bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectral intensity in some Scottish freshwater lochs
Authors: SPENCE D. H. N. , CAMPBELL R. M. , CHRYSTAL J. 
Published: May 2006

SummaryIn the course of investigations on the ecology of submerged aquatic macrophytes a narrow‐bandwidth spectroradiometer has been used to measure underwater spectral intensity (390–750 nm) in a series of lochs approaching the extremes in optical and chemical properties of Scottish fresh waters. Cosine response and immersion‐effect properties of the collector were determined in the laboratory with a colUmated hght source. Diffuse attenuation coefficients, Ee, ranged from 0·55 in Loch Croispol, a calcareous loch, to 2·9 in Loch Leven, a lowland eutrophic loch. Underwater spectral intensity (1 m) relative to subsurface values show a proportional increase in short‐wave radiation in the blue‐green water of Loch Croispol, while the converse is true of the peaty brown water of Loch Uanagan. Attenuation coefficients were derived over 25 nm wavebands in Lochs Croispol, Leven and Uanagan. The water in the latter two lochs is optically similar although Leven is rich in phytopiankton and has an extinction peak at 675 nm. Uanagan represents the brown‐water type of loch most common in Scotland. Loch Croispol has attenuation coefficients for shorter wave‐lengths at least ten times lower than the other two lochs and only approaches their values at 750 nm. Croispol resembles Crater Lake, Oregon. The colour range at the maximum colonizable depths by rooted macrophytes of brown (Uanagan 4 m) to blue‐green (Croispol 6 m) water is equivalent to 196·0 and 230·6 kJ/Einstein (48·2 and 55·6 kcal/Einstein). Red/far‐red ratios even in plankton‐rich water (Leven) were at least three times the value for sunlight (1·3) and within the total photic zone reached three‐figure proportions. Possible implications for light‐sensitive seeds of aquatic species and for morphogenesis and zonation are discussed.
Molecule‐size distribution of soluble hiunic compounds from different natural waters
Authors: DE HAAN H. 
Published: May 2006

SummaryIt this study the use of Sephadex G‐25, Sephadex LH‐20 and CPG‐10‐75 for the separation of soluble humic compoutids frotn fresh water is tested.It is shown by Sephadex G‐25 gel filtration that differences in molecule‐size distribution of soluble humic compounds in one lake at different titnes and between lakes can be predicted by E250 and E365 measurements.
Further studies on the occurrence of freshwater Microturbellaria in the British Isles
Authors: YOUNG JOHNSTONE O. 
Published: May 2006

SummaryMacrostomwn johni sp. nov. from Llyn Cwellyn, N. Wales is described. The species has been recorded from the vegetational littoral in December and February only. The main distinguishing criterion is the penis stylet which consists of a funnel, about 80‐98 μm in length in slightly squashed specimens, curved in two planes and with a sub‐terminal distal opening, the distal end is blunt and cowl (hood) shaped. Other features include the presence of sensory hairs and rhabdoids all over the body, ‘Haft‐papillen’, and eyes. Rhammite tracks are weakly developed. The testes are elongate and the ovaries are compact, though slightly indented, and smaller than the testes. A very short ductus intervesicularis is present. The vagina is short. A ‘Verschlussap‐parat’ is present but poorly developed.
The use of acetone and methanol in the estimation of chlorophyll in the presence of phaeophytin
Authors: MARKER A. F. H. 
Published: May 2006

Summary(1)Where grinding or maceration of plant tissue is impractical, immersion in methanol should be used.(2)The adaption to aqueous methanol of existing techniqus for distinguishing chlorophyll and phaeophytin in aqueous acetone was studied in detail. In methanol the spectra of both phaeophytin a and b were found to be pH sensitive. A method developed involving changes in absorbance at 665 nm is less precise than similar methods using acetone.(3)The spectra of phaeophytin b in methanol at different pH levels are anomalous. Changes in absorbance between 440 and 410 nm cannot be used for the estimation of phaeophytin.(4)Plant pigments can be transferred from methanol to aqueous acetone without degradation of chlorophyll. Modified standard techniques may then be used to measure chlorophyll a and phaeophytin a content.
The biology of Simocephalus acutirostratus King (Cladocera: Daphnidae)‐laboratory studies of life span, instar duration, egg production, growth and stages in embryonic development
Authors: MURUGAN N. , SIVARAMAKRISHNAN K. G. 
Published: May 2006

