bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of the growth rates of epiphytic bacteria and Lemna minor in a river
Authors: HOSSELLand JUDITH C. , BAKER J. H. 
Published: May 2006

SUMMARY.
Growth of Lemna minor fronds in the River Frome during summer was found to be logarithmic with time and the growth rate (log10) was 0.066 day−1. This is equivalent to a doubling time of 4.5 days. The life expectancy of the fronds was 34 days.The net change in the density of bacteria epiphytic on the lower surface of Lemna fronds in the R. Frome was monitored using a direct microscopic technique. The observed increase in bacterial numbers has been partitioned into the components of attachment and growth, assuming that attachment occurred at a constant rate and that the bacterial population grew logarithmically. The line which fitted the data best gave an attachment rate of 5.7 × 105 bacteria cm−2 day−1 and a growth rate (log10) for the bacteria of 0.044 day−1 which is equivalent to a doubling time of 164 h.Estimates of the rate of detachment of bacteria from Lemna plants were obtained from a laboratory experiment which assumed negligible growth of bacteria in 1 h. The number of bacteria which detached per hour and the sizes of the bacterial populations on the plants before and after detachment were estimated using a plating technique. Different detachment rates were monitored. The detachment rate (analogous to growth rate) which is judged to be most similar to an in situ value was 0.0031 h−1 (0.074 day−1). This rate added to the specific growth rate given above resulted in a corrected growth rate of 0.118 day−1 equivalent to a doubling time of 61 h.
Feeding and growth of the isopod Asellus aquaticus on actinomycetes, considered as model filamentous bacteria
Authors: WILLOUGHBY L. G. , MARCUS J. H. 
Published: May 2006

SUMMARY.
Asellus aquaticus was fed for 49 days at 15°C on aquatic actinomycetes in the laboratory. Specific growth rates (wet weight) of animals initially 2.5mm in length ranged from 0.85 to 2.33% day−1 on Micromonospora and Streptomyces S2 respectively. Asellus newly released from the brood‐pouch (1.0 mm length) had a similar growth rate (2.74% day−1) on Streptomyces S2. The growth rates of animals fed on actinomycetes were lower than those of animals feeding on macroscopic foods such as Elodea and decaying oak leaves, regardless of the initial size of the animal. However, it was concluded that actinomycetes, and by inference bacteria also, could maintain a population, albeit a slow‐growing one, in a situation where macroscopic foods are largely absent.The possible significance of hyphal diameter of micro‐organisms in relation to assimilation from them is discussed. In this connection actinomycetes are considered as model filamentous bacteria.
Life cycles and growth rates of Baetis spp. (Ephemeroptera: Baetidae) in the laboratory and in two stony streams in Austria
Authors: HUMPESCH U. H. 
Published: May 2006

SUMMARY.
Larvae of Baetis alpinus, B. lutheri and B. rhodani were reared in a stream channel (water temperature range 4.2–11.4°C) in the laboratory. The larval growth was exponential and the mean specific growth rate varied from 1.93 to 2.24% day−1 for B. alpinus, 1.49 to 3.41% day−1 for B. lutheri and 0.79 to 3.11% day−1 for B. rhodani. These variations in growth rate were related to variations in mean temperature and this was the major factor affecting growth in the laboratory.Non‐quantitative samples of the benthos in the Seebach and Unterseebach, two stony streams near Lunz, Austria, were taken at approximately monthly intervals from November 1965 to May 1968. In each year, there were two winter and three summer cohorts for B. alpinus from Seebach and two or three winter and one to three summer cohorts for B. lutheri and B. rhodani from Unterseebach. Over the study period of 30 months, eleven cohorts were recorded for B. alpinus and B. lutheri, and ten cohorts for B. rhodani. The life cycle of a cohort varied from 3 to 8 months in B. alpinus, from 2.5 to 9 months in B. lutheri and from 2.5 to 8 months in B. rhodani. Mean specific growth rate in length varied from 0.82 to 2.97% day−1 for B. alpinus, 0.96 to 3.33% day−1 for B. lutheri and 0.65 to 3.01% day−1 for B. rhodani. The percentage of the variability in growth rate accounted for by variations in mean temperature was 63% for B. alpinus, 91% for B. lutheri and 82% for B. rhodani. Therefore mean temperature was clearly the major factor affecting the growth rates in the field.An agreement was found between the growth rates of B. alpinus in the field and the laboratory. The growth rates of B. lutheri and B. rhodani were slower in the field than in the laboratory at higher temperatures. The possible reasons for this latter discrepancy are discussed, and the growth rates of the three Baetis spp. are compared with those of other species of Ephemeroptera.
The effects of coal industry pollutants on the macroinvertebrate fauna of a small river in the South Wales coalfield
Authors: SCULLION J. , EDWARDS R.W. 
Published: May 2006

