bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in Chemical Composition, Reproductive Success and Body Weight of Daphnia magna in Relation to Diet
Authors: Cowgill U. M. , Emmel H. W. , Hopkins D. L. , Takahashi I. T. , Parker W. M.
Published: February 2007

The concern of this study has been the chemical composition of Daphnia magna, the algae (Selenastrum capricornutum, Ankistrodesmus convolutus) it was fed, the two growth media in which the algae were cultured and the water (Lake Huron, Michigan, USA) in which D. magna was reared. A synthetic diet (fish chow + alfalfa) was used as a control. The effectiveness of these five diets on the health of the D. magna populations was ascertained by the weight and number of neonates thus produced. The diet, S. capricornutum cultured in an organic medium, produced the largest mean brood size and the heaviest neonates in unstressed populations. The synthetic diet produced the smallest mean brood size and the lightest neonates. Stressed organisms may produce smaller broods with heavier neonates than unstressed organisms. The evolutionary significance of this observation is discussed. Statistical studies suggest that daphnids maintained on the synthetic diet derived no demonstrable nutritive value from the diet in terms of elemental composition or amino acid production. A great similarity in patterns of amino acid quantity and type was noted in the algae and the daphnids. On further examination it was discovered that this pattern was widespread in other aquatic forms, bacteria, fungi, yeasts, casein and was common to a variety of birds and mammals. It may be suggested that products that are made and stored, such as lipids, are less uniform in pattern among widely diverse species than those that have to be produced and are not stored, such as amino acids.
Field and Laboratory Studies on Nile Phytoplankton in Egypt. I. Some Physical and Chemical Characteristics
Authors: Ahmed Ahmed M. , Haikal Medhat M. , Mohammed Ahmed A. , Zidan Mohammed A.
Published: February 2007

Monthly variations of some physical and chemical characteristics of Nile waters at Assiut (375 km south from Cairo, Egypt) during the period from September 1980 to September 1982 were followed and discussed. As expected, the maximum temperature was recorded in summer and the minimum in winter. The pH values of Nile waters were recorded to be in the vicinity of 8.0. The highest oxygen concentrations were recorded in the summer months, mainly due to the relatively high photosynthetic activity. The total soluble salts and the total alkalinity exhibited almost identical trends. Nitrate, phosphate, silicate and chloride concentrations showed no major regular trends. The cation abundances by weight were as follows: Ca2+ > Na+ > Mg2+ > K+.
Vertical Distribution of Tintinnopsis lacustris (ENTZ) and Tintinnidium fluviatile STEIN (Ciliata) in Lake Kozjak (Plitvice Lakes), Yugoslavia
Authors: Primc Biserka
Published: February 2007

The seasonal changes in the vertical distribution of Tintinnopsis lacustris and Tintinnidium fluviatile was studied in the Karst Lake Kozjak, one of the group of Plitvice lakes. The question asked was to what extent does the development of these two species‐populations follow the seasonal fluctuations and spatial distributions of the planktonic community or the seasonal changes in environmental conditions.
Effect of Non‐removal of the Macrophytic Biomass on the Characteristics of Water and Plant Community in Lake Naini Tal, U.P., India
Authors: Purohit Rekha , Singh S. P. , Upreti Neeraj
Published: February 2007

In the most productive macrophytes stand lying within the littoral zone of Lake Naini Tal (a Kumaun Himalayan Lake, located 1937 m above sea level) the macrophytic biomass was removed at the time of peak biomass one year, but not during the next. The effect of non‐removal of the macrophytes was apparent in the physical and chemical parameters of the water, viz: thermal stratification, pH, dissolved oxygen, calcium and nitrogen content. The removal of macrophytes increased the plant diversity. Seasonal patterns of ash, calcium and nitrogen content in plant tissues were different for the two years of study.
Structure of Periphytic Communities in Cooling Pond of Nuclear Power Plant
Authors: Protasov Alexander A. , Afanasyev Sergey A.
Published: February 2007

Periphyton was studied in the cooling pond of a nuclear power plant in the Ukraine. Fourteen periphytic communities called by the dominants were distinguished on the basis of an analysis of visually detected homogeneity distribution and with reference to results obtained from treatment of samples. Relationships among communities were determined by a method similar to taxonomic analysis according to E. S. SMIRNOV. The periphytic communities were shown to be integrated in two “large” communities gravitating towards the thermogradient poles. Temperature was the important factor that determined the macrostructure of periphyton in the cooling pond.
Antarctic Stream Ecosystems: Variability in Environmental Properties and Algal Community Structure
Authors: Howard‐Williams Clive , Vincent Connie L. , Broady Paul A. , Vincent Warwick F.
Published: February 2007

The variability in physical, chemical and biological properties was examined for a number of glacier melt streams in south Victoria Land, Antarctica. Streams flowed for between one and two months. Stream water temperatures (range = 0–11°C) varied over short (hr) time scales whilst discharges varied considerably between streams (range 0.001–15 m3s−1) and over diel cycles. Solar radiation and air temperature were major determinants of stream discharge. Variability in discharge was reflected in variability in nutrient chemistry and sediment load. Nitrogen and phosphorus varied considerably between streams; the meltwaters early in summer contained 10–20 times higher levels of dissolved N and P than later in the season. Within stream nutrient levels were modified by dense algal growths and penguin rookeries. Epilithic algal communities were made up predominantly of cyanophyceae which formed mats and crusts. Longitudinal and horizontal variability of species in the communities in selected streams is described. Analyses of algal cover and biomass (chlorophyll a) show that substrate type and flow rates are of greater importance than nutrients in influencing algal abundance and biomass. In some streams biomass values of over 20 μg Ch. a cm−2 were recorded, much of which remains viable but inactive over the antarctic winter.
Investigations of the Benthos of Mangrove Coastal Lagoons in Southern Cuba
Authors: Lalana‐Rueda Rogelio , Gosselck Fritz
Published: February 2007

