bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lake Guri (Venezuela): Preliminary Limnological Characterization of a Large Tropical Blackwater Reservoir
Authors: Weibezahn Franz H. 
Published: February 2007

AbstractThe Caroni River, a tributary of the Orinoco River, in south‐eastern Venezuela, and originating in the Guayana Shield, has been impounded by the construction of two dams. The largest, Guri, is 90km upriver from the confluence with the Orinoco. The final stage of the dam and hydroelectric power plant of the Guri complex, was completed in 1986. The Guri Reservoir (62° 32′–63° 18′ long. W and 6° 55′–7° 52′ lat. N) is a blackwater lake, due to the high concentration of humic substances in the water. The surface of the reservoir is 4250km2 at normal maximum operating water level of 270 m a.s.l., has a maximum depth of 150 m and a storage capacity of 135.7 km3. The waters of the Caroni, flowing through an old geological basement (Pre‐Cambrian), highly weathered and eroded, are poor in mineral nutrients, making Guri's waters oligotrophic, that is biologically manifested in low organic production (Lewis and Weibezahn, 1976; Gonzalez et al., 1991). Its hydrological regime is closely related to the regional dry‐wet climatic pattern. Chemically, the waters are characterized by low pH and alkalinity, relatively high content of Si, Al und Fe, low anion concentrations with sodium dominating the series, low content of nitrogen, and very low concentrations of phosphorus. Phytoplankton is represented predominantly by Chlorophyta and Chrysophyta, with low biomass and depressed production (Gonzalez et al., 1991). Zooplankton (only Copepoda were studied) is represented by 8 spp. and densities are low (Gonzalez, 1992). Suspended particulates concentrations present descending gradient from the tail of the reservoir towards the dam, but in absolute terms the values are low.
Biology ofClupeichthys aesarnensis(Clupeidae) in Ubolratana Reservoir, Thailand, with Special Reference to Food and Feeding Habits
Authors: Sirimongkonthaworn R. , Fernando C. H. 
Published: February 2007

AbstractThe freshwater sardineClupeichthys aesarnensisis a zooplanktivore like many clupeids. In Ubolratana reservoir, Thailand, it feeds selectively on larger zooplankters, especially Cladocera and to a lesser extent on Copepoda. Other zooplankters are also consumed together with both living and dead insects and occasionally its own young. It feeds during the day. Our results indicate that the slight seasonal differences in food consumed probably reflects differences in availability at different seasons and sites. The fish grows in weight, as expected, at a higher rate than the cube of its length. The condition factor is the same for males and females and shows some seasonal variation. Data on fecundity and gonadosomatic index mark this fish as highly fecund and a year‐round spawner. Its short life span, favourable growth and high fecundity make it a valuable source of cheap protein. In 1990, 17% (about 300 tons) of the fish catch from Ubolratana came from this fish.
Intensification of Reservoir Fisheries in Tropical and Subtropical Countries
Authors: Petr T. 
Published: February 2007

AbstractBy now, most marine and inland fishery resources have been fully exploited or overexploited. To keep up with the growing demand for fish, only a few avenues for increasing fish production remain open. One of these is the intensification of fisheries in inland waters, such as reservoirs, lakes and small water bodies. Fish species transfer and culture‐enhanced fisheries based largely on exotic species, mainly tilapias and cyprinids, is the current common strategy for increasing fishery benefits from tropical and subtropical inland water bodies. The growing human population and rising expectations require a steady growth in the number of reservoirs, both large and small. The development of cage and pen culture, especially in Asia, has substantially increased the reservoir fish production there. In Latin America, tilapias are the mainstay of many reservoir fisheries. By the year 2025, an additional 62 million tonnes of aquatic products will be required to maintain the present consumption of 19.1 kg/person. Much of it will have to come from inland waters, including reservoirs and small water bodies.
Growth Rates of Roach (Rutilus rutilus (L)) in a Cooling Water Reservoir under Different Thermal Conditions
Authors: Balkuvienė G. , Pernaravičiūté B. 
Published: February 2007

AbstractThermal effluent from the nuclear power plant on Lake Drūkšiai in Lituania has had a major impact on fish population and other aquatic biota of this lake. In 1984, Lake Drūkšiai was transformed into a cooling water reservoir of the Ignalina Nuclear Power Plant (INPP). The greatest impact of elevated water temperatures was on the fish species composition. Roach (Rutilus rutilus) adapted itself best to water temperatures averaging in summer month 30°C, and it grew faster, while other species became much less common. The mollusc Dreissena polymorpha Pall, became an important source of food for roach. When the long‐term temperature exceeded 30°C, the rate of growth of roach slowed down.
Life and Times of Five Saskatchewan Saline Meromictic Lakes
Authors: Hammer U. Theodore 
Published: February 2007

