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1

Bacterial Community Composition in Lake Tanganyika: Vertical and Horizontal Heterogeneity  

Microsoft Academic Search

Vertical and latitudinal differences in bacterial community composition (BCC) in Lake Tanganyika were studied during the dry season of 2002 by means of denaturing gradient gel electrophoresis analysis of PCR-amplified 16S RNA fragments. Dominant bands were sequenced and identified as members of the Cyanobacteria, Actinobacteria, Nitrospirae, green nonsulfur bacteria, and Firmicutes divisions and the Gamma- and Deltaproteobacteria subdivisions. The BCC

Aaike De Wever; Koenraad Muylaert; Katleen Van der Gucht; Samuel Pirlot; Christine Cocquyt; Jean-Pierre Descy; Pierre-Denis Plisnier; Wim Vyverman

2005-01-01

2

Bacterial Community Composition in Lake Tanganyika: Vertical and Horizontal Heterogeneity  

PubMed Central

Vertical and latitudinal differences in bacterial community composition (BCC) in Lake Tanganyika were studied during the dry season of 2002 by means of denaturing gradient gel electrophoresis analysis of PCR-amplified 16S RNA fragments. Dominant bands were sequenced and identified as members of the Cyanobacteria, Actinobacteria, Nitrospirae, green nonsulfur bacteria, and Firmicutes divisions and the Gamma- and Deltaproteobacteria subdivisions. The BCC in the lake displayed both vertical and latitudinal variation. Vertical changes in BCC were related to the thermal water column stratification, which influences oxygen and nutrient concentrations. Latitudinal variation was related to upwelling of deep water and increased primary production in the south of the lake. The number of bands per sample increased with bacterial production in the epilimnion of the lake, suggesting a positive diversity-productivity relationship.

De Wever, Aaike; Muylaert, Koenraad; Van der Gucht, Katleen; Pirlot, Samuel; Cocquyt, Christine; Descy, Jean-Pierre; Plisnier, Pierre-Denis; Vyverman, Wim

2005-01-01

3

Inorganic Nitrogen Uptake and River Inputs in Northern Lake Tanganyika  

Microsoft Academic Search

Northern Lake Tanganyika is characterized by an almost permanently stratified water column which causes severe nutrient depletion in surface waters. Any external N source to surface waters, therefore, is of importance in sustaining primary production. This study attempted to quantify riverine input of dissolved inorganic nitrogen (DIN) to the extreme northern end of Lake Tanganyika (surface = 900 km2) as

Natacha Brion; Evariste Nzeyimana; Leo Goeyens; David Nahimana; Clavery Tungaraza; Willy Baeyens

2006-01-01

4

Biogeography and species diversity of diatoms in the Northern basin of Lake Tanganyika  

Microsoft Academic Search

The geographical distribution and diversity of the diatoms in the northern basin of Lake Tanganyika (historically by far the most intensively studied area of the African Great Lakes concerning this group) are examined and compared with the data available for Lake Tanganyika as a whole. Most of the diatom taxa recorded in Lake Tanganyika are cosmopolitan in distribution, but c.

C. Cocquyt

2000-01-01

5

Mating and Parental Care in Lake Tanganyika's Cichlids  

PubMed Central

Cichlid fishes of Lake Tanganyika display a variety of mating and parental care behaviors, including polygamous and monogamous mouthbrooding and substrate breeding, cooperative breeding, as well as various alternative reproductive tactics such as sneaking and piracy. Moreover, reproductive behaviors sometimes vary within species both in space and in time. Here, I survey reports on mating and parenting behaviors of Lake Tanganyika cichlid species and address the evolution of mating and parental care patterns and sexual dimorphism. Notes on measures of sexual selection intensity and the difficulties of defining mating systems and estimating selection intensities at species level conclude the essay.

Sefc, Kristina M.

2011-01-01

6

Trophic structure of Lake Tanganyika: carbon flows in the pelagic food web  

Microsoft Academic Search

The sources of carbon for the pelagic fish production in Lake Tanganyika, East Africa, were evaluated in a comprehensive multi-year study. Phytoplankton production was assessed from seasonal in situ 14C and simulated in situ results, using on-board incubator measurements and knowledge of the vertical distributions of chlorophyll and irradiance. Bacterioplankton production was measured on two cruises with the leucine incorporation

Jouko Sarvala; Kalevi Salonen; Marko Järvinen; Eero Aro; Timo Huttula; Pekka Kotilainen; Heini Kurki; Victor Langenberg; Piero Mannini; Anu Peltonen; Pierre-Denis Plisnier; Ilppo Vuorinen; Hannu Mölsä; Ossi V. Lindqvist

1999-01-01

7

Tempo and Mode of Diversification of Lake Tanganyika Cichlid Fishes  

Microsoft Academic Search

Background: Understanding the causes of disparities in species diversity across taxonomic groups and regions is a fundamental aim in evolutionary biology. Addressing these questions is difficult because of the need for densely sampled phylogenies and suitable empirical systems. Methodology\\/Principal Findings: Here we investigate the cichlid fish radiation of Lake Tanganyika and show that per lineage diversification rates have been more

Julia J. Day; James A. Cotton; Timothy G. Barraclough

2008-01-01

8

Manganese content records seasonal upwelling in Lake Tanganyika mussels  

Microsoft Academic Search

Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions

D. Langlet; L. Y. Alleman; P.-D. Plisnier; H. Hughes; L. André

2007-01-01

9

Marine Incursion: The Freshwater Herring of Lake Tanganyika Are the Product of a Marine Invasion into West Africa  

Microsoft Academic Search

The spectacular marine-like diversity of the endemic fauna of Lake Tanganyika, the oldest of the African Great Lakes, led early researchers to suggest that the lake must have once been connected to the ocean. Recent geophysical reconstructions clearly indicate that Lake Tanganyika formed by rifting in the African subcontinent and was never directly linked to the sea. Although the Lake

Anthony B. Wilson; Guy G. Teugels; Axel Meyer

2008-01-01

10

Ancient lakes as evolutionary reservoirs: evidence from the thalassoid gastropods of Lake Tanganyika.  

PubMed Central

Ancient lakes are often collectively viewed as evolutionary hot spots of diversification. East Africa's Lake Tanganyika has long been the subject of scientific interest owing to dramatic levels of endemism in species as diverse as cichlid fishes, paludomid gastropods, decapod and ostracod crustaceans and poriferans. It is the largest and deepest of the African rift lakes, and its endemic fauna has been presented with a stable inland environment for over 10 Myr, offering unique opportunities for within-lake diversification. Although astonishing diversification has been documented in the endemic cichlid fauna of the lake, similar patterns of rapid diversification have long been assumed for other groups. In contrast to this hypothesis of rapid speciation, we show here that there has been no acceleration in the rate of speciation in the thalassoid gastropods of the lake following lake colonization. While limited within-lake speciation has occurred, the dramatic conchological diversity of gastropods presently found within the lake has evolved from at least four major lineages that pre-date its formation by as much as 40 Myr. At the same time, a widespread group of African gastropods appears to have evolved from taxa presently found in the lake. While Lake Tanganyika has been a cradle of speciation for cichlid fishes, it has also been an important evolutionary reservoir of gastropod lineages that have been extirpated outside the basin.

Wilson, Anthony B.; Glaubrecht, Matthias; Meyer, Axel

2004-01-01

11

Marine Incursion: The Freshwater Herring of Lake Tanganyika Are the Product of a Marine Invasion into West Africa  

PubMed Central

The spectacular marine-like diversity of the endemic fauna of Lake Tanganyika, the oldest of the African Great Lakes, led early researchers to suggest that the lake must have once been connected to the ocean. Recent geophysical reconstructions clearly indicate that Lake Tanganyika formed by rifting in the African subcontinent and was never directly linked to the sea. Although the Lake has a high proportion of specialized endemics, the absence of close relatives outside Tanganyika has complicated phylogeographic reconstructions of the timing of lake colonization and intralacustrine diversification. The freshwater herring of Lake Tanganyika are members of a large group of pellonuline herring found in western and southern Africa, offering one of the best opportunities to trace the evolutionary history of members of Tanganyika's biota. Molecular phylogenetic reconstructions indicate that herring colonized West Africa 25–50MYA, at the end of a major marine incursion in the region. Pellonuline herring subsequently experienced an evolutionary radiation in West Africa, spreading across the continent and reaching East Africa's Lake Tanganyika during its early formation. While Lake Tanganyika has never been directly connected with the sea, the endemic freshwater herring of the lake are the descendents of an ancient marine incursion, a scenario which may also explain the origin of other Tanganyikan endemics.

Wilson, Anthony B.; Teugels, Guy G.; Meyer, Axel

2008-01-01

12

Size-specific effects of increased sediment loads on gastropod communities in Lake Tanganyika, Africa  

Microsoft Academic Search

The remarkable biodiversity of the littoral zone of Lake Tanganyika appears to be at risk through increasing sediment input caused by anthropogenic pressures. An in-situ field experiment was done to investigate the effects of increased sediment loads on the size-structure of gastropod communities on a rocky shore site in the lake. Gastropods were removed prior to the addition of sediment,

Ian Donohue; Kenneth Irvine

2004-01-01

13

Ancient Divergence in Bathypelagic Lake Tanganyika Deepwater Cichlids: Mitochondrial Phylogeny of the Tribe Bathybatini  

Microsoft Academic Search

The cichlid species flock of Lake Tanganyika represents a polyphyletic assemblage of eight ancestral lineages, which colonized the emerging lake independently. Our study is focused on one of these lineages, the Bathybatini, a tribe of specialized piscivorous cichlids of the deep pelagic zone. By analyzing three mtDNA gene segments of all eight species of the tribe and two species of

Stephan Koblmüller; Nina Duftner; Cyprian Katongo; Harris Phiri; Christian Sturmbauer

2005-01-01

14

The Lake Tanganyika cichlid species assemblage: recent advances in molecular phylogenetics  

Microsoft Academic Search

Lake Tanganyika is not the most species-rich of the Great East African Lakes, but comprises the greatest diversity of cichlid\\u000a fishes in terms of morphology, ecology, and breeding styles. The lake contains a polyphyletic assemblage of cichlid lineages,\\u000a which evolved from several ancient species that colonized the emerging lake some 9–12 million years ago. Based on morphological\\u000a characteristics, the Tanganyikan cichlids

Stephan Koblmüller; Kristina M. Sefc; Christian Sturmbauer

2008-01-01

15

The impact of the River Ntahangwa, the most polluted Burundian affluent of Lake Tanganyika, on the water quality of the lake  

Microsoft Academic Search

Sources of pollution at the north end of Lake Tanganyika are concentrated around Bujumbura, Burundi. The impact of River Ntahangwa on the water quality of this part of Lake Tanganyika was compared with that of an unpolluted river, the Mugere. A shallow bay, not influenced by a river, was used as a reference station. Chemical analyses were carried out at

A. Vandelannoote; H. Robberecht; H. Deelstra; F. Vyumvuhore; L. Bitetera; F. Ollevier

1996-01-01

16

Nuclear and mitochondrial data reveal different evolutionary processes in the Lake Tanganyika cichlid genus Tropheus  

Microsoft Academic Search

BACKGROUND: Cichlid fishes are notorious for their wealth of intra- and interspecific colour pattern diversity. In Lake Tanganyika, the endemic genus Tropheus represents the most impressive example for geographic variation in the pattern and hue of integument colouration, but the taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved. Previous studies of mitochondrial DNA

Bernd Egger; Stephan Koblmüller; Christian Sturmbauer; Kristina M Sefc

2007-01-01

17

Paleolimnological evidence for the onset and termination of glacial aridity from Lake Tanganyika, Tropical East Africa  

Microsoft Academic Search

Geochemical and sedimentological data in a continuous 60,000-year sediment core record from the Kalya horst region of central Lake Tanganyika provide a detailed history of paleoclimate-mediated weathering and overflow events from upstream Lake Kivu. Univariate (elemental profiles), bivariate (elemental ratios) and multivariate analyses of chemical trends show variations between the dry Late Pleistocene (32–18 ka cal yr BP) and the wetter

Anna A. Felton; James M. Russell; Andrew S. Cohen; Mark E. Baker; John T. Chesley; Kiram E. Lezzar; Michael M. McGlue; Jeffrey S. Pigati; Jay Quade; J. Curt Stager; Jean Jacques Tiercelin

2007-01-01

18

Assortative mating preferences between colour morphs of the endemic Lake Tanganyika cichlid genus Tropheus  

Microsoft Academic Search

Female mate preferences effectuate reproductive isolation among and sexual selection within species. Both mechanisms have\\u000a been associated with the diversification and speciation of cichlid species flocks of the East African Great Lakes. In Lake\\u000a Tanganyika, the endemic genus Tropheus has diversified into >100 geographic colour morphs. Although distributed allopatrically at present, water level fluctuations\\u000a have repeatedly displaced and merged the

Bernd Egger; Beate Obermüller; Eva Eigner; Christian Sturmbauer; Kristina M. Sefc

19

Assortative mating preferences between colour morphs of the endemic Lake Tanganyika cichlid genus Tropheus  

Microsoft Academic Search

Female mate preferences effectuate reproductive isolation among and sexual selection within species. Both mechanisms have\\u000a been associated with the diversification and speciation of cichlid species flocks of the East African Great Lakes. In Lake\\u000a Tanganyika, the endemic genus Tropheus has diversified into >100 geographic colour morphs. Although distributed allopatrically at present, water level fluctuations\\u000a have repeatedly displaced and merged the

Bernd Egger; Beate Obermüller; Eva Eigner; Christian Sturmbauer; Kristina M. Sefc

2008-01-01

20

Protist Herbivory: a Key Pathway in the Pelagic Food Web of Lake Tanganyika  

Microsoft Academic Search

Herbivory and bacterivory by phagotrophic protists were estimated in the southern basin of the oligotrophic Lake Tanganyika\\u000a at different seasons (in the rainy season in February–March 2007 and in the dry season in July–August 2006 and September 2007),\\u000a using two independent methods: the selective inhibitor technique for assessing community grazing on picocyanobacteria (PCya)\\u000a and fluorescently labelled bacteria (FLB) and Synechococcus

Anne-Laure Tarbe; Fernando Unrein; Stephane Stenuite; Samuel Pirlot; Hugo Sarmento; Danny Sinyinza; Jean-Pierre Descy

21

Ecological correlates of species differences in the Lake Tanganyika crab radiation  

Microsoft Academic Search

The endemic crabs of Lake Tanganyika include a phenotypically diverse clade that exhibits recent divergence and low phylogenetic\\u000a species resolution. There are indications that ecological niche segregation has played a prominent role in the divergence\\u000a of this clade. We used habitat surveys, gut content analyses and stable isotope analyses to test the extent to which morphological\\u000a species are ecologically different.

Saskia A. E. Marijnissen; Ellinor Michel; Marjolein Kamermans; Kim Olaya-Bosch; Moniek Kars; Daniel F. R. Cleary; E. Emiel van Loon; Paola G. Rachello Dolmen; Steph B. J. Menken

2008-01-01

22

Ecological correlates of species differences in the Lake Tanganyika crab radiation  

Microsoft Academic Search

The endemic crabs of Lake Tanganyika include a phenotypically diverse clade that exhibits recent divergence and low phylogenetic\\u000a species resolution. There are indications that ecological niche segregation has played a prominent role in the divergence\\u000a of this clade. We used habitat surveys, gut content analyses and stable isotope analyses to test the extent to which morphological\\u000a species are ecologically different.

Saskia A. E. Marijnissen; Ellinor Michel; Marjolein Kamermans; Kim Olaya-Bosch; Moniek Kars; Daniel F. R. Cleary; E. Emiel van Loon; Paola G. Rachello Dolmen; Steph B. J. Menken

23

Ecology and conservation status of endemic freshwater crabs in Lake Tanganyika, Africa  

Microsoft Academic Search

Sedimentation resulting from riparian deforestation has a wide range of detrimental effects on aquatic biodiversity, but predicting\\u000a the full consequences of such disturbances requires an understanding of the ecosystem’s key functional components. We investigated\\u000a the ecology and response to sedimentation of the diverse, endemic freshwater crabs of Lake Tanganyika, which may occupy important\\u000a positions in littoral foodwebs. Our surveys revealed

Saskia A. E. Marijnissen; Ellinor Michel; Daniel F. R. Cleary; Peter B. McIntyre

2009-01-01

24

Replicated evolution of trophic specializations in an endemic cichlid fish lineage from Lake Tanganyika  

PubMed Central

The current phylogenetic hypothesis for the endemic Lake Tanganyika cichlid fishes of the tribe Eretmodini is based solely on morphology and suggests that more complex trophic morphologies derived only once from a less specialized ancestral condition. A molecular phylogeny of eretmodine cichlids based on partial mitochondrial DNA cytochrome b and control-region sequences was used to reconstruct the evolutionary sequence of trophic adaptations and to test alternative models of morphological divergence. The six mitochondrial lineages found disagree with the current taxonomy and the morphology-based phylogeny. Mitochondrial lineages with similar trophic morphologies are not grouped monophyletically but are typically more closely related to lineages with different trophic phenotypes currently assigned to other genera. Our results indicate multiple independent origins of similar trophic specializations in these cichlids. A pattern of repeated divergent morphological evolution becomes apparent when the phylogeography of the mitochondrial haplotypes is analyzed in the context of the geological and paleoclimatological history of Lake Tanganyika. In more than one instance within Lake Tanganyika, similar morphological divergence of dentitional traits occurred in sympatric species pairs. Possibly, resource-based divergent selective regimes led to resource partitioning and brought about similar trophic morphologies independently and repeatedly.

Ruber, Lukas; Verheyen, Erik; Meyer, Axel

1999-01-01

25

Changes in species composition and abundance of commercially important pelagic fish species in Kigoma area, Lake Tanganyika, Tanzania  

Microsoft Academic Search

The pelagic fishery of Lake Tanganyika provides employment to about 1 million consumers and protein to many more people living around the lake. It is mainly based on three commercially important fish species namely two clupeids Stolothrissa tanganicae and Limnothrissa miodon commonly known as “dagaa” and a perch Lates stappersii. A declining trend of the perch both in its composition

I. A. Kimirei; Y. D. Mgaya; A. I. Chande

2008-01-01

26

Biodiversity and food chains on the littoral bottoms of Lakes Baikal, Biwa, Malawi and Tanganyika: working hypotheses  

Microsoft Academic Search

Boreal Lake Baikal, temperate Lake Biwa, and tropical Lakes Malawi and Tanganyika each possess high biodiversities of benthic\\u000a organisms in their littoral areas. Two general mechanisms influencing the evolutionary development of these high biodiversities\\u000a can be hypothesized; i.e., a bottom-up constraint depending on the availability of food resources, and a top-down effect exerted\\u000a by predators especially within the fish assemblage.

Masahide Yuma; Oleg A. Timoshkin; Natalia G. Melnik; Igor V. Khanaev; Aggrey Ambali

2006-01-01

27

Oblique-slip deformation in extensional terrains: A case study of the lakes Tanganyika and Malawi Rift Zones  

Microsoft Academic Search

The East African Rift system (EAR) is the archetypal continental rift and a widely proposed analogue for the early stages of evolution of passive continental margins. The three-dimensional structure of parts of the EAR has been recently elucidated by a multifold seismic (MFS) survey of Lakes Tanganyika and Malawi (Project PROBE). Analysis of fault geometries displayed on the PROBE MFS

Deborah L. Scott; Michael A. Etheridge; Bruce R. Rosendahl

1992-01-01

28

Reticulate phylogeny of gastropod-shell-breeding cichlids from Lake Tanganyika – the result of repeated introgressive hybridization  

Microsoft Academic Search

BACKGROUND: The tribe Lamprologini is the major substrate breeding lineage of Lake Tanganyika's cichlid species flock. Among several different life history strategies found in lamprologines, the adaptation to live and breed in empty gastropod shells is probably the most peculiar. Although shell-breeding arose several times in the evolutionary history of the lamprologines, all obligatory and most facultative shell-breeders belong to

Stephan Koblmüller; Nina Duftner; Kristina M Sefc; Mitsuto Aibara; Martina Stipacek; Michel Blanc; Bernd Egger; Christian Sturmbauer

2007-01-01

29

Thermophilic Sulfate Reduction in Hydrothermal Sediment of Lake Tanganyika, East Africa  

PubMed Central

In environments with temperatures above 60°C, thermophilic prokaryotes are the only metabolically active life-forms. By using the 35SO42- tracer technique, we studied the activity of sulfate-reducing microorganisms (SRM) in hot sediment from a hydrothermal vent site in the northern part of freshwater Lake Tanganyika (East Africa). Incubation of slurry samples at 8 to 90°C demonstrated meso- and thermophilic sulfate reduction with optimum temperatures of 34 to 45°C and 56 to 65°C, respectively, and with an upper temperature limit of 80°C. Sulfate reduction was stimulated at all temperatures by the addition of short-chain fatty acids and benzoate or complex substrates (yeast extract and peptone). A time course experiment showed that linear thermophilic sulfate consumption occurred after a lag phase (12 h) and indicated the presence of a large population of SRM in the hydrothermal sediment. Thermophilic sulfate reduction had a pH optimum of about 7 and was completely inhibited at pH 8.8 to 9.2. SRM could be enriched from hydrothermal chimney and sediment samples at 60 and 75°C. In lactate-grown enrichments, sulfide production occurred at up to 70 and 75°C, with optima at 63 and 71°C, respectively. Several sporulating thermophilic enrichments were morphologically similar to Desulfotomaculum spp. Dissimilatory sulfate reduction in the studied hydrothermal area of Lake Tanganyika apparently has an upper temperature limit of 80°C.

Elsgaard, Lars; Prieur, Daniel; Mukwaya, Gashagaza M.; J?rgensen, Bo B.

1994-01-01

30

Trace metal enrichments in Lake Tanganyika sediments: Controls on trace metal burial in lacustrine systems  

NASA Astrophysics Data System (ADS)

We investigate the distributions of several key diagenetic reactants (C, S, Fe) and redox-sensitive trace metals (Mo, Cd, Re, U) in sediments from Lake Tanganyika, East Africa. This study includes modern sediments from a chemocline transect, which spans oxygenated shallow waters to sulfidic conditions at depth, as well as ancient sediments from a longer core (˜2 m) taken at ˜900 m water depth. Modern sediments from depths spanning ˜70-335 m are generally characterized by increasing enrichments of C, S, Mo, Cd, and U with increasing water depth but static Fe distributions. It appears that the sedimentary enrichments of these elements are, to varying degrees, influenced by a combination of organic carbon cycling and sulfur cycling. These modern lake characteristics contrast with a period of high total organic carbon (C org), total sulfur (S Tot), and trace metal concentrations observed in the 900 m core, a period which follows the most recent deglaciation (˜18-11 ky). This interval is followed abruptly by an interval (˜11-6 ky) that is characterized by lower C, S, U, and Mo. Consistent with other work we suspect that the low concentrations of S, Mo, and U may indicate a period of intense lake mixing, during which time the lake may have been less productive and less reducing as compared to the present. An alternative, but not mutually exclusive, hypothesis is that changes in the lake's chemical inventory, driven by significant hydrological changes, could be influencing the distribution of sedimentary trace elements through time.

Poulson Brucker, Rebecca; McManus, James; Severmann, Silke; Owens, Jeremy; Lyons, Timothy W.

31

Nuclear and mitochondrial data reveal different evolutionary processes in the Lake Tanganyika cichlid genus Tropheus  

PubMed Central

Background Cichlid fishes are notorious for their wealth of intra- and interspecific colour pattern diversity. In Lake Tanganyika, the endemic genus Tropheus represents the most impressive example for geographic variation in the pattern and hue of integument colouration, but the taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved. Previous studies of mitochondrial DNA sequence data revealed polyphyly of the six nominally described species and complex phylogeographic patterns influenced by lake level fluctuations and population admixture, and suggested the parallel evolution of similar colour patterns in divergent evolutionary lineages. A gene tree of a rapidly radiating group may be subject to incomplete and stochastic lineage sorting, and to overcome this problem we used multi-locus, nuclear AFLP data in comparison with mtDNA sequences to study diversification, migration and introgression in Tropheus colour morphs in Lake Tanganyika. Results Significant incongruence between phylogenetic reconstructions from mitochondrial and AFLP data suggested incomplete sorting of mitochondrial haplotypes as well as frequent introgression between differentiated lineages. In contrast to the mitochondrial phylogeny, the AFLP phenogram was largely congruent with species classifications, colour pattern similarities, and in many cases also with the current geographic distribution of populations, and did not produce evidence of convergent colour pattern evolution. Homoplasy in the AFLP data was used to identify populations that were strongly affected by introgression. Conclusion Different evolutionary processes were distinguished by the combination of mitochondrial and AFLP data. Mitochondrial phylogeographic patterns retained signals of large-scale migration events triggered by historical, major lake level fluctuations, whereas AFLP data indicated genetic cohesion among local groups of populations resulting from secondary contact of adjacent populations in the course of the more frequently occurring, minor lake level fluctuations. There was no support for the parallel evolution of similar colour patterns in the AFLP data. Genetic signatures of introgression and hybridisation detected in several populations suggest that lake level fluctuations drove the stunning diversification of Tropheus morphs not only through population fragmentation, but also by promoting hybridisation between differentiated morphs in secondary contact.

Egger, Bernd; Koblmuller, Stephan; Sturmbauer, Christian; Sefc, Kristina M

2007-01-01

32

Observations on the transmission of Schistosoma haematobium and Schistosoma bovis in the Lake Region of Tanganyika  

PubMed Central

Previous investigations have shown that in the Lake Region of Sukumaland, Tanganyika, where Schistosoma haematobium is highly endemic, Bulinus (Physopsis) nasutus is responsible for the transmission of that schistosome in small, temporary rain pools. This area is one of low rainfall, and large artificial reservoirs are the chief source of water in the dry season. The role of these reservoirs in S. haematobium transmission was studied over a period of about a year. Previous work in South Africa had indicated the potential danger of bovine schistosomes to man. S. bovis is a very common parasite in cattle in the Lake Region, and a search for its intermediate host or hosts, previously unidentified, was therefore also made. The results of this double investigation suggest that large bodies of water are relatively unimportant in the transmission of both S. haematobium and S. bovis. Bulinus (Physopsis) africanus is shown to be a second intermediate of S. haematobium and a vector of S. bovis as well. Transmission of these parasites by this snail takes place principally in streams.

Kinoti, George

1964-01-01

33

The transmission of Schistosoma haematobium in an area of Lake Province, Tanganyika  

PubMed Central

This paper records the results of detailed studies carried out over a two-year period on the transmission of Schistosoma haematobium in an area of Lake Province, Tanganyika. The ecology of a variety of snail habitats is described; and data on the biology of the principal molluscan host (Bulinus (Physopsis) nasutus productus), on seasonal fluctuations in its population density and associated cercarial infection rates, on its response to desiccation and on other aspects of population dynamics are presented and discussed. Taking into consideration the seasonal fluctuation in snail numbers which occurs in the area and the snails' capacity to survive desiccation, it is considered that a substantial reduction in transmission of S. haematobium might be effected by application of a molluscicide timed so as to lower the population density before aestivation begins, followed by a second treatment when the habitats have been refilled by rainfall to reduce yet further the population that has survived the first treatment and subsequent desiccation. It is also suggested that a combination of methods directed against two stages in the schistosome life-cycle—the snail and the miracidium—by application of molluscicides and treatment of infected persons might be more efficacious than an attempt merely to reduce snail density and alter the population structure.

Webbe, G.

1962-01-01

34

Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw laterality in Lake Tanganyika scale-eating cichlids  

Microsoft Academic Search

BACKGROUND: While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid

Thomas A Stewart; R Craig Albertson

2010-01-01

35

Reticulate phylogeny of gastropod-shell-breeding cichlids from Lake Tanganyika - the result of repeated introgressive hybridization  

PubMed Central

Background The tribe Lamprologini is the major substrate breeding lineage of Lake Tanganyika's cichlid species flock. Among several different life history strategies found in lamprologines, the adaptation to live and breed in empty gastropod shells is probably the most peculiar. Although shell-breeding arose several times in the evolutionary history of the lamprologines, all obligatory and most facultative shell-breeders belong to the so called "ossified group", a monophyletic lineage within the lamprologine cichlids. Since their distinctive life style enables these species to live and breed in closest vicinity, we hypothesized that these cichlids might be particularly prone to accidental hybridization, and that introgression might have affected the evolutionary history of this cichlid lineage. Results Our analyses revealed discrepancies between phylogenetic hypotheses based on mitochondrial and nuclear (AFLP) data. While the nuclear phylogeny was congruent with morphological, behavioral and ecological characteristics, several species – usually highly specialized shell-breeders – were placed at contradicting positions in the mitochondrial phylogeny. The discordant phylogenies strongly suggest repeated incidents of introgressive hybridization between several distantly related shell-breeding species, which reticulated the phylogeny of this group of cichlids. Long interior branches and high bootstrap support for many interior nodes in the mitochondrial phylogeny argue against a major effect of ancient incomplete lineage sorting on the phylogenetic reconstruction. Moreover, we provide morphological and genetic (mtDNA and microsatellites) evidence for ongoing hybridization among distantly related shell-breeders. In these cases, the territorial males of the inferred paternal species are too large to enter the shells of their mate, such that they have to release their sperm over the entrance of the shell to fertilize the eggs. With sperm dispersal by water currents and wave action, trans-specific fertilization of clutches in neighboring shells seem inevitable, when post-zygotic isolation is incomplete. Conclusion From the direct observation of hybrids we conclude that hybridization between distantly related gastropod-shell-breeding cichlids of Lake Tanganyika follows inevitably from their ecological specialization. Moreover, the observed incongruence between mtDNA and nuclear multilocus phylogeny suggests that repeated hybridization events among quite distantly related taxa affected the diversification of this group, and introduced reticulation into their phylogeny.

Koblmuller, Stephan; Duftner, Nina; Sefc, Kristina M; Aibara, Mitsuto; Stipacek, Martina; Blanc, Michel; Egger, Bernd; Sturmbauer, Christian

2007-01-01

36

Distinct population structure in a phenotypically homogeneous rock-dwelling cichlid fish from Lake Tanganyika  

Microsoft Academic Search

Several lineages of cichlid fishes in the East African Great Lakes display stunning levels of morphological diversification. The rapid evolution of rock-dwelling polygynous mouthbrooders in Lake Malawi, for example, was in part ascribed to their allopatric distribu- tion on disjunct stretches of rocky coast, where even short habitat discontinuities reduce gene flow effectively. However, as seen in other cichlids, ecological

NINA DUFTNER; KRISTINA M. S EFC; STEPHAN KOBLMÜLLER; BRUNO NEVADO; ERIK VERHEYEN; HARRIS PHIRI; CHRISTIAN STURMBAUER

2006-01-01

37

Possible effects of global climate change on the ecosystem of Lake Tanganyika  

Microsoft Academic Search

Any change in the air temperature, wind speed, precipitation, and incoming solar radiation induced by increasing greenhouse\\u000a gasses and climate change will directly influence lakes and other water bodies. The influence can cause changes in the physical\\u000a (water temperature, stratification, transparency), chemical (nutrient loading, oxygen) and biological (structure and functioning\\u000a of the ecosystem) components of the Lake. In this work

Jaya Naithani; Pierre-Denis Plisnier; Eric Deleersnijder

2011-01-01

38

Discharge of forested and deforested watersheds on the northeastern shores of Lake Tanganyika, Tanzania  

Microsoft Academic Search

The purpose of this study was to measure discharge as the product of the mean current velocity and vertical cross-sectional area of flowing water (USEPA 2004). The variables isolated and measured in this study included stream discharge, water depth, cobble size and distance between samples, from which we calculated discharge using three different methods. These methods included the \\

Joanna Souers; Catherine O'Reilly

39

The genus Argulus (Crustacea: Branchiura) in Africa: redescriptions of type-material collected by W.A. Cunnington during the Lake Tanganyika Expedition in 1913, with notes on A. giganteus Lucas and A. arcassonensis Cuénot  

Microsoft Academic Search

Of the 11 specimens of Argulus Müller, 1785 examined during the present study, nine are recognised as valid. The two-specimens collected by W.A. Cunnington (1913) during the Expedition to Lake Tanganyika are redescribed. In these redescriptions, many species-specific features have been identified which facilitate identification when comparing with all other species of Argulus recorded from Africa. The type-material of A.

Sophie K. Rushton-Mellor

1994-01-01

40

Characterizing Seasonal Habitat Use and Diel Vertical Activity of Lake Whitefish in Clear Lake, Maine, as Determined with Acoustic Telemetry  

Microsoft Academic Search

Seasonal and daily vertical activity of lake whitefish Coregonus clupeaformis was studied in Clear Lake, Maine (253 ha), using acoustic telemetry from November 2004 to June 2009. Twenty adult lake whitefish were tagged with acoustic tags that had either a depth sensor or both depth and temperature sensors to assess vertical habitat use at a seasonal and daily resolution. Vertical

Dimitry Gorsky; Joseph Zydlewski; David Basley

2012-01-01

41

Numerical modeling of vertical stratification of Lake Shira in summer  

Microsoft Academic Search

A one-dimensional numerical model and a two-dimensional numerical model of the hydrodynamic and thermal structure of Lake\\u000a Shira during summer have been developed, with several original physical and numerical features. These models are well suited\\u000a to simulate the formation and dynamics of vertical stratification and provide a basis for an ecological water-quality model\\u000a of the lake. They allow for the

Pavel V. BelolipetskyVictor; Victor M. Belolipetskii; Svetlana N. Genova; Wolf M. Mooij

2010-01-01

42

Vertical mixing of lake sediments by tubificid oligochaetes  

SciTech Connect

Vertical mixing of lake sediments by tubificid oligochaetes was studied in laboratory experiments by using a radioactive (cesium 137 labeled sediment) marker horizon. Results from these experiments were used to develop and test a mathematical model describing tubificid sediment mixing as a dominantly advective process. Tubificids were found to mix sediments to a depth of 6--9 cm. The rate of tubificid sediment processing observed in the experiments agrees well with those reported by other workers. Extrapolation of laboratory results to Lake Erie shows that the feeding activity of tubificids alone may result in significant sediment mixing throughout the lake.

Fisher, J.B.; Lick, W.J.; McCall, P.L.; Robbins, J.A.

1980-07-20

43

Vertical and Seasonal Distribution of Chlorophyll alpha in Lake Michigan.  

National Technical Information Service (NTIS)

Vertical and seasonal distribution of chlorophyll alpha was observed for 2 yr at an offshore station in Lake Michigan. Chlorophyll alpha concentrations increased uniformly at all depths during spring reaching 3-4 mg/cu m by late May. Thermal stratificatio...

A. S. Brooks B. G. Torke

1977-01-01

44

VERTICAL DIFFUSION IN SMALL STRATIFIED LAKES: DATA AND ERROR ANALYSIS  

EPA Science Inventory

Water temperature profiles were measured at 2-min intervals in a stratified temperate lake with a surface area of 0.06 km2 and a aximum depth of 10 m from May 7 to August 9, 1989. he data were used to calculate the vertical eddy diffusion coefficient K2 in the hypolimnion. he dep...

45

Vertical mixing of lake sediments by tubificid oligochaetes  

Microsoft Academic Search

Vertical mixing of lake sediments by tubificid oligochaetes was studied in laboratory experiments by using a radioactive (cesium 137 labeled sediment) marker horizon. Results from these experiments were used to develop and test a mathematical model describing tubificid sediment mixing as a dominantly advective process. Tubificids were found to mix sediments to a depth of 6--9 cm. The rate of

J. B. Fisher; W. J. Lick; P. L. McCall; J. A. Robbins

1980-01-01

46

Vertical light attenuation and phytoplankton development in Lake Zurich  

Microsoft Academic Search

Many light-depth profiles based on measurements of photosynthetically available radiation (PAR) in the 0-20-m zone ofLake Zurich were analyzed with respect to phytoplankton development in the epilimnion and the thermocline. Variations in the average value of the vertical attenuation coefficient with time were closely related to variations in biomass. Inspection of the depth distri- bution of the natural logarithms of

FERDINAND SCHANZ

1985-01-01

47

The Tanganyika Library Service.  

National Technical Information Service (NTIS)

The history, services, reading habits, and statistics are given for the Tanganyika public libraries. The conclusions of the study were that most Africans tend to read for utilitarian purposes and not for recreation or self-development, that there is littl...

E. E. Kaungamno

1971-01-01

48

Infestation and Pathological Alterations by Ergasilus sarsi (Copepoda) on the Tanganyika Killifish from Africa  

PubMed Central

A total of 204 Ergasilus sarsi, a copepod, were collected from Tanganyika Killifish Lamprichthys tanganicanus in Lake Tanganyika during March 2010. The prevalence was 86.40%, the mean intensity was 7.56, and the mean abundance was 6.38. Only 27 of the fish were infested, and the highest infestation on one fish was 29. Proliferation of mucus cells and lamellar fusion occurred. Haemorrhage due to blood vessel compression was noted. This is the first record of E. sarsi from Tanganyika Killifish. This study is also the first to provide a description of the pathological alterations caused by E. sarsi.

Kilian, Esmari; Avenant-Oldewage, Annemarie

2013-01-01

49

Dynamics of vertical mixing in a shallow lake with submersed macrophytes  

Microsoft Academic Search

A model for vertical turbulent diffusion and stratification in a shallow lake with submersed macrophytes is formulated on the basis of a one-dimensional equation for production, transport, and dissipation of turbulent kinetic energy, coupled with a vertical heat transfer equation. Numerical solutions of the coupled equations allow simulation of the hourly variation of water temperature profiles in a shallow lake

William R. Herb; Heinz G. Stefan

2005-01-01

50

A one-dimensional model of vertical stratification of Lake Shira focussed on winter conditions and ice cover  

Microsoft Academic Search

In meromictic lakes such as Lake Shira, horizontal inhomogeneity is small in comparison with vertical gradients. To determine\\u000a the vertical distribution of temperature, salinity, and density of water in a deep zone of a Lake Shira, or other saline lakes,\\u000a a one-dimensional (in vertical direction) mathematical model is presented. A special feature of this model is that it takes\\u000a into

S. N. Genova; V. M. Belolipetskii; D. Y. Rogozin; A. G. Degermendzhy; W. M. Mooij

2010-01-01

51

Vertical distribution and rotifer concentrations in the chemocline of meromictic lakes  

Microsoft Academic Search

The vertical distribution of planktonic rotifers has been analysed in relation to season in several meromictic lakes; a coastal lagoon with sea-water intrusion and three dissolution lakes from two karstic systems. Two species, Filinia hofmanni and a form of Anuraeopsis fissa have been found to be more or less restricted to the chemocline or adjacent strata any time they occurred.

María R. Miracle; Eduardo Vicente

1983-01-01

52

A model of the vertical mixing in Lake Erie in summer  

Microsoft Academic Search

A vertical one-dimensional model is proposed to describe the vertical mixing in the central portion of the central basin of Lake Erie in summer. The model explicitly describes the various mechanisms which operate in the well mixed upper and bottom layers. The model predictions are in good agreement with the observed thermal structure over the entire water column during a

G. N. IVEY; J. C. PATTERSON

1984-01-01

53

Vertical transport of mercury in a Wisconsin seepage lake  

SciTech Connect

During summer stratification, dissolved and particulate mercury species reach maxima in oxygen-depleted, sulfide-rich bottom water of a Wisconsin seepage lake. Initially, it appeared that this hypolimnetic build-up was due to redox-controlled release from bottom sediments. However, Hg did not increase near the bottom sediments during winter anoxia, when lakes are sealed from atmospheric inputs and biological productivity is low. In contrast, Fe shows both a summer and winter build-up with depth. Reinterpretation of depth profiles using seston distributions and sediment trap collections suggests that hypolimnetic enrichment may result from the transport of epilimnetic Hg to deeper waters via biotic particles. Furthermore, a preliminary Hg mass balance for the ice-free season shows that atmospheric inputs are the dominant source of Hg to the lakes and that Hg inputs are removed by sedimentation. Mercury-rich biotic particles tend to accumulate in layers at depth through both settling and in situ growth. We hypothesize that recycling of Hg within these deep plankton layers has a strong influence on the distribution and speciation of Hg in these lakes.

Hurley, J.P. (Univ. of Wisconsin, Madison (United States)); Watras, C.J. (Univ. of Wisconsin, Boulder Junction (United States))

1990-01-09

54

Water and gas chemistry at Lake Kivu (DRC): Geochemical evidence of vertical and horizontal heterogeneities in a multibasin structure  

Microsoft Academic Search

Waters and dissolved gases collected along vertical profiles in the five basins (Main, Kabuno Bay, Kalehe, Ishungu, and Bukavu) forming the 485 m deep Lake Kivu (Democratic Republic of the Congo) were analyzed to provide a geochemical conceptual model of the several processes controlling lake chemistry. The measured horizontal and vertical variations of water and gas compositions suggest that each

F. Tassi; O. Vaselli; D. Tedesco; G. Montegrossi; T. Darrah; E. Cuoco; M. Y. Mapendano; R. Poreda; A. Delgado Huertas

2009-01-01

55

Vertical stratification of physical, chemical and biological components in two saline lakes Shira and Shunet (South Siberia, Russia)  

Microsoft Academic Search

A feature of meromictic lakes is that several physicochemical and biological gradients affect the vertical distribution of\\u000a different organisms. The vertical stratification of physical, chemical and biological components in saline, fishless meromictic\\u000a lakes Shira and Shunet (Siberia, Russia) is quite different mainly because both mean depth and maximum depth of lakes differ\\u000a as well as their salinity levels differ. The

Andrey G. DegermendzhyEgor; Egor S. Zadereev; Denis Yu. Rogozin; Igor G. Prokopkin; Yuri V. Barkhatov; Alexander P. Tolomeev; Elena B. Khromechek; Jan H. Janse; Wolf M. Mooij; Ramesh D. Gulati

2010-01-01

56

Vertical distribution of brown trout ( Salmo Trutta ) and perch ( Perca Fluviatilis ) in an acidified lake  

Microsoft Academic Search

Brown trout (Salmo trutta) and perch (Perca fluviatilis) had different vertical distributions throughout the year in the acidified lake Gjerstadvann. During summer, the brown trout lived in the 0 to 16 m depth interval, whereas the perch lived in the 0 to 8 m interval. In Gjerstadvann, the thermocline lies at 8 to 10 m depth. The epilimnion pH was

Arne Linløkken; Hedmark County

1988-01-01

57

[Vertical distribution characteristics of nutrients and heavy metals in sediments of Lake Hongze].  

PubMed

In order to understand the vertical distribution characteristics of nutrients and heavy metals in sediments of Lake Hongze, three core sediment samples at 3 sites (one near the Huaihe River inlet of Lake Hongze, one at the western part of the lake and one at the lake center) were collected in June of 2008. By measurement of total nitrogen (TN), total phosphorus (TP) and heavy metals (Cu, Zn, Pb, Cd, Fe, Al, Cr, Hg, Mn, As) and by analyzing of their vertical characteristics, investigation revealed the nutrient evolution processes and pollution history. Sediment near Huaihe river mouth was more polluted by the Huaihe River watershed. The nutrients TN, TP and organic matter (OM) concentrations in this core sample were 390.8-643.7, 428.6-538.6, 5 194.3-9 164.9 mg x kg(-1) respectively. Zn, Cd, Al, Fe and Mn in the sediment in this area were affected by human activities less than other heavy metals. Western Lake sediment was affected by the Huaihe River, inlet river and human activities in cities along western lake shoreline. TN, TP and OM concentrations in this core sample were 633.4-2 677.3, 480.0-1115.9, 7 140.8-47 849.7 mg x kg(-1) respectively. The pollution extents of TN, OM and heavy metals in sediment were exacerbated since the late of 1970s, but the situation was improved since the 1990s. As and Cr in the sediments were influenced by human activities more than other heavy metals. Main pollution source in sediment at the lake center were detritus from the lake watershed. TN, TP and OM concentrations in this core sample were 904.7-1 585.4, 526.3-750.1, 10 635.6-19 020.6 mg x kg(-1) respectively. The correlations among nutrients and heavy metals in sediment are significant, and their vertical distribution patterns were similar. The concentrations of nutrients and heavy metals increased from bottom to surface. Nutrients and heavy metal pollution in sediment had the same vertical distribution characteristics which coincided with the lake watershed economic development stage. The sediment in Lake Hongze can be described by the Turbidity Flood Model. PMID:22509573

Zhang, Wen-Bin; Yu, Hui

2012-02-01

58

Vertical distribution of a deep-water moss and associated epiphytes in Crater Lake, Oregon  

USGS Publications Warehouse

A one-person submersible was used to examine the vertical distribution of the deep-water moss Drepanocladus aduncus (Hedw.) Warnst in Crater Lake (Oregon). Living specimens were found attached to sediment and rocks at depths between 25 m and 140 m. Dense beds of the moss were observed at depths between 30 m and 80 m, a region that corresponded roughly to the zone of maximum primary production by phytoplankton. The moss population supported a diverse assemblage of epiphytic algae, of which the most abundant genera included Cladophora,Oedogonium, Rhizoclonium, Tribonema, Vaucheria, and the diatoms Cocconeis, Cymbella, Epithemia, Fragilaria, Gomphonema, Melosira, Navicula, and Synedra. Chemical and physical data supported the hypothesis that the lower limit of distribution of the moss is determined by light limitation, whereas the upper limit is related to the availability of nutrients, particularly nitrate-nitrogen and trace elements. Deep-water videotapes of the moss population indicated that D. aduncus with its epiphytic algae was abundant enough in regions associated with the metalimnion and upper hypolimnion to have a potential influence on the nutrient dynamics of the Crater Lake ecosystem. Although the maximum depth at which living bryophytes occur in Crater Lake is similar to that found for Lake Tahoe, conditions in Lake Tahoe allow the growth and survival of a much more diverse assemblage of bryophytes and charophytes than is present in Crater Lake.

McIntire, C. D.; Phinney, H. K.; Larson, Gary L.; Buktenica, M. W.

1994-01-01

59

Studies on the mycoflora of Aswan High Dam Lake, Egypt: vertical fluctuations.  

PubMed

The fungal population of Aswan High Dam Lake showed marked vertical variations during the period of study which extended from July 1985 to December 1986. High fungal counts were observed at the surface water which were mainly due to the high counts of Aspergillus fumigatus and A. terreus. Going deeper the fungal population decreased till 30 meters, then gradually increased to reach its maximum at the 70 meter depth (near the bottom of the lake). Such increase was basically due to the high population of Penicillium funiculosum. At each sampling time, the water temperature and the values of dissolved oxygen were always higher at the surface than near the bottom of the lake. The temperature ranged from 15 degrees to 26 degrees C and the dissolved oxygen from 1.31 to 8.98 mg 1(-1). PMID:2370640

Moharram, A M; el-Hissy, F T; el-Zayat, S A

1990-01-01

60

Tracer experiment with sulfur hexafluoride to quantify the vertical transport in a meromictic pit lake  

Microsoft Academic Search

This paper describes a tracer experiment with sulfurhexafluoride (SF6) in the monimolimnion of the meromictic mining lake Merseburg-Ost 1b. In October 1998, 1.1 mmol (~ 160 mg) of the conservative gas SF6 was released at the site of greatest depth 3.5 m above the sediment to observe its vertical spreading. An easy-to-use system to collect ~0.5 L water samples using

Christoph von Rohden; Johann Ilmberger

2001-01-01

61

Vertical profiles of organochlorine pesticides in sediment core from Nile river and Manzala lake, Egypt  

Microsoft Academic Search

Residue levels of organochlorine pesticides (DDTs, HCHs, HCB and chlordane compounds) were determined in core samples collected from Nile River near by Cairo and Manzala Lake, Egypt in 1994. Regional difference and vertical profiles were discussed in view of historical reconstruction of environmental pollution by these chemicals. On the basis of estimated sedimentation rate (0.5 to 0.7 cm\\/year) in Manzala

Nobuyoshi Yamashita; Shigeki Masunaga; Mohamed S. Rizk; Yoshikuni Urushigawa

1997-01-01

62

Vertical segregation and phylogenetic characterization of ammonia-oxidizing Archaea in a deep oligotrophic lake.  

PubMed

Freshwater habitats have been identified as one of the largest reservoirs of archaeal genetic diversity, with specific lineages of ammonia-oxidizing archaea (AOA) populations different from soils and seas. The ecology and biology of lacustrine AOA is, however, poorly known. In the present study, vertical changes in archaeal abundance by CARD-FISH, quantitative PCR (qPCR) analyses and identity by clone libraries were correlated with environmental parameters in the deep glacial high-altitude Lake Redon. The lake is located in the central Spanish Pyrenees where atmospheric depositions are the main source of reactive nitrogen. Strong correlations were found between abundance of thaumarchaeotal 16S rRNA gene, archaeal amoA gene and nitrite concentrations, indicating an ammonium oxidation potential by these microorganisms. The bacterial amoA gene was not detected. Three depths with potential ammonia-oxidation activity were unveiled along the vertical gradient, (i) on the top of the lake in winter-spring (that is, the 0?(o)C slush layers above the ice-covered sheet), (ii) at the thermocline and (iii) the bottom waters in summer-autumn. Overall, up to 90% of the 16S rRNA gene sequences matched Thaumarchaeota, mostly from both the Marine Group (MG) 1.1a (Nitrosoarchaeum-like) and the sister clade SAGMGC-1 (Nitrosotalea-like). Clone-libraries analysis showed the two clades changed their relative abundances with water depth being higher in surface and lower in depth for SAGMGC-1 than for MG 1.1a, reflecting a vertical phylogenetic segregation. Overall, the relative abundance and recurrent appearance of SAGMGC-1 suggests a significant environmental role of this clade in alpine lakes. These results expand the set of ecological and thermal conditions where Thaumarchaeota are distributed, unveiling vertical positioning in the water column as a key factor to understand the ecology of different thaumarchaeotal clades in lacustrine environments. PMID:22495069

Auguet, Jean-Christophe; Triadó-Margarit, Xavier; Nomokonova, Natalya; Camarero, Lluís; Casamayor, Emilio O

2012-04-12

63

Formation of the vertical heterogeneity in the Lake Shira ecosystem: the biological mechanisms and mathematical model  

Microsoft Academic Search

Data on the seasonal changes in vertical heterogeneity of the physical-chemical and biological parameters of the thermally stratified Shira Lake ecosystem (Khakasia, Siberia) in 1996–2000 have been analyzed. The interaction mechanisms involving: (1) The plankton populations in aerobic and anaerobic zones, involving the cycling of carbon and sulphur, (2) the primary production limitation (by light and phosphorus) and inhibition (by light), and

Andrei G. Degermendzhy; Victor M. Belolipetsky; Tatiana A. Zotina; Ramesh D. Gulati

2002-01-01

64

Diel changes in vertical overlap between Cyclops strenuus (Copepoda; Cyclopoida) and its prey in oligotrophic Lake Toya, Hokkaido, Japan  

Microsoft Academic Search

The vertical distribution of Cyclops strenuus and its prey, and the gut contents of C. strenuus were investigated at 3 h intervals over 24 h periods in the pelagic area of oligotrophic Lake Toya in May, August and October 1992. C. strenuus showed slight diel vertical migration (DVM) in May, but did not migrate and was always distributed below 15

Wataru Makino; Syuhei Ban

1998-01-01

65

Politics and Business in the Indian Newspapers of Colonial Tanganyika  

Microsoft Academic Search

This article examines the history of two Indian newspapers, Tanganyika Opinion and Tanganyika Herald, to demonstrate how business considerations provided both the opportunity for East African Indians to make public arguments and the central limitation on the arguments that could be made. Founded on the inspiration of mass nationalist action through a territorial hartal, the Tanganyika Opinion and later the

James R. Brennan

2011-01-01

66

River and landslide dynamics on the western Tanganyika rift border, Uvira, D.R. Congo: diachronic observations and a GIS inventory of traces of extreme geomorphologic activity  

Microsoft Academic Search

Uvira occupies a series of narrow alluvial fans squeezed between the NW corner of Lake Tanganyika (±710 m asl) and the W-shoulder\\u000a of the Tanganyika rift, the Itombwe–Mitumba Plateau (±3,000 m asl). In 50 years, the fans progressed into the lake over distances\\u000a up to some hundreds of metres. This happened during a few catastrophic flash floods issued from the torrents which cascade\\u000a from the

J. Moeyersons; Ph. Trefois; L. Nahimana; L. Ilunga; I. Vandecasteele; V. Byizigiro; S. Sadiki

2010-01-01

67

Vertical distribution of microbial communities in a perennially stratified Arctic lake with saline, anoxic bottom waters  

PubMed Central

Meromictic lakes are useful biogeochemical models because of their stratified chemical gradients and separation of redox reactions down the water column. Perennially ice-covered meromictic lakes are particularly stable, with long term constancy in their density profiles. Here we sampled Lake A, a deep meromictic lake at latitude 83°N in High Arctic Canada. Sampling was before (May) and after (August) an unusual ice-out event during the warm 2008 summer. We determined the bacterial and archaeal community composition by high-throughput 16S rRNA gene tag-pyrosequencing. Both prokaryote communities were stratified by depth and the Bacteria differed between dates, indicating locally driven selection processes. We matched taxa to known taxon-specific biogeochemical functions and found a close correspondence between the depth of functional specialists and chemical gradients. These results indicate a rich microbial diversity despite the extreme location, with pronounced vertical structure in taxonomic and potential functional composition, and with community shifts during ice-out.

Comeau, Andre M.; Harding, Tommy; Galand, Pierre E.; Vincent, Warwick F.; Lovejoy, Connie

2012-01-01

68

Vertical distribution of nitrogen-fixing phylotypes in a meromictic, hypersaline lake.  

PubMed

We investigated the diversity of nitrogenase genes in the alkaline, moderately hypersaline Mono Lake, California to determine (1) whether nitrogen-fixing (diazotrophic) populations were similar to those in other aquatic environments and (2) if there was a pattern of distribution of phylotypes that reflected redox conditions, as well as (3) to identify populations that could be important in N dynamics in this nitrogen-limited lake. Mono Lake has been meromictic for almost a decade and has steep gradients in oxygen and reduced compounds that provide a wide range of aerobic and anaerobic habitats. We amplified a fragment of the nitrogenase gene (nifH) from planktonic DNA samples collected at three depths representing oxygenated surface waters, the oxycline, and anoxic, ammonium-rich deep waters. Forty-three percent of the 90 sequences grouped in nifH Cluster I. The majority of clones (57%) grouped in Cluster III, which contains many known anaerobic bacteria. Cluster I and Cluster III sequences were retrieved at every depth indicating little vertical zonation in sequence types related to the prominent gradients in oxygen and ammonia. One group in Cluster I was found most often at every depth and accounted for 29% of all the clones. These sequences formed a subcluster that contained other environmental clones, but no cultivated representatives. No significant nitrogen fixation was detected by the 15N2 method after 48 h of incubation of surface, oxycline, or deep waters, suggesting that pelagic diazotrophs were contributing little to nitrogen fluxes in the lake. The failure to measure any significant nitrogen fixation, despite the detection of diverse and novel nitrogenase genes throughout the water column, raises interesting questions about the ecological controls on diazotrophy in Mono Lake and the distribution of functional genes in the environment. PMID:15259267

Steward, G F; Zehr, J P; Jellison, R; Montoya, J P; Hollibaugh, J T

2004-01-01

69

Vertical and temporal microbial community patterns in a meromictic coastal lake influenced by the Straits of Messina upwelling system  

Microsoft Academic Search

The vertical and temporal dynamics of total picoplankton, heterotrophic nanoflagellates and ciliates were monitored monthly\\u000a from May 2002 to April 2003, along with environmental parameters, in Lake Faro, a meromictic coastal basin characterized by\\u000a a permanently anoxic monimolimnion and sulfide-rich bottom waters. A two-layer discrimination was delineated in the water\\u000a column of the lake, based on the correlations between environmental

Alessandro Saccà; Letterio Guglielmo; Vivia Bruni

2008-01-01

70

Factors determining growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2.7)  

Microsoft Academic Search

In this thesis, I investigated the factors influencing the growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2-3). In the focal study site, Lake 111 (pH 2.7; Lusatia, Germany), the chrysophyte, Ochromonas sp., dominates in the upper water strata and the chlorophyte, Chlamydomonas sp., in the deeper strata, forming a pronounced deep chlorophyll maximum (DCM).

Vera Bissinger

2003-01-01

71

Vertical structure of small eukaryotes in three lakes that differ by their trophic status: a quantitative approach  

Microsoft Academic Search

In lakes, the diversity of eukaryotic picoplankton has been recently studied by the analysis of 18S ribosomal RNA gene sequences; however, quantitative data are rare. In this study, the vertical structure and abundance of the small eukaryotic size fraction (0.2–5 ?m) were investigated in three lakes by tyramide signal amplification–fluorescent in situ hybridization targeting six phylogenetic groups: Chlorophyta, Haptophyta, Cercozoa,

Cecile Lepère; Sylvie Masquelier; Jean-François Mangot; Didier Debroas; Isabelle Domaizon

2010-01-01

72

Unique qualities and special problems of the African Great Lakes  

Microsoft Academic Search

The African Great Lakes consist of large, deep rift valley lakes (e.g. Malawi & Tanganyika) and shallower lakes between the Eastern and Western Rifts (e.g. Victoria). They are a group comparable in size to the North American Great Lakes, but are old. Most are seasonally thermally stratified, and wind is the decisive factor that determines the annual cycle of cooling

George W. Coulter; Brian R. Allanson; Michael N. Bruton; P. Humphry Greenwood; Robert C. Hart; Peter B. N. Jackson; Anthony J. Ribbink

1986-01-01

73

Zooplankton grazing in a eutrophic lake: implications of diel vertical migration. [Scenedesmus; Eudiaptomus; Daphnia; Ceriodaphnia; Synechococcus  

SciTech Connect

During summer and fall, depth profiles of zooplankton community grazing were determined in situ during day and night in the Schoehsee, a small eutrophic lake. Labeled algae of two different sizes were mixed with the natural suspension of phytoplankton in a grazing chamber. A small blue-green alga (Synechococcus, 1 ..mu..m) was labeled with /sup 32/P; a larger green alga (Scenedesmus, 4-15 ..mu..m) was labeled with /sup 14/C. During summer, grazing in the upper 5 m was negligible during day but strong at night. Hence, algae grow relatively unimpeded by grazing during daytime but are harvested at night. Vertical and diel differences in grazing rates disappeared when the vertical migration ceased in fall. Selectivity of grazing was controlled by the zooplankton species composition. Eudiaptomus showed a strong preference for Scenedesmus. Daphnia showed a slight preference for Scenedesmus, but Ceriodaphnia preferred Synechococcus. Cyclopoid copepodites did not ingest the small blue-green. Because Daphnia and Eudiaptomus were dominant, grazing rates on larger cells were usually higher than grazing rates on the small cells. Negative electivity indices for scenedesmus occurred only when the biomass of large crustaceans was extremely low (near the surface, during day). Zooplankton biomass was the main factor controlling both vertical and seasonal variations in grazing. Highest grazing rates (65%/d) were measured during fall when zooplankton abundance was high. Because differential losses can produce substantial errors in the results, it was necessary to process the samples on the boat immediately after collection, without preservation.

Lampert, W.; Taylor, B.E.

1985-02-01

74

Vertical distribution of ammonia-oxidizing archaea and bacteria in sediments of a eutrophic lake.  

PubMed

In order to characterize the vertical variation of abundance and community composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in sediments of a eutrophic lake, Lake Taihu, molecular techniques including real-time PCR, clone library, and sequencing were carried out in this study. Abundances of archaeal amoA gene (ranged from 2.34 × 10(6) to 4.43 × 10(7) copies [g dry sediment](-1)) were higher than those of bacterial amoA gene (ranged from 5.02 × 10(4) to 6.91 × 10(6) copies [g dry sediment](-1)) for all samples and both of them exhibited negative correlations with the increased depths. Diversities of archaeal and bacterial amoA gene increased with the elevated depths. There were no significant variations of AOB community structures derived from different sediment depths, whereas obvious differences were observed for the AOA community compositions. The information acquired in this study would be useful to elucidate the roles of AOA and AOB in the nitrogen cycling of freshwater ecosystems. PMID:23636492

Zhao, Dayong; Zeng, Jin; Wan, Wenhua; Liang, Huidi; Huang, Rui; Wu, Qinglong L

2013-05-01

75

Do Daphnia use metalimnetic organic matter in a north temperate lake? An analysis of vertical migration  

USGS Publications Warehouse

Diel vertical migration of zooplankton is influenced by a variety of factors including predation, food, and temperature. Research has recently shifted from a focus on factors influencing migration to how migration affects nutrient cycling and habitat coupling. Here we evaluate the potential for Daphnia migrations to incorporate metalimnetic productivity in a well-studied northern Wisconsin lake. We use prior studies conducted between 1985 and 1990 and current diel migration data (2008) to compare day and night Daphnia vertical distributions with the depth of the metalimnion (between the thermocline and 1% light depth). Daphnia migrate from a daytime mean residence depth of between about 1.7 and 2.5 m to a nighttime mean residence depth of between 0 and 2.0 m. These migrations are consistent between the prior period and current measurements. Daytime residence depths of Daphnia are rarely deep enough to reach the metalimnion; hence, metalimnetic primary production is unlikely to be an important resource for Daphnia in this system.

Brosseau, Chase Julian; Cline, Timothy J.; Cole, Jonathan J.; Hodgson, James R.; Pace, Michael L.; Weidel, Brian C.

2012-01-01

76

Biology of the African clupeid Limnothrissa miodon with reference to its small size in artificial lakes  

Microsoft Academic Search

Summary Limnothrissa miodon is a clupeid from Lake Tanganyika which has been introduced to Lakes Kivu and Kariba and which invaded Lake Cahora Bassa. These lakes differ considerably from one another but the biology of Limnothrissa is similar in many respects in all of them. Similarities include its feeding and breeding biology, whilst its populations fluctuate, on both an annual

B. E. Marshall

1993-01-01

77

Investigation of the vertical distribution of major and trace elements in Matita Lake (Danube Delta) sediments by activation analysis  

Microsoft Academic Search

The vertical profiles of two major elements (Na and Ca) and 24 trace elements (Rb, Cs, Sr, Ba, Sc, La, Ce, Sm, Eu, Tb, Yb,\\u000a Lu, Th, U, Hf, Nb, Ta, Cr, Fe, Co, Zn, As, Sb and Br) have been investigated by neutron activation analysis in a 2.5 m core\\u000a collected from the Danube Delta, Matita Lake. The data

L. C. Dinescu; O. G. Duliu; M. Badea; N. G. Mihãilescu; I. M. Vanghelie

1998-01-01

78

Classification and dynamic simulation of the vertical density structure of lakes  

Microsoft Academic Search

Field data from two lakes of widely differing geometry and size are analyzed in terms of four nondimensional numbers which allow the principal mixing processes in each lake to be identified. The numbers are based on basin geometry, density stratification, wind stress, and rates of inflow and outflow. The procedure highlights the differences in the dynamics of the two lakes

J. C. PATTERSON; P. F. HAMBLIN; J. IMBERGER

1984-01-01

79

The Nyanza Project: Interdisciplinary Research Training In Tropical Lakes  

Microsoft Academic Search

The Nyanza Project is a research training program for American and African students, run annually at Lake Tanganyika (LT), Tanzania. The Project`s objective is to provide undergraduates, graduate students and secondary school teachers with the skills to plan and conduct interdisciplinary research on various aspects of tropical lake studiees. At a time of rapid global change there is a pressing

A. S. Cohen; K. E. Lezzar; E. Michel; C. M. O'Reilly; J. M. Russell; H. Nkotagu; I. Kimirei

2005-01-01

80

A Comparative Introduction to the Biology and Limnology of the African Great Lakes  

Microsoft Academic Search

The East African rift valley region contains the earth's largest aggregation of tropical lakes. Three of these lakes—Victoria, Tanganyika, and Malawi—hold one quarter of the earth's total surface freshwater supply, and are home to a myriad of fish species. Apart from the diversity and endemicity of their biota, properties that distinguish the African Great Lakes from their North American counterparts

Harvey A. Bootsma; Robert E. Hecky

2003-01-01

81

Stratification of Archaea in the deep sediments of a freshwater meromictic lake: vertical shift from methanogenic to uncultured archaeal lineages.  

PubMed

As for lineages of known methanogens, several lineages of uncultured archaea were recurrently retrieved in freshwater sediments. However, knowledge is missing about how these lineages might be affected and structured according to depth. In the present study, the vertical changes of archaeal communities were characterized in the deep sediment of the freshwater meromictic Lake Pavin. For that purpose, an integrated molecular approach was performed to gain information on the structure, composition, abundance and vertical stratification of archaeal communities thriving in anoxic freshwater sediments along a gradient of sediments encompassing 130 years of sedimentation. Huge changes occurred in the structure and composition of archaeal assemblages along the sediment core. Methanogenic taxa (i.e. Methanosaeta and Methanomicrobiales) were progressively replaced by uncultured archaeal lineages (i.e. Marine Benthic Group-D (MBG-D) and Miscellaneous Crenarchaeal Group (MCG)) which are suspected to be involved in the methane cycle. PMID:22927959

Borrel, Guillaume; Lehours, Anne-Catherine; Crouzet, Olivier; Jézéquel, Didier; Rockne, Karl; Kulczak, Amélie; Duffaud, Emilie; Joblin, Keith; Fonty, Gérard

2012-08-21

82

Stratification of Archaea in the Deep Sediments of a Freshwater Meromictic Lake: Vertical Shift from Methanogenic to Uncultured Archaeal Lineages  

PubMed Central

As for lineages of known methanogens, several lineages of uncultured archaea were recurrently retrieved in freshwater sediments. However, knowledge is missing about how these lineages might be affected and structured according to depth. In the present study, the vertical changes of archaeal communities were characterized in the deep sediment of the freshwater meromictic Lake Pavin. For that purpose, an integrated molecular approach was performed to gain information on the structure, composition, abundance and vertical stratification of archaeal communities thriving in anoxic freshwater sediments along a gradient of sediments encompassing 130 years of sedimentation. Huge changes occurred in the structure and composition of archaeal assemblages along the sediment core. Methanogenic taxa (i.e. Methanosaeta and Methanomicrobiales) were progressively replaced by uncultured archaeal lineages (i.e. Marine Benthic Group-D (MBG-D) and Miscellaneous Crenarchaeal Group (MCG)) which are suspected to be involved in the methane cycle.

Borrel, Guillaume; Lehours, Anne-Catherine; Crouzet, Olivier; Jezequel, Didier; Rockne, Karl; Kulczak, Amelie; Duffaud, Emilie; Joblin, Keith; Fonty, Gerard

2012-01-01

83

Vertical variation of phosphorus forms in surface sediments from Wuli Bay, Taihu Lake, China  

Microsoft Academic Search

In order to investigate the cycling of phosphorus in the Taihu Lake, a sequential extraction technique was used to separate\\u000a different phosphorus forms in surficial sediments from the Wuli Bay of the Taihu Lake. The concentrations of total P are high\\u000a in the sediments, with an average of 2. 80 mg g-1, and a variation range between 4. 02 and

Li Jun; Liu Congqiang; Wang Shilu; Zhu Zhaozhou; Zhou Zhihua; Xiao Huayun

2006-01-01

84

Traditional (?D, ?O-18 ) and non-traditional (Sr-87/Sr-86) isotopes approach to vertical lake profile study  

NASA Astrophysics Data System (ADS)

Isotopic studies (?D, ?O-18, and Sr-87/Sr-86) may contribute to hydrodynamic characterization of lakes, considered as complex systems. Most frequently, researches on lake waters using stable isotopes focus on hydrodynamic studies for the development of hydrological balance. Moreover compared to other types of natural or artificial tracers, isotopes have the advantage of being conservative. Stable isotopes are defined ideal tracers for the characterization of some hydrodynamic parameters of lakes. A comparison of Sr-87/Sr-86 ratio between the aqueous phase (lakewater and groundwater) and the Sr-87/Sr-86 ratio of exchangeable Sr from aquifer material can give detailed information on the hydrochemical processes that contribute solutes to the water. Furthermore, the combination of Sr-87/Sr-86 ratios with information on flow patterns deduced from other isotopes (?D, ?O-18 ) and from geochemical modeling of the cycling of major ions in lakewater and groundwater provides an effective multitracer approach. This can significantly add to our understanding of complex hydrologic systems In addition to determining chemical components and chemical-physical properties (T, pH, electrical conductivity, dissolved oxygen) the study provided the isotopic characterization (?D, ?O-18 e Sr-87/Sr-86) of Lake Albano waters. The vertical profile of dissolved oxygen indicates the existence of the following: ossic epilimnion from surface to the depth of 30 m, a quite large thermocline (metalimnic zone) from 30 to 50 m depth, and anoxic extended hypolimnum from 50 to 100 m depth. The pattern of the value of ?O-18 and ?D with depth leads to the hypothesis that the lake basin is divided into an upper zone (up to 60 m), with a good flow of water, and a lower zone (60 m to 100 m) with a system of stagnant and stratified water, producing different values of ?18O between the layers. ?O-18 data associated with ?D value shows the effect of evaporation on closed basin. The values of Sr-87/Sr-86 isotopic ratio of the lake suggests that there is an interaction of lake water with volcanic products and a contribution of water sedimentary substrate. Sr-87/Sr-86 ratio in combination with, such as ?O-18 and ?D, provide invaluable information about geochemical processes, such as dissolution of aquifer minerals and cation-exchange reactions, flow and mixing patterns in dynamic hydrologic flow systems, and sources of dissolved solutes in groundwater controlling the chemical evolution of groundwater in a volcanic complex.

Battistel, M.; Garone, A.; Barbieri, M.; Parisse, B.

2012-04-01

85

Vertical gradients of PCBs and PBDEs in fish from European high mountain lakes  

NASA Astrophysics Data System (ADS)

A first case of temperature-dependent distribution of polybromodiphenyl eters (PBDEs) in remote areas is shown. Analysis of these compounds in fish from Pyrenean lakes distributed along an altitudinal transect shows higher concentrations at lower temperatures, as predicted in the global distillation model. Conversely, no temperature-dependent distribution is observed in a similar transect in the Tatra mountains (Central Europe) nor in fish from high mountain lakes distributed throughout Europe. The fish concentrations of polychlorobiphenyls (PCBs) examined for comparison showed significant temperature correlations in all these studied lakes. In the interval of feasible temperatures for high mountain lakes, cold trapping of both PCBs and PBDEs concerned the less volatile congeners. In the Pyrenean lake transect the concentrations of PCBs and PBDEs in fish were correlated despite the distinct use of these compounds and their 40 year time-lag of emissions to the environment. Thus, temperature effects have overcome these anthropogenic differences constituting at present the main process determining their distributions. The cases of distinct PBDE and PCB behavior in high mountains can therefore be interpreted to reflect early stages in the environmental distribution of the former compounds.

Grimalt, J. O.; Gallego, E.; Bartrons, M.; Catalan, J.; Camarero, L.; Stuchlik, E.; Battarbee, R.

2006-12-01

86

On the Combined Use of GRACE and Geodetic Observations for Vertical Motion in the Great Lakes Region  

NASA Astrophysics Data System (ADS)

As the measurements from geodetic observations become more accurate, they are implemented to not only empirically derive velocity surfaces but also to infer mantle viscosity. Accurate empirical models for vertical crustal motion are of particular interest in the Great Lakes region, where the line of zero motion (hinge line) is an important constraint for postglacial rebound modelling. With the abundance of geodetic observations in this region, the gradient of the velocity surface can be described relatively well. However, the hinge line can deviate from one data set to another due to datum inconsistencies, different time span and accuracy of measurements, different spatial resolution and presence of erroneous data, as well as the underlying mathematical model. Reliably estimated error bounds of the empirical rates of crustal displacement are required to define the uncertainty with which the mantle viscosity profile can be inferred in the inversion of the empirical rates. In this study, we combine the most recent GRACE-observed rates of gravity change converted to vertical crustal motion, water gauge (and altimetry) data, and GPS velocity data. The combined vertical motion model is realized via a least-squares adjustment procedure, which incorporates variance-component estimation and robust outlier detection. The latter is necessary to ensure reliable estimates of relative errors in the combined least-squares adjustment (via re-scaling of covariance matrices) and to ensure that the final vertical motion model is not distorted by erroneous data. The combined vertical motion model shows a subsidence of -2 mm/yr along the southern shores and uplift of 3 - 4 mm/yr along the northern shores.

Rangelova, E.; Fotopoulos, G.; Sideris, M. G.

2007-12-01

87

Vertical transport of heavy metals by settling particles in Lake Zurich  

Microsoft Academic Search

Transport into sediments of the trace elements Cu, Zn, Pb, Cd, Cr, and Sr by settling particles was investigated in Lake Zurich; the concentrations of these elements in settling particles collected in sediment traps and in the water column were determined at different times of year. Correlations of trace element concentrations with the various main components of the settling particles

LAURA SIGG; MICHAEL STURM; DAVID KISTLER

1987-01-01

88

Vertical Distribution of Nitrogen-Fixing Phylotypes in a Meromictic, Hypersaline Lake  

Microsoft Academic Search

We investigated the diversity of nitrogenase genes in the alkaline, moderately hypersaline Mono Lake, California to determine (1) whether nitrogen-fixing (diazotrophic) populations were similar to those in other aquatic environments and (2) if there was a pattern of distribution of phylotypes that reflected redox conditions, as well as (3) to identify populations that could be important in N dynamics in

G. F. Steward; J. P. Zehr; R. Jellison; J. P. Montoya; J. T. Hollibaugh

2004-01-01

89

Vertical distribution and organic matter production of photosynthetic sulfur bacteria in Japanese lakes  

Microsoft Academic Search

The role of photosynthetic sulfur bacteria as primary producers in stagnant lakes having hydrogen sulfide is described. Photosynthetic bacteria normally appear at the boundary layer of the oxidative and reductive zones, where H& is present and the light intensity is lower than 10% of the surface value. The water of this layer was milky green or pink due to dense

MASAYUKI TAKAHASHI; SHUN-EI ICHIMURA

1968-01-01

90

Composition and transport of settling particles in Lake Zurich: relative importance of vertical and lateral pathways  

Microsoft Academic Search

:   Time- and space-dependent variations in the composition of settling particles were investigated along a longitudinal transect\\u000a in Lower Lake Zurich. The study was carried out during summer stratification using a two-dimensional array of sediment traps\\u000a deployed in the hypolimnion. Samples of the sedimentary material were analysed for total C and total N, P, Ca, Si, Al, Fe,\\u000a Mn, Mg,

Erich Wieland; Peter Lienemann; Silvia Bollhalder; Alfred Lück; Peter H. Santschi

2001-01-01

91

[Speciation and vertical distribution of heavy metals in sediments of Baiyangdian Lake].  

PubMed

In order to find out the heavy metal concentrations and their potential ecological risks on sediments in Baiyangdian Lake, 0-14 cm surface sediments had been collected by the no-disturbance-gravity sampler at seven representative sampling points of Baiyangdian Lake. Optimized BCR sequential extraction procedure was used to carry out the analysis of heavy metal forms in the surface sediments. The heavy metal contents of different forms and in different depths were determined. The relationship between different forms of heavy metal and total organic carbon (TOC) in the sediments was analyzed. The geo-accumulation index (Igeo) was employed to evaluate the extent of heavy metal contamination. The results demonstrated that Co, Fe, Mn, Pb, Zn were mainly in residual form, acid soluble form, Fe-Mn oxide and organic matter bound forms respectively. The tendency of organic bound form of heavy metals and TOC of sediments was greater than the others. The concentration of Co, Pb, Zn decreased with the increase of sediment depth, with the maximal concentration was between 0-2 cm, while the concentration of Mn was the minimal between 6-8 cm and the maximal was at 14 cm. Baiyangdian sediments were not contaminated as a whole by Co, Mn, apart from medium pollution in the entrance of the Fuhe River. The other regions were lightly polluted by Zn and Pb. PMID:23002616

Li, Bi-Cai; He, Lian-Sheng; Yang, Min; Meng, Rui; Yuan, Dong-Hai; Xi, Bei-Dou; Shu, Jian-Min

2012-07-01

92

Mysis Vertical Migration in Grand Traverse Bay, Lake Michigan, Observed by an Acoustic Doppler Current Profiler  

Microsoft Academic Search

The acoustic return signal from Acoustic Doppler Current Profilers (ADCP) moored in Traverse Bay during a 90-day summer period showed a rapid 5-10 dB increase about 1\\/2 hour after sunset and a similar decrease 1\\/2 hour before sunrise. The pattern is characteristic of zooplankton diel vertical migration, most likely Mysis relicta. These are the first reported observations of freshwater invertibrate

Gerald S. Miller

2003-01-01

93

Colour-assortative mating among populations of Tropheus moorii, a cichlid fish from Lake  

Microsoft Academic Search

The species flocks of cichlid fishes in the East African Lakes Tanganyika, Malawi and Victoria are prime examples of adaptive radiation and explosive speciation. Several hundreds of endemic species have evolved in each of the lakes over the past several thousands to a few millions years. Sexual selection via colour- assortative mating has often been proposed as a probable causal

Harald Niederstatter; Anita Brandstatter; Burkhard Berger; Walther Parson; Jos Snoeks; Christian Sturmbauer

94

Tempo and Mode of Diversification of Lake Tanganyika Cichlid Fishes  

Microsoft Academic Search

Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

Julia J. Day; James A. Cotton; Timothy G. Barraclough; Oliver G. Pybus

2008-01-01

95

Vertical distribution of pharmaceuticals in lake sediments-citalopram as potential chemomarker.  

PubMed

The use of pharmaceuticals has increased enormously over the last few decades and serious concerns about their environmental fate and effects have arisen. Thus far, there is little knowledge about the historical pollution of the environment by pharmaceuticals. In the present study, sediment columns from three lake sites adjacent to wastewater treatment plants were collected, further divided in 2- or 2.5-cm slices, and analyzed for 15 pharmaceuticals by liquid chromatography-tandem mass spectrometry. In addition, sediment columns were historically interpreted by analyzing fecal sterols (coprostanol and cholesterol) as well as organic material and organic carbon. Several pharmaceuticals were detected in sediments, the most abundant being citalopram, bisoprolol, and propranolol. At site A, pharmaceuticals prevailed only in the uppermost 15 cm, whereas at site B they existed in the whole sediment column (0-30 cm). Pharmaceuticals were not found in site C sediments. Based on the sterol analyses, municipal wastewater contamination at sites A, B, and C was found in the uppermost 15, 30, and 20 cm, respectively. For the first time, contamination of sediments by pharmaceuticals was demonstrated below the subsurface (up to a depth of 30 cm). When considering the consumption and the observed concentration profiles of pharmaceuticals, a clear increasing trend of citalopram toward the surface was evident at site A. PMID:22639393

Lahti, Marja; Oikari, Aimo

2012-06-29

96

Vertical electrical sounding (VES) and multi-electrode resistivity in environmental impact assessment studies over some selected lakes: a case study  

Microsoft Academic Search

A combined geophysical investigation consisting of vertical electrical sounding (VES) and multielectrode system was carried\\u000a out to map the subsurface resistivity in all major lakes which are highly polluted by the discharge of sewage and other chemical\\u000a effluents in greater Hyderabad, India. The structural features identified in the study area play a major role in groundwater\\u000a flow and storage. The

N. Sundararajan; S. Sankaran; T. K. Al-Hosni

97

Interactive effects of vertical mixing, nutrients and ultraviolet radiation: in situ photosynthetic responses of phytoplankton from high mountain lakes of Southern Europe  

NASA Astrophysics Data System (ADS)

Global change, together with human activities had resulted in increasing amounts of organic material (including nutrients) received by water bodies. This input further attenuates the penetration of solar radiation leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, which effects have in general been neglected. Even more, the combined impacts of mixing, together with those of UVR and nutrients input are virtually unknown. In this study, we carried out in situ experiments in three high mountain lakes of Spain (Lake Enol in Asturias, and lakes Las Yeguas and La Caldera in Granada) to determine the combined effects of these three variables associated to global change on photosynthetic responses of natural phytoplankton communities. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR + PAR (280-700 nm) versus PAR alone (400-700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 ?g P l-1, and N to reach a N : P molar ratio of 31) and, (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m every 4 min, total of 10 cycles) versus static. Our findings suggest that under in situ nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and EOC from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where antagonistic effects were determined, with mixing partially counteracting the negative effects of UVR. Nutrients input mimicking atmospheric pulses from Saharan dust, reversed this effect and clear lakes became more inhibited during mixing, while opaque lakes benefited from the fluctuating irradiance regime. These climate change-related nutrients input and increased mixing would not only affect photosynthesis and production of lakes, but might also further influence the microbial loop and trophic interactions via enhanced EOC under fluctuating UVR exposure.

Helbling, E. W.; Carrillo, P.; Medina-Sanchez, J. M.; Durán, C.; Herrera, G.; Villar-Argaiz, M.; Villafañe, V. E.

2012-07-01

98

Using vertical dikes as a new approach to constraining the size of buried craters: An example from Lake Wanapitei, Canada  

Microsoft Academic Search

Lake Wanapitei, located within the Southern Province of Ontario, Canada, provides the setting for a unique study of an impact crater situated within a shield environment. Evidence for the 7.5-km-diameter Wanapitei impact includes a circular Bouguer gravity low centered over the central area of the lake and features of shock metamorphism in samples of glacial drift found on the southern

E. L'Heureux; H. Ugalde; B. Milkereit; J. Boyce; W. Morris; N. Eyles; N. Artemieva

99

Introductions and extinction of fish in the African great lakes.  

PubMed

The great lakes of Africa contain one of the most remarkable known examples of rapid evolution and speciation of a vertebrate group. The three major lakes - Lake Victoria, Lake Malawi and Lake Tanganyika - each contain a unique radiation of fish belonging to the family Cichlidae. This has produced species 'flocks' that are unique to each lake in species numbers and diversity. At present most of the cichlid species in Lake Victoria are facing extinction as a result of the introduction of an exotic fish species. There are many other examples of introductions or invasions of non-native fish that have had severe effects on the native fish populations and regional economics. These examples should provide a clear warning against the proposed introductions of exotic fish into Lake Malawi. PMID:21227317

Miller, D J

1989-02-01

100

Seasonal variation of nutrients, organic carbon, ATP, and microbial standing crops in a vertical profile of Pyramid Lake, Nevada  

Microsoft Academic Search

Previous studies of Pyramid Lake, Nevada, led to the hypothesis that detritus could be an important food source for zooplankton because abundance of palatable algal species did not seem to be enough to support the zooplankton community throughout the year. Furthermore, a large portion of the annual primary productivity was attributed to a nonpalatable blue-green alga, Nodularia spumigena. We felt

K. Hamilton-Galat; D. L. Galat

1983-01-01

101

The Great Lakes in East Africa: biological conservation considerations for species flocks  

Microsoft Academic Search

The three largest water bodies of East Africa, Lake Victoria, Tanganyika, and Malawi contain an estimated number of 2,000\\u000a endemic cichlid fish species, in addition, to a mostly uncounted wealth of invertebrates. While the terrestrial diversity\\u000a is reasonably well protected, as economic and touristic interests coincide with biological conservation strategies, this is\\u000a not the case for most African lakes and

Christian Sturmbauer

2008-01-01

102

Continental lake level variations from Topex/Poseidon (1993 1996)  

NASA Astrophysics Data System (ADS)

The water level of continental lakes fluctuates due to variations in evaporation and precipitation within their catchment basin in response to regional climatic changes. With satellite altimetry, lake level variations can now he monitored almost continuously with a precision of a few centimeters. In this note, we present water level changes of three American Great Lakes (Superior, Michigan and Huron) and three African lakes (Tanganyika. Malawi and Turkana) based on 4 years (1993-1996) of altimetry data of the Topex/Poseidon (T/P) satellite. The levels of these lakes show a dominant annual cycle highly correlated with precipitations. American Great Lakes are regulated, hence present little interannual variations. This is unlike African lakes which markedly respond to regional (possibly global) climatic changes. A large water level decrease of lakes Tanganyika and Malawi (? 20 cm.yr -1) is observed by T/P for 1993-1996. This trend is associated with recurrent droughts recorded in East and South Africa since the early 1990s, as a result of the series of recent ENSO events.

Ponchaut, Frédérique; Cazenave, Anny

1998-01-01

103

Lacustrine mollusc radiations in the Lake Malawi Basin: experiments in a natural laboratory for evolution  

NASA Astrophysics Data System (ADS)

In terminal Pliocene-early Pleistocene times, part of the Malawi Basin was occupied by paleo-lake Chiwondo. Molluscan biostratigraphy situates this freshwater lake either in the East African wet phase between 2.7-2.4 Ma or that of 2.0-1.8 Ma. In-lake divergent evolution remained restricted to a few molluscan taxa and was very modest. The lacustrine Chiwondo fauna went extinct at the beginning of the Pleistocene. The modern Lake Malawi malacofauna is depauperate and descends from ubiquistic southeast African taxa and some Malawi basin endemics that invaded the present lake after the Late Pleistocene mega-droughts. The Pleistocene aridity crises caused dramatic changes, affecting the malacofauna of all East African lakes. All lacustrine endemic faunas that had evolved in the Pliocene rift lakes, such as paleo-lake Chiwondo, became extinct. In Lake Tanganyika, the freshwater ecosystem did not crash as in other lakes, but the environmental changes were sufficiently important to trigger a vast radiation. All African endemic lacustrine molluscan clades that are the result of in-lake divergence are hence geologically young, including the vast Lavigeria clade in Lake Tanganyika (ca. 43 species).

Van Damme, D.; Gautier, A.

2013-09-01

104

Seasonal and vertical distributions of porewater phosphorus and iron concentrations in a macrophyte-dominated eutrophic lake.  

PubMed

In this study variations in total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) and total iron (TFe) concentrations and pH values in the littoral sediment porewater of macrophyte-dominated eutrophic Mogan Lake (Turkey), were determined depth wise (0-20 cm, on a basis of 5 cm depths) over a period of eleven months. Additionally water temperature, dissolved oxygen, redox potential, TDP, SRP and TFe levels in the overlying water were measured. Especially in the spring and summer months constituting a large portion of the research period, seasonal variation of SRP at depths between 0-5 cm and 15-20 cm were not found to be statistically significant (p > 0.01). However in the fall and winter months, surface sediment (0-5 cm) SRP values were elevated in comparison with deeper sediment depths. As for TFe values, no clearseasonal variation was evident at different depths. Due to the fact that TFe concentrations in the overlying water (101.25-511.67 mg x m(-3)) were lower than iron concentrations in the porewater (104.00-783.00 mg x m(-3)), positive phosphorus release remained at low levels. In this eutrophic lake, in which action is continuing to reduce the external phosphorus load, monitoring SRP variations in the overlying water and porewater would be beneficial. PMID:20143709

Pulatsu, Serap; Topcu, Akasya

2009-09-01

105

A 12,000-year record of vertical deformation across the Yellowstone caldera margin: The shorelines of Yellowstone Lake  

NASA Astrophysics Data System (ADS)

The 600 ka Yellowstone caldera exhibits several signs of unrest, the most evident of which is historic ground deformation including both uplift and subsidence. We document deformation in the area of the southern caldera across approximately 12,000 years using the postglactic shoreline terraces of Yellowstone Lake. Raised shoreline elevations were interpreted from 230 leveling profiles surveyed across flights of terraces, with an accuracy of +/- 0.5 m. Of about 11 recognizable terraces, the five most continuous raised shorelines were correlated around the lake basin to reveal deformation patterns. Net deformation over the past approximatley 3 kyr has been dominantly up within the caldera interior and slightly down along the caldera rim, relative to the extracaldera region. This uplift is roughly similar to the historic pattern and may largely represent the effects of the most recent inflation episode. Subtraction of the total estimated magnitude of inflation in this epsiode suggests that the overall trend of postglacial deformation has been subsidence. The cause of this trend is undetermined but is most likely related to the effects of regional extension and long-term cooling within the Yellowstone caldera.

Locke, William W.; Meyer, Grant A.

1994-10-01

106

Vertical distribution of Archaea and Bacteria in a meromictic lake as determined by fluorescent in situ hybridization.  

PubMed

The prokaryotic cells distribution in the water column of the coastal saline meromictic Lake Faro (Messina, Italy) was investigated by microscopic counting techniques. Water samples were collected at a central station from the surface to the bottom, when waters were characterized by a marked stratification. A "red-water" layer, caused by a dense growth of photosynthetic sulfur bacteria, was present at a depth of 15 m, defining a transition area between oxic (mixolimnion) and anoxic (monimolimnion) layers. Fluorescently labeled 16S rRNA oligonucleotide, group-specific probes were used to determine the abundance of Bacteria and Archaea, and their subgroups, Green Sulfur Bacteria (GSB), Sulfate Reducing Bacteria (SRB), Cyanobacteria and Chromatium okenii, and Crenarchaeota and Euryarchaeota, as key elements of the microbial community. Bacteria decreased from surface to bottom, while Archaea increased with depth and reached the maximum value at 30 m, where they outnumbered the Bacteria. Bacteria and picophytoplankton prevailed in the mixolimnion. At the chemocline high numbers of prokaryotic cells were present, mainly represented by Cyanobacteria, Chromatium okenii and Euryarchaeota. GSB, SRB, and Crenarchaeota prevailed below the chemocline. Although Archaea constitute a minor fraction of microbial community, they could represent active contributors to the meromictic Lake Faro ecosystem. PMID:22006072

Lentini, Valeria; Gugliandolo, Concetta; Maugeri, Teresa L

2011-10-18

107

Vertical distribution of bacteria in a lake sediment from Antarctica by culture-independent and culture-dependent approaches.  

PubMed

Bacterial diversity of the subsurface (18-22 cm), middle (60-64 cm) and bottom (100-104 cm) of a 136-cm-long sediment core sampled from a freshwater lake in Antarctica was determined by the culturable approach, T-RFLP and 16S rRNA gene clone libraries. Using the culturable approach, 41 strains were isolated and, based on phylogenetic analysis, they could be categorized into 14 groups. Representatives of the 14 groups varied in their growth temperature range (4-30 °C), in their tolerance to NaCl (0-2 M NaCl) and in the growth pH range (5-11). Eleven of fourteen representative strains exhibited either amylase, lipase, protease and (or) urease activities at 4 °C. Bacterial diversity at the phyla level using T-RFLP and 16S rRNA clone libraries was similar and clones were affiliated with Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. TRFs affiliated with Spirochaetes were detected only by the T-RFLP approach and clones affiliated with Caldiserica only in the clone libraries. Stratification of bacteria along the depth of the sediment was observed both with the T-RFLP and the 16S rRNA gene clone library methods, and results indicated that stratification was dependent on the nature of the organism, aerobic or anaerobic. For instance, aerobic Janthinobacterium and Polaromonas were confined to the surface of the sediment, whereas anaerobic Caldisericum was present only in the bottom portion of the core. It may be concluded that the bacterial diversity of an Antarctic lake sediment core sample varies throughout the length of the core depending on the oxic-anoxic conditions of the sediment. Furthermore, these psychrophilic bacteria, due to their ability to produce extracellular cold active enzymes, might play a key role in the transformation of complex organic compounds. PMID:21126578

Shivaji, Sisinthy; Kumari, Kiran; Kishore, Kankipati Hara; Pindi, Pavan Kumar; Rao, Pasupuleti Sreenivasa; Radha Srinivas, Tanuku Naga; Asthana, Rajesh; Ravindra, Rasik

2010-11-30

108

Use of acoustic backscatter and vertical velocity to estimate concentration and dynamics of suspended solids in Upper Klamath Lake, south-central Oregon: Implications for Aphanizomenon flos-aquae  

USGS Publications Warehouse

Vertical velocity and acoustic backscatter measurements by acoustic Doppler current profilers were used to determine seasonal, subseasonal (days to weeks), and diel variation in suspended solids in a freshwater lake where massive cyanobacterial blooms occur annually. During the growing season, the suspended material in the lake is dominated by the buoyancy-regulating cyanobacteria, Aphanizomenon flos-aquae. Measured variables (water velocity, relative backscatter [RB], wind speed, and air and water temperatures) were averaged over the deployment season at each sample time of day to determine average diel cycles. Phase shifts between diel cycles in RB and diel cycles in wind speed, vertical water temperature differences (delta T(degree)), and horizontal current speeds were found by determining the lead or lag that maximized the linear correlation between the respective diel cycles. Diel cycles in RB were more in phase with delta T(degree) cycles, and, to a lesser extent, wind cycles, than to water current cycles but were out of phase with the cycle that would be expected if the vertical movement of buoyant cyanobacteria colonies was controlled primarily by light. Clear evidence of a diel cycle in vertical velocity was found only at the two deepest sites in the lake. Cycles of vertical velocity, where present, were out of phase with expected vertical motion of cyanobacterial colonies based on the theoretical cycle for light-driven vertical movement. This suggests that water column stability and turbulence were more important factors in controlling vertical distribution of colonies than light. Variations at subseasonal time scales were determined by filtering data to pass periods between 1.2 and 15 days. At subseasonal time scales, correlations between RB and currents or air temperature were consistent with increased concentration of cyanobacterial colonies near the surface when water column stability increased (higher air temperatures or weaker currents) and dispersal of colonies throughout the water column when the water column mixed more easily. RB was used to estimate suspended solids concentrations (SSC). Correlations of depth-integrated SSC with currents or air temperatures suggest that depth-integrated water column mass decreased under conditions of greater water column stability and weaker currents. Results suggest that the use of measured vertical velocity and acoustic backscatter as a surrogate for suspended material has the potential to contribute significant additional insight into dynamics of Aphanizomenon flos-aquae colonies in Upper Klamath Lake, south-central Oregon.

Wood, Tamara M.; Gartner, Jeffrey W.

2010-01-01

109

Vertical and temporal distribution of nitrogen and phosphorus and relationship with their influencing factors in aquatic-terrestrial ecotone: a case study in Taihu Lake, China.  

