bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Importance of Planktonic Protozoans in the Eutrophication Process of the Baltic Sea
Authors: Arndt Hartmut
Published: February 2007

Analysing the results of various authors recent studies in the pelagic region of the Baltic revealed that protozoan biomass is in the same range or even higher than metazooplankton biomass. The dominant groups of planktonic protozoans are heterotrophic pico‐ and nanoflagellates (various taxonomic groups), large heterotrophic flagellates (mainly dinoflagellates) and ciliates. Regularly the spring bloom of phytoplankton is accompanied by a maximum of protozoan biomass which declines in early summer as a result of intensive grazing pressure by metazooplankton and changing food conditions. The analysis of results from different stations indicated that biomasses of protozoans increase with an increasing degree of eutrophication. Several trophic levels within the microbial web should be added to the traditional view on the pelagic food web of the Baltic. Our knowledge regarding the quantitative aspect of the microbial matter flux of the Baltic is very limited up to now and complex ecological (and taxonomical) studies using standardized methods including all protozoan components are necessary. Protozoans (various trophic groups and levels), besides bacteria, should be viewed as the metabolically most active heterotrophic component in the pelagic region of the Baltic, their activity should increase with an increasing degree of eutrophication.
Temporal and Spatial Variability of Zoobenthic Communities in Archipelago Waters of the Northern Baltic Sea‐Consequences of Eutrophication?
Authors: Bonsdorff Erik , Aarnio Katri , Sandberg Eva
Published: February 2007

A large‐scale spatial (52 sampling stations in two areas; one previously affected by numerous sources of enrichment, and one pristine area used as a standard reference for coastal monitoring) and temporal (1972‐1989) analysis of hydrography and benthic macrofauna in the archipelago waters of Åland, northern Baltic Sea, revealed significant changes of the ecosystem. The nutrient levels exceeded the criteria for eutrophicated waters at all stations, and the benthic macrofauna showed significant alterations in all parameters analyzed. In the area previously (1972‐73) disturbed, reduced complexity in terms of diversity and evenness (i.e. functional responses) were recorded, whereas the changes in the previously undisturbed area are classified as structural. The main conclusions are that (a) no truly “natural” coastal reference areas can be found in the northern Baltic, and (b) the importance of the local effluents will add to the large‐scale effects of eutrophication.
Ecological Characteristics of Autotrophic Picoplankton in a Prealpine Lake
Authors: Weisse Thomas , Kenter Ulrich
Published: February 2007

The seasonal distribution of autotrophic picoplankton in Lake Constance was investigated over four consecutive years. Cell numbers varied seasonally and vertically over four orders of magnitude (102 to 106 cells ml−1). A horizontal variation by a factor of 3 in abundance and biomass across the different parts of the lake was found during summer stratification. Picoplankton peaks occurred during the phytoplankton spring bloom and in late summer. Low values were characteristic for the clear‐water phase in early summer and for autumn‐winter. This seasonal pattern differed from that of larger phytoplankton in Lake Constance and from the seasonal distribution of picoplankton known from other lakes and marine environments. Picoplankton was predominated by chroococcoid cyanobacteria of about 0.6 μ3 biovolume. The average cell size increased from winter until early summer. Using HPLC pigment analysis, we identified zeaxanthin and β‐carotene as typical picoplankton pigments. Results of the pigment analyses suggest that algae others than picocyano‐bacteria may be more prominent in the picoplankton size class than derived from routine epifluorescence counting.
Phototrophic Picoplankton in Temperate Lakes: Seasonal Abundance and Importance along a Trophic Gradient
Authors: Søndergaard Morten
Published: February 2007

The seasonal development of autotrophic picoplankton was investigated in seven Danish lakes representing a eutrophication gradient. Highest cell abundance between 1.5 to 6 × 105 cells ml−1 were found in mid‐summer. Minor peaks were observed in spring. In winter, densities were below 103 ml−1. The highest relative picoplankton contribution to total autotrophic biomass also occurred in mid‐summer. In the eutrophic lakes and one humic lake the average seasonal contribution of picoplankton to total chlorophyll was below 1% increasing to 5‐8% in the meso‐ and oligotrophic clear water lakes. During short periods the proportion of picoplankton did reach 25%. The higher relative importance of picoplankton in less productive lakes was not due to higher actual chlorophyll concentrations, but due to a much more pronounced response by larger algae at higher nutrient loading. Both cyanobacteria and eukaryote organisms were present as picoplankton. Only eukaryotes were found in one eutrophic lake and an acidic, humic lake. In the eutrophic lakes eukaryote picoplankton was dominant; both with respect to cell densities and biovolume, whereas cyanobacteria dominated the two meso‐oligotrophic lakes. Autotrophic picoplankton were present in all lake types, however their importance seemed to be less in most eutrophic lakes than in less productive, meso‐oligotrophic lakes.
Picocyanobacteria and Bacteria in Lake Kinneret
Authors: Malinsky‐Rushanksy Nehama , Berman Tom
Published: February 2007

In Lake Kinneret, we have been monitoring the numbers and depth distributions of bacteria and picocyanobacteria since early 1988. Picocyanobacteria were found throughout the year at all depths, at concentrations ranging from < 103 to 105 cells·ml−1. Highest abundances were recorded during summer and fall in the epilimnion. The lowest areal standing stocks occurred from March to May, the period which corresponds to the peak of the annual dinoflagellate bloom. Bacterial numbers ranged from about 105 to 107 cells·ml−1. The picocyanobacteria were evenly distributed in the water column during the mixed period. With the onset of thermal stratification and the end of the dinoflagellate bloom the numbers of picocyanobacteria increased rapidly in the epilimnion.
Red Fluorescing Phototrophic Picoplankton in the Laurentian Great Lakes: What Are They and What Are They Doing?
Authors: Fahnenstiel Gary L. , Carrick Hunter J. , Rogers Clare E. , Sicko‐Goad Linda
Published: February 2007

Epifluorescence microscopy, flow cytometry, and transmission electron microscopy were used to characterize the community of red fluorescing (emission >665 nm when excited with blue light) phototrophic picoplankton (RFPP) in lakes Huron and Michigan. A population of coccoid to ovate eukaryotic cells with a mean size of 1.2 μm dominated the RFPP community in both surface and deep water samples. Abundant prochlorophyte populations were not found in any samples. Comparisons of counts with epifluorescence microscopy and flow cytometry, revealed that RFPP were adequately enumerated with standard epifluorescence microscopy. These RFPP were significant contributors to total phototrophic picoplankton abundance in both lakes Michigan (24%) and Huron (18%), with maximum seasonal abundance during the May‐June period (surface mixing layer temperatures, 3‐9 °C). During thermal stratification, maximum vertical abundance was found in the metalimnion/hypolimnion at the 1‐5% isolumes. RFPP were only minor contributors (1‐7%) to total primary production. Growth rates of RFPP measured with dilution and small inocula growth experiments ranged from 0.05‐1.0 d−1. Microzooplankton grazing rates on RFPP measured with dilution experiments were similar to estimated growth rates, accounting for 52‐280% of growth on any given date.
Nutrient and Grazer‐Mediated Effects on Picoplankton and Size Structure in Phytoplankton Communities
Authors: Wehr John D.
Published: February 2007

This study examines the factors which contribute to the abundance of algal picoplankton in lakes. A three‐year field study of a meso‐eutrophic lake was compared with observations from oligotrophic and highly eutrophic lakes in the region. Trophic state alone (oligotrophic vs. eutrophic) was not a good predictor of the importance of picoplankton; smaller cells were relatively abundant when phosphorus was limiting other phytoplankters, but also when nitrogen was in surplus. Subsequent field experiments found that picoplankton growth was stimulated by N, but not by P additions. This relationship was strongly affected by light and grazer levels. Grazers apparently mediate the effects of nutrient deficiency, and favor the growth of larger algal size classes, especially nanoplankton. The flux of P within experimental enclosures was controlled by picoplankton abundance under low nutrient conditions, but was a function of total phytoplankton biomass under P surplus.
Nitrogen Loss and Denitrification as Studied in Relation to Reductions in Nitrogen Loading in a Shallow, Hypertrophic Lake (Lake Søbygård, Denmark)
Authors: Jensen Jens Peder , Jeppesen Erik , Kristensen Peter , Christensen Peter Bondo , Søndergaard Martin
Published: February 2007

A detailed mass balance on nitrogen was carried out in shallow and hypertrophic Lake Søbygård during 4.5 years before through 2.5 years after a 36 % reduction in nitrogen loading. Annual mean loss rate of nitrogen was 159–229 mg N m−2 d−1 before the loading reduction and 125 mg N m−2 d−1 after. In spite of a short hydraulic retention time (18–27 days) the proportion of nitrogen loading lost in the lake was high (38–53 %) and not affected by changes in loading. Calculated denitrification accounted for 86–93% of the loss rate, while 7–14% was permanently buried. Marked seasonal variations in the loss percentage were found during the season, ranging from 23 % in first quarter to 65 % in third quarter. The seasonal variation in the loss percentage of nitrogen showed a hysteresis like relationship to temperature, with a high percentage in fourth quarter. This suggests that the amount of available substrate, which mainly consists of sedimentated phytoplankton, accumulated during summer, is an important regulating factor. The ability of various published input‐output models to predict the observed changes in in‐lake nitrogen concentration in Lake Søbygård was tested. This study has further confirmed that small lakes with short retention and high nitrogen loading may significantly reduce the nitrogen loading of downstream aquatic environments.
Nitrogen Accumulation, Productivity and Stability of Reed Stands (Phragmites australis (CAV.) TRIN. ex STEUDEL) at Different Lakes and Sites of the Lake Districts of Uckermark and Mark Brandenburg (Germany)
Authors: Küshl Harald , Kohl Johannes‐Günter
Published: February 2007

The extent of decline of reed belts (Phragmites australis) during last decades has been established by using aerial photographs of the mesotrophic lake Parsteiner See and the eutrophic lake Müggelsee. Final standing crop and nitrogen accumulation within the above‐ground plant biomass of 15 different sites of 8 lakes correlate with nitrogen availability indicated by both dissolved nutrient content of the sediment and nitrogen content of biomass during the main growth period. Reed stands well supplied with nitrogen show high shoot loss and compensatory tiller growth till late in the season. Some results demonstrate a delayed switching from the vegetative phase to the generative one and lowered allocation of reserve material to the rhizome as at least one of the factors responsible for lowering stability of the reed beds.
Chemical and Microbial Binding Forms of Phosphorus Considering the Availability of Nitrate in Sediment‐Water Systems
Authors: Andrusch T. , Hupfer M. , Luther D.
Published: February 2007

An analytical registration of P‐transport processes in intact sediment cores from the shallow reservoir Radeburg II (near Dresden, Saxonia, Germany) was possible by application of KH232PO4 and followed by sequential P‐fractionation (PSENNER et al. 1984). Under oxygen free conditions and sufficient nitrate supply an activity accumulation was found in the uppermost sediment horizon. Nitrate influences above all the BD‐fraction (reductant soluble P), so that an interaction between nitrate and the iron binding system could be proved. It could be shown by means of activated sludge (a model object for microbial polyphosphate accumulation from a lab plant qualified for biological P‐ and N‐elimination) that added KH232PO4 was bound within 5 h to about 75 % in the NaOH‐fraction. The saturation of iron compounds in the activated sludge took place immediately after KH232PO4 had been added. In the same time the portion of the microbial immobilization of added 32P amounted to 7 % in the high‐iron sediment from the Radeburg reservoir, whereas evidently in the heat‐ and HgCl2‐sterilized sediments this portion was additionally ascertained in the BD‐fraction, too.
Seasonal Periodicity in Lacustrine Phytoplankton and the Theory of Ecological Succession
Authors: Amblard C.
Published: February 2007

An attempt has been made to examine the extent to which seasonal periodicity of lacustrine phytoplankton corresponds to the general concepts of the theory of ecological succession. The study was carried out on an eutrophic lake (Aydat, France). As REYNOLDS (1980, 1984) suggests, the seasonal periodicity of phytoplankton is an autogenic succession which may be perturbed by allogenic physical processes that change the initial direction of the succession. Thus, in this lake, only spring succession of phytoplankton can be considered as a true succession, consistent with the theory of ecological succession in that it was a directional and predictable phenomenon leading to an increasing complexity of community.
Anti‐predator Defence in Three Daphnia Species
Authors: Pijanowska Joanna
Published: February 2007

Over a two‐year period, each of the three Daphnia species in two lakes with different pressure by fish and invertebrate predators exhibited different defensive reactions: predator avoidance in space (Daphnia hyalina), seasonal morphological changes (Daphnia cucullata), and a combination of both (Daphnia cristata). Body size and general susceptibility to predation, combined with predators' preferences were most likely responsible for the kind of defence in each of the three Daphnia.
Structural Compositions of Pelagic Communities in the River Warnow and their Changes
Authors: Schumann Rhena , Sievert Catrin , Schiewer Ulrich
Published: February 2007

The phytoplankton and heterotrophic microbial communities from the Oberwarnow and Unterwarnow were analyzed from November 1987 to May 1988. The production potential of the microorganisms was quantified in laboratory experiments. On the average, phytoplankton accounted for 73 % of the total biomass in the Oberwarnow and 59 % in the Unterwarnow. The corresponding figures for bacterial biomass were 24 % and 33 %, respectively. If the nutrient supply is unlimited and phytoplankton biomass predominates, the development of primary producers in eutrophic to polytrophic waters is not regulated by metazooplankton. Top‐down regulation is possible only if prevailing conditions limit the growth of the dominant phytoplankton species.
Secondary Production of Macrobenthic Invertebrates from Delaware Bay and Coastal Waters
Authors: Maurer Don , Howe Stavros , Leathem Wayne
Published: February 2007

Secondary production of benthic invertebrates was estimated for Delaware Bay and coastal Delaware. Production and turnover ratios were highest in Delaware Bay (P = 46,572 mg AFDW m−2 yr−1, P:B = 6,O) and progressively lower at two coastal stations (P = 7,501 to 30,124 mg AFDW m−2 yr−1, P:B = 2.3 to 5.3, and P = 4,485 to 4,492mg AFDW m−2 yr−1, P:B =2.3 to 4.8). Production was inversely related to sediment particle size. Production in Delaware Bay was relatively evenly distributed between deposit feeding polychaetes and suspension feeding molluscs with a definite shift in production dominance to suspension feeding molluscs at the coastal stations. Moreover, crustaceans and echinoderms played a larger role in production at the coastal stations than in Delaware Bay. Concerns about the health of soft‐bottom communities in Delaware Bay expressed earlier were not supported here. Finally, it was concluded that P and P: B from the Delaware Bay area were very similar to those obtained from other areas in the North Atlantic which agrees with estimates for other estuaries in the northern hemisphere.
Zooplankton Associations in the Middle Niger‐Sokoto Basin (Nigeria: West Africa)
Authors: Jeje C. Y. , Fernando C. H.
Published: February 2007

The species richness of the crustacean zooplankton (Cladocera and Copepoda) and Rotifera in the Middle Niger‐Sokoto Basin is characterised from 351 samples collected from 109 localities. 26(4) Cladocera, 18(8) Copepoda and 38(8) Rotifera are recorded. Figures in brackets indicate first records of species for Nigeria. Zooplancton associations of the Middle Niger are compared with one of its major tributaries, River Sokoto, and seven of its minor tributaries using similarity indices of Sørensen and Pearsons Product Moment Cluster Coefficients. The Rivers Sokoto and Shagari consistently had the highest similarity of zooplankton associations, for all combinations of rivers studied with r = 0.54 (Cladocera), r = 0.91 (Copepoda) and r = 0.54 (Rotifera). Zooplankton associations of the Middle Niger are weakly correlated with all tributaries studied (r < 0.1). Species composition and hydrology of the River Sokoto Basin are also compared with previous studies in Nigeria. A Principal Component Analysis of species abundance accounted for 54 % of the total variance. It again confirmed the similarity of the branches Sokoto and Shagari. Two groups of species assemblages were identified. The occurrence of Asplanchna sp., Testudinella patina and Microcyclops varicans in one group appears related to microhabitat selection. The other group made up of Brachionus calyciflorus calyciflorus, Macrothrix spinosa, Lecane luna, Thermocyclops decipiens and Metacyclops minutus is suspected to be linked to physico‐chemistry. Further studies on the hydrology and physico‐chemistry are required for definitive identification of both factors.
Die Trichoptera‐Emergenz im Mittellauf eines Bergbaches des Thüringer Waldes (Insecta, Trichoptera)
Authors: Mey Wolfram
Published: February 2007

Fifty‐seven species of caddisflies were identified in samples taken over a 7‐month period from a large emergence trap placed on the mid‐reach of a forested mountain stream in the Thuringian Forest, East Germany, in 1984. A total of 4,673 specimens were obtained during the sampling period. The community was dominated by collectors and shredders (52 % and 35.6 % of biomass) indicating a high input of allochthonous organic material from the bank trees as well as from upper stretches of the stream. The emergence periods and patterns of the common species are described and compared. Some species showed significant departures from a balanced sex‐ratio. An explanation is proposed to account for the general unpredictability of sex‐ratios in emergence traps. Unusual emergence patterns of 5 species are discussed in detail.
Species Composition and Habitat Preference of Watermolds in the Nainital District of Kumaun Himalaya, India
Authors: Mer G. S.
Published: February 2007

A total of thirty two species of watermolds have been identified from the entire study area. Of these, 22 % species were restricted to water, 44 % to soil and 34 % occurred in water and soil both. The maximum number of species were found during rainy season in both the ecosystems. Pythium s pp. were dominant in terrestrial ecosystem whereas Pythium s pp. and Saprolegnia spp. were dominant in water system. There were two clusters indicative of presence of two distinct communities in both the systems.
The Structure of Molar Surfaces of the Mandibles of Sidoidea (Crustacea: Daphniiformes). 1. Holopediurn gibberum ZADDACH, 1848
Authors: Glagolev Sergey M. , Korovchinsky Nikolay M.
Published: February 2007

The morphology of mandibles of Holopedium gibberum was studied using scanning electron microscopy. They are strongly asymmetric and differ with that of Anemia and Podonidae and similar with that of Branchinecta and Daphniiformes especially Penilia.
Deep‐sea Environmental Disturbance and Recovery Potential
Authors: Thiel Hjalmar
Published: February 2007

Mining the abyssal seafloor for manganese nodules will destroy the hard substrate and it will severely disturb the seabed and the benthic soft substrate community. Recolonization will occur from unmined areas. Reestablishment of a community similar to that originally present is, however, not possible, since the nodules will be removed and epigrowth on hard substrates is thereby precluded. Small scale experiments using azoic sediment in trays exposed to ambient deep‐sea conditions, may not be appropriate models for large scale recolonization processes.

Results of such experiments and general knowledge of deep‐sea ecology suggest that decades may be required for reestablishment of a balanced community.

With respect to evaluation of some ecological consequences of mining an ongoing large scale experiment, termed DISCOL (DIS‐turbance and re‐COL‐onization) is shortly described as a new approach in deep‐sea risk assessment.
Hydrobiological Studies on Suraj Kund and Chandrama Kund, Hot Springs of Rajgir, Bihar, India
Authors: Jha Mahendra
Published: February 2007

The hot water of Rajgir springs is used for drinking and bathing purposes by tourists. Certain physico‐chemical characteristics (temperature, pH, NO, PO, etc.) of the water along with phycological parameters viz. community composition, species diversity, standing crop etc. were measured from June 1986 to April 1987. The water was deficient in Na, NO and PO ions. The hot springs were mainly dominated by algae belonging to Cyanophyceae and Bacillariophyceae. The algal community comprised 18 species, with dominance of Cyanophyceae over Bacillariophyceae. While Mastigocladus laminosus and species of Phormidium were dominant in Suraj Kund, species of Oscillaroria and Synechococcus dominated in Chandrama Kund. Diatoms comprised about 10 % of the algal community. Though there was a considerable seasonal change in species diversity of the algal community the total biomass (chlorophyll a extracted per unit area from the algal mat) remained constant.
Considerations on Representative Water Quality Data
Authors: Håkanson Lars
Published: February 2007

The aim of this paper is to give a brief summary concerning important methodological aspects in establishing the reliability of empirical water quality data. These considerations are relevant for applied work e.g. monitoring programmes, as well as theoretical research, e.g. to validate models. The paper concerns data from Swedish lakes on Hg in pike, perch, water and sediments, and a broad set of limnological data (pH, Secchi depth, temperature, alkalinity, total‐P, conductivity, Fe, Ca, hardness, chlorophyll‐a and colour). These standard parameters generally vary in a lake, both temporally and areally. The focus of this paper is on such variations and how to express lake‐typical values. There are large differences in analytical reliability for different parametres; e.g. Hg (in fish and sediments but not in water) and lake pH can generally be determined with a comparatively great accuracy; the average relative standard deviation (V) is only about 2‐3% for pH. Colour, Fe‐, total‐P‐concentration and alkalinity, on the other hand, generally give high V‐values. In natural lakes, the variability is often at least twice as large as the “methodological” variability for parameters such as colour, P, Fe and alkalinity (V‐values ranging between 20 and 40% on average in our lakes). This implies that for most parameters one must analyse many samples to obtain representative, lake‐typical values with a given statistical reliability. A general furmula expressing how many samples are required to establish lake‐typical mean values is discussed as well as statistical aspects concerning the range of empirical data in models based on such data.
Nutrient Interactions and Phytoplankton Growth during the Spring Bloom Period in Lake Erken, Sweden
Authors: Eriksson Cecilia , Forsberg Curt
Published: February 2007

