bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population dynamics of autotrophic picoplankton in a southeastern U.S. Reservoir
Authors: Ochs Clifford A. , Rhew Kyeongsik 
Published: February 2007

AbstractReservoirs typically exhibit a gradient along their longitudinal axis in turbidity, nutrient flux, and algal biomass. We utilized these characteristics to examine factors influencing temporal and spatial patterns in abundance, biomass, composition, and production of epilimnetic autotrophic picoplankton (APP) in Sardis Reservoir, Mississippi, USA. Over a 18‐month period, APP abundance varied between about 15,000 and 700,000 cells ml−1. Both APP abundance and APP biomass were closely linked to APP production and temperature. On an annual basis, the contribution of APP to total algal biomass and light‐standardized production ranged between 15–47%, and 5–40%, respectively. Prokaryotes comprised more than 95% of all APP in summer, but eukaryotes dominated the APP community in winter. During the nutrient‐depleted summer period, APP decreased in number but tended to increase in the percentage of total algal biomass and production, from the uplake riverine zone to the downlake lacustrine zone. Only in the second year of the study, when reservoir water residence time was more than four times greater than in the first year, were there significant differences in biomass and productivity of APP between the uplake and downlake regions. We suggest that, particularly in years or at times of the year when water‐flow through the reservoir is slow, the importance of APP in Sardis Reservoir reflects a spatial and temporal gradient in nutrient availability.
Gradients of nutrients, dissolved oxygen and sulfide in wave‐protected and unsheltered stands of Phragmites australis
Authors: Rolletschek Hardy 
Published: February 2007

AbstractThe horizontal and vertical distribution of TN, TP, TC, and TIC in littoral sediments and O2 and total soluble sulfide (∑S2‐) in the overlying water was determined to assess characteristic patterns and the extent of littoral accumulation in Lake Müggelsee. Wave extinction by helophytes allows the formation of deposition zones at the land/water‐interface and inside the reed bed. Organogenic sediments (LOI >60% dm, TP >1.2 mg P/g dm, TN >2% dm) declined non‐linear towards open water. Additionally, irregular periods of anaerobiosis and increased ∑S2‐ concentrations (1.316 μg S2‐/1) were measured. Wave breakers, which were built in front of mechanically damaged reed significantly promote littoral accumulation and protect deposition zones from erosion. However, embankment with fagots produces a fine‐grained organogenic mud towards open water. These sediments revealed significantly increased O2 consumption rates (610 mg O2/m2 · d) and steeper gradients of NO3−, SO42‐ and CH4 indicating intensified anaerobic reduction processes when compared with unsheltered sites. The nutrient gradients differed from those of ‘natural’ accumulation zones and caused diminished O2 saturation (by 30%) specially in summer months. ∑S2‐ concentration was positively correlated to TC content of sediments and temperature and negatively to distance from shore. The annual mean concentration ranged among 10 and 51 μg S2‐/1 and was not affected by wave breakers.
Oxygen consumption of a Chaoborus species from a neotropical reservoir (socuy reservoir, Venezuela)
Authors: Corona Alnair , López Carlos 
Published: February 2007

AbstractOxygen consumption of all four larval instars of a Chaoborus species from Socuy Reservoir in western Venezuela was studied under laboratory conditions at 25°C. On a logarithmic basis, oxygen consumption per organism increased as a smooth, linear function of body weight (0.49 power of body weight). Observed rates were lower than other Chaoborus species with comparable body weight at the same temperature. Oxygen consumption per unit weight decreased from smaller to large instar larvae. With the exception of instar I, values of oxygen consumption per unit weight were lower than values reported for other Chaoborus species. The results suggest that our species have low energy demands for maintenance, and are consistent with suggestions about high efficiency in use of energy in genus Chaoborus.
Patterns of benthic fauna and benthic respiration on the celtic continental margin in relation to the distribution of phytodetritus
Authors: Duineveld G. C. A. , Lavaleye M. S. S. , Berghuis E. M. , de Wilde P. A. W. J. , van der Weele J. , Kok A. , Batten S. D. , de Leeuw J. W. 
Published: February 2007

