bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal changes in the abundance and distribution of planktonic rotifers in Grasmere (English Lake District)
Authors: ELLIOTT JUDITH I. 
Published: May 2006

SUMMARY. The planktonic rotifers of Grasmere, a small lake in the English Lake District, were studied from August 1969 to December 1972. Twenty‐four species were recorded but five were very rare. The remaining species were divided into three groups according to their seasonal occurrence: spring to autumn species (Keratella quadrata. K. cochlearis, Gastropus stylifer, Asplauduia priodonta. Kellicottia Umgispina, Conochilus hippocrepis)., spring to early summer species (Polyarthra dolichoptera, Synchaeta tremula, S. pectinata, S. stylata, S. oblonga, C. unicornis), summer to autumn species (Polyarthra vulgaris, P. major. Filinia terminalis, S. grandis, Ploesoma hudsoni, Trichocerca capucina, T. similis). The months in which each species was abundant are given. Keratella quadrata and Filinia terminalis were most abundant in the deepest stratum, Kellicottia longispina and Conochilus spp. were most abundant in the upper and middle strata. Trichocerca spp. showed no pronounced vertical distribution, and all the remaining species were most abundant in the upper stratum. Keratella cochlearis and Kellicottia longispina attained their highest densities over a wide range of temperature and oxygen concentration. Filinia terminalis, Conchihis spp., Asplanchna priodonta. K. quadrata, and Polyarthra spp., attained their highest densities within a narrow range of temperature and oxygen concentration. Optimum ranges are given for each species.Major changes occurred between 1971 and 1972 when Asplanchna priodonta. Kellicottia longispina, Conochilus unicornis and Filinia terminalis increased in abundance, whilst Keratella quadrata. Gastropus stylifer, C. hippocrepis, Polyarthra spp., Synchaeta spp. and Ploesoma hudsoni decreased in abundance. These changes are discussed in relation to the temperature and oxygen requirements of each species and also to the probable enrichment of the lake after the opening of a new sewage works in June 1971.
The spring development of phytoplankton in Lake Erken
Authors: BOSTRÖM BENGT , PETTERSSON KURT 
Published: May 2006

SUMMARY. In Lake Erken there is a regular phytoplankton peak at ice‐breakup in the spring. Pechlaner (1970) studied the spring outburst of 1960. We carried out a similar study in 1973, when the climatic factors were completely different, with only 10 cm of ice and almost no snow. Thus, due to light penetration, there was a high phytoplankton biomass under the ice as early as March. Stephanodiscus astraea (Ehr.) Grun. and Asterionella formosa Hass. dominated the biomass during the spring development in 1973 instead of the normally dominating S. hantzschii v. pusillus Grun.The nutrient decrease was slower in 1973 than in 1960. A comparison of carbon assimilation and the decrease of nitrate and phosphate indicate sufficient nutrient supply in 1973. In 1960, the population grew logarithmically until the nutrients became limiting. In 1973, the average biomass was greater, but the mean probable primary production was only half that of 1960. From the activity coefficients for the 2 years it is also clear that, in 1960, S. hantzschii v. pusillus was highly productive during its short but intensive growth period. Its minute size and high surface/volume ratio enabled it to take up nutrients rapidly and efficiently. The chlorophyll content of S. astraea in 1973 was only half as much as that of S. hantzschii v. pusillus in 1960. Since the light conditions under the ice in March 1973 were more unfavourable than during the exponential phase of 1960, production was much lower.
Ecological studies on Oligochaeta inhabiting depositing substrata in the Irwell, a polluted English river
Authors: EYRES J. P. , WILLIAMS N. V. , PUGH‐THOMAS M. 
Published: May 2006

