bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mediterranean Fine‐sand Polychaete Community and the Effect of the Tube‐dwelling Owenia fusiformis DELLE CHIAJE on Community Structure
Authors: Somaschini Alessandra
Published: February 2007

Samples were taken in fine‐sand community of the North Latium coast in February and September for two years.

Eigthy‐eight species of Polychaetes were identified. The most abundant was Owenia fusiformis which was highly correlated to the clay fraction in the sediments. Species richness and abundance of other polychaete species were related to the abundance of this tubicolous species which provides a spatial refuge from predators and implements sediment stability. There was a persistency in the community structure in spite of seasonal fluctuations in the abundance of dominant species.
A Comparison of Phytoplankton and Algae Growing on Plexiglas Slides in an Oligotrophic Lake
Authors: Rodriguez Marco A.
Published: February 2007

This study compares the composition and dynamics of phytoplankton communities and of periphyton communities growing on Plexiglas slides in a temperate oligotrophic lake. Ordination methods were used in the comparisons, which covered a three‐month period during the summer. Plankton and periphyton communities differed considerably, and shared only six common taxa. An ephemeral Dinobryon pulse occurred simultaneously in both communities, and represented the largest source of variability in community composition. Recovery from the pulse was faster in the phytoplankton than in the periphyton. Attachment to substrata, through its effect on cell turnover times and nutrient cycling, is hypothesized to provide a temporal refuge for plankton species during periods of unfavorable environmental conditions.
Dynamics of Phototrophic Microbial Populations in the Chemocline of a Meromictic Basin of Lake Banyoles
Authors: Garcia‐Gil L. J. , Borrego C. M. , Bañeras L. , Abella C. A.
Published: February 2007

The ecological succession of two microbial planktonic populations in the chemocline of C‐IV, a meromictic basin of Lake Banyoles has been studied during the stratification period of 1989 (June to October). A dense population of deep‐living algae Cryptomonas phaseolus was found growing between 13 and 14 meters depth, forming peaks of 10 to 20 μg.l−1 of chlorophyll a. The physical and chemical properties of the water were continually changing during the studied period and were strongly related to the biological processes developed at the monimolimnion of C‐IV. Although the monimolimnion of the basin was initially anoxic (Eh values were around +300 mV and sulphide was not present at detectable levels) soluble iron and sulphide appeared sequentially, displacing the deep‐living algae population and setting the conditions for the development of a population of brown Chlorobiaceae, Chlorobium phaeobacteroides. Although Cryptomonas population abandons the chemocline (13.75 m.) and decreases its biomass, it does not disappear at all, but moves upwards (8–11 m.) leaving the zone to sulphur phototrophic bacteria which find optimal conditions to grow. The sulphide diffusion coming from sediment and the nutrient limitation were the main responsible factors accounting for the upwards migration and the decrease of growth rate of the algal population respectively.
Biology of Multi Cell Ponds Treating Municipal Wastes
Authors: Patil H. S. , Meti G. M. , Hosetti B. B.
Published: February 2007

Observations were made over a period of one year on the performance of multi stage stabilization ponds treating domestic waste waters. The unit is composed of Primary anaerobic (P1) and two consecutive Secondary (P2) and Tertiary (P3) facultative ponds. The overall reduction in BOD, bacteria, PO4, SO4, NH3N, Cl− and total solids were 89.4, 99.8, 76.2, 47.7, 79.7, 18.6 and 74.0 percent, respectively. Elimination of H2S was 84.8% in the final effluents. Chlorella vulgaris was found to be the dominant alga followed by Euglena, Ankistrodesmus, Phacus and Synedra as subdominant forms. 9 species of protozoa have been recorded in the first pond and their number declined in the successive ponds.
Lake Müggelsee and its Environment — Natural Conditions and Anthropogenic Impacts
Authors: Driescher Eva , Behrendt Horst , Schellenberger Günter , Stellmacher Rita
Published: February 2007

Lake Müggelsee, a polymictic eutrophic lake at the eastern border of the city of Berlin (area: 7.3 km2, mean depth: 4.9m) is mainly influenced by the River Spree (flowing through the lake) and subject to various usages, especially to municipal water supply and recreation. Geomorphologic development, morphometric features, climatic conditions, hydrological regime, and position in the hydrographic net are described. Short information is given on fauna and flora of the lake, and on characteristics of the catchment area. Water quality parameters are summarized as 12 year average (1979–1990) and the eutrophic state is compared to other lakes. Finally, a short report on scientific research activities is given.
Lake Müggelsee and the Inflowing River Spree; Comparison of Phytoplankton Communities 1980–1990
Authors: Köhler Jan , Nixdorf Brigitte , Hoeg Sigrid
Published: February 2007