SUMMARY.
The effects of pollutants from the coal industry on the macroinvertebrate fauna of a small river in the South Wales coalfield were investigated during 1972 and 1973.Three major types of pollution, each spatially separate, affected the river and its tributaries. The upper reaches received acidic drainage from coal stockpiles. The lower reaches received a discharge from a drift mine, bearing high loads of suspended coal particles which caused siltation of the river bed downstream to its confluence with the R. Taff (3.5 km). The largest tributary was subjected, under neutral pH, to siltation by ferric hydroxide, derived from seepage from an abandoned mine.In the upper reaches, a few acid‐tolerant invertebrate species survived in low numbers. Downstream recovery was not complete before the discharge of coal particles. In the reaches silted by ferric hydroxide or coal there was a pronounced reduction (80–90%) in faunal abundance. Clear differences in sensitivity of invertebrate groups to these types of siltation were apparent.The data are used to assess the various methods of biological surveillance involving invertebrates.
Phytoplankton ecology in an Antarctic lake
Authors: LIGHT J. J. , ELLIS‐EVANS J. C. , PRIDDLE J. 
Published: May 2006

SUMMARY.
The ecology of the phytoplankton of Heywood Lake, Signy Island, South Orkney Islands, Antarctica was investigated during 1969–72. The lake, which is ice‐covered for 8–10 months per year, is moderately eutrophic due to enrichment by seal excreta.The annual cycle of the phytoplankton is described. During the winter (approximately May‐September), very few algal cells could be detected in the water column and 14C fixation was below measurable limits. In spring (October‐November), a rapidly‐growing population of algae caused a large increase in the chlorophyll‐a concentration (maximum value 170 mg m−2) but carbon fixation remained low, with values <500 mg C m−2 day−1. The algae contributing to this peak were mainly small chlorophytes and chrysophytes. The summer open‐water period (December‐March) was characterized by a different phytoplankton population dominated by cryptophytes. Chlorophyll levels were lower (c. 40 mg m−2) but 14C fixation rates >3 g C m−2 day−1 were measured on bright days. Values for Assimilation Number were very high (maximum value 10.5 mg C h−1 mg−1 (chlorophyll‐a) in January (1971) though temperatures never exceeded 8°C. In autumn, the phytoplankton regressed to winter levels. Both spring and summer algal populations probably overwinter as resting stages.
Field estimates of feeding rate for Gammarus pseudolimnaeus (Crustacea: Amphipoda) in the Credit River, Ontario
Authors: MARCHANT R. , HYNES H. B. N. 
Published: May 2006

SUMMARY.
The feeding rate of G. pseudolimnaeus was measured monthly for 7 months in the field by monitoring the decline in weight of gut contents when the amphipod was starved. This decline was modelled by an exponential regression of weight on time. As the amphipods appeared to be continuous feeders, feeding rate was calculated by multiplying the dry weight of a full gut by the specific rate of emptying, i.e., the slope of the exponential regression. Specific rate of emptying was independent of animal size, but increased with temperature. Therefore, food has a longer period in which to be digested at low temperatures, which suggests that assimilation efficiency may increase.However, the assimilation efficiency of amphipods feeding on decaying maple leaves in the laboratory was only 10% and did not vary with temperature. Ingestion and egestion rates were measured in the laboratory by weighing amounts eaten and defecated. The turnover time of the contents of a full gut in the laboratory often agreed very well with turnover time measured in the field, i.e., the reciprocal of the specific rate of emptying, thus confirming the use of an exponential regression.
The distribution and production of Gammarus pseudolimnaeus (Crustacea: Amphipoda) along a reach of the Credit River, Ontario
Authors: MARCHANT R. , HYNES H. B. N. 
Published: May 2006