Factorial enrichment experiments with nitrate‐N, phosphate‐P and selenite‐Se, were conducted in situ, with natural phytoplankton assemblages, during two consecutive spring‐bloom periods (1983 and 1984) in Lake Erken, Sweden. Nutrient conditions, biomass indicators and algal physiological status, in experiments and in lake water, were compared. Characteristic peaks of phytoplankton, dominated by diatoms, developed in the lake in both years. In 1984, chlorophyll a biomass (30 μgl−1) reached almost twice that of 1983 (17 μgl−1). Inorganic P resources were depleted in both years, but inorganic N was exhausted only in 1984. In 1983, Stephanodiscus hantzschii GRUN v. pusillus GRUN. KRIEGER completely dominated the biomass peak. In 1984, Melosira islandica v. helvetica O. MÜLL occurred in great numbers along with S. hantzschii v. pusillus. The growth rate of S. hantzschii v. pusillus, surplus phosphorus dynamics and potential alkaline phosphatase activity were different during the two spring periods. In the experiments, eight alternative nutrient situations were tested during four phases of the natural phytoplankton development. The algae responded to enrichments during the entire phytoplankton bloom in 1983 and 1984. Nutrient interactions were important, especially in 1983, and occurred most frequently during the late exponential phase, biomass maximum and declining phase in both years. Interactions between N and P were most common in 1983, occurring during the late exponential phase and biomass maximum. N and Se interaction occurred occasionally. Interactions between P and Se were more frequent in 1983 than in 1984. When nutrients interacted, the combined effect was generally smaller than the sum of their individual effects. P deficiency indicators and the experiments showed clearly that the bloom of 1983 was P limited. In 1984 no such clear pattern was found.
Effets du retard dans la première alimentation sur le développement de la larve planctotrophe de l'oursin Paracentrotus lividus
Authors: Fenaux Lucienne , de Greef Yves , Cellario Christiane
Published: February 2007

The growth of the skleleton and changes in biochemical constituents (proteins, carbohydrates and lipids) were observed in embryos (days 0 and 1) and larvae (2‐8 days) of the sea urchin Paracentrotus lividus that were starved (C 0) or fed low (1,000 cells of Hymenomonas elongata, C 1) or high (5,000 cells, C 5). Different batches of C 1 and C 5 larvae were fed first the 2nd, 3rd, 4th or 5th day after fertilization. Initiation of feeding 24 h after hatching slowed down the rate of increase in length of the larval appendages. A differential growth of skeletic rods (somatic and postoral rods) and variations in proteins weights shows the existence of a mixotrophic phase between endotrophic and planktotrophic phases. Best development occured in larvae which were first fed at the lower food level 24 h after hatching.

On the 2nd and the 3rd day the somatic/postoral rod ratio is ≥1. This higher ration can be used to estimate the age of natural populations of larvae.
Sedimentary Losses in the Reservoir Saidenbach: Flux and Sinking Velocities of Dominant Phytoplankton Species
Authors: Horn Heidemarie , Horn Wolfgang
Published: February 2007

Sedimentation of phytoplankton was studied in the meso/eutrophic reservoir Saidenbach for two years and measured as biovolume in a sedimentation trap near the bottom. It comes to an annual average of 2.76cm3/m2 × d (0.4… 10.9) and is statistically significant dependent on the free water concentration measured 14 days before. This allows flux to be reliably calculated without any direct measurement. The bottom is reached above all by diatoms which form 90% of the deposited algae. The sinking velocity of the diatoms is mainly determined by their physiological state: During growth phases low sinking velocities (0.1 … 2m/d) were found, while in decline phases they increased considerably (>6m/d). The highest average sinking velocities found among large diatoms were calculated for Fragilaria crotonensis (3…4m/d), the lowest for Melosira italica (1.5…2m/d). The values for Asterionella formosa, Synedra acus and Diatoma elongatum were between them. Turbulence has no influence on sinking velocity (usually, spring full circulation sees the highest sedimentary losses), but plays an essential part in the survival of the population in free water. Permanent redistribution prevents diatoms from sinking out from the euphotic layer, this “inoculation” making further development possible. On an annual average, phytoplankton forms approximately only one quarter of the whole trap sediment (max. 62%). The flux of the dry weight of seston (2.33g/m2 x d on an average) reflects the changes in phytoplankton flux negligibly only and does not reveal any relation to it. so that seston flux is not suitable for determining phytoplankton sedimentation. But it is possible to calculate this at a probability of 65 to 94%, by using the free water concentration measured 14 days before.
Macrozoobenthic Assemblages of the Evros Delta (North Aegean Sea)
Authors: Gouvis N. , Koukouras A.
Published: February 2007

The composition of the macrozoobenthic assemblages of the Evros Delta (North Aegean Sea) has been investigated by means of 4 replicate quantitative samples, collected at 35 sites. The information obtained from the numerical analysis of the faunal samples and the analysis of other data (values of the main physico‐chemical parameters) revealed the presence of a single community. The faunal composition of this community varies locally according mainly to the salinity and secondly to the particle size of the substrate. The community is described on the basis of its biological parameters and compared with corresponding assemblages from other areas.
Influence du Régime Alimentaire sur la Composition Chimique Elémentaire de Nebalia bipes (Crustacea, Leptostraca)
Authors: Kerambrun P. , Guerin J.‐P.
Published: February 2007

Effect of Diet on the Elementary Chemical Composition of Nebalia bipes (Crustacea, Leptostraca)

Changes in carbon, hydrogen and nitrogen contents of Nebalia bipes were studied under different artificial feeding conditions. Using a multifactor ANOVA, highly significant variations were observed according to diet. C:N ratio, which was 4.99 ± 0.31 in control animals, exhibited extreme values of 3.96 ± 0.09 and 5.52 ± 0.49. From a trophic point of view, the results demonstrate the large possibilities of N. bipes to exploit very different resources. The variability of its elementary chemical composition expressed in C:N ratio is compared to other generalist species.
Calcite Precipitation in Hard Water Lakes in Calculation and Experiment
Authors: Proft G. , Stutter E.
Published: February 2007

Calcite precipitation in model solutions and natural waters depends on the magnitude of saturation (saturation index ≫ 1). Continuous lye addition should simulate the CO2 decrease through assimilation by algae and the experiments can be applied to the autochthonic calcite precipitation in lakes. It seems possible to restore lakes with artificial calcite precipitation. Basic data for this experiment are given in this paper.
Sublittoral Protistan Communities of the Shores of the Sea of Cantabria (Bay of Biscay)
Authors: Fernandez‐Leborans Gregorio , Novillo Apolonia
Published: February 2007

The composition of the protist communities of three coastal areas of the Sea of Cantabria were studied, and the seasonal variation of the larger groups of these organisms described, with respect to the productivity. Also, the annual dynamics of consumption and degradation of organic matter achieved by the ciliate species were analyzed.
The Biogeography of Tropical Phytoplankton Species in the Pacific Ocean
Authors: Semina Halina J. , Levashova Sophia S.
Published: February 2007

The ranges of 10 tropical Pacific phytoplankton species are shown in the maps. Five types of these ranges are discussed. Except for broadly tropical species some species with much narrower ranges are characterized. The bases of ranges and the expatriation areas are given. The bases of ranges of all the species studied fall into similar temperature and salinity limits. Most of the species inhabit a wide range of nutrients concentration, but Climacodium frauenfeldianum and Hemiaulus hauckii are only found at low phosphate and silicate concentrations. These peculiarities determine the geography of ranges of these two species. Among the species investigated only Ceratium gravidum belongs to the shade flora.
Distribution and Species Composition of Zooplankton in Himalayan Ecosystems
Authors: Raina H. S. , Vass K. K.
Published: February 2007

The zooplankton communities of lakes, Sars, wetlands and ponds in Jammu‐Kashmir Himalayas were examined. The waters are situated between 600–3800 m a. s. l. and, in the ordinates 30°–36° N. Significant variations in Rotifers and Crustacean distribution patterns were encountered. Some species having wide tolerance limits are more frequent while a few species due to their rigid environmental demands are restricted to few water bodies. Such species serve as good indicators of trophic evolution. The general distribution of these groups and their ecological implication have been discussed in the paper.
Phytoplankton — Community Structure, Succession and Chlorophyll Content in Lake Müggelsee from 1979 to 1990
Authors: Nixdorf Brigitte , Hoeg Sigrid
Published: February 2007

One aspect of the present work on Lake Müggelsee has been a quantitative assessment of phytoplankton changes over the annual cycle and from year to year as a basis for primary production measurements. The investigations of plankton analysis were carried out in Lake Müggelsee (Großer Müggelsee, Berlin), a eutrophic, polymictic shallow lake with an area of 7.2 km2, a mean depth of 4.9 m. The lake was described as a species rich water with partially considerable developments of diatoms and blue‐green algae as was shown by plankton analyses from the beginning of this century. Since the end of the 60s, when macrophytes disappeared, Lake Müggelsee has been recognized as a lake with extensive phytoplankton development characterized by dense and irregular development of blue green algae and diatoms. Especially solitary centric diatoms increased in number and in biovolume from 1979 to 1990 and occurred with greater diameters in spring during the seasonal course.

The specific content of chlorophyll a was estimated according to the algal composition. It is suggested that the observed decrease in Chl a per unit biovolume is associated with species size rather than the time of development depending on the unknown portion of inactive algal cells resuspended from the sediment surface.
Long‐term Annual and Seasonal Changes of Meta‐ and Protozooplankton in Lake Müggelsee (Berlin): Effects of Eutrophication, Grazing Activities, and the Impact of Predation
Authors: Arndt Hartmut , Krocker Maria , Nixdorf Brigitte , Köhler Antje
Published: February 2007

Annual changes of rotifers, copepods, cladocerans, the ciliate Epistylis rotans, and larvae of Dreissena polymorpha were analysed for the period 1908–1990. Though food resources increased 6–10 fold in the course of eutrophication, only rotifers and Epistylis increased accordingly. Probably as a result of increased predation pressure crustaceans increased only twice.

The seasonal pattern of metazoans and protozoans (flagellates, sarcodines, ciliates) were analysed for 12 and 3 years, resp. During winter and spring, large heterotrophic flagellates and ciliates dominated the zooplankton and were responsible for a pronounced ‐ formerly underestimated ‐ grazing pressure on phytoplankton. In early summer, metazoan filter‐feeders were often able to cause a significant reduction of phyto‐ and protozooplankton. However, during some years, phytoplankton declined in the absence of a pronounced grazing pressure. Field data and experiments revealed that predators were able to regulate the density of cladocerans in early summer (mainly cyclopoids) and summer (mainly Leptodora, smelt and fish juveniles).
Seasonal Changes in the Plankton Dynamics of a Eutrophic Lake Including the Microbial Web
Authors: Nixdorf Brigitte , Arndt Hartmut
Published: February 2007

During 1989 and 1990 the carbon dynamics in the shallow eutrophic Lake Müggelsee (Berlin) were investigated by analysing the seasonal succession of phytoplankton, metazooplankton, protozooplankton and bacteria. Size fractionated algal primary production and exudation were measured as well as bacterial production in order to calculate the amount of carbon covering the bacterial carbon demand by primary production. The impact of bacterivorous protozoans and metazoans was estimated by comparison of the calculated feeding rate and the bacterial production. Our results show a shift within the metabolic interactions of the microbial food web from winter/spring to summer, indicating a high significance of the protozooplankton as a regulator on bacteria during the colder season, whereas from early summer the influence of metazooplankton dominated by cladocerans was evident in this eutrophic lake.
Lake Oxygenation: Application of a One‐box Model with Ice Cover
Authors: Livingstone David M.
Published: February 2007

A one‐box exponential model with constant coefficients is capable of giving a good description of the winter oxygen uptake of a lake not subject to freezing over. A simple modification of the model accounts well for the effects of ice cover. The modified model predicts that, all else being equal, the oxygen regimes of eutrophic lakes will tend to be affected more by ice cover than those of oligotrophic lakes; that a short period of ice cover is of no great consequence for the oxygen regime of the lake, whereas a long period of ice cover results in a disproportionately large decrease in the mean lake oxygen concentration; and that the later break‐up occurs, the greater will be the effect of the ice cover on the oxygen regime of the lake.
Changes in the Benthic Macroinvertebrate Community in Two Years of Colonization of New Experimental Ponds
Authors: Christman Van D. , Voshell J. Reese
Published: February 2007

The objective of this study was to determine if the benthic macroinvertebrate community structure in a set of experimental ponds changed significantly during the second year of their existence. This is an important factor in pesticide registration testing using this type of facility. One year has been established as sufficient time to develop a complete community but this has never been tested. Comparison of the community at the end of year 1 to the community at the end of year 2 showed no significant differences for community summary measures (total density, taxa richness, diversity, Bray‐Curtis similarity index); however, some individual taxa densities were significantly lower at the end of year 2. Physicochemical parameters measured indicated that the ponds were oligotrophic. Submerged macrophytes colonized and became established in most of the ponds during year 2. With the exception of a few noninsect taxa, the experimental pond communities appeared similar to mature communities in shallow lentic environments. Additionally, the seasonal changes observed in the pond communities followed expected patterns.
Tube‐dwelling Meiofauna in Marine Sediments
Authors: Nehring Stefan
Published: February 2007

Tube‐dwelling has been recognized previously as a life‐style for several meiobenthic species, but behavioural observation of living specimens has rarely been reported. The extent to which tube‐building and tube‐dwelling occurs within meiofauna, and how they have influenced evolutionary and ecological processes as well as morphology within these organisms, is relatively unknown but potentially of great significance. In addition to direct observation of tube‐building and the occurence of tubes in natural habitats, the internal anatomy associated with tube‐building in two nematode species (Ptycholaimellus jacobi, P. ponticus) and one harpacticoid copepod species (Stenhelia palustris) is the focus of this study. Special attention is given to the secretory products, glands, and their association with secretory pores. Also, the role of meiobenthic tube‐dwelling activities in relationship to their environment is extensive discussed.
Participation of a Specific Substrate Degrading Strain in a Mixed Bacteria Culture as a Result of Ciliate Grazing
Authors: Macek Miroslav , Hartmann Petr , Škopová Ivana
Published: February 2007

Participation of nitrilotriacetic acid degrading bacterial strain NTA‐1 in the continuous‐cultivated mixed culture was studied under different conditions including predation pressure of the ciliate Dexiostoma campyla (STOKES, 1886). From the viewpoint of dispersed/flocculated biomass distribution, significant relationships between NTA‐1 and total bacteria ratio, and dispersed and total biomass ratio were proved in the systems without high concentrations of ciliates. The ciliate concentrations reaching 104 ml−1 stabilized flocculated biomass growth without directly affecting NTA‐1 portion. Using fluorescently labelled NTA‐1 bacteria, filter feeding rates of ciliates were evaluated (maximum individual uptake rate upon NTA‐1 bacteria as a number of bacteria per ciliate per hour being 120 h−1 and 260 h−1 under ciliate division rate of 0.3 day−1 and 1 day−1, respectively). Biomass balance showed that dispersed NTA‐1 bacteria should not serve as the sole feeding source for these free‐swimming ciliates. The role of diversity of mixed bacterial diet in ciliate growth and the role of ciliate predation in stabilizing bacterial assemblage structure was proved.
Studies of Aquatic Fungi. XXVI. Hyphomycetes in the River Supraśi in Various Seasons of the Year with Reference to Environmental Conditions
Authors: Czeczuga Bazyli , Orłowska Mirosława
Published: February 2007

The authors investigated the aquatic mycoflora and the environmental factors at two sites of the River Supraśl on the occurrence of various aquatic Hyphomycetes.

At the stations investigated the presence of 56 aquatic Hyphomycetes species was noted. The foam of both site I and site II contained more species than did the water collected at these sites. Most of the aquatic Hyphomycetes found at the sites studied are common fungi quite frequently found in different kinds of water bodies. On the other hand 17 species have been comparatively seldom encountered up to date.
Limnological Studies in a Tropical Man‐Made Lake (Lagartijo Reservoir) Venezuela
Authors: De Infante Aida Gonzáles , Infante Otto
Published: February 2007

The purpose of this study was to evaluate the present limnological conditions of Lagartijo reservoir (North central Venezuela) and to compare them with conditions reported in early studies. Lagartijo reservoir supplies an important part of the water demand for Caracas city and wide fluctuations on water volume occur annually.

Relevant physical, chemical and biological data were obtained from three sampling stations between July 1990 and April 1992. The reservoir was permanently stratified with a well defined thermocline. The main tributary (Lagartijo river), with a temperature about 6° C colder than the surface temperature of the reservoir, flows through the hypolimnion producing distinct chemical and biological properties. The average of the daily integral phytoplankton photosynthesis was 1550 mg C m−2 d−1. The present annual average of the net photosynthetic activity is about 40% lower than the reported for 1970 and corresponds to an apparent decrease in phytoplankton biomass and to the reduction of the euphotic zone. Photosynthetic activity was higher for the wet season than for the dry season. Actual chlorophyll a concentration in the euphotic zone averages 4.9 μg l−1. Abundance of zooplankton was significantly decreased in comparison to 1976. Mean zooplankton biomass (dry weight) for the upper 10 m layer was 596 μg l−1. Copepods accounted for most of this biomass, followed by cladocerans and rotifers. For the first time, a freshwater medusa (probably Craspedacusta sowerbyi) was collected from Venezuelan waters.
Comparative Limnology of Four Cuban Reservoirs
Authors: Laiz Orlando , Quintana Isabel , Blomqvist Peter , Broberg Anders , Infante Aida
Published: February 2007

Four Cuban reservoirs (Higuanojo, Tuinicu, Lebrije and Zaza) in the Sancti Spiritus province were studied in 1988–1989. The study was based on monthly samples of physical, chemical and biological components of the pelagic ecosystem.

The reservoirs were warm‐monomictic with more or less complete water mixing during the dry season and stable stratification during the wet season when inflow of water was highest. The mixing event was very important in regulating the biology and chemistry of the reservoirs. During the stratified period the water was anoxic below 10 m depth and reduced compounds, especially ammonium, accumulated. In the reservoirs with less stable stratification, ammonium was occasionally oxidized and the nitrogen lost to the atmosphere through denitrification. Phytoplankton biomass varied considerably among reservoirs and was not only correlated to total‐P, but also to light, Zooplankton biomass and composition was related to availability of good quality food and to the intensity of fish predation.
Variability and Representativness of Lake Variables
Authors: Håkanson Lars
Published: February 2007

This paper summarizes results from extensive field work in 95 Swedish lakes. It discusses four years (1986–1989) of monthly data on pH, Secchi depth, temperature, alkalinity, total‐P, conductivity, Fe, Ca, hardness and colour. These variables vary both temporally and areally. The focus here is on such variations and patterns in variations, and how to express lake‐typical values, not for specific sites and sampling occasions, but for entire lakes and longer periods of time (months‐years). This is of importance in monitoring and validating models. A definition of total variability (TV), expressing variability between adjacent months within the year, and between the same month for different years, is presented. Selected results: An important pattern emerges for total‐P with marked increases in TV during the summer and minimum values in winter. The pattern for colour shows lower TV during summer and higher TV during fall. The TV‐values for pH are low and stable thoughout the year and no clear seasonal pattern can be seen. A seasonal pattern exists for conductivity, alkalinity, hardness, and Ca with higher TV during spring. The results concerning the variability within and between lakes show that the greatest differences exist for conductivity and Fe; the smallest (except temperature) for pH and alkalinity.
Characteristics of the Summer Hydrological Regimen and Chlorophyll Distribution in the Volga River Reservoirs
Authors: Litvinov A. S. , Mineeva N. M.
Published: February 2007

Field observations on chlorophyll content and hydrological parameters such as temperature, dissolved oxygen and conductivity profiles, Secchi disk transparency and water color were carried out at 5 reservoirs of the Mid and Lower Volga River during August 1990 and 1991. Principal Component Analysis distinguished four classes from 46 sampling points based on the hydrological regimen and phytoplankton development.
Description of the Immature Stages of Three Nearctic Species of the Genus Berosus Leach (Coleoptera: Hydrophilidae)
Authors: Archangelsky Miguel
Published: February 2007

Egg cases, larvae, and pupae of Berosus corrini Wooldridge 1964, Berosus hoplites Sharp 1887, and Berosus pugnax LeConte 1863, are described and illustrated with line drawings. Bionomic and behavioral observations of larvae and adults are included. Keys to different instars of B. hoplites and B. pugnax larvae are provided.