SUMMARY.
Oligochaete worms dominate the macroinvertebrate fauna of the River Irwell, in north west England. The river is polluted by domestic and industrial wastes. Tubificids constituted 86.8% of the worm fauna, with three dominant species; Tubifex tubifex (Müller), representing 43.1% of the total oligochaetes, Limnodrilus hoffmeisteri Claparède, representing 26.8% and Limnodrilus udekcmianus Claparède, representing 16.7%. The Naididae were the next most abundant worms, representing 6.1% of the oligochaete fauna, with Nais elinguis Müller comprising 5.0%. T. tubifex and L. hoffmeisteri were abundant along the length of the river, but reached their greatest numbers in the organically polluted lower reaches at Agecroft and Salford. The density of L. udekemianus was low in the Irwell above the entry point of the heavily polluted River Roch, but high below this point. N. elinguis was abundant above the Roch entry point and scarce below it.In the three dominant tubificids, the main population recruitment occurred during the summer months (April to September for T. tubifex, May to November for L. hoffmeisteri and June to October for L. udekemianus). In N. elinguis, there was massive recruitment in April.
A review of the biology of British Naididae (Oligochaeta) with emphasis on the lotic environment
Authors: LEARNER M. A. , LOCHHEAD G. , HUGHES B. D. 
Published: May 2006

SUMMARY.
Naidids live in a wide range of aquatic habitats but are particularly important numerically as part of the benthic fauna of rivers with stony substrates. In general they graze on bacteria and algae although some, particularly Chaetogaster spp., are mainly predaceous, and C. limnaei vaghini is a parasite of molluscs, chiefly Gastropoda. Food selection seems to be based largely on particle size although the food quality of the particles within the appropriate size‐range influences rates of growth and reproduction.Major factors determining the distribution and abundance of naidid species are the nature of the substratum and the presence and kind of vegetation. Plants with a highly dissected form, a thick growth habit, and which permit the greatest periphyton development generally support the most abundant naidid populations. The oligochaete fauna of coarse substrates (stones and gravels) is often dominated by the Naididae but both species‐richness and abundance of naidid populations are generally reduced where fine substrates (silts and muds) occur. The occurrence of worms within the substratum is also determined by its nature; naidids penetrate to depths of 20–70 cm in coarse substrates but rarely penetrate below 6 cm in mud. The principal factor limiting both depth penetration and the dominance of naidids in fine substrates is probably oxygen availability.Naidids reproduce both asexually and sexually, the former method predominating for most of the year. Asexual reproduction usually involves the budding‐off of zooids but a few species fragment. Sexual reproduction is often infrequent; populations of some species produce few or no sexually mature individuals. In mature worms asexual reproduction virtually ceases. In populations that produce mature individuals there is apparently one sexual generation a year, usually occurring during the summer and autumn. Adults die soon after laying their cocoons.In general, naidids are most abundant during the summer months when rates of growth and asexual reproduction are stimulated by higher temperatures and a plentiful supply of food. A few species, however, e.g. Nais elinguis and Paranais litoralis, are more abundant in the spring.The response of naidid species to different kinds of pollution is varied but generally organic enrichment of rivers which have stony substrates results in a considerable (ten‐ to twenty‐fold) increase in naidid abundance. Nais elinguis, N. barbata, N. communis, N. variabilis, and Chaetogaster diaphanus are often abundant in such rivers, the foremost species reaching densities of 200 000 m−2. Nais alpina, N. bretscheri, and N. pardalis appear to be relatively intolerant of organic enrichment. A substantial increase in naidid abundance is also promoted by the deposition of biologically inert particles (coal dust, china clay, sand) on the river bed.The importance of Naididae in relation to pollution surveillance of fresh waters is discussed.
Early composition and biomass of the crustacean Zooplankton in Bough Beech Reservoir, south‐east England
Authors: MUNRO I. G. , BAILEY R. G. 
Published: May 2006

SUMMARY.
The crustacean Zooplankton community in Bough Beech, a flooded valley reservoir in south‐east England, was investigated in the early years of impoundment. The nutrient status and phytoplankton were typical of a lowland eutrophic lake, and this was reflected in the composition of the Zooplankton. At any given time, the latter comprised one or two cladoceran and two or three copepod species, of which the cladocerans were generally numerically predominant. Marked alterations in the Zooplankton community occurred in the first 2 years of the study and were related to changes in predation pressure by fishes. By the end of the third year, the composition of the Zooplankton community had stabilized.The cladoceran biomass was normally in excess of that of the copepods, with maxima in spring and autumn. Peaks in copepod biomass occurred within 2 months of those of the Cladocera.
Colonization of artificial substrata by macro‐invertebrates in a stream and variations according to stone size
Authors: KHALAF G. , TACHET H. 
Published: May 2006

SUMMARY. Plastic cages containing artificial substrata were placed on the stony bottom of a stream in a section where the environmental conditions appeared to be homogeneous. The section was divided into eight equal sub‐sections (A‐H) and four cages were placed in each sub‐section. The stone‐size of the artificial substrata was similar within each cage but differed between the four cages with average diameters of 14, 24, 48 and 96 mm, respectively. The baskets were removed one month later and the catches of macro‐invertebrates were recorded.Analysis of the catches (density and number of taxa in each cage) revealed no significant differences in connection with the position of the cages in the section of stream. Cages with 48‐mm stones contained the least abundant fauna. The taxa which colonized cages with 14‐ or 24‐mrn stones were more numerous than those collected from cages with 48‐ or 96‐mm stones.Statistical analysis by laxon confirmed the preceding results. Variability in connection with the position of the cages along the section of stream was never significant. A little more than half the taxa were distributed independently of stone size but always showed a contagious type distribution. The density of the other taxa was higher, either in cages with 14‐ or 24‐mm stones (particularly Gammarus) or only in cages with 96‐mm stones (especially Hydropsyche). Only one taxon was more abundant in cages with 48‐mm stones, the type of substratum in which the overall density was lowest.Catches in the cages were not the same as those taken with a Surber sampler because the two samplers did not take samples from the same habitats and also because the baskets offered a more specialized habitat than the surrounding bottom. The basket with 24‐mm stones gave the least distorted picture of the natural population.
Algal bioassay of the water from two linked but contrasting Welsh lakes
Authors: HAPPEY‐WOOD CHRISTINE M. , PENTECOST ALLAN 
Published: May 2006

SUMMARY.
A comparison of the potential water fertility of two linked lakes, Llyn Peris and Llyn Padarn, was carried out over a year using Asterionella formosa as the test organism in batch cultures. In unenriched lake water, growth was more rapid in Padarn water during autumn‐winter‐spring, but there was no significant difference between growth in water from the two lakes during the period of thermal stratification. Mean growth rates in treatments with additions of nitrogen and chelated iron were not significantly different from unenriched water samples, both between treatments and lakes during thermal stratification. Growth in water from both lakes was increased greatly by addition of phosphate. Maximum growth rates occurred on addition of nitrogen, phosphate and chelated iron, and there was no significant difference between growth rates in this treatment for the two lakes throughout the year. Comparisons of mean growth rates in bioassays by Tukey's interval estimate showed significant differences between other treatments and the two lakes. The potential fertility of water samples from the two lakes differs more during mixed water conditions than in the period of thermal stratification.Inhibition of A. formosa growth was recorded four times in unenriched filtered water from Peris, once on addition of nitrogen and once on addition of iron. Inhibition was alleviated by the addition of nutrients.The addition of diluted sewage effluent which enters the drainage system between the two lakes, resulted in similar rates of growth of A. formosa in water from both lakes.Results of the bioassays are discussed in relation to differences in phytoplankton between the two lakes. Although A. formosa will grow in samples of unenriched lake water from Peris, other features, including a shorter retention time of water, lower level of incident radiation and, occasionally, inhibitory substances in the lake water, contribute to the rare occurrence of this diatom in Peris. Padarn is enriched by sewage effluent which aids the growth of A. formosa.
Population dynamics and production of the tropical freshwater shrimp Caridina nilotica (Decapoda: Atyidae) in the littoral of Lake Sibaya
Authors: HART R. C. 
Published: May 2006

