bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lake Number, a Quantitative Indicator of Mixing Used to Estimate Changes in Dissolved Oxygen
Authors: Robertson Dale M. , Imberger Jörg 
Published: February 2007

AbstractLake Number, LN, values are shown to be quantitative indicators of deep mixing in lakes and reservoirs that can be used to estimate changes in deep water dissolved oxygen (DO) concentrations. LN is a dimensionless parameter defined as the ratio of the moments about the center of volume of the water body, of the stabilizing force of gravity associated with density stratification to the destabilizing forces supplied by wind, cooling, inflow, outflow, and other artificial mixing devices. To demonstrate the universality of this parameter, LN values are used to describe the extent of deep mixing and are compared with changes in DO concentrations in three reservoirs in Australia and four lakes in the U.S.A., which vary in productivity and mixing regimes. A simple model is developed which relates changes in LN values, i.e., the extent of mixing, to changes in near bottom DO concentrations. After calibrating the model for a specific system, it is possible to use real‐time LN values, calculated using water temperature profiles and surface wind velocities, to estimate changes in DO concentrations (assuming unchanged trophic conditions).
The Seasonal Occurrence of Glass Eels (Anguilla Anguilla L.) in the Rio Minho between 1991 and 1993 (North of Portugal)
Authors: Antunes Carlos 
Published: February 2007

AbstractGlass eels were sampled monthly at two stations in the Rio Minho. The experimental fishery was carried out in the estuary between November 1991 and July 1992 and at an upstream site between December 1991 and March 1993. The yield differed at each station, especially in summer and between the official seasons of the experimental glass eel fishery. Early pigmentation stages were more frequent in the estuary and the maximum lengths and weights were observed in autumn and winter. The official statistics of the professional glass eel fishery are briefly mentioned.
The Distribution of Hydrobiids and the Effects of Sediment Characteristics on the Population Dynamics of Hydrobia ventrosa in a Coastal Region of the Southern Baltic
Authors: Bick Andreas , Zettler Michael L. 
Published: February 2007

AbstractThe composition of the hydrobiid fauna in a coastal water of the southern Baltic was studied in 1990/91 at three stations with different sediment characteristics (grain size, organic content). Four species were found (Hydrobia ventrosa, H. ulvae, H. neglecta and Potamopyrgus jenkinsi). H. ventrosa was dominant at all stations. The mean hydrobiid abundances were 4,000 (stn. C), 18,000 (stn. B) and 40,000 (stn. A) ind./m2 respectively. Abundance was found to correlate with the organic content of the sediment. The reproduction and growth of H. ventrosa was studied. Two reproduction phases were observed, one in summer and the other in late autumn. The autumn reproduction peaks were staggered owing to the different growth rates at the various stations. Possible correlations between the differences in shell size of H. ventrosa at the various stations and both sediment characteristics and abundance are discussed.
Lebensgemeinschaften koexistierender Arten der Wasserkäfergattung Hydroporus aus zwei norddeutschen Untersuchungsgebieten (Coleoptera; Dytiscidae)
Authors: Behr Hauke 
Published: February 2007

AbstractThe community structure of 15 species of the genus Hydroporus was investigated in various pools with the multivariate software DECORANA, TWINSPAN and CANOCO. Abiotic values measured at 22 bog pools were correlated to DECORANA‐data. Typical communities in the Ohemoor (near Hamburg) are related to the factors shaddow, absorption, calcium, and sodium. Data of coexisting Hydroporus species (including other small Dytiscidae, Haliplidae, Noteridae) from 93 pools (near Seedorf/Schleswig‐Holstein) could be devided into 4 typical communities (bog, wood, sand‐pit, agricultural areas).
Diurnal Variations in Swimming Activity of Rutilus rutilus (Cyprinidae) in a Group under Tank Conditions
Authors: Hammer Cornelius , Temming Axel , Schubert Hans‐Joachim 
Published: February 2007

AbstractMeasurements of the swimming activity of a group of roach (12–19 cm TL, average) in a circular swimming chamber revealed two distinct activity patterns: a diurnal and a nocturnal one. The experiments showed that, having the choice, two factors stimulated the rhythmicity of the swimming behaviour of the fish, i.e. light intensity and the presence of a current field in the proximity of the fish. During daytime (bright light conditions) the fish moved into the current field and swam on average at 0.4 BL/s (resting swimming). The roach remained swimming at this speed even if no current field was established, however, then distributed evenly in the basin. By contrast, during night (dim light conditions) the fish predominantly chose the still water section but swam on average with a cruising speed of 1.6 BL/s (night swimming). Accordingly, they did not seek the still water section for night swimming if the light was kept on. Then again, the fish distributed more or less evenly in the basin. The results support the hypothesis that the fish migrate during night‐time and do this preferably in still water.
The Seasonal Succession of Biotic Communities in Wetlands of the Tropical Wet‐and‐Dry Climatic Zone: I. Physical and Chemical Causes and Biological Effects in the Pantanal of Mato Grosso, Brazil
Authors: Heckman Charles W. 
Published: February 2007

AbstractThe tropical wet‐and‐dry climatic zone is characterized by aquatic environments that cover extensive areas during part of the year and shrink to small standing water bodies or rivers with minimal water levels during the dry seasons. Even in the small permanent water bodies, the conditions fluctuate radically during each annual cycle. While there are often strong currents in the water courses during the high water periods, most aquatic habitats are strictly lentic during the dry seasons. Studies conducted in the Pantanal of Mato Grosso, one of the largest wetlands of the world, revealed major features of changes in physical and chemical parameters during the annual cycle. The general features of the climate include a hot, rainy period usually lasting from late October through late April, a cool, dry period from late April through late August, and a hot, dry period from late August through late October. Considerable year to year variations are encountered in the dates of onset and end of the various seasons, however. Four annual periods are recognized according to the water level in the Pantanal. Generally, the concentrations of dissolved inorganic substances are very low and stable during the high water period and variable and usually high in the remaining standing water bodies when much of the region has dried out. The amount of mineral nutrients increases as the water level rises during the early rainy season but decreases again as the aquatic macrophyte populations develop. Some of the reasons for the many short‐term changes in mineral nutrient concentrations and the roles of the various aquatic communities are discussed. The results presented will serve as a basis for subsequent studies on the seasonal succession of the flora and fauna.
Some Bag Experiments on Tibbs Run Lake, W.V., A Eutrophic Acidified Lake
Authors: Yates Carl , Decosta John 
Published: February 2007

AbstractTibbs Run Lake was sampled from December 1979 to December 1980, monthly during the winter and biweekly during the spring, summer, and autumn. Primary production was measured from March 1980 to February 1981, either monthly or biweekly, as indicated above. The mean annual hydrogen ion concentration was equivalent to pH 4.33. This pH was 46% lower (based on H+ concentrations) than the 1977–1978 mean. The low pH of the lake is due to inputs of acid precipitation and the low buffering capacity of the watershed. Predictions of further reductions in the lake pH, based on mean annual hydrogen ion concentrations and hydrogen ion retention coefficients (RH) from Shellito (1979) and this study, indicate that the lake pH should reach an equilibrium with the precipitation pH between 1982 and 1985, assuming the precipitation pH continues to average 4.10. The stratified period mean chlorophyll a and total phosphorus concentrations were 22.1 mg/m3 and 19.3 μg/1, respectively. Total phosphorus loading to the lake was 0.233 gP/m2/yr.To examine the effects of neutralization and fertilization with phosphorus an in situ bag enclosure experiment, lasting 16 days, was performed during the summer of 1980. In the bags, phosphorus (20 μg/1 on days 0,4,8,12 as KH2PO4) was added alone and in combination with a base addition (IN KOH). The base additions raised the pH to approximately 7.8. Other treatments included base addition alone and a control. The maximum chlorophyll a concentration was found in the phosphorus treatment (∼30 mg/m3) on day 6. The phosphorus plus base treatment exhibited a 10 day lag before reaching a maximum chlorophyll a concentration (∼27 mg/m3) on day 16. The highest production rate was found in the phosphorus plus base treatment on day 12 (∼27 mgC/m3/hr.).A similar bag experiment, lasting 46 days, was performed during the late summer and early autumn of 1980. The treatments were the same as in the first experiment, however, the nitrate‐nitrogen depletion in the lake and treatments necessitated the addition of nitrogen (2 mg/1 as NaNO3) to one of each replicate treatment on day 5. On day 34, the maximum chlorophyll a concentrations were found in the phosphorus plus base nitrogen treatment (∼120 mg/m3) and the phosphorus plus nitrogen treatment (∼38.8 mg/m3). The control plus nitrogen treatment was submerged and possibly contaminated on day 5. All treatments not receiving nitrogen, except for the phosphorus plus base treatment, decreased in the chlorophyll a concentration throughout the experiment. The phosphorus plus base treatment peaked in the chlorophyll a concentration on day 45 (∼28 mg/m3) despite non‐detectable levels of nitrate‐nitrogen. The maximum primary production rate was found in the phosphorus plus base plus nitrogen treatment (∼32 mgC/m3/hr.) on day 11.
Ecology and Gametogenic Biology of the Genus Umbellula (Pennatulacea) in the North Atlantic Ocean
Authors: Tyler P. A. , Bronsdon S. K. , Young C. M. , Rice A. L. 
Published: February 2007

