bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of some ecological factors on the metabolism—temperature curve of the larvae of Limnephilus rhombicus (Trichoptera, Limnephilidae)
Authors: ROUX C. 
Published: May 2006

SUMMARY.
The oxygen uptake of Limnephilus rhombicus, a typical inhabitant of lentic waters, was measured in three different experimental situations: in still water with a plastic mesh as a substrate, in stirred water with a plastic mesh and in still water without any substrate. Water flow caused a small increase in oxygen uptake at all temperatures but principally above 15°C. The presence or absence of the plastic substrate had little influence on oxygen uptake; L. rhombicus can be active over the whole range of temperatures studied but its activity is always small. Its metabolism—temperature curve stands out in having a plateau between 5 and 10°C, with a steeper part between 10 and 20°C, the slope of which varies according to the conditions. Maximum oxygen uptake at high temperatures was relatively low (1235 ± 153 μl O2g dry wt‐1h‐1 at 25°C).The results are compared with those obtained previously for the larvae of Microptema testacea which inhabit flowing zones in brooks. L. rhombicus larvae appear both as cold‐water animals and as animals from highly variable biotopes. They are in fact very ubiquitous and occupy all lentic biotopes from cold and mountainous districts to temperate lowlands.
Periphyton production in Fort River, Massachusetts
Authors: SUMNER WILLIAM T. , FISHER STUART G. 
Published: May 2006

SUMMARY.
The primary production and general ecology of a periphyton community of a New England, lowland stream were studied over a seventeen‐month period. Temperature, light, periphyton chlorophyll‐α, and community structure were monitored regularly. Seasonally distinct chlorophyll peaks coincided with the light maximum in early May, just prior to the appearance of leaves of riparian trees, and again in autumn after terrestrial leaf fall. During midwinter, despite low light and temperature levels and high stream discharge, mean chlorophyll concentrations remained similar to summer values.A mathematical expression relating periphyton photosynthesis per unit chlorophyll‐α to temperature, light and periphyton density was established with submersible light‐dark chambers in situ. Survey data collected over the study period were employed in the empirical equation to estimate seasonal variations in periphyton primary production. Weekly mean daily estimates of periphyton gross production ranged from < 0.1 g O2 m−2, during midwinter, to 6.5 g O2 m−2 during early May. Estimated annual periphyton gross production and respiration were 0.58 and 1.27 kg O2 m−2, respectively. Factors influencing seasonal variations of Fort River periphyton standing crop are discussed.
Energetics of a population of the isopod Asellus aquaticus: Life history and production
Authors: ADCOCK J. A. 
Published: May 2006

SUMMARY.
A population of Asellus aquaticus in Wistow Lake, England, was sampled at monthly intervals from September 1973 to September 1974. The mean population density was 586 m−2 in autumn 1973 but it fell to 67 m−2 by autumn 1974. Evidence suggests that the lower density in autumn 1974 was due to premature mortality of gravid females. The cause of this is not known.Gravid females were present from February to June and July to September, giving rise to spring and autumn cohorts. The larger members of the spring cohort reproduced in the autumn, the remainder in the following spring. The autumn cohort reproduced mainly in the following spring but later than the spring cohort. The bimodal length‐frequency curves were analysed to separate the two cohorts and to estimate growth and production of each cohort separately. The overwintering spring cohort had a faster relative growth rate than the smaller individuals of the autumn cohort. Thus the spring cohort showed a P/B ratio of 2.62 for the period September–April compared with a ratio of 1.81 for the autumn cohort. The highest ratio of 6.42 was shown by the spring cohort in the summer (May–September).Annual population production (P) was 3004.9 mg dry wt m−2 from a mean biomass (B) of 757.2 mg dry wt m−2. The P/B ratio of 3.96 is double the value reported for A. aquaticus in Sweden.
Feeding on gastropods by lake‐dwelling Polycelis in the absence and presence of Dugesia polychroa (Turbellaria, Tricladida)
Authors: REYNOLDSON T. B. , PIEARCE BRONWEN 
Published: May 2006

