bluuebunny/crossref_metadata_2025 huggingface dataset:
Limnological Studies on the River Tigris, Iraq. III. Phytoplankton
Authors: Saad Massoud A. H. , Antoine Samir E.
Published: February 2007

Variations in quantity and structure of phytoplankton in the lower 630 km stretch of the Tigris were studied and discussed. The Chlorophyceae generally contributed more genera to the phytoplankton community, and the Bacillariophyceae and Cyanophyceae ranked second and third, respectively. The phytoplankton generally showed considerable local and seasonal variations at the surfaces of the sampling locations.
The Hydrochemical and Physical Characteristics of the Breeding Sites of the Simulium neavei Roubaud Group and their Associated Crabs in the Eastern Usambara Mountains in Tanzania
Authors: Grunewald Jörg , Grunewald Barbara E. , Raybould John N. , Mhiddin Haji K.
Published: February 2007

Investigations on the hydrochemical and physical parameters of the breeding sites of Simulium woodi (an onchocerciasis vector). and Simulium nyasalandicum, and on their aquatic stages and associated crabs, were carried out for 13 months in the Zigi (Sigi). River system. The conductivity, pH and concentration of the main ions and silicate were all higher in the breeding sites of S. woodi than in those of S. nyasalandicum. S. woodi was restricted to small heavily shaded streams and did not enter rivers and large streams which contained higher concentrations of ammonium and nitrite. S. nyasalandicum was most numerous in rivers and large streams, but invaded small heavily shaded streams during the rainy season when conductivity and pH values were reduced.
Phytoplankton and Primary Production of Lakes in the Matamek Watershed, Quebec
Authors: Janus L. L. , Duthie H. C.
Published: February 2007

The productivity of three Shield lakes on Quebec's North Shore was found to be comparable with that of the most oligotrophic lakes known. Factors contributing to this condition may be that the moderately sized lakes of this study are deep relative to their surface areas, highly stained by humic substances, of very low conductivity, and contain little dissolved CO2. Standing crops of phytoplankton are very low, never exceeding 600 mg/m3. Chrysophyceae are dominant over all other classes of algae in both biomass and numbers, comprising approximately 50% of the fresh weight throughout the season. The abundance of micro‐flagellates implies a large surface area to volume ratio and the ability to move are an advantage in a nutrient poor environment. Much of the phytoplankton present may grow heterotrophically and energy additions from the terrestrial environment may be extremely important to the productivity of northern lakes when photosynthetic production is not significant.
A Contribution to the Phosphorus Loading Concept
Authors: Benndorf Jürgen
Published: February 2007

For the application of the empirical model of Vollenweider and Dillon (1974). and Vollenweider (1976). to reservoirs, the critical phosphorus loading levels have been related to dissolved orthophosphate. 19 reservoirs and primary reservoirs are in optimum accordance with the extended model. To permit the use of the model also in the range of very short residence times, an extremely simple analytical model of phytoplankton growth has been introduced. The reliability of the resulting outwash limits has been checked by means of random sampling at two primary reservoirs. Among 17 samples only 1 does not fit into the model.
A Rationale for the Subclassification of Biogenic Meromictic Lakes
Authors: Dickman M. D. , Hartman J. S.
Published: February 2007

An extension of Walker and Likens' (1974). scheme for the classification of meromictic lakes of the world has been based in part upon the mutual incompatibility of certain common chemical species and their generation within the monimolimnia of biogenic meromictic lakes.
The Feeding of Chaoborus flavicans Meigen (Diptera, Chaoboridae). and its Predation on Lake Zooplankton
Authors: Kajak Zdzislaw , Rybak Jadwiga
Published: February 2007

In a study of Chaoborus feeding in a eutrophic lake, selectivity was found to be positive with Crustacea (especially copepodit stages). and negative with Rotatoria. Daily food rations were about 20% for most of the feeding period, but higher (106%). during the month of intensive growth after hatching. Feeding intensity correlated positively with amount of food an temperature, and negatively with Chaoborus concentration. Elimination of Crustacea (in the epilimnion of the central zone of the lake). equalled about 30–40% of Crustacea production in June and September and slightly exeeded the August production (it was almost zero in the remaining months because Chaoborus larvae stayed at the bottom). This applies, however, only in the central zone – about 50% of the lake volume. Chaoborus probably influences both the density of zooplankton and the quantitative relations between zooplankton species.
System Analysis of Silica‐Diatom Interaction
Authors: Baumert Helmut
Published: February 2007

The prediction of and measures to prevent planktic diatom blooms in shallow lakes and slowly flowing rivers are major problems specific to water quality management. In this paper methods of mathematical systems analysis, computer simulation, and parameter identification are used to analyse a simple system consisting only of a population of planktic diatoms and dissolved silica in a shallow lake.
Factors Influencing the Diversity, Species Composition and Abundance of Phytoplankton in Twenty One Arctic and Subarctic Lakes
Authors: Moore James W.
Published: February 2007