AbstractIn‐situ and shipboard measurements of sediment community oxygen consumption (SCOC), in conjunction with a study of the distributions of macro and megafauna and phytopigments, were used to determine and, where possible, explain the distribution of labile particulate organic matter (POM) on the NE Atlantic continental slope (Goban Spur, SW Ireland). A specific issue concerned the existence of depocentres of labile POM on the slope caused by lateral transport, a phenomenon that has been found previously in the NW Atlantic. The SCOC data from October 1993 and May 1994 showed a steady decrease with increasing water depth. SCOC values ranged from 5.4 mmol m−2 d−1 at the shelfbreak to 0.3 mmol m−2 d−1 at 4,500 m depth. No evidence was found for seasonal variation in SCOC. A clear seasonal signal was observed with regard to sediment phytopigments and phytopigment fluxes into sediment traps attached to the benthic lander. The upper‐ and mid‐slope values of both parameters were much higher in May 1994 than in October 1993 and August 1995. This is consistent with the normal spring bloom pattern; but because of the degraded state of the May phytodetritus in the near‐bottom water, reflected in the lack of a response in SCOC and the low chlorophyll‐a concentrations, it was concluded that the material was not derived from the overlying photic zone, but instead transported from elsewhere in the benthic nepheloid layer (BNL). In August 1995, the lower slope (>3,000 m) had received a strong and fresh phytodetritus pulse (3 g C m−2) forming a mucous layer on top of the sediment. Using phytopigments and sterols as molecular markers, it was shown that the pulse was derived from an offshore bloom with an important contribution by dinoflagellates. By contrast, no mucous layer was found on the upper slope stations in August 1995. Macrofauna biomass showed a distinct decline from the upper slope down to the lower slope conforming to the diminishing supply of labile POM. The total wet biomass of megafauna reached relatively high values at the lower slope (>3,500 m) owing to large motile sea cucumbers. The presence of these “vacuum‐cleaner” sea cucumbers is considered indicative of the occurrence of phytodetritus pulses. In spite of their assumed adaptation to periodic pulses, the estimated contribution by the sea cucumbers to the total benthic mineralization is minor. When combining data from different years/seasons we observed decoupling between the food supply to the lower slope and the upper and mid slopes. The major pulse to the former comes from an offshore summer bloom. The upper and mid slope appear to be fuelled by spring bloom material which is subsequently redistributed on the upper slope in a BNL. The quality of the seston in the BNL diminished in the offshore direction as indicated by the phytopigment concentrations.
Freshwater oligochaeta of some urban watercourses in the Russian far east
Authors: Timm Tarmo 
Published: February 2007

Abstract40 oligochaete species are identified in the lowland watercourses near Ussurijsk and Vladivostok. In the Razdol'naja River, Naididae are common, increasing in numbers in enriched urban stretches where tubificids become abundant, including Limnodrilus hoffmeisteri Claparède and Tubifex tubifex (Müller). A freshwater population of Monopylephorus rubroniveus Levinsen exists there. The endemics of the Amur zoogeographical Province, Haber amurensis (Sokol'skaja et Hrabê) and Piguetiella amurensis Sokol'skaja, are redescribed. Stylaria fossularis Leidy is a valid species. Rhyacodrilus coccineus (Vejdovsky) and its East Asian congeners form a closely related species complex. A new generic name is proposed instead Muliercula (Timm). According its oligochaete fauna, the Amur‐Japanese freshwater zoogeographical Subregion is closer to the Holarctic than to the Sino‐Indian Region.
Physico‐chemical and biological dynamics of a sewage‐polluted limestone aquifer
Authors: Malard Florian , Reygrobellet Jean‐Louis , Winiarski Thierry 
Published: February 2007