SUMMARY.
Using a serological technique, the extent of feeding upon snails by Polycelis tenuis was compared in habitats lacking and containing Dugesia polychroa which is the major triclad predator of snails. It was found that P. tenuis ate significantly more snails when D. polychroa was absent. It was concluded that in the field interspecific competition for snails between these two triclad species was a more powerful process than any social feeding by P. tenuis on snails captured by D. polychroa.Feeding on snails as a group by P. tenuis and P. nigra in the habitat where the two triclads co‐existed was of a similar magnitude and this was also true of their feeding on the common snail species and genera. Approximately 10% of the triclads gave a positive reaction to snail antisera.Feeding on snails by P. nigra in the three habitats lacking D. polychroa was similar in extent and did not differ from that of P. tenuis. It was concluded that P. nigra would be similarly affected by the presence and absence of D. polychroa as shown for P. tenuis.No definitive seasonal pattern was detected in the incidence of feeding upon snails by either Polycelis species but this may have been obscured by seasonal changes in the detection period of snail antigens due to temperature effects. There was some evidence that such feeding increased during the period when small snails were present in the population.
The occurrence and ecological importance of dissolved ATP in fresh water
Authors: RIEMANN BO 
Published: May 2006

SUMMARY.
Dissolved ATP, defined as ATP which passes through 0.2 μm filters, was found in fresh water. During the spring diatom bloom in two eutrophic Danish lakes, concentrations of dissolved ATP varied between 0.1 and 3.8 μgl−1, constituting 14–76% of the total ATP (particulate plus dissolved ATP). The kinetics of the light emission obtained from mixing firefly enzyme with dissolved ATP demonstrated that the major proportion of the dissolved ATP was in fact ATP. Despite some variations, the seasonal changes in dissolved ATP paralleled the changes in the increasing phytoplankton population during the rise of the diatom blooms. The dissolved ATP increased after the diatom peak, indicating that release of ATP from the phytoplankton due to mortality may be a major source of dissolved ATP.Consumption of dissolved ATP was evaluated in uptake experiments using 3H‐ATP. Rates of uptake of 3H‐ATP by micro‐organisms (diameter 0.2–0.6 μm) proved to be close to the rates for 3H‐D‐glucose uptake. The variations in 3H‐ATP uptake during the diatom blooms showed non‐systematic changes and ranged between 1.0 and 15.8% h−1 (mean = 4.9% h−1) of the quantity added. Turnover rates for dissolved ATP varied between 12 and 730 ng l−1 h−1 (mean = 175 ng l−1). These rather high rates of turnover suggest that dissolved ATP is an important compound in the metabolism of freshwater bacteria.
Effect of temperature on the duration of egg, nauplius and copepodite development of some freshwater benthic Copepoda
Authors: SARVALA J. 
Published: May 2006

SUMMARY.
The development times of the egg, nauplius and copepodite stages of seven species of freshwater benthic copepods (Paracyclops fimbriatus, Canthocamptus staphylinus, Attheyella crassa, Moraria brevipes, M. mrazeki, Bryocamptus echinatus and Paracamptus schmeili) were determined at constant temperatures ranging from 1.5 to 24°C using detritus as food. Several regression models used earlier to describe the temperature dependence of development were tested on this material.Species differed both in the rapidity of development and in the magnitude of the effect of temperature. Development times usually decreased with increasing temperature, but in M. brevipes temperatures exceeding 16°C retarded postembryonic development. P. fimbriatus developed at a rate comparable to that reported earlier for littoral cyclopoids. All the harpacticoid species developed more slowly than planktonic, littoral or benthic copepods previously studied, but faster than subterranean species. The effect of temperature was most marked in species reproducing in warm water.The relationship between rate of development and temperature was not linear. None of the curvilinear temperature functions tested was statistically adequate in all cases. However, three of the models gave a reasonable fit to all egg development data, and one of these, the semilogarithmic quadratic equation, lnD= In a+T In b+T2 In c, also satisfactorily described postembryonic development. This model accommodates the retardation of development at higher temperatures, and can therefore be recommended for further testing.
An algal pigment ratio as an indicator of the nitrogen supply to phytoplankton in three Norfolk broads
Authors: WATSON R. A. , OSBORNE P. L. 
Published: May 2006