AbstractFive closed saline lakes near Humboldt, Saskatchewan, were found to be meromictic. Two of these lakes (Waldsea, Deadmoose) were first discovered to be meromictic in the early 1970s and three (Arthur, Marie, Sayer) in 1985. The origin of their meromixis is ectogenic. One of the lakes, Waldsea, had surface salinities far higher in 1960–1961 than those of 1970 or later and as high as that of the monimolimnion occasionally was from 1970 to the present. During the late 1960s to 1980 the lake level of Waldsea rose four metres as a result of higher than normal snowpacks and subsequent high snowmelt runoff. Endogenic processes of freezing out of salts from the upper metre during ice formation and precipitation of sodium sulphate during autumn cooling also promote meromixis. The lakes which are located in depressions in a relatively flat topography are very exposed to periodic high velocity westerly winds. Although Deadmoose and Waldsea lakes are relatively deep, Arthur, Marie and Sayer lakes have maximum depths of only three to five metres. Meromixis has persisted until the present in three lakes but Marie and Arthur lakes became holomictic during the autumn of 1988, a severe drought year. Bacterial plates were prominent in Waldsea, Deadmoose and Sayer lakes. BChl‐a and BChl‐d were present in 1988 with maxima of 2652 mg · m−3 BChl‐a and 4290 mg · m−3 BChl‐d in Sayer Lake. BChl‐a virtually disappeared in subsequent years.
Influence of an Atypical Summer on the Primary Productivity of Phytoplankton in Two Tropical Ponds
Authors: Kundu G. , Jana B. B. 
Published: February 2007

AbstractPrimary productivity of phytoplankton was measured in two fish ponds at monthly intervals during two annual cycles, of which the second one included an unusual drought. The temporal course of variations in phytoplankton primary productivity was essentially similar in both annual cycles, exhibiting peaks and troughs during summer and winter, respectively. However, monthly mean values of gross and net primary productivity of phytoplankton during the second year were several times higher than during the first. The greatest difference between the two years of investigation was found in the summer peak of primary productivity. It is estimated that an increase of nitrogen or phosphate or the N/P ratio by one unit during the second year caused a 2 to 16‐fold enhancement of the rates of primary productivity. The seasonal changes of photosynthetic efficiency correlated with the concentrations of phosphate.
Phytoplankton Periodicity in a Eutrophic Coastal Water of the Baltic Sea
Authors: Wasmund Norbert 
Published: February 2007

AbstractThe phytoplankton periodicity in the Darss‐Zingst bodden chain, an estuary‐like coastal water of the southern Baltic Sea, was investigated from 1984 to 1990. The following functional groups were established: 1.) nitrogen‐fixing Cyanobacteria plusOscillatoria limnetica, 2.) coccoid Chlorophyceae,Gomphosphaeria pusilla, Lyngbya contortaandStephanodiscus hantzschii, 3.) coccoid Cyanobacteria exceptGomphosphaeria, 4.) diatoms exceptStephanodiscus, 5.) Cryptophyceae and some other flagellates.A general seasonal pattern was observable: in cold winters group 5 dominates; in spring a diatom bloom (= group 4) occurred, which was followed by the development of group 2; steep temperature increases caused a summer bloom of nitrogen‐fixing cyanobacteria (= group 1), which was followed by groups 2 and 3 in autumn; in bland winters group 2 lasts until spring.Grazing was shown to be of minor importance for the phytoplankton periodicity.
Direct Estimation of Food Consumption of Juvenile Fish in a Shallow Inlet of the Southern Baltic
Authors: Mehner Thomas , Heerkloss Reinhard 
Published: February 2007

