摘要:

SUMMARY.1. Monthly and diel patterns of food consumption by the three‐spined stickleback,Gasterosteus aculeatusL., were studied in Llyn Frongoch, a small reservoir in upland mid‐Wales.2. Copepods were particularly prominent in the diet in spring and autumn, with ephemeropteran nymphs prominent in summer. Chironomid pupae and stickleback eggs were also elements of the diet in summer, whereas algae, plant material and debris were more important in autumn and winter. Chironomid larvae and ostracods were present throughout the year, but there was some doubt as to the importance of ostracods as digestible food items.3. Stomach contents were heaviest in spring and late summer and lightest in late autumn and winter.4. Samples for the diel samples were taken four times, once in each season. These diel samples largely reflected the seasonal changes in diet noted in the monthly samples. There were few cases of a clear switch in the composition of the diet during a 24 h period. Feeding occurred during daylight, the weight of the stomach contents declined during darkness.3. Several methods provided estimates of the daily rate of food consumption which ranged from 3.5 mg in December (4°C), to 19.0 mg in May (15°C). These estimates and others obtained independently suggest that the annual rate of food consumption for a stickleback in Llyn Frongoch is between 2000 and 5000 mg wet w

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00158.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. The reliability of the simple frequency, Janetschek, Cassie and Dyar's law methods for determining or corroborating instars of mayflies and stoneflies was evaluated using data from published studies, a population ofBaetisca rogersiand populations simulated through use of random numbers and generated normal distributions.2. The Janetschek and Cassie methods are variations of the simple frequency method that offer no significant advantage. Modes of the Cassie method, thought to represent instars, are much more difficult or impossible to detect than are the corresponding peaks of the other two methods.3. Overlap in size between adjacent instars can lead to false instar peaks or modes in frequency plots. The potential for overlap in mayflies and stoneflies is greatly increased, compared to other insects, because of their large number of instars and known developmental variability. The normal distribution simulations demonstrated that instar size variability as low as 5–7.5% COV (coefficient of variability) may lead to false instar peaks when the number of instars is in the typical range. These simulations also indicated that even simple frequency plots with distinct peaks may result in inaccurate instar determinations.4. The number of size classes used in an analysis was correlated with the number of peaks or modes revealed. The number of peaks greater than zero in the Janetschek plots for theBaetisca rogersipopulation varied from 5 to 53 as the number of size classes was varied from 20 to 188. Similarly for the random number simulations. the number of peaks varied from 6 to 41 as the number of size classes varied from 22 to 127.5. Dyar's law semi‐logarithmic plots do not corroborate instars determined through frequency methods, because the uniform spacing of‘instar’data points is the direct result of the uniform spacing of peaks in frequency plots of most data sources (including random numbers), whether or not peaks actually indicate instars. Also Dyar's law plots will‘corroborate’different numbers of instars depending on the peak selection criteria used. The potential for corroborating instars through supplemental rearing and best‐fit analysis is discussed.6. The future of mayfly—stonefly instar determination lies in the increased and more rigorous application of the rearing and Palmen body (mayflie

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00159.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Quantitative fauna samples were taken from four differently structured vegetations in a ditch on three dates in the summer of 1980.2. Cluster analysis of twenty‐four samples showed that the vegetation pattern is probably the main factor in determining the spatial distribution of non‐benthic macro‐invertebrates in the ditch. Temporal heterogeneity arising from changes in the macro‐invertebrate fauna during the summer, however, appeared to be of at least the same magnitude as the observed spatial heterogeneity. Different vegetation types differed considerably in total faunal density. Species that are taxonomically related tend to have a similar distribution in th

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00160.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Rotenone was applied to Round Lake in the autumn of 1980 in order to eliminate predominantly planktivorous and benthivorous fish. The lake was subsequently restocked with a higher population density of piscivores. The effect of this biomanipulation on the phytoplankton and zooplankton communities and on total nutrient concentrations was monitored at fortnightly intervals during the summers, from May 1980 to September 1982.2. The abundance of phytoplankton was much lower after biomanipulation and was consistent with observed changes in Secchi disc transparency, total attenuation coefficient and chlorophyllaconcentration. Zooplankters were also less abundant in 1981 and 1982 but the decrease in numbers was more than offset by the large increase in the mean sizes of the zooplankters present, so that the estimated grazing pressures in 1981 and 1982 were at least double the 1980 value.3.Daphnia, rare in 1980, became the dominant genus in 1981 and 1982, and a shift to progressively larger‐bodiedDaphniaspecies was observed.4. Although total nitrogen and total phosphorus levels were generally lower after biomanipulation, their decline could not explain the reduction in phytoplankton abundance which was attributed to the increased grazing pressure. Possible causes of the observed declines in nutrient concentrations are discusse

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00161.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Newly‐laid eggs ofCoenagrion puella(L.) from a pond near Herzogenburg (Lower Austria) were kept at constant water temperatures (rangec.3.5°C toc.28°C)in the laboratory. Hatching success varied with temperature; no eggs hatched below 12°C and nearly all hatched atc.l6°C. Hatching time decreased with increasing temperature and the relationship between the two variables within the range 12–28 °C was well described by a power law. The length of the hatching period was less than 12 days. Hatching times estimated from the power‐law equations and those obtained in the field experiments were similar. Therefore both the hatching time and the length of the hatching period in the field could be estimated from the laboratory data for the range 12–28°C.2. The maximum number of instars from egg to imago was 11; the average body length increment (mm) per moult was proportionately constant atc.26% and Dyar's rule was applicable. The interval between moults decreased with increasing temperature up to the seventh instar and the relationship between the two variables within the range 12–28°C was well described by a power law. The moulting interval for instars 8–11 ranged from 23 to 48 days and was relatively independent of temperature. No moulting occurred at temperatures below 12°C.3. Larval growth was logistic in the laboratory and variations in mean logistic growth rate (range 0–2.5% length day−1) were related to mean temperature with no growth at temperatures<12°C. Larval growth rates in pond experiments were similar to those estimated from laboratory data, and therefore the regression equations obtained from the laboratory experiments are probably applicable to larval growth in the field.4. Information on the life cycle ofC. puellais briefly reviewed and it is concluded thatC. puellafrom the pond near Herzogenburg has

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00162.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. Diel depth distribution patterns ofCeratium hirundinellawere studied during eleven sampling periods, covering the seasonal growth cycle. They were shown to result from short‐term periodic or non‐periodic external factors, endogenous responses of the alga, and interactions between these.2. Diel variations in wind stress resulted in the net transport of algae into or out of the sampling position due to lateral water movements. A progressive surface accumulation ofCeratium, leading to a 3‐fold increase in cell numbers at the sampling site over a 24 h period, was due to wind‐induced upwelling of deeper cells. Near‐surface accumulation ofCeratiumon a completely overcast afternoon, similar to that associated with migrations, was attributable to advection.3. Under sufficiently calm conditions, depth‐differentiation ofCeratiumwas regulated by its vertical swimming movements with a diel periodicity. Migration patterns observed in earlier work were confirmed and extended. The alga migrated towards the surface during the daytime and downward during the night; this rhythm had an endogenous component.4. At high surface illumination, the alga retreated from the surface and formed discrete sub‐surface maxima; at low irradianceCeratiumshowed positive phototaxis and concentrated near the surface. Under either condition of irradianceCeratiumactively aggregated at depths associated with irradiance levels of about 125–155 μEinsteins m−2s−1. Downward movement was restricted by anoxic conditions and possibly by thermal/ density gradients. However, given sufficient light penetration, dissolved oxygen and nutrient availability, the thermal density gradient does not apparently eliminate downward

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00163.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.1. A simple and inexpensive assay was developed to determine the amount of biologically available phosphorus (BAP) present in freshwater.2. BAP was measured by usingAeromonas hydrophilain a proteolytic assay system in which the release of the chromogen from an insoluble azure dye derivative of hide powder (HPA) was determined spectrophotometrically. The time necessary to hydrolyse 50% of the HPA was found to be directly dependent on the amount of BAP present. BAP within the range 2–250 μg 1−1phosphate‐phosphorus was detected.3. Our data suggest that the application of this assay for the measurement of BAP in freshwater offers the potential of monitoring the biological response of a freshwater ecosystem to phos

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00164.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY.I. Movement of33P from hypolimnion to epilimnion in a small, dystrophic lake was investigated using small‐diameter experimental tubes enclosing thermally stratified water columns. This approach was made possible by the extremely sharp stratification found in such lakes, in which the euphotic zone closely coincides with the epilimnion.2. The vertical distribution of inorganic phosphorus in the lake showed a sharp increase across the thermocline so that enhanced concentrations were available to phytoplankton just below the thermocline. Inorganic nitrogen concentrations did not show such a marked relation to thermal stratification.3. One abundant motile alga (Cryptomonas marssonii) showed striking and regular vertical migrations in the lake, moving below the thermocline at night and returning to the surface waters in early morning. These migrations took cells across a 10°C temperature gradient. Non‐motile phytoplankton showed constant vertical distributions.4. In the experimental tubes an upward movement of phosphorus took place from hypolimnion to epilimnion which was only attributable to transport by phytoplankton cells undertaking active vertical migrations. No equivalent movement of phosphorus occurred in control tubes from which algae were absent.5. The possible significance of such nutrient retrieval is discussed with reference to plankton phosphorus budgets and competition between phytoplankton spe

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00165.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Book reviewed in this article:Fay, P.(1983)The Blue‐Greens.Petr, T.(Ed.) (1983)The Purari—Tropical Environment of a High Rainfall River Basin.Nisbet, B.(1984)Nutrition and Feeding in Protozoa.Frank, J.H.&Lounibos, L.P.(Eds.) (1983)Phytotelmata: Terrestrial Plants as Hosts for Aquatic Insect Communities.Elliott, J.M.&Humpesch, U.H.(1983)A Key to the Adults of the British Ephemeropt

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00166.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1984.tb00167.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY