bluuebunny/crossref_metadata_2025_split huggingface dataset:
Annual cycles of macro‐invertebrates of a river in southern Ghana
Authors: HYNES J.D. 
Published: May 2006

SummaryThe results of a quantitative study of the benthic invertebrates of a riffle area in the upper reaches of the Pawmpawm River in the forest of southern Ghana are presented. The investigation was carried out over a period of 17 months with a Surber Sampler. The seasonal fauna changes are discussed in relation to changes both in water flow and in the vegetational substrate, and a model for the succession of recolonization of the river after the resumption of flow is outlined. The earliest colonizers of the river were primary consumers, Chironomidae, Centroptilum and Simulium., which were followed after a few weeks (once a mat of vegetation had become established) by the carnivorous Cheumatopsyche (Trichoptera) and Centroptiloides (Ephemeroptera). After 2 to 3 months, the attached vegetation matured and was able to support a greater diversity of fauna. The strategy of survival in intermittent tropical rivers is discussed and it is concluded that recolonization from eggs laid by flying adults is the most important method.
The determination of nucleic acids in freshwater plankton and its ecological implications *
Authors: BAUDOUIN MARIE‐FRANCE , SCOPPA PIETRO 
Published: May 2006

SummaryNucleic acid concentrations show large variations between different planktonic species. RNA concentration is much higher in phytoplankton than in zooplankton. DNA varies to a considerable extent, being five to six times higher in copepods than in cladocerans. In Daphnia hyalina, nucleic acid contents are proportional to dry weight during the whole life cycle except in newborn Daphnia where DNA concentration is abnormally high. Seasonal variations affect, to a large extent, nucleic acid concentrations. These results rule out the possibility of using nucleic acids as indicators of biomass in mixed planktonic populations.
Salinity tolerance and osmoregulatory ability of Galaxias maculatus (Jenyns) (Pisces, Salmoniformes, Galaxiidae)
Authors: CHESSMAN B. C. , WILLIAMS W. D. 
Published: May 2006

SummaryThe salinity tolerance and osmoregulatory ability of Galaxias maculatus were investigated. In the field this species has been recorded from salinities of less than 1‰ to 49‰. In the laboratory, upper L.D.50 salinity values of 62‰ after gradual acclimation and 45‰ after direct transfer were established. Within the salinity range of its field occurrence the species is a powerful osmoregulator, being able both to hypo‐ and hyper‐osmoregulate.
Dominant diatoms in Tjeukemeer
Authors: MOED J. R. , HOOGVELD H. L. 
Published: May 2006

Summary Diatoma elongatum has been observed in Tjeukemeer (The Netherlands) from time to time. Its intermittent presence is probably a consequence of the local hydrology. In early 1972, besides the usual increase of Melosira spp. and of unicellular centric diatoms, a development of D. elongatum took place. Its maximum was found 5‐6 weeks later than those of the centric diatoms. Possible factors causing the decrease in number of cells are discussed.
Quantitative aspects of the distribution of invertebrates in the benthos of a small stream system in western Ireland
Authors: FAHY EDWARD 
Published: May 2006

SummaryThe invertebrate community of a small stream system in western Ireland is described from the results of two sampling programmes. The investigation was conducted at four sites which occurred within the same range of altitude (between 60 and 130 m O.D.) and the greatest differences between them were rock size, current intensity and the amount and type of detritus in the substratum. Approximately 60,000 invertebrates were identified and almost 100 taxa were listed. Attempts which were made to relate the occurrence of certain taxa to three factors (rock size, current intensity and detrital content) showed that detrital content was the most significant. Using empirical clustering techniques efforts were made to demonstrate zonation of the invertebrates taken during one of the two sampling programmes and the groups which were so obtained were further amalgamated subjectively. The resemblance of the resulting pattern to lotic zonation is briefly discussed.
The Plecoptera community of a small stream in Oregon, U.S.A. *
Authors: KERST CARY D. , ANDERSON N. H. 
Published: May 2006

SummaryThe Plecoptera community of a small woodland stream in Oregon was studied by examining density and species composition. Four sites were studied using benthos sampling for larvae and emergence trap collections for adults. Sixteen genera and forty‐three species were identified with most species occurring in relatively low numbers. A comparison with the species list from an earlier study suggested that the species composition has not changed markedly in 40 years but there were several changes in relative abundance.Species diversity of stoneflies decreased with distance from the headwaters. These changes were correlated with decrease in habitat complexity, decrease in stability of the substrate, and increase in water depth. Examples of longitudinal succession are given as a method enabling the large number of species to partition the habitat. Concurrent benthos and emergence sampling demonstrated differences in emergence success that were correlated with habitat suitability.
An experimental study of the role of gradient and substratum in the distribution of two stream‐dwelling triclads, Crenobia alpina (Dana) and Polycelis felina (Dalyell) in North Wales
Authors: LOCK MAURICE A. 
Published: May 2006

SummaryA laboratory stream is described which has simulated steep‐ and shallow‐gradient bottoms whose gradients can be varied. It was found that Polycelis felina, the principal triclad of shallow‐gradient streams had a much reduced ability to colonize the simulated steep‐gradient bottoms when compared to Crenobia alpina, which is the principal triclad of the steep‐gradient bottoms in the field. P. felina is unable to move in the steep‐gradient bottoms to any great extent, while C. alpina showed considerable ability to do this. When a reduction in flow was made this did not increase the proportion of P. felina to be found in the steep‐gradient regions. The triclads were also tested for possible acclimatory responses and it was found that their responses were more fundamentally based. On the basis of the above evidence it is suggested that the absence of P. felina from the steep‐gradient regions of streams in North Wales is due to a behavioural inability to tolerate the current regimes present in the steep‐gradient bottoms.
The influence of microbial food sources and aeration on the growth of Ceriodaphnia quadrangula (O.F.Müller) (Crustacea: Cladocera) under experimental conditions
Authors: SMYLY W. J. P. , COLLINS VERA G. 
Published: May 2006

SummaryCasual observations had shown that, in laboratory cultures, populations of Ceriodaphnia quadrangula (O. F. Muller) rarely persisted for more than a month at most. It is shown here that populations of C. quadrangula can be maintained in static water on a diet of mixed algae (mainly Scenedesmus quadricauda (Turp.) Brev., but if the water is disturbed by a slow current of ascending air bubbles, the numbers of C. quadrangula decline. Death is not, however, immediate, and at high densities populations may persist in disturbed water for several weeks before numbers start to decline.Numbers of C. quadrangula did not decline in disturbed water when the food was changed from the alga Scenedesmus to the animal Artemia salina (L.). Individuals of C. quadrangula in the presence of decomposing naupliar larvae of A. salina grew as well in disturbed as in static water and in static water their numbers increased at a greater rate on this animal diet than on an algal diet of Scenedesmus. When the bacterial populations associated with Scenedesmus were greatly reduced, there was no increase in the numbers of C. quandrangula. Microbes associated with Scenedesmus, and not the alga per se, seem to be used as food by C. quandrangula.
Number of meals in a day, maximum weight of food consumed in a day and maximum rate of feeding for brown trout, Salmo trutta L.
Authors: ELLIOTT J. M. 
Published: May 2006

SummaryBrown trout (live weight 9–302 g) were fed to satiation in each of four meals at seven different water temperatures (range 3.8–18.1°C). The period (Ih) from the start of one meal to the start of the following meal was not significantly affected by the weight (Wg) of the trout, but was negatively correlated with water temperature (T°C). A regression equation described the exponential relationship between I and T, and also estimated the number of meals {N) in a day. Values ranged from one meal at about 4°C t o three meals at about 18°C, The greatest increase in appetite occurred at the end of the period I.The maximum weight offood (Drng) eaten in a day was positively correlated with both W and T, a relationship which was well described by a multiple regression equation. The maximum rate of feeding (Fmg h−1) was not significantly affected by W, but increased from 3.8 to 6.8°C, was fairly constant from 6.8 to 19.3°C, and decreased markedly above 19.3°C. Estimates of D and F(with 95% confidence limits) were applicable to a wide variety offood organisms with the exception of mealworms. From comparisons with the results of other workers, it was concluded that the upper limit ofthe daily energy intake determines the optimum temperature for growth.
Primary production studies on a new reservior; Bighorn Lake‐Yellowtail Dam, Montana, U.S.A. *
Authors: SOLTERO RAYMOND A. , WRIGHT JOHN C. 
Published: May 2006

SummaryA definite algal succession pattern was established for all 3 years of study. Volume‐based phytoplankton density and chlorophyll concentration decreased down‐reservoir. However, the depth of the euphotic zone increased down‐reservoir as silt settled out. Consequently, the euphotic zone standing crops were greatest mid‐reservoir. Insufficient light penetration was established as the principal limiting factor to primary production in the upper end of the reservoir. Decreased primary production in the lower end of the reservoir did not appear to be due to nutrient limitation. Comparison of sampling periods common to all years of the study showed that estimated net primary production increased 84% in 1970 over 1968.
Algal nitrogen fixation in Californian streams: seasonal cycles
Authors: HORNE ALEXANDER J. , CARMIGGELT COEN J. W. 
Published: May 2006

SummaryUsing the acetylene reduction technique, nitrogen fixation was measured in Rocky Creek, a small seasonally dry Californian stream. In the 3 years since 1970 nitrogen fixation varied seasonally and spatially, being highest in the early stages of colony growth in shallow, clear regions where there was little shade. The annual rate of N2‐fixation was similar to that found recently for Arctic tundra, but was greater than rates for Antarctic rivulets and less than rates for temperate rocky shores. A hetero‐cystous Nostoc appeared to be the sole organism responsible for this fixation. Nostoc occurred in variously sized gelatinous clumps on the stable boulders on which the co‐dominant alga, Ulothrix zonata, also grew. Maximum nitrogenase activity yielded 70 nmoles C2H4 mg‐1 drywt day‐1 and 123 nmoles C2H4cm‐2 day‐1. Estimated annual amounts of nitrogen fixed in 1971 ranged from 42 in shade to 360 mg N fixed m‐2y‐1 in the most favourable areas. Nostoc biomass reached 33 g dry wt m‐2 and peeled off each year in June‐July. Because Nostoc was confined to stable rocks the biomass per unit area of the stream as a whole was much less, ranging from 0.054 to 1.26 g dry wt m‐2 in the most favourable site. Nostoc was common throughout the length of Rocky Creek and also plentiful in eight out of ten adjacent streams but not in the main river (Eel River South Fork), probably due to high turbulence and turbidity. N2‐fixation in these streams makes a significant, but probably small contribution to the nitrogen income of the nitrogen‐deficient Eel River system. Nostoc colony establishment appears to be controlled by a combination of reduced turbulence and firmer attachment of the colonies to the substrate. Nostoc colony disappearance in June is probably due to nutrient depletion.
A survey of the invertebrates of four streams in The Moor House National Nature Reserve in Northern England
Authors: ARMITAGE P. D. , MacHALE ANGELA M. , CRISP DIANE C. 
Published: May 2006

SummaryThe Moor House Nature Reserve, Westmorland, is situated in typical north Pennine moorland and experiences a rigorous climate. Three of the streams arise between 700 and 750 m O.D. and the fourth at 590 m O.D. The sampling sites lie between 570 and 540 m O.D. and conditions in the streams range from slow‐flowing peaty‐bottomed reaches to typical fast‐flowing stony streams. Samples were taken in riffles and pools in May, August and October using the kick method. 111 taxa were recorded from the four streams, 90 of which were identified to the species level. The most abundant and widespread taxa were Leuctra inermis, L. fusca, Rhithrogena semicolorata, Elmis aenea and Chironomidae. Seasonal and annual variation in abundance of several species was marked with L. inermis most numerous in May, E. aenea and Chironomidae in August and R. semicolorata most abundant in October. The total number of animals caught was generally higher in riffles than in pools and the mean number per 60‐sec kick for riffles and pools, based on May, August and October samples between 1967 and 1970, ranged from 110 to 128 in the four streams. Capnia bifrons, Paraleptophlebia submarginata, P. cincta, Leptophlebia marginata, Centroptilum pennulatum, Plectrocnemia geniculata, Cyrnus trimaculatus, Lepidostoma hirtum, Hydropsychidae (larvae indet.) and Philopotamidae (larvae indet.), are all additions to the lists of previously studied groups on the Reserve. All the species of Tricladida, Annelida, Coleoptera, Hydrachnellae and Pisidium are here recorded for the first time for the Reserve.Great Dodgen Pot Sike supported the largest number of species and species groups (88) and was characterized by having water with the lowest pH (6.75) of all the streams and by having the most gentle gradient and a relatively stable bottom. The fauna is discussed and compared with that of the adjacent Cow Green area. Some of the differences between these areas may be attributable to the slightly greater variation in flow‐conditions and water chemistry in the Cow Green basin. Comparison with other areas in the British Isles are made briefly and it is suggested that habitat diversity may account for the species richness of the Moor House streams.
Variation in chemical composition of the River Frome, England, from 1965 to 1972
Authors: CASEY H. 
Published: May 2006

SummaryThis study covers a 7‐year period from 1965 to 1972, and shows the variation in flow, water chemistry and throughput of nutrients. The annual discharge of the River Frome varied considerably from year to year, ranging from a mean value of 4.48 m3 sec−1 in 1971 to one of 8.38 m3 sec−1 in 1966. The mean annual nutrient losses calculated over all 7 years of study from the River Frome catchment were: Nitrate 11.4 kg ha−1, phosphorus 0.49 kg ha−1 and potassium 8.4 kg ha−1. There has been an increase in annual throughput (in years of similar flow) of 21% in phosphate and 41% in nitrate from 1965 to 1972.
Laboratory experiments on factors affecting the activity of Gammarus pseudolimnaeus Bousfield
Authors: WALLACE RON R. , HYNES H. B. N. , KAUSHIK N. K. 
Published: May 2006

SummaryFactors such as current, light, food, substrate and time of year were found to influence the activity of specimens of Gammarus pseudolimnaeus maintained in stream tanks in the laboratory. Although there was seasonal variation, levels of diurnal and nocturnal activity were generally much higher when there was no current than when the water was running. Diurnal periodicity occurred but was not as pronounced as had been indicated in the field studies of previous workers. Although there was activity during the day, nocturnal levels were higher especially in specimens collected during the summer. When there was no current, and the lights were left on for 24 h, peak activity occurred at precisely the times when the lights normally would have been off. This strongly suggests that there is an endogenous component in the activity. The nocturnal activity showed a bigeminus pattern, and there was a seasonal change, with the general activity at its highest levels in summer. Activity was significantly greater during daylight both with and without current when there was no substrate present in the tanks. The behaviour of Gammarus appears to be complex and greatly influenced by combinations of the various factors.
Methods of sampling aquatic beetles in the transitional habitats at water margins
Authors: LANDIN JAN 
Published: May 2006

SummaryPopulations of water‐beetles (Hydrophiloidea) were studied during the ice‐free seasons of 2 years at a lake shore near Stockholm, Sweden. They were sampled by means of an absolute quantitative method (twenty‐four bottom cores/sample), extracted by Berlese‐Tullgren funnels, and a relative searching method (time‐catch or catch per unit effort). The sampling efficiency was tested by charging empty samples with known numbers of beetles. ‘Smaller’ species were less efficiently extracted than ‘larger’ ones. Absolute and relative population estimates of eight species were compared by means of regression analysis, the relative estimate being considered as the dependent variable. Only three statistically significant correlations were found, but a correlation always seemed to exist, and the relative estimates are considered as crude estimates. To obtain better ones when studying several species in one habitat much work is required, and then the advantages of the simple relative method disappears. The different sizes of the species were evaluated as sources of errors affecting the relative estimates. The estimates of the 'smaller’ species were more affected than the ‘larger’ ones. It is considered that relative population estimates would gain much if compared with independent absolute estimates. This seems to have been done rarely with invertebrates in aquatic habitats. Further, it is thought that behavioural extraction methods might be applied to several aquatic animal groups in eulittorals and littorals, saving much time compared with mechanical methods or hand sorting.
Seasonal patterns in abundance of water‐beetles belonging to the Hydrophiloidea (Coleoptera)
Authors: LANDIN JAN 
Published: May 2006

SummaryPopulations of Hydraena britteni Joy., Limnebius aluta Bedel (Hydraenidae), and Helophorus brevipalpis Bedel, H. strigifrons Thoms., Hydrobius fuscipes L. and Anacaena limbata Fabr. (Hydrophilidae) were studied from the break up of the ice until autumn or freezing at three different shores of a lake near Stockholm, Sweden. The beetles were generally found to frequent the zone immediately at the water's edge. Both larvae and imagines inhabit the uppermost 2 or 3 cm of the substrate. Two patterns in the seasonal abundance were found. (a) Maximal abundance during spring, minimal during summer, and sometimes a new, smaller maximum during late summer and autumn (Hydraena britteni, Helophorus strigifrons, Hydrobius fuscipes, Anacaena limbata, and perhaps Limnebius aluta). (b) An abrupt peak in abundance during July‐August and very low abundance at other times (Helophorus brevipalpis). Type (a) is probably the general one in this region and type of habitat. It fits a univoltine life cycle, where the beetles breed during early summer and hibernate as adults. In other climates this life cycle seems to be modified, partial second generations may occur or development is retarded and a new generation does not emerge until next spring. Type (b) is shown by a univoltine species much disposed to flight. The peak coincides both with its dispersal phase and the emergence of the new generation. The species is thought not to belong to a closed, stable habitat but to ephemeral waters in open landscapes. Its ecology is quite different to that of H. strigifrons, which is considered to belong to more closed, stable habitats. Patterns similar to type (a) are also shown by Laccophilus spp. (Dytiscidae) and Haliplus spp. (Haliplidae) according to the literature. This may be an adaptation to the probable danger of being trapped in ice during winter. Like the water‐beetles these two beetle groups also mostly leave the water margin during autumn. The pattern of type (a) of most Hydrophiloidea seems to be geared to the amounts of plant remnants in the littoral, imagines and some larvae being most abundant when the amounts are maximal, i.e. during spring. The plant material probably offers food and cover. It disintegrates rapidly during summer and a new maximum is reached next spring. The pond‐like habitat, which may develop behind reeds is compared with ephemeral ponds. Both may be regarded as unstable habitats, each passing through a series of predictable changes. The difference is the final stage, often disastrous when a pond dries out, but seldom so in a lake when the water line moves outwards in the littoral during summer.
Nitrogen nutrition of Myriophyllum spicatum: variation of plant tissue nitrogen concentration with season and site in Lake Wingra
Authors: NICHOLS DALE S. , KEENEY DENNIS R. 
Published: May 2006

SummarySamples of water, sediment and Myriophyllum spicatum were collected from four weedbed sites in Lake Wingra, a small hypereutrophic hardwater lake in Madison, Wisconsin, several times during the 1972 and 1973 growing seasons, and analysed for various forms of N. The concentrations of inorganic N in the lake water were quite similar at all sites. The differences in the total N content of the Myriophyllum tissue from site to site directly related to the levels of available sediment N, indicating a dependence upon the sediment as a N source. Myriophyllum tissue N concentrations (ash and moisture‐free basis) were highest in spring, decreased steadily during the summer, and increased again in the fall. Myriophyllum apparently grows very little during the winter, but continues to accumulate N. The death and decay of a considerable portion of the Myriophyllum in the fall contributes insignificant amounts of N directly to the lake water. Nitrogen does not appear to be limiting Myriophyllum spicatum growth in Lake Wingra.
Environmental dependence of manganese and zinc in the scales of Atlantic salmon, Salmo salar (L) and Brown trout, Salmo trutta (L)
Authors: ABDULLAH M. I. , BANKS J. W. , MILES D. L. , O'GRADY K. T. 
Published: May 2006

SummaryAnalysis of manganese and zinc concentrations in the scales of salmon and trout from a number of sites showed significant dependence of the levels of these metals in the scales on the levels in the environment. There is some evidence to suggest that in trout scales there is a minimum concentration of zinc above which there is a direct proportion between environmental and scale concentration. It is also possible that the response of trout to environmental zinc differs from that of salmon.