Biomass and community structure of phytoplankton have been analysed in the eutrophic, shallow, polymictic Müggelsee and in the inflowing Spree since 1980. In both lake and river, mean biomass and vitality of phytoplankton were similar. A regular annual succession of planktonic algae was found in both the river and the lake. The same species were found to be dominant, although the actual biomass of single phytoplankton populations differed normally from inflow to lake. Lake phytoplankton was characterized by higher proportions of Cyanobacteria (45.9 ± 11.3% resp. 34.5 ± 8.2%) and lower proportions of centric diatoms (35.1 ± 9.5% resp. 41.9 ± 10.3%, average April‐October, 1980–90). The less abundant Pennales, Chlorophytes, and unidentified planktonic algae < 10 μm had attained a relatively higher importance in the river than in the lake. In the last decade, a pronounced shift from Cyanobacteria to diatoms (mainly Centrales) has been observed in the river.
Phenomenological Description of Polymixis and Influence on Oxygen Budget and Phosphorus Release in Lake Müggelsee
Authors: Behrendt Horst , Nixdorf Brigitte , Pagenkopf Wolf‐Gunter
Published: February 2007

The polymictic properties of a shallow eutrophic lake (Lake Müggelsee, Berlin) are described by the water column stability (N2) and vertical differences in oxygen saturation at the deepest site (7 m) of the lake from 1979 to 1990. Mixing and stratification changed irregularly up to seven times from April to October. Thermally stable conditions generally lasted 1–2 weeks. A maximum of 5 weeks stratification was observed in 1982. Although the oxygen content above the sediment depleted during stratification periods the lake is well supplied with oxygen in general. As a consequence of oxygen depletion, considerable amounts of phosphate can be released from the sediment leading to differences in the concentration of phosphate between the deepest point and subsurface of more than 1000 μg 1−1. The release of dissolved reactive phosphate from the sediment is mainly controlled by the rate of change of oxygen in the deepest layers of the lake.
The Carbon Balance of Phytoplankton Production and Loss Processes Based on in situ Measurements in a Shallow Lake
Authors: Behrendt Horst , Nixdorf Brigitte
Published: February 2007

The balance of phytoplankton biomass was studied during spring and early summer 1986 and 1987 in Lake Müggelsee, a eutrophic polymictic lake. It is assessed as the result of biomass changes, gross primary production (14C‐method) and physiological or internal and ecological or external losses. Biomass changes, primary production, grazing, dark carbon losses and exudation were estimated from in situ measurements. The remaining light carbon losses and net sedimentation were calculated from the phytoplankton balance of the lake. On average the physiological losses of algae ranged between 80.5 of primary production in 1986 and 72% in 1987. Dark carbon losses by respiration ranged between 15 and 20%, and grazing losses between 24.5 and 21.9% of gross primary production in 1986 and 1987, respectively. The remaining 16.6 and 23.6% of primary production which were lost in 1986 and 1987, respectively, are mainly attributed to sedimentation.
The Cost of Reproduction in the Rotifer Brachionus calyciflorus Pallas
Authors: Guisande C. , Galindo M. D. , Galan F. M. , Oliveros F.
Published: February 2007

A study of lifespan, fecundity, and reproductive schedules was carried out with the rotifer Brachionus calyciflorus under different food concentrations.

At high food densities (6.1 to 12.4 μg · ml−1, dry mass) there was an increase in offspring number but the reproductive investment remained constantly. This was possible because Brachionus calyciflorus invested a smaller amount of energy one egg volume being able to increase offspring number. Although egg volume was reduced, this was compensated by the greater amount of energy available to the neonates. The length of the prereproductive period remained constant throughout this range of food concentrations. Within this range a reduction in lifespan was observed. This, however, was not due to a total higher reproductive investment, but to an increased offspring rate production resulting in a shortening of the reproductive period. The length of the post‐reproductive period was not different at all food concentrations.
Free Fatty Acids of Surface Film of Water in the Sydinsky Bay of the Krasnoyarsk Reservoir
Authors: Gladyshev Michail I. , Kalachova Galina S. , Sushchik Nadezhda N.
Published: February 2007

