bluuebunny/crossref_metadata_2025 huggingface dataset:
The peritrophic membrane and faecal pellets of Gammarus lacustris limnaeus Smith
Authors: LAUTENSCHLAGER K. P. , KAUSHIK N. K. , ROBINSON J. B.
Published: May 2006

SUMMARY.
Gammarus lacustris limnaeus Smith was fed decomposed autumnshed leaves of maple (Acer saccharum Marsh.) and poplar (Populus tremuloides Michx.). Faecal pellets were collected at various time intervals after egestion and examined under a light and a scanning electron microscope. Nearly all the faecal pellets collected up to a period of about 7 h after egestion possessed a thin, tightly‐fitting peritrophic membrane while those that had been outside the gut of the animal for a longer time lacked a peritrophic membrane. Presumably, after egestion faecal pellets swell because of absorption of water leading to eventual rupture and loss of the membrane. The surface of newly extruded pellets is devoid of microbes and microbes seem to play a very insignificant role in the loss of peritrophic membrane from the pellets.
On the early growth of 0+ perch, Perca fluviatilis, in Windermere
Authors: GUMA'A S. A.
Published: May 2006

SUMMARY.
The growth in length and weight (wet and dry) of 0+ perch Perca fluviatilis during their first summer of life in Windermere, has been investigated. Two major stanzas, occurring during and after metamorphosis, characterize the growth of 0+ perch in Windermere. The change from one stanza to another takes place between six and eight weeks after hatching. The exponential rate of growth in length was 0.26 and 0.27 mm mm−1 week−1 for the first stanzas of 1975 and 1976, respectively, and decreased to about 0.08 and 0.07 mm mm−1 week−1 for the second stanzas of the same years. Similarly, the growth in both wet and dry weights decreased from the first to the second stanza. Growth of 0+ perch was found to be logistic, and could not be described by the von Bertalanffy growth curve. The relationship between weight and length was allometric and the power values for length were, for wet weight: 4.154 (in 1975) and 4.033 (in 1976) for the first stanza and 2.400 (in 1975) and 2.734 (in 1976) for the second stanza; for dry weight: 3.988 (1975) and 3.971 (1976) for the first stanza and 3.066 (1975) and 2.651 (1976) for the second stanza. Half of the total growth was completed in 47% (1975) and 40% (1976) of the total growth period to the end of the summer.
Observations on the biology of the perch, Perca fluviatilis, in the River Stour, Dorset
Authors: MANN R. H. K.
Published: May 2006

SUMMARY.
Opercular bones from 323 perch from the River Stour were used for age and back‐calculated growth determinations. Annuli were formed during May at the beginning of the growth period. Growth was minimal from October to April. Female perch grew faster than males, and the growth rates of both sexes were higher than those observed in most other European waters. Spawning occurred during late April and early May; male gonads began development in August and had attained their maximum weight in September, but the ovaries developed gradually from August until April. Immature perch had an annual cycle of condition with a maximum in June‐July and a minimum in December‐January. The condition of mature males and females was affected by the gonad cycle. The fecundity of Stour perch is expressed by the formula: log egg number = 2.40 log length (mm) ‐ 1.34.

Approximately 25% of males were mature at age I and all were mature at age II, whereas most females did not spawn until age III. Ephemeroptera nymphs and minnow fry constituted the bulk of the diet of 0‐group perch; Ephemeroptera nymphs, minnow fry and Corixidae were the most numerous items in I group perch, whereas older perch contained Corixidae and a wider range of fish prey species, although minnows were the most numerous of these.
Aspects of the ecology of benthic fauna in Lake McIlwaine, Rhodesia
Authors: MARSHALL B. E.
Published: May 2006

SUMMARY.
An investigation into the ecology of benthic fauna in the eutrophic Lake McIlwaine (Rhodesia) was carried out in 1968–69. The profundal zone was only colonized in winter when the lake was isothermal and oxygen was present. The littoral zone was greatly affected by lake level fluctuation during the study period, and the population of lamellibranchs was destroyed by a drop in water level. While the water level was low, numbers of oligochaetes were high, but they declined as the water level rose. Chironomid larvae colonized the newly‐flooded land and their numbers increased considerably. The effects of eutrophication were less clear but it is suggested that the presence of Chironomus in the profundal in winter, and an increase in Limnodrilus hoffmeisteri, was linked with eutrophication.
Benthic macroinvertebrates of a fluctuating reservoir
Authors: KASTER J. L. , JACOBI G. Z.
Published: May 2006

SUMMARY.
Benthic macroinvertebrate distribution, abundance, and composition were observed in a fluctuating (7.7 m) central Wisconsin, U.S.A., reservoir during 1973–74. Chironomidae and Oligochaeta represented 98% of the total fauna by number. The chironomid, Chironomus plumosus, and an oligochaete, Limnodrilus, each averaged 36% of the total benthic biomass. Annual mean numbers and biomass in areas exposed to air, exposed to ice cover, or remaining inundated were 3025/m2 (1.8g/m2), 4311/m2 (4.5g/m2), and 8558/m2 (16.0 g/m2), respectively. A substantial portion of the benthic fauna was stranded and subsequently decreased rapidly in drying and frozen substrates exposed to air. Total benthic numbers and biomass were greatest immediately below the drawdown limit.

Recolonization required 3 months (mid‐March to mid‐June, 1974) to attain pre‐drawdown values for numbers and biomass, and subsequently both were greater after reinundation than before the substrate was exposed. Recolonization of areas exposed to the air was greater in substrates containing large amounts of organic matter than in sandy areas containing little organic matter. Sorting and transportation of sediments redistributed organic materials from the regulated zone to below the drawdown limit, and macrophytes were eliminated from the regulated zone. When compared to other reservoirs and lakes, the density of benthos in the Big Eau Pleine Reservoir is neither high nor low. However, when compared with non‐fluctuating reservoirs the number of Ephemeroptera, Plecoptera, Trichoptera, Amphipoda, and Gastropoda was low.
Caddis larvae (Trichoptera) as predators of fish eggs
Authors: FOX PETER J.
Published: May 2006

SUMMARY.
Eggs of bullhead (Cottus gobio) were found with damaged shells and with the contents removed. Experiments in laboratory aquaria indicated that the damage was caused by caddis larvae and that the type of caddis involved in egg predation might be identified by the nature of the shell damage.
Chemistry of sediments from two linked lakes in North Wales
Authors: GUPPY SUSAN F. , HAPPEY‐WOOD CHRISTINE M.
Published: May 2006

SUMMARY.
Cores of sediment from Llyn Peris and Llyn Padarn, two linked lakes in North Wales, are described. Dating of sediments by 14C techniques, investigations of remanent geomagnetism and estimates of recent deposition rates from measurements of 137Cs, indicate that in Padarn an unbroken record of the last 7000 years has been obtained. In Peris, the upper lake, the rate of sediment accumulation is greater than in Padarn and the sediment has been considerably disturbed. Sediment chemistry is related to the climatic and industrial history of the area. Some features of the chemical profiles in Padarn are similar to those of lakes in the English Lake District, and there is evidence to suggest that erosion has increased in the catchment since c. 3500 years ago. This is more recent than similar increases in erosion reported for the English Lake District. In Peris, industrial activity during the past few hundred years has resulted in high levels of copper and calcium in the surface regions of sediment profiles.
Horizontal distribution of the copepod Pseudodiaptomus hessei in subtropical Lake Sibaya
Authors: HART R. C.
Published: May 2006

SUMMARY.
The horizontal distribution of nauplii, CI‐CIII, CIV‐Cv and adult stages of the copepod Pseudodiaptomus hessei within the main basin of Lake Sibaya (27° 20′ S, 32° 37′ E) is described on the basis of semi‐synoptic cruises on 6 August 1971, 28 January 1972 and 11 February 1972. The distribution observed is considered in relation to variations in food availability and water temperature over this homothermal lake. It is concluded that these factors are not primarily responsible for observed patterns of distribution. Rather, wind‐induced currents appear to be of major significance in determining horizontal distribution. Stage‐related differences in the nature and extent of horizontal redistribution following severe wind are described. A consideration of the vertical distribution of groups of life‐history stages over a diel cycle in relation to the direction and relative strength of currents encountered by the copepods within their respective depth ranges provides an explanation for the differences in horizontal redistribution observed.
Limnological studies of Lake Wisdom, a large New Guinea caldera lake with a simple fauna
Authors: BALL E. , GLUCKSMAN J.
Published: May 2006

SUMMARY.
Lake Wisdom is of interest because it is large and deep, has oxygen throughout, and yet, apparently as a result of its recent formation, its biota has some surprising lacunae. It is nearly circular and fills the central caldera of Long Island, Papua New Guinea (5° 20′ S, 147° 6′ E). Its maximum length is 13.4 km, and area approximately 95 km2. A bathymetric map of the lake to depths of 300 m has been constructed from fathometer transects. Repeated soundings in the deeper parts gave depths of about 360 m. The surface of the lake is approximately 190 m above sea‐level and water samples from the deepest part of the lake are fresh, so the basin is apparently sealed. The lake level shows annual fluctuations of c. 1.0 m.

Limnological information has been collected during seven visits to Lake Wisdom over the period 1969–76. The surface temperature of the lake was constant at 28°C throughout this period and the temperature falls very gradually to 26–27°C at 60 m, except for a relatively rapid drop of approximately 1°C from 10 to 20 m. One of the most unusual features is the relatively high oxygen concentration in the deepest parts of the lake. Living chironomid larvae and molluscs were collected from the bottom in depths of 360 m. Light penetration in the lake varies greatly depending on the amount of rainfall and the volcanic activity of Motmot, a secondary cone within the lake.

The biota of Lake Wisdom is rather simple. There is a low standing crop of phytoplankton. Benthic algae are abundant and diverse although they cover only a limited area because of the depth of the lake. There are no vascular aquatic plants. The pelagic fauna consists of two species of Cladocera and one species of notonectid. There is one species of sponge, four species of molluscs, and a small number of species of aquatic insects including Hemiptera. Odonata, and the larvae of chironomids, mayflies, a caddisfly, and a pyralid moth. Water birds, including ducks, grebes and waders, are fairly numerous. The lake also contains one or more crocodiles.
The energy balance of the Australian brine shrimp, Parartemia zietziana (Crustacea : Anostraca)
Authors: MARCHANT R.
Published: May 2006

SUMMARY.
Assimilation budgets (i.e. assimilation = respiration + excretion + production) are presented for cohorts of P. zietziana in two salt lakes. Shrimps in Pink Lake had an assimilation rate of 1631.6 kJ m−2 year −1, those in Lake Cundare 212.1 kJ m−2 year−1. In both lakes, respiration accounted for 60–80% of assimilation. Assimilation rates for individuals (derived as assimilation = ingestion minus faecal output) are also given and compared with respiratory rates of individuals. The comparisons indicated that energy was often consumed at a higher rate by respiration than it could be supplied by assimilation. Starvation due to a low assimilation efficiency was suggested as a cause of the consistent mortality, variable growth rate of individuals and unpredictable recruitment which were characteristic of the cohorts of P. zietziana in both lakes. An analysis of mortality showed that the young had the poorest survival, as predicted by a theoretical model of a starving zooplankter and a comparison of the increase with weight of ingestion and respiration. Gross growth efficiency (production: assimilation) was 15–30%, about the same as published data on Anostracans. Net growth efficiency (production : consumption) was 5–12% and generally lower than published values reflecting the difficulty P. zietziana has in balancing its budget.
Feeding and growth of Asellus aquaticus (Isopoda) on food items from the littoral of Windermere, including green leaves of Elodea canadensis
Authors: MARCUS J. H. , SUTCLIFFE D. W. , WILLOUGHBY L. G.
Published: May 2006

SUMMARY.
In the laboratory, Asellus aquaticus devoured intact green leaves from growing shoots of the aquatic macrophyte Elodea canadensis. In four collections of A. aquaticus on Elodea in a lake (Windermere), c. 20% of the specimens contained in their guts fragments of green Elodea leaves; this material and pieces of oak (Quercus) were identified from characteristic leaf hairs. Some specimens had also eaten the filamentous alga Oedogonium. Fluorescence microscopy is a useful aid for screening invertebrates that may have eaten living plant tissues.

Immature A. aquaticus, with an initial mean body length of c. 3 mm, wet weight c. 1 mg, were grown through sexual maturity over a 49‐day period at 15°C in a series of twenty‐two experiments (six to twelve isolated specimens in each experiment) comparing growth rates on different foods, including instances where no food was given. Animals were fed on a variety of items collected from the littoral of Windermere, plus some laboratory cultures of algae and bacteria. The highest mean specific growth rate (5.8% day−1) was obtained on young Elodea leaves mechanically shaken to remove epiphytes. Other diets yielding fast growth rates (3.7–5.3% day−1) were young growing leaves of Elodea with few epiphytes and older green and brown living leaves covered with a thick growth of epiphytic algae, epiphytic algae removed from Elodea, plastic imitation Elodea immersed in the lake until covered with attached algae, epilithic algae on stones, Oedogonium, and decaying oak leaves. Slower growth (1.3–2.2% day−1) and poorer survival was obtained on the following: a pure culture of the bacterium Sphaerotilus natans; cultured bacteria from lakewater; the filamentous algae Cladophora and Stigeoclonium both with and without epiphytes; faecal matter from Asellus; freshly killed Asellus; lake sediment. Some growth (mean = 0.7% day−1) and 50% survival for 21 days occurred in ‘starved’ animals kept in filtered, sterilized lakewater. Better survival and slightly faster growth (1.0–1.5% day−1) occurred in ‘starved’ animals kept in filtered and unfiltered lakewater.

Growth of A. aquaticus was also experimentally determined from birth in animals fed on young green Elodea leaves and on decaying oak leaves. On both diets, growth was curvilinear and approximately exponential from birth to sexual maturity reached at c. 2mg wet weight in 46–60 days at 15°C. In older specimens the relative growth rate gradually fell over a period of 50 days, representing a more linear phase of growth during sexual maturity.
A simple water and plankton sampler
Authors: BLAKAR INGGARD ARNE
Published: May 2006

SUMMARY.
A lightweight, free‐flushing water and plankton sampler constructed of readily available, inexpensive material is described. Easily interchangeable tubes of varying volumes allow sampling flexibility. The sampler is activated by a messenger and is shut by two plastic funnels. For analyses in highly stratified waters, the sampler can be adjusted into the horizontal position. Several samplers may be tripped in series. The sampler has proved a versatile and reliable instrument in ecological studies.

The tripping mechanism may also be used to release reversing thermometers and closing nets.
Vertical and seasonal variation of phytoplankton photosynthesis in a brown‐water lake with winter ice cover
Authors: JONES ROGER I. , ILMAVIRTA VEIJO
Published: May 2006

SUMMARY.
Unlike previously studied lakes with prolonged winter ice and snow cover, Lake Paajarvi, southern Finland, has a high humus content and consequently differs in both the quantity and quality of light penetration into its waters. Moreover, the range of temperature fluctuation and the degree of development of thermal stratification are greater in Paajarvi, and this increased environmental heterogeneity apparently stimulates diversity in the phytoplankton community, especially in the seasonal succession of species. Differences in the photosynthetic capacity of algae from different depths in the water column were not great. This is attributed to the extremely shallow euphotic zone, algae circulating freely through the steep light gradient and sedimenting rapidly once they pass through the thermocline into the hypolimnion. It is suggested that ‘adaptation’ of phytoplankton to the great seasonal changes in irradiance is achieved largely by successive growths of different species in the community, and that the adaptations and vertical migrations by individual algal species, which have been reported from polar and high alpine lakes, may be of secondary importance in Pääjärvi. The species successions in Pääjärvi produce changes in the pigment content of algae similar to those reported from polar and high alpine lakes, confirming that change in pigmentation is an important mechanism in light adaptation, whether at community or individual level. Algal pigment content was particularly high at the end of the long period of winter ice cover, indicating a degree of adaptation to the prolonged low‐light conditions, which produced the extremely high photosynthetic capacities measured at this time. However, phytoplankton production at any irradiance was primarily determined by biomass.
Growth and population studies on Tilapia galilaea in Lake Kinneret
Authors: LANDAU RUTH
Published: May 2006

SUMMARY.
Between 1967 and 1977, catches of Tilapia galilaea in Lake Kinneret fell from an annual average of about 200 tonnes to a low of 70 tonnes in 1974, and then returned to their former level. Total yearly mortality (Z) was estimated at 1.84 between 1970 and 1976. Assuming a natural mortality (M) of 0.94, total stock size averaged 300–700 tonnes in that period, while recruitment averaged < 0.7–3 million per year. Three broods hatched in years of relatively high water levels (1970, 1971 and 1972) yielded especially low recruitment.

The Von Bertalanffy growth coefficient (K) was estimated at 0.67, and final length (L∞) at 25–36cm total length. First year's growth, 23–152mm, was closely related to final length, which appeared to be affected by genetic variation in the population. Yearly fluctuations in size distribution were attributed to changes in the proportions of fast‐ and slow‐growers, as well as in the abundance of year‐classes. Recruitment to the fishery, at 17–20cm, occurred between ages l+and3+.

The highest growth rates for age‐1 T, galilaea, 1–2% mean weight per day, occurred in April and May, the Peridinium season. However, only a small proportion of age‐1 fish reached marketable size by July, when their food supply began to diminish. During the autumn months, there was hardly any length increment, and all T. galilaea became lean, especially the age‐0 group. It is surmised that recruitment of stocked fish could be increased by introduction in December and by use of fingerlings which are potentially able to grow to marketable size in less than two seasons.
Temporal variation in benthic ciliates and the application of association analysis
Authors: FINLAY B. , BANNISTER P. , STEWART J.
Published: May 2006

SUMMARY.
A 2‐year sampling programme of three benthic sites in a small eutrophic loch revealed large communities of ciliated protozoa consisting of a wide diversity of species (91 spp. over the 2 years). Species‐groups described with the aid of association analysis (normal and inverse) indicated the existence of a ‘ubiquitous’ species‐group consisting of at least Cyclidium glaucoma and Aspidisca costata. Another species‐group containing large ciliates (Loxodes striatus, Frontonia leucas, Spirostomum spp. and Paramecium spp.) was characteristic of the summer months at all sites. It is advocated that association analysis might increase the value of protozoa as pollution indicators.
The effects of temperature and different food organisms on the rate of gastric evacuation in perch (Perca fluviatilis)
Authors: PERSSON LENNART
Published: May 2006

SUMMARY.
The rate of gastric evacuation in perch Perca fluviatilis was studied at different mean temperatures (range 4.0–21.7°C). Gastric evacuation rates were empirically described by an exponential function and the relationship between the instantaneous evacuation rate (R) and temperature was also exponential. Evacuation rates were not significantly different (P > 0.1) for the following food organisms: Gammarus pulex, Chaoborus, chironomids and zooplankton. The effects of temperature, different food organisms and fish size on the evacuation rates in different fish species are discussed.
Diel emergence patterns of lotic Chironomidae
Authors: WARTINBEE DAVID C.
Published: May 2006

SUMMARY.
Six channels were constructed in various parts of two riffles from which chironomid exuviae were collected every 3 h for three 24‐h periods in July 1974. Diel emergence patterns were calculated for twelve abundant species and six different patterns were observed.

Krenosmittia cf. camptopheleps and Cordites had their major emergence pulse during peak light periods and it is proposed that high or increasing light intensity is a cue for their emergence. Stempellinella cf. brevis begins its emergence in the morning and continues until after darkness. Increasing and high water temperatures are suggested as the emergence cue since emergence tracks water temperatures with little apparent effect of light. Parametriocnemus sp. and Polypedilum (Tripodura) sp. begin emerging in late evening and continue into early daylight hours. These patterns indicate low and decreasing water temperatures as the emergence cue with little apparent effect of light. Corynoneura sp. and Thienemanniella sp. emerged primarily during daylight hours with a minor pulse in the morning and the major pulse in late afternoon. It is proposed that the emergence cue is simply the presence of light and that water temperature determines how many individuals are able to prepare for emergence and respond to the cue. Rheotanytarsus cf. exiguus and Tanytarsus (Sublettea) coffmani have major emergence peaks just after sunset and minor pulses in the morning hours. Changes in light are proposed as their emergence cue with water temperatures determining the number of individuals able to respond to that cue. Eukiefferiella discoforipes gr. sp. and Nilotanypus sp. emerge continuously throughout daylight and darkness hours, showing no obvious pattern.
The emergence of midges (Diptera: Chironomidae) from a wet gravel‐pit
Authors: TITMUS GRAHAM
Published: May 2006

SUMMARY.
Emerging adult chironomids were captured from a wet gravel‐pit in the Midlands in 1975 and 1976. The emergence period in 1976 was earlier than in 1975 and this change was attributed to the higher temperatures during the early part of 1976. Forty‐seven species were identified of which twenty‐one were found in both years. However, only eighteen species represented more than 5% of the monthly emergence from any one trap. The timing and location of emergence of the common species is discussed in relation to the physical parameters of substratum, depth of water and vegetation at each trap site. Similarity indices were used to compare samples from each trap site and revealed a progressive change in the chironomid assemblage with depth, caused by a succession of species and a change in the structure of the assemblage with ‘equitability’ decreasing with increasing depth. The predominant species in 1975 were Cricotopus sylvestris, C. intersectus and Procladius choreus with a number of Chironominae present in both May and June. A trap in the littoral zone caught maximum numbers earlier than traps in open water. In 1976 the above species were still predominant and Tanypus punctipennis and T. vilipennis were also numerous. The Chironominae became proportionally more abundant as the season progressed. The abundance of emerging midges was low compared with other surveys due to the restricted emergence period, imagines being abundant only in June, and also due to the low numbers emerging.
A comparison of the gut contents of two co‐existing lake‐dwelling Naididae (Oligochaeta), Nais pseudobtusa and Chaetogaster diastrophus
Authors: McELHONE M. J.
Published: May 2006

SUMMARY.
The gut contents of Nais pseudobtusa and Chaetogaster diastrophus, two co‐existing littoral‐dwelling Naididae (Oligochaeta), differed over a period of one and a half years due to strong selection by C. diastrophus for specific diatom genera, Cymbella spp. and Navicula spp. In contrast, N. pseudobtusa showed less selection and the gut contents consisted mainly of detritus, diatoms and mineral particles. These differences in the food niche are likely to contribute to the co‐existence of the two species in this habitat.

Seasonal changes in the relative abundance of diatom genera in the habitat greatly influenced the gut contents of N. pseudobtusa; however, these changes had less influence on those of C. diastrophus. This and the highly selective nature of the gut contents of C. diastrophus suggests that the two species have different feeding strategies. It is suggested that C. diastrophus actively seeks out certain diatom genera in preference to other food items, while the unseslective gut contents of N. pseudobtusa are more typical of an opportunist feeder.
Nutrient budgets and the regulation of nutrient concentrations in a small sub‐arctic lake in northern Sweden
Authors: JANSSON MATS
Published: May 2006

SUMMARY.
A 5‐year study was made of the hydrology and water chemistry in the watershed of Lake Stugsjön, a small lake in the sub‐arctic region of northern Sweden. Of the total yearly runoff, 80% occurs during the spring thaw in May and June and largely regulates the nutrient loading. The ice‐free period of the lake is June—October. Atmospheric deposition of nitrogen and phosphorus was among the lowest recorded anywhere, in spite of which it accounts for approximately half of the total summer nutrient loading. Dry fall‐out made up the major part of the total atmospheric deposition of nitrogen and phosphorus during the summer.

Conductivity measurements showed that the major constituents were not influenced by processes within the lake.

The nitrogen concentration in the lake during the summer was probably regulated by benthic algae which assimilated inorganic nitrogen from the sediments and released organic nitrogen to the lake water.

Phosphorus loading and water temperature in combination showed a clear relationship with the mean concentration of chlorophyll‐α during the ice‐free period.
Estimation of the growth rates of epiphytic bacteria and Lemna minor in a river
Authors: HOSSELLand JUDITH C. , BAKER J. H.
Published: May 2006

SUMMARY.
Growth of Lemna minor fronds in the River Frome during summer was found to be logarithmic with time and the growth rate (log10) was 0.066 day−1. This is equivalent to a doubling time of 4.5 days. The life expectancy of the fronds was 34 days.

The net change in the density of bacteria epiphytic on the lower surface of Lemna fronds in the R. Frome was monitored using a direct microscopic technique. The observed increase in bacterial numbers has been partitioned into the components of attachment and growth, assuming that attachment occurred at a constant rate and that the bacterial population grew logarithmically. The line which fitted the data best gave an attachment rate of 5.7 × 105 bacteria cm−2 day−1 and a growth rate (log10) for the bacteria of 0.044 day−1 which is equivalent to a doubling time of 164 h.

Estimates of the rate of detachment of bacteria from Lemna plants were obtained from a laboratory experiment which assumed negligible growth of bacteria in 1 h. The number of bacteria which detached per hour and the sizes of the bacterial populations on the plants before and after detachment were estimated using a plating technique. Different detachment rates were monitored. The detachment rate (analogous to growth rate) which is judged to be most similar to an in situ value was 0.0031 h−1 (0.074 day−1). This rate added to the specific growth rate given above resulted in a corrected growth rate of 0.118 day−1 equivalent to a doubling time of 61 h.
Tests to confirm quantitative sampling of young fish by the Bagenal buoyant net
Authors: HEWITT D. P.
Published: May 2006

SUMMARY.
Buoyant nets had been developed and used for several years to sample young fish quantitatively. Tests were carried out to verify the quantitative aspect of sampling. Using nets of 1‐m and 0.5‐m mouth diameter, over several months, the catches of the two net sizes were compared. There was no significant difference in the lengths of the fish caught in the two sizes of net nor in the population estimates derived from their catches. These results indicate that there is no avoidance of the nets and that they can be considered to sample quantitatively.
Feeding and growth of the isopod Asellus aquaticus on actinomycetes, considered as model filamentous bacteria
Authors: WILLOUGHBY L. G. , MARCUS J. H.
Published: May 2006

SUMMARY.
Asellus aquaticus was fed for 49 days at 15°C on aquatic actinomycetes in the laboratory. Specific growth rates (wet weight) of animals initially 2.5mm in length ranged from 0.85 to 2.33% day−1 on Micromonospora and Streptomyces S2 respectively. Asellus newly released from the brood‐pouch (1.0 mm length) had a similar growth rate (2.74% day−1) on Streptomyces S2. The growth rates of animals fed on actinomycetes were lower than those of animals feeding on macroscopic foods such as Elodea and decaying oak leaves, regardless of the initial size of the animal. However, it was concluded that actinomycetes, and by inference bacteria also, could maintain a population, albeit a slow‐growing one, in a situation where macroscopic foods are largely absent.

The possible significance of hyphal diameter of micro‐organisms in relation to assimilation from them is discussed. In this connection actinomycetes are considered as model filamentous bacteria.
Life cycles and growth rates of Baetis spp. (Ephemeroptera: Baetidae) in the laboratory and in two stony streams in Austria
Authors: HUMPESCH U. H.
Published: May 2006

SUMMARY.
Larvae of Baetis alpinus, B. lutheri and B. rhodani were reared in a stream channel (water temperature range 4.2–11.4°C) in the laboratory. The larval growth was exponential and the mean specific growth rate varied from 1.93 to 2.24% day−1 for B. alpinus, 1.49 to 3.41% day−1 for B. lutheri and 0.79 to 3.11% day−1 for B. rhodani. These variations in growth rate were related to variations in mean temperature and this was the major factor affecting growth in the laboratory.

Non‐quantitative samples of the benthos in the Seebach and Unterseebach, two stony streams near Lunz, Austria, were taken at approximately monthly intervals from November 1965 to May 1968. In each year, there were two winter and three summer cohorts for B. alpinus from Seebach and two or three winter and one to three summer cohorts for B. lutheri and B. rhodani from Unterseebach. Over the study period of 30 months, eleven cohorts were recorded for B. alpinus and B. lutheri, and ten cohorts for B. rhodani. The life cycle of a cohort varied from 3 to 8 months in B. alpinus, from 2.5 to 9 months in B. lutheri and from 2.5 to 8 months in B. rhodani. Mean specific growth rate in length varied from 0.82 to 2.97% day−1 for B. alpinus, 0.96 to 3.33% day−1 for B. lutheri and 0.65 to 3.01% day−1 for B. rhodani. The percentage of the variability in growth rate accounted for by variations in mean temperature was 63% for B. alpinus, 91% for B. lutheri and 82% for B. rhodani. Therefore mean temperature was clearly the major factor affecting the growth rates in the field.

An agreement was found between the growth rates of B. alpinus in the field and the laboratory. The growth rates of B. lutheri and B. rhodani were slower in the field than in the laboratory at higher temperatures. The possible reasons for this latter discrepancy are discussed, and the growth rates of the three Baetis spp. are compared with those of other species of Ephemeroptera.
Annual productivity and phytoplankton changes between 1969 and 1974 in Gull Lake, Michigan
Authors: MOSS B. , WETZEL R. , LAUFF G. H.
Published: May 2006

SUMMARY.
The seasonal and depth distributions of dominant phytoplankters, in situ primary productivity, organic carbon, and major chemical variables are described for Gull Lake, Michigan for the years 1971–74. Despite efforts by residents surrounding this moderately large dimictic lake to reduce phosphorus loading, all indications are of progressive eutrophication over the period. Previously dominant Cyclotella michiganiana has almost completely disappeared while araphidinean diatoms have increased greatly; certain blue‐green algae that were absent previously are becoming characteristic. The ratio of araphidinean to centric diatoms in recent sediments has also increased. Primary productivity and particulate and dissolved organic carbon concentrations have also increased. Voluntary attempts to reduce nutrient loading have apparently been inadequate to arrest increasing rates of eutrophication.
The effects of coal industry pollutants on the macroinvertebrate fauna of a small river in the South Wales coalfield
Authors: SCULLION J. , EDWARDS R.W.
Published: May 2006

SUMMARY.
The effects of pollutants from the coal industry on the macroinvertebrate fauna of a small river in the South Wales coalfield were investigated during 1972 and 1973.

Three major types of pollution, each spatially separate, affected the river and its tributaries. The upper reaches received acidic drainage from coal stockpiles. The lower reaches received a discharge from a drift mine, bearing high loads of suspended coal particles which caused siltation of the river bed downstream to its confluence with the R. Taff (3.5 km). The largest tributary was subjected, under neutral pH, to siltation by ferric hydroxide, derived from seepage from an abandoned mine.

In the upper reaches, a few acid‐tolerant invertebrate species survived in low numbers. Downstream recovery was not complete before the discharge of coal particles. In the reaches silted by ferric hydroxide or coal there was a pronounced reduction (80–90%) in faunal abundance. Clear differences in sensitivity of invertebrate groups to these types of siltation were apparent.

The data are used to assess the various methods of biological surveillance involving invertebrates.
Ultra‐trace analysis of soluble zinc, cadmium, copper and lead in Windermere lake water using anodic stripping voltammetry and atomic absorption spectroscopy
Authors: DAVISON W.
Published: May 2006

SUMMARY.
The concentrations of trace metals in filtered and unfiltered lake water were measured using anodic stripping voltammetry, before and after digestion by ultra‐violet irradiation, and by atomic absorption spectroscopy with electrothermal atomization. Total soluble components were estimated to be: zinc, 2.1 μg 1−1; cadmium, <0.05 μg l−1; lead, <(0.1 μg l−1 and copper, 0.3 μg 1−1. Atomic absorption spectrophotometric results and u.v.‐digested, anodic stripping voltammetric results were in good agreement. All measurable zinc was electrochemically labile whereas copper above the detection limit of 0.09 μg l−1 was electrochemically inert.
Effect of temperature in laboratory studies on development and growth of Cladocera and Copepoda from Tjeukemeer, The Netherlands
Authors: VIJVERBERG J.
Published: May 2006

SUMMARY.The effects of temperature on development and growth are described for the common Cladocera and Copepoda in Tjeukemeer. Eight cladoceran species and five copepod species have been investigated:Daphnia hyalina, Daphnia cucullata, Bosmina coregoni, Bosmina longirostris, Chydorus sphaericus, Ceriodaphnia pulchella, Diaphanosoma brachyurum, Leptodora kindtii, Acanthocyclops robustus, Mesocydops leuckarti, Diacyclops bicuspidatus, Cyclops vicinus vicinusandEurytemora affinis. Growth is expressed as length increment per size class (cladocerans) or instar (copepods) per week and as the relationship between time and length. The curvilinear logarithmic equation: In D = In a + b (In T)2is fitted to the development times of eggs, combined naupliar instars and combined copepodite instars, as well as to the longevity of the adults. The results are compared with those found in the literature and differences are discussed.
The effect of sewage effluent on denitrification in Grasmere (English Lake District)
Authors: JONES J. GWYNFRYN , DOWNES MALCOLM T. , TALLING IDA B.
Published: May 2006

SUMMARY.
Denitrification processes in Grasmere were studied using several techniques. Sediments were analysed for nitrate reductase activity and the accumulation of nitrogenous gases in samples incubated in the laboratory. Changes in the concentrations of inorganic nitrogen species in the water column and the release of gas bubbles into gas traps suspended above the sediment were also measured. Sewage effluent entered the lake via the main inflow and faecal bacteria were used as tracers to map the path of the river (and effluent) across the lake. The main river flow was west of the island in the centre of the lake and across the smaller of the two main basins. A preliminary study indicated that this western basin was the site of most active denitrification and this was confirmed in the following year when a seasonal survey showed that deoxygenation, nitrate reduction and ammonium accumulation was more advanced at this site. In addition, this basin was the only area where consistent discharge of nitrogen and methane from the profundal zone was observed. The nitrate reductase assay demonstrated that the sediment was the major site of denitrification, and that activity in the water column was higher in the anoxic hypolimnion than in the euphotic zone. Gas evolution from incubated sediment samples was analysed by gas liquid chromatography (GLC) and indicated that maximum denitrifying activity occurred below the mud surface in oxidized sediments. There was reasonable agreement between the enzyme assay and the GLC technique but neither predicted events in the field satisfactorily. Viable, most probable number (MPN) counts of denitrifying bacteria had similar limitations. A bimodal seasonal pattern of nitrate reductase activity was observed at four sites during thermal stratification, but this could not be explained fully. The major site of denitrification was identified and it was calculated that the nitrogen gas discharged was equivalent to c. 54% of the nitrate removed from the water column.
Biochemical genetics and taxonomy in Plumatella emarginata and P. repens (Bryozoa: Phylactolaemata)
Authors: THORPE J. P. , MUNDY S. P.
Published: May 2006

SUMMARY.
Although morphological distinctions are well documented, many authors have regarded the freshwater bryozoan Plumatella emarginata as a variety of P. repens. Differences between the two nominate species have been studied by the electrophoretic examination of genetic variation at enzyme loci. Genetic identity (Nei, 1972) was 0.286, a value well below that expected for conspecific allopatric populations. The results leave little doubt that specimens of the two species are from quite distinct and separate gene pools, with an unexpectedly high level of genetic differentiation. It is therefore concluded that P. emarginata is a valid species and is not merely a variety of P. repens. Morphological differences between the two species are also discussed.
The larva of Tinodes maculicornis (Trichoptera: Psychomyiidae), with notes on the species' distribution and habitat in Ireland
Authors: O'CONNOR J. P. , WISE E. J.
Published: May 2006

SUMMARY.
A key is given for the identification of the larva of Tinodes maculicornis which is the only undescribed psychomyiid in the British Isles. The Irish distribution and habitat of the species are outlined.
The temperature‐determined growing season of a submerged hydrophyte
Authors: MOELLER ROBERT E.
Published: May 2006

SUMMARY.
Temperature determines the growing season of Utricularia purpurea, a common rootless, carnivorous plant at depths of 0–6.5 m in a dimictic oligotrophic lake (Mirror Lake, New Hampshire, U.S.A.). The dynamics of thermal stratification limit the growing season to 8 weeks at a depth of 6 m compared to 17 weeks at 2 m. Light may limit growth at 6 m during the short growing season, but is not limiting in midsummer at 2 m or 4 m. Plants of equivalent size produce 60–75% less biomass annually at 6 m than at 2 or 4 m. The seasonally maximal biomass (in mid‐August) is equivalent to the annual net production as calculated from periodic inventories of new, old and senescent tissue (thus P/B= 1.0). Uptake of nutrient elements (N, P, Ca, Mg, Na, K) is synchronous with biomass production. Nutrients do not become enriched in the overwintering tissue (52% of the maximum biomass). This species is unusually rich in Zn (1000 μg g dry wt−1), relatively rich in N (2.9% dry wt). but quite poor in P (0.084%).
Growth in the crayfish Austropotamobius pallipes (Crustacea: Astacidae)
Authors: PRATTEN D. J.
Published: May 2006

