bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertical distribution of the zoobenthos in southeastern Lake Michigan with evidence of seasonal variation*
Authors: NALEPA THOMAS F. , ROBERTSON ANDREW
Published: May 2006

SUMMARY.
The vertical distribution of the zoobenthos in southeastern Lake Michigan was investigated monthly from May to November 1976. The organisms could be divided into two categories: one in which the majority of the population occurred in the upper 1 cm of substrate (Pontoporeia, naidids, chironomids, cyclopoids, harpacticoids, cladocerans, turbellarians, ostracods, rotifers, sphaeriids and gastropods) and one in which the majority of the population occurred deeper (immature tubificids without hair setae, Stylodrilus heringianus, enchytraeids, nematodes, and tardigrades). The vertical distribution of these infaunal forms showed a marked seasonal variation. They were found in the superficial sediments in the spring, but deeper in the sediments in the autumn. This trend coincided with the seasonal occurrence of a detrital layer that overlay the sandy substrate in the spring but was absent in the autumn.
The effects of temperature and meal size on the rate of gastric evacuation in perch (Perca fluviatilis) fed on fish larvae
Authors: PERSSON LENNART
Published: May 2006

SUMMARY.
The rate of gastric evacuation in perch (Perca fluviatilis) (89–170 mm length) fed on fish larvae was studied at temperatures between 12.0 and 21.7°C. Gastric evacuation rates were usually described by an exponential function. The instantaneous rate of gastric evacuation (R) was constant for a large number of different meal sizes. At higher food rations, a lag phase in digestion was found during the first part of digestion, and this ration size was smaller for smaller perch (89–110 mm) than for bigger perch (120–170 mm). Below these larger meal sizes, gastric evacuation was similar for the different size classes studied. The relation between R and temperature was described by an exponential function. The effects of meal size, number of food items, fish size and temperature on the rate of gastric evacuation are discussed.
The distribution and production of Gammarus pseudolimnaeus (Crustacea: Amphipoda) along a reach of the Credit River, Ontario
Authors: MARCHANT R. , HYNES H. B. N.
Published: May 2006

SUMMARY.
The population density of the univoltine amphipod Gammarus pseudolimnaeus was estimated monthly from April 1977 to June 1978 along a 600‐m reach using a form of removal sampling at 0.5, 1.5 and 2.5 m from the bank. The probability of catching an amphipod with three sweeps over an area of 0.15 m2 was 0.95. Drift and upstream migration were measured for 24 h, also monthly. Population density varied from 1600 m−2 (newly‐hatched young in July) to 26 m−2 (adults) within 3 m of the bank with 95% confidence limits of 40–60% of the mean; density was highest < 1 m from the bank and beyond 3 m it declined to insignificant levels. No significant difference could be shown between the total catches in the drift and upstream nets over a year and there appeared to be no net migration of amphipods. Mean drift was 2 amphipods day−1.

Growth was estimated from the length composition of monthly samples. Annual production (P) was 29.4 kg ha−1 for one generation of the amphipod with a P/B ratio of 4.65. Egg production accounted for only 2% of this estimate. Recruitment was calculated from regressions relating female length to clutch size and egg development time to temperature in the laboratory; mean temperature was measured in the field.

Mortality was greatest in July at the beginning of the generation. It was high again in September and during winter; at these later times it was suggested that starvation occurred in addition to predation. Annual consumption (C) of organic matter for the generation calculated from published data on feeding rate was 1547 kg ha−1 which results in a P/C ratio of 1.9%.
Distribution and feeding of larval Chironomidae in a gravel‐pit lake
Authors: TITMUS GRAHAM , BADCOCK RUTH M.
Published: May 2006

SUMMARY.
Replicated benthic samples were collected from a wet gravel‐pit in the English Midlands at fortnightly intervals during 1978. The aggregation patterns of the four most numerous genera, Chironomus, Polypedilum, Procladius and Tanypus, were analysed by fitting the means and variances of replicated sampling units to Taylor's power law and Iwao's plot of mean crowding against mean density. Chironomus larvae were not aggregated; all other genera showed an increased aggregation with density. The Iwao plots indicated that Tanypus larvae tended to be aggregated at low as well as high densities. Gut contents were analysed in larvae of the above genera and also in Cryptochironomus larvae, to investigate the relationship between dispersion pattern and feeding. Chironomus and Polypedilum larvae fed mainly on detritus, Tanypus on algae, Procladius on algae and crustacea and Cryptochironomus on oligochaetes. The extent of overlap in feeding niche was measured by Levins’ index and shown to be low in all except the pair feeding upon detritus. Differences in the feeding niche may partly account for the dispersion patterns of the genera investigated.
A key to larvae of the family Leptoceridae (Trichoptera) in Great Britain and Ireland
Authors: WALLACE I. D.
Published: May 2006

SUMMARY.
There are thirty‐one British leptocerid species in nine genera. A key is provided to identify larvae of all species at the final (fifth) instar and many species are also separated at earlier instars. The work is based on British material for all but one species.
Metabolism of a desert stream
Authors: BUSCH DAVID E. , FISHER STUART G.
Published: May 2006

SUMMARY.
Rates of photosynthesis and community respiration were determined for benthic assemblages in Sycamore Creek, a Sonoran Desert stream in Arizona. Benthos in this stream can be separated into (1) mats of Cladophora glomerata and associated epiphytes and (2) assemblages of epipelic diatoms and blue‐green algae. Community respiration and net photosynthesis were measured for these assemblages using submerged light‐dark chambers in situ. Multiple regression analysis was used to predict (1) gross photosynthesis as a function of photosynthetically active radiation, temperature and chlorophyll‐α concentration; and (2) community respiration as a function of temperature and biomass.

Calculations suggest that Sycamore Creek is autotrophic during the summer (P/R= 1.7) and that the rates of gross photosynthesis (P=8.5 g O2 m−2 day−1) and community respiration (R= 5.1 g O2 m−2 day−1) are high for a small stream. Considerable difference exists between the Cladophora mat assemblages, in which mean P is 12.5gO2m−2 day−1and the P/R ratio is 2.3, and the epipelic assemblages in which mean P is 4.4 g O2m−2 day−1 and P/R is 0.96. The high rate of gross photosynthesis, low litter inputs, high biomass of algae and the intermittent but severe floods that characterize Sycamore Creek indicate that this stream and other similar desert streams are net exporters of organic matter and are, thereby, truly autotrophic stream ecosystems.
Growth and recession of aquatic macrophytes on an unshaded section of the River Lambourn, England, from 1971 to 1976
Authors: HAM STEPHANIE F. , WRIGHT J. F. , BERRIE A. D.
Published: May 2006

SUMMARY.
The growth and recession of the macrophytes on an unshaded section of the R. Lambourn was documented by a mapping procedure from March 1971 to December 1976. The seasonal patterns were determined mainly by the dominant macrophytes. Ranunculus penicillatus var. calcareus and Ranunculus peltatus. Ranunculus grew rapidly in spring and early summer, mainly colonizing areas of gravel and reached a summer maximum. The greatest loss of plants was in August and September but losses continued through the winter to give minimum cover in March. Berula and Callitriche did not show regular seasonal growth patterns but their growth was largely confined to times when there was little growth of Ranunculus. Increase in area of Ranunculus in the spring was positively correlated with the mean discharge at that time. The growth of Ranunculus appeared to be restricted when shading was caused by turbid water due to dredging or by accumulation of epiphytic algae on the surface of the plants in years when discharge was low. Discharge also influenced the substrata underlying Ranunculus and the area of silt under Ranunculus beds was negatively correlated with discharge. The factors thought to influence growth of Ranunculus were used to develop a conceptual model of growth.
Effect of temperature on the duration of egg development, and moulting and growth in juveniles of Crangonyx pseudogracilis (Crustacea: Amphipoda) in the laboratory
Authors: SUTCLIFFE D. W. , CARRICK T. R.
Published: May 2006

SUMMARY.The interval between moults is an extension of egg development time, increasing from birth to sexual maturity which is probably reached at instar 6 or 7. The duration of each instar increased with the animal's age. Incubation time for eggs and the intermoult interval have the same curvilinear inverse relationship with water temperature in the range 3.5–25°C. Results are expressed as degree‐days above predicted threshold temperatures of 3.8°C for eggs and 3.2°C for instar 1 after birth, but inverse power‐law relationships were a better fit to the results, with exponents of ‐ 1.355 for eggs, ‐ 1.263 for instar 1 and ‐ 1.37 to ‐ 1.92 for instars 2–4. Temperature — dependence apparently altered in instars 5 and 6 at 15–25°C. From a multiple regression of geometric mean moult interval (Mi, days) against mean age (A) and temperature (T, °C),Mi= 56.4T−0.7e0.016A, with mean ages of 106 days at 15°C and 85 days at 25°C after six moults.

The mean number of primary flagellar segments on the antennules increased from 4.0 in instar 1 to 6.0 in instar 2 and 8.0 in instar 3. Thereafter, segments were added less regularly to give a mean of 13.2 in instar 7. In a natural population, when the sexes became distinctive they had 11–13 flagellar segments.

From birth atc. 0.05 mg wet wt, individual growth rates were highly variable; mean growth rates (Gs, % wet wt day−1) were similar in animals fed on dried, leached elm leaves and living, green leaves ofCallitriche; there was a power‐law relationship with temperature in the range 3.5–25°C, (Gs= 0.27T0.59). Faster growth rates were obtained on living leaves ofElodea. Sexual maturity is reached atc. 0.4–0.5 mg wet wt. A brief comparison is made withGammarus pulex;C. pseudogracilismay be better adapted to warm‐water habitats.
Grafham Water
Authors: STENT R. F.
Published: May 2006

SUMMARY.
The phytoplankton and zooplankton of Grafham Water reservoir, Cambridgeshire, are described and discussed for the 5 years 1974–78 together with the main physical variables and macro‐nutrients believed to affect them. This follows on from the Water Pollution Research Laboratory study of 1969–74. The rationale for the work was to provide short‐term warning of treatment and management problems caused by algae and to gain insight into the factors controlling them.

During the period reviewed the 1976 drought occurred with a massive draw‐down. Afterwards replenishment of the lake from the River Great Ouse resulted in its enrichment with high concentrations of nitrate, orthophosphate and silica. The algal cycles changed to some extent over this period with a few species becoming even more dominant and others diminishing in importance. The effect of the drought and post‐drought pumping is discussed; a return to former nutrient levels seems likely. The effects of weather, particularly radiation and wind, on algae may be of equal importance to nutrient levels in Grafham and will be further investigated.
Calorific values of pond invertebrates eaten by ducks
Authors: DRIVER E. A.
Published: May 2006

SUMMARY.
Calorific determination of twenty‐three species of aquatic invertebrates from various life stages, collected from prairie wetlands, ranged from 3682 cal g−1 dry wt for adult amphipods, Hyalella azteca, to 6270 cal g−1 dry wt for an adult female beetle, Agabus bifarius. The aggregate mean for the specimens was 5225 cal g−1 dry wt. All genera analysed here are eaten by ducks.
A study of the benthic communities of twenty lakes in the South Island, New Zealand
Authors: TIMMS B. V.
Published: May 2006

SUMMARY. The benthos of a heterogeneous series of lakes was sampled in late winter‐spring (before insect emergence) to determine species composition, community structure and standing crops. Nearly 50 species were found, with an average of only 12.4 per lake. Fifteen species occurred widely, with the same few species(Limnodrilus hoffmeisteri, Potamopyrgus antipodarum and sometimes Chironomus and Macropelopia spp.) often dominant. All taxonomic groups were of limited diversity; for instance, the maximum number of chironomids per lake was 8, with an average of 4.7 species. There were no chaoborids or mayflies, and very few isopods, amphipods, ceralopogonids and water mites. Niches of common species were broad.

Species composition and dominance were not related to lake trophic status; hence there were no indicator organisms. Standing crops varied only broadly with lake trophic status, probably because of the differential influence of extraneous factors such as relative depth and input of allochthonous organic matter and silt. Depth: biomass profiles were also variable and only partly correlated with trophic status. Instead, many lakes were grouped on the basis of geographical area and the influence of extraneous factors; species were grouped according to the relative extent of their distribution.
The growth of the freshwater crayfish A ustropotamobius pallipes in Northumbria
Authors: BREWIS J. M. , BOWLER K.
Published: May 2006

SUMMARY. Growth increments, moult frequency and growth rates of individuals in a population of the freshwater crayfish Austropotamobius pallipes were followed for a period of 3 years during a mark‐recapture study. There was an inverse relationship between body size and the growth increment relative to body size. The absolute increment increased from the juvenile to the young adult stage and thereafter declined with increasing body size.

Differences between the adult male, reproductive female, non‐reproductive female and juvenile subpopulations in the size of growth increments are reported and growth increments during the two major moult periods of each year are compared. The effect of the endoparasite Thelohania contejeani and of chela regeneration was to reduce slightly the growth increments.

Instantaneous growth rates declined throughout life in both sexes, but adult males maintained higher growth rates than adult females, particularly in the largest size class studied. The effect of reproduction on growth appeared to be most severe in the smallest breeding females. Males maintained the tendency to moult twice annually to a larger size than females. A simplified construction of the relationship between size and age in the population is presented for each sex. The oldest animals were estimated to be at least 11 years old.
Rate of food evacuation in roach (Rutilus rutilus) in relation to temperature, and the application of evacuation rate estimates for studies on the rate of food consumption
Authors: PERSSON LENNART
Published: May 2006

SUMMARY. Food evacuation in roach (total body length, range 75–150 mm) was studied at temperatures between 4.2 and 24.0 °C. The rate of food evacuation was described by an exponential function and was similar for two different food items (Daphnia and Chaoborus). The relation between the instantaneous rate of food evacuation (R) and temperature was also described by an exponential function. A model developed for estimating food consumption rates in fish was tested in a simulation experiment and there was good agreement between estimated and actual values for food consumption.
A quantitative study of the life cycle of the case‐building caddis Odontocerum albicorne (Trichoptera: Odontoceridae) in a Lake District stream
Authors: ELLIOTT J. M.
Published: May 2006

SUMMARY. Odontocerum albicorne (Scopoli) took 1 year to complete its life cycle in a 3‐year study of this species in a small, stony stream in the English Lake District. Adults were present from May to August (1967, 1968) or from June to September (1969); most eggs were laid in July and August. There were five larval instarsand most larvae were in instars III, IV and V by October. Larvae usually overwintered in instar V or III and some third instars were in a resting state in sealed cases. Most fifth instars became male pupae in spring; most third instars grew rapidly to instar V in spring and then became female pupae. The duration of the pupal stage was short, and was shown in laboratory experiments to require 87.5 degree‐days (95% C L = 79–98 degree‐days) above a threshold temperature of 6.7±0.01°C. Pupation in the stream did not commence until temperatures exceeded 6.8°C.

As the sample variance‐mean relationship followed a power‐law, the spatial distribution of larvae and pupae was density dependent. Relative clumping remained fairly constant between year‐classes but increased markedly between the larval and pupal stages. Although population density varied between year‐classes, it remained remarkably constant in each year‐class for about 9 months between the end of egg hatching and the start of adult emergence.

The growth pattern was similar in each year‐class but growth rates varied between year‐classes. The mean instantaneous growth rate was highest (range 3.9–8.0% dry wt day‐1)in the first 3 months of the life cycle (August‐October), close to zero in winter (November‐February) and slightly higher than 1% day‐1 (range 1.1–1.7%) for the rest of the life cycle (March‐August). Production varied considerably between years and year‐classes, and was closely related to growth rates for March‐August. Annual production estimates were 243, 160 and 257 mg dry wt m‐2 in 1967, 1968 and 1969. respectively. The ratio of production to mean standing crop (P/B) also varied between year‐classes and the mean annual value was 3.9 (range 3.2–4.5).

Life tables were similar for the 1966 (latter part only), 1967, 1968 and 1969 year‐classes. Losses were very high (c. 99%) in the egg stage and early instars. About 30% (range 27–31%) of the population in instars III‐V did not reach the pupal stage, and c. 25% (range 20–29%) of the pupal population died. About 37% (range 35–39%) of the emerging adults were females.
The life history and production of the leech Helobdella stagnalis (Hirudinea:Glossiphonidae) in the River Ely, South Wales
Authors: MURPHY P. M. , LEARNER M.A.
Published: May 2006

SUMMARY. A population of the glossiphonid leech Helobdella stagnalis was studied over a period of 16 months in the organically polluted River Ely, South Wales. There were two generations each year. The overwintering population released young (the spring‐brood) in June. The spring‐brood in turn produced their own offspring (summer‐brood) in August.

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

Annual population production (P) was 7.56 g wet wt m‐2, mean annual population biomass (B) was 1.43 g wet wt m‐2 and the annual P/B ratio was 5.29.
A field experiment on the value of allochthonous straw as food and substratum for lake macro‐invertebrates
Authors: STREET M. , TITMUS G.
Published: May 2006

SUMMARY. The relative importance of habitat structure and food availability to lake macro‐invertebrates was investigated experimentally. A gravel‐pit lake of uniform depth was partitioned into two parts and allochthonous material (straw) added to one half. Replicate litter bags of 0.3‐mm mesh size containing sisal string, straw, wood‐wool or polypropylene twine were added to each halt ol the lake in May 1980. After 2 months they were removed and the invertebrates within them identified and counted. Data were analysed statistically to determine the relative importance of bag Material and the level of allochthonous detritus in the vicinity of the bags (referred to as Food). Of the abundant taxa (> 5 individuals per bag mean density) only C hironomus was distributed independently of Material. The other abundant taxa (Gammmrus. Asellus, Cryptochirnomus and Helobdella stagnalis) were all more strongly influenced by Material than Food. The effect of Material on total numbers was 14 times more important than that of Food. Of the 17 taxa analysed, only Pisidium was distributed Independently of either faetor.

The relative abundance of total taxa was lowest in the sisal bags and greatest in the polypropylene and wood‐wool bags. This is presumably related to structural properties of these materials with high abundance coinciding with an open buoyant substratum similar to that provided by aquatic macrophytcs. The importance of Material for most taxa indicates that the structural properties of the habitat may be very significant in determining animal distribution.
A comparative study of three air‐lift samplers used for sampling benthic macro‐invertebrates in rivers
Authors: DRAKE C. M. , ELLIOTT J. M.
Published: May 2006

SUMMARY. From 16 air‐lift samplers described in the literature, three were selected for operation from a small boat: Mackey, Pearson et al. and Verollet & Tachet samplers. Random samples (number of sampling units n= 10) were taken in a large tank with a known number of dried peas, representing invertebrates, amongst stones of uniform size. Separate experiments were performed with three sizes of stones (modal sizes 2–4, 16–20 and 32–36 mm). Stratified‐random samples (usually n= 10) were taken in rivers at lour sites with modal particle sizes of < 0.1 2–4. 32–128 and 64–128 mm. The samplers were compared with a Ponar grab in the tank experiments and the field, and with a Naturalist's dredge in the field.

Rates of pumping at different air‐flows were established for each sampler. Water‐How increased with increasing air‐How and increasing submergence of the riser‐pipe. The Mackey sampler achieved the highest water‐flow and lifted more substratum and larger stones (64–128 mm) than the other samplers. The Verollet & Tachet sampler had the lowest pumping rate and failed to lift stones > 8 mm long, whilst the Pearson et al. sampler, with an intermediate performance, lifted mud and stones < 32 mm long.

In the tank experiments, the area from which the Mackey and Pearson et al. samplers collected peas varied with air‐flow, operating time and type of substratum. The Maekey sampler over‐sampled and the Pearson et al. sampler usually under‐sampled their respective sampling areas, except the latter sampler at high air‐flows gave approximately quantitative results comparable to those of the Ponar grab for peas on the surface of stones 16–20 mm. No sampler collected much at a depth of 3 cm on larger stones (32–36 mm), and the Verollet & Tachet sampler failed completely on all substrata.

In field trials, the Mackey and Pearson et al. samplers provided good qualitative samples except on large stones (32–128mm). The Verollet & Tachet sampler lifted little material. The relative abundance of taxa often differed between samplers. Estimates of the number of invertebrates per m2 differed widely between samplers except for the Pearson et al. and Ponar grab which gave similar quantitative results at three sites. Values were very low for the Verollet & Tachet sampler and Naturalist's dredge and always very high for the Mackey sampler which often grossly over‐sampled its sampling area. Therefore, these three samplers cannot be considered as quantitative. The relationship between the variances and the means of samples of peas in the tank and most invertebrates in the field followed a power law with values of the exponent b in the range 1.13–2.51.

The present study completes the evaluation of 14 samplers used to sample benthic macro‐invertebrates in deep rivers, and the more important conclusions from the comparative studies of seven grabs, four dredges and three air‐lift samplers are summarized in a table.
Food selection by Dreissena polymorpha Pallas (Mollusca: Bivalvia)
Authors: WINKEL E. H. TEN , DAVIDS C.
Published: May 2006

SUMMARY. The role of the selection systems in the mantle cavity and the stomach of Dreissena polymorpha was investigated by comparing the composition of particles in the plankton, the stomach and the mid‐gut. Both systems selected particles of 15–40 μm for food. The selection mechanism functioned more efficiently in the presence of simple algal mixtures than in the presence of lake plankton, but did not function at all in animals fed after 16 h starvation. The composition of successive pseudo‐faecal pellets differed. It is concluded that selection of different kinds of particle occurs in specific places in the mantle cavity. Cryptomonas spp. were highly preferred as food. Indications were found that not only does size‐selection occur, but also selection of a chemical nature.
Comparison of benthic macroinvertebrate fauna and substratum composition in riffles and pools in the impounded River Elan and the unregulated River Wye, mid‐Wales
Authors: SCULLION J. , PARISH C. A. , MORGAN N. , EDWARDS R. W.
Published: May 2006

SUMMARY. The macro‐invertebrate fauna and substrate were studied in a riffle and pool from a regulated (Elan) and an unregulated (Wye) river in summer. There were some differences in the substrate particle size distribution of the two rivers and between the riffle and the pool on the Wye. There was more detritus in pools than in riffles in both rivers and generally more in the Elan than the Wye. Deposits on the bed of the Elan were rich in iron and manganese.

On the Wye. there was a greater density of invertebrates in the riffle than in the pool, but species richness was similar. Most species showed some preferences for either the riffle or the pool. The riffle contained a substantial number of Ephemeroptera, Trichoptera, Plecoptera and Simuliidae (52%) whilst the pool was dominated by chironomids (71%). Compared with the Wye, total invertebrate density and species richness were reduced in the Elan. Some species characteristic of riffles were reduced or absent on the Elan. Invertebrate density on the Elan was similar in the riffle and pool; species richness was greater in the riffle. The distribution and abundance of invertebrates is discussed in relation to such environmental factors as water velocity through the substrate and dissolved oxygen supply in interstitial habitats.
Community structure in some southern English streams: the influence of physicochemical factors
Authors: TOWNSEND COLIN R. , HILDREW ALAN G. , FRANCIS JEANETTE
Published: May 2006

SUMMARY. 1. Invertebrates and fish were surveyed during October 1976 in thirty‐four stony riffle stream sites in Ashdown Forest, Sussex.

2. A variety of physicochemical factors were also measured in an attempt to assess the importance of each in determining the distribution of species and the structure of communities.

3. Three analytical techniques—stepwise multiple regression analysis, ordination and community classification—revealed that the structure of these communities was strongly related to variation in stream pH. Acid sites had low numbers of individuals, low species richness and low equitabilities. Summer temperature and stream discharge also appeared to play significant roles. The pattern of catchment land use was shown to have an important bearing on stream pH.

4. In the most acid sites only collectors, shredders and predators occurred. In more basic sites the number of species in collector and predator categories increased and these were joined by grazer/scrapers and filter feeders.

5. A theoretical basis for explaining stream community structure is discussed.
Monovalent—divalent cation ratios and the occurrence of phytoplankton, with special reference to the desmids
Authors: SHOESMTTH E. A. , BROOK A. J.
Published: May 2006

SUMMARY. We have analysed data from ninety‐nine Scottish freshwater lochs, to explore the relationship between water chemistry and phytoplankton assemblages. Our results confirm that there are strong correlations both between the phytoplankton quotient and divalent cation concentrations, particularly Ca++, and also between the phytoplankton quotient and the (Na++ K+)/(Ca+++ Mg++) ratio. However, the latter is evidently a spurious relationship, arising from the former association, together with an association between Ca++ and the (Na++K+)/ (Ca+++ Mg++) ratio. The observed correlation does not persist if account is taken of concomitant variations in the Ca++concentration. This conclusion is suggested both by relatively informal analyses (median polish, partial correlation coefficients) and by more formal modelling and testing (stepwise regression, all‐subsets regression).
The influence of elevated nitrate concentration on rate of leaf decomposition in a stream
Authors: MEYER JUDY L. , JOHNSON CAROL
Published: May 2006

SUMMARY.

Leaf decomposition was compared in two streams at the Coweeta Hydrologic Laboratory, North Carolina. U.S.A. One stream drains an undisturbed hardwood watershed, while the other drains a successional watershed subject to an insect outbreak. The successional watershed has elevated nitrate concentrations in the streamwater.

Both black locust (Robinia pseudo‐acacia) and sweet birch (Betula lenta) leaf litter decomposed 2.8 times more rapidly in the stream with high nitrate concentrations.

The more rapid decay rates appeared to be partly due to accelerated microbial processing in response to nitrate enrichment, because microbial biomass (as ATP) was higher in the nitrate‐enriched stream.

At each point in time, nitrogen and phosphorus content of the litter was lower in the high nitrate stream; however, there was no significant difference in nitrogen or phosphorus content at the same state of leaf decay in the two streams.
The effect of fungal parasitism on the succession of diatoms in Lake Maarsseveen I (The Netherlands)
Authors: DONK ELLEN VAN , RINGELBERG J.
Published: May 2006

SUMMARY. During late winter and early spring, diatoms are predominant in Lake Maarsseveen I and show a succession in blooming. To elucidate the role of parasitism in this succession, samples were taken once a week in 1978, 1979and 1980 and examined for fungal parasites, further, factors which presumably influenced the phytoplankton growth. including temperature and chemical compounds, were studied. Parasites were found on Asterionella formosa Hass., Stephanodiscus astraea (Ehr) Grun. and Cyclotella comta (Ehr) Kütz. The chytrid fungus Zygorhizidium planktonicum

Canter was parasitic tin Asterionella formosa. This was the only case where high infection percentages were registered. The developmental phases of Zygorhizidium plunktonicum on Asterionella formosa were studied. The fungus was capable of affecting the spring increase and bringing about a premature end to the bloom. Only when the fungus was temporarily inhibited in its parasitic activity (this phenomenon coincided with periods of frost) was A. formosa able to reach a high abundance. Severe parasitism on A. formosa favoured the development of other diatoms (mainly of Fragilaria crotoriensis Kitt., Stephanodiscus hantzschii Grun. and Stephanodiscus astraea).

Host‐parasite interrelationship studies performed in the laboratory showed that temperature can be an important environmental factor associated with epidemics of Zygorhizidium plankiomcum on Asterionella formosa. At very low temepratures (1.5. 1) the fungal activity was inhibited while Asterionella fortnosa still grew well. However, at 5, 10 and 18 the fungus manifested a high infection rate and was able to overtake Asterionella.
The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A.
Authors: STRAYER DAVID
Published: May 2006

Stream size and surface geology are the two major environmental features thai control the distributions of the thirty‐four species of unionid mussels living in the streams of southeastern Michigan.

Surface geology, a previously unrecognized factor in the ecology of freshwater mussels, acts lo regulate the hydrology, slope and turbidity of streams in the study area.

Reciprocal averaging ordinations are used to aid the description of the habitats occupied by each mussel species.
The influence of feeding habits on whole‐body metal concentrations in aquatic insects
Authors: SMOCK LEONARD A.
Published: May 2006

SUMMARY.

Concentrations of seven metals in forty taxa of aquatic insects were determined in order to examine the influence of the insects’ feeding habits on their whole‐body metal content. Species were grouped into five feeding categories which reflected both the type of material the organisms ingested and their contact with sediments during feeding.

Species such as the burrowing mayflies (Ephemeridae) and some of the Chironomidae, which indiscriminately ingest sediment along with detritus, had the highest concentrations of most metals. Filter feeders (e.g. Hydropsychidae) had the next highest concentrations, followed by species which to some degree selectively ingest detritus and periphyton (e.g. many Ephemeroptera, Plecoptera and Trichoptera). Carnivores and surface feeding species, such as the Gerridae and Gyrinidae, had the lowest metal concentrations.

Analysis of metal concentrations of both gut contents and bodies of individuals from each of these feeding types explain these differences. Gut material was enriched in most metals (Co, Cr, Fe, Sb, Sc) relative to their concentrations in the organism's body and it often constituted a major proportion of an organism's whole‐body burden of a metal.

Both the concentrations of metals in the gut material and the proportion of the whole‐body burden of a metal that was associated with gut contents varied with the feeding habit of a species. This was because of differences in the amount of inorganic material ingested by the species in each feeding category, higher concentrations occurring in organisms which ingested relatively greater amounts of sediment.

Organism concentrations of K and Na were less affected by feeding habits since the majority of the whole‐body burden of these metals was associated with an organism's tissue and surface rather than with gut material.
The physical limnology of Augher Lough (Northern Ireland)
Authors: RIPPEY BRIAN
Published: May 2006

SUMMARY.

The physical limnology of Augher Lough, Northern Ireland (area=9.25 ha. z=5.5 m), including stratification pattern, heat budget, thermocline erosion rate, eddy diffusion rate in the thermocline and hypolimnion and areal hypolimnetic oxygen deficit is described.

Oxygen and temperature profiles, recorded at two sites during 1978 and four sites during 1979, showed that spatial variability of these quantities was low and allowed the following lake characteristics to be estimated. Heat budgel was 5.30 kcal cm‐2 (standard deviation=s=0.26) in 1978 and 5.00 (s= 0.26) in 1979. The thermocline depth was 3.5–6.5 m with an erosion rate of 1.9X10‐7 m s‐1 in 1979. Eddy diffusion coefficients of heat in the thermocline and hypolimnion normally ranged from 0.48X 10‐2 cm2 s‐1 (s=0.20X10‐2) to 5.4X10‐2 (s=2.6X10‐2), but reached 10X10‐2 cm2s‐l (s=9X10‐2) in early July 1978 after a cooling‐mixing episode in the epilimnion. The hypolimnetic oxygen deficit was 680 mg O2 m‐2 d‐1 (s=76) and varied strongly with depth.

A cooling‐mixing episode in the epilimnion in June‐July 1978 caused the movement of heat down to 8 m, movement of oxygen down to 6 m and increased the eddy diffusion coefficients of heat by an order of magnitude.
Biomass and production of phyto‐ and bacterio‐plankton in eutrophic Lake Tystrup, Denmark
Authors: RIEMANN BO
Published: May 2006

SUMMARY.

Phytoplankton primary production and biomass were compared with bacterial secondary production estimated by means of frequency of dividing cells (FDC) in eutrophic Lake Tystrup. Denmark.

In the upper part of the photic zone, bacterial secondary production constituted 12% of the carbon fixed by the phytoplankton. In vertical profiles, bacterial secondary production ranged from 7.6% (early spring) to 121% (during August) of the carbon fixed by the algae.

A close relationship was found between occurrence and activity of bacteria and algae, suggesting that released organic products are of primary importance to the bacteria.

The annual phytoplankton primary production was estimated as 227 g C m‐2 compared to 102 g C m‐2 assimilated by the bacteria, so 45% of the carbon fixed by the phytoplankton went through pelagic bacteria.
On the biology of the catfish Chrysichthys auratus (Geoffory) in the man‐made Tiga Lake in Northern Nigeria
Authors: STURM M. G. de L.
Published: May 2006

SUMMARY. (1) A study was made of the biology of Chrysichthys auratus, a bottom‐feeding omnivore, in Tiga Lake, a man‐made lake in Northern Nigeria.

(2) Ripe females were present from April to September, coinciding with the hot season and rise in water level. First spawning took place at age II in females. No ripe males were found, and this was attributed to their spatial separation. Absolute fecundity was related to length and ranged from 327 to 1466 in forty‐six females.

(3) Hyaline rings on the centra of lumbar vertebrae were counted to age 235 fish. The first ring is laid down at the end of the second year, after which the rings were formed annually, probably during the breeding season. The fish live for up to 6 years. There is a good fit of the growth curve to the von Bertalanffy equation. Growth is slow and a smaller maximum size is attained than in rivers.
Seasonal changes in the concentration and colour of humic substances in some aquatic environments
Authors: VISSER S. A.
Published: May 2006

SUMMARY. 1. Between February and September 1974, concentrations of fulvic and humic acids in waters from a cryoboreal region of the Precambrian Shield in Quebec varied between 0.5–6.1 mg 1−1 and 0.1–6.5 mg 1−1 respectively. Whereas the fulvic acids usually remained relatively constant during this period, humic acids showed appreciable increases.

2. The number and weight average molecular weights of the fulvic acids (∼5000 and ∼22,000 daltons respectively) were lower than those of the humic acids (∼20,000 and ∼75,000 daltons respectively). The average molecular weight of the aquatic humic matter often decreased during late summer and early autumn. During spring floods the molecular weight of fulvic acids increased and that of humic acids declined.

3. Because the aquatic humic acids were more intensely coloured than fulvic acids, they contributed more than 30% of the colour of the water even though they accounted for only 15% of the concentration of humic matter. The colour intensity of both fulvic and humic acids generally appeared to increase during the latter part of the summer, when there was normally a decrease in the value of the colour quotient (E4/E6 ratio), indicating the accumulation in the waters of more humified material.
The influence of drought on the fish and invertebrate populations of an upland stream in Wales
Authors: COWX I. G. , YOUNG W. O. , HELLAWELL J. M.
Published: May 2006

SUMMARY. 1. The exceptionally dry summer of 1976 presented an opportunity to assess the impact of drought on the fauna of an unregulated stream in Wales.

2. Total number of macroinvertebrates varied from 1808 m−2 in September 1976 to 7412m−2 in August 1977. Two main effects of drought were observed: an initial reduction in abundance during the drought and a change in community structure in the following year, probably through impaired reproduction.

3. Trout density ranged from 0.075±0.028 to 0.402±0.093 m−2 and salmon parr density varied between 0.014±0.004 and 0.414±0.119 m−2. The only detrimental effect of the drought on the fish fauna was the elimination of the 1976 year class of young salmon. probably due to prolonged high water temperature.
Errors in instar determination of mayflies (Ephemeroptera) and stoneflies (Plecoptera) using the simple frequency, Janetschek, Cassie and Dyar's law methods
Authors: FINK THOMAS J.
Published: May 2006

SUMMARY. 1. The reliability of the simple frequency, Janetschek, Cassie and Dyar's law methods for determining or corroborating instars of mayflies and stoneflies was evaluated using data from published studies, a population of Baetisca rogersi and populations simulated through use of random numbers and generated normal distributions.

2. The Janetschek and Cassie methods are variations of the simple frequency method that offer no significant advantage. Modes of the Cassie method, thought to represent instars, are much more difficult or impossible to detect than are the corresponding peaks of the other two methods.

3. Overlap in size between adjacent instars can lead to false instar peaks or modes in frequency plots. The potential for overlap in mayflies and stoneflies is greatly increased, compared to other insects, because of their large number of instars and known developmental variability. The normal distribution simulations demonstrated that instar size variability as low as 5–7.5% COV (coefficient of variability) may lead to false instar peaks when the number of instars is in the typical range. These simulations also indicated that even simple frequency plots with distinct peaks may result in inaccurate instar determinations.

4. The number of size classes used in an analysis was correlated with the number of peaks or modes revealed. The number of peaks greater than zero in the Janetschek plots for the Baetisca rogersi population varied from 5 to 53 as the number of size classes was varied from 20 to 188. Similarly for the random number simulations. the number of peaks varied from 6 to 41 as the number of size classes varied from 22 to 127.

5. Dyar's law semi‐logarithmic plots do not corroborate instars determined through frequency methods, because the uniform spacing of‘instar’data points is the direct result of the uniform spacing of peaks in frequency plots of most data sources (including random numbers), whether or not peaks actually indicate instars. Also Dyar's law plots will‘corroborate’different numbers of instars depending on the peak selection criteria used. The potential for corroborating instars through supplemental rearing and best‐fit analysis is discussed.

6. The future of mayfly—stonefly instar determination lies in the increased and more rigorous application of the rearing and Palmen body (mayflies only) methods.
Lake restoration by biomanipulation: Round Lake, Minnesota, the first two years
Authors: With JOSEPH SHAPIRO , WRIGHT DAVID I.
Published: May 2006

SUMMARY. 1. Rotenone was applied to Round Lake in the autumn of 1980 in order to eliminate predominantly planktivorous and benthivorous fish. The lake was subsequently restocked with a higher population density of piscivores. The effect of this biomanipulation on the phytoplankton and zooplankton communities and on total nutrient concentrations was monitored at fortnightly intervals during the summers, from May 1980 to September 1982.

2. The abundance of phytoplankton was much lower after biomanipulation and was consistent with observed changes in Secchi disc transparency, total attenuation coefficient and chlorophyll a concentration. Zooplankters were also less abundant in 1981 and 1982 but the decrease in numbers was more than offset by the large increase in the mean sizes of the zooplankters present, so that the estimated grazing pressures in 1981 and 1982 were at least double the 1980 value.

3. Daphnia, rare in 1980, became the dominant genus in 1981 and 1982, and a shift to progressively larger‐bodied Daphnia species was observed.

4. Although total nitrogen and total phosphorus levels were generally lower after biomanipulation, their decline could not explain the reduction in phytoplankton abundance which was attributed to the increased grazing pressure. Possible causes of the observed declines in nutrient concentrations are discussed.
Concentrations and annual loading of dissolved organic matter in a small moorland stream
Authors: GRIEVE IAN C.
Published: May 2006

SUMMARY. 1. Dissolved organic matter (DOM) was measured at 8h intervals over a 1 year period in a stream draining 51 ha of moorland with peaty soils.

2. DOM concentrations increased with increasing stream discharge from low flow values of 0–3 mg 1−1 to maximum values of 30 mg 1−1. There were also seasonal differences of up to 13mgl−1 between August (maximum) and February, and differences of about 2.5 mg l−1 between rising and falling stage samples.

3. Seasonal variation was closely related to mean temperature.

4. Total loss over the year was 168 kg ha−1 DOM (84 kg ha−1 C), larger than previous estimates for upland sites.
Influence of food quality and temperature on life history characteristics of the parthenogenetic mayfly, Cloeon triangulifer
Authors: SWEENEY BERNARD W. , VANNOTE ROBIN L.
Published: May 2006

SUMMARY. 1. Laboratory and field data indicate that Cloeon triangulifer McDunnough has at least three generations per year in White Clay Creek (Pennsylvania, U.S.A.).

2. The duration of the egg stage ranged from 5 days at 30°C to about 90 days at 10°C.

3. Larvae completed development (i.e. first instar to adult) in 27 days at 25°C, 45 days at 20°C, and 179 days at 10°C on an algal diet dominated by diatoms.

4. Larvae reared on hickory leaves completed development in 30 days at 25°C but died prior to metamorphosis at 10, 15 and 20°C.

5. Adult size (i.e. body length, wing length and dry mass) and fecundity were inversely related to rearing temperature for all laboratory and field experiments.

6. The significant interaction of food quality and temperature suggest that these factors may be important in understanding geographic variation in the life history of C. triangulifer.
Alkaline phosphatase activity and cellular phosphorus as an index of the phosphorus status of phytoplankton in Minnesota lakes
Authors: GAGE MAURA A. , GORHAM EVILLE
Published: May 2006

SUMMARY.Total alkaline phosphatase activity is inversely related to cellular phosphorus in the particulate organic matter of waters above and below the thermocline in nine Minnesota lakes. Diagnostic criteria for assessing surplus and limiting levels of phosphorus are proposed. When applied to seasonal changes in phosphorus status in Lake Josephine, they demonstrate severe phosphorus starvation in late summer and autumn.
Studies on Chironomidae in experimental recirculating stream systems. II. The growth, development and production of a spring generation of Orthocladius (Euorthodadius) calvus Pinder
Authors: LADLE M. , COOLING D. A. , WELTON J. S. , BASS J. A. B.
Published: May 2006

SUMMARY.

Orthodadius (Euorthodadius) calvus Pinder. similar to Orthocladius (Euorthodadius) thienemanni Kieffer. colonized a new gravel substratum in two recirculating stream channels. A maximum population density of 68.621 m‐2 was attained after only 16 days. This had fallen to a negligible density by the thirty‐third day.

Some recruitment occurred over most of the study period (April‐May 1981) and no single sharply defined cohort was evident. There was a large range of body lengths within each instar. and considerable overlap between instars. The population density estimates for instars I and II were low compared with instars III and IV.

The relationship between instantaneous growth rate (g) and geometric mean length indicated that growth was best described by a Gompertz curve. Growth rate decreased with increasing length from a value of about 40% length day‐1 at 2 mm body length to about 5% length day‐1 at 9 mm.

Growth rates for individual larvae, kept in culture, were very variable with maximum rates close to the values determined from the field data. Mean duration of larval life was 16 days.

Estimates of production for the study period ranged from 13.5 g dry wt m‐2 (Channel III, size‐frequency method) to 34.2 g dry wt m‐2 (Channel II, Allen's graphical method, values corrected for non‐linear growth).

Gut contents were estimated to represent about 55% of the total weight therefore production values should be reduced by this amount.