The factors influencing the diversity, species composition and abundance of phytoplankton in 21 lakes in the Canadian arctic and subarctic were determined between 1975 and 1978. The maximum number of species (60–75). and highest diversity indices (1. 6–1. 9). were recorded from the most southerly lakes, situated at 63–64°North. Since there were fewer species (40–60). and lower diversity indices (0. 7–1.0). in lakes located at 65–66°North, temperature was the main factor influencing the diversity of the flora. Other parameters, including surface area, depth and the concentrations of nutrients, exerted little influence on the plankton. The maximum densities of several common species (Rhodomonas minutavar.nannoplanktonica, Kephyrion boreale, Ochromonas sphaerella, Ankistrodesmus falcatus, Oscillatoria limnetica). increased significantly in lakes with high concentrations of total phosphorus and total hardness whereas the reverse pattern was recorded for two other common species (Dinobryon bavaricum, D. sociale). Diatoms (mainlyAsterionella formosaandCyclotella glomerata). were restricted primarily to large lakes where turbulence helped keep these algae afloat.
The Ecology of Temporary Streams III. Temporary Stream Fishes in Southern Ontario, Canada
Authors: Dudley Williams D. , Coad Brian W.
Published: February 2007

The 12 fish species living in three temporary streams in Southern Ontario, Canada, during 1973–1974, are listed. Environmental parameters are recorded together with details of the abundance, distribution, age structure, growth, reproduction and food of the more common species. These species are thought to be either physiologically very tolerant, or to be capable of temporal or spatial migrations. Colonization of temporary streams bestows benefits in terms of plentiful invertebrate food, although resource sharing may occur, earlier spring breeding and reduced predation.
The Food and Feeding Chronology of Yellow Perch (Perca flavescens) in Lake Washington
Authors: Costa H. H.
Published: February 2007

The food habits of yellow perch (Perca flavescens) in Lake Washington, Seattle, U.S.A. were studied over a period of nine months. Altogether 549 yellow perch were examined for the stomach contents. The daily activity pattern of the yellow perch in Lake Washington appears to correspond roughly with the feeding pattern. The maximum numbers of perch caught by the nets during 24 hour study periods correspond well with degree of fullness of stomachs noted for the different times of the day. The food consisted mainly of cottids, mysid shrimps (Acanthomysis awatchensis) and chironomid pupae and larvae. There was no difference in the food consumed between the different sexes and between the different size groups. Maximum feeding by perch during the day was observed just before dark and the daily ration was calculated to be about 1.4% of their wet body weight.
Distribution of Peltoperla arcuata Needham (Ins., Plecoptera) in a Small Woodland Stream
Authors: Miller Dale E. , Kovalak William P.
Published: February 2007

The distribution of Peltoperla arcuata in a first‐order stream and its two ephemeral tributaries was studied between March and April, 1977. Overall, the distribution was highly contagious (clumped) with most nymphs concentrated in the lower reaches of the tributaries. The most reasonable explanations for aggregation in tributaries were: 1) higher food quantity and quality in early fall, 2) minimization of downstream transport by erosion of leaf packets and 3) diversion to the tributaries of upstream movement in the mainstream by obstacles (e. g., logs and boulders) in the channel.
Two New Krumbachia (Turbellaria Neorhabdocoela) from Highland Streams near Schlitz, Hesse Schlitz Studies on Productivity No. 32
Authors: Schwank Peter
Published: February 2007

The descriptions of Krumbachia paludicola n. sp. and K. hiemalis n. sp. (Typhloplanidae, Turbellaria Neorhabdocoela) are given, together with brief diagnoses and a general discussion of all species in the genus. The new species are illustrated.
The Dependence of Crustacean Respiration Rate on Body Mass and Habitat Temperature
Authors: Ivleva I. V.
Published: February 2007

The respiratorion rates of Crustacea from temperate and tropical waters of the Atlantic Ocean were measured directly at habitat temperatures of 19, 25 and 29 °C. The results were analysed together with data obtained from similar investigations in previous years (Ivleva, 1977) on Crustacea from moderately cold and polar latitudes at 10, 6 and 0 °C. Variations of the values for A and k in generalized regressions (R = AWκ) for Crustacea within the temperature limits of the physiological range were shown to have quite a clear‐cut and regular character. The coefficient k varied from 0.60 to 0.79 and revealed a tendency to increase as temperatures decreased. The value of A increased with rising temperature within all intervals from 0 to 30 °C. The quantitative relationship between respiration rate and temperature was evaluated by the Arrhenius equation. Statistical processing of resultant data indicated a rather close association between log A and the habitat temperature of the Crustacea but only slight deviations from the theory of empirically found values. The accelerating effect of temperature (μ) was 13 ± 0.13 keal/mol. This value was used to calculate Q10, which was more convenient for practical purposes.
A Limnological Reconnaissance of the Lough Erne System, Ireland
Authors: Gibson C. E. , Foy R. H. , Fitzsimons A. G.
Published: February 2007

The Lough Erne System (Northwest Ireland) consists of two linked eutrophic lakes. Phosphorus input budgets suggested mean catchment exports of 30–62 kg total P km−2 a−1, resulting in a heavy P loading to the small upper lake. The export of soluble P is related to the human population density in the catchment. Although complex in outline, the upper lake has similar phytoplankton populations throughout, but the populations in the simpler shaped lower lake differ quantitatively and qualitatively from place to place. This is probably due to differences in mixed depth. A chlorophyll a map of the surface water of the lower lake, obtained by fluorometry, showed the relationship between algal biomass and depth of water.
Field Investigations and Model Simulation of the Dynamics of Zooplankton Populations in Fresh Waters
Authors: Horn Wolfgang , Benndorf Jürgen
Published: February 2007

The main parameters characterizing the dynamics of a population were determined by field investigations at the Saidenbach reservoir and by means of an ecological model. The results obtained by both methods involving totally different procedures were in good agreement. The gross growth rates obtained by both methods ranged up to 0.14 d−1, and the net growth rates vary between 0.1 d−1 and 0.2 d−1. Field investigations revealed zooplankton mortality rates during summer of about 0.1 compared with 0.08 d−1 for the model. Comparison of the two methods shows how practical investigations may be improved and gives a better insight into the dynamics of zooplankton populations in waters.
Spatial Pattern of a Free‐Living Marine Nematode Community off the Coast of Peru
Authors: Nichols Jean Ann
Published: February 2007

The numerical abundance and biomass of free‐living marine nematodes from sandy sediment off the coast of Peru (water depth 40 m) was similar to that reported from other areas. Dispersion chi‐square analysis indicated that three species were aggregated, while the remaining species were randomly distributed throughout the samples. The most reasonable hypothesis is that variation in size of individual pore spaces is the mechanism controlling the distribution of the aggregated species.
Feeding Habits of Diaptomus ashlandi and Diaptomus sicilis in Lake Michigan
Authors: Bowers James A.
Published: February 2007

The herbivorous habits of Diaptomus ashlandi and Diaptomus sicilis were studied at a nearshore station in Lake Michigan. Filtering and feeding rates were measured from December 1975 to October 1976. Feeding was measured from the change in concentration in three size fractions of chlorophyll a. D. ashlandi fed only on particles in the smallest size class, while the larger D. sicilis consumed particles in all three size fractions. During the isothermal period (winter and spring), the feeding rates of both species were proportional to temperature or chlorophyll concentration. D. sicilis preferentially ingested particles in the largest size class, when this size class increased significantly during the spring bloom. During the summer the highest feeding rates of D. ashlandi occurred in the epilimnion. The highest feeding rates of D. sicilis were in the metalimnion, where large particles in a subsurface chlorophyll maximum were available for consumption. These results indicated the importance of the depth distributions of herbivores and phytoplankton for feeding.
Production of Urea by Bacterial Decomposition of Organic Matter Including Phytoplankton
Authors: Satoh Yasuhiro
Published: February 2007

A concentrated colony of Fragilaria crotonensis collected from the surface water of Lake Suwa, which is one of the typical eutrophic lakes in Japan, and organic matter contained in untreated surface water from the same lake were subjected to aerobic decomposition by bacteria in a dark room at a temperature of 20 ± 3 °C. An exponential increase of urea with time was recorded in both of the experiments. The apparent rate constants of urea production were calculated to be 0.083 day−1 for decomposition of F. crotonensis and 0.051 day−1 for decomposition of the organic matter contained in the untreated surface water.

This study suggests that urea production by bacterial decomposition of organic matter, including phytoplankton, may be an important source of urea in natural waters under certain conditions.
Occurrence and Distribution of Stony Corals in the Gulf of Cariaco, Venezuela
Authors: Antonius Arnfried
Published: February 2007

Occurrence and distribution of stony corals (Milleporina and Scleractinia) in the Gulf of Cariaco were investigated quantitatively using skin‐diving methods. Unusual temperature conditions due to cold upwelling limit coral growth to a depth of 15 m. A clear vertical zonation of species was observed, with five zones, in order of increasing depth, dominated by Porites porites, Millepora complanata, Siderastrea siderea, Dichocoenia stokesi, and Solenastrea hyades.

Twenty‐one species of scleractinians and three species of hydrocorals have so far been found in the gulf. Of the total area covered by corals, over 50% is inhabited by Siderastrea siderea, Millepora spp., and Porites porites. A horizontal zonation of the littoral was established based on species composition and density of the coral cover.
Abundance and Distribution of Benthic Macroinvertebrates near Little Egg Inlet, New Jersey, from 1972 to 1974
Authors: Garlo Elizabeth V.
Published: February 2007

Benthic collections taken during a 34 month period from Little Egg Inlet, New Jersey were dominated by haustoriid amphipods and collections from a nearshore ridge/swale formation were dominated by ampharetid and capitellid polychaetes. Polychaetes were most abundant at the swale station where density was 2.4 to 17.5 times higher than at other stations. Changes in species composition and density were influenced by increases in the silt/clay component of the sediment which was influenced by depth, bottom topography, and exposure to currents.
Seasonal Cycles of Zooplankton and Related Phytoplankton Development in Three Shallow, Mesotrophic Lakes in Northern Canada
Authors: Moore James W.
Published: February 2007

The primary goal of this study was to assess the importance of food in regulating densities of zooplankton in 3 northern Canadian lakes, where algal availability was low compared to temperate zone water bodies. Collections were made every 2 weeks during the summer and monthly during the winter from April 1978 to April 1979. Since the lakes were similar in most respects, including nannoplankton density, net phytoplankton density, temperature, depth, oxygen concentration and phosphorus levels, the seasonal cycles of the main species (Keratella cochlearis, Kellicottia longispina, Polyarthra remata, Polyarthra vulgaris, Cyclops spp., Diaptomus spp.) were generally similar throughout the study area. Changes in the densities of herbivorous species were poorly correlated with fluctuations in nannoplankton and net plankton availability, implying that food did not limit development. Although predatory copepods, particularly Cyclops spp., were abundant, they also had no measurable impact on the main species. It was therefore concluded that temperature controlled the seasonal cycles and the ultimate population size of most zooplankters.
Correlation Between Urea and Other Chemical and Biological Parameters in Waters of Lake Suwa, Japan
Authors: Satoh Yasuhiro , Okino Tokio , Aoyama Kanzi
Published: February 2007

The vertical profiles of chemical and biological parameters, including urea concentration, have been measured periodically since February of 1977 at a central station in Lake Suwa, which is one of the typical eutrophic lakes in Japan. The seasonal trend in the standing stock of urea in the central water column, together with the ratio of urea versus total inorganic nitrogen in the euphotic zone from 12 March, 1977 to 25 July, 1978, are presented. The possible importance of bacterial decomposition of dead phytoplankton as a urea source in natural waters is demonstrated by this study. At times, a highly significant correlation between the vertical profile of urea and vertical distributions of other chemical and biological parameters which were also measured was found. An apparent in situ utilization of urea by phytoplankton is suggested on the basis of vertical profiles of urea and other chemical and biological parameters.
Population Dynamics of the Polychaetous Annelids of an Intertidal Habitat in Upper Old Tampa Bay, Florida
Authors: Dauer Daniel M.
Published: February 2007

Following an extensive red‐tide induced mass mortality of the benthic macrofauna of a sandy intertidal habitat, the population dynamics of the polychaete species were studied. Detailed studies of the 12 most abundant species are presented. Data concerning total population levels, reproduction, recruitment, distribution within the intertidal zone, and gut content analyses are integrated in order to explain the observed spatial and temporal patterns of distribution and abundance. Potential competive interactions for food are considered to be the most important factor for explaining the observed ecological patterns. The polychaete species studied are divided into three trophic guilds: an omnivorous guild that feeds predaciously and as non‐selective deposit feeders, a surface feeding guild consisting of species usually considered to be selective surface deposit feeders, and a subsurface feeding guild usually considered as non‐selective infaunal deposit feeders. Within and between guild interactions are discussed.
Seasonal Divergence of Bosmina Morphs
Authors: Nilssen Jens Petter , Halvorsen Gunnar , Melåen Jan G.
Published: February 2007

Seasonal occurrence and vertical distribution of two sympatric Bosmina morphs were investigated in two oligotrophic, deep fjord‐type lakes. Bosmina obtusirostris and B. lacustris displayed similar ecology, but B. obtusirostris exhibited more eggs per clutch. B. obtusirostris is probably the most viable of the two morphs when fish predation is relaxed, while B. lacustris exhibits an advantage with increasing fish and invertebrate predation. This has important consequences for habitat selection of the two morphs. B. obtusirostris and B. lacustris are most probably two phenotypes of a polymorphic species.
A Brine Seep at the East Flower Garden Bank, Northwestern Gulf of Mexico
Authors: Bright Thomas J. , Larock Paul A. , Lauer Ray D. , Brooks James M.
Published: February 2007

Dissolution of Triassic‐Jurassic, intrusive salt deposits within 150 m of the sea floor produces a hypersaline brine seep (∼200 0/00) at 71 m water depth on the East Flower Garden Bank. The anoxic, sulfide‐rich brine supports large populations of sulfur oxidizing bacteria. Toxic effects of the brine on surrounding epifauna, infauna and fishes are limited to the brine and a very narrow surrounding zone. Leafy algae, coralline algae, foraminifers, sponges, bryozoans, anemones, polychaetes, sipunculids, amphipods and pelecypods live on the hard substratum within 2 cm of the brine‐seawater interface. Sixty meters from the brine outflow, at dilutions of 50 to 1, the carbonate sand harbors polychaetes, ostracods, nematodes, amphipods, tanaidaceans, isopods, copepods, pelecypods and gastropods. Certain species of fish momentarily enter the brine and brine‐seawater mixtures.
Studies on the Primary Production of Phytoplankton in Suraha Lake (Ballia, India)
Authors: Singh Shree Ram , Swarup Krishna
Published: February 2007

The paper describes the seasonal variation in the rate of phytoplankton primary production in Suraha Lake – a large shallow water body – in relation to certain physico‐chemical parameters and the abundance and composition of the phytoplankton over a period of two years.
Chromatic Adaptation of the Planktonic Blue‐green Alga Oscillatoria redekei VAN GOOR and its Ecological Significance
Authors: Kohl Johannes‐Günter , Nicklisch Andreas
Published: February 2007

Natural populations and culture strains of Oscillatoria redekei isolated from the same lakes exhibit a great variety of phycoerythrine/phycocyanine ratios even under the same growth conditions. Cytophotometric and spectrophotometric determinations of the phycoerythrine and phycocyanine contents of different strains after exposure to blue‐green and orange‐red light, respectively, suggested that chromatic adaptation of O. redekei takes place both at cellular and population level. This wide intraspecific diversity is considered at least one reason for competitiveness in highly eutrophic lakes.
Euglenophyta of Bangladesh. I. Genus Trachelomonas EHR.
Authors: Islam A. K. M. Nurul , Muniruzzaman Kh.
Published: February 2007

A total of 55 taxa belonging to Trachelomonas (Euglenophyta) are reported from Bangladesh. Of these, 5 varieties (Tr. allorgei var. madaripurense, Tr. anguste‐ovata var. ellipsoidea, Tr. armata var. rangpurense, Tr. hispida var. subcoronata, Tr. asymmetrica var. crenulata) and one forma (Tr. anguste‐ovata fa. minor) are described as new to science.
Phosphorus and Nitrogen Budgets of Barton Broad and Predicted Effects of a Reduction in Nutrient Loading on Phytoplankton Biomass in Barton, Sutton and Stalham Broads, Norfolk, United Kingdom
Authors: Osborne P. L.
Published: February 2007

Barton, Sutton and Stalham Broads are shallow, man‐made lakes formed in mediaeval times when peat excavations were flooded. Recently, a once diverse submerged macrophyte flora has, in most broads, been replaced by large phytoplankton populations. This change has been attributed to increased nutrient loadings. The seasonal cycles of chlorophyll α, nitrogen and phosphorus in the three broads are described and the inputs of nitrogen and phosphorus to Barton Broad are budgeted. A reduction in the phosphorus loading is recommended as the best method of restricting phytoplankton populations in these broads. An equation relating phosphorus loading, flushing rate, mean depth and retention coefficient to mean standing phosphorus concentration is used to predict the reduction in phosphorus loading required to limit phytoplankton populations and permit the re‐establishment of submerged macrophytes.
Reversibility of Man‐Induced Eutrophication. Experiences of a Lake Recovery Study in Sweden
Authors: Ryding Sven‐Olof
Published: February 2007

Recovery of polluted lakes is a complicated process involving many factors. Different lake rehabilitation techniques and former experiences with advanced wastewater treatment and sewage diversion are reviewed. The response in water quality after a nutrient reduction may vary significantly, despite a lowering of the phosphorus concentration in the lake. The different factors influencing the process, such as climatic fluctuations, the growth‐limiting effect of nutrients and phosphorus release from the sediments, are discussed, based on examples from a lake recovery study in Sweden carried out in 30 lakes. Due to various interrelationships between physical characteristics and biological mechanisms involved, and to significant fluctuations in these factors from one year to the next, it is difficult to generalize and to forecast the actual response of a certain water body to a reduced nutrient input. Unfortunately, too many monitoring programmes aimed at elucidating the effects of remedial efforts are not designed in such a manner that relevant information can be obtained about the nutrient load — lake response relationships. Ways for optimizing and increasing the predictive power of inventory studies and monitoring programmes are discussed.
Light Climate and Metabolism of Nitella flexilis (L.) AG. In the Bottom Waters of Oligotrophic Lake Grane Langsø, Denmark
Authors: Nygaard Gunnar , Sand‐Jensen Kaj
Published: February 2007

The irradiance reaching Nitella at 11.5 m depths was almost the same during three years: 1000 cal cm−2 year−1 PAR, or 2.2% of the surface irradiance PAR. Green light (500–600 nm) constituted most (62–88%) of the irradiance on Nitella. Net photosynthesis by Nitella was linearly correlated to irradiance. Nitella had a positive oxygen balance from mid‐May to late September and a minor negative one at other times. The annual turnover of biomass was potentially high, and the dark‐respiration was very important in the metabolic balance. The contribution of Nitella to total autotrophic production and to oxygen conditions in the hypolimnion is discussed.
A Note on the Variability of the Diatom Cyclotella meneghiniana (KÜTZ.) after Isolation from the Natural Environment
Authors: Benndorf Jürgen , Egerer Gabriele
Published: February 2007

A pure culture strain of Cyclotella meneghiniana (KÜTZ.) isolated from the hypereutrophic Bautzen reservoir (March 1980) developed from the typical Cyclotella‐shape to cells with an extremely prolonged pervalvar axis and a small diameter after five months growing under pure culture conditions. This change is interpreted as a consequence of the complete absence of grazing pressure as a selection factor. Since the cell surface/volume ratio showed a singificant increase (3.0) in comparison with the natural population (1.8), it is assumed that the culture strain has also changed with respect to physiological criteria. The conclusion is drawn that investigations of pure cultures for ecological purposes should be restricted to freshly isolated strains.
Losses of Total Phosphorus from Watersheds Influenced by Various Human Activity
Authors: Popovský Jiří
Published: February 2007

In territories without settlements, major livestock production or industry, and from territories devoted to row‐crop agriculture (diffuse pollution sources), the annual mean concentrations of total phosphorus compounds in waterways were found to be 17 to 43 μg · 1−1 P. Where there are point or hybrid pollution sources in watersheds, the annual average concentrations vary from 56 to 410 μg · 1−1 P. It was found that annual average total phosphorus concentration values obtained from three‐week sampling intervals can be used to show the presence of diffuse, hybrid and point pollution sources. The main sources of the high and permanent total phosphorus concentrations were densely populated areas, industrial works, agriculture, inadequately managed farms and disposal sites for solid and liquid wastes.
Factors Controlling the Seasonal Variation of Nitrate in Lake Erken
Authors: Boström Bengt
Published: February 2007

The seasonal variation of the nitrate concentration in the mesotrophic Lake Erken is markedly regular and shows some important differences compared with that of phosphate. Nitrification occurs mainly at the sediment surface. Nitrate accumulates when the nitrification‐denitrification sequence is broken at a time when the nitrate assimilation is small. This occurs in Lake Erken during autumn turnover.
Overwintering of Invertebrates in a Shallow Northern Swedish Lake
Authors: Danell Kjell
Published: February 2007

During two winters, the benthic invertebrates in a shallow northern Swedish lake (66 °N) were studied. The lake is ice‐covered for about 200 days a year. Live Lamellibranchiata, Oligochaeta. Hydracarina, Isopoda, Heteroptera, Cole optera and Diptera were found in samples of ice and of frozen lake‐bottom sediments. During the winter in which the bottom froze deepest, a 70–90% decrease in numbers of live Chironomidae larvae was recorded between the autumn and following early spring.
A Microflow Respirometer for Measuring the Oxygen Consumption of Small Aquatic Organisms
Authors: Scharf Eva‐Maria , Oertzen Jöro‐Andreas Von , Scharf Walter , Stave Alfred
Published: February 2007

A microrespiration device is decribed which uses a Clark electrode to measure the oxygen consumption or production of small and microscopic aquatic organisms in an open flow system. The construction and working principles of the device, which can measure oxygen consumptions as low as 0.5 nl · h−1, are described. The design of the apparatus permits parallel measurements under identical conditions with a single electrode. The device can be matched to various sizes of animal and oxygen consumption rates by means of specimen chambers of different volumes (6 μl, 35 μl, 140 μl) and a variable water flow rate. The microflow respiration device has been used successfully to measure the respiration of zooplankton and meiobenthos organisms as well as protozoans and has also been used successfully on board a research vessel.
Nitrogen Fixation in the Sediment of Shallow Lake Balaton, a Reservoir and Fishponds
Authors: Oláh J. , Abdel Moneim M. A. , Tóth L.
Published: February 2007

For the in situ measurement of nitrogen fixation in lake sediments, we developed a method which assures the rapid saturation with acetylene of the whole enzyme pool in the sediment and maintains near intact physical, chemical and biological environment at the water‐sediment interface. On the basis of seasonal measurements, the annual nitrogen fixation in the sediment was estimated in four types of shallow water ecosystem: the Keszthely Basin, Lake Balaton: 4.7 g N m−2; Körös backwater reservoir: 6.5 g N m−2; a polycultural fishpond: 0.49 g N m−2; and a liquid manure oxidation fishpond: 0.61 g N m−2. The amount of nitrogen fixed in the sediment of the Keszthely Basin was close to the fixation in the water column, while that fixed in the sediment of Körös backwater reservoir was considerably greater.

A multiple regression analysis was made on the basis of synoptic studies on the vertical distribution of nitrogen fixation in the sediment, the pH, Eh, and concentrations of organic N, NH4‐N, NO3‐N, and NO2‐N in the interstitial water. The results indicate that nitrogen fixation is related to the dep, the NH4‐N concentration, and the redox potential. The vertical distribution of nitrogen fixation cannot be explained in every case by the densities and distributional patterns of the Azotobacter and Clostridium populations. No correlation was observed between nitrogen fixation and total organic‐C in lake sediment. A surprisingly close correlation was found between plankton primary production and the sedimentary nitrogen fixation in these lakes (r = 0.85, y = 4.5 X0.85). Short‐term (4 h) in vitro studies revealed a glucose mediated increase of nitrogen fixation, but there was no NH4‐N inhibition detected during this short incubation period.
Macrobenthic Communities of the Lower Chesapeake Bay. III. Southern Branch of the Elizabeth River
Authors: Hawthorne Steven D. , Dauer Daniel M.
Published: February 2007

Macrobenthic invertebrates of an industrialized seaport ecosystem were studied seasonally from October, 1977 through July, 1978. Five stations were selected along the Southern Branch of the Elizabeth River, Virginia. The benthic community was dominated by eurytopic species that were not affected by minor to moderate stresses induced by man's activities in the seaport. Caution is required when benthic communities of the lower polyhaline to mesohaline zones of an estuary are used to indicate the effects of anthropomorphic alterations.
Ingestion Rates of Some Daphnia Species in a Shallow Lake (Lake Balaton, Hungary)
Authors: Zánkai Nóra P.
Published: February 2007

Filtering rates of three species of Daphnia were studied in situ by the 14C technique during the summer in a lake with a water temperature of 20‐25°C (Lake Balaton, Hungary). The renewal time of gut contents proved to be 3‐5 min in each of the three species whether fed on natural or artificial food. From May to September, filtering rates of D. cucullata, D. hyalina and D. galeata averaged 7.8, 10.3 and 9.2 ml ind.−1 day−1, respectively. Identically long individuals of all three species had almost the same filtering rates in spring, whereas in summer animals of identical weights had similar filtering rates regardless of species because of the length variability of the helmets. The grazing rate of adult filter‐feeding crustaceans is suggested to be approximately 7 % per day.
Biological Studies of the Pearl Spot Etroplus suratensis (Pisces, Cichlidae) from three Different Habitats in Sri Lanka
Authors: Costa H. H.
Published: February 2007

The morphometry, feeding habits and reproductive biology of Etroplus suratensis, an indigenous cichlid food fish, were studied for a period of one year on specimens from three different habitats in Sri Lanka. The morphometric studies implied that the length weight relationships are curvilinear. Macrophytic fragments formed the most important component of food, although detritus, diatoms, and animal matter are also ingested. First sexual maturity is attained in the length ranges 8.0‐9.0 cm in females from brackish water habitats. Fecundity ranged from 700‐3900 eggs in mature specimens. The wide range of the gonadosomatic index suggests that spawning occurs several times during the year.
A Study on the Macro‐Zoobenthos and the Physico‐chemical Characteristics of the Bottom of Bakhira Lake, Uttar Pradesh, India
Authors: Pandey K. , Shyam Radhey , Prasad Sant , Chaudhry H. S.
Published: February 2007

Bakhira Lake is the largest man‐made lake of Eastern Uttar Pradesh. It is utilized for Boro (coarse paddy) cultivation, irrigation and fishing by poor village farmers. Hydrographical features, qualitative and quantitative composition of the macro‐zoobenthos, and the physico‐chemical characteristics of the bottom water and sediment were studied from October 1976 to April 1977.