During the summer of 1990 composition and concentrations of free fatty acids (FFA) in the surface film of water were investigated. 23 FFA species were identified. Using cluster analysis in conjunction with ANOVAR correspondence of FFA contents in the surface film with seasonal patterns of pelagic plankton was proved. Three different groups of FFA were revealed, acids of every group had similar seasonal dynamics and presumably were of similar origination. Data obtained gave a chance to suppose that main part of FFA were originated by exudation of living cells of phytoplankton as well as postmortal exudation of bacterioplankton. On the basis of FFA contents in a single sample from the surface film identification of sign of derivatives of phytoplankton biomass was suggested. This express‐assay may be useful for monitoring.
Redescription of Mesocyclops leuckarti (Copepoda, Cyclopoida), Including a Study of its Naupliar Development
Authors: Dahms H.‐U. , Fernando C. H.
Published: February 2007

The female and male of Mesocyclops leuckarti (CLAUS, 1857) from a European population are redescribed in detail. New diagnostic characters are described which have passed unnoticed so far. All six naupliar stages of this species are studied as well. Characters of the adult and naupliar external morphology are discussed with respect to previous studies.
Inorganic Turbidity and the Failure of Fishery Models
Authors: Lind O. T. , Dávalos‐Lind L. O. , Chrzanowski T. H. , Limón J. G.
Published: February 2007

Models for the prediction of fishery production and/or harvest based on primary production, algal biomass, or nutrients and morphometry have been effective in many lakes and reservoirs. Lake Chapala, México's largest, is located on the Río Lerma, one of México's principal rivers. It was made a reservoir in 1903 by the construction of a hydroelectric dam on the out‐flowing Rio Santiago. For the first half of this century Lake Chapala was famous for its native white‐fish (Chirostoma lucius) fishery. This fishery has collapsed. The present fishery consists of small Chirostoma species and the introduced Oreochromis. During the past 17 years the water level has fallen by over 3 meters. Now very shallow, clay resuspension creates low visibility (Secchi < 1 m). Nutrients are abundant with total phosphorus exceeding 1 mg 1−1 and inorganic nitrogen exceeding 0.5 mg 1−1. Photosynthesis is limited by light and especially the unfavorable mixing depth to photic depth ratio. Models based on phytoplankton production or biomass underestimate the fishery by about one order of magnitude while a morphoedaphic model overestimates the fishery to the same extent. We sought to explain alternate pathways to support the realized fishery. Experiments suggest that bacterial prodution, with a bypass of the microbial loop, may offer a partial explanation. Management practices to increase the fishery based on an increased autotrophic base to food chain would fail without consideration of bacterial processes in this highly turbid ecosystem.
Lake Guri (Venezuela): Preliminary Limnological Characterization of a Large Tropical Blackwater Reservoir
Authors: Weibezahn Franz H.
Published: February 2007

The 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

The 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

By 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

Thermal 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

Five 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

Primary 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

The 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

The 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

The 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

Four 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

The 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

Studies 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

In 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

Saidenbach 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

The 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

79 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

This 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

Analyses 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

Species 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.
The Role of a Green Alga in the Precipitation of Calcite and the Coprecipitation of Phosphate in Freshwater
Authors: Hartley A. M. , House W. A. , Callow M. E. , Leadbeater B. S. C.
Published: February 2007

The precipitation of calcite from a calcium bicarbonate solution, similar in ionic strength to natural hardwaters, was observed in a series of experiments utilizing an automated culture apparatus. Seeded growth experiments, using calcite seed crystals, were performed at a range of phosphate concentrations to observe inhibitory effects. These experiments demonstrated a linear relationship of increasing inhibition with increasing initial phosphate concentration. A further series of experiments was performed in which an actively photosynthesizing culture of a unicellular green alga (Chlorococcum sp.) was added to the culture vessel in order to initiate precipitation. Experiments to observe spontaneous precipitation, occurring in the absence of both seed and alga additions, were carried out to compare with precipitation rates in the algal experiments. A control experiment was also performed to investigate whether precipitation occurrred in algal cultures maintained in darkness. The carbonate site mechanistic model, developed for calcite precipitation in abiotic conditions, was used to analyse the results of the algal experiments and found to be applicable.
Die Entwicklung des Makrozoobenthon der Oberen Elbe in den Jahren 1988 bis 1994
Authors: Mädler Konrad
Published: February 2007

