bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of components controlling net phytoplankton photosynthesis in a well‐mixed lake (Lough Neagh, Northern Ireland)
Authors: JEWSON D. H.
Published: May 2006

The homogeneous distribution of the phytoplankton in a shallow (mean depth 8·6 m) unstratified lake, L. Neagh, Northern Ireland, facilitated the study of the interaction of components controlling gross photosynthesis per unit area. These included the photosynthetic capacity, the phytoplankton content of the euphotic zone, and a logarithmic function describing the effective radiation input. These factors were analysed for two sites, the open lake and Kinnego Bay, which respectively had standing crops of up to 90 and 300 mg chlorophyll a m−3 and maximum daily rates of gross integral photosynthesis of 11·7 and 15·6 g O2 m−2 day−1. Values are reduced by the high contribution to light attenuation by non‐algal sources, which increases at low standing crops particularly in winter, when values of integral photosynthesis decrease to 0·5 g O2 m−2 day−1. This relative change is the result of self‐shading behaviour of the phytoplankton altering the crop content of the euphotic zone at different population densities. Changes in the irradiance function, incorporating day length, are largely responsible for the changes in daily rates of integral gross photosynthesis; as daily irradiance is also a determinant of water temperature, it exerts further influence through the photosynthetic capacity which was strongly correlated with temperature. Much of the gain in gross photosynthesis resulting from higher photosynthetic capacity may not be reflected in a higher net column photosynthesis, because of the greater proportional rise in respiration with temperature. The balance in the water column between respiration losses and photosynthetic input may frequently alter since the ratio of illuminated to dark zones is between 1/4 to 1/5 in the open lake, and small shifts in any of the controlling features may result in conditions unfavourable for growth. This is analysed especially for the increase of diatoms in spring, when small modifications of the underwater light field can delay growth.
The macrophytic vegetation of the River Tees in 1975: observed and predicted changes
Authors: HOLMES N. T. H. , WHITTON B. A.
Published: May 2006

SUMMARY. An account is given of the distribution of macrophytes in the River Tees and its tributaries, north‐east England, together with a critical discussion of the problems involved in recording data in a form which can be used for monitoring long‐term changes of vegetation in rivers. Among the conventions and methods adopted in the present study are an attempt to define the vertical limits of the river sensu strictu as opposed to the bank, the extension of the term macrophyte to include as many visually obvious photosynthetic organisms as possible, the use of a check‐list prepared in advance which contains a wider range of species than are actually expected for the river, and the collection of two different types of standard record for each 0.5 km length of river. The Tees has been the subject of intermittent observations on its vegetation for some 45 years. The most obvious change has taken place since 1965, with a substantial upstream spread of four submerged angiosperm species. Potamogeton crispus, Zannichellia palustris and Myriophyllum spicatum were previously present only in the lower reaches of the Tees, and have spread 25, 9.5 and 4.5 km respectively upstream from their previously known most upstream localities. Ranunculus penicillatus var. calcareus is an apparent invader to the river. It seems probable that these changes have taken place since 1971 as a result of regulation of the Tees by Cow Green Reservoir. Further changes are predicted with the advent of water transfer from the Tyne to Tees around 1980, because at least twenty‐six macrophytes are known to be present in the former river that are either absent or confined to the lowest stretches of the latter.
The Zambezi River in Moçambique
Authors: HALL ARISTIDES , VALENTE ISABEL MARIA C. B. S. , DAVIES BRYAN R.
Published: May 2006

SUMMARY. Surveys of the physico‐chemical status of the River Zambezi in Moçambique were conducted between April 1973 and May 1974, to characterize the river prior to the closure of the Cabora Bassa Dam and to provide baseline data from which future changes in the river ecosystem can be followed.

The temperature of the river water increases by about 3°C from Lake Kariba to the sea, and with an average pH of 7.8 the water is slightly more alkaline than Kariba Dam water. The river is well oxygenated with no sign of hydrogen sulphide. Transparency is generally very low and changes are mainly determined by the floods of local tributaries. The overall average total alkalinity is 55 mg 1−1 CaCO3, with no regular seasonal variation, average concentrations of chloride and sulphate are respectively, 5.4 mg 1−1 Cl− and 5.3 mg 1−1 SO2‐4. They increase under both the influence of the ionically rich Shire River and the sea; the latter due to vertical mixing. Total hardness and calcium hardness behave in a similar way, while conductivity and silica concentrations increase slightly until the Zambezi—Shire confluence, at which point, conductivity increases by 25% to an average peak value of 153 μS cm−1, and silica decreases by 15% to a minimum average value of 15.5 mg 1−1 SiO2. Ammonia and nitrate concentrations show a clear seasonal variation, with respectively, minimum dry season and maximum wet season average values of about 0.05 mg 1−1 and 0.3 mg 1−1. The overall average concentration of nitrite is 0.004 mg 1−1. Orthophosphate in the river is mostly affected by Lake Kariba, though other sources are also of some importance. Maximum average concentrations of about 0.4 mg 1−1 PO3‐4 were recorded during the dry season after the overturn of Lake Kariba. The concentration of dissolved metals is mainly determined by the outflow of Kariba and by the Shire River, with only K and Mg apparently affected by the outflow from Lake Kafue.

It is concluded that the water quality of the Middle Zambezi is mainly determined by the Kariba Dam, with the Kafue Dam playing a minor role. At the time of the pre‐impoundment survey, the main impact on water quality of the Lower Zambezi came from the Shire River. With the addition of yet another large reservoir on the Zambezi, in the form of Cabora Bassa, together with the appreciable effect of tributary rivers on the lake, and the likely increased impact of the Shire River on the now more regulated river, the quality of the Lower Zambezi is expected to alter considerably, with concomitant ecological changes.
Uptake of copper and lead by a metaltolerant isopod Asellus meridianus Rac.
Authors: BROWN BARBARA E.
Published: May 2006

SUMMARY. Asellus meridianus from sites on the rivers Hayle and Gannel accumulates both copper and lead from experimental solutions: tolerant animals also accumulate copper and lead from metal‐enriched food. Copper‐tolerant animals accumulated up to 6.8 μg mg−1 copper after feeding on a copper‐enriched diet for 12 days whereas non‐tolerant animals showed no evidence of copper accumulation from food and no survivors remained after 8 days. Lead‐tolerant animals accumulated up to 28 μg mg−1 lead during a 14‐day exposure to a lead diet: non‐tolerant animals showed no accumulation of lead from food and no live animals remained after 10 days.

A marked difference in the storage forms of copper is observed in the hepatopancreas of copper‐tolerant isopods, as compared with non‐tolerant animals, when samples are taken from natural populations.
Life‐cycle, drift and production of Gammarus pulex L. (Amphipoda) in a Danish spring
Authors: IVERSEN TORBEN MOTH , JESSEN JACOB
Published: May 2006

SUMMARY. Gammarus pulex L. was studied at three sites in a Danish spring. Breeding took place during the summer and therefore cohorts could be followed. Sexual maturity was not reached until the next summer and maximum age appeared to be two years.

Changes in population size differed between stations and was tentatively related to differences in drift and numbers of predators. Generally the drift was non‐selective between cohorts and within cohorts.

Yearly production estimated from production curves was 2.6 g dry weight m−2 (the young cohort) and 1.2 g dry weight (the old cohort) at Station 1. The respective P/B̄ ratios were 3.35 and 1.22. Production of the youngest cohort at the three stations in the period September‐May was 0.9–1.3 g m−2 and P/B̄ ratios were 2.14–2.31. Total yearly production at the three stations was estimated at 4–7 g dry weight m−2.
Denitrification in Lake Kinneret in the presence of oxygen*
Authors: CAVARI B. Z. , PHELPS G.
Published: May 2006

SUMMARY. Denitrification experiments under anaerobic and aerated conditions were carried out in the laboratory with Lake Kinneret water and with pure cultures of the denitrifying bacteria Pseudomonas aeruginosa 2 Kin isolated from the lake. Although losses of nitrogen in Lake Kinneret due to denitrification have been found to occur during periods when dissolved oxygen exceeded 5 mg l−1 it was found that under aerated conditions glucose as a carbon source must be added in order to get denitrification in the laboratory.

Disappearance of nitrogen during the experiments was due to denitrification as shown by the nitrogen balance calculated for each sampling. The ATP content showed that no proliferation of cells took place during the experiment.

The rate of denitrification was strongly influenced by and was directly proportional to nitrate concentrations. Temperature has a very slight effect on the denitrification rate. Q10 for the range 15–30°C was 1.35.

The role of denitrification in the nitrogen balance of Lake Kinneret is discussed.
Hydraulic conditions in isothermal lakes
Authors: SMITH I. R.
Published: May 2006

SUMMARY.
The paper considers the forms of water movement that occur in unstratified lakes. Although not dealing directly with ecological implications, it is hoped that it will encourage the inclusion of observations of underwater weather as part of normal limnological routine. It is particularly concerned to show what observations are most effective in revealing hydraulic conditions.

Relations between wind, lake geometry and wave characteristics are examined. Factors determining the steady, wind‐driven circulation are reviewed and examined in sequence: the action of wind on a water surface and the current directly generated by the wind drag; the effect of the earth's rotation; the need to balance the flow in and out of any part of the lake; the influence of lake morphometry. A simple model of lake circulation is developed that may help in the interpretation of on‐lake observations. Some other features of isothermal motion are discussed including the horizontal currents associated with unsteady wind conditions (seiches).

The possible interaction between waves and currents are discussed. A tentative classification of hydraulic conditions in terms of wind speed, lake depth and fetch is suggested as a basis for forming hypotheses about the motion prior to on‐lake observations and as a possible starting point for a comparative approach.
Life‐history and production of the amphipod Gammarus pulex in a Dorset chalk stream
Authors: WELTON J. S.
Published: May 2006

SUMMARY.
The seasonal variation in population density of Gammarus pulex was studied in a Dorset chalk stream. The numbers increased markedly in June and July and reached a maximum of c. 10000m−2 in September whilst the most rapid decline in density occurred in October‐November and reached a minimum of 820 m−2 in February. The animals occurred in greater densities in habitats containing Ranunculus or Callitriche than in those devoid of vegetation. The population structure was determined monthly and was split into juveniles (length <4mm), immature males, immature females, mature males and ovigerous females. The percentage of juveniles (39–76) was always the highest of any of the categories. Ovigerous females were found at all times of the year. The sex ratio varied with the time of year both for immatures and matures, although there was approximately a 1:1 ratio for the mature individuals. Seasonal variation in biomass showed a maximum of 7.l g dry wt m−2 in September and a minimum of 1.4 g dry wt m−2 in March. Production was calculated by two methods giving values of 12.9 g dry wt m−2 year−1 and 12.8 g dry wt m−2 year−1.
Life‐cycles of lotic populations of Spongilla lacustris and Eunapius fragilis (Porifera: Spongillidae)
Authors: WILLIAMSON CRAIG E. , WILLIAMSON GAIL L.
Published: May 2006

SUMMARY.
The life‐cycles of green and white morphs of the freshwater sponge Spongilla lacustris were examined in the light of past evidence that zoochlorellae may augment their sponge host's nutrition. Field collections from a lotic population of S. lacustris were supplemented by laboratory experiments on gemmule hatching and gemmule size. Both white and green S. lacustris produced sperm for a 6‐week period in 1976 starting in the middle of May. Out of thirty white and thirty green sponges examined during this period, twenty white and ten green sponges contained sperm. Sperm production in both morphs was limited primarily to the basal 3.18mm of sponge tissue, and the density of sperm packets in the two morphs was the same. Out of 180 white and green sponges examined in 1976, only four eggs, no embryos, and no larvae were observed. White sponges gemmulated a week or two earlier, and produced smaller gemmules which were more uniform in size than those of green sponges. White and green gemmules hatched synchronously in the spring. In 1977 one female and numerous male specimens of S. lacustris, and numerous females but no males of another sponge, Eunapius fragilis, were found. The life‐cycles are discussed in the light of other recent studies on freshwater sponges.
The identification of British limnephilid larvae (Trichoptera: Limnephilidae) which have single‐filament gills
Authors: WALLACE I. D.
Published: May 2006

SUMMARY.
Keys are provided to identify those British limnephilid larvae which are characterized by having gill sites occupied solely by single filaments at the final instar. Most species can be identified at the final instar but many species can also be identified at the earlier instars. A key is also supplied to distinguish the early instar larvae as a group from other limnephilid larvae. Brief notes on distribution and habitat are given. The species identified at least at the final instar are:‐ Apatania wallengreni, A. auricula, A. muliebris, Drusus annulatus, Ecclisopteryx guttulata, Potamophylax latipennis, P. cingulatus, P. rotundipennis, Melampophylax mucoreus, Allogamus auricollis, Hydatophylax infumatus, Chaetopteryx villosa. It was not possible to segregate Halesus radiatus from H. digitatus, Stenophylax permistus from S. vibex, or S. lateralis from S. sequax.
Further studies on the palaeolimnology and changes in the phosphorus budget of Barton Broad, Norfolk
Authors: MOSS BRIAN
Published: May 2006

SUMMARY.
Patterns of sedimentation have been studied in Barton Broad, Norfolk, a man‐made lake created by peat excavation prior to the fifteenth century. Sedimentation rates since before 1800 have increased by as much as 50‐fold owing to the effects of hypereutrophication and sediment movement downriver into the lake. A striking horizontal pattern has been found; a long black tongue of sulphide‐rich sediment extends into the broad from the inflow river. This dates (210Pb method) back to 1920–30 and is associated with enrichment from sewage effluent and a change from a macrophyte‐dominated to a plankton‐dominated lake. Past phosphorus concentrations (1800, 1900, 1920, 1940) and budgets have been predicted from sediment core analyses by use of a model previously validated by contemporary measurements on the lake. The analyses and calculations provide a perspective for plans to restore the lake to a less fertile state capable of supporting aquatic macrophytes.
Calcium balance in premoult and post‐moult Gammarus pulex (Amphipoda)
Authors: WRIGHT D. A.
Published: May 2006

SUMMARY.
Adult Gammarus pulex lose about 42% body calcium into solution over a 2–3‐day period preceding the moult. A further 54% body calcium is lost with the exuviae, leaving c. 4% in the newly moulted animal.

Nearly all of the body calcium in a stage A (post moult) animal is contained in the hepatopancreas and a transient increase in the calcium content of this tissue is seen in some individuals. The haemolymph calcium compartment is heavily depleted at this stage. In stage B animals the hepatopancreas calcium level has returned to, or even fallen below, the intermoult level while the haemolymph calcium concentration remains lower than in intermoult animals.

Animals switch from a strongly negative calcium balance to a state of rapid calcium uptake immediately following moult. Uptake at 10°C proceeds at a rate of between 3 and 10 μmol g−1 h−1 depending on the calcium concentration of the external medium. The lower rate is found in starved animals in 0.1 mM calcium and this concentration is probably close to a minimum for the satisfactory restoration of body calcium. Recalcification is completed in 10–14 days in 0.1 mM calcium and is apparently enhanced by the presence of food in the form of a portion of oak leaf together with the cast exuviae. In 1.0 mM calcium the recalcification period is shortened to 3–4 days. This is considerably longer than the time recorded for French populations of this species (Vincent, 1969), although reasons for this are offered.
Phytobenthos of the River Tees and its tributaries
Authors: HOLMES N. T. H. , WHITTON B. A.
Published: May 2006

SUMMARY.
A standard method is given for describing plant communities in fast‐flowing streams and rivers. This involves the selection of a representative 10‐m length of stream (termed a reach) which can be re‐located exactly. Various estimates of the relative areas covered by different physiognomic forms and the relative proportions of species present are then combined to give a ‘semi‐quantitative’ account, which can be compared with data collected at other sites or times. The method has been applied to six sites on the River Tees system. A site below Cow Green reservoir with markedly regulated flows, differs from the others in various ways. Bryophytes show a greater cover here than elsewhere throughout the year and a conspicuous cover of Phormidium occurs in autumn. Filamentous green algae of many different species are abundant at this site in late summer and early autumn. At the most downstream site where such seasonal growths also occur, a single species, Cladophora glomerata, is dominant. Conspicuous spring diatom ‘bursts’ occurred at the two upstream sites and a month later at the two downstream sites.
Two‐egged ephippia in the chydorid Cladocera
Authors: FRYER GEOFFREY , FREY DAVID G.
Published: May 2006

SUMMARY.
With a single reported exception, the ephippia of all specialized chydorid cladocerans hitherto described contain a single egg. Ephippia the European Chydorus ovalis and the North American species currently listed as C. cf. sphaericus have been found persistently, and so far invariably, to contain two eggs. The alternative strategies of producing 1‐and 2‐egged ephippia are briefly considered. Anomalous 1‐egged ephippia of Daphnia (family Daphniidae) are also mentioned.
The seasonal cycle of inorganic carbon species in Cazenovia Lake, New York, 1977 *
Authors: EFFLER STEVEN W. , FIELD STEPHEN D. , QUIRK MICHAEL
Published: May 2006

SUMMARY. Spatial and temporal distributions of inorganic carbon and related ionic species (Ca2+, H+) were monitored weekly for 1 year in Cazenovia Lake, a small mesotrophic marl lake. Attendant [H2CO*3]([H2CO3] + [CO2(aq)]) and CaCO3 equilibrium conditions were determined through application of equilibrium equations adjusted for appropriate temperatures and ionic strength.

A seasonal cycle was demonstrated for the inorganic carbon species which was temporally correlated to the lake's thermal and productivity cycles. Vertical homogeneity in carbonate chemistry was evident during turnover periods while dramatic differences developed between the epilimnion and hypolimnion during winter and summer stratification. The lake was supersaturated throughout the year with H2CO*3, though saturation was approached during the productive summer months in the epilimnion. The epilimnion was supersaturated with respect to CaCO3, from the start of spring turnover to the end of autumn turnover. Calcium (Ca2+) levels within the epilimnion decreased through much of the same period. Dissolution of CaCO3 in the hypolimnion is indicated by increases in Ca2+ and alkalinity as stratification periods progress. Analysis of potentially influencing factors indicates that the seasonal trends were mostly a result of CO2 metabolism. This was further supported by concurrent algal biomass and 14C uptake.
Effect of temperature and sex on growth patterns in nymphs of the mayfly Hexagenia hilineata in the laboratory
Authors: WRIGHT L. L. , MATTICE J. S. , BEAUCHAMP J. J.
Published: May 2006

SUMMARY. Eggs collected from Hexagenia bilineata females were successfully reared in the laboratory at temperatures of 15, 20, 25 and 30°C. Eggs did not hatch at 10°C and although hatching was successful at 35°C, all nymphs at this temperature died while in early instars.

Survival of nymphs between the approximate size interval of 4–14 mm showed a significant decrease with increased temperatures. Nymphs at 15°C, however, generally did not survive transformation to the subaduit stage.

The growth pattern of individual nymphs was well described by a logistic curve at most temperatures. Furthermore, growth pattern was significantly affected by both temperature and sex.

Rate of development from oviposition to first emergence increased with increasing temperatures in a linear fashion between 15 and 30°C. The relationship was equally well described by a hyperbolic equation and a power‐law equation. By extrapolation from the hyperbolic equation, the lower threshold temperature for development was estimated to be 10.1°C3.1°C. The degree (°C)‐days required for development from oviposition to first emergence was calculated to be 2337 days with 95% confidence limits of 2045–2727 days under laboratory conditions.
A study of the dynamics of a natural population of the freshwater crayfish, Austropotamobius pallipes
Authors: BREWIS J. M. , BOWLER K.
Published: May 2006

SUMMARY. 1. Population size, survival and recruitment were estimated from mark—recapture data at frequent intervals.

2. Two types of mortality were identified: (1) moult‐associated—an intense but short duration mortality, and (2) overwinter mortality, which operated at a lower estimated weekly rate but over some 30 weeks.

3. Population size reached a mid‐summer peak as recruitment into the catchable size classes occurred. Thereafter numbers declined slowly to the end of the growth season, followed by an overwinter decline of some 50% of total.

4. Annual production was estimated at 196.5 kg wet wt ha−1 in 1977, 116.8 kg wet wt ha−1 in 1978 and 87.79 kg wet wt ha−1 in 1979.
Primary productivity studies during early years of West Point Reservoir, Alabama‐Georgia
Authors: BAYNE DAVID R. , LAWRENCE JOHN M. , McGUIRE JOHN A.
Published: May 2006

SUMMARY. 1. Phytoplankton density (organisms ml−1), standing crop (chlorophyll a mg m−2) and primary productivity (mg C m−2 d−1) were measured during years 2 (1976) to 5 (1979) after impoundment on West Point Lake.

2. West Point waters had low alkalinity (<0.4 meq 1–1) and low conductivity (<75 μs cm−1 at 20°C) but N and P concentrations typically exceeded those considered apt to cause nuisance blooms of algae. Abiogenic turbidity was normally higher in the upstream areas of the reservoir than in the downstream areas and was several times higher in winter‐spring than in summer‐autumn due to increased rains and runoff.

3. Primary productivity varied greatly both temporally and spatially. A mean value of 684 mg C m−2 d−1 was well within the mesotrophic range and did not approach the highly eutrophic state predicted. Productivity increased from a low of 550 mg C m−2 d−1 in 1976 to high of 763 mg Cm−2d−1 in 1979.

4. Observed variation in both chlorophyll a and primary productivity was more predictable in the cool (December‐March) than in the warm (June‐September) season and with plant nutrient data than without it. With plant nutrient data in the cool season 84% and 86% of the variation (R2) in chlorophyll a and productivity, respectively, were accounted for by the regression equations. During the warm season, with plant nutrient data, regression equations accounted for 44% and 68% of the variation in chlorophyll a and productivity, respectively. Higher R2 values in cool seasons resulted from the overriding influence of abiogenic turbidity on phytoplankton communities.
A new quantitative air‐lift sampler for collecting macroinvertebrates on stony bottoms in deep rivers
Authors: DRAKE C. M. , ELLIOTT J. M.
Published: May 2006

SUMMARY. 1. As three previous comparative studies of deep‐water samplers for benthic macroinvertebrates in rivers highlighted the need for a quantitative sampler for use on stony substrata, a new air‐lift sampler was developed. It can be operated from a small boat by two people, weighs 13.5–20.0 kg, depending on the length of riser used, and extends the maximum range of substrata that may be sampled quantitatively from 16–32 mm to 128—256 mm. The sampling area is isolated by forcing a collecting cylinder into the substratum, and rapid evacuation of the contents is assisted by a vibrator.

2. All the major specifications of the sampler were determined experimentally in a large tank using three sizes of substrata and plastic pellets to represent invertebrates. The sampler performed accurately to a depth of at least 8 cm on substrata ranging from gravel (2–4 mm) to large stones (32–36 mm long).

3. The performance of the sampler was compared with that of a Ponar grab and Pearson el at. air‐lift sampler at two sites on a large river and also with a Naturalist's dredge and a diver‐operated Hess‐Waters sampler at one of the sites where there were large stones up to 280 mm long. In terms of both mean taxa per sample and mean numbers m−2, samples taken using the new air‐lift sampler provided estimates comparable to or belter than those obtained with the other samplers.
Some factors regulating cohort production of the crayfish, Orconectes virilis
Authors: MOMOT WALTER T. , GOWING HOWARD
Published: May 2006

SUMMARY. Cohort production of the crayfish. Orconectes virilis, ranged from 148.8 to 70.2 kg in North Twin Lake (surface area 1.9 ha) and from 151.9 to 84.9 kg in West Lost Lake (surface area 1.4 ha). Both cohort production (P) and cohort mean biomass (B) showed a long‐term decrease with time. The cohort P/B ratios did not show such a trend but remained steady. The P/B ratio approximated the life cycle instantaneous rate of growth (G) which could then be used for estimating cohort production from mean biomass.

Production remained consistently higher in West Lost Lake. Analysis of horizontal life table data revealed no inherent difference between survival and fecundity rates of the crayfish population in each lake. Slight differences in basin morphometry between the two lakes determined nursery habitat availability and this affected recruitment of young from each female brood stock. Small differences in carrying capacity between two similar sized nearby lakes, along with a decrease in carrying capacity over time, were sufficient to nullify attempts to manage these populations using a maximum sustainable yield model.
A simplified 1,10‐phenanthroline technique suitable for the determination of dissolved iron in remote sources of water
Authors: WRIGHT R. C.
Published: May 2006

A simple technique is described for the determination of dissolved iron in water. It is useful for investigating remote sources and avoids errors due to post‐sampling precipitation of hydrated ferric oxides.

A small sample is added to a mixed 1.10‐phenanthroline‐i‐acetate buffer solution in the field and this‘developed sample” can then be stored for up to 4 weeks before the absorbancc value is read.
Chemical composition of water‐bodies in the English Lake District: relationships between chloride and other major ions related to solid geology, and a tentative budget for Windermere
Authors: SUTCLIFFE D. W. , CARRICK T. R.
Published: May 2006

SUMMARY.

Mean tarnwater concentrations of CI‐and other ions (Na+, K+, Ca2+, Mg2+, SO42‐+ NO3‐) decrease with increasing distance from the sea and altitude but are also related to solid geology. Lowest concentrations occur on slow‐weathering igneous rocks (Borrow‐dale Volcanics); minima of c. 100 μequiv. CI‐I‐1are similar to the volume‐weighted mean for bulk precipitation. At least 10–20% of Na+is leached from upland catchments, giving Na+/CI‐ratios greater than the equivalent ratio (0.86) in seawater and precipitation. Evapotranspiration at 20–30% annual rainfall accounts for CI‐concentrations in many tarns on igneous rocks but not all; some CI‐may be leached from the rocks in upland catchments and come from groundwaters at low altitudes near the sea. Sea‐spray has little influence on tarnwaters near the coast.

On sedimentary rocks overall mean CI‐concentrations are 27–73% higher than equivalent means on Borrowdale Volcanics; concentrations of other ions are also higher. A 5‐fold to 10‐fold range of CI‐concentrations is not simply due to increased evapotranspiration. Na+/CI‐ratios are < 0.86, especially on Skiddaw Slates where tarnwaters contain 10% or more excess CI‐balanced by Ca2+, apparently derived from groundwaters rich in CaCI2. On other sedimentary rocks (Silurian Slates and Carboniferous, Triassic and Permian series) tarn waters display a similar but less pronounced excess of CI‐and Ca2‐+relative to Na+. Some extra CI‐may be captured by dry deposition on vegetation but a portion, perhaps 15–30% of the total, apparently comes from the rocks or from groundwaters via deep aquifers in contact with seawater or connate water.

Anthropogenic sources on the catchments are also considered: deicing salt used on highways in winter accounts for a 27% increase of CI‐in Windermere South Basin over a 20‐year period.
The annual cycle of Simulium erythrocephalum (Diptera: Simuliidae) at a site in Norfolk
Authors: POST R. J.
Published: May 2006

SUMMARY. Size frequency distributions of larvae of Simulium erythrocephalum sampled regularly throughout 1978 from the River Tiffey at Carlton Forehoe, Norfolk, revealed five generations per year. The number of larval instars could be determined for the second and fifth generations, being six and seven respectively. Individuals of the overwintering generation were of larger ultimate size, had more ovarioles and apparently laid larger eggs than those of the summer generations. Females were larger than males throughout the year.
ATP as a biomass indicator in eight North Island Lakes, New Zealand
Authors: PRIDMORE R. D. , COOPER A. B. , HEWITT J. E.
Published: May 2006

SUMMARY. 1. The relationship between microbial ATP and biomass‐ carbon in the near surface waters (0.5–5 m) of eight New Zealand lakes was studied to determine the constancy of the carbon:ATP ratio under natural growth conditions. Concentrations of microbial carbon were estimated indirectly from cell volume determinations.

2. The carbon:ATP ratio remained reasonably constant (interquartile range 248–291, n= 50), except during periods of nitrogen/phosphorus deficiency when carbon: ATP ratios increased to values greater than 400.

3. During periods of nitrogen/phosphorus sufficiency, corresponding estimates of microbial ATP and biomass‐carbon were strongly correlated (r=0.97, n=47) and related by the equation carbon = (287±20) ATP‐(22±41) where carbon and ATP are expressed in mg m−3. From this relationship an average carbon:ATP ratio of 267 (SE=5) was calculated.

4. This ratio was not significantly affected by the relative proportions of bacterial and algal biomass in the surface water samples. However, because of the marked deviation of the carbon:ATP ratio during periods of nitrogen/phosphorus deficiency, the routine use of ATP as a biomass indicator is discouraged.
Use of ATP and carbon: nitrogen ratio as indicators of food quality of stream detritus
Authors: TAYLOR B. R. , ROFF J. C.
Published: May 2006

SUMMARY. 1. Differences in food quality of suspended and benthic organic detritus, as measured by ATP content and C/N ratio, were assessed along three contrasting headwater streams in southern Ontario.

2. Large differences in ATP content of sediments between cooler upstream reaches and warmer downstream reaches were detected. Sediment ATP content was highly correlated with stream temperature, presumably as a result of faster microbial growth, and with stream gradient. C/N ratios of sediments showed much the same pattern of differences as ATP, but were less variable.

3. By contrast, the ATP content (or BIOC/POM ratio) and C/N ratios of suspended organic matter showed no systematic variation between upstream and downstream or between warmer open and cooler shaded areas, probably due to the very short residence time of suspended particles.
The influence of seasonal and taxonomic factors on the ordination and classification of running‐water sites in Great Britain and on the prediction of their macro‐invertebrate communities
Authors: FURSE M. T. , MOSS D. , WRIGHT J. F. , ARMITAGE P. D.
Published: May 2006

SUMMARY. 1. Macro‐invertebrate samples were collected from 268 running‐water sites in Great Britain in each of three seasons (spring, summer and autumn). A combined seasons’treatment was generated by amalgamating the individual seasons’data. These four seasonal options were each subjected to four distinct taxonomic analyses differing in level of identification and whether the data were quantitative or qualitative. Thus sixteen data‐sets were available for analysis. Environmental data on physical and chemical variables, macrophyte cover and date of sampling were also recorded for each site.

2. All sixteen data‐sets were ordinated by detrended correspondence analysis and classified by two‐way indicator species analysis. There were strong correlations between the sixteen ordinations and significant concordance between classifications.

3. The relationships between ordination scores and single environmental variables were investigated. Muhiple discriminant analysis was used to fit environmental data to eight selected classifications covering the full range of seasonal and taxonomic treatments. The environmental variables most useful in distinguishing between rivers were substratum characteristics, alkalinity and total oxidized nitrogen. Within‐river differences were often highly correlated with discharge, distance from source, width and depth. Slope and altitude contributed strongly to both between‐river and within‐river distinctions.

4. Between‐site variation (beta diversity), eigenvalues of ordination, the reliability of classifications, the proportion of sites correctly assigned to their biological group using environmental data and the standardized similarity between observed and predicted fauna were all higher when identifications were taken to species level, rather than one of three family treatments. Qualitative data on a reduced list of families gave comparable or better results than more detailed family treatments.

5. Combined seasons’data enabled better categorization and prediction than single season's.

6. The values of the Czekanowski Index of Similarity between the observed and predicted fauna of test sites were close to realistic maximum values.

7. Recommendations are made concerning potential usages of the various classifications. The species level classification has uses in the field of conservation and in the prediction of biological response to environmental change. The family level classifications have value in developing local site inventories and in the interpretation of pollution surveillance programmes.
A seasonal sequence of diel distribution patterns for the planktonic dinoflagellate Ceratium hirundinella in a eutrophic lake
Authors: FREMPONG E.
Published: May 2006

SUMMARY. 1. Diel depth distribution patterns of Ceratium hirundinella were studied during eleven sampling periods, covering the seasonal growth cycle. They were shown to result from short‐term periodic or non‐periodic external factors, endogenous responses of the alga, and interactions between these.

2. Diel variations in wind stress resulted in the net transport of algae into or out of the sampling position due to lateral water movements. A progressive surface accumulation of Ceratium, leading to a 3‐fold increase in cell numbers at the sampling site over a 24 h period, was due to wind‐induced upwelling of deeper cells. Near‐surface accumulation of Ceratium on a completely overcast afternoon, similar to that associated with migrations, was attributable to advection.

3. Under sufficiently calm conditions, depth‐differentiation of Ceratium was regulated by its vertical swimming movements with a diel periodicity. Migration patterns observed in earlier work were confirmed and extended. The alga migrated towards the surface during the daytime and downward during the night; this rhythm had an endogenous component.

4. At high surface illumination, the alga retreated from the surface and formed discrete sub‐surface maxima; at low irradiance Ceratium showed positive phototaxis and concentrated near the surface. Under either condition of irradiance Ceratium actively aggregated at depths associated with irradiance levels of about 125–155 μEinsteins m −2 s −1. Downward movement was restricted by anoxic conditions and possibly by thermal/ density gradients. However, given sufficient light penetration, dissolved oxygen and nutrient availability, the thermal density gradient does not apparently eliminate downward movement by Ceratium.
Quantitative aspects of oxygen uptake by Gammarus (Crustacea, Amphipoda): a critical review
Authors: SUTCLIFFE D. W.
Published: May 2006

SUMMARY. Gill structure and function are brietly considered, as are the main factors affecting the oxygen content of water. The review deals with quantitative, analytical aspects of oxygen uptake related to body size, temperature, oxygen content of water, salinity, water velocity, substratum and activity of Cammarus. A theoretical model relates oxygen uptake to growth and life‐span of individuals. Several aspects of regression analysis, as applied to measurements of oxygen uptake, are examined and constructively criticized. The energetic cost of osmoregulation is calculated for G. pulex. The review concentrates on freshwater species of Gammarus but work on brackish‐marine species is also included. A more detailed summary and conclusions are given at the end of the review.
Haemoglobin synthesis in Daphnia magna Straus (Crustacea: Cladocera): ecological differentiation between neighbouring populations
Authors: CARVALHO GARY R.
Published: May 2006

SUMMARY. 1. Variations in the haemoglobin index of two neighbouring populations of Daphnia magna were recorded over a range of dissolved oxygen concentrations (0.5–4.0ml O2 1−1, 20°C). Reciprocal transfer experiments between habitats compared haemoglobin synthesis in situ.

2. An inverse relationship was found between the oxygen content of pond water and the haemoglobin indices of laboratory and natural populations.

3. Significant genetic differences in the synthesis of haemoglobin were found between the two populations. Animals from the poorly oxygenated habitat (0.8±0.18ml O2 1−1) had consistently higher haemoglobin contents (maximum HI, 87.7±4.5) at all experimental and in situ oxygen levels. D. magna from the well oxygenated pond (4.3±0.59 ml O21−1) had a lowered physiological ability to synthesize haemoglobin (maximum HI, 48.3±4.2). The process of ecological differentiation in Daphnia populations is discussed.
The invertebrate fauna of four macrophytes in a lotic system
Authors: ROOKE J. BRIAN
Published: May 2006

SUMMARY. 1. Invertebrates associated with four species of aquatic plants and on the adjacent substrate were investigated in a riffle/run section of a hard‐water stream.

2. Invertebrates were more numerous on stones than on any species of plant (> 17,000m−2 versus 1000–4000 m−2). Gatherers were more abundant on Ranunculus longirostris, where proportionally more fine detritus was trapped in the leaf bundles than on other plants. Scrapers were most numerous on Charu vulgaris, where attached diatoms were also most prevalent.

3. Invertebrate community structure on three plant speeies was quite different from that on stones. This was not the case for Potamogeton amplifolius which appeared to be used by the organisms as a mere extension of the substrate.
Seasonal and comparative aspects of chemical stratification in some tropical crater lakes, Ethiopia
Authors: WOOD R. B. , BAXTER R. M. , PROSSER M. V.
Published: May 2006

SUMMARY. 1. Measurements of oxygen, pH, phosphate, nitrate, nitrite, hydroxylamine. ammonium and sulphide were made in four Ethiopian crater lakes during 1964, 1965 and 1966 at fairly regular intervals. The seasonal pattern of the dynamics of these chemical constituents is described for depth and time and relates closely to the pattern of thermal stratification and mixing previously described.

2. Interactions between the chemical constituents are examined and comparisons are made between the four lakes which differ widely in their depth, exposure to wind and standing crops of phytoplankton.

3. The vertical distribution of the chemical constituents is used to help define the limits of circulation of surface waters and the need to understand the seasonality of chemical stratification in relating climatic, morphometric and biological events, especially in tropical lakes, is stressed.
Nitrate respiration by Protozoa (Loxodes spp.) in the hypolimnetic nitrite maximum of a productive freshwater pond
Authors: FINLAY B. J.
Published: May 2006

SUMMARY.

The ciliated protozoon Loxodes dominated the microfaunal community living in the anoxic hypolimnion of Priest Pot, a small productive pond. Its peak abundance close to the oxic‐anoxic boundary was always associated with a peak in nitrite (NO2) concentration. Both peaks were usually found in water containing μ1 μmol O2 1‐1.

The microfauna were concentrated on a 30 μim sieve. The number of Loxodes in the sieve retentate correlated well with the activity of nitrate reductase in the same material, implying that the enzyme was located in Loxodes. It is unlikely that residual bacterial contamination could have accounted for the activity.

A doubling of specific electron transport system activity was associated with the transition across the oxic–anoxic boundary. This is consistent with the switch to nitrate respiration and the lower energy yield it provides.

Dissimilatory nitrate reduction was deduced to be the source of the nitrite peak. Nitrate was supplied by both run‐off and nitrification.

It is suggested that Loxodes participates in the dissimilatory sequence of a condensed nitrogen cycle functioning across the oxic—anoxic boundary.
Structure and grazing of stone surface organic layers in some acid streams of southern England
Authors: WINTERBOURN MICHAEL J. , HILDREW ALAN G. , BOX ALAN
Published: May 2006

SUMMARY.

Stone surface organic layers were investigated at five sites on small, acid streams in the Ashdown Forest, southern England. Sites differed in stream water pH (means 4.3–6.6) and some other physicochemical features.

Organic layers at the stream bed surface differed between sites in structure and in the amount of organic carbon present. Algae were abundant at the sites with higher conductivity and pH, iron bacteria (mainly Leptothrix sp.) predominated in the iron‐rich Broadstone stream, whereas the surface layer at the most acid site was predominantly a rather structure less organic film with few living organisms.

Amounts of organic carbon on stones buried within the stream bed for 3 months were almost identical at all sites. When viewed with the scanning electron microscope (SEM), organic layers on buried stones were rather structure less with some amorphous, floceulent material. The paucity of microflora suggests that these layers may have been formed primarily by abiotic mechanisms.

X‐ray microanalysis of organic layers indicated that complexes of organic matter with the metals iron, aluminium and manganese were present.

Laboratory experiments with seven species of invertebrates showed that all were able to remove and at least partially ingest organic layers and underlying sandstone. The weight of material removed was highest on microbially impoverished layers from the most acid site, and was substantially lower where algae were abundant.

6. The role of stone surface organic layers in stream systems is discussed. They may be important sites of dissolved organic matter (DOM) uptake and transfer to the benthos. A major impact of acidity on running water could be through its effect on the structure and function of organic layers.
The forces on microorganisms at surfaces in flowing water
Authors: SILVESTER N. R. , SLEIGH M. A.
Published: May 2006

SUMMARY.

Surfaces in flowing water are covered by boundary layers within which the velocity of flow ranges between zero at the surface and the velocity of the main stream at the limits of the boundary layer.

Many organisms are small enough to live entirely within the boundary layer and so are subjected to much smaller drag forces than if they were exposed to the main stream velocity.

The form and extent of boundary layers at different stream velocities around selected structures, representing leaves and stems, have been calculated and presented graphically.

These data provide a basis for the estimation of shear stresses on substrate surfaces and of forces exerted upon organisms of different sizes that live within the boundary layers around such surfaces, when exposed to different current velocities. Values for shear stresses on bacteria calculated in this way lie within the range of shear stresses required to detach bacteria from surfaces experimentally.
Environmental cues for cyclomorphosis in Daphnia retrocurva Forbes
Authors: HAVEL JOHN E. , DODSON STANLEY I.
Published: May 2006

SUMMARY.

The invertebrate predators. Chaohorus, Leptodora, Hydra, Utricularia, and cyclopoid copepods were ineffective as inducers of high helmets in laboratory reared Daphnia retrocurva. Lako water from different sources, when used as culture medium, was also ineffective.

High helmets were induced when clones were grown under warm and turbulent conditions. Presence or absence of illumination and varying photoperiod did not affect helmet growth in warm turbulent cultures. Different clones grown under warm turbulent conditions differed in their responsiveness to the treatment, but no relationship between helmet size in clones and helmet size in the field on the dates of clone isolation was demonstrated. Laboratory‐induced phenotypes were rarely as extreme as those of field animals.