SummaryThe life cycle of the cladoceran Simocephalus acutirostratus has been studied in the laboratory with reference to its total life span, duration of instars, egg production and growth. It has four pre‐adult and eighteen adult instars and produces about 248 eggs during a mean life span of 44 days within a temperature range of 28°C‐30°C. Egg production was found to be bimodal, with a sharp decline towards the end of the life cycle. The present results are compared and discussed with those of other tropical and temperate daphnids. It has been shown that while this species resembles most other daphnids (D. middendorffiana, D. pulex, D. carinata) in the growth pattern of pre‐adult instars, it resembles the temperate D. pulex in having a relatively long life span, relatively high egg production and slow rate of growth.While studies on embryonic development of S. acutirostratus resemble the growth stages of the temperate Daphnia magna, there are differences in the total period of development between the two species. In the latter aspect, however, the present species closely resembles other tropical daphnids.
The seasonal periodicity of planktonic diatoms in a shallow eutrophic lake
Authors: REYNOLDS C. S. 
Published: May 2006

SummaryThe seasonal periodicity of four species of planktonic diatoms in a small eutrophic lake in the Shropshire‐Cheshire Plain, England, is examined. Diatoms typically dominate the spring increase; a second period of growth follows in the summer months. The growth phases are considered in relation to environmental factors in the mere. Of these, light levels appear to be critical in determining the onset of growth and the size of the population maxima, whilst stratification and turbulence play a leading role in the vertical distribution of the algae, and hence, of the growth conditions to which they are exposed. The thermocline is believed to provide a reservoir of diatoms in summer, maintaining them in a position where they are able to gain maximum advantage from increased wind‐induced turbulence. Relative specific differences in growth requirements and in behaviour under varying physical conditions are important in determining which species dominate. Dominance may be modified by the effect of attacks by fungal parasites. It is also shown that, generally, nutrients are present in relative abundance, and only rarely does their availability become a limiting factor. Tt is concluded that diatom growth in this lake is typically subject to physical rather than chemical control.
The reproductive biology of the leech Helobdella stagnalis (L.) in Utah Lake, Utah
Authors: TILLMAN DAVID L. , BARNES JAMES R. 
Published: May 2006

SummaryThe reproductive biology of the glossiphoniid leech Helobdella stagnalis in Utah Lake, Utah was studied for an 18‐month period from June 1970 to December 1971. In this lake it was found that the overwintering adult leeches produce two broods of young in May and June. Evidence is presented to support the idea that the same individual can produce two broods. Two complete cycles of gametogenesis also take place. Continuous water temperatures were recorded at the study site to correlate with reproductive activity. Gametogenesis appears to be temperature dependent with the first generation of sperm taking 4 months to be produced in the fall and winter months while the second generation of sperm is produced in 6 weeks during the spring. Egg production follows a similar pattem.
A preliminary check‐list of the phytoplankton of the Oshun River, Nigeria
Authors: EGBORGE AUSTIN B. M. 
Published: May 2006

SummaryDuring hydrobiological investigations on the River Oshun, plankton samples were taken with a hand net of fine mesh for 14 months (May 1968‐June 1969). Thirty‐seven of the sixty species of algae identified have not been previously recorded in Nigeria. The qualitative character of the Oshun algae indicates the dominating nature of the floods in mixing bottom‐living and rock‐dwelling algae with the few euplanktonic species.
The occurrence of benthos deep in the substratum of a stream
Authors: DUDLEY WILLIAMS D. , HYNES H. B. N. 
Published: May 2006