SUMMARY.
The growth of Austropotamobius pallipes was studied in the River Ouse during 1976–78. Growth of mature crayfish (>2.5 cm carapace length) was followed by determining the relationship between the growth increment at moult and premoult carapace length, together with the frequency of moulting of different categories of crayfish. These data are supplemented by the recapture of marked individuals and the measurement of crayfish held in corves in the river. Growth was limited to the period May–October when water temperatures exceeded 10°C. Growth rates of male and female crayfish are similar until maturity is reached, thereafter males moult twice per year and the majority of females moult once. No crayfish in excess of 3.7 cm carapace length has been observed to moult more than once per year. Growth of juveniles (<2.5 cm carapace length) was estimated from size frequency distributions constructed from regularly taken samples. Growth rates of juveniles showed great variation both between and within year classes. In the hot dry summer of 1976, juveniles exhibited faster growth rates (instantaneous growth rates (G) for 0+ and 1 + crayfish were 0.029 and 0.013 mg mg−1 day−1. respectively) than in other years. Laboratory experiments on the effect of temperature on the growth rate of 0 + crayfish were undertaken; for crayfish at 15°C. G= 0.0138 (0–53 days) and at 10°C, G= 0.0003 (0–90 days). Crayfish held at 10°C failed to undergo a single successful moult. At 20°C crayfish exhibited exponential growth over the first 40 days, with G= 0.0189. declining thereafter to G= 0.012 (40–90 days).
A survey of the macro‐invertebrate riffle fauna of the River Wye
Authors: BROOKER M. P. , MORRIS D. L.
Published: May 2006

SUMMARY.
Surveys of the Wye catchment in March and September 1975, and July and September 1976 and 1977, yielded 227 macro‐invertebrate taxa, 77 of which were Chironomidae. Total macro‐invertebrate density ranged from 520 to 22020 m−2. Total density estimates in July 1976. during a period of severe drought, were significantly higher than in July 1977 but no differences were established between estimates on other comparable dates in 1975, 1976 and 1977. The total number of taxa and total macro‐invertebrates collected from sites with total dissolved solids concentrations less than 50 mg I−1 were significantly lower than at sites with higher concentrations. In general, upstream sites were dominated numerically by Plecoptera in March; Ephemeroptera, Trichoptera and Diptera were relatively more abundant during the summer months. Sites lower in the catchment were more variable in composition with Oligochaeta, Ephemeroptera, Trichoptera and Diptera all abundant at certain sites and times. The densities of Ecdyonuridae (Ephemeroptera). Hydropsychidae (Trichoptera) and Elminthidae (Coleoptera) in the impounded R. Elan, a tributary of the R. Wye, were significantly lower than at nearby sites on the Wye although no differences in total macro‐invertebrate density were established. Average linkage clustering of Spearman rank correlation coefficients between selected taxa allowed the comparison of taxa groups with contemporary site groups by nodal analysis. Six major taxa groups were established and these characterized five site groupings.
Abnormalities in the tracheal gills of aquatic insects collected from streams receiving chlorinated or crude oil wastes
Authors: SIMPSON KARL W.
Published: May 2006

SUMMARY.
Altered tracheal gills were found on some specimens of Phasganophora capitata (Plecoptera: Perlidae) and net‐spinning caddisflies (Trichoptera: Hydropsychidae) collected from streams in New York State. At one location only the basal portion remained of the normally highly‐branched structures. At another location the gills were impregnated with a tar‐like substance. Chlorine and crude oil are the suspected causal agents.
Phytoplankton ecology in an Antarctic lake
Authors: LIGHT J. J. , ELLIS‐EVANS J. C. , PRIDDLE J.
Published: May 2006

SUMMARY.
The ecology of the phytoplankton of Heywood Lake, Signy Island, South Orkney Islands, Antarctica was investigated during 1969–72. The lake, which is ice‐covered for 8–10 months per year, is moderately eutrophic due to enrichment by seal excreta.

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

SUMMARY.
The feeding rate of G. pseudolimnaeus was measured monthly for 7 months in the field by monitoring the decline in weight of gut contents when the amphipod was starved. This decline was modelled by an exponential regression of weight on time. As the amphipods appeared to be continuous feeders, feeding rate was calculated by multiplying the dry weight of a full gut by the specific rate of emptying, i.e., the slope of the exponential regression. Specific rate of emptying was independent of animal size, but increased with temperature. Therefore, food has a longer period in which to be digested at low temperatures, which suggests that assimilation efficiency may increase.

However, the assimilation efficiency of amphipods feeding on decaying maple leaves in the laboratory was only 10% and did not vary with temperature. Ingestion and egestion rates were measured in the laboratory by weighing amounts eaten and defecated. The turnover time of the contents of a full gut in the laboratory often agreed very well with turnover time measured in the field, i.e., the reciprocal of the specific rate of emptying, thus confirming the use of an exponential regression.