Benthic studies were undertaken in two mangrove‐lagoons on the south coast of Cuba. Both lagoons are approximately 30–50 cm deep and the tidal range is 15–20 cm. There is little influx of fresh water, and the lagoons are normally euhaline. Most of the lagoon bottom is not colonized by plants, although filamentous algae (Cladophora and Enteromorpha spp.) and Thalassia testudium grow in a few places. Meiobenthic organisms account for 92% of the invertebrates in the benthic zone of the lagoon. The five most common taxa (Nematoda, Copepoda, Tanaidacea, Oligochaeta, Polychaeta) account for 88–94% of the total number of individuals in Tolete Lagoon and in Basto Lagoon the five most common taxa (Nematoda, Copepoda, Ostracoda, Amphipoda, Polychaeta) account for 97–98%. Biomasses were 26.6 g/m2 in Tolete and 20.2 g/m2 in Basto Lagoon. The dominant taxon on the roots of Rhizophora mangle is Crustacea (Balanus eburneus, B. recurvus and Corophium insidiosum), accounting for over 60% of the total number of individuals. They are followed by molluscs (Crassostrea rhizophora) and the polychaetes (serpulids).
A Phytoplankton Bloom in Shallow Divor Reservoir (Portugal)—The Importance of Internal Nutrient Loading
Authors: Cabeçadas Graça , Brogueira Maria J. , Windolf Jörgen
Published: February 2007

The development of a heavy phytoplankton bloom (chl. a = 360 mg/m3), which occurred in the summer 1983 in a shallow reservoir, Divor, is described. The study shows that remobilization of phosphate from the sediment was initiating the phytoplankton bloom. This was confirmed not only by calculations of the change in iron‐phosphate pool, but also supported by sorption experiments carried out with the sediment. It is discussed that turbidity of the water due to suspended matter caused the reduction in standing stock of phytoplankton to approx. 50 mg chl. a/m3 in late summer.
Distribution of Macrophytes in Relation to Environmental Factors in the Ter River, N. E. Spain
Authors: Peñuelas Josep , Sabater Francesc
Published: February 2007

Most of the tested water quality factors increase downstream coinciding with changes in the aquatic vegetation, from typical species of fast‐flowing oligotrophic waters to those of slower‐flowing eutrophic waters. Several statistic analyses were carried out to relate physical and chemical parameters with plant distribution. Five vegetation types are found in a longitudinal distribution along the river system. They are dominated by bryophytes in the initial parts before the reservoirs and by higher plants in the final parts after the reservoirs.
Stratigraphy of Cladocera (Crustacea) and Chironomidae (Insecta: Diptera) in Three Sediment Cores from the Central Baltic Sea as Related to Paleo‐salinity
Authors: Hofmann Wolfgang
Published: February 2007

In three sediment cores from the Central Baltic Sea (Bornholm Basin, Gdansk Bay) corresponding horizons with maximum abundance of remains of a limnetic fauna (Cladocera, Chironomidae) were found. These associations indicate the existence of an oligotrophic freshwater lake. However, this horizon does not coincide with the Ancylus stage but is located in sediment layers from the very end of that period, or from the Mastogloia stage, which was a transitional brackish water phase.
Effects of Sewage Dumping on Macrobenthic Invertebrates in the Jordan Gulf of Aqaba, Red Sea
Authors: Ismail Naim S. , Awad Jamal
Published: February 2007

There are two sewage outfalls along the Jordanian coastline in the Gulf of Aqaba. During 1982 and 1983 a total of 328 core samples (0.01 m2 to a depth of 15 cm) were collected from the two outfalls, two control stations which resemble the outfalls in depth and sediment texture, and from two stations 100 m on both sides of each outfall. Faunal analysis revealed that the total number of individuals, number of species, species richness, and faunal similarities of macrobenthic invertebrates were lower at the sewage outfall near the phosphate loading port than the control station during both collections. At the 100 m stations, the numbers of individuals were generally higher than the sewage and control stations. The number of species, however, was highest at the control station and lowest at the sewage outfall.

At the other sewage outfall, where the sewage effluent is discharged sporadically, no measurable effects on macrobenthic invertebrates were found.
Computer Aided Interactive Classification and Mapping of Aquatic Areas
Authors: Forsgren Per‐Ola , Wallsten Maud
Published: February 2007

Classification and mapping of aquatic vegetation is an important task in limnology. In this paper we will present a new computer aided and interactive method for this purpose. It is similar to older techniques in that the classification relies on the judgement of the human eye. The precision is increased by using a linear diode array scanner and the evaluation times are reduced by introducing computer vision techniques. Combining these in an interactive environment gives the operator a powerful tool for the classification. The results from a mapping of aerial infrared colour photographs will be presented.
Factors Affecting the Benthic Community Structure of a Discontinuous Stream in Guadelupe Mountains National Park, Texas
Authors: Meyerhoff Richard D. , Lind Owen T.
Published: February 2007

McKittrick Creek, a discontinuous mountain‐desert stream in Guadelupe Mountains National Park, Texas, was sampled at discrete locations (pools) to test for differences in biomass, density, species diversity, equitability, and species richness in the benthic macroinvertebrate community. Significant differences occurred among pools for these biotic characteristics of the benthic community along the downstream gradient. Pools connected by flow were more similar to each other than pools separated by dry reaches. Variation in the quantity of coarse detritus and periphyton best explained differences among pools.
Field Studies Concerning the Fecundity of Daphnia galeata, its Causes and Consequences
Authors: Horn Wolfgang , Horn Heidemarie
Published: February 2007

Field studies on a Daphnia galeata population in the mesotrophic man‐made lake Saidenbach show that the fecundity of the animals depends on individual size, water temperature and the food supply (absolute quantity, specific food supply, food quality). These different factors are subsumed in the ingestion rate (rate of individual food intake per unit time), which is of an integrative character. The fecundity plotted versus ingestion rate yields a graph with the shape of a saturation curve. Attention is drawn to the consequences in terms of variation in population size.
Photosynthesis of Natural Populations of Aphanizomenon flos‐aquae: Some Ecological Implications
Authors: Pechar Libor
Published: February 2007

The photosynthetic characteristics of different natural populations of Aphanizomenon flos‐aquae RALFS ex BORN. et FLAH. were measured in laboratory. Two types of A. flos‐aquae, partly var. klebahnii (small needle‐like colonies, 0.1–0.3 mm long on the average, growing at transparency reduced by high density of nanoplankton to about 0.5 m) and partly var. flos‐aquae (colonies flake‐like up to 20 mm long, which grow when transparency is about 1.5 m or higher) were investigated. The photosynthesis‐irradiance (P–I) curves of var. klebahnii were characterized by a high value of the initial slope and photoinhibition at relatively low light intensities (250–400 μE. m−2. s−1). In var. flos‐aquae the P–I curves had a lower initial slope and no photo‐inhibition was observed in the range of irradiance to 450 μE. m−2. s−1. The effect of different sizes of colonies on photosynthesis and possible impact of strong light (induced by Daphnia feeding activity) to promoting the large‐flakes Aphanizomenon in the presence of large Daphnia are discussed.
Biology of Latia neritoides Gray 1850 (Gastropoda, Pulmonata, Basommatophora): the Only Light‐producing Freshwater Snail in the World
Authors: Meyer‐Rochow V. B. , Moore S.
Published: February 2007

This report on the freshwater pulmonate basommatophoran Latia neritoides of the North Island of New Zealand is based on field and laboratory studies. It deals with aspects of the habitat, describes biological adaptations of organs and organ systems in Latia, reviews the chemical basis of bioluminescence in this species, discusses the possible roles of light production in Latia, and addresses zoogeographic and phylogenetic questions.
Polychaetous Annelids from the Gulf of Nicoya, Costa Rica
Authors: Maurer Don , Vargas Jose , Dean Harlan
Published: February 2007

Polychaetous annelids from a soft bottom community (1–46 m) were sampled from the Gulf of Nicoya, Costa Rica. A total of 125 species was identified, 120 from a faunistic study throughout the gulf and 78 species from a time study at four stations. The number of species from the Gulf was not as high as in some temperate areas. Temporal differences were slight compared to station differences. Twenty dominant species indicated three descriptive patterns: 1) Species with a marked seasonal peak and stable densities thereafter; 2) Species with a moderate seasonal peak and stable densities thereafter; and 3) Species with no discernible seasonal peak. Although 10 polychaete feeding guilds were identified, species from six feeding guilds were the dominant groups. The effect of the rainy season on polychaete opportunism and feeding guilds was discussed.
A Three Years' Study of Life Cycle, Population Dynamics and Production of Asellus aquaticus L. in a Macrophyte Rich Stream
Authors: Iversen Torben Moth , Thorup Jens
Published: February 2007

Populations of A. aquaticus were sampled quantitatively in 1979–82 at two localities in the river Suså which has a slope of <1 m km−1 and large variations in macrophyte biomass, discharge and stream velocity. The latter two differed significantly between years. A. aquaticus had (1)−2 life cycles per year and summer and winter cohort production intervals of 85 and 290 days. Populations of A. aquaticus varied between 0 and 28,000 ind. m−2 with an exponential increase in the spring and an exponential decrease in the autumn‐winter. The A. aquaticus rate of decrease varied between 0.62 and 5.61 % d−1 and increased with increasing rate of elimination of the macrophyte biomass Differences between the two localities were due to differences in physical heterogeneity. Production varied between 2.8 and 9.1 g DW m−2 yr−1 and between 12.9 and 55 g DW m−2 yr−1 at the two localities and P/B ratios were 7.4–9.9 yr−1. Physical limitations are thought to be most important for the populations of A. aquaticus in the Suså, and the macrophyte biomass played an important role in modifying the physical environment. Differences between streams and lake populations are discussed.
Meteorological and Hydrographical Features of Vellayani Lake, Kerala, India
Authors: Jayachandran K. V. , Joseph N. I.
Published: February 2007

Meteorological, physical and chemical parameters of Vellayani Lake, Kerala, India, have been analysed for twelve months (August 1980 to July 1981), the topography of the lake is described, and correlation coefficients were calculated between meteorological and hydrographical parameters. The results indicate that the lake can be converted into a productive aquafarm by means of slight manuring.
The macrophytes in lake Änketjärn—a lake dominated by Juncus bulbosus L
Authors: Svedäng Maria
Published: February 2007