After a remarkable reduction of the waste load of the upper part of the River Elbe, a significant restoration of the macrobenthic communities appeared in the last years. The number of found macro‐benthic taxa raised up from 30 to 55 with an increasing proportion of sensitive species. The biological water qulity assessment shows a decrease in the saprobic index from 2.96 in 1988/89 to 2.18 in 1994.
The Adhesive Organ of Larval Pike Esox Lucius L., (Pisces)
Authors: Braum E. , Peters N. , Stolz M.
Published: February 2007

Newly hatched pike laryae swim by lateral movements of the trunk. The swimming path is directed upwards. They do not avoid obstacles but interrupt any movements immediately when colliding a substrate. Paired cement glands in rostro‐nasal position excrete an elastic connection between larva and the touched substrate. Larvae spend yolk sac stage in a motionless position.

The glands were studied by scanning electron microscope, by lightmicroscope and transmission electron microscope. The organs consist of two rostro‐lateral areas which have a striking sculptured surface.

The glandular cells are of the high prismatic type with basic nuclei and granulae in the apical parts. The granulae are already reduced in size and number after hatching against the prehatching stage. This indicates an early secretory activity before an attachement occured.

There are grounds to consider mainly two ecological aspects in favour of pike larvae attached to substrates. One is the distance from the bottom water layers which are often characterized by oxygen deficiency and low water currents. Because pike larvae develop their gills later the gas exchange occurs with the body surface. Favourable water circulation normally exists in some distance from sediment and improves the respiration.

The second aspect is governed by immobility and pigmentation which camouflage larvae against predators.
Autecology of Monhystera paludicola De Man, 1880 – Seasonal, Bathymetric and Vertical Distribution of a Free‐living Nematode in an Oligotrophic Lake
Authors: Traunspurger Walter
Published: February 2007

The autecology of Monhystera paludicola (n = 3766 individuals), a dominant nematode of Lake Königssee, was studied throughout the year 1986. The species comprised 2341% of all nematodes in the littoriprofundal and profundal. Mean yearly biomass was highest at 10 m depth (149 pg/lOO cm2, fresh weight). Abundance peaked twice a year in the littoral (winter and summer) and once in deeper regions (winter). The main reproductive period is the winter. Morphometric data (n = 658) revealed sexual dimorphism in size, body shape and weight. There was considerable water depth and time dependent variation in sex ratios. The proportion of individuals in the top sediment layer increased with water depth. Juveniles and adults were partially segregated in the sediment column. M. paludicola appears to undergo vertical migrations.
The Role of Small Wetlands in Catchment Management: Their Effect on Diffuse Agricultural Pollutants
Authors: Raisin Gregory Wallace
Published: February 2007

Despite extensive interest in natural wetlands and their use in waste‐water technology, little is known about how effective they are for the control of diffuse agricultural pollution. The impact of a small upland wetland located along a drainage line on different storm generated discharge events and resultant downstream nutrient loads over a two year period was assessed. Results for individual events indicated that the relationship between this wetland and its catchment was variable. An annual nutrient budget was determined for this wetland for the period March 1994 to February 1995. The wetland retained 9.7 kg yr−1 (20.5 kg yr−1) of nitrogen and 1.5 kg yrl (±0.1 kg yr−1) of phosphorus which represented 23% of the nitrogen and 38% of the phosphorus that flowed from this catchment. It is concluded that this form of wetland has a role in strategic catchment management for the interception of nutrients flowing from diffuse agricultural sources.
Response of Photosynthesis Models to Light Limitation
Authors: Wallace Brett B. , Hamilton David P. , Patterson John C.
Published: February 2007