SUMMARY.
The population density of the univoltine amphipod Gammarus pseudolimnaeus was estimated monthly from April 1977 to June 1978 along a 600‐m reach using a form of removal sampling at 0.5, 1.5 and 2.5 m from the bank. The probability of catching an amphipod with three sweeps over an area of 0.15 m2 was 0.95. Drift and upstream migration were measured for 24 h, also monthly. Population density varied from 1600 m−2 (newly‐hatched young in July) to 26 m−2 (adults) within 3 m of the bank with 95% confidence limits of 40–60% of the mean; density was highest < 1 m from the bank and beyond 3 m it declined to insignificant levels. No significant difference could be shown between the total catches in the drift and upstream nets over a year and there appeared to be no net migration of amphipods. Mean drift was 2 amphipods day−1.Growth was estimated from the length composition of monthly samples. Annual production (P) was 29.4 kg ha−1 for one generation of the amphipod with a P/B ratio of 4.65. Egg production accounted for only 2% of this estimate. Recruitment was calculated from regressions relating female length to clutch size and egg development time to temperature in the laboratory; mean temperature was measured in the field.Mortality was greatest in July at the beginning of the generation. It was high again in September and during winter; at these later times it was suggested that starvation occurred in addition to predation. Annual consumption (C) of organic matter for the generation calculated from published data on feeding rate was 1547 kg ha−1 which results in a P/C ratio of 1.9%.
Metabolism of a desert stream
Authors: BUSCH DAVID E. , FISHER STUART G. 
Published: May 2006

SUMMARY.
Rates of photosynthesis and community respiration were determined for benthic assemblages in Sycamore Creek, a Sonoran Desert stream in Arizona. Benthos in this stream can be separated into (1) mats of Cladophora glomerata and associated epiphytes and (2) assemblages of epipelic diatoms and blue‐green algae. Community respiration and net photosynthesis were measured for these assemblages using submerged light‐dark chambers in situ. Multiple regression analysis was used to predict (1) gross photosynthesis as a function of photosynthetically active radiation, temperature and chlorophyll‐α concentration; and (2) community respiration as a function of temperature and biomass.Calculations suggest that Sycamore Creek is autotrophic during the summer (P/R= 1.7) and that the rates of gross photosynthesis (P=8.5 g O2 m−2 day−1) and community respiration (R= 5.1 g O2 m−2 day−1) are high for a small stream. Considerable difference exists between the Cladophora mat assemblages, in which mean P is 12.5gO2m−2 day−1and the P/R ratio is 2.3, and the epipelic assemblages in which mean P is 4.4 g O2m−2 day−1 and P/R is 0.96. The high rate of gross photosynthesis, low litter inputs, high biomass of algae and the intermittent but severe floods that characterize Sycamore Creek indicate that this stream and other similar desert streams are net exporters of organic matter and are, thereby, truly autotrophic stream ecosystems.
Effect of temperature on the duration of egg development, and moulting and growth in juveniles of Crangonyx pseudogracilis (Crustacea: Amphipoda) in the laboratory
Authors: SUTCLIFFE D. W. , CARRICK T. R. 
Published: May 2006