PubMed

Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone (ATE) of Taihu Lake were investigated, and the relations among N, P, ORP (oxidation reduction potential), TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3- -N, DON (dissolved organic nitrogen) and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4+ -N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3- -N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3- -N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation of TN, TP, NO3- -N, NH4+ -N and DON is significant, of which the variation coefficient of NO3- -N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment. PMID:17969641

Yang, Hong-jun; Shen, Zhe-min; Zhu, Song-he; ang, Wen-hua

2007-01-01

110

Lateral and Vertical Channel Movement and Potential for Bed-Material Movement on the Madison River Downstream from Earthquake Lake, Montana.  

National Technical Information Service (NTIS)

The 1959 Hebgen Lake earthquake caused a massive landslide (Madison Slide) that dammed the Madison River and formed Earthquake Lake. The U.S. Army Corps of Engineers excavated a spillway through the Madison Slide to permit outflow from Earthquake Lake. In...

K. J. Chase P. M. McCarthy

2012-01-01

111

Silica dynamics in a pampean lake (Lake Chascomús, Argentina)  

Microsoft Academic Search

Silica dynamics in a pampean lake, Lake Chascomús (Chaco-Pampa plain, Argentina) is described. Pampean lakes are shallow alkaline ecosystems, with circulation pattern corresponding to polymictic lakes, due to the nearly continuous vertical mixing that promotes a high concentration of suspended particulate matter and low transparency. A silica budget was calculated in Lake Chascomús in 1999–2000 using a one-box model that

Patricia Miretzky; Alicia Fernández Cirelli

2004-01-01

112

Water quality of Lake Austin and Town Lake, Austin, Texas  

SciTech Connect

Lake Austin and Town Lake are impoundments on the Colorado River in Travis County, central Texas, and are a source of water for municipal industrial water supplies, electrical-power generation, and recreation for more than 500,000 people in the Austin metropolitan area. Small vertical temperature variations in both lakes were attributed to shallow depths in the lakes and short retention times of water in the lakes during the summer months. The largest areal variations in dissolved oxygen generally occur in Lake Austin during the summer as a result of releases of water from below the thermocline in Lake Travis. Except for iron, manganese, and mercury, dissolved concentrations of trace elements in water collected from Lake Austin and Town Lake did not exceed the primary or secondary drinking water standards set by the US Environmental Protection Agency. Little or no effect of stormwater runoff on temperature, dissolved oxygen, or minor elements could be detected in either Lake Austin or Town Lake. Little seasonal or areal variation was noted in nitrogen concentrations in Lake Austin or Town lake. Total phosphorus concentrations generally were small in both lakes. Increased concentrations of nitrogen and phosphorus were detected after storm runoff inflow in Town Lake, but not in Lake Austin; densities of fecal-coliform bacteria increased in Lake Austin and Town Lake, but were substantially greater in Town Lake than in Lake Austin. 18 refs., 38 figs., 59 tabs.

Andrews, F.L.; Wells, F.C.; Shelby, W.J.; McPherson, E.M.

1988-01-01

113

Assessing high resolution oxidation-reduction potential and soluble reactive phosphorus variation across vertical sediments and water layers in Xinghu Lake: A novel laboratory approach  

Microsoft Academic Search

To understand the transfer process of soluble reactive phosphorus (SRP) on the lake sediment-water interface in a mesotrophic shallow lake in South China, the SRP concentrations and the oxidation-reduction potential (ORP) across the sediment-water interfaces were continually monitored. Sediment samples were collected from Xinghu Lake in Guangdong Province. The ORP dynamics at different layers of overlying water was similar for

Yingzhi Li; Beicheng Xia; Jiaying Zhang; Chuanhong Li; Wenzhuan Zhu

2010-01-01

114

High-frequency internal waves in large stratified lakes  

Microsoft Academic Search

Observations are presented from Lake Biwa and Lake Kinneret showing the ubiquitous and often periodic nature of high-frequency internal waves in large stratified lakes. In both lakes, high-frequency wave events were observed within two distinct categories: (1) Vertical mode 1 solitary waves near a steepened Kelvin wave front and vertical mode 2 solitary waves at the head of an intrusive

L. Boegman; J. Imberger; G. N. Ivey; J. P. Antenucci

2003-01-01

115

The Role of Flow Velocity in the Vertical Distribution of Particulate Organic Matter on Moss-covered Travertine Barriers of the Plitvice Lakes (Croatia)  

Microsoft Academic Search

We investigated the distribution patterns of particulate organic matter (POM) on travertine barriers in respect to flow velocity.\\u000a Research was conducted on the barrage-lake system of the Plitvice Lakes, Croatia. Four layers were distinguished within the\\u000a substrate (moss mat + three travertine layers) in three hydraulic habitats at three sites. Substrate samples were collected\\u000a monthly with a core sampler. The aim of

Marko Miliša; Ivan Habdija; Biserka Primc-Habdija; Ines Radanovi?; Renata Matoni?kin Kep?ija

2006-01-01

116

The influence of water quality and sediment geochemistry on the horizontal and vertical distribution of phosphorus and nitrogen in sediments of a large, shallow lake  

Microsoft Academic Search

Distinct horizontal water column concentration gradients of nutrients and chlorophyll a (Chl a) occur within large, shallow, eutrophic Lake Taihu, China. Concentrations are high in the north, where some of the major\\u000a polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. It is not\\u000a clear, however, whether these water column concentration gradients are

Dennis Trolle; Guangwei Zhu; David Hamilton; Liancong Luo; Chris McBride; Lu Zhang

2009-01-01

117

Water-surface chlorophyll detection by remote sensing and vertical structure of chlorophyll analysis in Lake Superior: Water-surface chlorophyll as an estimate of water-column-integrated chlorophyll  

NASA Astrophysics Data System (ADS)

This research, consisting of three parts, investigates the application of remote sensing to both the detection of water-surface chlorophyll a concentration ([Chl-a]) and the estimation of water-column-integrated [Chl-a] in Lake Superior. In Chapter 1, we describe four methods for determining remote sensing reflectance ( Rrs), using a combination of above-surface, below-surface, and polarization measurements of radiance, in western Lake Superior during the summer of 2003. The work allows us to examine in detail the effects of the unwanted surface reflectance from a rough water surface. The results of Chapter 1 provide consistent values of Rrs and indicate that the four methods are practical and helpful in determining Rrs reliably. In Chapter 2, we evaluate two standard empirical [Chl-a] retrieval algorithms: one for Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and one for Moderate Resolution Imaging Spectroradiometer (MODIS). We compare the results from satellite data with the corresponding in-situ data collected in western Lake Superior in the summer of 2004. The linear correlations between the empirically-derived [Chl-a] and the in-situ measurements are poor (R2 around 0.1) for both algorithms. We find that more detailed information on particulate backscattering is required to test and derive a regionally optimized semi-analytical algorithm. To overcome the problems associated with retrieving water-surface [Chl-a] from the empirical and the semi-analytical algorithms, we apply artificial neural networks (ANNs). The results appear to provide better estimates of [Chl-a] than the empirical algorithms. In Chapter 3, we discuss the difference between the [Chl- a] profiles collected in offshore and inshore areas of western and southeastern Lake Superior and explore the possibility of applying a Gaussian distribution to the modeling for the offshore [Chl-a] profiles. We establish statistical relationships between the water-surface [Chl- a] and its vertical distribution characteristics: the deep chlorophyll maximum (DCM), the DCM depth (zmax), and the depth-integrated [Chl-a]. ANNs are used to relate the [Chl-a], the temperature, and the vertical attenuation coefficient (K d) near water surface to the depth-integrated [Chl- a]. Using these two kinds of inverse models, we determine the depth-integrated [Chl-a] distribution for western Lake Superior.

Yan, Yuhu

118

Reproductive biology of Eretmodus cyanostictus , a cichlid fish from Lake Tanganyika  

Microsoft Academic Search

One of the most widely accepted explanations for monogamy is the need for biparental care. However, the occurrence of monogamy combined with biparental care is extremely rare in oral incubating (mouthbrooding) cichlid fishes. Few studies have been performed on cichlid species that exhibit this behaviour, and therefore the ecological factors that favour monogamy in these cases remain obscure. Here we

Josephine Isabelle Morley; Sigal Balshine

2003-01-01

119

Discovery of sublacustrine hydrothermal activity and associated massive sulfides and hydrocarbons in the north Tanganyika trough, East African Rift  

SciTech Connect

Massive sulfides and carbonate mineral deposits associated with sublacustrine thermal springs were recently discovered along the Zaire side of the north Tanganyika trough, western branch of the East African Rift. This hydrothermal activity, investigated by scuba diving at a maximum depth of 20 m, is located at the intersection of major north-south normal faults and northwest-southeast faults belonging to the Tanganyika-Rukwa-Malawi (TRM) strike-slip fault zone. The preliminary results presented here come from analyses of sulfide deposits, hydrothermal fluids, and associated hydrocarbons that result from geothermal activity in this part of the East African Rift filled by a thick pile of sediment, the north Tanganyika trough.

Tiercelin, J.J.; Mondeguer, A. (Universite de Bretagne Occidentale, Brest (France)); Thouin, C. (Centre Universitaire Regional de Toliara (Madagascar)); Kalala, T. (Centre de Recherche en Sciences Naturelles, Sud-Kivu (Zaire))

1989-11-01

120

Circulation and mixing of lake water  

NASA Astrophysics Data System (ADS)

The results of the research on the circulation and the mixing of lake water were organized, and the perspective of the research was considered. The flow of lake water is divided into a horizontal flow and a vertical flow. A horizontal flow is chiefly caused by the wind shear stress. As for the research of the flow caused by the wind shear stress, a field observation, a model flume experiment, and a numerical experiment have been conducted. They provided a remarkable advancement from the 1970s to the 1980s. Hereafter, using a new technology such as GPS will be hoped in the flow observation. A vertical circulation is caused by the density difference of water due to the cooling on the lake surface and the wind shear stress. A vertical circulation causes the mixing of lake water. The mixing of lake water is investigated by observing the water quality distribution, especially there are a lot of researches that consider a vertical mixing making use of the profiles of the dissolved oxygen. In a tropical lake, there is a close relationship between the mixing of lake water and the heat balance on the lake surface, then the depth of vertical mixing is estimated by the amount of cooling on the lake surface. Therefore, it is considered that the clarification of the lake water mixing on a tropical lake contributes to the information about the global warming phenomenon. Moreover, some natural lakes are expected as a monitor of acid precipitation and the micro pollutant.

Sato, Yoshinori

121

Installation of a vertical slurry wall around an Italian quarry lake: complications arising and simulation of the effects on groundwater flow  

Microsoft Academic Search

Slurry walls are non-structural barriers that are constructed underground to impede groundwater flow or manage groundwater\\u000a control problems. The study area is in the Piemonte plain (Italy), close to the River Po. Quarrying works carried out below\\u000a the piezometric surface created two big quarry lakes. The local groundwater system is characterized by a lower semi-confined\\u000a aquifer, which is overlain by

D. A. De Luca; M. Lasagna; A. Morelli di Popolo e Ticineto

2007-01-01

122

ARE LAKES GETTING WARMER? REMOTE SENSING OF LARGE LAKE TEMPERATURES  

EPA Science Inventory

Recent studies (Levitus et al., 2000) suggest a warning of the world ocean over the past 50 years. Freshwater lakes could also be getting warmer but thermal measurements to determine this are lacking. Large lake temperatures are vertically and horizontally heterogeneous and vary ...

123

Long-term lake water temperature and ice cover simulations\\/measurements  

Microsoft Academic Search

The one-dimensional, numerical simulation model for vertical water temperature profiles in cold climate freshwater lakes developed by Gu and Stefan was modified and applied to two small lakes in the north-central US. Modifications include a new expression for vertical thermal diffusion coefficients derived from a detailed field study in a third lake, heat exchange with lake sediment for all layers

Xing Fang; Heinz G. Stefan

124

Lake Malawi sediment and pore water chemistry: Proposition of a conceptual model for stratification intensification since the end of the Little Ice Age  

NASA Astrophysics Data System (ADS)

Sedimentary records of salinity indicators are largely used to reconstruct past climatic changes in lacustrine systems where chemistry is sensitive to hydroclimatic conditions. In large fresh lakes of the East African Rift such as Lakes Tanganyika and Malawi, salinity is often considered constant and other paleoclimatological proxy data are used. However, a relation between lake surface chloride concentration and hydroclimatic regime was previously demonstrated at the century scale in Lake Tanganyika. This relation is transposed to Lake Malawi on the base of similarity between hydrochemical budgets of both lakes that are computed for the whole lake and epilimnion. Whereas numerous physico-chemical difficulties make generally debatable use of lake pore water chemistry, as illustrated here by diffusion modelling, the dissolved chloride concentration profile from a core sampled in northern Lake Malawi is considered as a potential indicator of limnological-hydroclimatic condition changes for the last 200 years. A decrease in pore water chloride concentration between 1840 AD and present situation is directly associated to a metalimnetic water salinity decrease. The chronology of this event is synchronous with diatom productivity change demonstrated by Johnson et al. (2001) at the end of the Little Ice Age (LIA). A conceptual model of Lake Malawi, based on salinity, organic carbon and its "dead" watershed contribution, lake-level and productivity changes since the mid 19th century is presented. A new scenario is proposed, based on thermal stratification reinforcement at the end of the LIA. Lake productivity and chemistry depend on stratification strength, water column mixing rate and on climatic variability. During the LIA, nutrient distribution profiles were more homogeneous with depth due to the climatically (colder and drier climatic conditions than today) induced destabilisation of the mixing barrier. The productive system is then auto-supplied and does not require external silicon supply while chloride concentration is higher due to closure of the basin. Stratification has become more stable since the end of the LIA, as in nearby Lake Tanganyika where it is linked to air temperature global increase. Results demonstrated that chloride is a suitable indicator of the present and past hydroclimatic and hydrodynamic regimes. This work shows that in Lake Malawi, assessment of "dead" carbon (or old "refractive watershed carbon") contribution to the TOC is a key parameter to set chronological frame from 14C ages.

Branchu, Philippe; Bergonzini, Laurent; Pons-branchu, Edwige; Violier, Eric; Dittrich, Maria; Massault, Marc; Ghaleb, Bassam

2010-07-01

125

LAKE-WIDE SEASONAL CHANGES IN LIMNOLOGICAL CONDITIONS IN LAKE MICHIGAN IN 1976  

EPA Science Inventory

Data collected on lake-wide cruises in 1976 were used to study seasonal and vertical variations in water temperature, transparency, chlorophyll a, and nutrients in Lake Michigan. Data were analyzed according to subsets corresponding to the northern and southern open lake. Compari...

126

Understanding the performance of the FLake model over the African Great Lakes  

NASA Astrophysics Data System (ADS)

The ability of the one-dimensional lake model FLake to represent the mixolimnion temperatures for tropical conditions was tested for three locations in East Africa: Lake Kivu, Lake Tanganyika's northern and southern basins. Meteorological observations from surrounding Automatic Weather Stations were corrected and used to drive FLake, whereas a comprehensive set of water temperature profiles served to evaluate the model at each site. Careful forcing data correction and model configuration allowed to reproduce the observed mixed layer seasonality at Lake Kivu and Lake Tanganyika (northern and southern basins), with correct representation of both the mixed layer depth and temperature structure. At Lake Kivu, mixolimnion temperatures predicted by FLake were found sensitive both to minimal variations in the external parameters (lake depth and water transparency) as to small changes in the meteorological driving data, in particular wind velocity. In each case, small modifications may already lead to a regime switch from the correctly represented seasonal mixed layer deepening to either completely mixed (down to the model lake bottom) or permanently stratified (from ~10 m downwards) conditions. In contrast, model temperatures are found robust close to the surface, with acceptable predictions of near-surface water temperatures even when the seasonal mixing regime is not reproduced. FLake can thus be a suitable tool to parameterize tropical lake water surface temperatures within atmospheric prediction models, but may be less appropriate, in its current form, to study complex limnological processes within tropical lakes. Furthermore, a study of different initial conditions showed that for tropical lakes lacking reliable initial data, a fully mixed, artificially warm initialisation is to be preferred, but only if the model is allowed to spin up until convergence is reached. Finally, FLake was used to attribute the seasonal mixing cycle at Lake Kivu to variations in the near-surface meteorological conditions. It was found that the annual mixing down to 60 m during the main dry season is primarily due to enhanced lake evaporation and secondarily due to the decreased incoming long wave radiation, both causing a significant heat loss from the lake surface and associated mixolimnion cooling.

Thiery, W.; Martynov, A.; Darchambeau, F.; Descy, J.-P.; Plisnier, P.-D.; Sushama, L.; van Lipzig, N. P. M.

2013-10-01

127

Vertical Separation  

Microsoft Academic Search

A simple duopoly model is used to show the advantage to a manufacturer of se lling his product through an independent retailer (vertical separatio n) rather than directly to consumers (vertical integration). Vertical separation is profitable insofar as it induces more friendly behavio r from the rival manufacturer. The authors consider the case where fr anchise fees can be used

Giacomo Bonanno; John Vickers

1988-01-01

128

Enhanced mixing in narrows: A case study at the Mainau sill (Lake Constance)  

Microsoft Academic Search

Previous work has identified bottom currents as a significant source of turbulence in stratified lakes. Sills may therefore be a major factor determining overall turbulent diapycnal (vertical) exchange in lakes with multi-basin hypolimnia.¶In order to investigate the contribution of the Mainau sill (separating Upper Lake Constance from Lake Überlingen) to the overall diapycnal mixing in Lake Constance, a series of

Otti Kocsis; Bruno Mathis; Manuel Gloor; Michael Schurter; Alfred Wüest

1998-01-01

129

HIGH RESOLUTION MODELLING OF PCB CONGENERS IN LAKE MICHIGAN USING THE LAKE MICHIGAN (LM3) CONTAMINANT MODEL  

EPA Science Inventory

The Lake Michigan Level 3 (LM3) Model is a numerical model of Lake Michigan used to predict the fate and transport of 54 PCB congeners. The LM3 model segments Lake Michigan horizontally with a 5 x 5 km grid and vertically with 19 sigma layers for a total of 44,042 water column se...

130

Paleoevaporation and Paleoprecipitation in the Tanganyika Basin at 18,000 Years B.P. Inferred from Hydrologic and Vegetation Proxies  

Microsoft Academic Search

Paleo-hydrologic and -vegetation proxy data from the Tanganyika basin are integrated in energy and water balance equations to infer past evaporation and precipitation during the last glacial maximum (LGM). Our approach is first validated on the modern system. Large variations are assigned to input variables to simulate the interannual precipitation variability. Equations are then applied to the LGM. We first

Laurent Bergonzini; Francoise Chalié; Francoise Gasse

1997-01-01

131

CONNECTICUT LAKES  

EPA Science Inventory

This is a 1:24,000-scale datalayer of named lakes in Connecticut. It is a polygon Shapefile that includes all lakes that are named on the U.S. Geologicial Survey (USGS) 7½ minute topographic quadrangle maps that cover the State of Connecticut, plus other officially named lakes i...

132

Repeated Parallel Evolution of Parental Care Strategies within Xenotilapia, a Genus of Cichlid Fishes from Lake Tanganyika  

Microsoft Academic Search

The factors promoting the evolution of parental care strategies have been extensively studied in experiment and theory. However, most attempts to examine parental care in an evolutionary context have evaluated broad taxonomic categories. The explosive and recent diversifications of East African cichlid fishes offer exceptional opportunities to study the evolution of various life history traits based on species-level phylogenies. The

Michael R. Kidd; Nina Duftner; Stephan Koblmüller; Christian Sturmbauer; Hans A. Hofmann

2012-01-01

133

CALCULATED CONTRIBUTION OF SURFACE MICROLAYER PCB TO CONTAMINATION OF LAKE MICHIGAN LAKE TROUT  

EPA Science Inventory

The possible significance of PCB concentration in the surface microlayer of Lake Michigan to contamination of lake trout was examined using a modification of a previously developed food chain model. Vertically migrating zooplankton were assumed to spend a fraction of each day exp...

134

Observed and predicted Great Lakes winter circulations  

SciTech Connect

Observed mean winter currents in Lakes Ontario and Huron are compared to predictions from a homogeneous, vertically integrated, steady-state model. If specific wind directions are selected to drive this model, the observed and predicted current patterns agree. The specific wind directions were chosen to maximize each lake's wind response. The agreement suggests that there is a mean wind-driven winter circulation in the Great Lakes, and that its pattern depends upon these specific wind directions. Based on these factors, winter circulations for Lakes Erie, Huron and Superior are predicted.

Pickett, R.L.

1980-07-01

135

Vertical mammaplasty.  

PubMed

Current criticisms regarding vertical mammaplasty include problems with poor immediate postoperative appearance, nipple-areola complex malposition, and excessive lower pole length. These problems can be avoided by proper patient selection, by utilizing correct concepts of skin design, and by observing correct glandular resection and closure concepts. Vertical mammaplasty also can result in other problems, such as hypertrophic circumareolar scars and lower pole deformities, including notching, boxy shape, infra-areolar depression, and flatness. These problems are also largely avoidable by using correct technique. Several basic concepts described previously have not proven necessary to achieve good results. Abandoning some of these principles has contributed to the ability to establish an aesthetically ideal breast shape intraoperatively as well as to a decrease in morbidity. This includes eliminating liposuction as a major integral component of the procedure, eliminating suturing the gland to the pectoralis muscle, not undermining the lower pole skin, and avoiding overly wide skin resection and tight wound closure that produces significant lower pole distortion in the early postoperative period. An important concept that has proven reliable is to use a "closed" design that does not predetermine the areolar opening whenever circumstances permit. When this is not possible, a modification that utilizes the smallest possible circumference as an open design is better than a large "mosque." These alternatives allow greater flexibility in determining final nipple position and also reduce the risk of hypertrophic circumareolar scars. Important glandular resection concepts include creating pillars that are attached to both the skin and the chest wall; making them of adequate dimension to avoid postoperative lower pole shape problems, such as flattening; resecting closer to the skin lateral to the pillars to avoid a boxy breast shape; and using a drain both to assist in accurately determining the endpoint of resection and to avoid postoperative seromas. Key closure concepts include approximation of the superior surfaces of the pillars at their base to maintain vertical height and thereby prevent lower pole flattening; approximation of the inferior surfaces of the pillars to the base of the breast to prevent notching; and proper management of the vertical incision by restricting the purse-string suture effect to only the inferior portion of the incision, where there may be skin excess present. Inclusion of these concepts leads to predictable and improved aesthetic results in vertical mammaplasty. This allows full realization of the purported advantages of vertical mammaplasty and allows this method to be utilized with a level of confidence similar to that seen with inverted-T techniques. PMID:15793463

Hidalgo, David A

2005-04-01

136

Offline test of the CLM4-VRLS lake model at Lake Taihu  

NASA Astrophysics Data System (ADS)

Lakes are an important surface type for atmospheric research. With the deployment of Taihu Eddy Flux Mesonet since 2010, Lake Taihu, a large shallow lake located in eastern China (~2500 km2 and 2 m deep), provides a unique testbed for models of lake-atmosphere interactions. In this study, we evaluated CLM4-VRLS, a state-of-the-art lake model developed by NCAR, against the observations made at Lake Taihu. CLM4-VRLS is an improved version of the earlier NCAR CLM4 lake model, and includes realistic representations of roughness length, vertical mixing and sediment layer. So far evaluation of the performance of CLM4-VRLS and other models of lake-atmosphere interactions has been restricted mostly to annual cycles of water temperature. In shallow lakes such as Lake Taihu, lake temperature also experiences strong diurnal variations, and it is not known if the model can adequately predict these variations. Furthermore, we are not aware of any studies that evaluate model-predicted surface fluxes of heat, water vapor and momentum against field observations. Accurate prediction of these fluxes is important for a number of reasons, one of which is that these fluxes serve as the lower boundary conditions for models of regional climate and weather prediction. Evaluating CLM4-VRLS at Lake Taihu provides novel insights on its performance, and lays the groundwork for our future study of the feedback between regional climate and Lake Taihu. Results show that CLM4-VRLS yields good estimations of the seasonal variations of the lake surface temperature (LST) at Lake Taihu. However, in terms of the diurnal variations of LST, which are important for the boundary layer processes, CLM4-VRLS does not perform well without the adoption of lake-specific parameters. Compared with the default values in CLM4-VRLS, Lake Taihu is characterized by smaller roughness lengths for heat and water vapor, and larger light extinction coefficient due to high turbidity. In addition, the eddy diffusivity was found to be two orders smaller than that of CLM4-VRLS. Adopting these lake-specific parameters can improve the performance of CLM4-VRLS, notably for the amplitude of the diurnal variations of LST. During nighttime when the lake water is vertically unstable and the passage of cold fronts, CLM4-VRLS with the lake-specific parameters tends to overestimate the LST. We suspect that the nighttime overestimation is attributed to the fact that instability enhances vertical mixing to a lesser extent than that predicted by CLM4-VRLS, while the overestimation during a front scenario is due to synoptic advection.

Deng, B.; Lee, X.; Xiao, W.; Liu, S.; Shen, S.

2011-12-01

137

Primary and Bacterial Production in Two Dimictic Indiana Lakes  

PubMed Central

The relationship between primary and bacterial production in two dimictic Indiana lakes with different primary productivities was examined during the summer stratification period in 1982. Primary production rates were calculated from rates of H14CO3? incorporation by natural samples, and bacterial production was calculated from rates of [3H-methyl]thymidine incorporation by natural samples. Both vertical and seasonal distributions of bacterial production in the more productive lake (Little Crooked Lake) were strongly influenced by primary production. A lag of about 2 weeks between a burst in primary production and the subsequent response in bacterial production was observed. The vertical distribution of bacterial production in the water column of the less productive lake (Crooked Lake) was determined by the vertical distribution of primary production, but no clear relationship between seasonal maxima of primary and bacterial production in this lake was observed. High rates of bacterial production in Crooked Lake during May indicate the importance of allochthonous carbon washed in by spring rains. Bacterial production accounted for 30.6 and 31.8% of total (primary plus bacterial) production in Crooked Lake and Little Crooked Lake, respectively, from April through October. High rates of bacterial production during late September and October were observed in both lakes. Calculation of the fraction of bacterial production supported by phytoplankton excretion implies an important role for other mechanisms of supplying carbon, such as phytoplankton autolysis. Several factors affecting the calculation of bacterial production from the thymidine incorporation rates in these lakes were examined.

Lovell, Charles R.; Konopka, Allan

1985-01-01

138

LAKE FORK  

EPA Science Inventory

The Lake Fork of the Arkansas River Watershed has been adversely affected through mining, water diversion and storage projects, grazing, logging, and other human influences over the past 120 years. It is the goals of the LFWWG to improve the health of Lake fork by addressing th...

139

Mormon Lake.  

National Technical Information Service (NTIS)

It is recommended that Mormon Lake be established as a scenic and recreation natural area. The area has a long history of disturbance and is heavily used by humans at present. The area is dominated by intermittant Mormon Lake itself and typical Transition...

E. L. Smith G. L. Bender

1973-01-01

140

Changes in peasant food production and food supply in relation to the historical development of commodity production in pre?colonial and colonial Tanganyika  

Microsoft Academic Search

This paper explores the dynamic interaction between peasant food production and commodity production under conditions of the increasing penetration of capital and consequent erosion of pre?capitalist modes of production in pre?colonial and colonial Tanganyika (Tanzania). It is argued that while the law of value inherent in commodity production definitely served to effect more specialisation of labour in peasant production, nevertheless,it

Deborah Fahy Bryceson

1980-01-01

141

Characterization of Lake Michigan coastal lakes using zooplankton assemblages  

USGS Publications Warehouse

Zooplankton assemblages and water quality were examined bi-weekly from 17 April to 19 October 1998 in 11 northeastern Lake Michigan coastal lakes of similar origin but varied in trophic status and limnological condition. All lakes were within or adjacent to Sleeping Bear Dunes National Lakeshore, Michigan. Zooplankton (principally microcrustaceans and rotifers) from triplicate Wisconsin net (80 I?m) vertical tows taken at each lake's deepest location were analyzed. Oxygen-temperature-pH-specific conductivity profiles and surface water quality were concurrently measured. Bray-Curtis similarity analysis showed small variations among sample replicates but large temporal differences. The potential use of zooplankton communities for environmental lake comparisons was evaluated by means of BIOENV (Primer 5.1) and principal component analyses. Zooplankton analyzed at the lowest identified taxonomic level yielded greatest sensitivity to limnological variation. Taxonomic and ecological aggregations of zooplankton data performed comparably, but less well than the finest taxonomic analysis. Secchi depth, chlorophyll a, and sulfate concentrations combined to give the best correlation with patterns of variation in the zooplankton data set. Principal component analysis of these variables revealed trophic status as the most influential major limnological gradient among the study lakes. Overall, zooplankton abundance was an excellent indicator of variation in trophic status.

Whitman, Richard L.; Nevers, Meredith B.; Goodrich, Maria L.; Murphy, Paul C.; Davis, Bruce M.

2004-01-01

142

Potential Effects of Climate Warming on Fish Habitats in Temperate Zone Lakes with Special Reference to Lake 239 of the Experimental Lakes Area (ELA), North-Western Ontario  

Microsoft Academic Search

We used simple statistics (e.g. mean temperature, degree days, cumulative volume days) to describe present thermal habitats for cool water (yellow perch, Perca flavescens) and cold water (lake trout, Salvelinus namaycush) fish of a small boreal lake. We then modelled changes in the vertical and temporal extent of these habitats under various scenarios of climatic change that included increases in

Wolfgang Jansen; Raymond H. Hesslein

2004-01-01

143

Lake Pillsbury, Lake County, California.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origion. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected b...

1978-01-01

144

Simulating the thermal dynamics of Lake Kinneret  

Microsoft Academic Search

In this study, we use the one-dimensional hydrodynamic model DYRESM to simulate the Lake Kinneret thermal structure over a period of 45 months. We focus on the application of a new version of the one-dimensional hydrodynamic model to Lake Kinneret and simulation of the physical processes. DYRESM is calibration-free process-based model that simulates the vertical distribution of temperature and salinity

Gideon Gal; Jorg Imberger; Tamar Zohary; Jason Antenucci; Ayal Anis; Tzahi Rosenberg

2003-01-01

145

Barotropic Oscillations in Lake Onega: A Lake of Complex Geometry  

Microsoft Academic Search

\\u000a The most simple model of a lake is a quadrilateral basin, i.e. a rectangular basin with constant depth and vertical walls\\u000a along its four sides. Analysis of the barotropic or baroclinic linear shallow water equations without rotation revealed that\\u000a the free oscillations occur in ordered modes. This will mean that the eigenperiods of these modes can be sequentially numbered\\u000a according

Kolumban Hutter; Yongqi Wang; Irina P. Chubarenko

146

Microbial communities of the stratified soda Lake Doroninskoe (Transbaikal region)  

Microsoft Academic Search

The physicochemical properties, species composition, and vertical distribution of microorganisms in the water column, shoreline\\u000a microbial mat, and small shoreline mud volcanoes of the stratified soda Lake Doroninskoe were investigated in September 2007.\\u000a The lake is located in the Transbaikal region, in the permafrost zone (51°25?N; 112°28?E). The maximal depth of the contemporary\\u000a lake is about 6 m, the pH

V. M. Gorlenko; S. P. Buryukhaev; E. B. Matyugina; S. V. Borzenko; Z. B. Namsaraev; I. A. Bryantseva; E. N. Boldareva; D. Yu. Sorokin; B. B. Namsaraev

2010-01-01

147

Anomalies of the natural electric field on Lake Baikal  

NASA Astrophysics Data System (ADS)

The paper presents results of observations of the electromagnetic field conducted on the ice and coast of Lake Baikal. The horizontal and vertical components of the electric field contain anomalous disturbances coinciding in time with earthquakes and with the origination of a crevice in the ice cover of the lake. A possible origin of the anomalous disturbances is considered.

Moroz, Yu. F.

2008-11-01

148

Lake Taneycomo  

Microsoft Academic Search

Significant changes in the fishery of 1,730-acre Lake Taneycomo resulted from the construction of Table Rock Dam immediately upstream on White River because water, released through the dam from a relatively low level, is consequently quite cool. Discharge temperatures range from 40 to 60 F, and the cold water influences a large portion of Lake Taneycomo.Netting indicated an excellent population

James P. Fry; Willis D. Hanson

1968-01-01

149

Evidence of deep circulation in two perenially ice-covered Antarctic lakes  

Microsoft Academic Search

The perennial ice covers found on many of the lakes in the McMurdo Dry Valley region of the Antarctic have been postulated to severely limit mixing and convective turnover of these unique lakes. In this work, we utilize chlorofluorocarbon (CFC) concentration profiles from Lakes Hoare and Fryxell in the McMurdo Dry Valley to determine the extent of deep vertical mixing

Scott W. Tyler; Peter G. Cook; Anya Z. Butt; James M. Thomas; Peter T. Doran; W. Berry Lyons

1998-01-01

150

Pseudo two?dimensional simulations of internal and boundary fluxes in stratified lakes and reservoirs  

Microsoft Academic Search

New mixing algorithms to model the vertical mixing processes in stratified lakes have been developed for the Dynamic Reservoir Simulations Model, DYRESM, and have been validated using five lakes of different size, shape and wind forcing characteristics. An analysis of temperature profiles from Lake Kinneret, Canning Reservoir and Mundaring Reservoir, were used to develop a strong inverse relationship between the

P. S. Yeates; J. Imberger

2003-01-01

151

Distribution and Diversity of Archaea Corresponding to the Limnological Cycle of a Hypersaline Stratified Lake (Solar Lake, Sinai, Egypt)  

Microsoft Academic Search

The vertical and seasonal distribution and diversity of archaeal sequences was investigated in a hypersaline, stratified, monomictic lake, Solar Lake, Sinai, Egypt, during the limnological development of stratification and mixing. Archaeal sequences were studied via phylogenetic analysis of 16S rDNA sequences as well as denatur- ing gradient gel electrophoresis analysis. The 165 clones studied were grouped into four phylogenetically dif-

EDDIE CYTRYN; DROR MINZ; RONALD S. OREMLAND; YEHUDA COHEN

2000-01-01

152

Principles of lake sedimentology  

SciTech Connect

This book presents a comprehensive outline on the basic sedimentological principles for lakes, and focuses on environmental aspects and matters related to lake management and control-on lake ecology rather than lake geology. This is a guide for those who plan, perform and evaluate lake sedimentological investigations. Contents abridged: Lake types and sediment types. Sedimentation in lakes and water dynamics. Lake bottom dynamics. Sediment dynamics and sediment age. Sediments in aquatic pollution control programmes. Subject index.

Janasson, L.

1983-01-01

153

Nitrogen enrichment alters the structure and function of oligotrophic alpine lakes  

NASA Astrophysics Data System (ADS)

Recent research has demonstrated that meltwater from alpine glaciers enriches high-elevation lakes with reactive nitrogen (Nr), making these systems useful models of the effects of Nr enrichment on lake ecosystems. We compared phytoplankton diversity and productivity in a set of glacially-fed (GSF, which have moderate Nr concentrations) and snowmelt-fed (SF, which have very low Nr concentrations) lakes situated in the central Rocky Mountains of North America to better understand the effects of nitrogen enrichment on the structure and function of lakes. In three lakes of each type, we determined the vertical distribution of the algal standing crop, measured primary productivity rates with 14C uptake experiments, and compared phytoplankton richness and community structure. Comparing the two lake types, primary productivity rates were higher in GSF lakes, but average (i.e., vertically-integrated) chlorophyll concentrations did not differ. However, algal biomass was higher in the epi- and metalimnion of GSF lakes while it was equivalent in the hypolimnion of both lake types, suggesting different vertical gradients of algal standing crop with Nr enrichment. Phytoplankton species richness was lower in GSF lakes compared to SF lakes, with SF lakes generally having a greater diversity of phyla represented as well. Our results suggest that even moderate Nr enrichment alters the productivity and diversity of oligotrophic lakes.

Saros, J. E.; Slemmons, K. E.

2011-12-01

154

Hydro?isostatic deflection and tectonic tilting in the central Andes: Initial results of a GPS survey of Lake Minchin shorelines  

Microsoft Academic Search

Stilciently large lake loads provide a means of probing theological stratification of the crust and upper mantle. Lake Minchin was the largest of the late ~leistocene pluvial lakes in the central Andes. Prominent shorelines, which formed during tempora~ still-stands in the climatically driven lake level history, preserve records of lateral variations in subsequent net vertical motions. At its maximum extent

Shanaka L. de Silva; Donald R. Currey; Robert S. Emengefi; Karl D. Lillquist; Andrea Donnellan; Bruce Worden

1994-01-01

155

Molecular archives of climatic history: exploring patterns of genomic differentiation in endemic species radiations of ancient lakes (MOLARCH)  

NASA Astrophysics Data System (ADS)

Little is known about the evolutionary response of species to global climate change because time scales are too long to be directly studied. Recent phylogenetic studies on taxa inhabiting ancient lakes suggested that climate-induced environmental changes can be reconstructed by analyzing genetic patterns within and among species. In fact such evolutionary responses seem to coincide with climate driven lake level-fluctuations and to be concentrated within narrow periods of time. Yet, it remains unclear to what extent such changes occur simultaneously across taxonomic groups and ecological guilds. Our study combines phylogenetic and paleoclimate data to test how patterns of evolutionary diversification agree with predictions of three groups of hypotheses (i) the ‘turnover pulse' and ‘paleo-ecological incumbency' hypotheses, predicting that speciation pulses across major taxa coincide with times of major lake level changes; (ii) the ‘ecological locking' hypothesis, also predicts simultaneous speciation pulses but not necessarily at times of major lake level changes; (iii) the ‘individual response' hypothesis, predicts no correlation of speciation pulses across taxa. These hypotheses will be tested using mtDNA sequences from selected endemic taxa (fish, crustaceans) of Lakes Baikal and Tanganyika, the two oldest lakes on Earth. Patterns of intraspecific diversity (reflecting dynamics of population size changes) and of the synchrony of interspecific divergences across taxa are used to investigate the evolutionary effects of lake level changes on different time scales, in taxa occurring in different habitats, within lakes and across continents. Combined with paleoclimatic information this will elucidate the effects of global climatic induced changes on the more general dynamics of diversification, loss of variation, adaptive radiations and speciation events. Computer simulations of sequence evolution generated in various ecological scenarios will be used to investigate whether real sequence data of natural faunas can be used to evaluate and predict the impact of future climate change on these faunas.

Martens, K.

2009-04-01

156

Asian great lakes, especially Lake Biwa  

Microsoft Academic Search

The geological and biological history of Asian great lakes, especially Lake Biwa in Japan, are reviewed. The origins and affiliations of endemic flora and fauna are interpreted in light of current understanding of Lake Biwa. Recent historical changes in the lake, including detrimental impacts on native fauna and water quality are summarized. The social and cultural values associated with Asian

Hiroya Kawanabe

1996-01-01

157

Densities and distribution of flagellates and ciliates in the chemocline of saline, meromictic Lake Shunet (Siberia, Russia)  

Microsoft Academic Search

The vertical and seasonal distributions of the phytoflagellate Cryptomonas spp., and its most common, the planktonic ciliate predators (Oligotrichida, Scuticociliatida, Hypotrichida and Prostomatida) were investigated in chemocline region of small saline, meromictic lake Shunet (Siberia, Russia) during 2003 and 2005. The\\u000a lake has a pronounced chemocline, with abundance of purple and green sulphur bacteria. Vertical distribution of the Cryptomonas populations

E. B. Khromechek; Y. V. Barkhatov; D. Y. Rogozin

2010-01-01

158

Great Lakes Restoration Crosscut.  

National Technical Information Service (NTIS)

This crosscut budget provides information on Federal funding for Great Lakes restoration work in the following formats: Total Federal funding by agency, which includes national and Great Lakes programs, as well as Great Lakes projects, FYs 2004 enacted-20...

2008-01-01

159

Great Lakes  

USGS Publications Warehouse

The wild plants and animals and the natural systems that support them in the Great Lakes region are valuable resources of considerable local, regional, and national interest. They are also, in part, transboundary resources that the U.S. shares with its Canadian neighbors to the north. The way these resources are changing over time is inadequately known and is a concern for resource users and for those charged with managing and protecting these unique and valuable resources. This chapter describes the wild plants and animals and the systems that support them in the Great Lakes region; addresses their condition; and points out the gaps in our knowledge about them that, if filled, would aid in their conservation and appropriate use.

Edsall, Thomas A.

1998-01-01

160

Advanced Vertical Array Beamformer.  

National Technical Information Service (NTIS)

The advanced vertical array beamformer signal processor accomplishes acoustic beamforming of an underwater vertical array used in shallow water utilizing matched beam processing to suppress generated noise and/or ship radiated noise thereby increasing the...

T. C. Yang J. A. Mobbs

1998-01-01

161

Vertical Map Storage.  

ERIC Educational Resources Information Center

Discusses the superiority of vertical filing of maps in compressor-style vertical units over horizontal filing in drawers, emphasizing such factors as physical protection of the collection, ease of filing and retrieval, and efficient use of space. Disadvantages of vertical filing are also reviewed. (Author/JL)

Perry, Joanne M.

1982-01-01

162

TEACH Great Lakes  

NSDL National Science Digital Library

The Education And Curriculum Home site (TEACH) is a new component of the Great Lakes Information Network, with a focus on advancing Great Lakes-related educational materials for the broad audience of educators and students in the Great Lakes region and beyond. TEACH features mini-lessons on Great Lakes topics: environment, history and culture, geography, pollution, careers, and business. Geared for elementary through high school students, the modules are continually expanded and updated and include links to a glossary to help explain scientific terms and acronyms. Also included is a section for questions and answers, and education links. Specific topics within the site include: Great Lakes native flora, water levels on the Great Lakes, native peoples of the Great Lakes region, Great Lakes law and policy, introduction to the Great Lakes, how the lakes were formed, Great Lakes shoreline geology, non-native species, and urban sprawl.

163

Vertical bounce of two vertically aligned balls  

NASA Astrophysics Data System (ADS)

When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

Cross, Rod

2007-11-01

164

Tyee Lake project: Alaska's second lake tap  

Microsoft Academic Search

Environmentally, as well as in terms of pure water energy efficiency, lake taps are an ideal source of power. The basic concept is to tap into the bottom of a high mountain lake to use the high static head of water to spin turns. The Lake Tyee project starts with a tunnel at the lowest possible topographic point and uses

1983-01-01

165

Lake Trout Rehabilitation in Lake Ontario 2005  

Microsoft Academic Search

Abstract Each year we report ,on the ,progress toward rehabilitation of the ,Lake Ontario lake trout population covering the results of stocking, annual assessment surveys, creel surveys, and evidence of natural reproduction observed from all standard surveys performed by USGS and NYSDEC. During 2005, the number of yearling lake trout stocked in May was 45% below the target level of

B. f. Lantry; S. E. Prindle

166

Lake Effects: The Lake Superior Curriculum Guide.  

ERIC Educational Resources Information Center

|This curriculum guide was launched in response to a need for Lake Superior-specific educational materials and contains lessons and activities that can be used to teach about Lake Superior. The lessons in this book are divided into four sections. Each of the first three sections has a background section that provides basic information about Lake

Beery, Tom; And Others

167

Size-dependent habitat choice in Daphnia galeata Sars and size-structured interactions among zooplankton in a subarctic lake (lake Lombola, Norway)  

Microsoft Academic Search

Seasonal changes in vertical distribution of Daphnia galeata and other zooplankters were monitored in lake Lombola (69° 07? N). Depth-habitat use, availability of edible algae and zooplankton densities were recorded to examine seasonal changes in intensity of competition between Daphnia and the other herbivores in the lake. Early in July, the exephippial generation of Daphnia aggregated near the surface, independently

Raul Primicerio

2003-01-01

168

Effects of Changes in Meteorological Conditions on Lake Evaporation, Water Temperature, and Heat Budget in a Deep Lake  

NASA Astrophysics Data System (ADS)

To reveal effects of changes in meteorological conditions on lake evaporation, water temperature, and heat budget in a deep lake, sensitivity analyses have been performed for Lake Ikeda, Kagoshima prefecture. In the study, the sensitivities of three aspects to the 10%-increased solar radiation, air temperature, relative humidity, and wind speed were estimated based on numerical calculations for 1981-2005 with the verified one-dimensional mathematical model that computes thermal transfer in the lake. The results demonstrated that the meteorological component which gives the largest evaporation-promoting effect was solar radiation and the component which brings the largest lake-heating was air temperature. When solar radiation was increased, the vapor pressure difference between lake-surface and atmosphere was increased and the atmospheric stability was decreased, which present the desirable condition for evaporation. Air temperature being higher, the lake-surface was intensively heated by increased atmospheric radiation. As for the humidity case, lake evaporation was decreased in any season due to decrease in vapor pressure difference. Although rise in water temperature was caused by decrease in latent heat, it was inhibited with cooling by sensible heat. Wind being up, water temperature was fallen at the lake-surface and risen around the 20 m depth by vertical thermal mixing effect. The mixing effect prevented from releasing heat to atmosphere, resulting in the secondary large lake-heating but smaller than air temperature case.

Ito, Yuji; Momii, Kazuro

169

Hazardous crater lakes studied  

Microsoft Academic Search

Crater lakes usually sit on top of volcanic conduits and act as condensers of magmatic vapor. Studies of crater lakes can therefore provide information on both deep magmatic activity and variations in the degassing state of a shallow magmatic body. The Lake Nyos gas disaster of August 1986 and a similar event in August 1984 at Lake Monoun, both in

Minoru Kusakabe

1993-01-01

170

Technologies for lake restoration  

Microsoft Academic Search

Lakes are suffering from different stress factors and need to be restored using different approaches. The eutrophication remains as the main water quality management problem for inland waters: both lakes and reservoirs. The way to curb the degradation is to stop the nutrient sources and to accelerate the restoration with help of in-lake technologies. Especially lakes with a long retention

Helmut KLAPPER

2003-01-01

171

Rediscovery of lake balls in Lake Michigan  

USGS Publications Warehouse

For the first time in 70 years, the occurrence of a 'lake ball' in Lake Michigan is here reported in the literature. According to a published system of classification, the object we collected in 1978 was a 'false' lake ball. Dissection revealed that it was colonized by 5 chironomid larvae and 162 oligochaetes. The species and numerical proportions of the oligochaetes indicated that it was formed in or near the mouth of a eutrophic tributary rather than in the open waters of Lake Michigan where it was found. Because of their mobility, false lake balls may be ecologically important, serving as natural vehicles for the dispersal of invertebrates.

Schloesser, Donald W.; Hiltunen, Jarl K.; Owens, Randall W.

1983-01-01

172

The Lakes of Canada  

NSDL National Science Digital Library

This information about Canadian lakes includes a general overview of the lakes, which are divided into four quadrants. In each area the origins and general characteristics of the lakes are discussed. The site also features an interactive map. At each lake location there is information on the physical attributes, general description, and watershed of the lake. Four additional chapters contain detailed information, which distinguishes lakes from other aquatic environments, explains the mechanisms by which lakes in Canada were created, discusses lake morphology, distribution of light and heat, and water movement, and discusses seasonal distribution as well as variations in distribution and concentration of oxygen. Aspects of nitrogen, phosphorus, and organic carbon cycling that pertain to lakes are addressed. In addition, one chapter provides statistical facts about different Canadian lakes.

173

Longevity of Lake Superior lake trout  

USGS Publications Warehouse

The age structure of mature lake trout Salvelinus namaycush from the Wisconsin waters of Lake Superior increased following a population recovery that has taken place since the 1960s. As the population aged, it became apparent that scales were unreliable aging structures. Beginning in 1986, we examined both scale and sagittal otolith ages from tagged fish with a known period at liberty. We found large discrepancies in scale and sagittal otolith ages of mature fish, such that scale ages were biased low. We estimated lake trout living up to 42 years, which is greater than previously reported from Lake Superior. Investigators studying lake trout population dynamics in the Great Lakes should be aware that lake trout can live longer than previously thought.

Schram, Stephen T.; Fabrizio, Mary C.

1998-01-01

174

Modeling basin-scale internal waves in a stratified lake  

Microsoft Academic Search

Basin-scale internal waves provide the driving forces for vertical and horizontal fluxes in a stratified lake below the wind-mixed layer. Thus, correct modeling of lake mixing and transport requires accurate modeling of basin- scale internal waves: examining this capability with a hydrostatic, z-coordinate three-dimensional (3D) numerical model at coarse grid resolutions is the focus of this paper. It is demonstrated

Ben R. Hodges; Jörg Imberger; Angelo Saggio; K. B. Winters

2000-01-01

175

Two Antarctic desert lakes  

Microsoft Academic Search

The optical and biological propertics of ice-covcrcd Lakes Vanda and Bonncy, Antarctica, were observed during two austral summers. The lakes arc among the clearest known, with extinction coefficients as low as 0.031 for blue light in Lake Vanda and 0.069 for green light in Lake Bonney. Temperature and conductivity measurements in a shallow lake on Cape Evans, Antarctica, suggest a

CHARLES R. GOLDMAN; DAVID T. MASON; JOHN E. HOBBIE

1967-01-01

176

First record of Daphnia lumholtzi Sars in the Great Lakes  

USGS Publications Warehouse

Adults of the cladoceran Daphnia lumholtzi, native to Australia, Africa, and parts of Asia, were first collected in August 1999 in Lake Erie. Individuals were collected near East Harbor State Park, Lakeside, Ohio from vertical plankton net tows. The average number of D. lumholtzi that were found (0.03/L) indicate that D. lumholtzi is beginning to establish itself in Lake Erie. The morphology of this Daphnia differs greatly from native species because of its elongated head and tail spine. This sighting is important because it acknowledges yet another exotic invader into the Great Lakes basin and it also shows that this, normally, warm water species continues to expand its range northward.

Muzinic, Christopher J.

2000-01-01

177

Mixotrophic ciliates in an Andean lake: dependence on light and prey of an Ophrydium naumanni population  

Microsoft Academic Search

SUMMARY 1. Planktonic ciliates were examined during a spring-summer period (November 1998- April 1999) in the ultraoligotrophic Lake Moreno Oeste (41?5¢ S and 71?33¢ W, 758 m a.s.l), which belongs to the Nahuel Huapi System (Patagonia, Argentina). The lake is deep (Zmaxà 90 m) and warm monomictic. 2. Sampling was performed at a mid-lake station, where vertical profiles of temperature

Beatriz E. Modenutti; Esteban G. Balseiro

2002-01-01

178

Hydrology of the lakes in Central Wohlthat Massif, East Antarctica: new results  

Microsoft Academic Search

In 1983\\/1984, in the course of the 28th Soviet Antarctic Expedition, waterbody, ice cover, and surrounding glaciers of the lakes Untersee and Obersee were sampled along some depth profiles. The geochemical data of those samples, now available, show the homogeneity of both large lakes in vertical (down to the maximum depth) as well as in lateral directions. The comparison of

Dietmar Haendel; Wolf-Dieter Hermichen; Reiner Höfling; Peter Kowski

2011-01-01

179

Transport by an intrusion generated by boundary mixing in a lake  

Microsoft Academic Search

A dye study was conducted to track an intrusion generated at the boundary of a small lake. Persistent turbid layers offshore presented evidence of possible intrusions from boundary mixing. After high winds, a streak of Rhodamine WT was injected at the boundary of the lake where the slope was between 5% and 10%. Both vertical profiles and longitudinal transects of

Danielle J. Wain; Chris R. Rehmann

2010-01-01

180

Lake Süßer See as a natural sink for heavy metals from copper mining  

Microsoft Academic Search

Lake Süßer See, west of Halle, Germany, is a natural sink for heavy metals, which are abundant in the streams crossing the Mansfeld copper shale mining and smelting district in Central Germany. The lake and its environment serve as a recreational area for the local residents. We investigated the vertical distribution of key metals such as Cu, Pb and Zn

Andreas Becker; Wolfgang Klöck; Kurt Friese; Peter Schreck; Hanns-Christian Treutler; Bernhard Spettel; Martine C Duff; W. EISENACHER

2001-01-01

181

Impact of internal waves on the spatial distribution of Planktothrix rubescens (cyanobacteria) in an alpine lake  

Microsoft Academic Search

The vertical and horizontal distribution of the cyanobacterium, Planktothrix rubescens, was studied in a deep alpine lake (Lac du Bourget) in a 2-year monitoring program with 11 sampling points, and a 24-h survey at one sampling station. This species is known to proliferate in the metalimnic layer of numerous deep mesotrophic lakes in temperate areas, and also to produce hepatotoxins.

Yannis Cuypers; Brigitte Vinçon-Leite; Alexis Groleau; Bruno Tassin; Jean-François Humbert; J-F Humbert

2011-01-01

182

Morphological and geochemical features of crater lakes in Costa Rica: an overview  

Microsoft Academic Search

This paper describes the compositional and morphological features of the crater lakes found in the volcanoes of Rincón de La Vieja, Poás, Irazú, Congo and Tenorio volcanoes (Costa Rica). As evidenced by the distribution of the water and dissolved gas chemistry along vertical profiles, the different fluid sources feeding the lakes reflect the present status of each of the volcanic

Franco TASSI; Orlando VASELLI; Erik FERNANDEZ; Eliecer DUARTE; Maria MARTINEZ; Antonio DELGADO HUERTAS; Francesco BERGAMASCHI

183

Effects of water color on predation regimes and zooplankton assemblages in freshwater lakes  

Microsoft Academic Search

Northern temperate lakes often have high water color because of high concentrations of dissolved organic carbon (DOC). Altered light, temperature, and oxygen profiles in these brown-water lakes should reduce the foraging abilities of planktivorous fish and reduce predation on zooplankton and invertebrate predators such as Chaoborus. Additionally, reduced diurnal vertical migration should limit exposure to cold temperatures and increase zooplankton

B. Wissel; W. J. Boeing; C. W. Ramcharan

2003-01-01

184

Resource Partitioning in Summer by Salmonids in South-Central Lake Ontario  

Microsoft Academic Search

During the summers of 1981 and 1982, we studied resource partitioning by stocked lake trout Salvelinus namaycush, brown trout Salmo trutta, and chinook salmon Oncorhynchus tshawytscha by fishing vertical gill nets at six distances from shore in south-central Lake Ontario. The nets were set at depths of approximately 15–45 m (nearshore stations, <4 km offshore) and more than 55 m

Robert A. Olson; Jimmy D. Winter; David C. Nettles; James M. Haynes

1988-01-01

185

Resource Partitioning in Summer by Salmonids in South-Central Lake Ontario  

Microsoft Academic Search

During the summers of 1981 and 1982, we studied resource partitioning by stocked lake trout Salvelinus namaycush, brown trout Salmo trutta, and chinook salmon Oncorhynchus tshawytscha by fishing vertical gill nets at six distances from shore in south-central Lake Ontario. The nets were set at depths of approximately 15-45 m (nearshore stations, <4 km offshore) and more than 55 m

ROBERT A. OLSON; JIMMY D. WINTER; DAVID C. NETTLES; James M. Haynes

1988-01-01

186

Hunger enhances vertical vection.  

PubMed

Hunger was found to facilitate visually induced illusory upward and downward self-motions (vertical vection), but not illusory self-motion in depth (vection in depth). We propose that the origin of this hunger effect lies in the possibility that vertical self-motions (both real and illusory) are more likely to induce changes in visceral state. PMID:23362680

Seno, Takeharu; Ito, Hiroyuki; Sunaga, Shoji; Palmisano, Stephen

2012-01-01

187

Aiding vertical guidance understanding  

Microsoft Academic Search

A study was conducted to evaluate training and displays for the vertical guidance system of a modern glass cockpit airliner. The experiment consisted of a complete flight performed in a fixed-base simulator with airline pilots. Three groups were used to evaluate a new flight mode annunciator display and vertical navigation training. Results showed improved pilot performance with training and significant

Everett Palmer; Martin Alkin; Peter Polson; Daniel McCrobie; Lance Sherry

1999-01-01

188

The need to correct for the Suess effect in the application of ? 13 C in sediment of autotrophic Lake Tanganyika, as a productivity proxy in the Anthropocene  

Microsoft Academic Search

The change in dissolved inorganic ?13C in the ocean resulting from the change in ?13C in atmospheric CO2 owing to anthropogenic activities (the Suess effect) is well known. The need to correct for the Suess effect when applying\\u000a ?13C in organic matter in lacustrine sediment deposited during the anthropocene as a productivity proxy, is widely although not\\u000a universally acknowledged. This

Piet Verburg

2007-01-01

189

Parallelism of amino acid changes at the RH1 affecting spectral sensitivity among deep-water cichlids from Lakes Tanganyika and Malawi  

PubMed Central

Many examples of the appearance of similar traits in different lineages are known during the evolution of organisms. However, the underlying genetic mechanisms have been elucidated in very few cases. Here, we provide a clear example of evolutionary parallelism, involving changes in the same genetic pathway, providing functional adaptation of RH1 pigments to deep-water habitats during the adaptive radiation of East African cichlid fishes. We determined the RH1 sequences from 233 individual cichlids. The reconstruction of cichlid RH1 pigments with 11-cis-retinal from 28 sequences showed that the absorption spectra of the pigments of nine species were shifted toward blue, tuned by two particular amino acid replacements. These blue-shifted RH1 pigments might have evolved as adaptations to the deep-water photic environment. Phylogenetic evidence indicates that one of the replacements, A292S, has evolved several times independently, inducing similar functional change. The parallel evolution of the same mutation at the same amino acid position suggests that the number of genetic changes underlying the appearance of similar traits in cichlid diversification may be fewer than previously expected.

Sugawara, Tohru; Terai, Yohey; Imai, Hiroo; Turner, George F.; Koblmuller, Stephan; Sturmbauer, Christian; Shichida, Yoshinori; Okada, Norihiro

2005-01-01

190

Measurements of supraglacial lake drainage and surface streams over West Greenland and effects on ice dynamics  

NASA Astrophysics Data System (ADS)

During the summer of 2011 we measured the filling and draining of two surface lakes in the Paakitsoq region of the West Greenland Ice Sheet (49.79 W, 69.57 N), together with the level of streams flowing into the basins feeding the lakes. We also used GPS to record the horizontal and vertical movement of the ice sheet surface at five locations surrounding the lakes for a two week period (overlapping the draining of the two lakes). In this talk we report results concerning the processes of lake filling and draining between the two lakes. 'Lake Half Moon', with a smaller catchment area, filled slowly at a steady rate over several days, then drained gradually over a 24 hour period as an existing moulin located outside the bottom of the lake became active; the lake level continued to drop very slowly over the remaining week as the surface stream leading from the lake to the moulin incised. 'Lake Ponting', with the larger catchment area, filled more rapidly and at an accelerating rate as depressions upstream of the lake filled with water, overflowed and delivered increasing volumes of water to the lake. Lake Ponting drained by hydrofracture following a particularly rapid rise in water level, generating a new ~ 800m long extensional crevasse on the ice sheet surface. The entire ~ 3 x 106 m3 lake drained within a few hours. For the Lake Pointing, we show, for the first time, a movie of the lake draining, showing many features that we observed right after its drainage. The rate of lake level lowering during the drainage varied; initially moderately rapid while the fractures formed and accommodated the water, then exceptionally rapid as the fractures reached the bed allowing the lake to drain completely. The analysis of the GPS data suggest that the different styles of lake draining affect the vertical and horizontal movement of the ice sheet in different ways. We also anticipate that the effect of the draining of Lake Ponting was affecting the GPS sensors in a different manner, hence providing information on how ice sheet dynamics (at which distance and direction) are impacted by the drainage of surface lakes.

Tedesco, M.; Willis, I. C.; Alexander, P. M.; Banwell, A. F.

2011-12-01

191

Thermal regimes of Florida lakes  

Microsoft Academic Search

Water column temperatures were determined monthly for 24 lakes and bimonthly for 5 lakes in peninsular Florida during 1979. Three geographical groups (north, central, south) were delineated from mean monthly water column temperatures for individual lakes. On a monthly basis, northern lakes were least similar to southern lakes, while central Florida lakes displayed greater affinity to the southern than to

John R. Beaver; Thomas L. Crisman; James S. Bays

1981-01-01

192

A theoretical analysis of vertical flow equilibrium  

NASA Astrophysics Data System (ADS)

The assumption of vertical flow equilibrium (VFE) and of parallel flow conditions, in general, is often applied to the modeling of flow and displacement in natural porous media. However, the methodology for the development of the various models is rather intuitive, and no rigorous method is currently available. We develop an asymptotic theory using as parameter the variable R(sub L) = (L/H) sq root of (k(sub V))/(k(sub H)). It is rigorously shown that present models represent the leading order term of an asymptotic expansion with respect to 1/(R(sub L)(exp 2)). Although this was numerically suspected, it is the first time that it is theoretically proven. Based on the general formulation, a series of models are subsequently obtained. In the absence of strong gravity effects, they generalize previous works by Zapata and Lake (1981), Yokoyama and Lake (1981), and Lake and Hirasaki (1981) on immiscible and miscible displacements. In the limit of gravity-segregated flow, we prove conditions for the fluids to be segregated and derive the Dupuit and Dietz (1953) approximations. Finally, we also discuss effects of capillarity and transverse dispersion.

Yortsos, Y. C.

1992-01-01

193

Simulation Study about the Influence of Macrophytes on Hydrodynamics in an extreme shallow Water Lake - Lake Federsee  

NASA Astrophysics Data System (ADS)

Lake Federsee is formed primarily by ice age processes and was subjected to strong siltation processes in post-glacial times, while in the last two centuries anthropogenic impact due to amelioration projects became more important. It has a maximum length of 2.4 km with a maximum width of 1.1 km and an area of 1.4 km2. Lake Federsee is the third largest lake in the federal state of Baden-Wuerttemberg situated in the south of Germany. It is characterized by its very flat bathymetry with a maximum depth of about 3.15 m and an average depth of about 1 m. In recent years Lake Federsee has undergone a strong reduction of the nutrient content, thus developing from hypertrophic states in the years 1980ies to eutrophic conditions in the years 2000ies. Since 2005 this development is accompanied by a change of the general habitus of the lake converting from a lake dominated by algae to a lake dominated by macrophytes. Changing successions of aquatic plants have been observed in the lake with strong seasonal variations in the composition and density of the vegetation cover, however forming often an almost complete coverage of the lake. In the present study the implementation of the hydrodynamic, three-dimensional model FLOW3D for this extreme shallow water lake will be presented. The impact of some numerical parameters will be investigated in a sensitivity study, which is aiming to set up the hydrodynamic model in an optimal way. The influence of the macrophyte population on general circulation processes and the vertical mixing processes in the lake will be discussed. It is shown by numerical simulations studies that both - circulation pattern and mixing processes - are influenced severely by macrophytes in the lake.

Wolf, T.; Barchmann, M.

2012-04-01

194

Lake Barkley Regional Plan.  

National Technical Information Service (NTIS)

The Lake Barkley Regional Plan includes (a) land use recommendations for the unincorporated portions of Lyon and Trigg Counties affected by the Lake, (b) seperate recommendations for revisions to the Cadiz General Plan, (c) recommendations for coordinatio...