SUMMARY.
A pigment ratio representing the ratio of carotenoid pigments to chlorophyll‐a was calculated by dividing the optical density at 480 nm by that at 664 nm for a 90% acetone extract of phytoplankton. Its seasonal variation in three Norfolk broads was examined and, except for nitrogen‐fixing species, it was found to vary independently of the algal species composition.A good inverse correlation with the particulate nitrogen to carbon ratio was found. The seasonal variation in the pigment ratio was considerably affected by measurable lake concentrations of inorganic nitrogen supplied from ttie catchment. Other sources of nitrogen such as nitrogen fixation and release from the sediment were also indicated by changes in the ratio.By comparison with the distinctions of extreme, moderate and no nitrogen deficiency drawn by Healey (1975) for the nitrogen/carbon ratio, values for the pigment ratio of < 1.4, 1.4–2.4 and > 2.4 were found to indicate no, moderate and extreme nitrogen deficiency respectively in the phytoplankton. The relation ship is attributed to the measurement of secondary carotenoids in response to nitrogen deficiency.
A comparison of populations of the isopod Asellus aquaticus above and below power stations in organically polluted reaches of the River Trent
Authors: ASTON R. J. , MILNER A. G. P. 
Published: May 2006

SUMMARY.
Five populations of Asellus aquaticus, subjected to different combinations of temperature and organic pollution in the River Trent, were examined over a period of 18 months. The life‐cycle was probably completed in a year or less in all the populations sampled, a larger proportion of the animals completing the life‐cycle in less than a year at warmer locations. Young animals also hatched 1 or 2 months earlier at the warmer locations.At the locations subjected to most organic pollution, population densities and the size of animals of both sexes were the largest. The size of ovigerous females, however, appeared to be inversely related to temperature, the smallest occurring at the warmest location. Possible explanations for these differences are given in terms of the amount of food available and the effect of temperature on growth and sexual maturation.
A limnological survey of Lake Dakataua, a large caldera lake on West New Britain, Papua New Guinea, with comparisons to Lake Wisdom, a younger nearby caldera lake
Authors: BALL E. , GLUCKSMAN J. 
Published: May 2006

SUMMARY.
Lake Dakataua (5°S, 150°E) is a large freshwater lake which fills the caldera at the tip of the Willaumez Peninsula on West New Britain, Papua New Guinea. A peninsula produced by post‐collapse volcanic activity divides the lake into two basins connected by a narrow channel. The surface of the lake is c. 76 m above sea level, the surface area is 48 km2, and the maximum depth c. 120 m (Lowder & Carmichael, 1970). A bathymetric map of the lake has been constructed from fathometer transects.In October‐November, 1974, the lake was alkaline throughout with surface pH 7.6–8.2; acidity increased with depth to pH 7.1–7.5. Surface temperatures were 30.8–31.9°C. There were thermoclines at 22 m and at 40–45 m. Minimum temperature recorded was 26.8°C (at 80 m). Oxygen saturation curves were similar to the temperature curves with sharp gradients at 22 m and 40–45 m. There was no measurable O2 from 80 m downward. Living organisms were common in dredge hauls to 20 m but were not found in those from greater depths. Carbon dioxide concentration rose steadily from 1.4 mg I−1 at the surface to 19.6 mg I−1 at 80 m. Average Secchi disc transparency was 11.1 m.Shallow water areas support dense beds of mixed aquatic plants (Najas tenuifolia and Chara sp.). Invertebrates collected included two species of sponge, a rotifer, an ostracod, six species of molluscs, seven species of Cladocera, a copepod, eight species of Hemiptera, two species of Trichoptera, ten species of Odonata, two species of Coleoptera, and seven species of Chironomidae. Vertebrates included frogs (two species) and crocodiles. Water birds, including ducks, grebes, and waders, were abundant. The biota of L. Dakataua is more diverse than that of nearby Lake Wisdom probably due to the combination of greater age and greater proximity to sources of colonists. Most species found in L. Wisdom are also found in L. Dakataua.
Laboratory models of diel vertical migration in the dinoflagellate Ceratium hirundinella
Authors: HEANEY S. I. , FURNASS T. I. 
Published: May 2006