SUMMARY.The interval between moults is an extension of egg development time, increasing from birth to sexual maturity which is probably reached at instar 6 or 7. The duration of each instar increased with the animal's age. Incubation time for eggs and the intermoult interval have the same curvilinear inverse relationship with water temperature in the range 3.5–25°C. Results are expressed as degree‐days above predicted threshold temperatures of 3.8°C for eggs and 3.2°C for instar 1 after birth, but inverse power‐law relationships were a better fit to the results, with exponents of ‐ 1.355 for eggs, ‐ 1.263 for instar 1 and ‐ 1.37 to ‐ 1.92 for instars 2–4. Temperature — dependence apparently altered in instars 5 and 6 at 15–25°C. From a multiple regression of geometric mean moult interval (Mi, days) against mean age (A) and temperature (T, °C),Mi= 56.4T−0.7e0.016A, with mean ages of 106 days at 15°C and 85 days at 25°C after six moults.The mean number of primary flagellar segments on the antennules increased from 4.0 in instar 1 to 6.0 in instar 2 and 8.0 in instar 3. Thereafter, segments were added less regularly to give a mean of 13.2 in instar 7. In a natural population, when the sexes became distinctive they had 11–13 flagellar segments.From birth atc. 0.05 mg wet wt, individual growth rates were highly variable; mean growth rates (Gs, % wet wt day−1) were similar in animals fed on dried, leached elm leaves and living, green leaves ofCallitriche; there was a power‐law relationship with temperature in the range 3.5–25°C, (Gs= 0.27T0.59). Faster growth rates were obtained on living leaves ofElodea. Sexual maturity is reached atc. 0.4–0.5 mg wet wt. A brief comparison is made withGammarus pulex;C. pseudogracilismay be better adapted to warm‐water habitats.
Grafham Water
Authors: STENT R. F. 
Published: May 2006

SUMMARY.
The phytoplankton and zooplankton of Grafham Water reservoir, Cambridgeshire, are described and discussed for the 5 years 1974–78 together with the main physical variables and macro‐nutrients believed to affect them. This follows on from the Water Pollution Research Laboratory study of 1969–74. The rationale for the work was to provide short‐term warning of treatment and management problems caused by algae and to gain insight into the factors controlling them.During the period reviewed the 1976 drought occurred with a massive draw‐down. Afterwards replenishment of the lake from the River Great Ouse resulted in its enrichment with high concentrations of nitrate, orthophosphate and silica. The algal cycles changed to some extent over this period with a few species becoming even more dominant and others diminishing in importance. The effect of the drought and post‐drought pumping is discussed; a return to former nutrient levels seems likely. The effects of weather, particularly radiation and wind, on algae may be of equal importance to nutrient levels in Grafham and will be further investigated.
A study of the benthic communities of twenty lakes in the South Island, New Zealand
Authors: TIMMS B. V. 
Published: May 2006

SUMMARY. The benthos of a heterogeneous series of lakes was sampled in late winter‐spring (before insect emergence) to determine species composition, community structure and standing crops. Nearly 50 species were found, with an average of only 12.4 per lake. Fifteen species occurred widely, with the same few species(Limnodrilus hoffmeisteri, Potamopyrgus antipodarum and sometimes Chironomus and Macropelopia spp.) often dominant. All taxonomic groups were of limited diversity; for instance, the maximum number of chironomids per lake was 8, with an average of 4.7 species. There were no chaoborids or mayflies, and very few isopods, amphipods, ceralopogonids and water mites. Niches of common species were broad.Species composition and dominance were not related to lake trophic status; hence there were no indicator organisms. Standing crops varied only broadly with lake trophic status, probably because of the differential influence of extraneous factors such as relative depth and input of allochthonous organic matter and silt. Depth: biomass profiles were also variable and only partly correlated with trophic status. Instead, many lakes were grouped on the basis of geographical area and the influence of extraneous factors; species were grouped according to the relative extent of their distribution.
The growth of the freshwater crayfish A ustropotamobius pallipes in Northumbria
Authors: BREWIS J. M. , BOWLER K. 
Published: May 2006