AbstractThe spatio‐temporal pattern of groundwater contamination at a 500 m2 fractured limestone site polluted with sewage effluent was investigated over two years. In the context of a previously defined conceptual groundwater flow model, a multidisciplinary approach involving the collection of physico‐chemical, bacteriological and biological (macro‐ and meiofauna) data was developed. Results showed that much of the sewage‐polluted water infiltrated rapidly through some large subvertical fractures at the site and circulated with little or no contaminant attenuation through the solution‐enlarged parts of a bedding joint. In such preferential contaminant paths, groundwater had low physico‐chemical and bacteriological “stability”, highest average contaminant concentrations, and a high epigean organism component. Observation of the spatial distribution of organisms a short period after flooding also suggested that contaminants circulating through these conductive fractures entered the adjacent small‐sized fissure matrix of the saturated zone. In this small aperture region of the site that was recharged by slow infiltrations of sewage‐polluted surface water, groundwater had a greater physico‐chemical and bacteriological “stability”, lowest average contaminant concentrations, and a high hypogean organism component. This lower sensitivity to surface pollution was partly due to attenuation processes such as retention of fecal indicator bacteria or nitrification of effluent ammonium which occurred in slow‐moving water parts of the unsaturated zone.
The effects of a change in withdrawal operations on phytoplankton and nutrient dynamics in eau galle reservoir, Wisconsin (USA)
Authors: Barbiero Richard P. , James William F. , Barko John W. 
Published: February 2007

AbstractSelective withdrawal through the surface outlet was employed in Eau Galle Reservoir to reduce phytoplankton populations by 1) strengthening thermal stability, thereby decreasing vertical entrainment of hypolimnetic phosphorus (P); and 2) increasing epilimnetic flushing rate and discharge of algae. In spite of substantial release of sediment P over the growing season, epilimnentic P concentrations were overwhelming dominated by external sources, and thus insensitive to changes in withdrawal depth. Nor did surface withdrawal increase flushing rate sufficiently to affect phytoplankton biomass. In one year, an increase in thermal stability, due in part to surface withdrawal, permitted the development of a metalimnetic chlorophyll maximum in a summer that also experienced relatively low populations of ‘nuisance’ cyanophytes, and can be regarded as a positive effect of the change in operations.
Effects of food limitation, notonectid predation, and temperature on the population dynamics of Daphnia carinata
Authors: Barry Michael J. 
Published: February 2007

AbstractThe relative contributions of invertebrate predation (Notonectidae: Anisops spp.), food limitation, and certain abiotic factors in driving the population dynamics of Daphnia carinata were studied for a two year period in a large farm dam in southern Victoria, Australia. Detailed measurements were made on the population densities of Daphnia and Anisops spp., the amount of food available, the nutritional status, and the size‐specific fecundity of Daphnia.The density of the Daphnia population at the field site oscillated closely with water temperature. The amplitude of the population fluctuations varied seasonally, being much greater during the warmer months of the year and switching to fluctuations with low peaks when water temperature dropped below approximately 15°C. Anisops spp. densities were greatest in winter and declined during the spring of each year. Nymphs appeared in late spring and early summer and numerically dominated the population. During the warmer periods of the year, the daphnid population went through a series of rapid growth phases leading to over‐exploitation of food resources and subsequent population collapses. Daphnia population densities were not correlated with Anisops numbers suggesting that predation was not a major regulatory factor during the warmer periods of the year. When water temperatures fell below ca. 15°C daphnid population densities remained low despite high food levels. During this period the impact of Anisops may have been greater. Two distinct phases were identified: a warm water period when food limitation was the main regulatory factor, and a cool water period when Anisops predation may have been the paramount factor. Low oxygen concentrations were associated with heavy rainfall in the spring and may have had a limiting effect on Daphnia for short periods. Daphnia may have had an important role in sustaining the Anisops population in the pond over each winter.
The Influence of Extremely High Concentrations of Inorganic P at Varying pH on the Growth and Photosynthesis of Unicellular Algae
Authors: Nielsen E. Steemann , Rochon T. 
Published: February 2007

AbstractAn increase in the phosphate concentration due to severe pollution is without real toxic effect for the phytoplankton in eutrophic lakes, although the various species have a variable tolerance against high concentrations. Experiments on photosynthesis and growth were made with cultures of two algae, Chlorella pyrenoidosa and Nitzcshia palea, using phosphate concentrations much higher than ever found in nature. The tolerance decreases with rising pH. This seems not to be due to a higher ratio of secondary phosphate at a high pH. Nor is the rise in the osmotic pressure apparently the cause of the decrease in the growth rate at high phosphate concentrations.
The Vertical Distribution Patterns of Heterotrophic Bacteria in the Depths of the World Ocean and the Importance of their Regularity to Oceanography
Authors: Kriss A. E. 
Published: February 2007

AbstractMany years' research into the concentration of unstable organic matter in ocean waters from many regions of the World Ocean is compiled. The relative amounts of this matter, as determined by counts of heterotrophic bacteria, are presented as three‐dimensional illustrations, depicting specific ocean areas from the surface to the sea floor. The merits of using this information in oceanography are discussed, particularly in cases where other parameters are indistinct. In many cases, this is viewed as the best method for determining the origin of water layers at various depths, and of following the movement of water masses in the ocean.
Beiträge zur Ökologie der benthischen Algen des Hochgebirges in den Pyrenäen II. Cyanophyceen und übrige Algengruppen
Authors: Backhaus Diedrich 
Published: February 2007

AbstractLittle research has been made on the litoral algal flora of unpolluted high mountain lakes and streams. Since the algal flora is often used to estimate the water quality, it is of great value to know more about the ecology of benthic forms living under extreme oligotrophic conditions.An investigation was made of the benthic and littoral microphytic vegetation of Esteragne torrent, and Lac de Port‐Bielh in the High Pyrenees. Both waters combine a low calcium content with a consistently basic pH. A comparison of their flora with that of other lakes may help to deal with the problem of whether the algal flora is determined more by the calcium content or the pH.The algal flora of Esteragne torrent differs little from that of low‐calcium streams of the central European highlands. In Lac de Porth‐Bielh there is a distinct depth‐zonation among the dominant algae. The dominant taxa at a depth of 0–0,5 metres are: Schizothrix lacustris f. lutescens, Sch. calcicola, Gloeocapsa tornensis, Pleurocapsa minor with Cyanostylon microcystoides and Hydrococcus cesatii particularly on the undersides of the stones; from 0,5 to 1,5 m: a massive growth of Nostoc zetterstedtii; from 2,5 to 4,5 m: Schizothrix funalis; from 7 m: Nitella flexilis. In addition the lake includes a number of rare and little known forms such as? Onkonema sp., of. Desmosiphon maculans, Lyngbya lachneri, Homeothrix sinensis, Chantransia chalybea v. profunda, Siphononema polonicum status chamaesiphonoides. Green algae were almost completely absent from the upper zones, in contrast to the usual findings. The littoral flora has a very distinctive character, and is not directly comparable with that usually found in lakes with either high or low calcium content. A certain resemblance to lakes with a high calcium content can be found only if all the forms present particularly with lower abundances are considered. The very strong development of lithophytes should be emphasized in contrast to their usually low density in lakes with low calcium content.The systematic section deals with systematic and taxonomic problems in a number of difficult forms.
Mathematisches Modell zur Deutung der durch intermittierende Belichtung von Phytoplanktern hervorgerufenen Mehrleistung der Photosynthese
Authors: Baumert Helmut 
Published: February 2007

AbstractIn the turbulent, turbid water body of a river, lake, reservoir or ocean, the light intensity for a phytoplankton individuum is time‐dependent. But current production equations are based on time‐independent light conditions. A mathematical model for the photosynthetic oxygen production under the simple condition of intermittent light is developed. It consists of one nonlinear algebraic and one linear differential equation of the first order. For the photosynthetic apparatus a global effective relaxation time τ is given. The model is proved with the data published by Warburg (1919). It shows, coupled with an empirical relation for τ, a good qualitative and quantitative agreement with experimental results.
Oxygen Deficits, Clarity, and Eutrophication in some Madison Lakes
Authors: Stewart Kenton M. 
Published: February 2007