AbstractFour putative species of the seapen genus Umbellula, U. lindahli, U. thomsonii, U. durissima and U. monocephalus, are found at bathyal and abyssal depths in the Porcupine Seabight and Abyssal Plain in the NE Atlantic Ocean and at bathyal depths off the Bahamas. The most common species, U. lindahli, has a cosmopolitan distribution in the world ocean. In situ observations, from bathyal depths in the Bahamas, of the posture of U. lindahli show that the polyps are spread out to maximize particle capture from the water column. In addition, the individuals of U. lindahli from the Bahamas suggest that the tentacles are cropped by a predator, but there is no evidence of predation in the NE Atlantic specimens. Reproduction in U. lindahli is typical of that previously observed in pennatulids. Fecundity is high, although most of the oocytes present are previtellogenic with only a few developing through to maximum size at any one time. Some specimens of U. lindahli appear to be infested with a small flatworm.
Abyssal Megafaunal Necrophages: Latitudinal Differences in the Eastern North Atlantic Ocean
Authors: Thurston Michael H. , Bett Brian J. , Rice Anthony L. 
Published: February 2007

AbstractA pop‐up time‐lapse camera system (BATHYSNACK) was used to study megafaunal organisms attracted to bait at three abyssal localities in the eastern North Atlantic Ocean, a northern site on the Porcupine Abyssal Plain and two sub‐tropical sites on the Madeira Abyssal Plain. Fish and decapod crustaceans appeared on 47% of photographs taken during deployments of up to seven days duration. The fishes Coryphaenoides (Nematonurus) armatus and Pachycara bulbiceps and the decapod Munidopsis spp. dominated appearances at the northern locality whereas over 95% of records at the two subtropical localities were of the decapod Plesiopenaeus armatus.Cyclical variations in necrophage abundance did not correlate with tidal cycles of near‐bottom currents, although high P. armatus numbers were inversely related to current speed. Most of the frequently recorded entities showed contagious intraspecific distributions. In contrast, many of the interspecies relationships were non‐random, with co‐occurrences lower than expected, probably as a result of physical disturbance or potential predation. Population densities based on times of first arrival were calculated.Assemblages dominated by fish at higher latitudes and crustaceans at lower latitudes are discussed in terms of organic carbon supply to the deep sea and pelagic community structures.
On the Vertical Distribution of the Metazoan Meiofauna in Shelf Break and Upper Slope Habitats of the NE Atlantic
Authors: Vanreusel Ann , Vincx Magda , Schram Danielle , van Gansbeke Dirk 
Published: February 2007

AbstractThe metazoan meiofauna of nine stations in shelf break and upper slope areas (70 to 1500 m water depth) of the N.E. Atlantic were investigated in order to assess which environmental factors are important in the control of densities and sediment profiles. Total meiofaunal densities (ranging between 368 and 1523 ind/10 cm2) were correlated with bacterial densities, an important food source for meiofauna. However, considering sediment vertical distribution profiles, the relative importance of both food and oxygen on the meiofauna became obvious. A combination of both bacterial densities and oxygen supply could explain about 95% of the variability in the vertical profiles of the meiofauna densities. Meiofauna numbers increase in proportion to food availability in the surface sediment layers, but this relationship breaks down in deeper sediment layers where the oxygen supply is often limiting, particularly in fine sediments.
Micro‐ and Nanoforaminifera from Abyssal Northeast Atlantic Sediments: A Preliminary Report
Authors: Gooday Andrew J. , Carstens Marina , Thiel Hjalmar 
Published: February 2007

AbstractRose Bengal stained benthic foraminifera which pass through a 63 μm mesh (microforaminifera and nanoforaminifera) have been extracted by handsorting the fine sieve residues (> 45 μm, 31 μm, 28 μm, 20 μm, 15 μm) of abyssal sediment samples. The samples were collected using a multiple corer in four areas of the northeast Atlantic between 31° N and 59° N. The abundance of these minute foraminifera varied from 2 specimens per 1 cm2 (Madeira Abyssal Plain) to > 110 per 1 cm2 (BIOTRANS area). They include a variety of taxa, the most common being certain rotaliid species, hormosinaceans and other multilocular agglutinated forms, the unilocular agglutinated genus Lagenammina, soft‐bodied agglutinated sphaeres and flasks (saccamminids and psammosphaerids) and allogromiids. Some specimens are < 63 μm in maximum dimension but others belonging to elongate taxa are longer.Two samples taken 10 cm apart on the Porcupine Abyssal Plain suggest that minute foraminifera may be patchily distributed on a small scale. One sample, which was overlain by substantial amounts of phytodetritus, contained > 100 stained specimens (> 30 per 1 cm2) while the other, in which much less phytodetritus was present, yielded only 10 specimens (2.9 per 1 cm2). This observation suggests that some micro‐ and nanoforaminifera may flourish in the presence of decaying organic matter, perhaps consuming the associated bacteria. The presence of phytodetritus may also explain why two of our samples from the Madeira Abyssal Plain (MAP) contained an order of magnitude more stained tiny foraminifera than two other MAP samples in which phytodetritus was absent.
The Effect of Reservoirs on Phosphorus Concentration
Authors: Straškraba Milan , Dostálková Iva , Hejzlar Josef , Vyhnálek Vojtêch 
Published: February 2007

AbstractThe annual average degree of phosphorus retention (both TP and OP) in reservoirs was found to depend mainly on the theoretical retention time (RT). The phosphorus retention (RP) is shown for some reservoirs in Czech Republic to be well approximated (standard deviation = 10.9) with RP(TP) = 74.7* (1‐exp(‐0.0255* RT)) (N = 38, 7 ≤ RT ≤ 604 days).The inclusion of 13 additional reservoirs for which data were assembled from literature resulted in an almost identical relationship: RP(TP) = 76.1* (1‐exp(‐0.0282* RT)) (N = 51, range of RT nearly unchanged).The retention of soluble reactive phosphorus RP(OP) studied on data from literature seems to be higher than that of TP.Statistical comparison with data for RP(TP) of lakes has shown a significantly lower retention in lakes than in reservoirs for comparable RP, resulting in RP(TP) = 66.0* (1‐exp(‐0.00419* RT)) (N = 59, 5.8 ≤ RT ≤ 260000 days).The differences between RP(OP) and RP(TP) and differentiation of lakes and reservoirs are discussed and a need for more thorough theoretical analysis stressed. Consequences for watershed management are summarized.
Die Steuerung der externen Belastung der Sächsischen Talsperren als wesentliche Strategie ihrer Wassergütebewirtschaftung The Control of the External Loading of Saxonian Reservoirs — an Important Strategy of the Water Quality Management
Authors: Pütz Klaus 
Published: February 2007

AbstractThe Reservoir‐administration of Saxony continuously investigates the development of water quality in its numerous reservoirs. 25 of these reservoirs are used for drinking water supply. About 40 reservoirs have considerable importance for recreation and fishing.The following priorities of water quality management are based on the results of scientific investigations:

protection against eutrophication
prevention of increase of nitrate concentrations
protection against polutants, especially pesticides, heavy metals, hydrocarbons, mineral oils
acidification of waters
The objectives of the water quality of the Saxonian reservoirs refer to EU‐guidelines, to DVGW‐guidelines, to the drinking water ordinance of FRG, to guidelines of LAWA and to the actual knowledge of limnology.The evaluation of the most important reservoirs in the period from 1991 to 1994 shows the following result:These objects can be achieved by two main strategies:

the reduction of the external loading
the control by means of the internal ecological mechanisms
To investigate the loadings of the reservoirs and the sources of the nutrients mass balances particularly for phosphorus and nitrogen were based on periodic analyses. From these mass balances the strategies of water qualilty management were derived. An important consequence in this conection is the following:“The protection of the water is a basic requirement to the security of water quality”Therefore, the reduction of external loading is the main field of the strategy. In the case of high nutrient loaded reservoirs, par example eutrophic waters, a combination with the strategy of internal control, particularly with the biomanipulation is carried on.
Nutrient Elimination in an Underwater Pre‐Dam
Authors: Paul Lothar 
Published: February 2007

AbstractThe nutrient elimination was investigated in the underwater pre‐dam Haselbach (UWHA) situated in the mouth region of the Saidenbach reservoir (Saxony, Germany). The pronounced thermal stratification with the depth of the thermocline determined by the top height of the underwater dam (4,8 m below surface) resulted in epilimnetic inflow and hydraulic short circuit between inlet and main basin of the reservoir in summer. A simple model was developed for the approximation of nutrient elimination. Epilimnetic nitrate was used as a quasi‐conservative discharge tracer. Compared with a “normal” pre‐dam of the same size, the estimated mean phosphorus elimination of less than about 20% in UWHA was low. However, the UWHA proved to be an efficient settling basin for allochthonous particulate P.
Phenology and Abundance of Ephemeroptera, Plecoptera and Trichoptera Caught by Emergence Traps at the Weidlingbach near Vienna, Austria
Authors: Waringer J. A. 
Published: February 2007

AbstractA total of 1136 Ephemeroptera, Plecoptera and Trichoptera were caught from March 1993 to March 1994 at the Weidlingbach, a first to fourth order forest brook near Vienna. Austria, using pyramid‐type emergence traps at tree sampling stations (390, 360 and 260 m above sea level). Five species comprised 67.1 % of the catch: the ephemeropterans Paraleptophlebia submarginata (Stephens), Habroleptoides confusa Sartori and Jacob and Habrophlebia lauta Eaton, and the plecopterans Nemoura flexuosa Aubert and Leuctra hippopus Kempny. Most taxa emerged from April to August, but the plecopterans Leuctra prima Kempny and Capnia bifrons (Newman) were caught early in the year (January to April), and Leuctra digitata Kempny (Plecoptera), Chaetopteryx fusca Brauer and Chaetopteryx major McLachlan (Trichoptera) emerged in September and October. In Ephemeroptera and Trichoptera, similarities between species groups were highest at the two upstream sampling stations; in Plecoptera and in pooled taxa, however, similarities were highest at the middle and downstream sites. Except in Trichoptera, diversity was highest at the middle station situated at 360 m above sea level.
Changes in the Trophic Structure of Benthic Macroinvertebrate Communities Associated with Food Availability and Stream Flow Variations
Authors: Basaguren A. , Elosegul A. , Pozo J. 
Published: February 2007

AbstractMacroinvertebrate communities were studied in relation to food (particulate organic matter and periphyton) availability and hydrologic regime in two reaches (autotrophic and heterotrophic) of the Agüera stream (Northern Spain). The structure of macroinvertebrate community reflected the trophic characteristics (main food sources) at each site. From a temporal point of view, both food availability and hydrologic regime seem to be the main factors that determine the dynamics and structure of the community. In the autotrophic reach, shredder density showed significant relationship with CPOM, and scrapers with periphyton both in terms of density and biomass.
The Seasonal Succession of Biotic Communities in Wetlands of the Tropical Wet‐and‐Dry Climatic Zone: IV. The Free‐Living Sarcodines and Ciliates of the Pantanal of Mato Grosso, Brazil
Authors: Hardoim Edna Lopes , Heckman Charles W. 
Published: February 2007

AbstractThis fourth paper in a series on the effects of the wet‐and‐dry climate on the northern Pantanal, Mato Grosso, Brazil, provides an outline of the seasonal activity of sarcodine and ciliate species. Both of these groups of protozoans include grazers on bacteria and algae, predators, and omnivores. Apparently because of their more complex trophic relationships and competition from small metazoans, the fauna of these groups in the Pantanal is considerably less rich in species than the alga flora, and the populations of most species remain small throughout the year. The presence of only 97 species was recorded during a period of study lasting about three and a half years. While the number of testacean species encountered is not notably less than expected, the number and diversity of the ciliate fauna are remarkably low compared to those encountered not only in the eutrophic waters of the temperate zones but also in water bodies in the eastern part of Brazil. The species found are almost exclusively cosmopolitan or circumtropical in distribution.