The distribution of macrophytes and the biomass development during the summer was studied in the slightly acidified Lake Änketjärn in western Sweden. The submerged cyperid Juncus bulbosus, which has been reported to expand in acidifying lakes, covered almost 50% of the lake area. The most dense Juncus vegetation was found at 1.5 m on loose, highly organic sediment. Besides J. bulbosus the vegetation was characterized by Nympheids, Carex rostrata and C. lasiocarpa (approximately equally important in the stands), Equisetum fluviatile and Lobelia dortmanna, species which showed a quite distinct zonation with depth.
Nucléotides adényliques et assimilation photosynthétique du phytoplancton dans deux lacs du Massif Central français
Authors: Amblard Christian
Published: February 2007

Adenine Nucleotides and Phytoplanktonic Primary Production in Two Lakes in France

The adenine nucleotides concentrations and photosynthetic assimilation of phytoplankton were established during two annual sampling seasons for two lakes with different nutrients concentrations (Lakes Pavin and Aydat). Intensive photosynthetic assimilation of phytoplankton led to a limited but real evolution of the pool of adenine nucleotides towards forms less charged with high energy phosphate bond (ADP and AMP). This evolution is seen as a consequence of the ATP hydrolysis in the process of cell biosynthesis.
Die Veränderung populationsdynamischer Parameter bei Gammarus tigrinus Sexton (Crustacea: Amphipoda) als Ausdruck subletaler Effekte durch die Wechselwirkung von Temperatur und cadmiumkontaminiertem Futter
Authors: Hackstein Elisabeth
Published: February 2007

Changes in the Population Dynamics of Gammarus tigrinus SEXTON (Crustacea: Amphipoda) as Expression of Sublethal Effects by Reciprocal Interactions of Temperature and Cadmium Enriched Food

The population dynamics of Gammarus tigrinus SEXTON were studied in a flow‐through system under semi‐natural conditions over a period of 9 months. Elevated temperatures and Cadmiumenriched food alter lifespan of generations, growth rate, number of individuals and time to reach maturity, even before elevated Cadmium concentrations can be detected in the animals. Reciprocal interactions of Cadmium intake via food and/or water can be modified by the experimental design, because it depends on the experimental animals, on the Cadmium concentration and on the temperature regime with constant or cyclic conditions.
The Ecology of Baetis muticus and Baetis rhodani (Insecta, Ephemeroptera), with Special Emphasis on Acid Water Backgrounds
Authors: Willoughby L. G.
Published: February 2007

The two mayflies (Insecta, Ephemeroptera) Baetis muticus and Baetis rhodani are absent from the acid water (pH 4.8–5.2) streams of the Upper Duddon drainage basin. Field observations and laboratory experiments were used in an attempt to explain this absence. Baetis muticus could not tolerate acid water; in addition it was deduced that available foods in the Upper Duddon streams would not sustain it there, even if the water could be tolerated. Baetis muticus feeds by browsing on decaying, allochthonous leaves, implying an input of micro‐organisms, especially fungi, to the diet. Well‐decayed, allochthonous leaves do not occur in the acid water, Upper Duddon streams. Baetis rhodani proved to be acid water tolerant, but only if the background waters had high ionic loadings. Since Upper Duddon waters have only low ionic loadings, Baetis rhodani is apparently excluded from them on this account. The evidence was that if the Upper Duddon waters were chemically suitable, then Baetis rhodani could survive in them, because a suitable food, the alga Hormidium subtile is present.
Temporal and Spatial Meiofauna Fluctuations in an Inlet of the South West Baltic (Darss‐Zingst Bodden Chain) with Special Reference to the Harpacticoida (Copepoda, Crustacea)
Authors: Arlt Günter
Published: February 2007

Diurnal, seasonal and annual fluctuations of the meiofauna population density were recorded during long term investigations carried out in an inlet of the southwestern coast of the Baltic from 1970 to 1980. Field experiments have shown a diurnal vertical migration of harpacticoids, which leave the sediment at night to colonize the pelagic zone 14 times more densely than during day. Besides the seasonal fluctuations considerable differences were observed between the meiofauna densities in two successive years from samples taken twice in a grid consisting of 98 stations: the abundances of all meiofauna taxa decreased by approximately 50 %. These fluctuations are not only caused by the reproductive activities of the meiofauna under different environmental conditions, but they are to a great extent a result of the active and passive movements of the meiofauna.
Valvata piscinalis O. F. MÜLLER (Mollusca, Prosobranchia) and its Epizoic Diatoms from Lake Trichonis, Greece
Authors: Falniowski A. , Economou‐Amilli A. , Anagnostidis K.
Published: February 2007

The ultrastructure of Valvata piscinalis O. F. MÜLLER, a mollusc collected from Lake Trichonis, Greece, is illustrated by SEM and compared with Polish specimens. The specific features observed are leading to the characterization of the specimens as an ecotype. The epizoic algal growths, ascertained by direct examination or scraped from shells of V. piscinalis, are commented.
Calcium and Magnesium in Dal Lake, a High Altitude Marl Lake in Kashmir Himalayas
Authors: Ishaq Mohammed , Kaul V.
Published: February 2007

Monthly sampling of calcium and magnesium in the in‐ and outflows of Dal Lake revealed high concentrations of both during summer. The monthly inputs, outputs and retentions of these alkaline earths were estimated. The lake on an overall basis showed the retention of calcium but not of magnesium. This was suspected to be related and affected by variable flushing rates of water. Most of the calcium and magnesium was present in sediments and only a small fraction in the water and in macrophytes. The calcium balance is discussed in relation to the P‐balance.
Sublittoral Macrobenthic Infaunal Assemblages of Two Nearby Embayments from Central Chile
Authors: Carrasco Franklin D. , Gallardo Victor A. , Medrano Sonia
Published: February 2007

The benthic assemblages in two Central Chile nearby embayments were studied from quantitative samples collected from 15 sites at depths of 8–65 m. The macrobenthic infauna (<0.5 mm) of both bays was greatly dominated by polychaetes. Some 93 taxa were identified, of which 51 were polychaetes. The average macrofaunal abundance for all stations (15,021 ind. m−2) is very close to the values reported for the neighboring areas. Numerical classification and ordination (DCA) of sites resulted in three site‐groups mostly reflecting differences in the bottom sediments: the muddy‐bottom stations of Concepción Bay and the shelf‐associated stations, the sandy‐bottom stations of San Vicente Bay and an heavily polluted station at San Vicente port. Classification of species showed that the muddy‐bottom stations and the sandy‐bottom sites had characteristic species assemblages. The macrofaunal assemblages presented high dominance values, which were due to the high numerical abundances of a few species in the collections.
Historic Trends in Lake Michigan Silica Concentrations
Authors: Schelske Claire L.
Published: February 2007

Historic data on soluble silica in the offshore waters of Lake Michigan were compiled and analyzed to determine whether the data supported a decrease in silica concentration which had been hypothesized previously on the basis of other studies. Although the data base was limited and no data were obtained for offshore waters (depths >40 m) prior to 1954, the available data support the conclusion that the silica concentration decreased rapidly after 1954. The thesis is developed that rapid silica depletion occurred in the 15‐year period from 1954 to 1969 when the winter maximum concentration decreased from approximately 4.4 to 1.4 mg SiO2 · 1−1 and the summer minimum decreased from approximately 2.2 to <0.2 mg SiO2 · 1−1. The decrease in silica concentration is attributed to increased production and sedimentation of diatoms that resulted from increased anthropogenic phosphorus loading. Total phosphorus in offshore waters was probably <10 μg P · 1−1 during the period of rapid silica depletion. The rapid decrease in silica concentration with relatively small phosphorus enrichment demonstrates that the tight coupling of biological and geochemical processes drastically affected the biogeochemistry of silica in a large, aquatic system within a relatively short period of time.
Activity of the Respiration Electron Transport System (ETS) Different Size Particles as a Measure of Carbon Losses from Primary Producers
Authors: Rai Hakumat
Published: February 2007

In situ ETS‐activity of size‐fractionated natural phytoplankton communities was studied to determine the relative rate of respiration of different size fractions. Different lakes of varying trophic levels were examined. This study suggested that <35 μm organisms are the major contributes of respiratory‐enzyme activity to the total community respiration. The results of this study indicate that half or more of the losses of primary productivity in different particle sizes are from respiratory activity. The data collected during this research on the photosynthetic rates and P/R ratio of different size particles give better information than primary productivity alone on community metabolic rates for evaluating productivity measurements.
Diurnal Variation in Feeding and Assimilation Rates of Planktonic Rotifers and its Possible Ecological Significance
Authors: Arndt Hartmut , Heerkloss Reinhard
Published: February 2007

Though rotifers play an important role in many pelagic ecosystems, there is a lack for studies on diurnal variations in feeding behaviour. Diurnal feeding rhythms of estuarine populations of Brachionus plicatilis and Keratella cruciformis f. eichwaldi and a pond population of K. cochlearis were investigated using 14C‐Chlorella and 14C‐labelled natural bacteria populations, respectively, as a tracer food during in situ experiments. A 51Cr/14C double tracer technique was used to determine Assimilation efficiencies.

All species had about two times higher feeding rates during day than during dark hours. There was a tendency for higher values during the afternoon. No trend was found regarding diurnal changes in assimilation efficiency.

Diurnally segregated niches between microphagous daytime active rotifers and nighttime active crustacean populations in pelagic ecosystems are demonstrated and their ecological significance with special regard to changes in food quality and predation pressure is discussed.
Phosphorus Load‐Concentration Relationship in Lake Dal, a High Altitude Marl Lake in the Kashmir Himalayas
Authors: Ishaq Mohammed , Kaul V.
Published: February 2007

The relationship between phosphorus concentration and estimated phosphorus load in Lake Dal—a marl lake—is described for the past decade. The concentration of this element in the lake system remained constant during this period although the P load increased by about 40 %. This phenomenon is discussed in connection with various P‐removal mechanisms operating in the lake system.
Factors Controlling the Planktonic Community in the Shallow‐Lake of Créteil, France
Authors: Lacroix Gérard , Boët Philippe , Garnier Josette , Lescher‐Moutoué Françoise , Pourriot Roger , Testard Paul
Published: February 2007

A two‐year study on the seasonal pattern of plankton was performed in a shallow, polymictic, eutrophic lake.

Autogenic successions typical of stratified lakes did not occur. Only small edible algae developed throughout the two years and Cyanophyceae rarely appeared, and did not bloom. Algal sequences depended on wind‐induced periodic mixing of water.

The seasonal pattern of Rotifers varied greatly from year to year and some species depended on sporadic increases of algae. In contrast, the seasonal pattern of microcrustacea was more regular. Resting stages played an important role in zooplankton development in this variable environment.

Successful fish reproduction depended a great deal on climatic conditions. The changes from year to year in predation pressure from young fish appeared to be an important factor controlling zoo‐plankton structure.
Seasonal Fluctuation in Species Composition of Aquatic Hyphomycetous Flora in a Temperate Freshwater Stream of Central Himalaya, India
Authors: Mer G. S. , Sati S. C.
Published: February 2007

The frequency of occurrence and seasonal periodicity of aquatic hyphomycetes in a temperate freshwater stream of Central Himalaya were studied. The number of aquatic hyphomycetes species was found to vary inversely with temperature (r= −0.499; not significant), which explained 25 % of the variability. There were two maxima, one in spring and the other in autumn. On the basis of their occurrence, the species observed have been categorised into three groups. Constant species were Campylospora chaetocladia, Flagellospora penicilloides, Lemonniera aquatica and Tetracladium marchalianum.
Field and Laboratory Studies on some Photosynthetic Bacteria in Aswan High Dam Lake. II. Isolation and Identification of Purple Non‐sulfur Bacteria (Rhodospirillaceae)
Authors: Shoreit A. A. M. , Ahmed A. M. , Shabeb M. S. A.
Published: February 2007

485 isolates were recorded from different localities between summer 1984 and spring 1985. These isolates comprise five different genera with eight different species of purple non‐sulfur bacteria‐ Rhodopseudomonas was the most common genus at all sites and was represented by three species. R. acidophila, R. blastica, R. palustris. Rhodomicrobium was the second in frequency and was represented by R. vannielli only. This species was only recorded for khor sites. Rhodocyclus was represented by two species, R. gelatinosus and R. tenuis. Rhodobacter and Rhodospirillum were represented by one species each, Rhodobacter capsulatus and Rhodospirillum rubrum. Khor sites were richer in number of isolates and genera of purple non‐sulphur bacteria than the main body of AHDL. Some species were more common in winter and spring while others predominate in summer and autumn.
Enclosure Experiments with Low‐dose Additions of Phosphorus and Nitrogen in the Acidified Lake Njupfatet, Central Sweden
Authors: Blomqvist P. , Olsson H. , Olofsson H. , Broberg O.
Published: February 2007

Experiments involving low‐dose additions of phosphate, ammonium, nitrate and ADP, one by one and in combination, were performed in small (350 litre) in‐situ enclosures in a moderately acid (pH 5.4) lake. Before manipulation, all large filter‐feeding animals were removed by filtration. Phytoplankton responded to the nutrient additions only when both phosphorus and nitrogen were added, thus indicating a close balance between phosphorus and nitrogen limitation in the system.

Variation of the inorganic nitrogen‐source resulted in species‐specific responses by phytoplankton. With ammonium as the nitrogen source Merismopedia tenuissima was favoured, regardless of whether this species was dominant in the phytoplankton community at the beginning of the experiment or not. With nitrate as nitrogen source Peridinium inconspicuum, which was never particularly common at the beginning of the experiments, was favoured. No other species of phytoplankton present in the bags was able to outcompete these two species as long as inorganic nutrients were added. With ADP as phosphorus source together with nitrate, a third species, Dictyosphaerium cf. botrytella, was favoured and reached dominance. The zooplankton community remaining in the bags, dominated by rotifers and calanoid nauplii, did not respond to the fertilization‐induced increases in the total biomass of phytoplankton.
Preliminary Observations on the Nature, Taxonomic Composition, Distribution, Behaviour and Nutrient Requirements of the “Unusual” Algal “Jellies” of Oguta Lake in Southeastern Nigeria
Authors: Nwadiaro C. S.
Published: February 2007

Preliminary observations were made between October 1982 and May 1983 on the nature, taxonomic composition, spatial distribution, buoyancy behaviour and nutrient requirements of some unusual planktonic algal “jellies” in Oguta Lake in Southeastern Nigeria. These “jellies” are macroscopic, blue‐green algal masses whose excessive mucilage of high consistency acts as substrata for other epiphytic components viz. diatoms and green algae. They are more abundant in the lentic areas of the lake, undergo diurnal vertical movements and have their growth enhanced by spikes of nitrogen and phosphorus salts into their aquatic medium. The effects of these “jellies” on the ecology and general water use of the lake are discussed. Speculations on the reasons for their occurrence are given and possible control measures outlined.
Planktonic Luminous Bacteria of Vellar Estuary, South India
Authors: Ramesh A. , Venugopalan V. K.
Published: February 2007

Distribution of planktonic luminous bacteria in relation to environmental parameters was investigated at two stations located in the Vellar Estuary. Luminous microflora showed a pronounced seasonal cycle with very low counts during monsoon months followed by an increase in post monsoon and peak counts during summer. The population density of these procaryotes was remarkably high ranging from 3.5 to 33.1 colony forming units per ml. They constituted 2.1 to 52.1 % of the total bacterial counts. Salinity appeared to govern the distribution of luminous procaryotes as their counts corresponded well with fluctuations in salinity. Taxonomic affiliation of the isolates revealed predominance of Vibrio harveyi. Vibrio fischeri and Photobacterium leiognathi exhibited sparse distribution.
Bacterioplankton and Phytoplankton Populations in a Rapidly‐Flushed Eutrophic Reservoir
Authors: Perry Sue A. , Perry William B. , Simmons George M.
Published: February 2007