AbstractThe species composition and feeding behaviour of fish larvae and juveniles was investigated in a shallow inlet of the Southern Baltic. The aim of the study was to examine if there was a predatory impact of young fish on the observed annual collapse of the copepod population. Dominant fish species were herring (Clupea harengus), perch (Perca fluviatilis) and roach (Rutilus rutilus). Roach larvae preferred shallower areas, whereas young herring and perch were found in open water.Highest consumption values were always observed in the evening. By computing complete evacuation of the digestive tract in approximately 3.5 hours, daily consumption in percent of fish fresh weight was 1.3, 4.7 and 5.5% for young herring, roach and perch, respectively. The impact of young fish on the dynamics of the population of the copepod species Eurytemora affinis is negligible.
Growth, Reproduction and Condition of Roach (Rutilus rutilus (L.)), Perch (Perca fluviatilis, L.) and Ruffe (Gymnocephalus cernuus (L.)) in Eutrophic Lake Aydat (France)
Authors: Jamet Jean‐Louis , Desmolles François 
Published: February 2007

AbstractThe growth, reproduction and condition of adults of the three dominant fish species (roach, Rutilus rutilus, (L.); perch, Perca fluviatilis, L. and ruffe, Gymnocephalus cernuus, (L.)) in the eutrophic Lake Aydat were studied over one year cycle. Compared to published data, the growth of R. rutilus and G. cernuus was about average, while that of P. fluviatilis was below average. Comparing to literature, the fecundity of R. rutilus and G. cernuus was low but their oocytes were large. In contrast, P. fluviatilis had a high fecundity but small oocytes. At the end of summer, an abrupt decrease in the condition was recorded only for perch, probably due to stress as a result of environmental conditions. The sex‐ratio was in favour of females for the three studied species but, in contrast to G. cernuus, the sex‐ratio of R. rutilus and P. fluviatilis increased significantly also with age. It is concluded that Lake Aydat is a more favourable environment for R. rutilus and G. cernuus than for P. fluviatilis.
Predatory Filter‐Feeding in Fairy Shrimps: Functional Response of Streptocephalus proboscideus (Crustacea: Anostraca) Fed Anuraeopsis fissa (Rotifera)
Authors: Dumont Henri J. , Ali A. Jawahar , Sarma S. S. S. , Mertens J. 
Published: February 2007

AbstractFour size classes of both sexes of laboratory‐cultured Streptocephalus proboscideus (post‐metanauplii 4.7±0.4; juvenile virgins 8.7±0.7; adults I 13.8±0.9, and adults II 22.07±1.1 mm) were fed five concentrations (20 to 320 ml−1) of Anuraeopsis fissa, or six concentrations (20 to 640 ml−1) in adults I and adults II, for 30 minutes. Post‐metanauplii consumed at maximum 66±9 rotifers ind.−1 min.−1 (mean±S.D.) while the largest adult females maximally ingested 347±37 rotifers min.−1.Regardless of predator size and sex, prey consumption was dependent on prey density. Functional response curves either plateaued or declined at 320 prey ml−1 in post‐metanauplii, juveniles and adults I, and at 640 ml−1 in adults II. Females consumed c. 40% more prey than males. On a daily basis, adult II females consumed up to 1.05 mg rotifer dry weight (10% of their own body weight) while post‐metanauplii consumed up to 0.2 mg DW (100% of their body weight). Intermediate stages had intermediate consumption rates. Filtration rates indicated that a fully grown S. proboscideus may filter as much as 2 1 of water per day, suggesting that fairy shrimps, in their natural environment, may often be food‐limited.
The Seasonal Succession of Biotic Communities in Wetlands of the Tropical Wet‐and‐Dry Climatic Zone: II. The Aquatic Macrophyte Vegetation in the Pantanal of Mato Grosso, Brazil.
Authors: Do Prado Anajde Lemes , Heckman Charles W. , Martins Fernando Roberto 
Published: February 2007

AbstractThe seasonal succession of macrophyte communities on temporarily flooded wetlands in the Pantanal of Poconé was investigated by general surveys of the region and by semi‐quantitative surveys conducted on an area of 2500 m2 with a gradient of water depth steep enough to permit a correlation of the species diversity with the depth and duration of flooding. The tropical wet‐and‐dry climate is the main determinant of the regional ecological conditions, and the seasonal variations of the physical and chemical factors, including the alternation between aquatic and terrestrial conditions over most of the area, produce a pronounced seasonal succession. During all of the seasons, the occurrence and growth of the plant species on the area surveyed was found to be inversely correlated with the water depth, but the statistical significance of the findings varied during the course of the year. The plant species are discussed individually, since little or nothing had previously been reported about the autecology of several of them. In addition, a general survey is made of the common aquatic and wetland plant species encountered in the region. On sites temporarily inundated during the course of the year, there is usually a succession of vegetation involving purely terrestrial and aquatic species as well as short‐lived annuals that appear only during the transition period from wet to dry and perennials with seasonal periods of dormancy during periods of excessive dryness.
The Use of Bacteriological Variables for the Characterization of Different Water Bodies
Authors: Rheinheimer Gerhard , Gocke Klaus 
Published: February 2007

