摘要:

SUMMARY.The relative importance of habitat structure and food availability to lake macro‐invertebrates was investigated experimentally. A gravel‐pit lake of uniform depth was partitioned into two parts and allochthonous material (straw) added to one half. Replicate litter bags of 0.3‐mm mesh size containing sisal string, straw, wood‐wool or polypropylene twine were added to each halt ol the lake in May 1980. After 2 months they were removed and the invertebrates within them identified and counted. Data were analysed statistically to determine the relative importance of bag Material and the level of allochthonous detritus in the vicinity of the bags (referred to as Food). Of the abundant taxa (>5 individuals per bag mean density) only Chironomuswas distributed independently of Material. The other abundant taxa(Gammmrus. Asellus, CryptochirnomusandHelobdella stagnalis)were all more strongly influenced by Material than Food. The effect of Material on total numbers was 14 times more important than that of Food. Of the 17 taxa analysed, onlyPisidiumwas distributed Independently of either faetor.The relative abundance of total taxa was lowest in the sisal bags and greatest in the polypropylene and wood‐wool bags. This is presumably related to structural properties of these materials with high abundance coinciding with an open buoyant substratum similar to that provided by aquatic macrophytcs. The importance of Material for most taxa indicates that the structural properties of the habitat may be very significant in determining animal dis

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00634.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SUMMARY.The benthic fauna of a small headwater stream in the Amazon drainage in Ecuador was studied from August 1976 to July 1977. The sampling station was at an altitude of 3300 m in a typical paramo habitat of constant and cool temperatures. The fauna is dominated numerically by Hydracarina, Insecta, Copepoda and Oligochaeta, The major insect groups are Ephemeroptera, Plecoptera, Trichoptera, Elmidae (Coleoptera) and Chironomidae (Diptera). Benthos densities followed a bimodal pattern of rapid decreases and intervening gradual recoveries; similar patterns occur in most taxa, but are more pronounced in smaller animals such as Copepoda and Hydracarina. An analysis of the size‐frequency distribution of three species of mayfly, two of stonefly and six of caddisfly suggest non‐seasonal life‐cycles except forAnacroneuriasp. Spates are thought to be the major factor regulating benthic densities in such non‐seasonal envir

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00635.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SUMMARY.The distribution of twenty species of Naididae found in seventeen lakes in North Wales and Shropshire is described. Fewer species were observed in the mountain lakes in Snowdonia in comparison to the more productive lakes of Anglesey and Shropshire.Substrate was an important factor influencing the distribution of naids within lakes, A small number of sexually mature individuals was found in more productive lakes in the summer and autumn months. Sexually mature individuals ofStylaria lacustriswere cultured in the laboratory; the population doubled its numbers, by asexual reproduction, in 12 days at 15°C. In Llyn Coron a natural population of S.lacustrisdoubled its numbers in 40 days. The gut contents ofS. lacustrisconsisted of periphyton

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00636.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SUMMARY.Measurements of the rate of oxygen uptake in a number of blue‐green algae and diatoms were carried out under both field and laboratory conditions to determine the effects of light on such rates. The light history of algal cells was an important controlling factor of oxygen uptake. When measured in the light, with dichlorophenyl‐dimethylurea (DCMU), oxygen uptake was sometimes different from uptake measured in the dark. The results cast some doubt on the validity of the light and dark bottle method for determining primary productivity. It is suggested that oxygen uptake measurements should be made in the presence of D

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00637.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SUMMARY.A population of the isopodAsellus aquaticuswas studied for sixteen months in the organically polluted River Ely. South Wales. There were two complete generations each year. The overwintering population released young (the spring‐brood) over the period April‐June. These animals in turn produced their own offspring (summer‐brood) in late July‐October. Each generation died after breeding and the overwintering population was comprised entirely of animals from the summer‐brood.Seasonal patterns of mortality were related to water flow, temperature and life‐cycle stage. Individual growth rates were affected by both temperature and life‐cycle stage.Annual population production (P) was 195.68 g wet wt m‐2, mean annual biomass (B) was 32.98 g wet wt m‐2and the annual P

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00638.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SUMMARY.A model describing the deposition of algae in a turbulent environment is outlined, it being assumed that all algae falling on the bed are trapped there forever. Its main features are that, above a certain threshold of turbulence the rate of deposition is independent of the turbulent intensity, and the rate of algal loss by sedimentation, in such conditions, is described by a first order kinetic equation. The hydraulic conditions under which algae settle at their intrinsic, still‐water rate and those for which the model is applicable, are examined. Some ecological implications of the model are discusse

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00639.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SUMMARY.The composition of bulk (wet and dry) precipitation in 1975 and 1976 was similar to that found 22 years previously. In 1975, mean values for nine precipitation samplers at one site (Wraymires) ranged from pH 4.3 to 4.5; similar values were obtained in 1976. Samplers covered with fine‐mesh plastic gauze caught substantially more Ca2+and K+than open samplers, but pH and SO2‐4+ NO3‐concentrations were similar in open and covered samplers. In precipitation, c. 50% of H+was balanced by NO3‐and c. 50% by SOi; 80% of the SO2‐4was balanced by Ca2+and Mg2+.Conccntrations of major cations (H+, Na+, K+,Ca2+, Mg2+) and anions (CI‐, NO3‐SO2‐4and alkalinity [Alk—largely HCO3‐]) in upland water‐ bodies were similar to those found in precipitation, but pH levels were generally higher and above 6.0 m some tarns. At lower altitudes, on base‐rich roeks and soils, Ca2+and Alk become dominant. Results of a survey of lakes and tarns in 1974–78 are compared with a survey in 1953–56 and published data (chiefly for pH and Alk) for 1947–50, 1932 and 1928. Comparisons are also made with other measurements of Alk in three productive lakes (Blelham Tarn, Esthwaite Water and Windermere) for 1936–39 and 1945–80. Winter levels of NO3‐N, PO4‐P and Si are given for these lakes; although the first two have increased during the late 1960s and the 1970s there has been no significant change in the last. NO3‐and probably some SO2‐4. In productive lakes a substantial (c. 50%) rise in mean Alk occurred during the late 1960s and the 1970s, possibly related to increased winter levels of NO3‐N and PO4‐P derived from sewage and fertilizers. In this period the maximum pH levels reached in summer were notably high, sometimes exceeding pH 10. The rise in Alk, conductivity and pH of surface waters is influenced by climatic factors (a decade of drier years), sewage input and biological productivity within the lakes.Considerable seasonal fluctuations in the concentrations of major ions, a characteristic feature of surface waters in the English Lake District, are illustrated and some implications for cation‐anion balance briefly discussed. Mid‐winter concentrations are usually high forNa+, K+, Cl‐. NO3‐and low for Ca2+, Mg2+, Alk. SO2‐4.Alkalinity. pH and conductivity of Lake District tarns and lakes show no signs of acidification during the period 1928–80. On the contrary, productive lakes have become more alkaline and some unproductive low‐alkalinity (<100 μ‐equiv. 1‐1) lakes also show signs of alkalization, with inc

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00640.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Book reviewed in this article:Vogel, S. (1981)Life in Moving Fluids: the Physical Biology of Flow.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00641.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1982.tb00642.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY