bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations and experiments on the phytoplankton of Blelham Tarn, English Lake District
Authors: LACK T. J. , LUND J. W. G. 
Published: May 2006

SummaryTubes composed of butyl rubber have been placed in a small English lake in an area where the water is 11‐12 m deep. Each tube, when fully distended, contains over 18 000 m3 of water. The tubes are anchored to the shore and lake bottom. A boat can be rowed into them over a specially strengthened portion ofthe margin. The first was installed and its water isolated from that in the lake by the end of July 1970 and the second tube at the beginning of October 1970. The installation, maintenance, and performance of the tubes are described; as are suggested improvements. The temperature regime in the tubes closely follows that in the lake. If the chemical conditions are favourable, the seasonal cycle of Melosira in a tube is similar to that n i the lake. Contamination of the water in the tubes by that in the lake is slight and has a negligible effect on chemical conditions within them. Water can be lost from the tubes under certain conditions. The reverse does not happen. The phytoplankton communities in the tubes are similar in quality to those ofthe lake, even after 2‐5 years of separation. The evidence suggests that the tubes are suitable for investigations on certain factors determining the abundance and seasonal cycles of algae in lakes and for other limnological studies.
Studies of tolerance to heavy metals in the flora of the rivers Ystwyth and Clarach, Wales
Authors: McLEAN R. O. , JONES A. K. 
Published: May 2006

SummaryA survey of the river Ystwyth demonstrated that it was polluted with metals especially below the areas of old lead mines. Hormidium spp. Kütz in particular Hormidium rivulare Kütz were the most tolerant filamentous green algae present. Scapania undulata (L.) Dum. was a tolerant bryophyte on the Ystwyth and Clarach rivers and was found alone in polluted sites, but was less frequent in cleaner areas. Metal extracts of this bryophyte mirrored the variation in metal concentrations of the environment to some extent. In general, lower levels of Fe, Pb and Mn were found in Scapania as compared with the less tolerant Fontinalis squamosa Hëdw. When the latter was transplanted to polluted sites an increase in its Pb, Cu, Zn and Mn content occurred within 6 weeks and the plant started to die and decay after 18 weeks. Scapania survived when it was transplanted from its natural polluted habitat to a less polluted area, and there was no marked change in its metal content. Zn65 tracing experiments, in the laboratory, demonstrated that both plants had similar uptake patterns for the metal, but that the amount taken up was slightly higher in the less tolerant Fontinalis. There was no change in the number of diatoms found upon Scapania when it was transplanted, but a reduction in numbers occurred on the transplanted Fontinalis when it started dying. The composition of these diatom floras was different in polluted sites as compared to that in the cleaner areas.
The effect of pH on the population growth of three species of duckweed: Spirodela oligorrhiza, Lemna minor and Wolffia arrhiza
Authors: McLAY C. L. 
Published: May 2006

SummaryThree species of duckweed, Spirodela oligorrhiza, Lemna minor and Wolffia arrhiza were grown under aseptic conditions on both buffered and unbuffered solutions of Jacob's media. Media with manually regulated pH levels were also used.Growth on unbuffered media is initially rapid but eventually inhibited, probably by increased pH levels. On buffered media growth is poor and effects of buffers cannot be separated out. These media give inadequate pictures of the species’ responses to changes in pH.Growth is most successful on media with regulated pH where sustained logarithmic population increases were achieved. Spirodela and Lemna rates are symmetrical about an almost neutral, optimal pH, declining fairly rapidly away from the optimum. Wolffia has an optimum at pH 5 and growth declined with increasing pH. All three species have optima at, or below, the neutral point.The range of tolerance of duckweeds is broader than has previously been suspected. Estimated lower limits, optimum and upper limits for each species are: Wolffia, pH 4·5–0·10, Lemna pH 4–6·2–10, Spirodela pH 3·7–0·10.Growth rate along a pH gradient is best described by means of polynomial equations: second‐degree equations are sufficient for Spirodela and Lemna but a fifth‐degree equation is required for Wolffia. Rates of population growth are similar for all species. In decreasing order they are: Wolffia, Lemna, Spirodela. However, in biomass units Lemna grew more than six and Spirodela seventeen times faster than Wolffia.
The occurrence and distribution of actinomycetes in lakes of the English Lake District
Authors: JOHNSTON D. W. , CROSS T. 
Published: May 2006

SummaryInvestigation of the occurrence of mesophilic actinomycetes in the lakes of the English Lake District revealed their widespread distribution in the lacustrine environment. Although only low numbers of actinomycetes occurred in the water, high numbers were recovered from all the lake muds. Total numbers of actinomycetes in the muds correlated quite well with the lakes’ productivity status. High numbers of Micro‐monospora, Streptomyces and nocardioform actinomycetes were isolated from all the lakes sampled. Low numbers of Streptosporangium were isolated from all the muds but strains of Actinomadura, Actinoplanes, Dactylosporangium, Microbispora and Thermomonospora were only encountered occasionally. Micromonospora was the numerically dominant genus isolated from all the lakes sampled. This dominance was even more striking in deeper layers of mud and this was thought to reflect a more resistant spore stage in Micromonospora than in either of the other two main genera.
The seasonal pattern of thermal characteristics of four of the Bishoftu crater lakes, Ethiopia
Authors: WOOD R. B. , PROSSER M. V. , BAXTER R. M. 
Published: May 2006

SummaryMeasurements of temperature/depth profiles in four Ethiopian crater lakes were made during 1964, 1965 and 1966 at fairly regular intervals. Several more intensive diurnal studies, with observations at 3‐h intervals during periods of about 48 h, were also carried out. Results show a pattern of heating leading to thermal stratification from February to September and cooling from September to December with possible overturn at the end of that period. Thermal stability was never great and thermoclines were often poorly defined and multiple. Net daily changes in heat content during both heating and cooling can be a small fraction (c. 3%) of the diurnal heat flux and depend upon the relative magnitudes of solar radiation and evaporative heat loss. These are such that cooling may occur during periods of highest solar input and vice versa. However, meteorological conditions could easily reverse the cooling process before the December overturn so that complete mixing is by no means a predictably regular annual event.
The interaction of components controlling net phytoplankton photosynthesis in a well‐mixed lake (Lough Neagh, Northern Ireland)
Authors: JEWSON D. H. 
Published: May 2006

SummaryThe 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 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.
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.
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.