Densities of bacterioplankton and phytoplankton were studied in relation to water retention time, temperature, nutrient concentrations, and other variables in a eutrophic montane reservoir (Bluestone Lake, West Virginia, U.S.A.). Weak temperature stratification occurred occasionally during the summer, but the reservoir did not become anaerobic. Water retention times were short (3.9 to 9.7 days between June and December), and differences in flushing rate within that range were important in regulating phytoplankton populations. Green algae and planktonic diatoms were dominant in summer during periods when water residence times were shorter. The occurrence of blue‐green algal blooms in fall was related to increased water residence times. Retention time was highly correlated with the percent composition of phytoplankton represented by Anabaena spp. and Microcystis sp. (r=0.898, p<0.001). Advective effects limited phytoplankton biomass when retention time was shortest, but were not as important when retention times were longer. Peaks in bacterial densities often coincided with decreases in viable algal cell densities, so bacterioplankton were less directly related to retention time.
Phosphorus Budget for Dal, a Himalayan Lake
Authors: Ishaq Mohammed , Kaul V.
Published: February 2007

The P‐budget of Dal Lake in Kashmir is described for a 12 month period. The lake is characterized by high P‐loading (7.5 g · m−2 a−1) and had high P‐retention (retention coefficient 0.32). P‐loading in the lake showed positive and negative relations with flushing rate and P‐retention respectively. A negative relation was similarly found existing between flushing and P‐retention. The roles of various biotic and abiotic factors in the P‐budget of the lake are described.
Uptake of Mineral Particles byBiomphalaria glabrata(Say.) (Pulmonata, Mollusca) and its Importance for Growth Rate and Egg Production
Authors: Schmölder Ute , Becker Wilhelm
Published: February 2007

The ingestion of mineral particles byBiomphalaria glabratais proved and the importance of these particles in the diet of the snails is investigated. The number of particles ingested rises with the size of the snails and they are retained in quantity in the alimentary tract when an adequate supply is not provided. The size of grit found in the gut differs widely from the mixture offered. Mineral particles are ingested actively and selectively.

Quantitative investigations comparing snails cultured with and without sand showed a slight advantage concerning growth and reproduction for snails cultured with sand.
The Significance of Zooplankton in the Cycling of Phosphorus in Lakes of Different Trophic Categories
Authors: Gutelmakher Boris L. , Makartseva Elena S.
Published: February 2007

The species composition, number, biomass and phosphorus excretion rate (PER) of zooplankton (Crustacea and Rotatoria) in 8 mesotrophic and eutrophic lakes were studied. PER were calculated using specific expenditures on metabolism estimated from the oxygen uptake, phosphorus content in zooplankton and field observations of number and biomass of planktonic Rotatoria and Crustacea. The zooplankton biomass and PER increased from mesotrophic to eutrophic lakes. The values of PER were compared with primary production and spring phosphorus concentration. The relative significance of zooplankton in phosphorus cycling declined with increasing trophic category of lakes.
A Natural Phosphate Source for Lake Waccamaw, North Carolina, USA
Authors: Cahoon Lawrence B. , Kucklick John R. , Stager J. Curtis
Published: February 2007

A limestone outcrop along the north shore of Lake Waccamaw, North Carolina, is found to contain ca. 0.1 % phosphate by weight. Weathering processes have probably driven steady inputs of phosphate from this source throughout the lake's history, accounting for its near eutrophic state. The sediments of Lake Waccamaw are enriched with phosphate, particularly in the littoral zone near the outcrop. Chemical and biological processes apparently remove phosphate from solution rapidly, making detection of a soluble phosphate signal near the outcrop difficult. Management of nutrient inputs and water quality in Lake Waccamaw requires consideration of the effects of this in‐lake source of phosphate. Other sources of phosphate, particularly in the lake's drainage basin, may be less important than previously thought.
The Usefulness of Various Numerical Methods for Assessing the Specific Effects of Pollution on Aquatic Biota
Authors: Heckman Charles W. , Kamieth Heino , Stöhr Manfred
Published: February 2007

The data obtained during an extensive multidisciplinary investigation of a polluted harbor basin in Hamburg were analyzed in various ways in order to determine which statistical methods are easiest to interpret and permit the most accurate evaluations. The methods analyzed include the species deficit, index of species similarity, and saprobity index, as well as the more complex cluster and gradient analyses, which revealed a variety of relationships among the biotic communities at the various sampling sites and some ecological tolerance limits of various species. The shortcomings of numerical indices for characterizing water bodies are discussed. It is suggested that biostatistical methods are much more valuable for the empirical evaluation of data than for artificially classifying ecosystems.
Proximate Composition and Nutrient Elements in the “Unusual” Algal “Jellies” of Lake Oguta in Southern Nigeria
Authors: Nwadiaro Chukwuemekanim , Idabor Peter
Published: February 2007

The proximate composition, nutrient and trace elements of the planktonic algal “jellies” of Lake Oguta in Southern Nigeria, are provided as guides to their utilization and control, using flood (rainy) and dry season samples. These “jellies” are an unusual, macroscopic planktonic algal community in the lake, made up mostly of blue‐green algae (Microcystis, Anabaena, Chroococcus) with some green algae (e. g. Spirogyra) and pennate diatoms (e.g. Navicula) rather epiphytic on the mucous jellies of the blue‐green algae. Water content was high (98.2% mean, range 97.5‐99.5%). Ash, protein and fat had values of 41.7 (39.0‐46.2%), 16.9 (15.6‐19.4%), and 2.0 (1.7‐2.1%) respectively. Crude fibre and carbohydrates were high (25.8% and 12.4%). The levels of phosphorus and nitrogen were rather high, so were the major cations whose order of dominance (Ca > K > Mg > Na) differed from that of the lake water. Macronutrients increased in their concentrations during the rainy flood season while the reverse was the case with the micronutrients. Diagenesis of the endogenic minerals rather than anthropogenic factors are thought to be the reason for the seasonal changes in the ionic concentrations. Possible uses of the algal jellies are discussed as well as their control options.
The Distribution of Mercury in the Sediments of Eight Saskatchewan Lakes
Authors: Merkowsky Alan T. , Hammer U. Theodore , Huang P. Ming
Published: February 2007

Eight lakes located in the southern half of Saskatchewan were sampled in May and June, 1987, to determine the concentration and spatial distribution of mercury in their surface sediments. Katepwa and Buffalo Pound lakes had maximum total mercury sediment concentrations of 0.158 and 0.100 μg · g−1 dry weight respectively, while in the other six lakes the mercury concentration was never greater than 0.04 μg · g−1 dw. Despite this difference in mercury concentration in the sediments of the lakes, walleye sampled from them have high mercury concentrations exceeding 0.5 μ · g−1 (wet weight).
Seasonal Variation in Community Structure of Macrobenthic Invertebrates in Sandy Beaches of Jordan Coastline, Gulf of Aqaba, Red Sea
Authors: Ismail Naim S.
Published: February 2007

Two Jordanian sandy beaches, one at the northern end and the other at the southern end near the Saudi‐Jordanian border, were examined during November 1984 to October 1985. Sediments of the South station were made of coarser sand than the North station. In general, low organic carbon and calcium carbonate levels were found at both stations. A total of 15839 animals representing 45 taxa were collected from both stations. Major differences in community structure were found between the two stations. An average density of 7981/m2, 39 taxa. an average diversity value of 1.78 and an evenness of 0.37 were characteristic of the South station. Lower number of taxa (39) and density (818/m2) were found on the North station. However, the average diversity (3.18) and evenness (0.74) were higher. Using the biological index value of MCCLOSKEY (1970), the archiannelid Saccocirrus sp. was the most dominant species at the South station and the bivalve Tellina perna at the North station.
The Assessment of Size‐class Proportions and Fisheries Mortality of Eel Using Various Catching Equipment
Authors: Berg R.
Published: February 2007

Samples of approximately 11,000 eels were used to analyse the size class composition of the eel stock in Lake Constance (Bodensee). The main statistical approach was to separate a ‘stock dependent fraction’ within the length frequency distributions obtained from three different traps and two electrofishing methods.

From the calculated size class proportions an average total mortality of 28.5% was estimated for eels bigger than 50 cm opposed to 26% total mortality for the unfished part of the population.
Re‐evaluation of Present Eel Stocking Practices in Czechoslovakia; Production of Advanced Fry
Authors: Peňáz Milan , Vostradovský Jiří
Published: February 2007

The authors have tested and recommend the rearing of eel fry until June when there are optimum conditions for stocking in open waters. Glass eels were fed either with traditional natural feeds (spleen, plankton, whitefish eggs) or exclusively with dry compound feeds for trout (EWOS, TROUVIT, VELAZ) and a special compound feed prepared by ourselves that is enriched by germ cells of Streptococcus faecium.
Gestion des barrages estuariens et migration d'anguilles. Estuary Dams Management and Eel Migration
Authors: Legault A.
Published: February 2007

Estuary dams often constitute the first obstacles of the colonization of rivers by eels. To reduce their impact, this study shows results of a special management of sluices and gates based on the glass eel migratory behaviour.
Short Note on the Effects of Cadmium on the Gill of the Glass Eel (Anguilla anguilla)
Authors: Gony Sylviane
Published: February 2007

Freshwater‐adapted glass eels have been exposed to cadmium (5 mg/l) for 3 days and then transferred in clean water for 28 days. Perturbations occurred very early (after 2 hrs only of exposure to cadmium) and concerned mainly the respiratory epithelium: the epithelial cells were very swollen and they showed an important dilation of the endoplasmic reticulum and nuclear membrane. After the decontamination period, signs of recovery appear. Perturbations of osmo‐regulatory and respiratory processes are suggested.
The Distribution of Small Larvae of Anguilla sp. Related to Hydrographic Conditions 1981 between Bermuda and Puerto Rico
Authors: Tesch F.‐W. , Wegner G.
Published: February 2007

On a section between Bermuda and Puerto Rico, in March/April 1981 Anguilla sp. larvae abundance and hydrographic conditions were studied. The small larvae (<7 mm Tl) occurred south of 30° N at the subtropical thermal front and showed peak abundance at 26° N. At 23° N larvae of all size groups became less abundant. North‐south extention of the spawning area was greater than described in the literature. A considerable net avoidance of the larvae during daylight hauls was observed. Lengths of both Anguilla species increased from the north to the peak abundance area in the south and for A. anguilla also from east to west. Patches with about the fifty fold larvae abundance compared with the surrounding area could be identified. Deeper occurrence of the smallest larvae (Tl = 4 and 5 mm) compared with older larvae, found in earlier studies could be stated.