D. P. Fogle

1965-01-01

195

Vertical Line Test  

NSDL National Science Digital Library

In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

196

Decadal Heat Accumulation in Ice-Covered Lakes of the McMurdo Dry Valleys, Antarctica  

NASA Astrophysics Data System (ADS)

Lakes integrate landscape processes and climate conditions. Most of the permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica are closed basin, receiving glacial melt water from streams for 10-12 weeks per year and lacking advective outflow. We measured vertical profiles of water temperature three lakes in Taylor Valley since 1988. From these measurements, calculated heat contents indicate that these three lakes have been gaining heat since 2002. Analyses of lake ice thickness, meteorological conditions, and stream water heat loads indicate that the main source of heat to these lakes is from the glacially fed streams. These results indicate that McMurdo Dry Valley lakes are sensitive indicators of climate processes in this polar desert landscape and demonstrate the importance of long-term data sets when addressing the effects of climate on ecosystem processes.

Gooseff, M. N.; Priscu, J. C.; Doran, P. T.; Chiuchiolo, A.; Bernzott, E. D.; Obryk, M.

2011-12-01

197

The Pantanal lakes  

Microsoft Academic Search

\\u000a More than anything else, the Pantanal is a land of lakes. There exists no census, but a prudent estimate would put the number\\u000a of lakes in the tens of thousands. Most of them are small lakes of 500 to 1000 m diameter. On the lands of one farm alone\\u000a (Fazenda Nhumirim), there are some 100 such small lakes (Mourão et

F. D. Por

198

Lake Layers: Stratification.  

ERIC Educational Resources Information Center

This teacher guide and student workbook set contains two learning activities, designed for fifth through ninth grade students, that concentrate on lake stratification and water quality. In the activities students model the seasonal temperature changes that occur in temperate lakes and observe the resulting stratification of lake waters. Students…

Brothers, Chris; And Others

199

Great Lakes: Chemical Monitoring  

ERIC Educational Resources Information Center

|The Tenth Great Lakes Regional Meeting of the American Chemical Society met to assess current Chemical Research activity in the Great Lakes Basin, and addressed to the various aspects of the theme, Chemistry of the Great Lakes. Research areas reviewed included watershed studies, atmospheric and aquatic studies, and sediment studies. (BT)|

Delfino, Joseph J.

1976-01-01

200

Quantifying anoxia in lakes  

Microsoft Academic Search

The anoxic factor (AF, days per year or per season) can be used to quantify anoxia in stratified lakes. AF is calculated from oxygen profiles measured in the stratified season and lake surface area (A,) as AF represents the number of days that a sediment area, equal to the whole-lake surface area, is overlain by anoxic water. Average AF for

Gertrud K. Niirnberg

1995-01-01

201

Great Minds? Great Lakes!  

ERIC Educational Resources Information Center

|This book contains lesson plans that provide an integrated approach to incorporating Great Lakes environmental issues into elementary subjects. The book is divided into three subject areas: (1) History, which includes the origins of the Great Lakes, Great Lakes people, and shipwrecks; (2) Social Studies, which covers government, acid rain as a…

Environmental Protection Agency, Chicago, IL. Great Lakes National Program Office.

202

A Killer Lake  

ERIC Educational Resources Information Center

|In 1986, Lake Nyos, a volcanic lake in Cameroon, released a huge amount of carbon dioxide gas, killing over 1,700 people in the surrounding area. This case study, developed for use in a limnology or aquatic biology course, explores that event, introducing students to concepts relating to lake formation, thermal stratification, and dissolved…

Horvath, Thomas

2005-01-01

203

Spatial Distribution of Vertical Shear.  

National Technical Information Service (NTIS)

Spatial variations in small scale vertical shear in the upper ocean are described, relationships between small scale vertical shear and density stratification are investigated, and the potential for predicting mean vertical shear from measurements of the ...

S. L. Patterson F. C. Newman D. M. Rubenstein R. B. Lambert

1981-01-01

204

Vertical Multijunction Solar Cells.  

National Technical Information Service (NTIS)

A theoretical analysis of the vertical multijunction (VMJ) solar cell was performed which indicated that using silicon certain configurations could be fabricated to satisfy the program objectives. Results indicate that initial AMO efficiencies of 15% can ...

P. M. Stella

1973-01-01

205

Stratification of microbial assemblages in Mono Lake, California, and response to a mixing event  

Microsoft Academic Search

Vertical profiles of microbial assemblages from samples of Mono Lake water collected in July 1994 and in April and July 1995 were obtained by analyzing DNA via the polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal RNA (rRNA) genes. The microbial assemblage was vertically stratified and distributions of individual ribotypes were coherent with temperature, salinity,

James T. Hollibaugh; Patricia S. Wong; Nasreen Bano; Sunny K. Pak; Ellen M. Prager; Cristián Orrego

2001-01-01

206

Seasonal evolution of the basin-scale internal wave field in a large stratified lake  

Microsoft Academic Search

The response of the water column to varying conditions of stratification and wind forcing was investigated in Lake Kinneret (Israel) using data collected from thermistor chains and acoustic Doppler current profilers during 1997 and 1998. The strong daily sea breeze was found to generate a vertical mode 1 internal Kelvin wave and basin-scale internal Poincarewaves of vertical modes 1, 2,

Jason P. Antenucci; Jörg Imberger; Angelo Saggio

2000-01-01

207

Temperature Stratification and Mixing Dynamics in a Shallow Lake With Submersed Macrophytes  

Microsoft Academic Search

This paper describes an investigation of temperature stratification and vertical mixing in lacustrine macrophyte beds. Field measurements in a shallow lake show pronounced diel temperature dynamics, driven by surface heat transfer. The temperature stratification data also indicate a significant dependence of vertical mixing characteristics on macrophyte stand height. While natural convective mixing during night-time cooling was rather uniform between measurement

William R. Herb; Heinz G. Stefan

2004-01-01

208

Water balance of selected floodplain lake basins in the Middle Bug River valley  

NASA Astrophysics Data System (ADS)

This study is the first attempt in the literature on the subject of comparing water balance equations for floodplain lake basins depending on the type of connection the lake has to its parent river. Where confluent lakes (upstream connections) were concerned, it was only possible to apply a classic water balance equation. When dealing with contrafluent lakes (downstream connections) as well as lakes with a complex recharge type (contrafluent-confluent) modified equations were created. The hydrological type of a lake is decided by high water flow conditions and, consequently, the duration of potamophase (connection with a river) and limnophase (the isolation of the lake), which determine the values of particular components and the proportion of the vertical to horizontal water exchange rate. Confluent lakes are characterised by the highest proportion of horizontal components (the inflow and runoff of river water) to the vertical ones (precipitation and evaporation). The smallest differences occur with respect to a contrafluent lake. In the case of confluent lakes, the relationship between water balance components resulted from the consequent water flow through the basin, consistent with the slope of the river channel and valley. The supplying channels of contrafluent lakes had an obsequent character, which is why the flow rate was lower. Lakes with a complex, contrafluent-confluent recharge type showed intermediate features. After a period of slow contrafluent recharge, the inflow of water through a downstream crevasse from the area of the headwater of the river was activated; this caused a radical change of flow conditions into confluent ones. The conditions of water retention in lake basins were also varied. Apart from hydrological recharge, also the orographic features of the catchment areas of the lakes played an important role here, for example, the distance from the river channel, the altitude at which a given catchment was located within the floodplain and the complexity of the channels of fluvial-water inflow.

Dawidek, J.; Ferencz, B.

2013-08-01

209

Effects of water quality and hydrologic drivers on periphyton colonization on Sparganium erectum in two Turkish lakes with different mixing regimes  

Microsoft Academic Search

The aim of this paper is to determine and compare the environmental factors controlling vertical colonisation of periphyton\\u000a on Sparganium erectum in a shallow eutrophic turbid lake, Manyas Lake, and an oligo-mesotrophic deep lake, Sapanca Lake, Turkey during the July\\u000a 1997–November 1998. To investigate the effect of the environmental factors on periphyton colonization on S. erectum, the stem was cut

Meriç Albay; Reyhan Akçaalan

2008-01-01

210

Turbulent kinetic energy balance as a tool for estimating vertical diffusivity in wind-forced stratified waters  

Microsoft Academic Search

Based on microstructure measurements in a simply shaped lake basin, the sources of vertical mixing in the stratified part of the water body were identified and estimates of their relative importance obtained by balancing turbulent kinetic energy introduced by the wind. It was found that (1) ;1.9% of the vertical wind energy flux P10 (;39 mW m 22 ), estimated

Alfred Wüest; Gabriel Piepke; David C. Van Senden

2000-01-01

211

Behavioral response of Lake Michigan Daphnia mendotae to Mysis relicta  

Microsoft Academic Search

We performed laboratory experiments to determine if Mysis relicta induce changes in the behavior of Daphnia mendotae collected from Lake Michigan. Laboratory results indicate that Daphnia perceived Mysis kairomones and responded by changing their vertical position in cylinders. Experiments using different resource levels, and two procedures to examine the potential effects of the chemical cues from Mysis or from particulate

Scott D. Peacor; Kevin L. Pangle; Henry A. Vanderploeg

2005-01-01

212

Microbiological Water Quality Of Lake Prespa And Its Tributaries  

Microsoft Academic Search

In parallel with physicochemical and biological investigations undertaken at Lake Prespa (from littoral at 3 stations and from a vertical profile in the pelagic zone at 4 points) and its tributaries (Golema, Kranska and Brajcinska), microbiological water quality analysis were conducted during 2004 and 2005. The total count of aerobic organotrophic bacteria were determined on nutritive agar; proteolytic on MPA

Lence Lokoska

213

Long Range Recording of Lake Superior 1966 Shot Points.  

National Technical Information Service (NTIS)

Observations of seismic waves generated by explosions in Lake Superior during the Early Rise Experiment have been made westward to a range of 2600 km. A phase filtering technique involving the vertical and horizontal motion, used to enhance the body phase...

C. A. Borcherdt B. T. R. Lewis R. P. Meyer J. R. Van Schaack

1968-01-01

214

Autotrophic processes in meromictic Big Soda Lake, Nevada  

Microsoft Academic Search

Daily rates of oxygenic photosynthesis (OP) by phytoplankton, anoxygenic photosynthesis (AP) by purple sulfur bacteria, and chemoautotrophic productivity (CP = dark CO, assimila- tion) were measured once each season in saline, meromictic Big Soda Lake. Total daily pro- ductivity and the relative importance of each autotrophic process varied with seasonal changes in vertical mixing, light availability, and the biomass of

JAMES E. CLOERN; BRIAN E. COLE; RONALD S. OREMLAND

1983-01-01

215

Mono Lake Web Site  

NSDL National Science Digital Library

Mono Lake Web Site is the homepage of the Mono Lake Committee and offers helpful information regarding the unique hypersaline and alkaline environment. Visitors will find information about the Mono Lake Committee, natural and political histories of the area, related water policies, a photo gallery with image descriptions, and links to related sites- including a clearinghouse. Those interested in Mono Basin birds will find sightings, counts, bird walks, and other related information. An additional feature, Mono Lake Live, offers up-to-the-minute data on road conditions, satellite images, weather, lake level, bird sightings, snow pack, and earthquakes.

Reis, Greg; Committee, Mono L.

216

Circulation and thermodynamics in a subglacial geothermal lake under the Western Skaftá cauldron of the Vatnajökull ice cap, Iceland  

NASA Astrophysics Data System (ADS)

The subglacial, geothermal lake beneath the Western Skaftá cauldron (depression) in the Vatnajökull ice cap, Iceland, was accessed by hot water drilling through the overlying 300 m-thick ice shelf. Most of the ca. 100-m water column was near 4.7°C, but was underlain by a distinct ~10 m-deep water mass at 3.5°C. The sensible heat content of the lake water is approximately twice the potential energy dissipated in outburst floods, and the temperature of the lake may be an important factor in the development of subglacial water courses of jökulhlaups from the lake. The lake temperature is higher than the temperature of maximum density, implying that convective heat transfer can take place in the lake. The vertical temperature structure suggests a large-scale recirculating flow in the lake, the rate of which was estimated from the lake temperatures and the chemical composition of a water sample.

Jóhannesson, Tómas; Thorsteinsson, Thorsteinn; Stefánsson, Andri; Gaidos, Eric J.; Einarsson, Bergur

2007-10-01

217

Hazardous crater lakes studied  

NASA Astrophysics Data System (ADS)

Crater lakes usually sit on top of volcanic conduits and act as condensers of magmatic vapor. Studies of crater lakes can therefore provide information on both deep magmatic activity and variations in the degassing state of a shallow magmatic body. The Lake Nyos gas disaster of August 1986 and a similar event in August 1984 at Lake Monoun, both in Cameroon, resulted from the accumulation of magmatic CO2 in the bottom layers of the lakes. Geochemical monitoring of crater lakes is a promising tool for forecasting not only limnic but also volcanic eruptions. Acid-mineralized waters formed by condensation of hot magmatic volatiles in crater lakes are thought to bear some resemblance to hydrothermal fluids acting in the genesis of acid-sulfate alteration and Au-Cu-Ag mineralization of volcanic-hosted precious metal deposits.

Kusakabe, Minoru

218

Lake trout rehabilitation in Lake Huron  

USGS Publications Warehouse

Efforts to restore lake trout (Salvelinus namaycush) in Lake Huron after their collapse in the 1940s were underway in the early 1970s with completion of the first round of lampricide applications in tributary streams and the stocking of several genotypes. We assess results of rehabilitation and establish a historical basis for comparison by quantifying the catch of spawning lake trout from Michigan waters in 1929-1932. Sixty-eight percent of this catch occurred in northern waters (MH-1) and most of the rest (15%) was from remote reefs in the middle of the main basin. Sea lampreys (Petromyzon marinus) increased in the early 1980s in the main basin and depressed spawning populations of lake trout. This increase was especially severe in northern waters and appeared to be associated with untreated populations in the St. Marys River. Excessive commercial fishing stemming from unresolved treaty rights also contributed to loss of spawning fish in northern Michigan waters. Seneca-strain lake trout did not appear to be attacked by sea lampreys until they reached a size > 532 mm. At sizes > 632 mm, Seneca trout were 40-fold more abundant than the Marquette strain in matched-planting experiments. Natural reproduction past the fry stage has occurred in Thunder Bay and South Bay, but prospects for self-sustaining populations of lake trout in the main basin are poor because sea lampreys are too abundant, only one side of the basin is stocked, and stocking is deferred to allow commercial gillnetting in areas where most of the spawning occurred historically. Backcross lake trout, a lake trout x splake (s. Fontinalis x s. Namaycush) hybrid, did not reproduce in Georgian Bay, but this genotype is being replaced with pure-strain lake trout, whose early performance appears promising.

Eshenroder, Randy L.; Payne, N. Robert; Johnson, James E.; Bowen, Charles, II; Ebener, Mark P.

1995-01-01

219

Water Velocity and Suspended Solids Measurements by In-situ Instruments in Upper Klamath Lake, Oregon  

USGS Publications Warehouse

The U. S. Geological Survey conducted hydrodynamic measurements in Upper Klamath Lake during four summer seasons (approximately mid-June to mid-September) during 2003 to 2006. Measurements included water current profiles made by acoustic Doppler current profilers at a number of fixed locations in the lake during all four years as well as from a moving boat during 2005 and 2006. Measurements of size distribution of suspended material were made at four locations in the lake during 2004-2006. Raw (unfiltered) data are presented as time series of measurements. In addition, water-velocity data have been filtered to remove wind-induced variations with periods less than thirty hours from the measurements. Bar graphs of horizontal and vertical water speed and acoustic backscatter have been generated to discern diurnal variations, especially as they relate to wind patterns over the lake. Mean speeds of the horizontal currents in the lake range between about 3.5 to 15 cm/s with the higher speeds at the deep locations in the trench on the west side of the lake. Current directions generally conform to the lake's bathymetry contours and the water circulation pattern is usually in a clockwise direction around the lake as established by the prevailing north to northwesterly surface winds in the region. Diurnal patterns in horizontal currents probably relate to diurnal wind patterns with minimum wind speeds near noon and maximum wind speeds near 2100. Diurnal variations in vertical velocities do not appear to be related to wind patterns; they do appear to be related to expected patterns of vertical migration of Aphanizomenon flos aquae, (AFA) the predominant species of blue-green algae in the lake. Similarly, diurnal variations in acoustic backscatter, especially near the lake's surface, are probably related to the vertical migration of AFA.

Gartner, Jeffrey W.; Wellman, Roy E.; Wood, Tamara M.; Cheng, Ralph T.

2007-01-01

220

On the cyclonic mean circulation of large lakes  

PubMed Central

In large lakes, during the heating season, the combination of surface wind drift and solar heating results in the horizontal transport of some of the absorbed heat into the coastal zone. Large-scale vertical movements associated with alternating upwellings and downwellings distribute the heat over a deeper water mass than at mid-lake. As a result, the mean shape of isotherm surfaces is “domed” and, correspondingly, the lake surface is slightly raised near shore and depressed over the center thermocline dome. The mean circulation in geostrophic equilibrium with this surface elevation field is a cyclonic gyre. In Lake Ontario, the amplitude of the mean surface velocity associated with this gyre is of the order of 3 cm sec-1.

Csanady, G. T.

1977-01-01

221

Origin and deformation of Holocene shoreline terraces, Yellowstone Lake, Wyoming  

SciTech Connect

Geodetic surveys within the Yellowstone caldera have documented active uplift that is most likely caused by magmatic processes in the upper crust. Along the northeast shore of Yellowstone Lake, maximum relative uplift rates are 10 mm/yr for the period 1923-1975. However, information on deformation prior to historic instrumental records has been lacking. In this study, closely spaced data on elevations of postglacial shoreline terraces around the north end of Yellowstone Lake reveal complex tilting. Though most Holocene deformation is probably magma related, the pattern of shoreline tilting deviates significantly from the historic pattern of roughly symmetric inflation of the caldera. Along the northeast shore, where tilt directions of historic and shoreline deformation are similar, differential uplift of a > 2500-yr-old terrace is roughly 10 m; this gives a maximum uplift rate of 4 mm/yr. These unique Holocene terraces may exist due to episodic deformation because vertical movements affecting the lake outlet directly control lake level.

Meyer, G.A.; Locke, W.W.

1986-08-01

222

Ice flow modelling in the area of Subglacial Lake Ellsworth.  

NASA Astrophysics Data System (ADS)

We use Elmer to model the 3D flow of ice in area with a simplified topography resembling Lake Ellsworth (Antarctica): a suglacial lake sitting in the bottom of a deep valley. Boundary conditions are periodic on the lateral sides. The upper surface is a free-surface with zero accumulation. On the bottom surface the lake is represented by an area with no basal drag. The results show that ice is drained toward the deep valley where high velocities are obtained. We observe a flattening of the free surface above the lake. Vertical velocity profiles are affected by the large variations in bed topography and sliperiness and are very different from place to place showing the effects of longitudinal stress gradients in the area.

Jay-Allemand, Maxime; Gillet-Chaulet, Fabien; Hindmarsh, Richard C. A.

2010-05-01

223

Large Lake Sampling Program Assessment Report for Leech Lake, 1995.  

National Technical Information Service (NTIS)

The Large Lake Monitoring Program was implemented to monitor and evaluate fish populations within Minnesota's large walleye lakes. For Leech Lake, this program includes annual fish population monitoring, natural reproduction checks, water quality monitori...

N. A. Haukos

1995-01-01

224

14 CFR 93.69 - Special requirements, Lake Campbell and Sixmile Lake Airports.  

Code of Federal Regulations, 2010 CFR

... false Special requirements, Lake Campbell and Sixmile Lake Airports. 93.69...93.69 Special requirements, Lake Campbell and Sixmile Lake Airports. Each person operating an aircraft to or from Lake Campbell or Sixmile Lake Airport shall...

2010-01-01

225

14 CFR 93.69 - Special requirements, Lake Campbell and Sixmile Lake Airports.  

Code of Federal Regulations, 2010 CFR

... false Special requirements, Lake Campbell and Sixmile Lake Airports. 93.69...93.69 Special requirements, Lake Campbell and Sixmile Lake Airports. Each person operating an aircraft to or from Lake Campbell or Sixmile Lake Airport shall...

2009-01-01

226

Modulation of the earthquake cycle at the southern San Andreas fault by lake loading  

NASA Astrophysics Data System (ADS)

Changes in the level of ancient Lake Cahuilla over the last 1500 years in the Salton Trough alter the state of stress by bending the lithosphere in response to the applied lake load and by varying the pore pressure magnitude within the crust. The recurrence interval of the lake is similar to the recurrence interval of rupture on the southern San Andreas and San Jacinto faults, both of which are partially covered by the lake at its highstand. Furthermore, four of the last five ruptures on the southern San Andreas fault have occurred near a time of substantial lake level change. We investigate the effect of Coulomb stress perturbations on local faults due to changing level of Lake Cahuilla to determine a possible role for the lake in affecting the timing of fault rupture. Coulomb stress is calculated with a three-dimensional model of an elastic plate overlying a viscoelastic half-space. Plate thickness and half-space relaxation time are adjusted to match observed vertical deformation since the last lake highstand. The lake cycle causes positive and negative Coulomb stress perturbations of 0.2-0.6 MPa on the southern San Andreas within the lake and 0.1-0.2 MPa on the southern San Andreas outside the lake. These Coulomb stress perturbations are comparable to stress magnitudes known to have triggered events at other faults along the North America-Pacific plate boundary.

Luttrell, Karen; Sandwell, David; Smith-Konter, Bridget; Bills, Bruce; Bock, Yehuda

2007-08-01

227

Control of primary productivity and the significance of photosynthetic bacteria in a meromictic kettle lake. Mittlerer Buchensee, West-Germany  

Microsoft Academic Search

During 1986 planktonic primary production and controlling factors were investigated in a small (A0 = 11.8 · 103 m2, Zmax = 11.5 m) meromictic kettle lake (Mittlerer Buchensee). Annual phytoplankton productivity was estimated to ca 120 gC · m-2 · a-1 (1,42 tC · lake-1 · a-1). The marked thermal stratification of the lake led to irregular vertical distributions of

Jörg Overmann; Max M. Tilzer

1989-01-01

228

Tyee Lake project: Alaska's second lake tap  

SciTech Connect

Environmentally, as well as in terms of pure water energy efficiency, lake taps are an ideal source of power. The basic concept is to tap into the bottom of a high mountain lake to use the high static head of water to spin turns. The Lake Tyee project starts with a tunnel at the lowest possible topographic point and uses the elevation differential between the lake bottom and originating point of the tunnel to multiply the height of the hydrostatic head. The water will generate 20 MW with a capacity to take on another 10-MW generator. The power generating system will be concealed inside the mountain with a small powerhouse and tail race visible. The cost of the project was over $60 million.

Sieber, O.V.

1983-12-01

229

Secchi disk and photometer estimates of light regimes in Alaskan lakes: Effects of yellow color and turbidity  

Microsoft Academic Search

Variations in underwater light regimes among 58 Alaskan lakes were indexed by Secchi disk (SD) transparency and by vertical attenuation coefficients (&) and euphotic zone depths (EZD) derived from using a submarine photometer (SP) sensitive to photosynthetically active radiation (PAR). Lake-specific ratios between turbidity (light scattering) and color (light absorption) explained 52% of the variation (P < 0.0001) in Kd

J. P. KOENINGS; J. A. EDMUNDSON

1991-01-01

230

Two-dimensional temperature and dissolved oxygen dynamics in the littoral region of an ice-covered lake  

Microsoft Academic Search

Temperature and dissolved oxygen were measured along a transect of Ryan Lake, MN, from February 3 to March 25, 1999 to gain information on water quality dynamics associated with convective exchange processes between littoral and profundal regions of an ice-covered mid-latitude lake. The observations show a difference in the vertical distribution of heat and dissolved oxygen between the shallow and

Dragoslav L. Stefanovic; Heinz G. Stefan

2002-01-01

231

An Integrated Hydrodynamic and Pollutant Transport Model for the Nearshore Areas of the Great Lakes and Their Tributaries  

Microsoft Academic Search

This thesis deals with the modelling of the circulation and pollutant transport in the nearshore areas of lakes and their tributaries. An integrated hydrodynamic\\/pollutant transport model was developed which operates in an interactive environment and is equipped with powerful graphics. The model can predict: (a) the horizontal and vertical current structure in the lake under isothermal and stratified conditions for

Jian Wu

1993-01-01

232

An integrated hydrodynamic and pollutant transport model for the nearshore areas of the Great Lakes and their tributaries  

Microsoft Academic Search

This thesis deals with the modelling of the circulation and pollutant transport in the nearshore areas of lakes and their tributaries. An integrated hydrodynamic\\/pollutant transport model was developed which operates in an interactive environment and is equipped with powerful graphics. The model can predict: (a) the horizontal and vertical current structure in the lake under isothermal and stratified conditions for

Jian Wu

1994-01-01

233

Is Lake Prespa Jeopardizing the Ecosystem of Ancient Lake Ohrid?  

Microsoft Academic Search

Lake Prespa and Lake Ohrid, located in south-eastern Europe, are two lakes of extraordinary ecological value. Although the\\u000a upstream Lake Prespa has no surface outflow, its waters reach the 160 m lower Lake Ohrid through underground hydraulic connections.\\u000a Substantial conservation efforts concentrate on oligotrophic downstream Lake Ohrid, which is famous for its large number of\\u000a endemic and relict species. In this

A. Matzinger; M. Jordanoski; E. Veljanoska-Sarafiloska; M. Sturm; B. Müller; A. Wüest

2006-01-01

234

Recent sediment geochemistry of an alkaline lake: Lake Acigöl (Denizli), SW Anatolia Turkey  

NASA Astrophysics Data System (ADS)

Lake Ac?göl (Denizli) is one of the largest alkaline lake in Turkey. Surface, and shallow core samples was studied to determine the effects of riverine and aeolian processes on sediment physical properties and sediment geochemistry. Total organic carbon, total nitrogen content and major and minor element geochemistry of Lake Ac?göl sediments were investigated. Major (Si, Ti, Al, Fe, Mg, Ca, K, Na, P, S) and trace elements (Mn, As, V, Cr, Ni, Cu, Zn, Sr, Y, Zr, Ba, Pb) showed significant differences in bulk chemical composition between the surface and shallow core samples. Sediment properties were examined by water content, loss-on-ignition (LOI). While most of core samples characteristic with relative LOI increase from bottom towards sediment surface, limited core samples that were taken from eastern shore of the lake show increase of LOI values from sediment surface towards bottom, suggesting shallow water levels, aeolian and dentritic riverine inputs on a regional scale. The Fe/Mn ratio was calculated to study changes in the redox potential. Distribution of Fe, Mn, and S concentration were related to redox condition of lake sediment and are due to mobilization of these elements in the pore waters. Calculated two particulate ratios (C:N and N:P) indicate predominantly lacustrine origin. Vertical changes of heavy metals occur in the all shallow downcore profiles, although the concentrations keep to ppm levels. Principal components analysis (PCA) was also used to examine all studied parameters and intercorrelations among the variables.

Budakoglu, M.; Karaman, M.; Karabel, S. B.; Geredeli, S. G.; Bulbul, A.; Kurt, H.; Uzasci, S.; Kan, A.; Akay, A. K.; Yilmaz, F. R.; Gumus, L.; Civas, M.; Sevis, C.; Kumral, M.

2012-04-01

235

Ecosystem effects of thermal manipulation of a whole lake, Lake Breisjøen, southern Norway (THERMOS project)  

NASA Astrophysics Data System (ADS)

We conducted a 3-year artificial deepening of the thermocline in the dimictic Lake Breisjøen, southern Norway, by means of a large submerged propeller. An adjacent lake served as untreated reference. The manipulation increased thermocline depth from 6 to 20 m, caused a significant increase in the heat content, and delayed ice-on by about 20 days. There were only minor changes in water chemistry. Concentrations of sulphate declined, perhaps due to greater reduction of sulphate at the sediment-water interface. Concentrations of particulate carbon and nitrogen decreased, perhaps due to increased sedimantation velocity. Water transparency increased. There was no significant change in concentration of phosphorus, the growth-limiting nutrient. There were few significant changes in principal biological components. Phytoplankton biomass and productivity did not change, although the chlorophyll-a concentration showed a small decrease. Phytoplankton species richness increased, and the species composition shifted. Growth of periphyton increased. There was no change in the macrophyte community. The manipulation did not affect the zooplankton biodiversity, but caused a significant shift in the relative abundance (measured as biomass) in the two major copepod species. The manipulation did not affect the individual density, but appeared to have changed the vertical distribution of zoobenthos. Fish populations were not affected. The lake is oligotrophic and clearwater and the manipulation did not change the supply of phosphorus, and thus there were only minor changes in lake chemistry and biology. Effects might be larger in eutrophic and dystrophic lakes in which internal processes are stronger.

Lydersen, E.; Aanes, K. J.; Andersen, S.; Andersen, T.; Brettum, P.; Baekken, T.; Lien, L.; Lindstrøm, E. A.; Løvik, J. E.; Mjelde, M.; Oredalen, T. J.; Solheim, A. L.; Romstad, R.; Wright, R. F.

2007-09-01

236

Ecosystem effects of thermal manipulation of a whole lake, Lake Breisjøen, southern Norway (THERMOS project)  

NASA Astrophysics Data System (ADS)

We conducted a 3-year artificial deepening of the thermocline in the dimictic Lake Breisjøen, southern Norway, by means of a large submerged propeller. An adjacent lake served as untreated reference. The manipulation increased thermocline depth from 6 to 20 m, caused a significant increase in the heat content, and delayed ice-on by about 20 days. There were only minor changes in water chemistry. Concentrations of sulphate declined, perhaps due to greater reduction of sulphate at the sediment-water interface. Concentrations of particulate carbon and nitrogen decreased, perhaps due to increased sedimentation velocity. Water transparency increased. There was no significant change in concentration of phosphorus, the growth-limiting nutrient. There were few significant changes in principal biological components. Phytoplankton biomass and productivity did not change, although the chlorophyll-a concentration showed a small decrease. Phytoplankton species richness increased, and the species composition shifted. Growth of periphyton increased. There was no change in the macrophyte community. The manipulation did not affect the zooplankton biodiversity, but caused a significant shift in the relative abundance (measured as biomass) in the two major copepod species. The manipulation did not affect the individual density, but appeared to have changed the vertical distribution of zoobenthos. Fish populations were not affected. The lake is oligotrophic and clearwater and the manipulation did not change the supply of phosphorus, and thus there were only minor changes in lake chemistry and biology. Effects might be larger in eutrophic and dystrophic lakes in which internal processes are stronger.

Lydersen, E.; Aanes, K. J.; Andersen, S.; Andersen, T.; Brettum, P.; Baekken, T.; Lien, L.; Lindstræm, E. A.; Lævik, J. E.; Mjelde, M.; Oredalen, T. J.; Solheim, A. L.; Romstad, R.; Wright, R. F.

2008-03-01

237

The Living Lakes  

NSDL National Science Digital Library

Living Lakes Partnership, a nonprofit organization has a goal to "create and support a network within which local lake organizations can find critical kinds of assistance for promoting sustainable development in lake areas." Their award winning site highlights nearly twenty lakes around the world, describing their individual, watershed, and biological characteristics as well as the geologic and human history of the area. The Living With Lakes section discusses lake management and conservation issues dealing with agriculture and urban areas (such as pollution and habitat loss). Other links include a photo gallery, news and events section, discussion groups, and much more. Visitors will enjoy the rich content and visuals that make up this site and will find themselves exploring it for some time and learning along the way.

2002-01-01

238

Great Lakes Monthly Hydrologic Data.  

National Technical Information Service (NTIS)

Accurate hydrologic data (over-land precipitation, over-lake precipitation, runoff, lake evaporation, net basin supplies, connecting channel flows, diversion flows, beginning-of-month lake levels, and changes in storage) are required for simulation, forec...

T. E. Croley T. S. Hunter

1994-01-01

239

Vertical Bargraph Display.  

National Technical Information Service (NTIS)

The program involves the generation of an advance approach to electronic aircraft instrumentation. The display media is a twisted nematic liquid crystal display (TN LCD). The instrument was designed as a one-for-one replacement for the existing vertical b...

S. Aftergut G. M. Gozeba C. R. Stein R. L. Skovholt W. W. Thurlow

1975-01-01

240

Vertical Differentiation among Occupations.  

ERIC Educational Resources Information Center

|It is reported that research on the socioeconomic achievement process has begun to generate anomalous findings, many of which involve occupational status as conventionally measured. The author proposes a theory of vertical occupational differentiation based on the role activities of occupational incumbents. (Author/RLV)|

Spaeth, Joe L.

1979-01-01

241

Great Lakes water levels  

Microsoft Academic Search

A new publication, Great Lakes Water Levels, 1860-1970, has been issued by the Lakes Survey Center of the National Oceanic and Atmospheric Administration. \\u000a\\u000aThe book contains tabular records of monthly and annual average water surface elevations for each of the more than 50 permanent gages in the Lake Survey network. There are also summaries of the average and extreme levels

Anonymous

1971-01-01

242

Big lake records preserved in a little lake’s sediment: an example from Silver Lake, Michigan, USA  

Microsoft Academic Search

We reconstruct postglacial lake-level history within the Lake Michigan basin using soil stratigraphy, ground-penetrating radar\\u000a (GPR), sedimentology and 14C data from the Silver Lake basin, which lies adjacent to Lake Michigan. Stratigraphy in nine vibracores recovered from the\\u000a floor of Silver Lake appears to reflect fluctuation of water levels in the Lake Michigan basin. Aeolian activity within the\\u000a study area

Timothy G. Fisher; Walter L. Loope; William Pierce; Harry M. Jol

2007-01-01

243

Great Lakes Literacy Principles  

NASA Astrophysics Data System (ADS)

Lakes Superior, Huron, Michigan, Ontario, and Erie together form North America's Great Lakes, a region that contains 20% of the world's fresh surface water and is home to roughly one quarter of the U.S. population (Figure 1). Supporting a $4 billion sport fishing industry, plus $16 billion annually in boating, 1.5 million U.S. jobs, and $62 billion in annual wages directly, the Great Lakes form the backbone of a regional economy that is vital to the United States as a whole (see http://www.miseagrant.umich.edu/downloads/economy/11-708-Great-Lakes-Jobs.pdf). Yet the grandeur and importance of this freshwater resource are little understood, not only by people in the rest of the country but also by many in the region itself. To help address this lack of knowledge, the Centers for Ocean Sciences Education Excellence (COSEE) Great Lakes, supported by the U.S. National Science Foundation and the National Oceanic and Atmospheric Administration, developed literacy principles for the Great Lakes to serve as a guide for education of students and the public. These “Great Lakes Literacy Principles” represent an understanding of the Great Lakes' influences on society and society's influences on the Great Lakes.

Fortner, Rosanne W.; Manzo, Lyndsey

2011-03-01

244

A large-scale experiment in the control of aquatic snails by the use of molluscicides on a sugar estate in the Northern Region of Tanganyika*  

PubMed Central

The author describes a large-scale experiment in which the molluscicide Bayer 73 (Bayluscide) was used in an attempt to eliminate Biomphalaria pfeifferi, the snail host of Schistosoma mansoni, from an irrigation system in Tanganyika. Applied at a concentration of 1 p.p.m., the molluscicide gave a very high kill of snails and much of the treated area remained completely free of vector snails for seven months after treatment. However, there were a few survivors in small pockets associated with a drainage area that became flooded during heavy rains coincident with the application of molluscicide. From these survivors a dramatic resurgence of snails occurred in some of the treated canals. This resurgence may be analogous to similar phenomena observed in some insecticide work. The suggestion is made that removal of parasites and predators, in particular trematode parasites, by a molluscicide might increase the snail's capacity for repopulation. Studies of the seasonal fluctuations of snail population density in an adjacent, but separate, irrigation system suggest that molluscicide applications would be more effective if timed to coincide with the end of the rainy seasons. ImagesFIG. 2

Crossland, N. O.

1963-01-01

245

Lakes, Lagerstaetten, and Evolution  

NASA Astrophysics Data System (ADS)

The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method for determining species diversity changes in the terrestrial environment because of their faunal completeness. Important Konservat Lagerstaetten, such as the Green River Formation (US) and Messel (Germany), both Eocene in age, are found in lake sediments and show a remarkable faunal diversity for both vertebrates and invertebrates. To date information from nearly 25 lake lagerstaetten derived from different types of lake basins from the Carboniferous to the Miocene have been collected and described. Carboniferous sites derive from the cyclothems of Midcontinent of the US while many Cenozoic sites have been described from North and South America as well as Europe and Australia. Asian sites contain fossils from the Mesozoic and Cenozoic. With this data, insight into the evolutionary processes associated with lake systems can be examined. Do lakes act as unique evolutionary crucibles in contrast to marine systems? The speciation of cichlid fishes in present-day African lakes appears to be very high and is attributed to the diversity of environments found in large rift lakes. Is this true of all ancient lakes or just large rift lakes? The longevity of a lake system may be an important factor in allowing speciation and evolutionary processes to occur; marine systems are limited only in the existence of environments as controlled by tectonics and sea level changes, on the order of tens of millions of years. Rift lakes are normally the longest lived in the millions of years. Perhaps there are only certain types of lakes in which speciation of nonmarine organisms, and thus the evolution of freshwater organisms, can occur in a short geologic timespan. Because of their unique and varied conditions, the evolution of nonmarine organisms may be linked to lake basin type as well as lake longevity.

Kordesch, E. G.; Park, L. E.

2001-12-01

246

Testing the spatial and temporal framework of speciation in an ancient lake species flock: the leech genus Dina (Hirudinea: Erpobdellidae) in Lake Ohrid  

NASA Astrophysics Data System (ADS)

Ancient Lake Ohrid on the Balkan Peninsula is considered to be the oldest ancient lake in Europe with a suggested Plio-Pleistocene age. Its exact geological age, however, remains unknown. Therefore, molecular clock data of Lake Ohrid biota may serve as an independent constraint of available geological data, and may thus also help to refine age estimates. Such evolutionary data may also help unravel potential biotic and abiotic factors that promote speciation events. Here, mitochondrial sequencing data of one of the largest groups of endemic taxa in Lake Ohrid, the leech genus Dina, is used to test whether it represents an ancient lake species flock, to study the role of horizontal and vertical barriers in Lake Ohrid for evolutionary events, to estimate the onset of intralacustrine diversification in this group based on molecular clock analyses, and to compare this data with data from other endemic species for providing an approximate time frame for the origin of Lake Ohrid. Based on the criteria speciosity, monophyly and endemicity, it can be concluded that Lake Ohrid Dina, indeed, represents an ancient lake species flock. Lineage sorting of its species, however, does not seem to be complete. Analyses of population structures of Dina spp. in the Ohrid watershed indicate a horizontal zonation of haplotypes from spring and lake populations, corroborating the role of lake-side springs, particularly the southern feeder springs, for evolutionary processes in endemic Ohrid taxa. Vertical differentiation of lake taxa, however, appears to be limited, though differences between populations from the littoral and the profundal are apparent. Molecular clock analyses indicate that the most recent common ancestor of extant species of this flock is approximately 1.99±0.83 Ma old, whereas the split of the Lake Ohrid Dina flock from a potential sister taxon outside the lake is estimated at 8.30±3.60 Ma. Comparisons with other groups of endemic Ohrid species indicated that in all cases, intralacustrine diversification started ?2 Ma ago. Thus, this estimate may provide information on a minimum age for the origin of Lake Ohrid. Maximum ages are less consistent and generally less reliable. But cautiously, a maximum age of 3 Ma is suggested. Interestingly, this time frame of approximately 2-3 Ma for the origin of Lake Ohrid, generated based solely on evolutionary data, well fits the time frame most often used in the literature by geologists. Future studies must show whether this concurrence holds true.

Trajanovski, S.; Albrecht, C.; Schreiber, K.; Schultheiß, R.; Stadler, T.; Benke, M.; Wilke, T.

2010-07-01

247

Jamming in Vertical Channels  

NASA Astrophysics Data System (ADS)

We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. Grain heights are less than their diameter so the grains resemble antacid tablets, coins, or poker chips. These grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by grain and channel sizes. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories.

Baxter, G. William; Steel, Fiona

2011-03-01

248

Jamming in Vertical Channels  

NASA Astrophysics Data System (ADS)

We experimentally study jamming of cylindrical grains in a vertical channel. The grains have a low aspect-ratio (height/diameter < 1) so their shape is like antacid tablets or poker chips. They are allowed to fall through a vertical channel with a square cross section. The channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. It is observed that grains sometimes jam in this apparatus. In a jam, grains form a stable structure from one side of the channel to the other with nothing beneath them. Jams may be strong enough to support additional grains above. The probability of a jam occurring is a function of the grain height and diameter. We will present experimental measurements of the jamming probability in this system and discuss the relationship of these results to other experiments and theories.

Baxter, G. William; McCausland, Jeffrey; Steel, Fiona

2010-03-01

249

Vertical axis wind turbine  

Microsoft Academic Search

A vertical axis wind turbine is provided based on the co-pending application ser. No. 890,998, filed Mar. 28, 1978, now U.S. Pat. No. 4,204,805. In this improved system the centrifugal forces of rotation produce no bending moments in the air foil spars. Also, the center of mass, the center of useful aerodynamic pressure and the center of main bearing supported

Bolie

1981-01-01

250

Hydrology and water quality of East Lake Tohopekaliga, Osceola County, Florida  

USGS Publications Warehouse

East Lake Tohopekaliga, one of the major lakes in central Florida, is located in the upper Kissimmee River basin in north-east Osceola County. It is one of numerous lakes in the upper basin used for flood control, in addition to recreation and some irrigation of surrounding pasture. This report is the fourth in a series of lake reconnaissance studies in the Kissimmee River basin prepared in cooperation with the South Florida Water Management District. The purpose of the report is to provide government agencies and the public with a brief summary of the lake 's hydrology and water quality. Site information is given and includes map number, site name, location, and type of data available (specific conductivity, pH, alkalinity, turbidity, color, dissolved oxygen, hardness, dissolved chlorides, dissolved sodium, dissolved calcium, dissolved magnesium, dissolved potassium, nitrogen, ammonia, nitrates, carbon and phosphorus). The U.S. Geological Survey (USGS) maintained a lake stage gaging station on East Lake Tohopekaliga from 1942 to 1968. The South Florida Water Management District has recorded lake stage since 1963. Periodic water quality samples have been collected from the lake by the South Florida Water Management District and USGS. Water quality and discharge data have been collected for one major tributary to the lake, Boggy Creek. Although few groundwater data are available for the study area, results of previous studies of the groundwater resources of Osceola County are included in this report. To supplement the water quality data for East Lake Tohopekaliga, water samples were collected at selected sites in November 1982 (dry season) and in August 1983 (rainy season). Samples were taken at inflow points, and in the lake, and vertical profiles of dissolved oxygen and temperature were measured in the lake. A water budget from an EPA report on the lake is also included. (Lantz-PTT)

Schiffer, Donna M.

1987-01-01

251

Lessons from a Lake.  

ERIC Educational Resources Information Center

|Describes a study that included classroom lessons on hydroelectric power, the history and construction of a nearby lake, data recording, the use of field guides, and methods of counting natural populations. The study culminated in a field trip to the lake. (JRH)|

Goethals, Susan

1997-01-01

252

Conservation of salt lakes  

Microsoft Academic Search

Salt lakes have a variety of important uses and values, including especially both economic and scientific ones. These uses and values have been and are increasingly subject to degradation from a variety of impacts: diversion of inflows, pollution, agricultural practices, and introduction of exotic species are among the more important. Recognition of these impacts upon salt lakes has led to

W. D. Williams

1993-01-01

253

Great Lakes Teacher's Guide.  

ERIC Educational Resources Information Center

|The Great Lakes are one of the world's greatest reservoirs of fresh water, the foundation of Ontario's economic development, a primary force in ecological systems, and a base for pleasure and recreation. They are also a magnificent resource for the teachers of Ontario. Study of the Great Lakes can bring to life the factors that shape the ecology…

Reid, Ron

254

Evaporation From Lake Superior  

NASA Astrophysics Data System (ADS)

Evaporation is a critical component of the water balance of each of the Laurentian Great Lakes, and understanding the magnitude and physical controls of evaporative water losses are important for several reasons. Recently, low water levels in Lakes Superior and Michigan/Huron have had socioeconomic, ecological, and even meteorological impacts (e.g. water quality and quantity, transportation, invasive species, recreation, etc.). The recent low water levels may be due to increased evaporation, but this is not known as operational evaporation estimates are currently calculated as the residual of water or heat budgets. Perhaps surprisingly, almost nothing is known about evaporation dynamics from Lake Superior and few direct measurements of evaporation have been made from any of the Laurentian Great Lakes. This research is the first to attempt to directly measure evaporation from Lake Superior by deploying eddy covariance instrumentation. Results of evaporation rates, their patterns and controlling mechanisms will be presented. The direct measurements of evaporation are used with concurrent satellite and climate model data to extrapolate evaporation measurements across the entire lake. This knowledge could improve predictions of how climate change may impact the lake's water budget and subsequently how the water in the lake is managed.

Spence, C.; Blanken, P.; Hedstrom, N.; Leshkevich, G.; Fortin, V.; Charpentier, D.; Haywood, H.

2009-05-01

255

Lake Nyos Dam  

Microsoft Academic Search

Lake Nyos, or to be more precise, the upper 38 m of Lake Nyos, is held back by a natural dam (Figure 1) which, if it were to fail, would wreak havoc in the valleys to the north and cause a serious flood to surge down the Katsina Ala into Nigeria. Lockwood et al., [1987], who have been investigating the

S. J. Freeth

1988-01-01

256

The Great Lakes.  

ERIC Educational Resources Information Center

|The Great Lakes are one of the world's greatest reserviors of fresh water, the foundation of Ontario's economic development, a primary force in ecological systems, and a base for pleasure and recreation. These lakes and their relationship with people of Canada and the United States can be useful as a subject for teaching the impact of human…

Seasons, 1987

1987-01-01

257

Great Lakes: chemical monitoring  

Microsoft Academic Search

The article discusses a symposium sponsored by the 10th Great Lakes Regional Meeting of the American Chemical Society (ACS) that addressed various aspects of the theme ''Chemistry of the Great Lakes''. The symposium attempted to gather together environmental information produced by chemists, and included: watershed studies, involving investigation of the sources, transport, and fate of sterols in the Menomonee River;

Joseph J. Delfino

1976-01-01

258

Great Lakes: Great Gardening.  

ERIC Educational Resources Information Center

|This folder contains 12 fact sheets designed to improve the quality of gardens near the Great Lakes. The titles are: (1) "Your Garden and the Great Lakes"; (2) "Organic Gardening"; (3) "Fruit and Vegetable Gardening"; (4) "Composting Yard Wastes"; (5) "Herbicides and Water Quality"; (6) "Watering"; (7) "Soil Erosion by Water"; (8) "Soil…

New York Sea Grant Inst., Albany, NY.

259

Hydrologic setting of Williams Lake, Hubbard County, Minnesota  

USGS Publications Warehouse

The hydrology and geology of Williams Lake watershed was studied to evaluate the accuracy of various methods used to determine precipitation and evaporation in lake water-balance studies and to define a lake and ground-water system according to approaches suggested by theoretical modeling studies. Regression analysis between estimated and measured precipitation at the lake showed that the accuracy of regionalization techniques is dependent on the closeness of the data network to the lake. For individual storms, the average-value method was found to be better than either the weighted average or isohyetal methods of determining precipitation, but it was least accurate in estimating 14-day average precipitation. The amount of evaporation calculated by the mass-transfer method ranged from 2 to 7 inches per month from July to October 1978, depending on the method used to determine the mass-transfer coefficient. Test drilling indicated that 30 to 150 feet of sand and gravel overlies till in the Williams Lake watershed. A sand lens about 50 feet thick occurs within the till. The configuration of the water table and vertical-head gradients measured from July to December 1978 indicate that ground water moves into the lake from the south and east and moves from the lake into the ground-water reservoir to the west. Preliminary numerical models indicate that the sand lens within the till is effectively isolated from the flow system interacting with the lake and that both inseepage and outseepage were about 1.4 inches from mid-July to mid-October 1978. When estimated as a residual in a water balance, ground water showed a net outseepage only of 1.47 inches. (USGS)

Siegel, Donald I.; Winter, Thomas C.

1980-01-01

260

Vertical-migration patterns of flagellates in a community of freshwater benthic algae  

Microsoft Academic Search

The population densities of sediment-inhabiting flagellates sampled from a shallow eutrophic lake in April 1986 were investigated at intervals of 1 or 1.5 h over a twenty hour period in the laboratory under natural irradiance and in controlled conditions. In natural irradiance the flagellates exhibited a vertical migration rhythm up onto the sediment surface after dawn and down into the

Christine M. Happey-Wood

1988-01-01

261

Lake circulation and sediment transport in Lake Myvatn  

Microsoft Academic Search

Lake circulation and sediment transport in Lake Myvatn have been calculated using AQUASEA, a numerical model developed by Vatnaskil Consulting Engineers. The goal of the modelling was to calculate changes in sediment transport within the lake due to changes in lake bathymetry caused by diatomite mining. The model uses the Galerkin finite element method and consists of a hydrodynamic flow

Snorri Páll Kjaran; Sigurdur Lárus Hólm; Eric Matthew Myer

2004-01-01

262

Spatial patterns in PCB concentrations of Lake Michigan lake trout  

USGS Publications Warehouse

Most of the PCB body burden in lake trout (Salvelinus namaycush) of the Great Lakes is from their food. PCB concentrations were determined in lake trout from three different locations in Lake Michigan during 1994-1995, and lake trout diets were analyzed at all three locations. The PCB concentrations were also determined in alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), bloater (Coregonus hoyi), slimy sculpin (Cottus cognatus), and deepwater sculpin (Myoxocephalus thompsoni), five species of prey fish eaten by lake trout in Lake Michigan, at three nearshore sites in the lake. Despite the lack of significant differences in the PCB concentrations of alewife, rainbow smelt, bloater, slimy sculpin, and deepwater sculpin from the southeastern nearshore site near Saugatuck (Michigan) compared with the corresponding PCB concentrations from the northwestern nearshore site near Sturgeon Bay (Wisconsin), PCB concentrations in lake trout at Saugatuck were significantly higher than those at Sturgeon Bay. The difference in the lake trout PCB concentrations between Saugatuck and Sturgeon Bay could be explained by diet differences. The diet of lake trout at Saugatuck was more concentrated in PCBs than the diet of Sturgeon Bay lake trout, and therefore lake trout at Saugatuck were more contaminated in PCBs that Sturgeon Bay lake trout. These findings were useful in interpreting the long-term monitoring series for contaminants in lake trout at both Saugatuck and the Wisconsin side of the lake.

Madenjian, Charles P.; DeSorcie, Timothy J.; Stedman, Ralph M.; Brown, Edward H., Jr.; Eck, Gary W.; Schmidt, Larry J.; Hesselberg, Robert J.; Chernyak, Sergei M.; Passino-Reader, Dora R.

1999-01-01

263

Lake Trout Rehabilitation in Lake Erie: A Case History  

Microsoft Academic Search

Native lake trout (Salvelinus namaycush) once thrived in the deep waters of eastern Lake Erie. The impact of nearly 70 years of unregulated exploitation and over 100 years of progressively severe cultural eutrophication resulted in the elimination of lake trout stocks by 1950. Early attempts to restore lake trout by stocking were unsuccessful in establishing a self-sustaining population. In the

Floyd C. Cornelius; Kenneth M. Muth; Roger Kenyon

1995-01-01

264

Lava Lake Filling, Draining, and Density-Driven Crustal Foundering: Kilauea Iki 1959  

NASA Astrophysics Data System (ADS)

The 1959 eruption of Kilauea formed an approximately 46x106 m3 lava lake during 17 episodes of Hawaiian fountaining. The vent location, on the steep walls of the Kilauea Iki pit crater, resulted in interplay between fountaining, pit filling and drain back from the lake into the vent. Previous studies of the Kilauea Iki lava lake have highlighted the post-eruption cooling and crystallization history, but little has been published regarding the processes of lake growth. The lava lake margins preserve features associated with filling, drainage and density-driven crustal foundering during the final eruptive episodes. Features associated with lake filling include relics of numerous vertically accreted layers preserved at the lake margins. The thickness of these onion-skin-like layers relates to variations in lake depth, the length of time a certain level was maintained, and cooling of the lake lava against the crater wall. Horizontal lava shelves are the relics of crusts formed as a result of surficial cooling during periods when the lake remained stable at a particular height for a period of time. Morphology, thickness, spacing and vertical placement of these shelves relate to the length of time a particular level was maintained, lava accretion style, as well as drainage velocity and cooling rates. Shelves were formed in both static environments (where crust standing in a fixed location thickened with time) and dynamic environments (where crust rolling along the lake edge accreted to the wall in a snow-ball-like fashion). Complete crustal overturn was observed repeatedly during the eruption and is a common process in all lava lakes, yet the initiating occurrence of crustal foundering is rarely preserved in situ. The northern margin of the 1959 lake reveals plates of lava plunging into the lake core and permits a detailed interpretation of the mechanics involved in crustal foundering during lake drainback. Density differences between (1) a lava lake crustal plate and (2) overriding and underlying material are several hundred kg/m3. These differences are substantial and lead to inevitable foundering of lake crust and eventually to complete crustal overturn.

Stovall, W. K.; Houghton, B. F.; Harris, A.; Swanson, D. A.

2007-12-01

265

Evidence of offshore lake trout reproduction in Lake Huron  

USGS Publications Warehouse

Six Fathom Bank-Yankee Reef, an offshore reef complex, was an historically important spawning area believed to represent some of the best habitat for the rehabilitation of lake trout Salvelinus namaycush in Lake Huron. Since 1986, lake trout have been stocked on these offshore reefs to reestablish self-sustaining populations. We sampled with beam trawls to determine the abundance of naturally reproduced age-0 lake trout on these offshore reefs during May-July in 1994-1998 and 2000-2002. In total, 123 naturally reproduced lake trout fry were caught at Six Fathom Bank, and 2 naturally reproduced lake trout fry were caught at nearby Yankee Reef. Our findings suggest that this region of Lake Huron contains suitable habitat for lake trout spawning and offers hope that lake trout rehabilitation can be achieved in the main basin of Lake Huron.

DeSorcie, Timothy J.; Bowen, Charles A., II

2003-01-01

266

Eutrophication factors in north central Florida lakes  

Microsoft Academic Search

Nutrient loading rates were estimated for Anderson-Cue Lake in Florida. The lake was artificially spiked with phosphorus. Nutrient budgets for the lake and other lakes were compared. Nutrient sources and sinks for lakes were identified. A partial nutrient budget for Anderson-Cue lake was prepared, and the chemical composition of the lake's water was compared to rainwater. 5 tables.

P. L. Brezonik; W. H. Morgan; E. E. Shannon; H. D. Putnam

1969-01-01

267

Modulation of the Earthquake Cycle at the Southern San Andreas Fault by Lake Loading  

NASA Astrophysics Data System (ADS)

Changes in the presence of Ancient Lake Cahuilla over the last 1500 years in the Salton Trough alter the state of stress by varying the pore pressure magnitude within the crust and by bending the lithosphere in response to the applied lake load. The recurrence interval of the lake is similar to the recurrence interval of rupture on the southern San Andreas and San Jacinto faults, both of which are partially covered by the lake at its highstand. Furthermore, four of the last five ruptures on the southern San Andreas fault have occurred near a time of substantial lake level change. We investigate the effect of Coulomb stress perturbations on local faults due to the changing level of Lake Cahuilla to determine a possible role in the timing of fault rupture. Vertical lake loading response and Coulomb stress is calculated with a 3-D semi-analytic model of an elastic plate overlying a viscoelastic half-space. Plate thickness and half-space relaxation time are adjusted to match observed vertical deformation since the last lake highstand. We find that the lake cycle induces Coulomb stress perturbations of 0.2 - 0.6 MPa on the southern San Andreas within the lake boundary, and 0.1 - 0.2 MPa on the southern San Andreas outside the lake boundary. These Coulomb stress perturbations are comparable to stress magnitudes known to have triggered events on other faults along the North American- Pacific plate boundary and represent 2 30 years of advance or delay of a southern San Andreas event.

Luttrell, K.; Sandwell, D.; Smith-Konter, B.; Bills, B.; Bock, Y.

2006-12-01

268

Depth profiles of temperature, specific conductance and oxygen concentration in Lake Powell, Arizona-Utah, 1992-95  

USGS Publications Warehouse

The depth distribution of temperature in lakes and reservoirs establishes vertical-density gradients that regulate the distribution of a wide array of chemical and biological features. In Lake Powell, the depth at which inflowing river water enters the reservoir is controlled by the water temperature of the river compared to the vertical-thermal structure of the reservoir in late spring and early summer. The measurements reported here document the longitudinal and vertical pattern of temperature, specific conductance, and oxygen concentration on several dates in 1992, 1994, and 1995.

Marzolf, G. Richard; Hart, Robert J.; Stephens, Doyle W.

1998-01-01

269

A comparison of lakes in the Kolyma River region that receive inputs of Holocene and Pleistocene origin  

NASA Astrophysics Data System (ADS)

The Siberian Arctic contains vast amounts of carbon stored in permafrost soils. Throughout this region there are many lakes and rivers that receive input of organic matter from terrestrial sources. Previous research suggests that these freshwater ecosystems are actively processing carbon, rather than functioning only as passive transporters. Ongoing climate warming in this vulnerable region is expected to cause increasing permafrost thaw and a likely increase of the inflow of permafrost-derived carbon to freshwater ecosystems. We aim to improve our understanding of how these freshwater ecosystems are processing carbon to increase our ability to predict how climate change will affect this region. This study was performed in July 2011 as part of the Polaris Project (www.polarisproject.org). We focused upon lakes in the Kolyma River watershed, the world's largest river underlain by continuous permafrost. These lakes receive inputs of allochthonous material from either Holocene (floodplain lakes) or Pleistocene (yedoma lakes) soils. We sampled a range of lakes (floodplain n=3; yedoma n=3) for DOC concentration and lability, by means of biological oxygen demand assays, in combination with N and P measurements and water column profiles (oxygen concentrations, pH, specific conductivity and temperature). Chlorophyll a concentrations were measured as a comparison of autochthonous production between lakes. Our findings indicate that yedoma lakes are generally stratified but also display a high variability in their vertical structure over relatively short time scales (the fieldwork took place over three weeks). Furthermore, floodplain lakes had more than twice the concentration of chlorophyll a in the surface water as yedoma lakes, suggesting more autotrophic production. Yedoma lakes contained approximately 40% more DOC than floodplain lakes in surface waters. However, the lability of yedoma lake DOC was half that of floodplain lakes. The higher concentrations of DOC within yedoma lakes may therefore be driven by the more refractory nature of the organic matter pool within these lakes.

Henriksen, E. H.; Vonk, J. E.; Schade, J. D.; Mann, P. J.; Bulygina, E. B.; Sobczak, W. V.; Zimov, S. A.; Holmes, R. M.

2011-12-01

270

The vertical distribution of phytoplankton in stratified water columns.  

PubMed

What determines the vertical distribution of phytoplankton in different aquatic environments remains an open question. To address this question, we develop a model to explore how phytoplankton respond through growth and movement to opposing resource gradients and different mixing conditions. We assume stratification creates a well-mixed surface layer on top of a poorly mixed deep layer and nutrients are supplied from multiple depth-dependent sources. Intraspecific competition leads to a unique strategic equilibrium for phytoplankton, which allows us to classify the distinct vertical distributions that can exist. Biomass can occur as a benthic layer (BL), a deep chlorophyll maximum (DCM), or in the mixed layer (ML), or as a combination of BL+ML or DCM+ML. The ML biomass can be limited by nutrients, light, or both. We predict how the vertical distribution, relative resource limitation, and biomass of phytoplankton will change across environmental gradients. We parameterized our model to represent potentially light and phosphorus limited freshwater lakes, but the model is applicable to a broad range of vertically stratified systems. Increasing nutrient input from the sediments or to the mixed layer increases light limitation, shifts phytoplankton towards the surface, and increases total biomass. Increasing background light attenuation increases light limitation, shifts the phytoplankton towards the surface, and generally decreases total biomass. Increasing mixed layer depth increases, decreases, or has no effect on light limitation and total biomass. Our model is able to replicate the diverse vertical distributions observed in nature and explain what underlying mechanisms drive these distributions. PMID:20932846

Mellard, Jarad P; Yoshiyama, Kohei; Litchman, Elena; Klausmeier, Christopher A

2011-01-21

271

The influence of spatial wind inhomogeneity on flow patterns in a small lake  

Microsoft Academic Search

A two-dimensional vertically averaged flow model was applied to study the circulation patterns in Lake Belau (Northern Germany). The lake is north–south oriented, with a maximum extension of 2.2km and is situated in a dead ice hole with steep slopes on the east and west coasts. A part of the coastal area is covered with forest, creating a strong shelter

Victor Podsetchine; Gerald Schernewski

1999-01-01

272

Optical characteristics of shallow lakes from the Pampa and Patagonia regions of Argentina  

Microsoft Academic Search

Sixteen Argentinean shallow lakes from the Pampa plains and the Patagonian steppe were characterized using optical properties and water-quality parameters. In this set of lakes a wide range in water transparency descriptors was observed (broadband vertical attenuation coefficient (kd PAR) varied from 0.40 to 47 m ? 1 , Secchi disk depth (Sd) from 0.07 to 12.00 m, and nephelometric

Gonzalo L. Perez; Ana Torremorell; Roberto Escaray; Patricia Perez; Maria Dieguez; Horacio Zagarese

2009-01-01

273

Optical characteristics of shallow lakes from the Pampa and Patagonia regions of Argentina  

Microsoft Academic Search

Sixteen Argentinean shallow lakes from the Pampa plains and the Patagonian steppe were characterized using optical properties and water-quality parameters. In this set of lakes a wide range in water transparency descriptors was observed [broadband vertical attenuation coefficient (kd PAR) varied from 0.40 to 47m?1, Secchi disk depth (Sd) from 0.07 to 12.00m, and nephelometric turbidity (tn) from 0.50 to

Gonzalo L. Pérez; Ana Torremorell; José Bustingorry; Roberto Escaray; Patricia Pérez; Maria Diéguez; Horacio Zagarese

2010-01-01

274

Diel variations of selected physico-chemical parameters in Lake Kissimmee, Florida  

Microsoft Academic Search

Every two months, diel depth profiles were made of dissolved oxygen, pH, temperature and conductivity at two stations in Lake Kissimmee, Florida, from July 1974 through June 1975. Results suggest that stratification does not occur in the large (137 km2), shallow (mean depth 2.5 m) lake, though steep vertical gradients in these parameters may develop. The data also suggest that

Craig W. Dye; Douglas A. Jones; Landon T. Ross; Jennifer L. Gernert

1980-01-01

275

Yellowstone lake nanoarchaeota.  