SUMMARY. Growth increments, moult frequency and growth rates of individuals in a population of the freshwater crayfish Austropotamobius pallipes were followed for a period of 3 years during a mark‐recapture study. There was an inverse relationship between body size and the growth increment relative to body size. The absolute increment increased from the juvenile to the young adult stage and thereafter declined with increasing body size.Differences between the adult male, reproductive female, non‐reproductive female and juvenile subpopulations in the size of growth increments are reported and growth increments during the two major moult periods of each year are compared. The effect of the endoparasite Thelohania contejeani and of chela regeneration was to reduce slightly the growth increments.Instantaneous growth rates declined throughout life in both sexes, but adult males maintained higher growth rates than adult females, particularly in the largest size class studied. The effect of reproduction on growth appeared to be most severe in the smallest breeding females. Males maintained the tendency to moult twice annually to a larger size than females. A simplified construction of the relationship between size and age in the population is presented for each sex. The oldest animals were estimated to be at least 11 years old.
A quantitative study of the life cycle of the case‐building caddis Odontocerum albicorne (Trichoptera: Odontoceridae) in a Lake District stream
Authors: ELLIOTT J. M. 
Published: May 2006

SUMMARY. Odontocerum albicorne (Scopoli) took 1 year to complete its life cycle in a 3‐year study of this species in a small, stony stream in the English Lake District. Adults were present from May to August (1967, 1968) or from June to September (1969); most eggs were laid in July and August. There were five larval instarsand most larvae were in instars III, IV and V by October. Larvae usually overwintered in instar V or III and some third instars were in a resting state in sealed cases. Most fifth instars became male pupae in spring; most third instars grew rapidly to instar V in spring and then became female pupae. The duration of the pupal stage was short, and was shown in laboratory experiments to require 87.5 degree‐days (95% C L = 79–98 degree‐days) above a threshold temperature of 6.7±0.01°C. Pupation in the stream did not commence until temperatures exceeded 6.8°C.As the sample variance‐mean relationship followed a power‐law, the spatial distribution of larvae and pupae was density dependent. Relative clumping remained fairly constant between year‐classes but increased markedly between the larval and pupal stages. Although population density varied between year‐classes, it remained remarkably constant in each year‐class for about 9 months between the end of egg hatching and the start of adult emergence.The growth pattern was similar in each year‐class but growth rates varied between year‐classes. The mean instantaneous growth rate was highest (range 3.9–8.0% dry wt day‐1)in the first 3 months of the life cycle (August‐October), close to zero in winter (November‐February) and slightly higher than 1% day‐1 (range 1.1–1.7%) for the rest of the life cycle (March‐August). Production varied considerably between years and year‐classes, and was closely related to growth rates for March‐August. Annual production estimates were 243, 160 and 257 mg dry wt m‐2 in 1967, 1968 and 1969. respectively. The ratio of production to mean standing crop (P/B) also varied between year‐classes and the mean annual value was 3.9 (range 3.2–4.5).Life tables were similar for the 1966 (latter part only), 1967, 1968 and 1969 year‐classes. Losses were very high (c. 99%) in the egg stage and early instars. About 30% (range 27–31%) of the population in instars III‐V did not reach the pupal stage, and c. 25% (range 20–29%) of the pupal population died. About 37% (range 35–39%) of the emerging adults were females.
The life history and production of the leech Helobdella stagnalis (Hirudinea:Glossiphonidae) in the River Ely, South Wales
Authors: MURPHY P. M. , LEARNER M.A. 
Published: May 2006

SUMMARY. A population of the glossiphonid leech Helobdella stagnalis was studied over a period of 16 months in the organically polluted River Ely, South Wales. There were two generations each year. The overwintering population released young (the spring‐brood) in June. The spring‐brood in turn produced their own offspring (summer‐brood) in August.Seasonal patterns of mortality were related to flow, temperature and life‐cycle stage. Individual growth rates were dependent upon both temperature and life‐cycle stage.Annual population production (P) was 7.56 g wet wt m‐2, mean annual population biomass (B) was 1.43 g wet wt m‐2 and the annual P/B ratio was 5.29.
A field experiment on the value of allochthonous straw as food and substratum for lake macro‐invertebrates
Authors: STREET M. , TITMUS G. 
Published: May 2006

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 C hironomus was distributed independently of Material. The other abundant taxa (Gammmrus. Asellus, Cryptochirnomus and Helobdella 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, only Pisidium was 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 distribution.