Summary

The vertical distribution of the benthic fauna of the Speed River, Ontario, was studied over a 13‐month period from October 1970 to October 1971. Various physical and chemical parameters of this interstitial environment were also measured.
Several new techniques for sampling the interstitial environment of rivers wert devised. These methods and their relative efficiencies are considered.
The validity of the terms ‘hyporheal’ and ‘hyporheic’ are discussed and the term ‘hyporheos’ is offered to replace the former.
A brief resume of interstitial sampling methods is given with comments on their limitations for sampling deep heterogeneous substrates.
Chemical parameters are thought to be more important in the control and distribution ofthe fauna than physical parameters.
It is suggested that many larvae of stream‐dwelling chironomids have over‐wintering stages when they penetrate deep into the substrate to: (a) actively feed on the trapped organic detritus; (b) follow an optimum temperature for development.
It is suggested that the shape of an organism determines its success as a hypo‐rheic form and examples are given.
The numbers of animals oecurring in the sub‐benthic populations are shown to be very large indeed. For the Speed River, estimates of between 184,760 and 797,960 animals/m^ are made for different times of the year. Dry weight biomass is estimated o t vary between 30 9 g and 253‐2 g/m^ throughout the year.
Sub‐benthic or hyporheic populations are shown to exist in at least three other Canadian rivers. Some ofthe animals found are shown to be common to two or more of these rivers.
The inefficiencies of many conventional benthic samplers in sampling the total biomass of certain streams with hyporheic populations is discussed.
Effects of the herbicide paraquat on the ecology of a reservoir
Authors: BROOKER M. P. , EDWARDS R. W. 
Published: May 2006

SummaryToxicity experiments indicated that changes in the fauna following the use of paraquat for weed control were likely to be indirect effects caused by the death and destruction of angiosperms. Generally, invertebrates living amongst the emergent vegetation in the margins of the reservoir and on the sediments were unaffected though the density of the benthic ostracod Cypridopsis vidua increased rapidly after the death of angiosperms. Of the planktonic invertebrates, those which were generally closely associated with the macrophytes were eliminated or survived at lower densities. Many of the invertebrates intimately associated with the angiosperms (e.g. Lepidoptera, Tricho‐ptera. Gastropoda) were lost completely or colonized the replacement growth of Chara globularis at reduced densities: these effects were extended to the year after treatment. A few species colonizing Chara were able to establish densities comparable with those found on the angiosperms in the pre‐herbicide period but in some cases the time of peak density was delayed.Data from fish gut analyses indicated that there was a change in the diet of the eel following the death of the angiosperms and that this was largely a reflection of the loss, or reduction in density, of many invertebrates associated with the angiosperms.
Observations on some predators of stream‐dwelling triclads
Authors: WRIGHT JOHN F. 
Published: May 2006

SummaryA serological technique was used to demonstrate that one species of trichopteran and three species of plecopteran nymphs were feeding on stream‐dwelling triclads. Observations on streams in Caernarvonshire, North Wales, suggested that, in general, these predators were not typical members of the fauna at springheads, where triclads were frequently abundant. In contrast, further downstream the presence of predators was considered to be one of a number of factors which contributed to lower population densities of triclads. However, two small stony streams were encountered where the plecopteran predator Dinocras cephalotes occurred in close proximity to stream‐dwelling triclads from the springhead downwards. In one, both predators and prey were found at all stations but highest triclad numbers were recorded where predators were few. In the second stream the population density of the predator was higher, and here, triclads were very scarce on the undersides of stones and were almost entirely confined o t patches of moss. It appears that the predators may be both limiting the micro‐distribution of the triclad and also perhaps feeding selectively on larger individuals since mature triclads were rare, except at the springhead.
Studies on Plover Cove Reservoir, Hong Kong
Authors: TAI Y. C. , HODGKISS I. J. 
Published: May 2006

SummaryThe four periphytic communities established in Plover Cove Reservoir (the epiphyton, epihthon, epipelon and epipsammon) were investigated between November, 1970 and December, 1971. A rich flora of diatoms was found to dominate all four peri‐phytic communities, and, for this reason, assessment of diatom numbers was used to monitor each community during this survey.The standing crop of each community, measured by cell counts and by chlorophyll a determinations, showed distinct seasonal patterns. Except for the epipsammon, each community displayed a maximum growth in winter, a moderate spring and autumn growth period and a low summer growth. The episammic flora stood apart from the other attached floras in that it exhibited a prolonged maximum growth period in summer.Relatively small numbers of species were found to form the main bulk of all four communities (the so‐called ‘constant forms’) and these belonged predominantly to the pennate genera Achnanthes, Fragilaria, Nitzschia and Synedra.
Seasonal variation in the catching power of traps used for perch, Perca fluviatilis L.
Authors: CRAIG J. F. 
Published: May 2006

