 274 to 434 mg O2m−2day−1with an accompanying marked increase in the degree of deoxygenation in the hypolimnion. Plate counts of bacteria in the surface water increased for 2 years but this increase was not sustained. The mean summer soluble reactive phosphorus concentration did, however, increase significantly (P= 0.05), but the same was not true of nitrate levels. This paper is particularly concerned with inorganic nitrogen transformations and analyses of the main inflow have shown that 50–98% of the ammonia and 10–40% of the nilrate entering in this river was derived from the sewage effluent. The concentrations in the main body of the lake were usually lower, possibly due to assimilation and denitrification in the shallower reaches of the lake. Seasonal changes in the inorganic nitrogen species in the hypolimnion showed three distinct phases of activity, ammonification, nitrification and denitrification. Nitrification accounted for approximately a quarter of the oxygen uptake in the hypo

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01438.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.The food of 0+ perch,Perca fluviatilisL. has been investigated in Windermere, the largest lake in the English Lake District. Whole guts and stomachs from 800 fish were investigated during four 24‐h periods between June and September in 1975 and in 1976. Ciliates, algae, rotifers and cyclopoid nauplii constituted the first food of larval perch in Windermere. Vertical samples were taken from the zooplankton, at the same time and in the same location where the fish were sampled, and the concentration of the different food organisms studied. Electivity of the different food organisms was studied from lvlev's index, which showed positive electivity, or selection for some organisms, e.g.Bosmina obtusirostris(Sars.) and copepods (both cyclopoid and calanoid), and negative for others such asDaphnia hyalina var. galeata(Sars.),Leptodora kindti(Focke) andBythotrephes longimanus(Leydig). In studying predatorprey relationships,Daphnia hyalinawas chosen as the ‘standard prey’, being the most abundant of all food organisms in the diet of young perch, also because its maximum body‐depth (carapace width (mm)) was among the largest of the cladocera and copepods in Windermere. Comparison of the maximum carapace width ofDaphniaeaten with that of the plankton revealed that smaller specimens were taken by juvenile perch in July, but they tended to select larger organisms during August and Se

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01439.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.Measurements were made of calcium, magnesium and eight trace elements (Cu, Zn, Fe, Mn, Ni, Pb, Cd, Co) in waters, sediment and biota at eight sites in the Upper Fly River, Papua New Guinea. Determinations from streams draining an area rich in copper ore showed relatively low values for soluble copper and this was attributed to the small amount of ore exposed to weathering, heavy rainfall and high pH of water associated with the limestone bedrock. More iron was transported in a soluble form down a headwater tributary (Alice River) than in the Fly River but higher iron concentrations were associated with particulate matter in the Fly than in the Alice. The geochemistry of the catchment and the distance from the headwaters were important influences on the amount of particulate iron and its distribution between soluble and particulate forms.Levels of metals in the biota generally reflected the background concentrations of metals encountered at each site. Concentrations of Cu, Cd, and Zn were lower in starved invertebrates compared with unstarved individuals but no consistent changes were observed in Fe or Mn content.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01440.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARY.Gammarus lacustris limnaeusSmith was fed decomposed autumnshed leaves of maple (Acer saccharumMarsh.) and poplar (Populus tremuloidesMichx.). Faecal pellets were collected at various time intervals after egestion and examined under a light and a scanning electron microscope. Nearly all the faecal pellets collected up to a period of about 7 h after egestion possessed a thin, tightly‐fitting peritrophic membrane while those that had been outside the gut of the animal for a longer time lacked a peritrophic membrane. Presumably, after egestion faecal pellets swell because of absorption of water leading to eventual rupture and loss of the membrane. The surface of newly extruded pellets is devoid of microbes and microbes seem to play a very insignificant role in the loss of peritrophic membrane from the pellet

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1978.tb01441.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY