bluuebunny/crossref_metadata_2025 huggingface dataset:
Further observations on limnetic zooplankton in a small lake and two enclosures containing fish
Authors: SMYLY W. J. P.
Published: May 2006

SUMMARY.
In a small lake (Blelham Tarn, English Lake District) two plastic cylinders, each of which extends from the lake surface to the bottom sediments and encloses 18 000 m3 of water, were used to investigate effects of enclosure on the zooplankton. This paper describes observations from March 1973 to October 1974 and is the second part of a report on a project spanning 4 years.

Seasonal population densities of the more abundant species were essentially similar to those observed in the first part of the project, despite large changes in algal and predator populations. In the enclosures, fish (mostly Perca fluviatilis) populations are known from observations by divers to have been large in the period under consideration and small in the first part of the project. Populations of Chaoborus larvae in the enclosures were small at all seasons from March 1973 to October 1974.
The fauna of the muddy sediments of Lough Neagh, with particular reference to eutrophication
Authors: CARTER C. E.
Published: May 2006

SUMMARY.
The main groups of animals found in the muddy sediments of Lough Neagh were Chironomidae (Diptera) and Oligochaeta (mainly Tubificidae). At 8 m depth, the average biomass of the main species in these groups was: Chironomus anthracinus, 2.64gm−2; Procladius, 342.8 mgm−2; tubificids (Tubifex, Potamothrix, Aulodrilus, Limnodrilus), 418.7mgm−2. At 25m depth C. anthracinus and Procladius were less abundant, C. plumosus was present and among the tubificids Limnodrilus had a higher density (up to 50000m−2) often an order of magnitude greater than at 8m. Kinnego Bay, a semi‐enclosed, polluted area of the lough, had fewer chironomids than the open lough, with chiefly C. plumosus and Procladius. Limnodrilus was more abundant than at 8m. Dero obtusa (Naididae) was also present, sometimes in large numbers (31000m−2).

The response of this fauna to eutrophication in L. Neagh appears to be a diminution in the number of species present, with C. plumosus gradually replacing C. anthracinus as the dominant Chironomus, and tubificids, particularly Limnodrilus, becoming more abundant, A further stage, shown in Kinnego Bay, has Procladius as the most numerous' chironomid. Average total biomass at the three sites was 3.9gm−2 at 8m, 13.2gm−2 at 25 m in the main lake, 2.8gm−2 in Kinnego Bay. At 8m depth, C. anthracinus contributed 76% of the total biomass, at 25m Limnodrilus contributed 74% and C. anthracinus 15%, and in Kinnego Bay, Limnodrilus contributed 40%, C. plumosus 28% and Procladius 20%.
The rates of dry matter and nutrient loss from decomposing Potamogeton pectinatus in a brackish south‐temperate coastal lake
Authors: HOWARD‐WILLIAMS C. , DAVIES BRYAN R.
Published: May 2006

SUMMARY.
Decomposition of Potamogeton pectinatus in Swartvlei, a southern African coastal lake, followed an exponential pattern of decay. The rale constant was 0.0205 day−1 and decay was virtually complete after 158 days. The original stock of ash, phosphorus and potassium was lost more rapidly than dry matter in the initial stages of decomposition due to leaching. Almost the entire stock of potassium and 60% of the phosphorus was lost in the first 7 days. The proportions of N and P in the decomposing detritus increase significantly in the final stages of decomposition, providing a rich food source for the abundant filter‐feeding animals of the littoral zone. The decomposition rate of P. pectinatus is compared with that of other aquatic macrophytes and the significance of the relatively rapid decay rate of this species in the ecology of Swartvlei lake is discussed.
Decomposition of aquatic biota and sediment formation: bound lipids in algal detritus and lake sediments
Authors: CRANWELL P. A.
Published: May 2006

SUMMARY.
Organic detritus resulting from microbial attack on algal material contains lipids directly extractable by organic solvents and also contains bound lipids, obtained by solvent extraction following acid hydrolysis. Differences between the composition of bound and extractable n‐alkanes, n‐ and branched/cyclic alkanoic acids from each source are attributed to a major bacterial input to these bound lipid classes. Similarities in composition between bound lipid classes of algal detritus and corresponding classes in a lake sediment support earlier suggestions of a considerable bacterially‐derived contribution to sedimentary bound lipids.
Curie point pyrolysis mass‐spectrometry of fulvic acids from Tjeukemeer, The Netherlands
Authors: DE HAAN H. , DE BOER T. , HALMA G.
Published: May 2006

SUMMARY.
Curie point pyrolysis mass‐spectrometry of freshwater fulvic acids from Tjeukemeer indicates the presence of polysaccharides, amino sugars, proteinaceous material and phenols. These results resemble those of the pyrolysis of soil fulvic acids. However, freshwater fulvic acids may be richer in aliphatic components than those from soil.
Heterotrophic activity, glucose uptake and primary productivity in Lake Kinneret*
Authors: CAVARI B. Z. , HADAS O.
Published: May 2006

SUMMARY.
Chlorophyll, ATP and glucose concentrations as well as glucose uptake rate and primary production were determined every 2–4 h during three 24–h surveys in Lake Kinneret. In spite of the fluctuations in glucose uptake rate, the estimation of the daily glucose uptake rate from a single sampling carried out at 10.00 hours is justified. The same applies also for the primary production.