SUMMARY.
Seasonal changes in population structure, standing stock levels and production of Caridina nilotica were studied at three sites in the littoral margins of subtropical Lake Sibaya between January 1975 and March 1976. Average population density at these sites declined from a maximum of c. 1400 to a minimum of c. 350 individuals per m2 (3.4–0.4 g m−2 dry wt) during the study, possibly as a result of emigration into peripheral vegetation inundated by rising lake levels.Shrimps bred perennially and, although egg stocks and instantaneous birth rates (b) were highest during summer, no corresponding increases in populaton density were observed, suggesting that the seasonally higher birth rates were offset by higher mortality rates. Population size structure and size‐specific sex ratios did not change seasonally to any marked extent. Relative abundance declined with size and females grew larger than males. Clutch size increased linearly as a function of female carapace length.Estimates of overall mean annual somatic production (g m−2 year−1 dry wt) for the three sites between January 1975 and January 1976 ranged between c. 132 (egg‐ratio method), 37.5 (summation of growth increments) and 24 (Hynes‐Hamilton method) at an annual mean standing stock level of 2.7 g m−2 dry wt (calorific value, 20.34 kJ g−1 dry wt). Production at sites 1, 2 and 3 decreased in line with declining annual mean standing stocks (5.32, 3.67 and 0.23 g m−2, respectively). The growth increment method gave an overall mean annual P/B value of 13.9. Egg production amounted to a further 5.6, 3.6 and 0.1 g m−2 year−1 dry wt (calorific value, 28.01 kJ g−1) at sites 1, 2 and 3, or 2.7 g m−2 year−1 on average.
Nutrient retention and transformation in relation to hydraulic flushing rate in a small impoundment
Authors: TURNER RALPH R. , LAWS EDWARD A. , HARRlSS ROBERT C. 
Published: May 2006

SUMMARY. The fluxes of water, chloride, silicale and various forms of nitrogen and phosphorus into and out of a 3925 ha impoundment (Lake Taiquin) in north Florida were examined over a 3 year period. Annual hydraulic flushing rates for the lake varied by a factor of more than 2 during the study period and provided an opportunity to examine the effect of flushing rate on nutrient cycling within the lake. The results support the hypothesis that nutrient retention and transformation in lakes and impoundments with high flushing rates (> 1 year‐1) are appreciably influenced by annual variations in flushing rates. Higher fractions of input silicate and total phosphorus were retained by Lake Taiquin during the years with average flushing rates (8 year‐1) than during a year with abnormally high flushing rate (16 year‐1). Nitrogen was not appreciably retained during any of the three study years, and thus N: P ratios in the lake outflow were higher than in the inflow.Phytoplankton productivity was appreciably higher (70%) during the year with the higher flushing rate, apparently in response to higher reactive phosphorus concentrations in the lake and perhaps to a higher standing crop of phytoplankton during that year. Reactive phosphorus and dissolved inorganic nitrogen inputs could account for only about 30% and 25%, respectively, of the phosphorus and nitrogen required to support observed photosynthetic rates in all three study years. Recycling of nutrients apparently accounted for most of the remainder, although nitrogen fixation could not be ruled out as a factor in the nitrogen budget.
In situ life table of a subtropical copepod
Authors: WYNGAARD GRACE A. 
Published: May 2006

A life table of a subtropical population of Mesocyclops edax(Copepoda: Cyclopoida) was constructed from a cohort of individuals reared in enclosures in a small, eutrophic lake.
The lake population was sampled concurrently to determine age structure, per capita birth, death and growth rates, body size and clutch size.
Maturation times of enclosed males and females were 9.3 and 11.4 days, respectively. The population growth rate. r. was estimated to be 0.18 females day‐1 for the enclosed population, but approximated zero on most dates in the lake population. Mortality was low in the enclosures which excluded predators and high in the field population exposed to planktivorous fish and Chaoborus.
The means and variances of several fitness traits are related to the specific environment. The enclosure approach promises to be a useful tool in the study of zooplankton life history variation.
The age, growth and reproduction of the stone loach Noemacheilus barbatulus (L.) in a Dorset chalk stream
Authors: MILLS C. A. , WELTON J. S. , RENDLE E. L. 
Published: May 2006

SUMMARY.