Molluscs, insects, ostracods, annelids, nematodes and crustaceans are the main groups of zoobenthos. Molluscs together with insects dominate the benthic fauna (95.2 to 96.4% of numbers). The benthic density varied from 273 to 517 individuals/m2. Average density of macro‐zoobenthos is more or less inversely related to the total alkalinity of the bottom water. Molluscs showed a positive correlation to temperature and a negative correlation to insect density.
How Currents on Different Sides of Substrates in Streams Affect Mechanisms of Benthic Algal Accumulation
Authors: Stevenson R. Jan
Published: February 2007

Benthic diatom accumulation rates and diversity were monitored for 32 days in five habitats where current conditions were different. After 32 days, diatom abundance in a sheltered habitat where eddies occurred over substrates was over eight times the abundance in a habitat that was exposed directly to the main flow of the stream (about 30 cm/sec). Diatom immigration rates and species richness of diatom taxocenes were negatively related to exposure; whereas, diatom reproduction rates, death rates and relative abundances of the eight dominant diatom species were not related to the small differences in current velocity that occurred. During the 32‐day colonization period diatom immigration rates increased, species richness of diatom taxocenes increased and evenness of species abundances decreased. Species composition of diatom taxocenes shifted from a numerical dominance by fast immigrators to dominance by fast reproducers during the 32‐day colonization.
Interactions between Light Situation, Depth of Mixing and Phytoplankton Growth during the Spring Period of Full Circulation
Authors: Horn Heidemarie , Paul Lothar
Published: February 2007

Investigations lasting several years at the artificial Lake Saidenbach have shown that, due to the poor light situation expressed in terms of average daily radiation (Riley 1957), mean daily exposure (Reynolds 1973), extinction depth and the ratio zmis/zeu, no mass development of the phytoplankton should actually occur during the spring complete circulation. In practice, however, the period of complete circulation of the water in spring is not only a prerequisite for, but often also the factor causing, the mass development (usually Asterionella formosa). The poor light situation and the fact that the vertical phytoplankton profile shows significant differences between the plankton concentrations at different depths indicate that the spring complete circulation does not represent a complete recirculation, and thus mixing, of the water down to the bottom but involves only episodic and local partial recirculations interspersed with periods of relatively slight turbulence. The actual mixing depth during this period of complete circulation is therefore obviously less than the mean depth of the water concerned, which is commonly assumed to equal. This permits the algae in the upper layers to grow. Respiratory losses of the phytoplankton at greater depths probably remain slight due to their adaptation to low light intensities in winter.
Development and Use of an Aquatic Micro‐Ecosystem as a Test System for Toxic Substances. Properties of an Aquatic Micro‐Ecosystem IV
Authors: Kersting Kees
Published: February 2007

Experiments were performed using several modifications of a micro‐ecosystem made up of three subsystems connected by a unidirectional flow of recirculating water. The three subsystems represent roughly the trophic levels of autotrophs (algae), herbivores (Daphnia magna), and decomposers (sandfilter with bacteria). The particle concentration was determined weekly, using a Coulter Counter, and the Daphnia population was counted. At regular intervals, the species composition of the algae was determined. The changes in the algal concentration and Daphnia population are described, and the different modifications are discussed.

In several micro‐ecosystems, the herbicide dichlobenil was introduced once or several times, and in one micro‐ecosystem, the herbicide diuron was added. The response of the micro‐ecosystems is discussed. For the periods without a toxic substance present, a normal operating range is suggested in relation to which the response of the systems to the introduced herbicide is discussed.

Besides the separate analysis of the data, the algal concentrations and the Daphnia numbers were correlated to each other. This was done by regression analysis and according to a dynamic system approach. In both cases, the effect of herbicides was better discerned than in the separate analysis of the data. In the dynamic systems approach, a normalized ecosystem strain was defined as a parameter to measure effects of stress on the ecosystem level.
Comparison of Plankton‐Water Chemistry Relationships in Three Acid Stressed Lakes in Nova Scotia, Canada
Authors: Blouin Anthony C. , Lane Patricia A. , Collins Terrance M. , Kerekes Joseph J.
Published: February 2007

A field program was conducted in 1980 and 1981 on three lakes in Kejimkujik National Park, Nova Scotia, to study plankton‐water chemistry relationships in a region of potential acid precipitation stress. Among lake and between year comparisons were made.

The three study sites represent two different types of lakes. Kejimkujik Lake (pH 4.8) and Pebbleloggitch Lake (pH 4.5) are both high‐colored, dystrophic acid lakes. Beaverskin Lake is a clear, oligotrophic lake which is not as acidic (pH 5.4).

The phytoplankton of Kejimkujik Lake was dominated by diatoms, while Pebbleloggitch Lake was dominated by chlorophytes and chrysophytes, and Beaverskin Lake was dominated by cyanophytes. Kejimkujik Lake had the highest total algal cell volume per liter, and Pebbleloggitch Lake the lowest.

Rotifer populations composed the majority of the zooplankton communities, while the crustacean zooplankton were dominated by the acid‐tolerant copepod Diaptomus minutus. Kejimkujik Lake had the lowest zooplankton biomass and Pebbleloggitch Lake the highest zooplankton biomass per m3. A pattern of highest algal density in Beaverskin Lake, but highest zooplankton density in Pebbleloggitch Lake emerged in both years. This is likely an effect of abundant, but unsuitable food (blue‐green algae) in Beaverskin Lake and important detrital food resources in Pebbleloggitch Lake in both years.

Multiple regression analysis of water chemistry variables with plankton species produced many significant effects, but failed to show clear patterns. Cause and effect relationships in aquatic ecosystems are poorly delineated by such techniques.
Composition and Productivity of the Benthic Macroinvertebrate Community of a Subtropical Reservoir
Authors: McCullough Jack D. , Jackson Douglas W.
Published: February 2007

Physical‐chemical conditions, phytoplankton productivity, community structure and productivity of the macroinvertebrate benthic community were determined during 1976–77 in a subtropical reservoir. Physical‐chemical results revealed high nitrate and phosphate concentrations with highest values in the riverine segment. Large phytoplankton populations were present during most of the year. Phytoplankton productivity was high, producing an annual mean of 87 mg C · m−3 · h−1 (12 hours light day). High turbidity in the riverine segment limited phytoplankton productivity during winter and spring. Macrobenthos was dominated by chironomids (Chironomus, Procladius, Coelotanypus and Tanypus) and oligochaetes (Limnodrilus). The annual mean benthic population was estimated at 1,626 · m−2 with a mean dry weight of 0.66 g · m−2. Mean benthic species diversity was 1.80. A lacustrine‐riverine community gradient was revealed. Benthic productivity was 6.8 g · m−2 · yr−1 (dry weight) with a P: B ratio of 10. A low correlation was observed between benthic and phytoplankton productivity, and between phytoplankton standing crop and benthic macroinvertebrate numbers throughout the reservoir. Algal food supplies had little impact on the benthic community which was composed predominately of species which fed mostly on organic detritus. Stressful conditions caused by low dissolved oxygen concentrations probably inhibited development of the benthic community throughout the reservoir during summer months, while high sedimentation rates limited development in the head waters.
The Effects of Hydraulic Dredging to Control Oyster Drills on Benthic Macrofauna of Oyster Grounds in Delaware Bay, New Jersey
Authors: Ismail Naim S.
Published: February 2007

This study describes the extent and nature of the effects of hydraulic dredging to control oyster drills (Urosalpinx cinerea and Eupleura caudata, Family Muricidae, Order Neogastropoda) on benthic macrofauna and sediments of the oyster grounds in Delaware Bay, New Jersey. The immediate effects of hydraulic dredging were reductions in numbers of species as well as in total numbers of animals on the three oyster grounds selected. However, oyster drills were most affected. Benthic populations have recovered three to ten months after dredging. The sediments of the dredged grounds can be described as muddy sands. Immediately after dredging, additional mud was brought up from subsurface layers which reduced the median grain size on Ground 154 test plot. On Ground 515 test plot, however, there was a slight loss in the mud which increased the median grain size.
Competition and Population Time Lags in Bosmina (Cladocera, Crustacea)
Authors: Matveev Vladimir
Published: February 2007

The competition between Bosmina coregoni and B. longirostris was studied by culturing of mixed and isolated populations in lake water. While interaction was detectable between the two species, they were capable of coexisting for at least 124 days. The pattern of predominance was found to depend on initial frequencies. The ratio of B. coregoni to B. longirostris in the pelagic zone of a mesotrophic lake could be explained on the basis of competition between either species. Birth, death, and population growth rates proved to be delayed functions of stock density, as was borne out by cross‐correlation analysis of experimental population dynamics. Time lag estimates for all three rates varied for different phases of population oscillation. For accurate assessment of time lags, the phases of monotonous changes in density should have been separated from one another. The time lag estimated for the rate of population growth in mixed cultures was significantly higher for the superior competitor (B. coregoni). This estimate may well be predicted as an arithmetic mean value cf time lag estimates for birth and death rates. The duration of population growth (or decline) was correlated to the time lag of the death rate, whereas the amplitude was not correlated to any time lag at all.
Influence de la spéciation du cuivre sur les populations phytoplanctoniques naturelles de la rivière du Saguenay, Québec, Canada Influence of Copper in Various Forms on Natural Phytoplanktonic Populations from the Saguenay River, Quebec, Canada
Authors: Thompson Patsy‐Ann , Cǒté Raynold
Published: February 2007

In 1981, experiments to study the toxicity of copper in its ionic, complexed (to humic acid) and adsorbed (on cellulose fibers from a local paper mill) forms on species composition, standing crop, and photosynthesis of phytoplankton were conducted in chemostats with natural aggregations composed mainly of either green algae or of diatoms from the Saguenay River. In the aggregations of green algae, the rates of primary production were more strongly inhibited by copper than were the chlorophyll a concentrations, whereas the cell numbers, standing crop and rates of primary production of the diatoms were all strongly inhibited by copper.
Application of Videomicroscopy to the Study of Interstitial Fauna
Authors: Farris Richard A. , O'Leary Daniel J.
Published: February 2007

This paper deals with a method of employing videomicroscopy in the study of meiofauna. The apparatus is inexpensive, easy to use, and offers a high degree of resolution. Accurate measurements of the specimen can be made directly from the video monitor screen. With the addition of a videocassette recorder, live footage can be recorded for analysis, correspondence, or as an aid in teaching.