SummaryThe number of perch caught weekly in traps set in Slapton Ley, Devon has been considered. Five traps were laid in each of six regions during 1970 and 1971. The numbers caught in each region were averaged for eight lifts during 8 weeks and the logarithms of these numbers calculated. The figures obtained showed marked seasonal trends in the catch of the traps and these trends were consistent when both years were compared. If single traps were considered there was marked variability at one time which was attributed to differences in habitat. However, the combined data from each region did give a good comparison of the density of perch between regions.
Chemistry and vegetation of highly acidic streams
Authors: HARGREAVES J. W. , LLOYD E. J. H. , WHITTON B. A. 
Published: May 2006

SummaryAn account is given of the water chemistry and photosynthetic flora of waters in England with a pH value of 3.0 or less. Of the fifteen sites found, thirteen were associated with coal‐mining, one with a barytes mine and one was an industrial effluent. Flowing waters predominated, but in some cases pools in direct contact with the streams were also present. All waters carried high levels of heavy metals and silicate, and most carried moderately high levels of phosphate and combined inorganic nitrogen. The total flora consisted of twenty‐four algae, two mosses and two flowering plants. Of these, three algae and one flowering plant were found in pools only. Euglena mutabilis was both the most widespread species, and often also the most abundant. The number of species present in a reach showed a positive correlation with pH during late summer, and a negative correlation with total acidity in winter. Only four of the algal species found in England are certainly included in the U.S.A. literature. Some, but not all, the apparent differences between the two floras are very probably due simply to taxonomic problems.
The distribution and diel vertical migration of Pseudodiaptomus hessei (Mrázek) (Calanoida: Copepoda) in a subtropical lake in southern Africa
Authors: HART R. C. , ALLANSON B. R. 
Published: May 2006

SummaryThe vertical distribution and diel migratory behaviour of Pseudodiaptomus hessei in a freshwater lake is described. All stages showed a pronounced diel migration.During daylight naupliar and copepodite instars were almost exclusively benthic in shallow areas (<10m). Copepodite V and adult stages were predominantly benthic even at 40 m. The diurnal vertical distribution pattern implies age‐related differences in photosensitivity and a possible depth‐regulatory mechanism, based on the existence of differential photosensitivity, is offered to account for day‐depth control.Nocturnal vertical distribution, studied approximately fortnightly during 1970–71, showed no clear seasonal variation. Variations in pattern, most obvious in adult instars, correlated with prevalent lunar conditions. Nocturnal or midnight sinking was evident, particularly in post‐naupliar stages.Dusk rise and dawn descent were performed at very low light intensities and paralleled changes in light penetration. Dawn descent was less rapid than the dusk rise. An ephemeral dawn rise was sometimes observed but was not a consistent feature of all stages. An endogenous rhythm of locomotor activity was recorded under laboratory conditions. Activity was low during daylight, increased sharply at dusk and then decreased through the night to reach daytime levels at dawn. The stimulus provided by changes in light intensity and/or endogenous activity changes can account for the dusk and dawn movements of P. hessei but a definitive identification of the direct migratory stimulus is not possible. Attention is called to a closer examination of the role of endogenous activity rhythms in vertical migratory behaviour.The possible adaptive value of vertical migration to P. hessei is examined briefly.
Planktonic diatoms and silica in Loch Leven, Kinross, Scotland: a one month silica budget
Authors: BAILEY‐WATTS A. E. 
Published: May 2006

SummaryDiatom populations and silica concentrations were monitored at frequent intervals in the shallow, eutrophic Loch Leven over a 27‐day period (October 1972) and the influences of the inflows, outflow and the sediment were assessed. Changes in dissolved and particulate silica are accounted for by incorporating the results into a silica budget.During this period processes affecting silica within the loch were more important than those outside. The incorporation of diatom frustules into the sediments and the release of dissolved silica from the sediments appeared to be of particular importance. Evidence suggests that dissolution of the frustules of some planktonic diatom species was also important.
A quantitative study of the invertebrate fauna of the River Tees below Cow Green Reservoir
Authors: ARMITAGE PATRICK D. 
Published: May 2006

