bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between metal concentrations and organism size in aquatic insects
Authors: SMOCK LEONARD A.
Published: May 2006

SUMMARY.

The influence of organism size on whole‐body metal concentrations of eight metals was examined in aquatic insects in field and laboratory studies. Information on the partitioning of metals between adsorbed, absorbed and gut content material was also obtained.

For Co, Cr, Fe, Sb and Sc, an exponential decrease in concentration with increasing organism size was observed, indicating surface adsorption as an important mode of metal accumulation.

No, or only a slight, concentration‐size relationship was found for K, Mn and Na. This is expected for metals with high absorption efficiencies and a low capacity to be adsorbed.

Clearing of the gut of the mayfly Stenonema modestum (Ephemeroptera: Heptageniidae) did not significantly after the concentration size relationship for any of the metals studied.

Studies of Cr uptake with Stenacron interpunctatum (Ephemeroptera: Heptageniidae) indicate that the concentration‐size relationship is not affected by variability in the concentration of available Cr.

About 52% of the whole‐body burden of Cr in S. interpunctatum was associated with gut material while at least 33% was adsorbed to the organism's exoskeleton and at most 15% was internally absorbed.
Habitat exploitation by larvae of Amphipsyche meridiana (Trichoptera: Hydropsychidae) in a Javanese lake outlet
Authors: BOON P. J.
Published: May 2006

SUMMARY. 1. Trichopteran populations below a dam on the River Tuntang (Central Java) and on intake screens above the dam consisted almost exclusively of Amphipsyche meridiana. Larvae on dam screens were in tightly packed aggregations, with greater densities in deeper water, and were predominantly fourth or fifth instars during the period of observation. Below the dam, 40% of larvae were in the first three instars. Larvae at the dam screens were heavier and yielded larger emerging adults which contained more eggs per female.

2. Mean net mesh sizes of fifth instar larvae varied greatly from 34×26 μm to 125×106 μm with larger meshes having progressively thicker strands. It is suggested that larger mesh size may be positively correlated with faster flow rates. The dinoflagellate Peridinium, commonly found in the guts of larvae below the dam, was virtually absent in dam screen larvae, possibly due to mesh size differences.

3. The behaviour of larvae in aggregations was observed in a laboratory flow channel. After experimental destruction of feeding nets, larvae immediately ingested silk prior to the construction of a new net. Nets were spun in a‘figure 8’fashion, and took between 11 and 30 min to complete. Stridulation between larvae occurred frequently and may be related to the defence of silk reserves within territories.
Movements of marsh‐dwelling invertebrates
Authors: CORKUM LYNDA D.
Published: May 2006

SUMMARY. 1. Invertebrate movement was monitored in a parkland marsh in central Alberta, Canada, for 24 h periods every 2 weeks during the ice‐free season. Stationary plankton nets captured organisms moving towards or away from shore.

2. Movement occurred throughout the sampling programme, particularly during the warm summer months. Most organisms were night active and exhibited directional movements. Hyalella azteca (Saussure) and Caenis simulans McDunnough constituted most of the catch.

3. Although there was a significant positive seasonal relationship between maximum water temperature and total numbers of animals captured. no physical factor appeared to control movement on a daily basis.
Ecology and behaviour of a free‐swimming tube‐dwelling rotifer Cephalodellaforficula
Authors: DODSON STANLEY I.
Published: May 2006

SUMMARY. 1. Cephalodella for ficula (Ploima, Rotifera) lives in tubes it constructs itself. These tubes are built of mueus in detritus‐rich environments. The tubes are often closed at both ends, arc not used as sieves, and are not eaten directly.

2. The rotifer swims back and forth in its tube and apparently lives on bacteria which are shed from the inner walls of the tubes. Because of surface‐to‐volume considerations, this feeding strategy is probably only possible for animals smaller than roughly 1 mm. Under low food conditions, rotifers inside a tube have a distinctly higher fitness than rotifers removed from their tube.

3. Given high food conditions, rotifers removed from a tube immediately build another. Grazing on particles outside the tube appears to take place when a tube is being lengthened. Rotifers do not leave the tube for routine feeding, but under conditions of starvation or very low oxygen concentration they will leave the tube and swim about.
Hypolimnetic phosphorus retrieval by diel vertical migrations of lake phytoplankton
Authors: SALONEN K. , JONES R. I. , ARVOLA L.
Published: May 2006

SUMMARY. I. Movement of 33P from hypolimnion to epilimnion in a small, dystrophic lake was investigated using small‐diameter experimental tubes enclosing thermally stratified water columns. This approach was made possible by the extremely sharp stratification found in such lakes, in which the euphotic zone closely coincides with the epilimnion.

2. The vertical distribution of inorganic phosphorus in the lake showed a sharp increase across the thermocline so that enhanced concentrations were available to phytoplankton just below the thermocline. Inorganic nitrogen concentrations did not show such a marked relation to thermal stratification.

3. One abundant motile alga (Cryptomonas marssonii) showed striking and regular vertical migrations in the lake, moving below the thermocline at night and returning to the surface waters in early morning. These migrations took cells across a 10°C temperature gradient. Non‐motile phytoplankton showed constant vertical distributions.

4. In the experimental tubes an upward movement of phosphorus took place from hypolimnion to epilimnion which was only attributable to transport by phytoplankton cells undertaking active vertical migrations. No equivalent movement of phosphorus occurred in control tubes from which algae were absent.

5. The possible significance of such nutrient retrieval is discussed with reference to plankton phosphorus budgets and competition between phytoplankton species.
Major ion and carbonate system chemistry of a navigable freshwater canal
Authors: HOWARD J. R. , SKIRROW G. , HOUSE W. A.
Published: May 2006

SUMMARY. 1. An examination has been made of the water quality of a 50 km (Wigan to Litherland) length of the Leeds‐Liverpool canal. Regular in situ measurements accompanied by sampling for laboratory analysis were made at seventeen stations over a 15‐month period.

2. Three principal contributory water types have been recognized, and the observations have allowed estimates to be made of their relative contributions to the total water flux in the lower reaches of the system. Linear flow rates (c. 0.6 km day−1 near Litherland) are consistent with previous reports.

3. The combined field and laboratory measurements have been used to obtain estimates of the partial pressure of CO2 in the water (P co2), the degree of saturation of the water with respect to calcite (Ω) and the major ion speciation in the water. Because of the variable ionic compositions of the waters examined, these estimates were made using a program (WATEQ) which took account of ion‐pairing.

4. Diurnal and annual cycles with respect to pH, P co2 and ω occur, these being most marked in the lower parts of the study length when, for a large proportion of the spring and summer, P co2 was below the atmospheric level and noticeable supersaturation with respect to calcite occurred. In contrast, two of the contributory water types, the River Douglas input and the Creek, showed low pH and Ω values and high P co2 values throughout the year.
Laboratory and field experiments on the feeding ecology of the cyclopoid copepod, Mesocyclops edax
Authors: WIUJAMSON CRAIG E.
Published: May 2006

SUMMARY. 1. Gut contents of Mesocyclops edax consisted of rotifers. cladocerans, copepods and algae, the importance of each varying seasonally.

2. Functional response experiments using two soft‐bodied rotifers as prey showed an increase in ingestion rate with increasing prey density up to a threshold, followed by a decline.

3. Enclosure experiments with natural assemblages of prey from two lakes indicated that Mesocyclops edax is a selective feeder and may ingest fifty or more prey per predator per day, accounting for up to 17% of the standing crop of its preferred prey species per day in nature.
Downstream increase in the abundance and heterotrophic activity of suspended bacteria in an intermittent calcareous headstream
Authors: GOULDER R.
Published: May 2006

SUMMARY. 1. Concentration of total bacteria, and heterotrophic activity (as turnover rate for glucose assimilation), in the water of an intermittent spring‐fed calcareous headstream, increased with distance from the source to 1600 m.

2. This increase was gradual rather than stepwise and might be due to release of bacteria from submerged vegetation and the stream bed, and to input of terrestrial bacteria with groundwater.

3. The increment per unit length of stream was greatest in summer when aquatic vegetation was most abundant and discharge was low.

4. When the stream was partly dry, isolated peaks of suspended bacteria occurred and there was no regular downstream increase.

5. A lesser spring which upwelled into a natural basin consistently contained more suspended bacteria than the principal source, which was an artificial culvert.
Spine development in the rotifer Keratella cochlearis: induction by cyclopoid copepods and Asplanchna
Authors: STEMBERGER R. S. , GILBERT J. J.
Published: May 2006

SUMMARY. 1. Spine development in a clone of unspined Keratella cochlearis was promoted by a water soluble factor released by the copepods Tropocyclops prasinus and Mesocyclops edax and by the predatory rotifer Asplanchna priodonta. Between 9 and 55% of K. cochlearis populations cultured in predator‐conditioned media responded to the inducing chemical.

2. The K. cochlearis form possessing a posterior spine of medium length was much less susceptible to predation by small Tropocylops and Asplanchna than the form lacking the posterior spine. These predators consistently selected the unspined form over the spined form when offered equal densities of each. However, both spined and unspined forms were equally susceptible to predation by large Mesocyclops.

3. The phenotypic variation of offspring produced from induced unspined Keratella females encompassed much of the variation reported for the taxon in North America. These morphotypes are similar to the variation of forms reported for the K. cochlearis tecta series known from Europe. We suggest that the North American morphotypes be identified in studies of this species because the presence of the posterior spine can greatly affect predator selectivity.
Particulates and the cycling of lead in Ullswater, Cumbria
Authors: EVERARD MARK , DENNY PATRICK
Published: May 2006

SUMMARY.

Ullswater has been affected by former lead mining in the catchment area. This paper investigates how lead in the lake is re‐distributed within the littoral zones. Concentrations in the lake water are low. Particulates including phytoplankton, seston and gelatinous ooze overlying lead‐enriched sediments can have values from 1.3 to >6.0 and 26 mg Pb g‐1 dry weight respectively.

During turbulent conditions, contaminated phytoplankton, settled algae and some of the gelatinous ooze are brought into near‐homogenous suspension within the water column. In calm conditions, settlement of particulates occurs and a rate‐zonal distribution results such that, in a vertical column of water, the finer particles in the upper layers have lower concentrations of lead per unit volume of water than the lower layers.

In non‐turbulent conditions the particles which settle on all submerged surfaces form a tenuous layer termed ecton. Aufwuchs becomes coated by ecton but the latter is readily re‐suspended by disturbances. The intimate contact, and the similarity of concentrations of lead in Aufivuchs and ecton from any one sample, suggests that metal flux occurs between the two. It is concluded that the variety of particulates which comprise the ecton distribute lead during turbulence. In calm conditions the ecton settles on all submerged surfaces and provides a mechanism for transfer of lead into the littoral food web.
The production of hemoglobin by small pond Daphnia pulex: intraspecific variation and its relation to habitat
Authors: ENGLE DIANA L.
Published: May 2006

SUMMARY.

Hemoglobin production was measured for two populations of Daphnia pulex, one from a temporary pond (GR Pond) and one from a permanent pond (Rash Pond). Surface water in Rash Pond remains high in oxygen, while by late summer very little oxygen remains in GR Pond. Hemoglobin synthesis was induced in the laboratory by artificial oxygen deficiency.

Reproductive state influenced the level of hemoglobin in Daphnia. Females with parthenogenesis eggs had higher total body hemoglobin than ephippial females. Clutches laid by pale Daphnia immediately before exposure to low oxygen conditions were aborted. Offspring produced by hemoglobin‐rich females later in the treatment survived.

Hemoglobin production was higher for Rash Pond Daphnia. Visual predators exist in GR Pond, but are absent in Rash Pond. Also, Daphnia are smaller in GR Pond. Visual predation may have selected against high levels of hemoglobin in the temporary pond. Thus oxygen availability in nature is not necessarily a good predictor of hemoglobin production by Daphnia.

Feeding behavior was altered in low oxygen conditions. Browsing was dominant in low oxygen treatments while Daphnia in control treatments filtered algae normally. Browsing may increase access to sedimented iron necessary for hemoglobin synthesis.
Rates of ammonia release from sediments by chironomid larvae
Authors: TÁTRAI ISTVÁN
Published: May 2006

SUMMARY. 1. Microcosms of Lake Balaton mud and sterilized sand and aerated water were used to evaluate ammonia increments in the overlying water as influenced by chironomid density and temperature. In the two approaches, the effects of sediment disturbance and metabolic excretion of chironomids were measured.

2. The activity of larvae increased the ammonia content of the overlying water at temperatures above 10°C. A rise of temperature to 20°C resulted in a 5–20‐fold increase in ammonia release in both systems with chironomids.

3. At 10°C combined effects of sediment disturbance and of excretion produced lower release rates than did excretion rates alone (mud‐water v. sand‐water treatments). At higher temperatures (15 and 20°C) release rates of ammonia by sediment disturbance plus excretion were higher than excretion rates alone. Ammonia excretion contributed significantly to the total release at each temperature.

4. Metabolic mineralization of nitrogen compounds appears to be an important mechanism contributing to nitrogen regeneration from aerobic lake sediments. High N:P ratio (14:1) of chironomid excretion materials supports this interpretation.
Advective effects of a reservoir flood on zooplankton abundance and dispersion
Authors: DIRNBERGER JOSEPH M. , THRELKELD STEPHEN T.
Published: May 2006

SUMMARY. 1. The diel vertical distribution and abundance of zooplankton in the Red River arm of Lake Texoma, Oklahoma‐Texas, U.S.A., were examined between 25 January and 26 June 1982.

2. During periods of low river inflow, zooplankton vertical patchiness was related to wind stress. Zooplankton did not maintain distinct vertical patches under strong mixing.

3. In mid May heavy rainfall in the drainage basin increased discharge from the Red River and reduced water retention time in the reservoir. The Red River water mass entered the lake as a turbid, surface overflow plume. During this period of flooding most zooplankton populations declined and the distributions of remaining individuals deepened. Greatest population losses occurred between 0 and 7m, depths where most zooplankton had been concentrated prior to the flood.

4. A model of population dynamics based on depth specific rates of water exchange between the lake and the Red River, estimated from conductivity changes through time, accounted for the general pattern of change in zooplankton abundance and vertical dispersion.
The life history of the minnow Phoxinus phoxinus (L.) in a productive stream
Authors: MILLS CHRIS A.
Published: May 2006

SUMMARY. 1. In the River Frome, Dorset, this small cyprinid spawned from mid‐April to early August and consequently some 0 group minnows did not develop scales until the following spring.

2. Most I group fish formed a summer hyaline band on their otoliths in a edition to the normal winter band.

3. Life‐span was short with a winter age‐structure of 67% 0 group, 32% I group and 1% II group fish with mean fork lengths of 29, 55 and 73 mm respectively.

4. In June, substantial numbers of I group fish reached reproductive size (50mm) and thereafter progressively replaced II group fish in the spawning shoals. Few II group males survived beyond June, few females beyond August.

5. Only half of I group minnows reached matutity. These were usually fish which had reached 30mm by the previous winter. Very few of these large I group fish survived to spawn the following year.

6. This differential mortality, together with the loss of condition and disappearance of II group fish during spawning, may indicate the cost of an extended high level of reproductive effort.

7. In this productive environment the life history of the minnow more closely resembles that of the small sympatric species Cottus gobio and Noemacheilus harhatulus than it does that of sympatric cyprinids.
Colonization of rivers and canals in Great Britain by Dugesia tigrina(Girard) (Platyhelminthes: Tricladida)
Authors: WRIGHT J. F.
Published: May 2006

SUMMARY. 1. Prior to 1975 Dugesia tigrina, an Americati immigrant triclad, was known from only a few flowing water sites in Great Britain. Since then it has been found in a large number of lowland rivers and canals in England and Wales, and in 1985 it was reported from the lower reaches of the River Tweed in Scotland.

2. This note gives the recorded distribution of D. tigrina up to the end of 1985 (115 10 km squares now occupied) and summarizes the environmental conditions at a subset of twenty‐five sites where D. tigrina occurs.

3. Information on the native triclads at sites recently colonized by D. tigrina is used as a basis for speculating on the rivers most vulnerable to the future spread of this species.

4. Possible methods of dispersal of D. tigrina and the features which make it a successful colonist are discussed.
Population dynamics and production of Sialis lutaria L. (Megaloptera) in the Danish River Suså
Authors: MOTHIVERSEN TORBEN , THORUP JENS
Published: May 2006

SUMMARY. 1. Populations of Stalls lutaria L. were sampled quantitatively at about monthly intervals during 3 years at two localities in the macrophyte rich River Suså, Denmark.

2. The life cycle was univoltine. The larvae hatched in June‐July, and the initial S. lutaria population densities varied between 10 and 370 ind. m−2. These differences were probably due to extreme variations in stream discharge during the period of recruitment, high velocities preventing the small swimming larvae from reaching the sediment.

3. The S. lutaria rate of elimination varied between 0.11 and 1.47% d−1at the two localities. The high rate of elimination was possibly due to fish predation.

4. The growth rates varied between 0.54 and 15% d−1. Growth rates differed between localities and years.

5. Numbers of potential prey organisms were not higher in sample units with S. lutaria than in sample units without S. lutaria. Numbers of leeches, which were potential competitors, did not differ significantly in sample units with and without S. lutaria.

6. Production of S. lutaria varied between 0.16 and 2.49 g ash free dry weight m−2 y−1, and the P/B̄ ratios varied between 3.0 and 7.3 y−1. The P/B̄ ratios increased significantly with increasing rate of elimination.
Seasonal variation in diet of Chironomus plumosus (L.) and C. anthracinus Zett. (Diptera: Chironomidae) in mesotrophic Lake Erken
Authors: JOHNSON RICHARD K.
Published: May 2006

SUMMARY. 1. Microscopic gut content analysis of Chironomus plumosus (L.) and C. anthracinus Zett. collected from 18m depth in mesotrophic Lake Erken. revealed significant seasonal differences between the two species.

2. C. plumosus dietary constituents showed greater seasonal variation than those of C. anthracinus, with diatom contribution to the gut contents reflecting temporal changes in the phytoplankton.

3. Overall the percentage of gut content constituted by detritus, algae, animal remains, and inorganic matter averaged 96%, 4%, 0.4% and 0.03% for C. plurnosus and 97%, 3%, 0.6% and 0.03% for C. anthracinus.

4. Coefficients ot dietary overlap for non‐detrital foods decreased markedly from August to September. During this period the proportion of centric diatoms in the guts of C. plumosus increased by 94% while no marked changes were noted in C. anthracinus.

5. C. ptttmosus ingested more diatoms than C. anthracinus, especially during diatom blooms in spring and autumn. These results are consistent with the known differences in feeding behaviour between these two speeies.
The ordination and classification of macroinvertebrate assemblages in the catchment of the River Wye in relation to environmental factors
Authors: ORMEROD S. J. , EDWARDS R. W.
Published: May 2006

SUMMARY. 1. Macroinvertebrates were sampled from three habitats at forty‐five sites in the catchment of the Welsh River Wye. Species assemblages were ordinated by DECORANA. classified by TWIN‐SPAN and related to physico‐chemical factors using correlation and multiple discriminant analysis respectively.

2. DECORANA axis 1 was correlated with pH or total hardness, whilst axis 2 correlated with slope or distance from source. TWINSPAN groupings were also related to hardness and, to a lesser extent, slope. Assemblages at soft‐water sites (<15gm−3 CaCO3) were composed mostly of Plecoptera but at hard‐water sites, even at high slope (>10 m km−1), the fauna was dominated numerically by Ephemerop‐tera, net‐spinning Trichoptera, Mollusca and Crustacea.

3. We suggest that our data do not support the River Continuum Concept unless there are modifications to allow for multiple gradients.
Seasonal variation in the filament morphology of the freshwater diatom Melosiragranulata(Ehrenb.) Ralfs
Authors: DAVEY MARTIN C.
Published: May 2006

SUMMARY 1, The seasonal changes in filament dimensions and the occurrence of separation valves in a population of Melosira granulata(Ehrenb.) Ralfs were investigated in a eutrophic lake in southern England. Experiments were carried out in culture to study the effects of various environmental factors on the diatom's morphology.

2. Major blooms of M. granulataoccurred from September to October, coinciding with an increase in mean filament length brought about by the high growth rate of the diatom. This increase was controlled by a reduction in the frequency of separation valve production. A similar increase in filament length occurred in rapidly growing cultures.

3. The population was lost from the epilimnion when thermal stratification occurred. Immediately prior to this the population consisted of short filaments.

4. The mean filament length was greatest during occasional summer blooms and was again controlled by a reduction in the frequency of separation valve production. This appeared to be a response to the reduced nutrient concentration in the lake. This is supported by similar morphological changes in low nutrient cultures.

5. Increases in the filament length of the diatom were accompanied by increases in the diatom's sinking velocity. The length increase thus ensured its rapid return to the sediment, after summer growth periods, where the cells could be replenished with nutrients.
Book Reviews
Authors: VINER A. B.
Published: May 2006

Book Review in this Article:

Paine, A.I.(1986) The Ecology of Tropical Lakes and Rivers.

John, D.M. (1986) The Inland Waters of Tropical West Africa

Smart, M.M., Lubinski, K.S. & Schnick, R.A. (Eds) (1986) Ecological Perspectives of the Upper Mississippi River

Skreslet, S. (Ed.) (1986) The Role of Freshwater Outflow in Coastal Marine Ecosystems

Kristiansen, J. & Andersen, R.A. (1986) Chry‐ sophytes: Aspects atid Problerrts.

Munawar, M. & Tailing, J.F. (Eds) (1986) Seasonality of Freshwater Phytoplankton: a Global Perspective—Developments in Hydrobiology

Neboiss, A. (1986) Atlas of Trichoptera of the SW Pacific‐Australian Region

Reuss, J.O. & Johnson, D.W. (1986) Acid Deposition and the Acidification of Soils and Waters

Davies, B.R. & Walker, K.F. (Eds) (1986) The Ecology of River Systems

Rowland, A.P. (Ed.) (1987) Chemical Analysis in Environmental Research

Shaw, S.A. & Muir, J.F. (1987) Salmon: Economics and Marketing
Late Holocene flooding in the Ecuadorian rain forest
Authors: FROST IAN , MILLER MIKE C.
Published: May 2006

SUMMARY 1. The stratigraphy, radiocarbon chronology, sedimentary pigment, and cation records of sediment cores from four lakes in the Ecuadorian rain forest show that regional flooding occurred from about 1300 to 800 ‘BP. Each core contains a stratum of alluvial clay, silt and sand overlain by lacustrine deposits of peat, gyttja or clayey gyttja. Radiocarbon dates show that the onset and termination of the alluvial event was synchronous across the sites. Short‐term, possibly regional, flooding occurred at each of the sites at least once since the major flood.

2. A core from Anangucocha, a black‐water lake, records the geoche‐ mical signature of white‐water incursion during this flooding interval. Sedimentary pigments show that aquatic production at Anañgucocha was low during the lotic interval but rose sharply and remained high within the modern lake period.

3. The Amazon's dynamic river system may have been an important force in promoting and maintaining high floral and faunal diversity.
The effects of water depth and density on the growth of a unionid clam*
Authors: HANSON JOHN MARK , MACKAY WILLIAM C. , PREPAS E. E.
Published: May 2006

SUMMARY. 1. Unionid clams from Narrow Lake, Alberta, were collected to quantify the natural variation in growth, to assess the natural variation in abundance, age and size distribution, and growth with water depth in the lake, and to conduct in situ experiments to directly test the effects of water depth (temperature) and clam abundance on clam growth.

2. The unionid clam, Anodonta grandis simpsoniana, showed wide variation in length at a given age. There were no significant differences in growth between clams collected at 1,3, 5, and 7m depths in the lake despite marked differences in water temperature. The wide variation in clam biomass within each depth zone may have masked possible effects of water depth.

3. The effect of water depth and variation in clam density on clam growth was tested directly by stocking clams into small enclosures at densities equivalent to 50, 150, 250, 350 and 450g m‐2 (live weight) at each of 1, 3, 5 and 7 m depths in Narrow Lake (each depth and abundance treatment in triplicate). A uniform sandy substrate was used in all enclosures to eliminate any possible effect of substrate type on growth.

4. Mortality was negligible (0.9%) during the experiment. Clam density had no significant effect on clam growth which suggests that clam growth was not food limited in the lake.

5. Clams reared at 7 m grew more slowly than clams reared at 1, 3 and 5 m. Clams reared at 5 m grew more slowly than clams reared at 1 and 3m. Growth of clams reared at 1 and 3m did not differ. These differences in growth were strongly correlated with the measured differences in water temperature between depths.

6. Migration between depths probably accounts for the lack of a depth effect on clams growing in the natural habitat.
A note on Lake Goang, an unusual acid lake in Flores, Indonesia
Authors: GREEN J. , KRAMADIBRATA HASIANA
Published: May 2006

SUMMARY. 1. Lake Goang has a pH of 2.5. Associated with this low pH are high concentrations of sulphate, chloride, iron and aluminium. There are no fish in the lake.

2. A single species of Heterococcales was found in the phytoplankton.

3. The zooplankton consists of one species of rotifer and a stalked species of Vorticella.

4. The shallow water fauna consists of two species of nematodes, at least two larval Diptera, one trichopteran, a zygopteran, a small crab (Sundatelphusa) and a cyclopoid copepod (Paracyclops).

5. During January an oily slick appears and is deposited as asphalt around the shore of the lake.
Interspecific and intraspecific variations in egg hatching for British populations of the stoneflies Siphonoperla torrentium and Chloroperia tripunctata (Plecoptera: Chloroperiidae)
Authors: ELLIOTT J. M.
Published: May 2006

SUMMARY 1. The objective was to compare variations in egg hatching between the two species (interspecific variations) and between populations of the same species (intraspecific variations). There were significant interspecific, but not intraspecific, differences in female size, adult life‐span, egg production, hatching success, incubation periods and hatching periods.

2. The optimum temperature for hatching success within the range 3.8–22.1°C in the laboratory and the range over which at least 50% of the eggs hatched were lower for Chloroperia tripunctata (Scopoli) (8.5°C, 4.2–17.3°C) than for Siphonoperla torrentium (Pictet) (12.8°C, 6.1–19.4°C). Few eggs hatched at 22.r°C.

3. The relationship between incubation period (d days) and water temperature (T°C) was given by: d=1219/T1.368 for S. torrentium, d=253/T0.459 for C. tripunctata. Both equations successfully predicted incubation periods for eggs placed in a stream. The period over which eggs hatched was much longer for C. tripunctata than for S. torrentium at all temperatures.

4. The shorter incubation period (at r>5.6°C) and shorter hatching period for S. torrentium ensure that larvae of this species are already growing when eggs of C. tripunctata start to hatch, but the prolonged hatching period of the latter species ensures a long period of larval recruitment to the population. These differences in egg hatching may reduce competition between the two closely‐related species.
Influence of environmental conditions on the ovarian cycle and serum chemistry of Cyprinus carpio in the Dal lake, Kashmir (India)
Authors: FIDA SHAHNAZ , QADRI M. YASEEN , SIDDIQI MAQSOOD
Published: May 2006

SUMMARY 1. The study presents adaptive and acclimatory changes observed in Cyprinus carpio communis L with respect to ovarian cycle and serum levels of electrolytes, calcium, total proteins and albumin as a consequence of wide temperature and sunshine variation in the natural environment of Dal lake in Srinagar, Kashmir (India).

2. The atmospheric temperatures in Srinagar show well‐defined seasonal and diurnal variations. During the period of study, the mean monthly average temperature in summer (June‐August) was 24°C whereas in winter (December‐February) it fell to 3.6°C. The total hours of sunshine during the winter months were about half of those found in summer.

3. Under local thermal and photo conditions the fish was found to spawn once a year compared to biannual spawning in tropical chmates.

4. A significant decrease was found in serum sodium, potassium and chloride concentrations during the months of January and February when the mean minimum atmospheric temperatures reached −2.5°C and −l.2°C respectively.

5. The serum calcium levels showed a marked increase during the period corresponding to ovarian maturity and spawning of fish.

6. A significant rise in total serum protein concentration was induced by decreased environmental temperatures. Serum albumin levels were found to exhibit a sharp fall coinciding with the spawning period.
Reproductive mode in populations of Daphnia pulex and Daphnia obtusa from the East Midlands of Britain
Authors: WARD ROBERT D. , GEISSLER PAUL A.
Published: May 2006

SUMMARY 1. Two populations of Daphnia pulex, one from a permanent pond and one from a temporary pond, and two temporary pond populations of Daphnia obtusa in the East Midlands of Britain were examined by enzyme electrophoresis. The three temporary pond populations showed good fits to Hardy‐Weinberg expectations, suggestive of cyclic parthenogenesis, while the permanent pond population showed deviations bordering on statistical significance.

2. Laboratory characterization of the ephippiai offspring of heterozy‐gous mothers from each population showed normal Mendelian segregation and males were produced. This indicates that in both species ephippiai egg production was a sexual process, and confirms that these populations reproduce by cyclic, rather than obligate, parthenogenesis.
An inexpensive device for sampling large volumes of lake water from discrete depths
Authors: DODDS WALTER K. , PRISCU JOHN C.
Published: May 2006

SUMMARY 1. A sampler was developed that displaces surface water which is replaced with water from a sampling tube at a set depth.

2. The displacement sampler is inexpensive, easy to build, and is capable of collecting water at 7.5 I min−1.

3. Phytoplankton photosynthesis was higher in water from the displacement sampler than in water collected with a Van‐Dorn bottle. Subsequent experiments indicated this was due to inhibition caused by the Van‐Dorn bottle.
Depth selection by larval Ischnura verticalis (Odonata: Coenagrionidae): effects of temperature and food
Authors: BAKER ROBERT L. , FELTMATE BLAIR W.
Published: May 2006

SUMMARY. 1. Water temperatures in a shallow, weedy bay of a reservoir in southern Ontario were related to depth; mid‐day temperatures in summer were approximately 30°C at the water surface and 20°C below 25 cm.

2. In the laboratory, larval Ischnura verticalis released in a thermal gradient (warmest water near the surface) did not remain near the surface any more than larvae in isothermal conditions. However, larvae in both isothermal and gradient conditions tended to spend more time close to the surface than expected by chance.

3. Larvae provided with food at all depths spent more time near the surface than did larvae with no food. Larvae provided with one feeding site in the coldest water remained near the food as much as did larvae provided with a single feeding site in the warmest water.

4. Results suggest that selection of microhabitats is based primarily on food availability and secondarily on proximity to the surface.
The susceptiblity of Keratella cochlearis to interference from small cladocerans
Authors: GILBERT JOHN J. , MACISAAC* HUGH J.
Published: May 2006

SUMMARY. 1. Even at high population densities (300–2000 ind. 1−1), only one of five small cladoceran species (adult body length <1 mm) significantly suppressed population growth of the rotifer Keratella cochlearis through interference (encounter) competition. At 500 ind. H, adults of D. ambigua (0.96 mm body length) imposed an instantaneous per capita death rate of 0.21 day−1 on this rotifer. These short‐term experiments may have underestimated cladoceran interference because newborn rotifers were rarely present.

2. Newborn rotifers (<12 h old) were much more susceptible than adult rotifers (> 24 h old) to interference from Ceriodaphnia dubia. All of the small cladoceran species tested were very much less likely than large Daphnia (body lengths >1.2 mm) to interfere with K. cochlearis, but perhaps at high population densities they could suppress population growth of susceptible rotifer species by damaging, and possibly eating, relatively small and soft‐bodied newborn individuals.

3. K. cochlearis of the tecta form, without a posterior spine, produced offspring of the typica form, with a posterior spine, in the presence of C. dubia. This developmental response is stimulated by at least several, and possibly all, cladocerans and probably reduces the susceptibility of the rotifer to cladoceran interference.
On the occurrence, causes and potential consequences of low zooplankton to phytoplankton ratios in New Zealand lakes
Authors: MALTHUS TIMOTHY J. , MITCHELL STUART F.
Published: May 2006

SUMMARY. 1. New Zealand lakes are shown to have lower average zooplankton biomasses than north‐temperate lakes of similar average phytoplankton biomass, expressed as cell volume or chlorophyll a, or similar average total phosphorus concentration, typically by a factor of 5 or more.

2. Evidence suggests that the relatively low zooplankton biomasses of New Zealand lakes may be related to a tendency for them to be dominated by large algae that are not directly available as food for zooplankton, with oligotrophy lakes in particular differing from north‐temperate lakes in this respect.

3. This difference in turn may be related largely to their mixing regimes. All of the New Zealand lakes are polymietic or monomietic, whereas the northern lakes used for comparison are mostly dimietic. Also, hetero‐cystous cyanobacteria are favoured by the low inorganic nitrogen concentrations that are typical of New Zealand lakes.

4. Poor nutritional quality of the phytoplankton, relating to nitrogen limitation in many New Zealand lakes, might supplement the effects of cell size.

5. Low exploitation of phytoplankton by zooplankton can be expected to produce a shift in the metabolism of New Zealand lakes towards the sediments. Among the potential consequences of this effect are increased hypolimnetic oxygen demand with increased susceptibility to development of large internal loads of nutrients, and consequently, increased sensitivity to accelerated eutrophication from any increase in external nutrient loads.
Effects of nutrients and grazers on periphyton phosphorus in lake enclosures
Authors: MAZUMDLR ASIT , TAYLOR W. D. , McQUEEN D. J. , LEAN D. R. S.
Published: May 2006

SUMMARY. 1. Periphyton. measured as particulate phosphorus (PP) and expressed as periphyton PP, growing on vertically oriented substrata (polyvinyl impregnated nylon) under different nutrient loadings, light intensities (exposures), and grazer communities was examined in eight large enclosures (750 m3) where nutrients (N and P) and planktivorous fish (1+yellow perch) were added in a 2x2 factorial design.

2. During the first 3 weeks of the experiment (25 June to 15 July), there was a significantly higher accumulation of phosphorus into periphyton (periphyton PP) with fertilization, but fish addition had no effect. During the fourth to seventh weeks (16 July to 12 August), addition of fish was associated with lower abundance of amphipods and chironomids and higher concentration of periphyton PP. In the enclosures without fish, these invertebrates were over 25 times more abundant, and periphyton PP decreased substantially compared to the June‐July period. Fertilization increased periphyton PP only at high exposures in the enclosures with fish.

3. Exposure had a significant effect on periphyton PP. In the enclosures with fish, high abundance of nanoplankton reduced water transparency, and periphyton PP was lower in the deeper waters which may have been due to limitation by low light. Lower periphyton PP was also observed at the surface on sunny sides of enclosures without fish, and therefore with high water transparency. This pattern may have been due to inhibitory effects of high light intensity.

4. Periphyton communities in the enclosures with fish had higher uptake rates for planktonic phosphorus, and lower rates of phosphorus release, suggesting that periphyton with high phosphorus demand may have high internal cycling of assimilated phosphorus.
Environmental stress and the survival of brown trout, Salmo trutta
Authors: PICKERING A. D.
Published: May 2006

SUMMARY. 1. The hypothalamic‐pituitary‐interrenal axis of the brown trout, Salmo trutta, is activated in response to most forms of environmental stress. This results in an elevation of blood cortisol levels.

2. Experimental elevation of blood cortisol levels in otherwise unstressed brown trout caused a dose‐dependent increase in mortality rate due to disease. In our studies., Saprolegnia‐infection, furunculosis and bacterial fin‐rot were the principal diseases.

3. Chronic cortisol elevation also suppressed several of the endocrine processes controlling sexual maturation, resulting in a significant reduction in the size of the gonad in both male and female fish.

4. It is argued that many of the deleterious effects of sublethal pollution (including acidification) on natural trout populations can be attributed to chronically‐elevated blood cortisol levels and that a knowledge of such physiological changes would allow an assessment of the impact of pollution events and act as an early warning of potential disease and recruitment problems.
Conservation and management of brown trout, Salmo trutta, stocks in Wales by the Welsh Water Authority
Authors: CRESSWELL R. C.
Published: May 2006

SUMMARY. 1. The diversity, value and status of the trout resource within the Welsh Water Authority area is described.

2. Reported angling catches of sea trout have increased in recent years but there is an apparent decline in brown trout stocks. Factors affecting the distribution, status and diversity of the trout resource are identified and discussed.

3. Investigations are being carried out to evaluate the apparent problems and to provide information required to formulate management solutions. A management strategy is proposed which allows for the maintenance and development of the resource, whilst ensuring the preservation of strains of trout which have conservation value in their own right.
Changes in diatom‐inferred pH and add neutralizing capacity in a dilute, high elevation, Sierra Nevada lake since A.D. 1825
Authors: HOLMES R. W. , WHITING M. C. , STODDARD J. L.
Published: May 2006

SUMMARY. 1. We developed equations which describe relationships between the relative abundance of diatom assemblages in the surface sediments of twenty‐seven Sierra Nevada lakes and the present pH and acid neutralizing capacity in these lakes.

2. These equations were employed to reconstruct pH and acid neutralizing capacity at twenty‐four depth intervals in a 20 cm long sediment core from Emerald Lake, a dilute, high elevation lake, located in Sequoia National Park, California, U.S.A.

3. The diatom‐inferred pH and acid neutralizing capacity values indicated that neither pH nor acid neutralizing capacity exhibited significant trends since about A.D. 1825. We conclude from our diatom analysis that Emerald Lake has not been affected by acidic deposition.
Timing of emergence of males and females of Ephoron shigae (Ephemeroptera: Polymitarcyidae)
Authors: WATANABE NAOSHl C. , YOSHITAKA ICHIRO , MORI IKUE
Published: May 2006

SUMMARY. 1. The winged adults of Ephoron shigae swarming over the water surface were collected by successive random sweeps during their daily emergence period, and the changes in sex and stage composition were examined, in the lower reach of the Asahi River in western Japan.

2. The emergence occurred mainly during a 11/2 h period beginning some time after sunset. Male sub‐imagos emerged synchronously and moulted to imagos in a 25 min period immediately prior to an abrupt increase of female emergence.

3. This timing of male emergence may be considered the result of selection of males to decrease the risk of death before mating, and for all the males to have an equal opportunity to mate.
Long‐term investigations of trophic relationships in southern chalk streams
Authors: LADLE M.
Published: May 2006

SUMMARY. 1. An understanding of the feeding relationships of organisms is fundamental to our capability to conserve and manage aquatic systems. At one extreme we must study the cyclic and erratic physical processes which govern the reproduction, survival and growth of consumers and their‘prey’and at the other the rates of food consumption, the assimilation of nutrients and the energetic interactions of plants, animals and micro‐organisms.

2. Since the commencement of freshwater science in this country, our understanding of the mechanisms by which producers and consumers interrelate has increased greatly. Information is required basically on three levels: (1) Short‐term laboratory and field studies designed to provide detailed data on aspects such as habitat selection, growth, feeding behaviour, etc. (2) Investigation of patterns of change which show periodicities of weeks, months or even a few years associated with the life cycles of many plants and animals and with the seasonal variations in physical and chemical parameters. (3) Long‐term surveillance and monitoring, often in a superficial manner, of particular aspects of river ecology in order to detect trends of change or patterns of variation over tens or hundreds of years and, if possible, to relate these to recorded climatic changes.

3. Long‐term data collection, in the scale of human longevity, is most appropriate to phenomena which show readily indentifiable periodic maxima or minima or which occur at well defined times (for example the discharge of a river or the start and finish of flow in a winterbourne). Alternatively, information which is amenable to automatic or semi‐automatic monitoring (temperature, water chemistry, fish migration) or integrated sampling (insect abundance, annual removal of cut water weeds) may also provide valuable evidence of long‐term change.
Diatoms as indicators of water quality in some English urban lakes
Authors: GUZKOWSKA M. A. J. , GASSE F.
Published: May 2006

SUMMARY. 1. The paper describes diatom communities from a series of linked urban lakes in relation to water chemistry and uses multivariate statistical techniques to show how indicator groups can he defined.

2. Diatoms are classified into ecological groups using two‐way species indicator analysis (TWINSPAN). Each ecological group is associated with a specific range of water‐quality conditions. The headwater stream environments are differentiated from the lake habitats at level 1. At level 2 of TWINSPAN. the sampling sites are grouped into five ecological groups, according to their water chemistry and irrespective of the time of year.

3. Detrended correspondence analysis (DCA) and principal components analysis (PCA) provide two statistically independent methods of assessing the environmental gradients along which the ecological groups are distributed. The most important physico‐chemical parameters are total hardness, specific conductance and pH, followed by phosphates and nitrates.

4. Ecological groups I‐V correspond to an environmental gradient ranging from the forested headwaters, which are acidic, of low specific conductance, total hardness and nutrient content, through the urban lakes, which are alkaline and of relatively high total hardness, specific conductance and nutrient content.

5. Twelve site groups are identified at level 3 of TWINSPAN, each of which corresponds to a narrower range of water‐quality conditions within the ecological groupings. A specific diatom assemblage is associated with each site group.

6. Benthic diatoms form an integral part of the diatom assemblages found in the water column and this is identified as a topic for further study.