AbstractStudies on the Mediterranean Undercurrent in the Gulf of Cádiz showed that bacterial abundance and biomass as well as heterotrophic activity were higher in the water of Mediterranean origin in 500–800 m depth than in the adjacent Atlantic water. Upwelling processes off Mauretania and Portugal were accompanied by high bacterial numbers (bacterial plate counts) in the mixed surface layer. Changes in the qualitative composition of the bacterial flora in the waters off West Africa and in the Arabian Gulf were explained by the introduction of dust from desert regions into the sea by aeolian transport. In the Western Baltic migration of fish was detected by the presence of special bacteria, which normally live on or in these animals. Regions with complex hydrographic structures such as the Western and Central Baltic Sea revealed interesting relationships between bacteriological abundance and activity on the one hand and characteristic physical and chemical properties, such as origin, salinity and O2/H2S‐content, on the other. The importance of bacteriological variables for the characterization of different water bodies is discussed.
Relationship between Seston Composition and Water Transparency in Spanish Reservoirs
Authors: Riera Joan Lluis , Armengol Joan 
Published: February 2007

AbstractIn the context of an extensive study of 101 Spanish reservoirs, we have explored the relationship between transparency (0.11 ≤ SD ≤ 8.6 m) and a number of general limnological parameters. Principal components analysis has been used as a means to summarize these relationships in two distinct periods, winter and summer, revealing the grouping of variables associated to abioseston or with biomass. Multiple regression analysis has been used to quantify these relationships. Total labile iron, calcium and chlorophyll appeared to be the best regressors of turbidity among our variables. The association between total labile iron and turbidity can be explained by the widespread adsorption of metals onto particles. Total labile manganese and phosphorus showed a similar behaviour, especially in winter. The presence of a relatively large proportion of detrital matter in low‐biomass eutrophic reservoirs in winter has been revealed by the analysis of Chla:C and Chla:N ratios. The fact that low ratios were associated with high iron concentrations gives support to this view. Also the C:P and N:P particulate atomic ratios differed from winter to summer. All these ratios appear to be very sensitive to the presence of a variable detrital component and, therefore, their use as indicators of the physiological state of phytoplanktonic populations is highly discouraged for these reservoirs.
Longitudinal Gradients in the Chemical and Microbial Composition of the Bottom Sediment in a Channel Reservoir (Saidenbach R., Saxony)
Authors: Uhlmann Dietrich , Hupfer Michael , Paul Lothar 
Published: February 2007

AbstractSaidenbach Reservoir is situated in the Erzgebirge Hills, Saxony, in a catchment with agriculture as the principal use and a high sensitivity to soil erosion. The high elimination of total phosphorus (ca. 70%) mainly results from a) the sedimentation flux of planktonic diatoms and b) the adsorption to and sedimentation with mineral particles rich in iron. At stations with a high sulfide concentration in the 0–5 cm sediment layer (about 0.2%), the P content was likewise high (about 0.3%), probably due to the high iron concentration (more than 2.5% of dry weight). A fractionation procedure showed that the major part of the sediment phosphorus was not sensitive to reductants (dithionite) but has been found only in the following extraction step (NaOH extract).
Hydrologic Peculiarities of Valley Reservoirs
Authors: Edelstein Konstantin K. 
Published: February 2007

AbstractThe analysis of data, obtained in more than 400 hydrological surveys of 13 large and small reservoirs during 1960–1993, was made. It was established that the features of bed's form, the irregularity of the water exchange and the horizontal lability of water masses are the causes for the multi‐component hydrological structure of the valley reservoirs. The factors ought to be taken into account in modelling of aquatic ecosystems.
Desmids of the Basrah District, South Iraq
Authors: Al‐Handal Adil Y. 
Published: February 2007

Abstract79 taxa of desmids belongig to 17 genera were observed in 17 samples collected from several parts in Basrah district, South Iraq. 3 genera viz. Actinotaenium, Docidium and Spondylosum, and 41 taxa are new records for Iraqi waters. Distribution of taxa in the area studied as well as in the whole country (when available) are given. Some slight morphological variations in desmids were observed due to the alkaline nature of water.
The Contribution of Gastropod Biomass in Macrobenthic Communities of a Karstic River
Authors: Habdija Ivan , Lajtner Jasna , Belinić Ines 
Published: February 2007

