bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Functional Characteristics of Aquatic Animal Communities
Authors: Alimov A. F. 
Published: February 2007

AbstractStructural and functional characteristics of macrobenthic animal communities have been studied in several rivers and lakes. Shannon diversity index (H) has been used as a measure of animal community structure. Relation of community production (Pb) to metabolic rate of all animals in the community (Rb) was regarded as its functional characteristic. Quantitative relations between structural and functional characteristics of aquatic animal communities have been established. The work deals with steadiness and stability and complexity of aquatic animal communities with regard to their structural and functional characteristics. For a better understanding of possible changes in communities brought about by human impact a notion of community durability is introduced, which means their ability to resist environmental changes maintaining their structure and functions.
Optical Limnology of a Hypertrophic Gravel‐Pit Lake
Authors: Cobelas Miguel Alvarez 
Published: February 2007

AbstractThe underwater light field has been studied in a hypertrophic, gravel‐pit lake close to Madrid (Spain) during a one year cycle. Both the inherent and the apparent properties of the underwater light field have been weekly surveyed. As theoretically expected, there is a link between inherent and apparent properties in this lake. Evidence is given suggesting that a seasonal trend in the underwater light field seems to occur. The main factor attenuating light in the vertical column is phytoplankton chlorophyll “a” but humic substances also appear to play an importtant role in light attenuation.
Phytoplancton du lac Ichkeul (Tunisie): Composition, structure et activité photosynthétique Phytoplankton of Lake Ichkeul (Tunesia): Composition, Structure and Photosynthetic Activity
Authors: Rejeb‐Jenhani Amel Ben , Kartas Fredj , Lemoalle Jacques , Amblard Christian 
Published: February 2007

AbstractPhytoplankton evolution was established during a study carried out on lake Ichkeul (Tunisia) from January 1985 to June 1988. During this period, the flora, composed of 51 species is distributed principally between Diatomophyceae and Chlorophyceae. Succesional changes of phytoplankton were often unpredictable and characterized by populations with monospecific trend. Photosynthetic activity and the parameters Aopt and IK were studied regularly along the year 1985 by oxygen method (GOLTERMANN, 1969). The relations between phytoplankton composition and photosynthetic activity were discussed.
Current Trends in Hydrographic and Chemical Parameters and Eutrophication in the Baltic Sea
Authors: Nehring Dietwart , Matthäus Wolfgang 
Published: February 2007

AbstractAnalysis of phosphate and nitrate data recorded in the winter surface layer of the Baltic Sea from 1958 to 1989 indicate positive overall trends, although the rate of accumulation has decreased since 1978. The long term accumulation of these algal nutrients in the oxic deep water below the halocline has also decreased since 1977. Under anoxic conditions, however, the trend shown by the phosphate concentration is distinctly positive in recent times owing to phosphate remobilization from the sediment.The salinity has decreased in the surface water and even more rapidly below the halocline in the central Baltic basins during the period marked by the absence of major salt water inflows since 1977. The oxygen conditions have also deteriorated in the near‐bottom water layer during this time as shown by the considerable rise in the hydrogen sulphide concentrations. These changes, including the recent phosphate accumulation under anoxic conditions, can thus be considered natural rather than anthropogenic.The impact of long‐term variations in nutrients and hydrographic parameters is discussed with respect to the development of Baltic fish stocks.
The Ecological State of the Waddensea. An Assessment
Authors: Höpner Thomas 
Published: February 2007

AbstractSince the present quality state of the Wadden Sea is judged more discordantly than that of the North Sea, it is examined whether the Wadden Sea is a separate ecosystem. The nutrient load into the Wadden Sea and the trend of the load are assessed. Biological indicators of the ecological state of the Wadden Sea are examined with the result that there are signs of a bad as well as of a good state. This contradiction is assigned to the fact that quality standards are absent. Self‐protection mechanisms of the Wadden Sea are discussed with respect to their responsibility for the relatively good state. A qualitative model is proposed to explain the long‐term behaviour of the ecosystem.
The Microbial Food Web and its Sensitivity to Eutrophication and Contaminant Enrichment: A Cross‐system Overview
Authors: Weisse Thomas 
Published: February 2007

AbstractThe relative contribution to the pelagic carbon flux of bacteria, autotrophic picoplankton (APP), and heterotrophic nano‐ and microplankton is highest in pristine oligotrophic waters. Increased nutrient loading stimulates picoplankton production but reduces the importance of the microbial food web. Not all microorganisms are affected in the same way by eutrophication and contaminant enrichment. In contrast to bacteria and heterotrophic nanoflagellates, the APP was found to be highly sensitive to heavy metal contamination. The changing significance of the microbial loop has far‐reaching consequences for the entire ecosystem including alterations occurring in the benthos. The structure and functioning of the microbial food web is similar in marine, brackish, and freshwater ecosystems.
On the Importance of Planktonic Protozoans in the Eutrophication Process of the Baltic Sea
Authors: Arndt Hartmut 
Published: February 2007

AbstractAnalysing 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractIn 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

AbstractEpifluorescence 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

AbstractThis 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

AbstractA 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

AbstractThe 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

AbstractAn 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

AbstractAn 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

AbstractOver 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

AbstractThe 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

AbstractSecondary 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

AbstractThe 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.