Routine bi‐weekly determinations of primary production and glucose uptake rate were carried out from October 1976 to July 1977. No correlations were found between glucose uptake rates and ambient concentrations of ATP, chlorophyll and glucose.

The glucose uptake rate showed two distinct seasonal patterns; the period which was dominated by the Peridinium (January‐April) and the rest of the year. In the former period the percentage of glucose‐carbon utilized out of the carbon formed in the water column by the photosynthetic activity, fluctuated between 1 and 9%, and in the latter period fluctuated between 5 and 37%. The yearly average was 11.1%, SD 9.8.
Fluorometric measurement of alkaline phosphatase activity in algae
Authors: HEALEY F. P. , HENDZEL L. L.
Published: May 2006

SUMMARY.
Using both cultures of algae and natural populations, alkaline phosphatase activity located on the cell surface has been measured by a fluorometric procedure. This was done in order to establish optimum standard conditions for the measurement of this activity as an indicator of phosphorus deficiency and to provide a means of interpreting alkaline phosphatase measurements on natural phytoplankton populations. A concentration of 10 μM o‐methylfluorescein phosphate saturates or nearly saturates the reaction in a variety of situations. In most trials, rates increased with temperature to or beyond 35°C. Optimum pH values in the range 7–10 were observed. In six of the algae examined, maximum alkaline phosphatase activities were dependent on external calcium at 100 μM or more. One alga, Synura uvella, showed acid phosphatase activity, peaking at pH 5–6, induced by phosphorus deficiency. Based on comparisons between P‐sufficient and P‐deficient cultures, alkaline phosphatase activities in excess of 0.1 μmol o‐methylfluorescein phosphate hydrolysed per mg dry weight per h or 0.1 μmol per μg ATP per h are suggested as indicative of phosphorus deficiency.
A re‐valuation of the Araphidineae/Centrales index as an indicator of lake trophic status
Authors: BRUGAM RICHARD B.
Published: May 2006

SUMMARY.
Comparisons of pre‐ and post‐settlement diatom assemblages from the sediment of twenty‐five Minnesota lakes reveals that Stephanodiscus hantzschii percentages are more consistent indicators of human disturbance than the Araphidineae/Centrales (A/C) index. In a set of eighty surface sediment samples from lakes whose water chemistry is known, S. hantzschii, a centric diatom, is abundant as a microfossil in lakes with total phosphorus > 15 μg I−1 and alkalinity > 1.5 m‐equiv. I−1. High Araphidineae/Centrales indices are characteristic of lakes with only moderate total phosphorus levels and very low alkalinities.
Haementeria costata (Hirudinea: Glossiphoniidae), a leech new to Britain
Authors: ELLIOTT J. M. , MUGRIDGE R. E. R. , STALLYBRASS H. G.
Published: May 2006

SUMMARY.
The European leech Haementeria costata is recorded in Britain for the first time and is described in detail. A key is provided to distinguish H. costata from other species of leeches in Britain, and the literature on the ecology of H. costata is summarized.
A key to the larvae of Sialidae (Insecta: Megaloptera) occurring in the British Isles
Authors: ELLIOTT J. M. , O'CONNOR J. P. , O'CONNOR M. A.
Published: May 2006

SUMMARY.
The discovery of a third species of alderfly (Sialis nigripes) in Britain and Ireland necessitates a new larval key for the group in these islands. Characters are now provided to distinguish the larvae of the three species, and their habitat and distribution in the British Isles are outlined.
Temporal and vertical distribution of ciliophoran communities in the benthos of a small eutrophic loch with particular reference to the redox profile
Authors: FINLAY B. J.
Published: May 2006

SUMMARY.
The ciliate communities occurring at three benthic sites in a small eutrophic loch have heen investigated over a 2‐year period. Two characteristics of the community were studied in detail, the pattern of vertical distribution within the sediment and the temporal distribution of ciliates occurring in the surface sediment. The relationships between ciliate distributions and the environmental factors recorded were analysed by multiple regression. Significant relationships were revealed between vertical distribution of ciliates and the sediment redox (Eh) profile, the larger ciliate communities being associated with regions of higher potential. Other factors such as sediment density, organic matter, temperature and daylength, combined with other indicators of benthic metabolism (sulphide ion activity (Es2−), pH, oxygen flux) were selected in the regression analysis as accounting for much of the variation in the depth distribution of ciliates.

In analysing the temporal distribution of ciliates in the surface sediment, numbers were inversely related to Eh, Es2− and oxygen flux, a result of the upwards migration of reducing conditions and greater microbial activity in the sediment surface during the summer. Daylength, temperature, organic carbon and benthic chlorophyll‐a were also selected as accounting for much of the variation in ciliate number. It is proposed that the large increases in number and biomass of surface‐sediment cilates in the summer months resulted from an intolerance of reducing conditions developing immediately beneath the surface and the increased productivity of the benthos as a whole during this period.

Methods are also described for the construction, calibration and operation of electrodes used in measuring Eh, Es2− and oxygen flux in the freshwater benthos. Data recorded for these three variables revealed similar seasonal patterns at each site in each of two consecutive years.
Characteristics and classification of the lakes of Signy Island, South Orkney Islands, Antarctica
Authors: HEYWOOD R. B. , DARTNALL H. J. G. , PRIDDLE J.
Published: May 2006

SUMMARY.
The lakes of Signy Island (60° 43′S, 45° 38′W), South Orkney Islands, Antarctica, provide a unique laboratory for the study of many processes including natural eutrophication. Current relationships between the lakes have been examined by principal components analysis of environmental data from a long‐term monitoring programme. The results from the analysis have been combined with some biological data to provide a classification scheme for the lakes. The study has produced a valuable baseline for use in future research.
Bdelloid rotifers and nematodes in a small Italian stream
Authors: ZULLINI ALDO , RICCI CLAUDIA
Published: May 2006

SUMMARY.
The bdelloid rotifers and nematodes of a small clean watercourse in the area surrounding the Po river near Parma have been studied. The samples were collected at two sites 400 m apart. The species found in twelve collections of benthos between May 1977 and June 1978 were eighteen belonging to Bdelloidea and forty‐seven to Nematoda (Tylenchida have not been considered). Nearly all the bdelloid species were oligosaprobic or beta‐mesosaprobic; the Shannon index of diversity was 3.0 at the first site and 2.4 at the second. Among the Nematoda the dominant species were Paraplectonema pedunculatum and Paraphanolaimus anisitsi which were not previously recorded for Italy. Nearly all nematodes are microphagous; predators represent only 10% of collected specimens. Polluted water indicator species (Secernentia group) were only 3.5% of the total nematodes recorded. Most rotifers and nematodes did not show seasonal fluctuations in numbers. The two sampling sites do not seem to have substantial differences in the taxocoenosis of Rotifera and Nematoda; their percentage of similarity is 69% and 79% for the two classes respectively.
Cadmium and calcium interactions in the freshwater amphipod Gammarus pulex
Authors: WRIGHT D. A.
Published: May 2006

SUMMARY.
The accumulation of cadmium from an experimental medium by the freshwater amphipod Gammarus pulex is described.

Much of the uptake is internal as opposed to adsorption on the body surface, and after an apparent saturation of the exoskeleton the hepatopancreas becomes an increasingly important site of cadmium storage. The haemolymph cadmium concentration reaches a high level compared with marine crustaceans, achieving a concentration factor (ratio of internal Cd/ external Cd) of 100 after about 60 h uptake.

The cadmium uptake process is severely inhibited after exposure of experimental animals to 0.5 mM 2:4 Dinitrophenol, indicating the mediation of an active process. This fact together with the negative relationship between cadmium uptake rate and the calcium concentration of the animal suggests that cadmium accumulation by this species may be at least partially accounted for by a process of ‘accidental’ active cadmium uptake, with cadmium substituting for calcium on a calcium regulatory mechanism.

As yet it has not been possible to establish a true stoichiometric relationship between the two metals. Although calcium influx and cadmium uptake (influx) rates are similar over a wide range of external concentrations, calcium influx is clearly inhibited by a low external ratio of cadmium to calcium. This indicates that the relationship between the two metals is far from an equimolar one and the possibility of non‐competitive inhibition of calcium influx by cadmium cannot be eliminated.
Distribution of aquatic Oligochaeta in the Finnish Lake District
Authors: SÄRKKÄ JUKKA , AHO JORMA
Published: May 2006

SUMMARY.
The distribution of oligochaetes was examined at sampling stations grouped into three types: (1), in eutrophic and dystrophic areas or in areas polluted by pulp‐mill wastewaters; (2), slightly eutrophic stations; (3), ‘clean’ stations unaffected by sewage or other inputs. Limnodrilus hoffmeisteri and Potamothrix hammoniensis were practically the only species in group 1, and the same species accounted for two thirds of the total numbers in group 2, although Peloscolex ferox and some other species also occurred. At the cleanest stations the dominating species were P. ferox, Psammoryctides barbatus, Stylodrilus heringianus and Tubifex tubifex. A factor analysis showed that L. hoffmeisteri and P. hammoniensis were associated with increased nutrients and water colour in the lower part of the epilimnion. In the metalimnion the relationship of S. heringianus and P. ferox to water colour and total nitrogen differed from that of L. hoffmeisteri and P. hammoniensis. Winter oxygen content was important for S. heringianus.
Genotypic succession in the cyclomorphosis of Bosmina longirostris (Cladocera)
Authors: BROCK DAVID A.
Published: May 2006

SUMMARY.
The pattern of cyclomorphosis of Bosmina longirostris was followed over a 21‐month period in Lake Travis, Texas. Appreciable variation was observed in body size and in the lengths of antennules and mucrones. Electrophoresis of clonal isolates collected over the period of study showed a seasonal cycle in esterase phenotypes. A definite association was demonstrated between the esterase phenotypes and morphologies of these clonal isolates. Individuals of one esterase phenotype were usually large and long‐featured, whereas individuals of the other esterase phenotypes were smaller, with short features. The association of morphology and esterase phenotypes from laboratory experiments corresponded to the association observed in field samples. These results support the hypothesis that the cyclomorphosis of Lake Travis Bosmina involves a succession of clones as well as phenotypic plasticity.
A survey of the macro‐invertebrate riffle fauna of the rivers Ystwyth and Rheidol, Wales
Authors: BROOKER M. P. , MORRIS D. L.
Published: May 2006

SUMMARY.
A total of 155 taxa was collected from the Ystwyth (111) and Rheidol (134) catchments and total macro‐invertebrate densities ranged from 435 to 9105 m−2 and 155 to 4290 m−2 in the two catchments, respectively. The fauna in each catchment was dominated by Insecta, principally Plecoptera, Ephemeroptera and Diptera. Trichoptera and Oligochaeta were proportionally more abundant in the Rheidol catchment. There was no evidence that the distribution or relative abundance of the faunas of the catchments were related simply to heavy metal contamination (mean zinc concentration up to 2.0 mg I−1 and 0.34 mg I−1 in the Ystwyth and Rheidol, respectively). Average linkage clusters of Spearman rank correlation coefficients suggested that community affinities were probably related principally to location within the catchment. There was no evidence in the Rheidol catchment that irregular discharges (up to c. 15 m3 s−1) of water for hydroelectric purposes had any substantial effect on the invertebrate fauna although total invertebrate density below the discharge was significantly higher than at an upstream site.
Biochemical genetics and taxonomy in Plumatella coralloides and P. fungosa, and a key to the British and European Plumatellidae (Bryozoa: Phylactolaemata)
Authors: MUNDY S. P. , THORPE J. P.
Published: May 2006

SUMMARY.
Plumatella coralloides Allman 1850 has in the past been regarded as a synonym or variety of a number of species. Specimens conforming to Allman's (1850) original description have been found in a pond at Millwood, South Wales, and electrophoretic techniques have been used to examine genetic differences between this material, P. repens and P. fungosa. The results show that neither P. repens nor P. fungosa is conspecific with the Millwood material. Morphological evidence suggests that it should be regarded as P. coralloides, and it is therefore concluded that P. coralloides is a valid species. A revised key to the British and European Phylactolaemata (Bryozoa) is provided, together with some notes on the distribution of each species in Britain.
Diurnal fluctuations within a littoral plankton community in oligotrophic Lake Pääjärvi, southern Finland
Authors: KAIRESALO TIMO
Published: May 2006

SUMMARY.
The plankton community within an Equisetum fluviatile stand in oligotrophic Lake Pääjärvi had distinct diurnal fluctuations in the total cell volume and species composition of algae and in the abundance of microcrustaceans (Bosmina coregoni). Diurnal fluctuations in pH, oxygen saturation and temperature of the water were also recorded. Within the littoral region, daytime pH values > 9 were recorded, whereas in the pelagial region of the lake, values remained near pH 7. Diatoms and green algae dominated the littoral phytoplankton especially in the innermost parts of the macrophyte stand, with cryptophytes (dominant in the pelagial area) occurring only in small numbers. At the outer parts of the macrophyte stand, water movements between the pelagial and littoral areas might rapidly increase the contribution of cryptophytes in the phytoplankton. The fall in algal cell volume during the night may have resulted from settling out of cells in the absence of wind‐induced water movements, perhaps together with increased grazing pressure from dense swarms of Bosmina (up to 3000 individuals per litre) which appeared during the night.
The distribution of the crayfish, Austropotamobius pallipes, in British waters
Authors: JAY D. , HOLDICH D. M.
Published: May 2006

SUMMARY.
The distribution of Austropotamobius pallipes, the only freshwater crayfish indigenous to the British Isles, is examined using over 300 records collected since 1970. The majority of records are for England where crayfish are found in areas associated with base‐rich easily weathered substrata. Waters containing crayfish tend to be in the pH range 7–9, with calcium levels above 5 mg l−1. Crayfish are found in a wide variety of habitats ranging from deep water‐filled quarries with a soft substratum to shallow fast‐flowing streams.
Overwintering strategy of two closely related forms of Cloeon (dipterum?) (Ephemeroptera) from Sweden and England
Authors: NAGELL BJÖRN
Published: May 2006

SUMMARY.
Comparison is made of resistance to anoxia at 0°C of an English and a Swedish winter larval population of two closely related forms of Cloeon (dipterum?). The English population was not very resistant but contained a few slightly resistant larvae; the Swedish population was very resistant. Swedish larvae initiated hibernation more rapidly than English larvae and were also more resistant to starvation. The different properties of the populations are seen as an adaptation to different winter conditions in ponds in England and Sweden. Evidence is presented that low temperatures but not decreasing photoperiod are decisive for the final induction of hibernation in the larvae. In Swedish larvae this induction starts at between 4 and 5°C.
Major ion chemistry in a tropical African lake basin
Authors: GAUDET JOHN J. , MELACK JOHN M.
Published: May 2006

SUMMARY.
The amount of water lost by seepage from Lake Naivasha, calculated as the residual in the water budget, was 5 (1973), 11 (1974) and 20% (1975) of the total water loss. Direct measurements of seepage in nearshore shallows indicated that water entered the lake via ground‐water seepage in the northern portion and left the lake in the southern portion. Naivasha lies in a topographic closed basin but is hydrologically a seepage lake; it is distinctive among the lakes lying in the endorheic rift valleys of Ethiopia, Kenya and Tanzania because the water is fresh.

The mean chemical composition (mg l−1) of bulk precipitation collected on two transects across the rift valley near L. Naivasha and at three stations near Nairobi was: Na, 0.54, K, 0.31; Ca, 0.19; Mg, 0.23; SO4, 0.72 and Cl, 0.41. The major inflow, the Malewa River, was largely a solution of bicarbonate (1.15 m‐equiv, l−1), sodium (9 mg l−1) and calcium (8 mg l−1) and carried a total dissolved solid load (kg ha−1) of 62 (1973) and 120 (1974). Total dissolved solids, sodium, calcium and bicarbonate concentrations were inversely related to discharge.

Among the standing waters in the Naivasha basin, sodium and bicarbonate are predominant and the mean total dissolved solute content (mg l−1) increased from a low under the northern papyrus swamp (217) to intermediate values in L. Naivasha (329), the nearshore lagoons (367) and Crescent Island basin (394) to a high in Oloidien Lake (831). Ion ratios and stability field diagrams indicated that calcite is formed in the Crescent Island basin and Oloidien Lake. Calcite was detected in the sediments of the two basins. Ion ratios also indicated that sulphate was retained in the sediments of the northern papyrus swamp.

Several factors combine to keep L. Naivasha's water fresh. A large fraction of the water supplied to the lake comes from dilute rivers and rain. The lake does not lie in a closed basin, but loses water and solutes via seepage. Exchanges with sediments both in the pelagic and littoral regions of the lake are the major routes for solute movement and biochemical sedimentation is a major factor in removal of silica. Both geochemical and biochemical sedimentation account for much of the potassium, calcium, magnesium and bicarbonate removal. Only low levels of the conservative ions, sodium and chloride, are taken up by the sediments, while very low levels of sulphate and fluoride are actually released.
Comparison of three mapping procedures developed for river macrophytes
Authors: WRIGHT J. F. , HILEY P. D. , HAM STEPHANIE F. , BERRIE A. D.
Published: May 2006

SUMMARY.
Three methods of mapping macrophytes on short sections of river are described and compared. All methods involve setting up a 1‐m grid system over the site using permanent stakes to locate a series of temporary strings. The first method (detailed mapping), which generates a map, uses the grid system to locate accurately the position of macrophytes and substrata on the river bed. It is very time consuming and objectivity in mapping is difficult to achieve. The second method (points method) involves recording the macrophytes and substratum below each intersection of the 1‐m grid system covering the study site. This method is fast, capable of giving estimates of percentage cover for the different substrata and macrophytes but does not produce a map. The third method (rectangles method) is regarded as both the most efficient and also the most objective of the three mapping procedures. The substratum or macrophyte dominating each 50 × 100 cm rectangle of river bed is recorded together with additional substrata and macrophytes present. The procedure is rapid to use in the field, provides a simplified map of the study site and is more amenable to detailed analysis than the two previous methods. All three mapping methods are best suited to rivers less than 20 m wide where safe wading and good visibility can be guaranteed.
Effect of temperature on larval growth of Ecdyonurus dispar (Ephemeroptera: Heptageniidae) from two English lakes
Authors: HUMPESCH U. H.
Published: May 2006

SUMMARY.
Mature larvae of Ecdyonurus dispar were collected from Ennerdale Water and Windermere (English Lake District) and reared to adult males and females in the laboratory. The females were then fertilized artificially and their progeny were kept at constant temperatures (range 4.2–20.2°C). Larvae collected directly from the two lakes were also reared under the same conditions.

The maximum number of instars from egg to subimago was 25, the average body length increment (mm) per moult was proportionately constant at c. 15% and Dyar's rule was applicable. The interval between moults decreased with increasing temperature and the relationship between the two variables within the temperature range 4.2–19.8°C was described by a power law. Larval growth was exponential and variations in mean specific growth rate (range 0.23–5.23% length day−1) were related to mean temperature which was the major factor affecting growth in the laboratory. A few experiments were also performed in the lake to test the adequacy of the estimated values for larval growth at different temperatures in the laboratory. There was agreement between the estimates and the actual growth rates in the lake. Therefore, the regression equations obtained from the laboratory experiments are probably applicable to larval growth in the field.

Values for daily production in the laboratory ranged from 0.53 to 9.33 mg dry wt day−1 m−2. The lowest value was obtained at 8.9°C and the highest at 20°C.

Information on different life cycles of E. dispar is briefly reviewed and it is concluded that E. dispar from the lakes can only achieve one generation per year.
Number of flagellar segments and moulting in the amphipod Gammarus pulex
Authors: SUTCLIFFE D. W. , CARRICK T. R.
Published: May 2006

SUMMARY.
The number of flagellar segments on the antennules of Gammarus pulex was quantitatively related to body size in animals from natural populations and to moulting and instar number of isolated animals grown from birth in the laboratory. The number of segments was 5.0 at birth increasing to means of 19–20 in females and 21–22 in males at sexual maturity or c. 5 mg wet wt reached after nine or ten moults. Addition of segments to the paired flagellae of juveniles was not regular and the number of segments cannot be used to identify particular instars of individuals or to determine their age. The mean interval (days) between moults progressively increased in the later juvenile instars and was exponentially related to moult number, age and the number of flagellar segments; the moult interval is also exponentially related to these variables in adults.
A note on the watermite Hydrodroma despiciens feeding on chironomid egg masses
Authors: WILES P. R.
Published: May 2006

SUMMARY. Chironomid eggs are the primary food of aduh and nymphal Hydrodroma despiciens. Observations on feeding behaviour showed that the palps are well adapted for probing the egg mass jelly. Chironomid egg masses also serve as primary sites for male spermatophore deposition.
Photographic identification of individual grayling, Thymallus thymallus, based on the disposition of black dots and scales
Authors: PERSAT H.
Published: May 2006

SUMMARY. The flanks of grayling are generally studded with black dots which vary in number. The number and position of these dots are well‐defined for each individual and make it possible to identify each fish, in some cases, as when there are very few dots or none at all, it is necessary to make use of other features such as the general disposition of the scales.

The best method for recording these characters is by photographing each fish. When recaptured, a fish can be recognized by comparing photographs. The number and position of dots on their lines can be sorted by a computer. Ultimate confirmation is given by comparing the most likely photographs once they have been selected by the computer.
Colonizing macroinvertebrates in the Upper Mississippi River with a comparison of basket and multiplate samplers *
Authors: HALL THOMAS J.
Published: May 2006

SUMMARY. Colonizing aquatic macroinvertebrates were collected from two kinds of artificial substrate placed on wing dams in Pool 13 of the Upper Mississippi River in September 1978. Thirty‐one taxa were collected from basket samplers containing cement spheres and twenty‐one taxa from multiplate samplers constructed from tempered hardboard. Hydro‐psychidae (Trichoptera), especially Cheumatopsyche sp., Potamyla flava and Hydropsyche sp., were the dominant macroinvertebrates which colonized both samplers. Basket samplers had a significantly greater macroinvertebrate density, biomass and number of taxa compared with multiplate samplers. Precision of the arithmetic mean for density, biomass and number of taxa was 19.9, 18.3 and 8.1% for basket samplers and 18.8, 18.7 and 8.5% for multiplate samplers. The number of sampling units required for a precision of 20% for macroinvertebrate density, biomass and number of taxa was 13, 11 and 2 for basket samplers and 11, 11 and 2 for multiplate samplers. Basket samplers with 7.5‐cm cement spheres are recommended for use instead of multiplate samplers.
Seasonal dynamics of Chironomidae (Diptera) on the Bulrush Schoenoplectus lacustris in a chalk stream
Authors: DRAKE C. M.
Published: May 2006

SUMMARY. The chironomid fauna of a chalk stream in southern England is described from 1 year's catches of emerging adults and 2 year's quantitative samples of larvae on Common Clubrush, Schoertoplectus lacustris. The number of species in eaeh higher taxon as adult males and larvae on Schoenoplectus were: Tanypodinae, nine and three; Diamesinae, two for both; Orthoeladiinae, 26 for both; Chironomini. twelve and six; Tanytarsini, seven and five, respectively. A total of 66 species was recorded for both life stages. Adult Orthocladiinae were caught throughout the year. Tanytarsini were absent for a few weeks in winter, and Tanypodinae and Chironomini were caught for shorter periods in warmer months. Chironomids 93.5% of the total invertebrates on Schoenoplectus. Life histories are deseribed for seven speeies that formed 91% of the identified chironomids (32% of the total were unidentifiable first and second instar larvae). Four of these life histories appear for the first time. All seven species were multivoltine and had continuous recruitment for part of the year. The species diversity of larvae was mostly in the range 1.5–3.0 and it was determined more by equitability than by species richness. The numbers of chironomids through time were dependent on the weight of detritus on the leaves (r2= 0.69) and the availability of detritus therefore partly controlled their population size.
Reactions of singlet oxygen in humic waters
Authors: BAXTER R. M. , CAREY J. H.
Published: May 2006

SUMMARY. The oxidation of 2, 5‐diniethylfuran (DMF) to cis‐1, 2‐ diacetylethylene (DAE) is a specific test for singlet oxygen (1O2). A method has been developed for the measurement of DAB by direct injection gas chromatography. By the use of this method, the photochemical generation of 1O2 has been demonstrated in samples of two Canadian humic waters.

Two other photochemical reactions probably mediated by 1O2generation, the oxidation of histidine and the inactivation of a‐chymotrypsin, have been demonstrated in these waters.

The possible ecological and environmental implications of these findings are discussed.
Phosphorus and major cation mass balances for two rivers during low summer flows
Authors: HILL ALAN R.
Published: May 2006

SUMMARY. Soluble reactive phosphorus (SRP) mass balances showed that phosphorus retention occurred during low summer flows in reaches of Duffin Creek and the Nottawasaga River, two phosphorus‐rich streams in southern Ontario. The average daily removal in Duffin Creek was 6.1 ± 1.6 kg SRP which represents the retention of about 92% of the phosphorus input. Approximately 5.3 ± 3.5 kg SRP (about 44% of the daily input) was removed from stream water in the Nottawasaga River. Laboratory experiments indicate that sorption by stream‐bed sediments is an important mechanism for phosphorus retention in both rivers. Uptake by benthic algae may also act as a temporary phosphorus sink in Duffin Creek. Major cation inputs and outputs are generally in balance, implying that these elements act in a relatively conservative manner in both rivers.
The input of terrestrial invertebrates from tree canopies to a stream
Authors: MASON C. F. , MACDONALD S. M.
Published: May 2006

SUMMARY. The input of terrestrial invertebrates from different tree canopies to a trout stream was determined for a 28‐week period from April to October, 1980. Sycamore produced the greatest number of animals, followed by oak and alder. Ash was not significantly different from the controls. Coleoptera, Diptera, Homoptera and Arachnida made up the greatest number of animals caught, with Lepidoptera larvae important beneath oak. The input of biomass (g m‐2 dry wt) was also greatest beneath sycamore (35.80), followed by oak (27.76), alder (20.39), ash (11.15) and control (9.92). The input of biomass was bimodal. The significance of terrestrial invertebrates as food for salmonids is discussed.
Influence of dissolved humic materials on carbon assimilation and alkaline phosphatase activity in natural algal‐bacterial assemblages
Authors: STEWART ARTHUR J. , ROBERT G. , WETZEL W. K.
Published: May 2006

SUMMARY. Mixed natural assemblages of algae and bacteria exhibited lower rates of 14C assimilation and high rates of dissimilation of recent photosynthate when amended with low concentrations (7.2 mg 1‐1) of unfractioned dissolved humic materials (DHM). The extent of the inhibition or stimulation was greatest in the smaller (1–5 μm) assemblage particles. In different algal‐bacterial assemblages, additions of DHM markedly enhanced community alkaline phosphatase activity (APA), particularly under low light regimes, DHM of low apparent molecular weight was much more stimulatory to both 14C assimilation and APA than DHM of high apparent molecular weight, supporting the belief that DHM molecular weight is an important determinant of DHM interactive capacity. Higher concentrations of D HM (either unfractionated, or molecular weight fractionated) produced greater APA responses. Addition of phosphate enhanced the disparity in rates of 14C assimilation of samples incubated under low and high light regimes, increased the rates of 14C assimilation, and depressed APA. There were indications of interactions between DHM and phosphorus in several experiments. Two hypotheses were invoked to explain increases in APA in response to DHM: (1) increased competition between algae and bacteria for phosphate following bacterial release from substrate limitation, or (2) DHM may have acted as a sequestering agent for organophosphorus compounds, and in so doing, gradually depleted available phosphate. In either case, it is clear that DHM alters phosphorus cycling. This DHM characteristic may be ecologically as important as its ability to complex trace metals.
Some effects of light on algal respiration and the validity of the light and dark bottle technique for measuring primary productivity
Authors: YALLOP MARIAN L.
Published: May 2006

SUMMARY. Measurements of the rate of oxygen uptake in a number of blue‐green algae and diatoms were carried out under both field and laboratory conditions to determine the effects of light on such rates. The light history of algal cells was an important controlling factor of oxygen uptake. When measured in the light, with dichlorophenyl‐dimethylurea (DCMU), oxygen uptake was sometimes different from uptake measured in the dark. The results cast some doubt on the validity of the light and dark bottle method for determining primary productivity. It is suggested that oxygen uptake measurements should be made in the presence of DCMU.
The life history and production of Asellus aquaticus (Crustacea: Isopoda) in the River Ely, South Wales
Authors: MURPHY P. M. , LEARNER M. A.
Published: May 2006

SUMMARY. A population of the isopod Asellus aquaticus was studied for sixteen months in the organically polluted River Ely. South Wales. There were two complete generations each year. The overwintering population released young (the spring‐brood) over the period April‐June. These animals in turn produced their own offspring (summer‐brood) in late July‐October. Each generation died after breeding and the overwintering population was comprised entirely of animals from the summer‐brood.

Seasonal patterns of mortality were related to water flow, temperature and life‐cycle stage. Individual growth rates were affected by both temperature and life‐cycle stage.

Annual population production (P) was 195.68 g wet wt m‐2, mean annual biomass (B) was 32.98 g wet wt m‐2 and the annual P/B ratio was 5.93.
Extracellular release of photosynthetic products by freshwater phytoplankton populations, with special reference to the algal species involved
Authors: BLAAUBOER MARIANNE C. I. , VAN KEULEN R. , CAPPENBERG TH. E.
Published: May 2006

SUMMARY. Over three successive years, depth profiles of C‐fixation and excretion, chlorophyll‐a concentrations, phytoplankton species composition and bacterial numbers were determined in Lake Vechten, a slightly eutrophic lake in The Netherlands. Special attention was given to the method used to measure extracellular release.

Excretion of dissolved organic 14C depended largely upon the photo‐synthetic activity of the phytoplankton, ranging from 0–2.5 mg m‐1 h‐1, representing a percentage extracellular release (PER) of 0–25%.

During a period in August, however, a subsurface chlorophyll‐a maximum at 5–7 m depth coincided with high excretion rates of up to 10 mg Cm‐3 h‐1 (PER = 55%). Phytoplankton analysis revealed a stratification in numbers of Mallomonas caudata with a maximum at 5–7 m depth.

The results suggest that in these water layers bacterial populations grew at the expense of the dissolved organic carbon compounds excreted by Mallomonas caudata. This means that extracellular release can temporarily function as an important nutrient source for the heterotrophie community in addition to the more or less constant dissolved organic carbon pool.
The drift of some chironomid egg masses (Diptera: Chironomidae)
Authors: WILLIAMS C. J.
Published: May 2006

SUMMARY. The drift of chironomid egg masses was investigated in the River Mole (Devon) and the River Wye (Powys) in 1981. Large numbers of egg masses were found in the drift just after dusk; on one occasion an estimated 50,000 egg masses passed a sampling point in 5 h. Oviposition of free‐floating egg masses appeared to be initiated and synchronized by the onset of darkness. Egg masses of some Pentaneurini (Tanypodinae), Tanytarsini and Chironomini (Chironominae) were found in the drift and adhering to submerged stones.

Flotation by means of a gas vacuole within the egg mass was observed in the Polypedilum ‘convictum’ group. The gas vacuole decreased in size over 8–11 h and the egg masses sank after 2–3h.

Some chironomid egg masses are capable of drifting large distances after oviposition. The implications of sueh drift are briefly discussed in relation to the distribution of chironomid larvae.
Relationship of macrophyte‐mediated changes in the water column to periphyton composition and abundance
Authors: MORIN JOANNE O'NEILL , KIMBALL KENNETH D.
Published: May 2006

SUMMARY. 1. Dense growths of Myriophyllum heterophyllum influenced temperature, dissolved oxygen, pH and light levels in the littoral waters of Lake Winnipesaukee, a soft‐water. New England lake. Periphyton species composition and abundance (algal units cm' stem) were related to the macrophyte‐mediated changes in the physicochemical environment.

2. Duringearlysummer, M. heterophyllum occupied onlythe lower part of the water column. Limnetic and littoral waters exchanged readily and were chemically similar. Early summer periphyton species composition was dominated by diatoms from the phytoplankton, entangled in the finely dissected leaves of M. heterophyllum.

3. By mid‐summer, M. heterophyllum occupied the entire watercolumn of the littoral zone. The metabolic and photosynthetic activity and dense foliage of M. heterophyllum created marked vertical gradients in physicochemical conditions. Mid‐day temperature, dissolved oxygen, pH and light levels were maximal in the surface waters of the M. heterophyllum mat during the summer. Concurrently, periphyton species composition shifted to blue‐green and then to a filamentous green alga on the apex and mid‐stem. On the lower stem, diatoms consistently dominated the periphyton.

4. Periphyton abundance on the apex was inversely related to apical elongation. Temporal fluctuations of periphyton abundance on the lower and mid‐stem were small throughout the study. Periphyton abundance was lowest on the lower stem, where the deteriorating leaves provided less surface area for colonization.
Potentiometric measurements of carbon dioxide flux of submerged aquatic macrophytes in pH‐statted natural waters
Authors: DENNY PATRICK , ORR PHILIP T. , CSIRO DAVID J. C. ERSKINE
Published: May 2006

SUMMARY. 1, An apparatus has been described that is suitable for potentiometric measurement of carbon dioxide flux in photosynthesizing shoots of submerged aquatic macrophytes

2. The procedure, based on methods described by Tailing (1973) for measurement of phytoplankton photosynthesis, relies upon the continuous pH‐statting of the solution surrounding the tissues. The pH of the solution is monitored by electrodes from a pH meter which is linked to an auto‐titrator. The rise in pH during photosynthesis is then compensated tor by controlled, small titrant additions of CO2‐ennched solution (titrant water). This replaces the CO2 removed by the tissues without affecting the total alkalinity of the solution. If the concentration of CO2 in the titrant water, and the volume of titrant added arc known precisely, the CO2 flux can be calculated.

3. Total alkalinity, total CO2 and free‐CO2 acidity of the bathing solutions and titrant waters are estimated by Gran titrations and the pH: tilre‐volume data pairs are analysed by computer to provide rapid data feed‐back. A modification to Tailing's equation for calculation of F1functions has been necessary for accurate calibration of the CO2enriched tilrant water.

4. The photosynthesis cuvette, which is surrounded by a water‐jacket, is approximately I dm3 in capacity and has six compartments for the shoots. An impeller at the base of the cuvette rapidly mixes and cycles the bathing solution and flushes it over the tissues.

5. Information on temperature, light flux density, oxygen concentration. pH and titre‐volume is continuously recorded into a data‐logger and is fed into a computer which is programmed for data analyses.

6. Results from a typical experiment show the system to be sound and the method has considerable potential, especially in the study of aquatic plant photosynthesis in natural waters.
Reproduction and growth of Craterocephalus marjoriae and C. stercusmuscarum (Pisces: Atherinidae) in south‐eastern Queensland, Australia
Authors: MILTON D. A. , ARTHINGTON A. H.
Published: May 2006

SUMMARY. 1. The reproductive cycle and growth of Craterocephalus marjoriae and Craterocephalus stercusmuscarum (Atherinidae) were studied in Brisbane, south‐eastern Queensland, over a 17‐month period (1981–82).

2. Both species had a 5‐month breeding season in spring and summer, with a breeding peak in spring (September‐October). Multiple spawning occurred but life time fecundity was not determined.

3. Gonosomatic index values and mean fecundity per female were higher in Craterocephalus marjoriae than in C. stercusmuscarum. Fecundity increased with body length in both species according to the relationship, F=aLb. Growth rates were similar and growth was adequately described by the von Bertalanffy equation. Both species grew rapidly during the first year and reached maturity the following season. Reproductive strategies are considered in relation to seasonal flooding in the streams inhabited.
Anomalies in hydropsychid capture nets from polluted streams
Authors: PETERSEN LENA B.‐M. , PETERSEN ROBERT C.
Published: May 2006

Members of the genus Hydropsyche, net‐spinning caddisfly larvae, exhibit anomalies in the structure of their capture nets when collected from stream localities receiving heavy metal and toxic chemical wastes.

The number of nets showing anomalies was positively correlated with the number of anomalies per net suggesting a graded response to the toxic wastes.

Frequency of anomalies in a hydropsychid population increased the closer the nets were collected to a pollution source. Anomaly frequency was negatively correlated to total macroinvertebrate community structure as measured by the Shannon function. It is suggested that net anomaly frequeney by hydropsychids may be a useful tool in ecological monitoring.
Chironomid deformities as indicators of pollution from a synthetic, coal‐derived oil
Authors: CUSHMAN ROBERT M.
Published: May 2006

SUMMARY. Larval Chironomus decorus (Diptera: Chironomidae), taken from experimental ponds to which a coal liquid had been added, were found to have deformities of the mentum. Aberrations of the medial portion of the mentum were significantly dose‐related. Occurrence of such deformities appeared to be a less sensitive measure of pollution by the coal liquid than did previously reported changes in abundance, biomass, number of taxa, and species diversity of benthic insects.