An investigation into the effect of time step on a common photosynthesis algorithm reveals that the predicted phytoplankton production and biomass depend strongly on the length of the time step. This time step dependence is due to the assumption that a light limitation factor derived from integrating the irradiance over the time step is equivalent to the integrated light limitation factor over the time step. This subtle inaccuracy in defining the factor for light limited phytoplankton production produces a substantial difference in the biomass estimates derived from the two models. To illustrate the difference, the light limitation factor integrated over the time step is implemented in the one dimensional water quality model DYRESM‐WQ. The new version of DYRESM‐WQ is used to simulate chlorophyll N concentrations in Prospect Reservoir, New South Wales. These results are compared to concentrations predicted using the original algorithm. The comparison shows that the new algorithm for phytoplankton production is relatively insensitive to time step, which decreases the difficulty of calibrating the model for chlorophyll a.
On Soil Rotatoria from a Lithotelma near Halali Lodge in Etosha National Park in N‐Namibia, South Africa
Authors: Koste Walter
Published: February 2007

A soil sample out of a dried rockpool (lithotelma) on a dolomit hill in the Etosha National Park, Namibia, was investigated for possible occurence of rotifers. Besides a numerous and rich microfaunae, e.g. Zooflagellata, Rhizopoda. Acari, Nematoda, Tardigrada and Copepoda, 24 rotifers were found. Until today, four so far unknown Bdelloidea could be described: Dissotrocha decembullata n. sp., Dissotrocha hertzogi aculeata n. ssp., Otostephanos jersabeki n. sp. and Philodina foissneri n. sp.
Seasonal and Interannual changes of chemical characteristics and phytoplankton in a mountain lake of the Eastern Italian Alps (Lake Calaita, Trentino)
Authors: Salmaso Nico , Decet Fabio
Published: February 2007

Measurements at Lake, Calaita, a small mountain lake located at 1605 m. a.s .l. in a metamorphic catchment area in the south of the Trentino Region (Northern Italy), have revealed great seasonal variations in the chemical characteristics and phytoplankton community during the ice free period in 1992 and 1993. The acidity present in wet precipitations (H+, NH4+) was neutralised within the drainage basin by mineral dissolution which led to an increase of basic cations and alkalinity in the runoff. The dilution during periods of higher discharge, e.g. in spring and autumn, resulted in low values of alkalinity (up to 60 μeq 1−1), pH (mostly <6.7) and conductivity (<8 μS cm−1, 20°C). In summer, the decrease in runoff caused higher alkalinity (>10 μeq 1−1), pH (6.9–7.4) and conductivity values (up to 30 μS cm−1). The phytoplankton showed a major development in summer (with biovolume values of up to 7000 mm3 m−3), two different taxa being dominant in 1992 (Oocystis cf. lacustris) and 1993 (Synedra sp.). Unpredictable climatic conditions have a strong influence on the physical stability of the lake, which makes it more difficult to explain the evolution of the phytoplankton community as opposed to deeper lakes.
Temporal changes of a macrobenthic assemblage in Evros Delta (North Aegean Sea)
Authors: Gouvis N. , Kevrekidis T. , Koukouras A.
Published: February 2007

Monthly samples of the macrobenthic fauna were collected during February 1983‐February 1984, in a coastal lagoon of Evros Delta (North Aegean Sea), characterized by a very strong monthly fluctuation of temperature and salinity. 3 groups of samples were distinguished, the first including those taken during the spring months, the second, those taken during summer and autumn, and the third, the samples of winter months. All the above samples were homogeneous concerning number of species, species richness (Margálef index) and evenness, but not as far as species diversity (Shannon‐Wiener index) is concerned. The monthly variation of the total number of individuals and total biomass was significant, with highest values in spring, beginning of summer and autumn. Most months, polychaetes dominating, having the highest relative abundance and wet biomass. The 8 dominating species, which had a cumulative dominance of about 93%, showed strong monthly variation of abundance and biomass.
The functional response of copepodid stages to adult of Parabroteas sarsi (copepoda, calanoida)
Authors: Vega Marina Patricia A.
Published: February 2007

P. sarsi is a carnivorous calanoid commonly found in South Andes lakes. Feeding experiments were carried out in order to analyze the functional response of P. sarsi (copepodid IV to adult) on different cladoceran prey. Predation rates increased with increasing prey density up to maximum (type II) in almost cases. The highest attack coefficients were obtained when P. sarsi adults were fed with the smaller prey (C. dubia juvenile and B. longirostris). The ingestion rates of copepodid IV and CV were smaller than for the adults. The ingested biomass as a proportion of predator biomass (Be/Bp) showed an inversal relationship with the predator length. The maximum Be/Bp ratio, in both sex of P. sarsi, was achieved with C. dubia adult, the intermediate‐sized prey.