SUMMARY.
Diel vertical migrations of a dinoflagellate, Ceratium hirundinella, were induced in a laboratory tube (1.63 × 0.15 m) under a light‐dark cycle. The timing of vertical migrations differed between cultures in the exponential and stationary phases of growth; the latter showed a greater coincidence with the light regime.Migration of cells into the surface layers occurred at low values of surface irradiance (<550 μeinsteins m−2 s−1). At irradiances more closely approaching summer sunshine (> 1300 μE m−2 s−1) there was a marked avoidance of surface waters, and population maxima were found at depths associated with a relative irradiance level of 10% or c. 150 μE m−2 s−1). Thermal stratification restricted downward movement of cells into the cooler layers. The combination of high surface irradiance and thermal stratification resulted in large, stable, sub‐surface maxima of Ceratium, similar to those observed in natural waters under comparable environmental conditions.
Oxygen consumption in Caridina nilotica (Decapoda: Atyidae) in relation to temperature and size
Authors: HART R. C. 
Published: May 2006

SUMMARY.
The oxygen consumption of shrimps ranging from 1 to 30 mg dry mass was determined at 18, 24 and 30°C using a continuous flow recording respirometer based upon a Clark‐type oxygen electrode. Respiration (ascribed to routine metabolism) is described by the power curve: R = a Mb, (R=μg O2 h−1, M= mg dry mass), which gives values of a= 1.632, 2.564 and 4.181, and b= 0.800, 0.898, and 0.793, at 18, 24 and 30°C respectively. The single expression, R= 0.008 T1.829M0.830 provides a reasonable prediction of respiration as a combined function of shrimp size (M) and temperature (T, °C). Using an energy equivalent of 14.14 J mg O2−1 estimates of the energy requirements (E, J h−1 10−3) of routine metabolism are given by the expression: E= 0.115 T1.829M0.830.Variability in oxygen consumption values between individuals is discussed and the observations on C. nilotica are compared with other crustacean studies.
Embryonic duration and post‐embryonic growth rates of the tropical freshwater shrimp Caridina nilotica (Decapoda:Atyidae) under laboratory and experimental field conditions
Authors: HART R. C. 
Published: May 2006

SUMMARY.
Embryonic durations and post embryonic growth rates of Caridina nilotica were determined under laboratory conditions at constant temperatures near 18, 24 and 30°C. Embryonic durations and intermoult intervals were negative curvilinear functions of temperature. At a given temperature moulting frequency varied inversely with shrimp size and slight sexual differences were apparent. Moulting frequency of berried females was governed by the temperature‐specific embryonic durations.Growth rates were determined from changes in carapace length (CL) of individual shrimps (laboratory) or batches of shrimps (field enclosures) over 1 month and these data were used to calculate temperature‐specific life‐long growth curves for males and females. Growth in body mass was estimated indirectly from the carapace length‐mass relationship of C. nilotica. On average, males grew marginally faster than females during the first 2 months of life, but growth of males larger than CL= 4 mm was considerably depressed relative to that of females. Inflexions in growth rate, apparently related to the onset of sexual maturity, were apparent in both sexes.Under laboratory conditions, the growth rate of males increased with temperature, but temperature‐related differences were not as marked in females. Notwithstanding the more rapid moulting rate at 30°C the growth rate of females was slightly slower at 30 than at 24°C as a result of marginally but significantly smaller per moult growth increments observed at 30°C in animals up to CL= 5.5 mm. Possible reasons for this depressed growth are discussed.Growth rates of animals in field enclosures in Lake Sibaya over 1 month in winter (20 ± 3°C) were generally comparable to those estimated for the 18°C laboratory experiments. Growth rates in enclosures containing tripled standing stocks were almost identical to those containing the naturally occurring biomass of animals, suggesting a non‐limited environment at least during the time of the experiment.
A bacteriological investigation to elucidate the feeding biology of Nais variabilis (Oligochaeta: Naididae)
Authors: HARPER R. M. , FRY J. C. , LEARNER M. A. 
Published: May 2006

SUMMARY.
The estimated average number of bacteria in the gut of laboratory‐cultured Nais variabilis was 100.4 × 104. This compares with values of 6.7 × 104 and 32.8 × 104, respectively, for N. variabilis and N. barbata obtained from a river.Comparison of the viability of heterotrophic bacteria in the food and gut of N. variabilis indicated a decline in viability of up to 99.6% during the passage of bacteria through the gut. The estimated gut retention time was 39 ± 8 min at 18°C and therefore loss of viability is unlikely to be due to long retention in the gut. Loss of viability is, however, a prerequisite of bacterial digestion by the worm and provides circumstantial evidence that ingested bacteria are used as food.No conclusive evidence was obtained indicating (a) preferential ingestion of certain kinds of bacteria, (b) that the gut environment was selectively hostile to the particular kinds of bacteria studied or (c) that worms had a specialized gut micro‐flora.
The spatial distribution of nutrients in the South Basin of Windermere
Authors: GEORGE D. G. 
Published: May 2006