In this highly productive chalk stream the stone loach, sampled by electrofishing over a 30 month period, had a high growth rate reaching a mean length of 65 mm in 1 year and 93 mm in 2 years. The fish were short‐lived in contrast to most slow‐growing populations in the U.K. and Finland with 11 group fish comprising 8.8% and III group fish only 1.1% of the total number.
The loach were fractional spawners: a 75 mm female produced an estimated 10,620 eggs between late April and early August totalling 46% of the loach's initial weight.
In March and April some small 0 group females contained only poorly developed eggs and up to 10% of 0 group fish may have failed to spawn.
Amongst loach >52 mm in length in March and April there was an exponential relationship between absolute fecundity and fish length but no relationship between relative fecundity and length. There was. however, a relationship between fish length and both gonadosomatic index and maximum egg size, which may indicate that large fish began to spawn first.
The logseries distribution and Mountford's similarity index as a basis for the study of stream benthic community structure
Authors: SHEPARD RICHARD B. 
Published: May 2006

SUMMARY. 1. Of the various approaches to studying species‐abundance patterns in aquatic ecosystems (particularly streams) the logseries distribution is the most appropriate. The distribution parameter, α, is readily estimated and goodness‐of‐fit of the model to the data can be estimated.2. A method exists which uses a to calculate an index of similarity from which cluster dendrograms can be constructed and the clusters tested for significant differences. Assumptions and calculations are presented.3. Procedures are illustrated, with examples from Idaho streams, and approaches to interpreting the results are included.4. Studies of stream macro invertebrates can fulfill the assumptions of the logseries distribution but cannot meet those of commonly used diversity indices.
The effect of temperature on photosynthetic and respiratory electron transport system activity in the shallow and deep‐living phytoplankton of a subalpine lake
Authors: PRISCU JOHN C. , GOLDMAN CHARLES R. 
Published: May 2006

SUMMARY. 1. The influence of temperature on in vivo photosynthetic and in vitro respiratory electron transport system (ETS) activity was determined over the season for the 3 m (warm‐water) and a 20m (cold‐water) phytoplankton communities in Castle Lake. The optimum temperature of photosynthesis at 3 m (X̄=20.8°C) was significantly higher than the average optimum at 20 m (X̄=14.8°C).2. Seasonally, the photosynthetic temperature optimum increased when the blue‐green alga Chroococcus limneticus Lemm. was present. The temperature characteristics of this organism were maintained even after it had settled into the cold water of the hypolimnion.3. Temperature optima were not significantly different in experiments conducted under limiting or saturating photosynthetic photon flux densities (PPFD).4. Short‐term (1 h) preincubations with dissolved inorganic nitrogen (DIN) (≃80 μg NH4NO3‐N l−1) had little effect on the temperature characteristics of photosynthesis while the longer (>24 h) incubations provided by a whole‐lake epilimnetic DIN addition (≃75 μg NH4NO3‐ N l−1) significantly lowered the photosynthetic temperature optimum to 12.5°C. Once this epilimnetic DIN was depleted the optimum roseto25°C, a value higher than that present before the enrichment, which coincided with the growth of C limneticus.5. Respiratory ETS activity usually began to inactivate between 19 and 20°C. However, when C. limneticus was abundant the inactivation temperature was often greater ihan 25°C.6. The average energy of activation (E) and Q10 value for the 3 m community (15.9 kcal mol−1 and 2.6 respectively) were significantly higher than those at 20 m (14.2 kcal mol−1 and 2.4 respectively). Seasonally, the highest E and Q10 values of ETS activity occurred during the late‐summer bloom of C. limneticus.7. These results demonstrate that the epilimnetic and hypolimnetic phytoplankton communities in Castle Lake are physiologically distinct with regards to their temperature characteristics.
Community structure in some southern English streams: the influence of species interactions
Authors: HILDREW ALAN G. , TOWNSEND COLIN R. , FRANCIS JEANETTE 
Published: May 2006

SUMMARY. 1. The results of a survey of thirty‐four stream sites, differing in pH and invertebrate species richness, indicated that the pool of locally available, suitably adapted species was smaller in the acid streams. This plays a part in determining the general pattern of lower species richness at more acid sites.2. Diversity of feeding categories increased with species richness, indicating that a greater range of food resources was available in the less acid, more species‐rich communities.3. The pattern of predation varied with pH and species richness. The numbers of large insect predators were lower in the less acid, more species‐rich communities and this was correlated with the presence of fish.4. A detailed study of the guild of detritivorous stoneflies in four streams differing in species richness provided evidence that density compensation occurs, niche width decreases and niche overlap declines as species richness increases.5. We discuss the roles that competition and predation play in determining the structure and richness of stream invertebrate communities.