SummaryMonthly samples were taken in the River Tees below Cow Green dam from four sites differing in flow conditions, by means of trays containing stones from the river, which were immersed for a period of 1 month. Information on the distribution, abundance and biomass of the benthos of the River Tees is given with additional data on the life‐histories of some of the more common species, during the period May 1971 to May 1972.Of the seventy‐two taxa found, fourteen made up 95% of the total numbers. Hydra, Polycentropodidae, and the molluscs Limnaea peregra and Ancylus fluviatilis were the most abundant animals in the slower‐flowing water (10–26 cm s−1) and Simuliidae, Orthocladiinae, and Baetis rhodani dominate the riffle (50–75 cm s−1) fauna numerically. Some organisms, Nais spp., Caenis rivulorum and Baetis scambus favoured intermediate flows of 20–60 cm s−1. The slowest‐flowing water contained the largest number of taxa and the site with the fastest flow supported the least. A mean monthly weight per square metre of 14·56 g (95% limits from 7 to 31) was calculated using data from all four sites.The frequency distribution of nymphal size‐classes is given for B. scambus, C. rivulorum, Ephemerella ignita, and Brachycentrus subnubilus, and the association of certain nymphal size‐classes with a particular site is analysed.The composition and distribution of the fauna is discussed. It is suggested that the relative richness of the fauna in terms of biomass is attributable to the organic enrichment of the river following the building of the Cow Green dam. The regulation of the flow has allowed the dense growth of algae and mosses, and the development of large molluscan populations, and the reservoir itself provides a rich source of food, particularly zooplankton and phytoplankton, for the river benthos.
The chemical composition and energy contents of copepods and cladocerans in relation to their size
Authors: VIJVERBERG J. , TH. FRANK H. 
Published: May 2006

SummaryThe chemical composition and energy contents of four different species of cladocerans, one species of a calenoid copepod, and mixed samples of four species of cyclopoid copepods were quantitatively determined.The relative chemical composition, expressed as a percentage of the total organic matter (excluding chitin) of each of the different species analysed, were very similar. The mean relative composition for all species was 71·2% protein, 9·5% carbohydrates, 19·3% lipids, 16·5% total nitrogen and 2·1% total phosphate–phosphorus. A substantial amount of the total nitrogen was found to be non‐protein nitrogen (mean of 23·3% of total nitrogen). The calorific value was calculated from the estimated amounts of proteins, carbohydrates and lipids using conversion factors. The relationship between the calculated organic matter and the chemical oxygen demand (COD) was found to be constant and did not vary much for the different species. The ratio of total organic matter to COD has a mean value of 0·51. Calorific values ranged from 5847 to 6353 cal/g total organic matter.The amounts of chemical substances or energy contents per individual Copepoda or Cladocera were calculated. Regression lines together with their correlation coefficients have been computed to describe the relationship between the amount of chemical constituents and energy contents per individual, and the length of the individual. The results are extensively compared with those given in the literature and differences are discussed.
Actinomycetes in lake muds: dormant spores or metabolically active mycelium?
Authors: JOHNSTON D. W. , CROSS T. 
Published: May 2006

SummaryHomogenization and ultrasonication experiments on samples of lake muds indicated that Micromonospora strains were present as a mixture of mycelium and spores. In contrast, strains of streptomycetes and nocardioforms appeared to be in the form of arthrospores or fragmentation spores respectively.Micromonospora strains originally isolated from lakes were able to grow in both native and enriched muds incubated in the laboratory. Numbers of streptomycetes and nocardioforms did not increase in these muds and are presumed to be relatively inactive in this habitat.We postulate that Micromonospora strains have an active role in the lacustrine environment as well as in soil.
The distribution of cellulase in freshwater invertebrates of different feeding habits
Authors: MONK D. C. 
Published: May 2006

SummaryTwenty‐six species of freshwater invertebrates were assayed in vitro for cellulase activity. A soluble cellulose derivative and crystalline cellulose powder were weakly hydrolysed by gut extracts from several insects, and more strongly hydrolysed by extracts from molluscs and crustaceans. There was no correlation between the occurrence of cellulase and the abundance of cellulose in the diet.