SUMMARY.
The vertical and horizontal distribution of electrical conductivity, soluble reactive phosphorus (SRP), total phosphorus, ammonia‐nitrogen and nitrate‐nitrogen in the South Basin of Windermere is described and related, where possible, to spatial variations in phytoplankton and zooplankton.For most variables, the maximum range of horizontal variation on a single day was greater than the maximum range of seasonal variation measured at a single station over a full year. Horizontal variations in SRP and ammonia were particularly high, with coefficients of variation often exceeding 100%. The errors associated with sampling at a single station were most pronounced when local accumulations of zooplankton or phytoplankton occurred in the lake.Horizontal variations in conductivity were primarily influenced by the discharge of treated sewage effluent into the central region and the mass transport of water from the more oligotrophic North Basin. Occasionally, more widespread variations in conductivity appeared to be related to spatial variations in photosynthetic activity. The major factor influencing the horizontal distribution of SRP was the discharge of treated effluent into the central region. Despite the intensive recycling of phosphorus, SRP concentrations were nearly always 10–30% higher near the sewage works than elsewhere in the basin. On a few occasions, significant horizontal differences in SRP concentration were also detected within downwind accumulations of crustacean zooplankton. Horizontal variations in total phosphorus were produced by spatial differences in SRP concentration or by local accumulations of phytoplankton or zooplankton. Horizontal differences in ammonia concentration appeared to be produced, both by the effluent discharge and by the turbulent transfer of nutrients from sediments in shallow water.Observations of effluent movement and dispersion demonstrate that wind‐induced water movements tend to recirculate nutrient‐rich water in the central region and limit mixing along the axis of the basin. The statistical implications of nutrient heterogeneity are discussed in relation to sampling strategy and the possible effects of persistent nutrient concentration gradients on phytoplankton patch formation are assessed.
Growth and recession of aquatic macrophytes on a shaded section of the River Lambourn, England, from 1971 to 1980
Authors: HAM STEPHANIE F. , COOLING D. A. , HTLEY P. D. , McLEISH PENELOPE R. , SCORGIE H.R.A. , BERRIE A. D. 
Published: May 2006

SUMMARY. The growth and recession of macrophytes on a shaded section of the R. Lambourn were documented by a mapping procedure. With the exception of Ranunculus spp., the changes in total cover did not indicate directly the pattern of growth and recession of the macrophyles. Analysis of gross changes, expressed as gains and losses on cover, indicated that colonization of gravel and silt by the dominant macrophyte, Berula erecta, did not vary seasonally. Colonization was at a constant rate of about 8% of the site each month throughout the year and this accounted for 50% of the total number of gains by Berula. Gains of Berula from Ranunculus showed an annual cycle with a maximum during the summer when Ranunculus was in recession. Gains of Berula from Callitriche spp. also varied annually but the maximum was during the autumn. Total losses of Berula were at a constant rate throughout the year but were to gravel and silt during the winter, to Ranunculus in spring and early summer and to Callitriche in late summer and autumn. Analysis of loss of Berula with time indicated that the position of the Berula carpet was constantly changing. The growth and recession of Berula could not be linked in a meaningful way to environmental variables. Callitriche and Ranunculus both showed an annual pattern of growth and recession. There was temporal separation of the two macrophytes with Ranunculus growing mainly in spring and early summer and Callitriche showing maximum growth in late summer and autumn, and some evidence of spatial separation. The observed differences between years in the growth of Callitriche could not be attributed to any of the environmental variables measured.Discharge was thought to be an important variable controlling the growth of Ranunculus since increase of Ranunculus in the spring was positively correlated with the mean discharge at that time. In years when discharge was low, the growth of Rununculus appeared to be restricted by shading from epiphytic algae which accumulated on the plant surfaces under these conditions.