AbstractOxygen deficits, rates of oxygen depletion, and Secchi disk measurements were the major indices examined in this study to determine trends in trophic conditions in Lakes Mendota, Monona, and Waubesa near Madison, Wisconsin. On the basis of available data, there is little that can be said reliably with respect to documenting eutrophication, particularly in Lake Mendota in the past several decades, that could not be attributed to normal variability. Better evidence for eutrophication comes from cores of some of the lakes.A comparison of oxygen deficits without simultaneous information on mean hypolimnetic temperatures and the lateness of ice out may provide a misleading interpretation of trophic variations over time.
Zur Bildung mathematischer Modelle limnischer Ökosysteme mittels rekursiver Schätzverfahren. Mathematical Modeling of Limnic Ecosystems with Recursive Estimation Methods
Authors: Gnauck Albrecht , Wernstedt Jürgen , Winkler Winfried 
Published: February 2007

AbstractIn the past many authors have described mathematical models of limnic ecosystems by means of differential equations and time‐stationary statistical methods. But an accurate description of the ecosystem processes is only possible by time‐varying methods. Approaching deterministic techniques often leads to hardly computable nonlinear differential equations with distributed parameters.In this paper recursive estimation methods of ecosystems modeling in real‐time are presented and first results of the application to Saidenbach reservoir are given. In practice the oxygen balance of the surface and of two lower layers (depth 10 m and 35 m) of the reservoir was modeled. The structure of all models was p‐canonic with oxygen as output and temperature, oxygen deficiency (BOD2), seston, chlorophyll, nitrate‐nitrogen, COD(Mn), phosphate (PO4) as inputs on each level. For surface model the Secchi disk‐transparency was used as an additional input.
Abschätzung von Turbulenzkorrekturen für die phytoplanktische O2‐Produktion bei schwacher Turbulenz. Estimation of Turbulence Correction Terms for the Phytoplankton Production (O2) Under Conditions of Low Turbulence
Authors: Baumert Helmut 
Published: February 2007

AbstractThe turbulence correction terms for the photosynthetic oxygen production of phytoplankton given by BAUMERT (1974) are used for the case that the variations in velocity are exponentially autocorrelated. In case of the P(I)‐relation by STEEMANN NIELSEN one can show that the value of the relative correction term is — in the worst case — less than, or equal to 1% if the depth of epilimnion (mixing depth) and the light intensity at the water surface are high.The demand for weak turbulence and light extinction — necessary for validity of the equations — is met for some real objects, especially for oligotrophic seas and lakes.
Assimilation de glucose dans la zone de divergence de Méditerranée Nord‐occidentale. Glucose Uptake in the North Western Mediterranean Divergence Zone
Authors: Cahet Guy , Jacques Guy 
Published: February 2007

AbstractConditions governing the utilization of glucose by the pelagic communities of the Northwest Mediterranean have been studied and it is concluded that (1) the vertical distribution of heterotrophic activity first reaches a maximum at about 50 m, close to the maximum of the phytoplankton while a second maximum occurs at 150 m; furthermore, within the first 200 m, the mineralization of carbon is almost complete and (2) the response of the microorganisms to increasing amounts of substrate follows the kinetic law of MICHAELIS‐MENTEN.
The Relation Between Adenosine Triphosphate and Microbial Biomass in Diverse Aquatic Ecosystems
Authors: Paerl Hans W. , Williams Noel J. 
Published: February 2007

AbstractBy using autoradiographic examination of 14C labeled viable cells, natural phytoplankton communities were separated into living and non‐living components. Comparisons of carbon to adenosine triphosphate (ATP) content of living cells yielded consistent ratios with depth, during periods of high and low nutrient supply at Lake Tahoe. Over time the ratio fluctuated by no more than ± 17% of the mean between the time of maximum nutrient supplies and nutrient depletion. The viability of specific phytoplankton groups was surprisingly low at times, indicating that conventional counting methods tend to overestimate live biomass. A survey of lakes differing in trophic states and having diverse phytoplankton and bacterial assemblages has shown that ATP measurements can be used as an accurate measure of total living microbial biomass.
An Improved Reineck Box for Sampling Coarse Sand
Authors: Farris Richard A. , Crezée M. 
Published: February 2007

AbstractA Reineck Box core sampler has been modified for quantitative use in the marine benthos. The modifications are inexpensive and easily accomplished in any machine shop. Samples have been successfully taken in medium coarse to fine sands for layer by layer analysis. The apparatus has a high degree of efficiency, takes a large volume of sediment, and produces an undisturbed core.