AbstractThis study evaluated the standing crop biomass of freshwater snails and its spatial distribution according to four substrate types (boulders, cobbles, gravel covered with periphyton and gravel covered with macrophytes). The study site, in the Kupa River of the NW Dinarid area of Croatia, is in a karstic region. Depending on habitat, the gastropod wet biomass varied from 6.4% to 43.8% of the total macroinvertebrate biomass per unit area. The gastropods are the dominant component of biomass on boulder substrates in the upper region of the river, and on gravel substrates covered with macrophytes, in the lower course. It was found that gastropods are also the dominant component of the functional group of scrapers. The average annual gastropod biomass constitutes more than 80% of scrapers at sampling sites in the upper and lower regions of the river.
Bosmina (Eubosmina) longicornis longicornis SCHOEDLER, 1866 (Crustacea, Cladocera: Bosminidae) from the Postglacial Sediments of the Neuendorfer See, East‐Germany
Authors: Lieder Ulrich , Günther Jutta 
Published: February 2007

AbstractAnalyses were made of subfossil Eubosmina remains from the Lake Neuendorfer See, a lake in the middle part of the river Spree in the “Urstromtal” of Baruth situated in the eastern part of Germany. In addition to Bosmina (Bosmina) longirostris (O. F. M., 1785) Bosmina (Eub.) longicornis longicornis Schoedler, 1866 occured in the lake from the Boreal (sediment depth 15.85 m) to the recent surface layers of the core. Other eubosminids did not occur during the history of the Lake Neuendorfer See with the exception of few remains of B. (Eub.) longispina, which were detected in the lowermost layers of the core during the late Pleistocene. In the present‐day plankton, Bosmina (Eub.) l. longicornis was the only eubosminid found in the Lake Neuendorfer See. During the long period between colonization during the Boreal to the present, no changes were detected in typical morphological features of B. (Eub.) l. longicornis. All remains of Eubosmina in the layers above 15.85 m belong undoubtedly to the same taxon. No signs of any morphological instability (other then ontogenetic and cyclomorphic formchanges) or “morphological transition” (Hofmann, 1977) to other taxa could be found. By using paleolimnological analyses, the named taxon has proven to be a “good” entity within the group of long‐spined taxa of the subgenus Eubosmina.
Deep‐Sea Macrobenthic Communities at Contrasting Sites off Portugal, Preliminary Results: I Introduction and Diversity Comparisons
Authors: Gage John D. , Lamont Peter A. , Tyler Paul A. 
Published: February 2007

AbstractSpecies diversity, faunal composition and abundance in the deep‐sea macrobenthos are investigated at two, adjoining deep‐sea areas off Portugal experiencing contrasting hydrodynamic conditions in order to test for the importance of disturbance in structuring the community. The first was located at 5,035 m depth on a presumably low current‐energy site on the Tagus Abyssal Plain (TAP) and the second was centered in the lower end of the Setubal Canyon (SC) at 3,400 m depth where high levels of hydrodynamic activity are inferred from ripple bedforms visible in sea bed photographs. Closely grouped, transponder‐mapped, “vegematic” box core samples were taken at each site. Agglutinated foraminifers numerically dominate the macrofauna (retained by 300 μm sieve) at both sites. Seagrass content in the SC cores indicates downslope detrital input from shallow water which is absent in the TAP samples. This must contribute, possibly with high levels of resuspended particles in near‐bed flow, to the almost tenfold difference in abundance of metazoan macrofauna at the two sites. Expected species diversity measured from rarefaction is highest at TAP, both for pooled data and when foraminifers. tanaids and bivalve are considered separately. Evenness (equitability) in species' abundances is also higher at TAP than at SC. These differences are compared with benthic community data from the hydrodynamically disturbed High Energy Benthic Boundary Layer (HEBBLE) site on the Nova Scotia continental rise, and from the Rockall Trough (N.E. Atlantic). In common with these sites, strong bed flow at SC is thought to result in relatively high abundances, lower species richness and greater unevenness by acting to periodically disturb and reduce populations. Differences in the degree to which different faunal groups seem to be affected might be related to differences in lifestyle, particularly burrowing depth.