bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Relations of Vertical Distribution, Diurnal Migration and Nutritional State of Herbivorous Zooplankton in the Northern North Sea during FLEX 1976
Authors: Krause Michael , Radach Gunther
Published: February 2007

At a fixed station in the northern North Sea the occurrence of herbivorous and omnivorous zooplankton and the changes in its vertical distribution were studied over 2 1/2 months during the spring phytoplankton bloom in 1976.

From a sporadical distribution of relative few plankton organisms in the mixed water column at the end of winter, in the middle of April a significant accumulation of organisms began to occur in the upper layers parallel to the development of stratification and the phytoplankton spring bloom. As exceptions, the populations of Microcalanus pusillus and Metridia lucens withdrew to below the thermocline.

About ten days after the decline of the phytoplankton bloom, a few zooplankton species—especially wax ester producing copepods like Calanus finmarchicus, Pseudocalanus elongatus, Microcalanus pusillus, aad Metridia lucens—started diurnal vertical migrations. The movements of the species and stages occurred synchronously, leading in the same direction. Nevertheless, the amplitude of the migrations increased with each maturity stage reached.

The vertical migrations, characterized by actual locations and velocities of the centers of gravity of the populations, are interpreted in terms of metabolism leading to fat storage, decomposition and reconstruction of lipids and proteins, in terms of a periodical change in the density of the organisms.

Further data sets about the vertical distribution of organisms are cited to support the hypotheses stated.
Sedimentation Studies on Gandhisagar Reservoir
Authors: Rao K. S. , Kartha K. N. , Shrivastava S.
Published: February 2007

The sedimentation data of Gandhisagar Reservoir is presented and discussed. About 4.3 % gross capacity of Gandhisagar Reservoir was lost due to accelerated sedimentation from 1962 to 1975. Grain size analysis shows that the sediment consisted of 40.80 percent clay, 51.99 percent silt, 6.30 percent sand, 1.12 percent gravel. Suitable measures to prevent sedimentation are suggested.
Seasonal Dynamics of a Chironomus plumosus (L.) (Diptera, Chironomidae) Population from a Fish Pond in Southern Bohemia
Authors: Maténa Josef
Published: February 2007

A population of Chironomus plumosus (L.) from a fish pond has been investigated for two years. Quantitative benthic samples and emergence traps were used to study the seasonal dynamics. Effect of some factors on the duration of development was studied in laboratory experiments. Data on larval abundance, length frequency analysis and emergence of adults suggest a bivoltine life cycle. The population of C. plumosus investigated showed a pronounced tendency to dormancy, even under long‐day conditions. Factors regulating the bivoltine life cycle are discussed.
Experimental Approach to the Role of Different Ecological Types of Protozoa in the Activated‐sludge System
Authors: Macek Miroslav
Published: February 2007

Relationship between bacteria and ciliates was investigated in continuous cultures with and without the recycling of flocculated biomass. Monocultures of ciliates of various ecological types were used together with mixed cultures of bacteria or bacteria and flagellates. The effect of ciliates on the distribution of flocculated and dispersed, biomass was tested with respect to characterizing an optimum mixed culture for activated‐sludge treatment. Monoprotozoal populations were not successful in stabilizing the morphology of a bacterial community in a system with recycling of flocculated biomass. Stabilization was observed (with particular ecological types of ciliates) in the system with a high residence time without recycling and/or in the system with the recycling inoculated by both flagellates and ciliates.
Werner Schnese and the Development of Coastal Waters Ecology in Rostock, GDR
Authors: Schiewer Ulrich
Published: February 2007

A survey of ecosystem research in brackish coastal waters (Baltic Sea) by the Department of Biology, University Rostock (GDR) is given. Using selected results the main goals are demonstrated, outgoing from the first steps initiated by W. Schnese.
The Chydorid Crustacean Alona diaphana (King), Limnetic in Lakes Awasa and Zwai, Ethiopia, with a Discussion of Littoral and Limnetic Zooplankton
Authors: Fernando C. H. , Belay Semeneii , Mengestou Seyoum
Published: February 2007

Alona diaphana, a common littoral tropicopolitan cladoceran, occurs in the limnetic of two Ethiopian lakes in considerable numbers and over long periods of time. Our results are presented and the composition of limnetic and littoral zooplankton, in terms of previous records of such incursions, are discussed. The high persistent densities of A. diaphana are due to the extensive littoral areas in the lakes, where it originates, the high intrinsic rates of increase of this species, the low diversity of zooplankton, reducing competition and the low level of predation.
Seasonal Changes in the Chemical Composition ofCeratophyllum demersumL. in a Small Pond
Authors: Pip Eva , Philipp Klaus
Published: February 2007

Seasonal content of total soluble carbohydrate, total soluble protein, free fatty acids and alkaloids were examined in a population ofCeratophyllum demersumgrowing in a pond on the southwestern edge of the Canadian Shield. Total soluble carbohydrate and total soluble protein were inversely correlated. Free fatty acids were dominated by (16:0 + 16:1), 18:2 and 18:3. Relative proportions of the different free fatty acids remained roughly constant throughout the season. Alkaloid concentrations showed large fluctuations, with the highest values found during the first half of the season. Carbohydrate and protein contents of associated periphyton were not correlated with host macrophyte metabolism.
Reliability of Analyses of Hg, Fe, Ca, K, P, pH, Alkalinity, Conductivity, Hardness and Colour from Lakes
Authors: Håkanson Lars , Borg Hans , Uhrberg Roland
Published: February 2007

The aim of this report has been to present results concerning analytical quality controls of Hg analysis of fish and sediment, analyses of Fe, Ca, total‐P, K, pH, alkalinity, conductivity, colour and hardness (Ca + Mg) of lake water samples. Despite the fact that these are standard parameters in many regular water control programs, there are major differences in the reliability with which these parameters can be determined. The focus here is on an overall inter‐laboratory comparison between the parameters. Six laboratories have been involved in the analysis. Selected results: pH gives the lowest (average) relative standard deviation (error), about 2 %; conductivity gives an error of about 5–7 %; alkalinity yields an average error of as much as 13–25 %, which is the largest among the parameters studied here; colour also gives a high error, 9–15 %; hardness gives a relative standard deviation of about 6–7 %. Of the other parameters (i. e., Hg, Fe, Ca and P), Hg gives the best reliability and Fe and P the lowest. To have knowledge of the reliability of the analytical data is of paramount importance in most control programs and research projects.
Growth and Production of Yellow Eels and Glass Eels in Ponds
Authors: Breteler J. G. P. Klein , Dekker W. , Lammens E. H. R. R.
Published: February 2007

Two experiments (I and II) were performed in drainable ponds. Yellow eels Anguilla anguilla (L.) were stocked in early June at three biomasses: 10, 20 and 60 kg · ha−1 in experiment I; and 10, 20 and 40 kg · ha−1 in experiment II. The mean body weights were 27.0 and 24.2 g respectively. Glass eels were stocked only in experiment II at equal densities of 1600·ha−1. In both experiments each biomass of yellow eel was combined in a factorial design with three cyprinid communities differing in biomass and in species‐ and size‐composition. The ponds were drained in autumn. The final body weights at draining ranged from 25.9 to 63.6 g for yellow eel and from 3.9 to 8.8 g for glass eel. The final body weights of yellow eel and of glass eel decreased with increasing biomass of yellow eel. No significant relation was found between the bream Abramis brama (L.) biomass and the growth of eel. The growth rates of yellow eel and glass eel were positively correlated in experiment II. At higher biomasses of yellow eel the percentage females decreased slightly. The recapture rates of yellow eel in experiments I and II amounted to 69.4 ± 9.8 % and 92.2 ± 4.9% (mean ± sd) respectively. The lower recapture rates in experiment I were caused by the inappropriate draining technique used. The glass eels were recaptured with 75.0·5.6% efficiency. The maximum net production of yellow eel occurred at a biomass of 20–40kg·ha−1 and amounted to 19 kg·ha−1.
Comparison of Spectrophotometric, Fluorometric and High Performance Liquid Chromatography Methods for Determination of Chlorophyll a in Aquatic Samples: Effects of Solvent and Extraction Procedures
Authors: Jacobsen Timothy R. , Rai Hakumat
Published: February 2007

Chlorophyll a determinations were made on lakewater and algal samples by spectrophotometric, fluorometric and high performance liquid chromatographic methods. Acetone, methanol and ethanol solvents were evaluated for their ability to extract photosynthetic pigments from Scenedesmus sp. cultures. Routinely used methods overestimated the chlorophyll a concentrations present in the samples. Significant differences resulted when various standard equations were used to calculate chlorophyll a concentrations. Acetone did not quantitatively extract chlorophyll pigments, even after 24 h. Mechanical disruption was found to be important in assuring complete extraction of the chlorophyll pigments.
Studies of Aquatic Fungi. XIII. Mycoflora of the River Czarna Hańcza and its Tributary, the River Marycha
Authors: Czeczuga Bazyli , Brzozowska Krystyna , Woronowicz Lucyna
Published: February 2007

The authors investigated the mycoflora and the environmental factors in the River Czarna Hańcza (10 stations) and its tributary River Marycha (1 station) as well as Lakes Hańcza (2 stations) and Wigry (2 stations) on the occurrence of various aquatic fungi.

At the stations investigated the presence of 45 aquatic fungi species was noted. The following fungi, up to now unknown in Poland, were found:Monoblepharis hypogyna, Rozellopsis inflata, Cladolegnia eccentrica, Apostemidium guernisaci, Anguillospora gigantea, Geniculospora grandis, Clavariopsis aquatica, Lemonniera aquaticaandLemonniera terrestris.
The Variation in the Acidity of Ground and Surface Waters in Northern Ireland
Authors: Jordan C. , Enlander I. J.
Published: February 2007

The distribution of surface and ground waters in Northern Ireland were mapped with respect to pH and total hardness and the distributions discussed in relation to the regional geology and pedology. These waters were grouped into 3 categories depending on their vulnerability to acidification. Three upland areas, the Mournes, the western Sperrins and the northern Glens of Antrim, were identified as being vulnerable to acidification. Concentrations of total and labile aluminium in these areas were high and, in the Mournes and Sperrin areas, exceeded the EC directive on total aluminium in drinking water. However, because of their differing geology and pedology, only the Mournes area had labile aluminium levels which gave cause for concern. A fish survey in a reservoir in the Mournes catchment showed that it supported a small but self‐sustaining population of brown trout (Salmo trutta) which, although small in size, showed no signs of deformity.
Les Invertébrés Planctoniques du Lac Volvi (Macédoine, Grèce). The Planktonic Invertebrates of Lake Volvi (Macedonia, Greece)
Authors: Zarfdjian M. H. , Vranovský M. , Economidis P. S.
Published: February 2007

The planktonic invertebrates found in Lake Volvi are presented. There are 26 species of Rotifera, 1 Bivalve (larva), 13 Cladocera, 5 Copepoda, 1 Branchiura and 1 Diptera (larva). Many of these are new for the Greek fauna, though they are common in Europe. The discovery of some other species extends the knwown bounds of their geographical distribution in Greece.

The lack of large‐sized forms is considered to be due to strong predation by Alosa macedonica. (Pisces, Clupeidae). A comparison is given to the planktonic invertebrates of other Balkan lakes. There is a remarkable similarity with the fauna of Lake Doïrani.
Growth of Blue‐Green Algae in the Saidenbach Reservoir and its Relationship to the Silicon Budget
Authors: Horn Heidemarie
Published: February 2007

The phytoplankton succession during the summer in the mesotrophic reservoir Saidenbach since 1975 may well be explained by the resource ratio hypothesis. Until 1980, only phosphorus controlled the phytoplankton growth, and diatoms prevailed, because an excesses of silicon existed. From 1981 to 1986, the ratio Si:P often was smaller than 90, a value, critical for the development of the diatom Fragilaria crotonensis. Its reduced growth caused an increased occurrence of blue‐greens (mostly Aphanothece clathrata) immediately after the diatom mass development. During these years at first silicon limited phytoplankton growth in summer, later on the growth again was limited by phosphorus.

Because of increased Si and P load since 1987 a simultaneous limitation of both nutrients occurs. This leads now to parallel mass developments of diatoms and blue‐greens.

In order to maintain the positive effect of diatoms (phosphorus transport into the sediment), it is to guarantee a sufficiently high Si:P ratio. If a reduction of P load isn't possible, Si remobilization from the sediment could be increased by artificial changes of the water level.
Biomass and Functional Distribution According to the Feeding Modes of Two Freshwater Protozoan Communities
Authors: Fernandez‐Leborans Gregorio , de Zaldumbide Mercedes Castro , Perales Carolina
Published: February 2007

The study has been made concerning the composition of and the relationships among: physico‐chemical factors, abundance, number of species, biomass, heterotrophic and photoautotrophic components, and functional groups with regard to the feeding patterns of a river‐reservoir system. The most outstanding results concerning the system as a whole are: 1, a relationship exists between the biomass of protozoa and the biomass of ciliates; 2, the most important functional groups, in terms of the number of species, are group III (ciliate “downstream” filter feeders) and group IV (ciliate “upxtream” filter feeders), and in terms of the abundance of specimens, the most important ones are groups III and V (raptorial feeders); 3, the division into functional groups according to feeding modes is similar in the river and the reservoir studied. This correlation is quite significant with regard to the number of species, the abundance of specimens, and between the samples taken from the two areas.
The Distribution of Perkinsus marinus in Gulf Coast Oysters: Its Relationship with Temperature, Reproduction, and Pollutant Body Burden
Authors: Wilson Elizabeth A. , Powell Eric N. , Craig M. Alison , Wade Terry L. , Brooks James M.
Published: February 2007

Oysters from 48 Gulf of Mexico sites were examined for presence and infection intensity of the endoparasite, Perkinsus (= Dermocystidium) marinus (Mackin, Owen and Collier, 1950) as part of NOAA's Status and Trends Mussel Watch Program. Prevalence exceeded 75% at 25 sites. Infection intensity did not vary with sex or reproductive stage. Latitude, total polynuclear aromatic hydrocarbon (PAH) content and industrial and agricultural land use significantly affected the parasite's distribution. PAH and pesticide concentrations were latitudinally dependent, suggesting an impact of spawning frequency on uptake and depuration. P. marinus analysis complements the use of pollutant body burden for determining change in environmental quality because it responds differently than pollutant body burden to the biology and ecology of the oyster.
Results to the Ecology of Endangered Species of Fish and Cyclostomes from Three Streams of Northern and Central Germany
Authors: Spiess Hans‐Jürgen , Waterstraat Arno
Published: February 2007

Research into endangered species of fish and cyclostomes, as well as their living environment, are prerequisite to determining species protection measures.

Relevant ecological research was carried out in three streams in the trout and grayling region; the environmental conditions were recorded, and the populations characterised.

Consequently the following suggestions for the protection of the streams dealt with in this research can be made.
Spatial and seasonal distribution of heterotrophic bacteria in pond water and sediments under different management practices
Authors: Jana B. B. , De U. K.
Published: February 2007

Population densities and generation time of heterotrophic bacteria were estimated in water and sediments of fish ponds used for polyculture, monoculture and traditional systems of fish farming over a period of two and a half years. Spatial differences in microbial densities in the ponds were related to the organic loadings of the farm site and farm management. A number of environmental factors such as nitrogen, dissolved organic carbon, bicarbonate and phosphate of water were found to be responsible for the seasonal changes of heterotrophic bacteria in these ponds.
Immigration of Young Eels to the Skagerrak‐Kattegat Area 1900 to 1989
Authors: Hagstrom Olle , Wickström Håkan
Published: February 2007

The decline in recruitment of glass eels, elvers and young yellow eels to the Skagerrak‐Kattegat area in Sweden was demonstrated by catch data from trawl hauls at sea (IKMWT) and from eel ladders in two rivers emptying in the Kattegat. A long term decline since the 1940's was indicated and the same short term decrease as observed in other European countries during the 1980's was proved.
Observations on the Silver Eel Migrations of the Burrishoole River System, Ireland, 1959 to 1988
Authors: Poole W. Russell , Reynolds Julian D. , Moriarty Christopher
Published: February 2007

The eel migrations in Burrishoole, Ireland, have been studied from 1959 to 1988. Numbers of eels in the catches have decreased. The mean length of male eels has increased by 16.5% and females by 27.6%. Total weight of catch has not been affected by the drop in numbers. A change in sex ratio from 94.5 % males in 1962 to 37.5% in 1988 has also occurred. A decrease in elver recruitment into freshwater and a change in the environmental status of the system are discussed as being possible reasons for these changes.
A Proposal Regarding the Source of Nutrition of Leptocephalus Larvae
Authors: Westeberg Håkak
Published: February 2007

The large size, transparency and peculiar dental configuration of leptocephalus larvae can be interpreted as adaptations to a diet of large, transparent and soft food items. It is suggested that gelatinous zooplancton, in particular the discarded house of the Appendicularia or Larvacea, is their main food. Calculations show that an ingestion rate of the order of magnitude 10 houses/ hour is sufficient to sustain an eel larva.
Optimization of Weaning Elvers in a Closed Cycle System: Preliminary‐Results
Authors: Bronzi P. , Zaffignani P.
Published: February 2007

Replicated tests to study the best combination of environmental conditions were carried out with a total of about 200 kg of glass eels of the Thyrrenian sea. Conditions tested were; stocking density, feed formulation, form of feed, grading frequency, cage and tank dimensions and protection of rearing units. Production and survival rates are reported, as well the size — class distribution at the beginning and at the end of the rearing period and the component chart of percentages of different size classes.
Short Note on a Culture Experiment on Monthly Captured Glass Eels from the Rio Minho, Portugal
Authors: Weber Michael , Antunes José Carlos
Published: February 2007

A recycling system combining biofiltration and hydroponics was used for rearing glass eels. Growth rates varied between 0.1 and 1.4% of body weight per feeding day. A large range of mortalities (9.4—93 %) after two months was mainly due to ectoparasitic infections.
Interrelations between Microcystis and Cladocera in the highly Eutrophic Lake Kasumigaura, Japan
Authors: Hanazato Takayuki
Published: February 2007

The zooplankton community in the highly eutrophic Lake Kasumigaura was investigated and its relation to a bloom of Microcystis was analyzed. The zooplankton community was dominated by small cladocerans, whose biomass and production became highest in summer, when Microcystis bloomed. The high cladoceran production is considered to depend on the production of colonial Microcystis, because the production of nannoplankton was apparently too low to ensure the cladoceran production. Microcystis cells were unsuitable as food for the cladocerans inhabiting Lake Kasumigaura, but became utilizable when decomposed. Decomposed Microcystis may be the main food for Cladocera in the lake in summer. High water temperatures occurring in summer probably promoted decomposition of the Microcystis, leading to increased production of the small cladocerans.
Strain‐specific Influence of Microcystis Aeruginosa on Food Ingestion and Assimilation of some Cladocerans and Copepods
Authors: Henning Manfred , Hertel Heino , Wall Henry , Kohl Johannes‐Günter
Published: February 2007

Ingestion rates where estimated for daphnids, Cyclops spp. and Bosmina (Eubosmina) coregoni thersites fed hepatotoxic and non‐toxic M. aeruginosa either separate or mixed with the readily available food alga Ankistrodesmus falcatus. The ingestion rates of hepatotoxic strains of M. aeruginosa are very low compared with those of A. falcatus or non‐toxic M. aeruginosa HUB 5‐3 fed to Daphnia magna or D. longispina. However, a close relationship between ingestion rate of different M. aeruginosa strains and their toxicity could not be observed. Addition of the toxic strain M. aeruginosa HUB 5‐2‐4 reduces the ingestion rates of A. falcatus progressively due to increased food rejection by D. magna. Additionally, the assimilation efficiency of M. aeruginosa HUB 5‐2‐4 is two times lower compared with A. falcatus and M. aeruginosa HUB 5‐3 leading to strong starvation.
The Influence of Extracellular Algal Products on the Surface Tension of Water
Authors: Nägeli Astrid , Schanz Ferdinand
Published: February 2007

By means of laboratory experiments and field investigations in Lake Zürich, the influence of extracellular algal products on the surface tension of water was investigated. Of interest to us was the question of whether a reduction in the surface tension, i.e. surface pressure, is dependent on (i) algal species or phytoplankton and phytoneuston community, (ii) the growth phase of the species or community concerned, and (iii) the abundance or concentration of phytoplankton and phytoneuston biomass. A dependence was ascertained in the case of the first two points. The laboratory experiments showed that extracellular products originating from diatoms give rise to a distinctly higher surface pressure than those originating from green and blue‐green algae; and that the change in surface pressure occurs during the later part of the stationary algal growth phase. In Lake Zürich, high values of surface pressure were measured at the time of the collapse of the diatom bloom, and comparatively low values during the period of dominance of the blue‐green alga Oscillatoria rubescens in the winter months. Changes in surface pressure established during the course of a year can thus be explained partly in terms of the phytoplankton and phytoneuston succession.
Besonderheiten bei der Ermittlung der Primärproduktion in der Elbe aus Sauerstoff‐Ganglinien. Some Particularities in Estimating Primary Productivity in the River Elbe Using Oxygen Time Curves
Authors: Böhme Michael
Published: February 2007

The phytoplanktonic primary production was estimated in the River Elbe (average flow 325 m3/s) byODUM's twin and single curve analysis of changes in the oxygen content (1‐ and 2‐ SGA). The results were affected by the severe and varying waste water load and the non‐uniform conditions along the upstream river stretch.

It is shown how the gross primary productivity was corrected by using the photosynthesis‐light‐relationship. At favourable measuring sites, single curve analysis gives similar values asODUM's twin curve method. But they scatter more when applied to establish the photsynthesis‐light‐relationship.
Characterization of Brackish Coastal Waters of Different Trophic Levels by Means of Phytoplankton Biomass and Primary Production
Authors: Wasmund Norbert , Kell Volkbert
Published: February 2007

Investigations on phytoplankton have been carried out in Baltic coastal waters, which are widely separated from the sea. Corresponding to their distance to the sea they differ in their trophic level. Annual phytoplankton production and a mean biovolume of 100‐200 g C · m−2 and 2‐10 mm−3 · 1−1 respectively were found for the mesotrophic level, of 200‐400 g C · m−2 and 10‐20 mm3 · 1−1 for the eutrophic level, and of 400‐600 g C · m−2 and over 20 mm3 · 1−1 for the polytrophic level.

In the course of nearly two decades of investigation a slight increase of phytoplankton biovolume, but no increase of primary production was recorded. Some changes in species composition are to be recognized in Greifswalder Bodden, if old literature is compared with recent data. In the Darss‐Zingst boddens a shift from Cyanobacteria dominance towards Chlorophyceae dominance has appeared for at least 5 years. This was on account of the disappearance of Gomphosphaeria pusilla, which is thought to be an indicator species of the mesotrophic level.
Influence of Eutrophication on Bacteria in Two Fjords of the Western Baltic
Authors: Gocke Klaus , Rheinheimer Gerhard
Published: February 2007

Longitudinal transects in the Schlei Fjord (Kiel Bight) revealed strong increases of microbiological parameters from the entrance towards the landlocked end of the fjord. In the inner part up to 14 × 106 bacteria ml−1 (microscopical count), 77 × 10−1 saprophytic bacteria ml−1 (plate count) and a thymidine incorporation rate of 0.436 nmol 1−1 h−1 were observed. The data were compared with earlier results from the same system and those from the nearby located Kiel Fjord. The observations indicate a very high degree of eutrophication in the Schlei Fjord and a lesser one in the Kiel Fjord. The significance of total bacterial numbers and numbers of saprophytic bacteria as indicators for eutrophication and contamination is discussed.
Seasonal Variation in the Biomass of Zooplankton in Two Shallow Coastal Water Inlets Differing in their Stage of Eutrophication
Authors: Heerkloss R. , Schnese W. , Adamkiewicz‐Chojnacka B.
Published: February 2007

The seasonal zooplankton dynamics of two coastal water inlets differing in their stage of eutrophication are compared. There are no clear differences between the two waters with respect to calanoid copepods, but they differ appreciably in terms of rotifer biomass. In the more eutrophic water the latter show a pronounced mass development in July which is absent in the less eutrophic water. It is concluded that bacterio‐detritivorous rotifer species are an important regulative factor of the ecosystem which compensates for productivity increases by intensifying heterotrophic destruction.
Autotrophic Picoplankton in Freshwater Ecosystems: The View from the Summit
Authors: Stockner John G.
Published: February 2007

A brief overview of the state‐of‐the‐art of freshwater autotrophic picoplankton (APP) is given as an introduction to this special issue of Internationale Revue der gesamten Hydrobiologie. Some questions that have arisen from research over the past decade are re‐evaluated in light of new information reported here. These include: 1.) what is the average abundance of autotrophic picoplankters along a nutrient gradient in freshwater?; 2.) how diverse and what are the major components of the APP community in freshwater?; 3.) what is the origin of colonial forms of picoplankton?; 4.) what is the significance of prokaryotic and eukaryotic picoplankton in pelagic systems?; and 5.) how important is grazing in APP population regulation? New questions are proposed and an outlook for possible future research is offered.

“Creating a theory … is rather like climbing a mountain, gaining new and wider views, discovering unexpected connections between our starting point and its rich environment. But the point from which we started still exists and can be seen, although it appears smaller and forms a tiny part of our broad view gained by mastery of the obstacles on our adventurous way up”
Determination of Eubacterial and Cyanobacterial Size and Number in Lake Baikal Using Epifluorescence
Authors: Boraas Martin E. , Bolgrien David W. , Holen Dale A.
Published: February 2007

Chroococcoid cyanobacteria, (mean size = 0.79 μm, likely Synchetocystis limnetica Popovsk) and total eubacteria (mean size = 0.33 μm), from Lake Baikal, USSR, were enumerated using epifluorescence microscopy and sized with image analysis. Bacterial densities ranged from 0.44 · 106 cells ml−1 at 250 m to 2.3 · 106 cells ml−1 at the surface. Mean eubacterial abundance was 1.3 · 106 cells ml−1. Cyanobacterial densities were more variable, ranging from 0.42 · 104 cells ml−1 at 250 m to 9.8 · 104 cells ml−1 at the surface, with a mean abundance of 2.7 · 104 cells ml−1. The cyanobacteria, in particular, occurred in clusters resembling “marine snow”. Our results indicate that Lake Baikal picoplankton size and density are similar to other large lakes but may have a more diverse community structure than in other large oligotrophic lakes.
Seasonal Changes in Chlorophyll‐containing Picoplankton Populations of Ten Lakes in Northern England
Authors: Hawley G. R. W. , Whitton B. A.
Published: February 2007

Key features of photosynthetic picoplankton populations were compared during 1988 in ten lakes in northern England ranging from oligotrophic to slightly eutrophic; two of the three eutrophic lakes were shallow and lacked a thermocline. Measurements were made at 0.5 m depth of temperature, total chlorophyll a, chlorophyll‐containing picoplankton cell density, mean picoplankton cell volume and percentage of phycoerythrin‐rich cells in the total picoplankton population. All lakes showed maxima for total chlorophyll concentration and picoplankton cell density in mid‐ to late summer. The maximum value for picoplankton density ranged from 3.4 × 103 (Esthwaite Water) to 1.3 × 106 cells ml−1 (Ennerdale Water).

There was a significant negative relationship (p < 0.05) between log10 of maximum picoplankton cell density and maximum total chlorophyll, the latter being taken as an indicator of lake trophic status. The ratio of maximum to minimum picoplankton density during the year in a particular lake ranged from 39 to 2360 and showed no obvious relationship to lake type. Overall, the seasonal range in picoplankton density was about one order of magnitude greater than the range in total chlorophyll a, but there were considerable differences between lakes.

Phycoerythrin‐rich picoplankton as a percentage of total picoplankton reached a maximum in summer in all lakes. Values were always very low (<5%) in the two shallow eutrophic lakes, but reached 97% and over in the four most oligotrophic lakes. In two of the oligotrophic lakes, Wast‐water and Ennerdale Water, phycoerythrin‐rich picoplankton was a major component of the summer phytoplankton biomass.
Occurrence, Dynamics and Production of Picoplankton in Hungarian Shallow Lakes
Authors: Vörös Lajos , Gulyás Pál , Németh József
Published: February 2007

Phototrophic picoplankton were detected in 105‐106 cells/ml concentrations in seven water bodies of differing chemistry and trophic level. Dominant picoplankters were, at all sites, coccoid cyanobacteria of 0.8‐1.2 μm dimensions, exhibiting red or yellow autofluorescence. Apart from the effects of water temperature their quantitative dynamics were significantly influenced by the nitrogen supply and the herbivorous zooplankton (Cladocera). Their maximum contribution to the total planktonic primary production was about 50%, both in mesotrophic and hypereutrophic environments. However during the bloom of filamentous nitrogen‐fixing blue‐greens their role became negligible. In phytoplankton communities the significance of picoplankton is overestimated several times, when based on the cell count, while it is underestimated on the basis of biomass. The most useful characteristics of phytoplankton size groups was the total surface area of their cells.
Carbon‐14 Uptake by Picoplankton and Total Phytoplankton in Eight New Zealand Lakes
Authors: Petersen Richard
Published: February 2007

Eight New Zealand lakes were surveyed for 14C uptake by phytoplankton as a function of light intensity. The results support the view that the photosynthetic picoplankton is an important contributor to primary productivity in oligotrophic lakes but is relatively unimportant in more eutrophic lakes. A comparison of carbon uptake vs. light intensity characteristics (P vs. I) of the picoplankton size class vs. that of the total phytoplankton community supports the view that the picoplankton size class may be adapted to utilization of dimmer light.
Diel Division Cycle and Growth Rates of Synechococcus in Lakes Huron and Michigan1
Authors: Fahnenstiel Gary L. , Patton Tyrone R. , Carrick Hunter J. , McCormick Michael J.
Published: February 2007

A clone of Synechococcus isolated from Lake Huron and natural populations of Synechococcus from lakes Huron and Michigan were studied in 1989 to examine the diel division cycle and to provide estimates of the in situ growth rate based on the frequency of dividing cells (FDC) method. Cultured populations of Synechococcus exhibited a consistent diel division pattern with a midday/afternoon (1100–1800 h) peak in the percent of dividing cells. The maximum percent of dividing cells varied among cultures (8‐27%) and was related to the growth rate. A small fraction of dividing cells (3‐5%) remained throughout the dark period, suggesting that some cells were arrested in the doublet stage prior to division. The duration of division (td) ranged from 2.6‐4.9 h, with a 3.7 h mean for cultures with growth rates ≥0.34 d−1 but increased to 8 h at a lower growth rate of 0.20 d−1.

The diel division pattern for natural populations was very similar to the laboratory clone; an afternoon peak (1400‐2100 h) in dividing cells and a small fraction of dividing cells (2‐5%) remained during the dark period. The maximum percent of dividing cells for natural populations ranged from 6‐10%. In situ growth rates, determined from the FDC and assuming a constant td of 3.7 h, ranged from 0.30‐0.42 d−1. The FDC method may provide accurate estimates of in situ growth, particularly in environments where the growth rate is >0.34 d−1, but in lakes Huron and Michigan where growth rates can be lower and td values may increase, FDC‐growth rates must be viewed with caution.
The Nitrogen Cycle in Lough Neagh, N. Ireland 1975 to 1987
Authors: Gibson C. E. , Smith R. V. , Stewart D. A.
Published: February 2007

Results from thirteen years of weekly observations are presented on the nitrogen cycle in Lough Neagh. The data comprised catchment and atmospheric inputs, output via the outflow and calculated losses by sedimentation and denitrification. Nitrate‐nitrogen in the rivers is the dominant input fraction and the nitrate loading has increased over the period observed. 52 % of the input N sediments to the lake bottom, but 65 % of this is lost by denitrification. In spite of increasing nitrogen inputs, the summer soluble nitrate concentrations have decreased due to uptake by a perpetual crop of the cyanobacterium Oscillatoria agardhii GOMONT.
Growth of Bream, Abramis brama L., in Two Outside Basins of Different Trophic State of Lake Balaton
Authors: Dauba Francis , Biró Péter
Published: February 2007

Age‐composition, size‐distribution, length/weight relationships and growth both in length and weight of bream stocks were studied on fishes collected in NE and SW basins of Lake Balaton during 1982/83. Stocks consisting of 10 to 12 age‐groups were observed at the two lake areas. The linear growth and weight‐gain in the SW‐basin were annually faster than in the NE‐basin, however, the growth of bream in Lake Balaton was slow as compared to that observed 10 years ago. Parallel with progressive eutrophication, the density of bream stocks increased by some 5–10 % especially at hypertrophic lake areas (SW) and consequently their growth was transformed to densitydependent. In the appearance of strong year‐classes some cyclicism could be observed especially in the SW‐basin.
Zu den Ursachen der unterschiedlichen pH‐Empfindlichkeit von Gammarus pulex L., G. fossarum KOCH (Amphipoda) und Aselus aquaticus L. (Isopoda)
Authors: Rupprecht Rainer
Published: February 2007

By means of ion chromatography the extensive and significantly higher loss of ions of G. pulex and G. fossarum in acid water (pH 3.0) as compared to neutral water is proved. While cations are being accumulated in the water, some ions (Na+, Cl−) leave the hemolymph in important percentage, others increase highly after being set free from the cells (K+ and Ca2+). The loss of cations with Asellus aquaticus in acid water (pH 3) is clearly lower than with Gammarus, and it is not significantly higher than when the animals are put into neutral water.
Herbivores and the Spatial Distributions of the Phytoplankton III. Estimating the Number of Good Foraging Places
Authors: Wirick Creighton D.
Published: February 2007

During critical periods, the survival of a herbivorous zooplankter or ichthyoplankter may depend upon the animal encountering food in excess of a critical concentration. During such times, the value of the animal's habitat is related to the relative number of places where food exceeds the critical concentration. CHEBYSHEV'S mathematical inequality gives a nonparametric upper bound for the probability that a place selected at random from a habitat will contain such excess food. The probability is proportional to the sum of the variance and mean squared of the food distribution, which is also a measure of the habitat's value to the animal.
Colonization, Species Composition, and Conidial Production of Aquatic Hyphomycetes on Chirpine Needle Litter in a Freshwater Kumaun Himalayan Stream
Authors: Sati S. C. , Tiwari N.
Published: February 2007

Aquatic hyphomycetes colonizing the submerged chirpine (pinus roxburghii SARG.) needle litter in a high altitude, Kumaun Himalayan stream were studied. 15 species belonging to different genera of aquatic Hyphomycetes have been recognized as the colonizers of chirpine needle litter. Clavariopsis aquatica, Heliscus lugdunensis, Lunulospora cymbiformis, Triscelophorus acuminatus and T. monosporus were found with a high frequency of occurrence. The conidial production was highest in Flagellospora penicillioides, however, Campylospora chaetocladia, L. cymbiformis and T. acuminatus had less number of conidia per unit area of pine needles. The chirpine needle litter decomposition in the freshwater habitat is also discussed.
Metacyclops minutus (CLAUS, 1863) ‐ Population Dynamics and Life History Characteristics of a Rapidly Developing Copepod
Authors: Maier Gerhard
Published: February 2007

The cyclopoid copepod Metacyclops minutus, a typical species of temporary pools, shows an unusual life cycle in a small pond in South Germany. The species is present from April/May to December during which period it forms at least 8 generations. Winter and early spring, when the pond is frozen to the bottom, are spent in the bottom mud as C4 or C5 instars. M. minutus shows an extraordinarily low degree of sex size dimorphism (female: male body length ratio) and no significant differences in. copepodite development time between the two sexes. This, together with the exceptionally short durations of embryonic‐ and postembryonic development enables reproduction to start without delay and rapid population growth after harsh conditions. By these means M. minutus is the first species to reproduce after periods of extremely low water level; later, when conditions in the pond become more stable, M. minutus is surpassed in numbers by a coexisting, filterfeeding and parthenogenetically reproducing cladoceran Moina brachiata.
Relationship of Sponge Macrofauna with the Morphology of their Hosts in the North Aegean Sea
Authors: Koukouras A. , Russo A. , Voultsiadou‐Koukoura E. , Dounas C. , Chintiroglou C.
Published: February 2007

The associated macrofauna of four Aegean Sea sponge species (Agelas oroides, Petrosia ficiformis, Ircinia variabilis and Aplysina aerophoba) was compared. The total number of individuals and species was found to be related to sponge volume for all sponge species.

The associated macrofaunal weight per individual on all sponge species was negatively correlated with sponge volume. Sponge complexity, as measured by sponge surface area to biomass ratio, was not a consistent predictor of associated macrofauna abundance or diversity. Sponge macrofauna species were not host specific and their relative abundances differed among sponge species.
Comparison of Two Methods of Zooplankton Grazing Measurements
Authors: Nőges Tiina
Published: February 2007

A comparison of two methods of zooplankton feeding experiments was performed in the Gulf of Finland. One was the advanced twin‐bathometer method (in situ technique), the other — the “bottle method”. The main difference between the two methods is that it is not necessary to manipulate zooplankton to start an experiment in a twin bathometer, while manipulation is inevitable if the second method is used. In cases when the onset of the grazing experiment requires the manipulation of animals, the adaptation period lasts 2–4 hours and the optimal duration of experiment is 6–10 hours. If animals are not manipulated at the beginning of experiment, the adaptation period does not exist, the exposition time should not exceed 10 hours and the optimal duration of experiment is 2–4 hours. In long‐term experiments (up to 24 hours) the fertilization effect of the excretion of concentrated zooplankton may cause underestimation of grazing rate.
Postglacial Succession in the Subgenus Eubosmina (Crustacea: Cladocera) in the Region of the Unterhavel River (near Berlin, Germany) — Type Changes or Species Immigration?
Authors: Günther Jutta , Lieder Ulrich
Published: February 2007

Analyses were made of subfossil Eubosmina remains from two Berlin Lakes. The first postglacial eubosminid was B. (E.) longispina. In Tegeler See it occurred from the Alleröd to Atlantic 2. In Lake Unterhavel it disappeared earlier in the Boreal. Bosmina (E.) longicornis occurred in early Atlantic 1 resp. at the end of Atlantic 2 (Tegeler See). Bosmina (E.) c. coregoni appeared in Lake Unterhavel at the end of the Boreal, in Lake Tegeler See at early Boreal. Bosmina (E.) c. thersites occurred only in sediments of Lake Unterhavel beginning in Atlantic 2.

No sign of a “morphological transition” between taxa found by HOFMANN could be found in the two investigated lakes. The succession of Eubosmina taxa seems to be mainly the result of immigration.
Zooplankton Migration in Three Lakes of Western New York
Authors: Stewart Kenton M. , Sutherland James W.
Published: February 2007

We examined the diel vertical migration (DVM) of zooplankton in three lakes of western New York; Lakes Conesus, Lime, and McCargo. In all three lakes, the dipteran predator Chaoborus was a more dramatic migrator than any of the cladocerans or copepods. In contrast, another invertebrate predator, Leptodora, seemed to have the least vertical dispersal. In Conesus Lake, following the evening ascent and upper‐water night‐positioning of Chaoborus flavicans, Daphnia pulicaria expanded its own vertical range of dispersal thereby decreasing its degree of overlap with Chaoborus. The vertical distribution of Diaptomus sicilis was mostly below that of Daphnia pulicaria, thus reducing possible competition for food resources. Poor oxygen conditions in the lower waters of Lakes Lime and McCargo restricted all zooplankton (except Chaoborus) to an epilimnetic zone where the regions of niche overlap and predation were narrowed. Such annually‐induced restrictions on vertical dispersal are probably common features of numerous stratified lakes with hypolimnetic reducing conditions. No fixed pattern of vertical dispersal or migration is likely in lakes where stratification and non‐stratification follow each other seasonally. Vertical migration does provide some flexibility in niche separation, but the potential for chaotic behavior in interacting predators and prey may confound simple explanations of DVM.
A Model to Predict Lake Water Colour
Authors: Håkanson Lars
Published: February 2007

This study is an attempt to quantitatively determine variables of significance for predicting colour in small glacial lakes. Lake colour is an important variable in many lake ecological contexts. The data emanate from two extensive data‐sets from Sweden, one of which concerns 1456 lakes, and the other 91 more well‐suited lakes. Four year average values of lake colour were compared to catchment and morphometric parameters to help identify the processes which influence variability in colour between lakes. Various hypotheses concerning the factors regulating colour in lakes were formulated and tested. Various statistical tests were used to separate random influences from causal influences. Those “map parameters” with the most significant influence on colour were the theoretical lake water retention time, the percent of rocks, lakes and mires of the drainage area, the ratio between lake area and drainage area and the lake mean depth. Each model parameter provides only a limited explanation (statistical) of the variability in colour between lakes. The predictability of colour by these models can not be markedly improved by accounting for the distribution of the characteristics in the drainage area. The stability of the final model, which gives an r2‐value of 0.74, has been tested with positive results. The model allows lake colour to be estimated from knowledge of “geological” characteristics of the lake and its drainage area. The variability between lakes from other factors, such as temperature, precipitation and/or contamination of acidifying substances and nutrients, may then be quantitatively differentiated from the impact of these “geological” factors.
Organic Matter, Carbon, Nitrogen and Phosphorus Contents of the Mesozooplankton, Mainly Acartia clausi, in a Tropical Brackish Lagoon (Ebrié Lagoon, Ivory Coast)
Authors: Pagano Marc , Saint‐Jean Lucien
Published: February 2007

Mesozooplankton samples were collected over a period of one year in five stations of the Ebrié lagoon and analysed for organic, carbon, nitrogen and phosphorus contents. When zooplankton was dominated by A. clausi, body composition was relatively stable compared with the broad variability of environmental factors (mainly salinity, food abundance and composition), although a negative hypothetic influence of salinity may have occurred. Body composition was comparable when zooplankton was dominated by Pseudodiaptomus hessei and freshwater species, but contents were significantly lower for assemblages dominated by more exclusively marine species (Paracalanus spp., Oithona spp., marine cladocerans, chaetognates, etc.).
Acute Toxicity for some Evaporating Aromatic Hydrocarbons for Freshwater Snails and Crustaceans
Authors: Erben Radovan , Pišl Zoran
Published: February 2007

Some typical and more frequent freshwater invertebrates of running waters were studied to examine the influence of styrene, xylene and benzene on their mortality. Snails Amphimelania holandri FÉR. and Lymnaea stagnalis L. and crustacenas Asellus aquaticus L. and Gammarus fossarum KOCH., were used in the semi‐static test. Compounds were added in volume concentrations of 0.005 to 0.4% v/v. For all concentrations LC50 was calculated by probit method, which demonstrated that mortality depends much more on increased concentrations (depending on the initial concentration) than on the length of exposure. Styrene was the most toxic, followed by xylene and then benzene. The species G. fossarum showed marked sensitivity, followed by A. aquaticus, and the species A. holandri and L. stagnalis showed less sensitivity.