PubMed

Considerable Nanoarchaeota novelty and diversity were encountered in Yellowstone Lake, Yellowstone National Park (YNP), where sampling targeted lake floor hydrothermal vent fluids, streamers and sediments associated with these vents, and in planktonic photic zones in three different regions of the lake. Significant homonucleotide repeats (HR) were observed in pyrosequence reads and in near full-length Sanger sequences, averaging 112 HR per 1349 bp clone and could confound diversity estimates derived from pyrosequencing, resulting in false nucleotide insertions or deletions (indels). However, Sanger sequencing of two different sets of PCR clones (110 bp, 1349 bp) demonstrated that at least some of these indels are real. The majority of the Nanoarchaeota PCR amplicons were vent associated; however, curiously, one relatively small Nanoarchaeota OTU (71 pyrosequencing reads) was only found in photic zone water samples obtained from a region of the lake furthest removed from the hydrothermal regions of the lake. Extensive pyrosequencing failed to demonstrate the presence of an Ignicoccus lineage in this lake, suggesting the Nanoarchaeota in this environment are associated with novel Archaea hosts. Defined phylogroups based on near full-length PCR clones document the significant Nanoarchaeota 16S rRNA gene diversity in this lake and firmly establish a terrestrial clade distinct from the marine Nanoarcheota as well as from other geographical locations. PMID:24062731

Clingenpeel, Scott; Kan, Jinjun; Macur, Richard E; Woyke, Tanja; Lovalvo, Dave; Varley, John; Inskeep, William P; Nealson, Kenneth; McDermott, Timothy R

2013-09-11

276

Yellowstone Lake Nanoarchaeota  

PubMed Central

Considerable Nanoarchaeota novelty and diversity were encountered in Yellowstone Lake, Yellowstone National Park (YNP), where sampling targeted lake floor hydrothermal vent fluids, streamers and sediments associated with these vents, and in planktonic photic zones in three different regions of the lake. Significant homonucleotide repeats (HR) were observed in pyrosequence reads and in near full-length Sanger sequences, averaging 112 HR per 1349 bp clone and could confound diversity estimates derived from pyrosequencing, resulting in false nucleotide insertions or deletions (indels). However, Sanger sequencing of two different sets of PCR clones (110 bp, 1349 bp) demonstrated that at least some of these indels are real. The majority of the Nanoarchaeota PCR amplicons were vent associated; however, curiously, one relatively small Nanoarchaeota OTU (71 pyrosequencing reads) was only found in photic zone water samples obtained from a region of the lake furthest removed from the hydrothermal regions of the lake. Extensive pyrosequencing failed to demonstrate the presence of an Ignicoccus lineage in this lake, suggesting the Nanoarchaeota in this environment are associated with novel Archaea hosts. Defined phylogroups based on near full-length PCR clones document the significant Nanoarchaeota 16S rRNA gene diversity in this lake and firmly establish a terrestrial clade distinct from the marine Nanoarcheota as well as from other geographical locations.

Clingenpeel, Scott; Kan, Jinjun; Macur, Richard E.; Woyke, Tanja; Lovalvo, Dave; Varley, John; Inskeep, William P.; Nealson, Kenneth; McDermott, Timothy R.

2013-01-01

277

Vertically moored platform anchoring  

SciTech Connect

An improved system is disclosed for anchoring a floating vessel which is anchored only by parallel and essentially vertical conduits. The anchoring load is carried by units of concentric pipes including an outer riser pipe and inner strings of casing. Drilling wells and/or production of oil and gas or like operations are conducted through these casings. The tension of the inner casing string is transmitted to the floating vessel through the upper end of the outer riser pipe. The system prevents excessive buildup of stresses in the upper end of the inner casing due to the bending caused by excursions caused by the waves, the wind and the current.

Blenkarn, K.A.; Beynet, P.A.

1984-02-14

278

Studying climate impacts on hydrophysical processes in Lake Constance by 3D hydrodynamic modelling  

NASA Astrophysics Data System (ADS)

A 3D hydrodynamic model was applied to investigate the implications of a change in climatic conditions for the hydrophysical behaviour of deep Upper Lake Constance. The model simulations covered the period from 1960 to 2011. Model adaptation and verification was based on 51 years of vertically resolved temperature recordings. Three different horizontal grid layouts were employed to test the sensitivity of the model to spatial grid resolution. Effective vertical turbulent diffusivities Kz in the stratified lake below 10 m were determined from simulation results and from vertically highly resolved CTD probe data over 16 years using the heat budget method. The Kz obtained from the simulated and measured water temperatures agreed rather well and ranged in the order of 10-5 to 10-4 m2s-1. In the deep water, where the lake basin is resolved only by few grid cells, the diffusivity values were overestimated by the model, whereby the deviation from the measurement data based estimates decreased with increasing grid resolution. The open water turbulent diffusivities in the model are substantially smaller than the basin wide effective diffusivities supporting that vertical transport in a stratified lake is largely dominated by turbulent mixing near the lake boundaries. The model was finally applied to investigate the impact of changed wind velocities and air temperatures on deep water renewal which is a key process for the vertical transport of nutrients and oxygen in deep Lake Constance. Numerical tracers were employed as indicators of the vertical transport and mixing of water. Increased air temperatures not only resulted in an overall increase in water temperatures but also in a change of the mixing dynamics. Deep-water renewal was most sensitive to changes in air temperatures during the winter season. Variations in wind velocity influenced water temperatures and mixing via changes in latent and sensible heat fluxes as well as by changes in the energy flux to turbulent motions.

Wahl, Bernd; Peeters, Frank

2013-04-01

279

Torsional nystagmus during vertical pursuit.  

PubMed

We examined three patients with cavernous angioma within the middle cerebellar peduncle. Each patient had an unusual ocular motor finding: the appearance of a strong torsional nystagmus during vertical pursuit. The uncalled-for torsion changed direction when vertical pursuit changed direction. In one patient, we recorded eye movements with the magnetic field technique using a combined direction and torsion eye coil. The slow-phase velocity of the inappropriate torsional nystagmus was linearly related to the slow-phase velocity of vertical smooth pursuit, and changed direction when vertical pursuit changed direction. This torsional nystagmus also appeared during fixation suppression of the vertical vestibulo-ocular reflex (VOR), but was minimal during vertical head rotation when fixing a stationary target in the light. We suggest that inappropriately directed eye movements during pursuit might be another ocular motor sign of cerebellar dysfunction. Furthermore, we speculate that the signals used for vertical smooth pursuit are, at some stage, encoded in a semicircular canal VOR coordinate framework. To illustrate, for the vertical semicircular canals, vertical and torsional motion are combined on the same cells, with the anterior semicircular canals mediating upward movements and the posterior semicircular canals mediating downward movements. For the right labyrinth, however, both vertical semicircular canals produce clockwise slow phases (ipsilateral eye intorts, contralateral eye extorts). The opposite is true for the vertical semicircular canals in the left labyrinth; counterclockwise slow phases are produced. Hence, to generate a pure vertical VOR, the anterior or posterior semicircular canals on both sides of the head must be excited so that opposite-directed torsional components cancel. Thus, if pursuit were organized in a way similar to the VOR, pure vertical pursuit would require that oppositely-directed torsional components cancel in normals. If this did not happen, a residual torsional nystagmus could appear during attempted vertical pursuit. PMID:8797162

FitzGibbon, E J; Calvert, P C; Dieterich, M; Brandt, T; Zee, D S

1996-06-01

280

Understanding Sediment Dynamics in a Shallow, Hypereutrophic Lake within the Middle St. Johns River: Lake Jesup, FL  

NASA Astrophysics Data System (ADS)

Improved knowledge of sediment dynamics within a lake system is important for understanding lake water quality. This research was focused on an assessment of the vertical sediment flux in Lake Jesup, a shallow (1.3 m average depth) hypereutrophic lake of central Florida. Sediment dynamics were assessed at varying time scales (daily to weekly) to understand the transport of sediments from external forces; wind, waves, precipitation and/or runoff. Four stations were selected within the lake based on water depth and the thicknesses of unconsolidated (floc) and consolidated sediments. At each of these stations, a 10:1 high aspect ratio trap (STHA) was deployed to collect particulate matter for a one to two week period. The water and sediment samples were collected and analyzed for total carbon (TC), total phosphorus (TP) and total nitrogen (TN). Mass accumulation rates (MAR) collected by the traps varied from 77 to 418 g m-2 d-1 over seven deployments. TN, TP and TC sediment concentrations collected by the traps were consistently higher than the sediments collected by coring the lake bottom and is most likely associated with water column biomass.

Nielsen, S.; Anderson, W. T.; Corbett, D. R.; Fugate, D. C.; Scinto, L. J.; Thomas, S.; Brandt-Williams, S.

2011-12-01

281

33 CFR 162.130 - Connecting waters from Lake Huron to Lake Erie; general rules.  

Code of Federal Regulations, 2010 CFR

...from Lake Huron to Lake Erie; general rules. (a) Purpose. The regulations in...connecting Lake Huron to Lake Erie (including the River Rouge) to prevent...navigation channels at the head of Lake Erie. District...

2009-07-01

282

33 CFR 162.130 - Connecting waters from Lake Huron to Lake Erie; general rules.  

Code of Federal Regulations, 2010 CFR

...from Lake Huron to Lake Erie; general rules. (a) Purpose. The regulations in...connecting Lake Huron to Lake Erie (including the River Rouge) to prevent...navigation channels at the head of Lake Erie. District...

2010-07-01

283

SIGNIFICANCE OF REGIONAL LAKE QUALITY PATTERNS TO MANAGEMENT/RESTORATION OF SPECIFIC LAKES  

EPA Science Inventory

Understanding regional lake quality patterns is important to lake management and restoration. t puts specific lake conditions into perspective, provides basis for establishing lake quality goals, assists identification of lakes most likely to benefit from protection and restorati...

284

Glacial Isostatic Adjustment in the Great Lakes Region Inferred by Tide Gauges and Satellite Altimetry  

NASA Astrophysics Data System (ADS)

Glacial isostatic adjustment (GIA) of the solid Earth due to deglaciation since the last Ice Age is characterized by its viscous rebound as a result of relaxation of the shear stresses inside the Earth. GIA uplift (in the form of 3-D crustal motion and the ensuing geoid change due to redistribution of mass in the solid Earth) has been recently measured with long-term GPS (e.g., the BIFROST project). In this paper, we used more than 50 long-term (1860-2000) water level gauges located around the Great Lakes, and satellite altimetry measurements (TOPEX/ POSEIDON and Geosat, 9-15 year data span) to measure the vertical motion of the region. Preliminary results indicate that Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, are uplifting at a rate of 1.8, 0.9, 1.4, -0.5, and 1.0 mm/yr, respectively. The uncertainty of the measurement is primarily due to the error in satellite altimetry due to its relatively short data span. The results are compared with available GIA models, including ICE-4G, and Mitrovica-Milne 2001 models, as well as relative vertical motion measured using water level gauges [Manville et al., 2001]. Analysis also includes the examination of GIA models using different estimates of mantle thickness and upper and lower mantle viscosity. Results using the vertical measurement in an inverse geophysical solution will be reported.

Shum, C.; Kuo, C.; Mitrovica, J. X.

2002-05-01

285

A performance evaluation of Canada's Snipe Lake/Beaverhill Lake A pool  

SciTech Connect

This paper describes the evaluation of the production performance of the Snipe Lake/Beaverhill Lake A (BHL-A) pool. The purpose of this investigation was to determine the reasons behind the pool's low projected recovery (32%) relative to similar pools (40%) and to recommend steps to remove the causes. This work was initiated because the pool's production is declining under the existing depletion scheme (essentially a downdip waterflood). The evaluation involved simultaneous geological and engineering investigations that improved the quality of data interpretation and the timeliness of the effort and reduced the overlap of work that otherwise might have occurred. The detailed reservoir model developed indicated that the production performance is controlled by the pool's geology. Fluid movement is restricted vertically between reservoir cycles and horizontally within the major reservoir cycle.

Springate, G. (Exxon Exploration Co. (United States)); Muir, I.D. (Esso Resources Canada Ltd (Canada)); Caldwell, T.R. (OMV Canada Ltd. (Canada))

1992-11-01

286

Sediment processes and mercury transport in a frozen freshwater fluvial lake (Lake St. Louis, QC, Canada).  

PubMed

An open-bottom and a closed-bottom mesocosm were developed to investigate the release of mercury from sediments to the water column in a frozen freshwater lake. The mesoscosms were deployed in a hole in the ice and particulate mercury (Hg(P)) and total dissolved mercury (TDHg) were measured in sediments and in water column vertical profiles. In addition, dissolved gaseous mercury (DGM) in water and mercury water/airflux were quantified. Concentrations of TDHg, DGM, and mercury flux were all higher in the open-bottom mesocosm than in the closed-bottom mesocosm. In this paper we focus on the molecular diffusion of mercury from the sediment in comparison with the TDHg accumulation in the water column. We conclude that the molecular diffusion and sediment resuspension play a minor role in mercury release from sediments suggesting that solute release during ebullition is an important transport process for mercury in the lake. PMID:19117652

Canário, João; Poissant, Laurier; O'Driscoll, Nelson; Vale, Carlos; Pilote, Martin; Lean, David

2008-12-30

287

Lake Hoare, Antarctica: sedimentation through a thick perennial ice cover.  

PubMed

Lake Hoare in the Dry Valleys of Antarctica is covered with a perennial ice cover more than 3 m thick, yet there is a complex record of sedimentation and of growth of microbial mats on the lake bottom. Rough topography on the ice covering the lake surface traps sand that is transported by the wind. In late summer, vertical conduits form by melting and fracturing, making the ice permeable to both liquid water and gases. Cross-sections of the ice cover show that sand is able to penetrate into and apparently through it by descending through these conduits. This is the primary sedimentation mechanism in the lake. Sediment traps retrieved from the lake bottom indicate that rates of deposition can vary by large amounts over lateral scales as small as 1 m. This conclusion is supported by cores taken in a 3 x 3 grid with a spacing of 1.5 m. Despite the close spacing of the cores, the poor stratigraphic correlation that is observed indicates substantial lateral variability in sedimentation rate. Apparently, sand descends into the lake from discrete, highly localized sources in the ice that may in some cases deposit a large amount of sand into the lake in a very short time. In some locations on the lake bottom, distinctive sand mounds have been formed by this process. They are primary sedimentary structures and appear unique to the perennially ice-covered lacustrine environment. In some locations they are tens of centimetres high and gently rounded with stable slopes; in others they reach approximately 1 m in height and have a conical shape with slopes at angle of repose. A simple formation model suggests that these differences can be explained by local variations in water depth and sedimentation rate. Rapid colonization of fresh sand surfaces by microbial mats composed of cyanobacteria, eukaryotic algae, and heterotrophic bacteria produces a complex intercalation of organic and sandy layers that are a distinctive form of modern stromatolites. PMID:11538650

Squyres, S W; Andersen, D W; Nedell, S S; Wharton, R A

1991-01-01

288

Great Lakes Water Quality.  

National Technical Information Service (NTIS)

The report provides an assessment of the present water quality of the Great Lakes and their connecting channels and critically examines the data collection and analysis programs available for this evaluation. The status of remedial programs being implemen...

1974-01-01

289

Great Lakes Water Quality.  

National Technical Information Service (NTIS)

The report is the first Annual Report of the International Joint Commission pursuant to the Great Lakes Water Quality Agreement between the United States and Canada signed April 15, 1972. The Commission's report takes cognizance of significant development...

1972-01-01

290

The Lake Erie Inquiry.  

ERIC Educational Resources Information Center

|Describes experiences, or "lab puzzles," which will help students develop problem-solving skills in a laboratory setting. Outlines procedures for developing techniques, setting boundaries, and finding the number of molecules of water in Lake Erie. (RT)|

Wherley, James M.

1989-01-01

291

Limnology of Lake Champlain.  

National Technical Information Service (NTIS)

This report presents an exhaustive compilation of existing physical, chemical, and biological data on Lake Champlain. As a reference document, the report assembles both published and unpublished information. Data presentation is through text tables, illus...

G. E. Myer G. K. Gruendling

1979-01-01

292

Limnology of Lake Minnetonka.  

National Technical Information Service (NTIS)

Fluctuations of population densities of phytoplankton in 4 basins of Lake Minnetonka in Minnesota were inferred from changes of concentrations of chlorophyll a and particulate organic carbon during the ice-fee season. Concentrations of chlorophyll a durin...

R. O. Megard

1974-01-01

293

Mormon Lake Cliffs.  

National Technical Information Service (NTIS)

An establishment of a scientific or educational natural area on the east side of Mormon Lake has been proposed. The area supports an unusual floral assemblage and may be important to vertebrates (especially migrating songbirds) as well. The cliffs include...

E. L. Smith G. L. Bender

1973-01-01

294

Hydrodynamic mesoscale modeling of atmospheric transport and pollutant deposition in the vicinity of a lake  

SciTech Connect

This study identifies two meteorological situations common to lakeshore environments, where pollutants can be vertically redistributed resulting in concentration and deposition fields, different from these expected for homogeneous surfaces. In order to study the effects of lakes on pollutant deposition, a hydrodynamic model was developed which included terms for pollutant transport, dispersion and deposition. The modeling domain was centered around (Lake Michigan) to investigate the potential impact of nearby industrial sources. The model is capable of forecasting the local wind, temperature, and pressure patterns as well as evolution of the atmospheric planetary boundary layer parameters. It was found that the presence of a lake in the summertime limits pollutant deposition over its length, due to stabilization and plum entrainment in the lake-breeze. Also the mean height of the resultant plume was predicted to be higher with the influence of a lake-breeze than without. In the other hand, deposition was enhanced over the upwind land due to the lake-breeze effect, and the downwind shore due to enhanced mixing. In the wintertime, the presence of a warm lake caused deposition near the upwind lakeshore greater than predicted without the lake. These limited applications illustrate that dry deposition around a source located by a large lake may be significantly different from that expected around a source located in simple terrain.

Christidis, Z.D.

1986-01-01

295

Observation of picometer vertical emittance with a vertical undulator.  

PubMed

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic. PMID:23215388

Wootton, K P; Boland, M J; Dowd, R; Tan, Y-R E; Cowie, B C C; Papaphilippou, Y; Taylor, G N; Rassool, R P

2012-11-08

296

Observation of Picometer Vertical Emittance with a Vertical Undulator  

NASA Astrophysics Data System (ADS)

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

Wootton, K. P.; Boland, M. J.; Dowd, R.; Tan, Y.-R. E.; Cowie, B. C. C.; Papaphilippou, Y.; Taylor, G. N.; Rassool, R. P.

2012-11-01

297

Temporal and Spatial Patterns in Thermokarst Lake Area Change in Yukon Flats, Alaska: an Indication of Permafrost Degradation  

NASA Astrophysics Data System (ADS)

The formation, expansion, and drainage of thermokarst lakes is determined by the lateral and vertical degradation of permafrost. Consequently, areal changes in thermokarst lakes can reflect changes in the spatial distribution and depth of permafrost. However, natural variability in lake areas confounds the long term trend and makes it difficult to detect permafrost degradation by simply comparing lake areas from different time periods. In this study, we used Landsat images of 16 time periods between 1984 and 2009 to extract lake area (closed basin lakes only) for a 422,382 ha study area within Yukon Flats, Alaska. A multiple linear regression model was built to quantify the long term change in lake area. In this model, we included LWB (local water balance, defined as difference between total precipitation and total potential evapotranspiration since the preceding October), MDT (mean daily temperature from May 1st to the date that Landsat image was acquired) and PRD (four time periods: 1984-1986, 1992, 1999-2002, and 2009). MDT was used to indicate the active layer depth. Both LWB and MDT were used to account for natural variability in lake area. The model explained 95% of the total variability in lake area, with 62%, 16% and 17% accounted for by LWB, MDT and PRD respectively. Using the total lake area (15898 ha) in 1984-1986 as a baseline, lake area increased by 12% in 1992, and decreased by 6% during 1999-2002 and 8% in 2009. Among the 1,667 lakes, 267 lakes showed an area decrease and 115 lakes showed an increase. The expanding lakes were distributed along the Yukon River and its main tributaries (Beaver creek and Birch creek), while the shrinking lakes were located farther away from rivers or on fluvial terraces. A potential reason for the spatial pattern of expanding and shrinking lakes is that, after permafrost thaws, lakes can become connected to the groundwater system. Lakes close to the rivers may be recharged by groundwater due to their lower position relative to groundwater table, while lakes farther away from rivers drain to the subsurface due to their higher position. This study provides a rigorous method to quantify long term change in thermokarst lake area and the regression model can be used in earth system models to make better predictions of thermokarst lake areas.

Chen, M.; Rowland, J. C.; Wilson, C. J.; Altmann, G.; Brumby, S. P.

2011-12-01

298

Anomalous rainfall and associated atmospheric circulation in the northeast Spanish Mediterranean area and its relationship to sediment fluidization events in a lake  

Microsoft Academic Search

Changes in the dynamics of sediment transport in a Mediterranean lake (sediment fluidization events) are linked to atmospheric circulations patterns (trough monthly precipitation). In the basins of Lake Banyoles, located in the northeast of Spain, water enters mainly through subterranean springs, and associated fluctuations in the vertical migration of sediment distribution (fluidization events) present episodic behavior as a result of

Marianna Soler; Teresa Serra; Jordi Colomer; Romualdo Romero

2007-01-01

299

Great Lakes literacy principles  

Microsoft Academic Search

Lakes Superior, Huron, Michigan, Ontario, and Erie together form North America's Great Lakes, a region that contains 20% of the world's fresh surface water and is home to roughly one quarter of the U.S. population (Figure 1). Supporting a $4 billion sport fishing industry, plus $16 billion annually in boating, 1.5 million U.S. jobs, and $62 billion in annual wages

Rosanne W. Fortner; Lyndsey Manzo

2011-01-01

300

Diagnostic analysis of water circulations in Lake Biwa  

Microsoft Academic Search

A diagnostic model is developed for the study of steady water-circulations during summer in Lake Biwa. The most characteristic feature of the present model is to include the vertical friction terms in the basic equations, so that it is not necessary to assume a level of no-motion. Under no-wind condition, the velocity field is calculated from the density field obtained

Shuichi Endoh

1978-01-01

301

Identification and Characterization of Dynamic Alpine Subglacial Lakes Using InSAR, Radio- Echo Sounding, and Crevasse Interpretation  

NASA Astrophysics Data System (ADS)

We use interferometric synthetic aperture radar (InSAR), radio-echo sounding (RES), and crevasse interpretation to identify and characterize two dynamic alpine subglacial lakes in Glacier Bay National Park, Alaska. Although significant literature exists on large subglacial lakes in Antarctica, little research has been done on alpine subglacial lakes. Subglacial and subaerial glacier-dammed lakes and the catastrophic floods (jokulhlaups) that release are a hazard in glacierized mountain regions around the world. Many glacier-dammed lakes form subglacially during periods of glacier retreat and downwasting, but are not identified until they become subaerially exposed or release a jokulhlaup. The two lakes discussed here are dammed by Brady Glacier in southeast Alaska, 120 km west of Juneau. Initially, a conspicuous, 3-km-long crevasse in the glacier drew our attention to Hinge Lake, so named because of its hinge-like appearance. For the InSAR analysis, we utilized 20 ascending and descending ERS-1 and -2 tandem radar images provided by the European Space Agency. We obtained a DEM from Glacier Bay National Park that was based on data from the SRTM mission, with gaps filled using photogrammetry data. We co-registered and processed raw SAR signal data into complex, single-look images, created interferograms, and unwrapped the phase. To simplify the analysis, we assumed zero horizontal glacier movement. This assumption is valid because ice is flowing into a closed depression and all interferograms analyzed in this study show very little or zero horizontal motion. To further characterize the lakes, we conducted a RES survey to determine ice depths and substrate. We deduced principle stresses by interpreting crevasses patterns in combination with vertical displacement data derived from interferograms. A time series of interferograms shows vertical motion over large areas of the two lakes. A hydraulic connection between the two lakes is inferred from contemporaneous vertical displacement of the overlying ice. The RES survey provided minimum depths of floating ice. We explain crevasse patterns using a two-fold stress field caused by simple downslope ice movement and vertical displacement of the overlying ice due to filling and draining of the lakes. This study demonstrates that a combination of InSAR, RES, and glaciological interpretation can effectively identify and characterize alpine subglacial lakes. Knowledge of these lakes is important for understanding glacier motion, outburst flood potential and routing, and glacier mass balance. This research is a component of a dissertation that seeks to identify and characterize the glacier-dammed lakes of Glacier Bay, Denali, and Wrangell - St. Elias National Parks using ground-truthed radar and optical remote sensing techniques. It is our aim to eventually apply these techniques to glacier-dammed lakes worldwide.

Capps, D. L.; Rabus, B. T.; Clague, J. J.

2007-12-01

302

TOXAPHENE STUDY OF GREAT LAKES TRIBUTARY SEDIMENTS  

EPA Science Inventory

The Product is the paper "Pulp and Paper Mills as Sources of Toxaphene to Lake Superior and Northern Lake Michigan" published in the Journal of Great Lakes Research, 25(2):383-394 International Association of Great Lakes 1999....

303

Vertical Cable Seismic Survey for Hydrothermal Deposit  

NASA Astrophysics Data System (ADS)

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques. We have carried out two field surveys in FY2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, the VCS will become a practical exploration tool for the exploration of seafloor hydrothermal deposits.

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2012-04-01

304

Availability of lake trout reproductive habitat in the Great Lakes  

USGS Publications Warehouse

A decades-long program to reestablish self-sustaining stocks of lake trout (Salvelinus namaycush) in the four lower Great Lakes produced excellent fisheries supported by stocked fish. These fish spawned widely and small numbers of their offspring were collected intermittently from Lakes Michigan, Huron, and Ontario, but no self-sustaining stocks were established. Irt this paper we address habitat sufficiency as a factor in the failure of stocked lake trout to established self-sustaining populations in the four lower Great Lakes. We present the previously unpublished results of lake trout spawning habitat surveys conducted at seven sites in the Great Lakes since 1987 and we compare them with the published results of similar surveys conducted at 24 other sites in the four lower lakes since 1981. Our evaluation indicates all but two of these sites can support the production of viable fry from spawnings by the shallow-water strains of lake trout that are stocked in the Great Lakes. However, some of the best spawning, egg, and fry habitat in the lower Great Lakes seems to be at deeper offshore sites that may be unattractive to these shallow-water strains. Thus, we suggest also stocking the lower four lakes with strains from Lake Superior that might more fully exploit the best spawning habitat at these deeper, offshore sites.

Edsall, Thomas A.; Kennedy, Gregory W.

1995-01-01

305

Dynamics of geckos running vertically  

Microsoft Academic Search

Geckos with adhesive toe pads rapidly climb even smooth vertical surfaces. We challenged geckos (Hemidactylus garnotii) to climb up a smooth vertical track that contained a force platform. Geckos climbed vertically at up to 77·cm·s -1 with a stride frequency of 15·Hz using a trotting gait. During each step, whole body fore-aft, lateral and normal forces all decreased to zero

K. Autumn; S. T. Hsieh; D. M. Dudek; J. Chen; C. Chitaphan; R. J. Full

2006-01-01

306

Coupled resonator vertical cavity laser  

SciTech Connect

The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

1998-01-01

307

30.VERTIGO AND VERTICALITY IN  

Microsoft Academic Search

The vertical dimension is crucial to Super Monkey Ball on all levels1, and invites us to meditate on vertigo and verticality, falling and failing in the construc- tion of space and game-play in this game and in comput- er-games as such. In Super Monkey Ball, the vertical dimension should be mastered (landing on tiny islands with the ball glider), avoided

Troels Degn Johansson

308

The Simulation of Heavy Lake-Effect Snowstorms across the Great Lakes Basin in the RegCM4 Regional Climate Model  

NASA Astrophysics Data System (ADS)

Heavy lake-effect snowstorms (LES) cause severe societal impacts in the U.S.-Canadian Great Lakes region, but the response of these extreme events to recent and future warming trends is uncertain. In this study we employ a regional climate model (ICTP RegCM4) at 20-km resolution to simulate LES over this domain, with a particular interest in heavy snowfalls. When coupled to an interactive lake model and driven with atmospheric reanalysis data, RegCM4 is able to reproduce major characteristics of LES with reasonable accuracy, including total seasonal snowfall, lake ice cover, and occasional strong snowfall events. The model also realistically simulates the observed interannual variability of lake ice and its decline during the late 20th century (1977-2002). The timing and location of heavy LES are in general agreement with observations, but the magnitude of the snowfalls is usually undersimulated. To investigate the role of lake ice cover on heavy LES, we conduct a set of case studies in which the simulation of an observed event is compared with a companion simulation that has 100% ice concentration imposed on one or all of the Great Lakes. This collection of experiments quantifies the impact of ice cover from a particular lake on downstream snowfall and demonstrates that Lake Superior has the most widespread influence on heavy snowfall in the basin and Lakes Erie and Ontario the least. We find that the amount of ice cover strongly affects a wide range of atmospheric variables during heavy LES, including temperature, precipitable water, clouds, air pressure, and vertical motion. An interesting meteorological consequence is a weakening of lower tropospheric winds over the lakes when they are completely iced over, suggesting a secondary mechanism by which the presence of open water can enhance downstream snowfall.

Vavrus, S. J.; Notaro, M.; Zarrin, A.

2011-12-01

309

Rapid Warming of the World's Lakes: A Global Assessment of Recent Lake Temperature Trends Using In Situ and Satellite-Based Records  

NASA Astrophysics Data System (ADS)

Recent studies have revealed significant warming of lakes throughout the world, and the observed rate of lake warming is - in many cases - more rapid than that of the ambient air temperature. These large changes in lake temperature have profound implications for lake hydrodynamics, productivity, and biotic communities. The scientific community is just beginning to understand the global extent, regional patterns, physical mechanisms, and ecological consequences of lake warming. Although many in situ lake temperature records are available, only a few encompass long time periods. Most datasets are collected by individual investigators, have varying sampling protocols, and do not have extensive geographic or temporal coverage. Remote sensing methods, on the other hand, have been increasingly used to characterize global trends in lake surface temperature, and they provide an invaluable counterpart to in situ measurements. However, the existing satellite records do not extend as far back in time as some of the longer in situ datasets, and remotely sensed measurements capture only surface temperature, rather than vertical profiles. In this study, we present initial results from an international collaborative effort to synthesize global records of lake temperature from in situ and satellite-based measurements. Surface water temperature data are analyzed from over 120 lakes distributed across 40 countries. Data from 20 of the lakes are based on in situ measurements, while the remaining 100+ lake temperature records are obtained from satellite-based methods. We focus primarily on mean summer water temperatures for the 25-year period 1985-2009, as this provides a common time period with the largest amount of available data. Linear regression analysis reveals that 65% of the lakes in the database are experiencing significant summertime warming (p < 0.1), with another 30% warming at a rate that is not statistically significant. Only 5% of the lakes in the database show cooling trends (none of which are significant). The in situ and satellite-based measurements show a very similar distribution of water temperature trends among lakes, with a mean value of approximately +0.5 °C/decade and standard deviation of +/-0.3 °C/decade (maximum = +1.0 °C/decade). We also examine a variety of external controlling factors (e.g., air temperature, solar radiation, latitude, and lake depth) to understand the physical mechanisms associated with the global and regional patterns of lake warming.

Lenters, J. D.; Adrian, R.; Allan, M.; de Eyto, E.; Hamilton, D. P.; Hook, S.; Izmestyeva, L.; Kraemer, B.; Kratz, T.; Livingstone, D.; Mcintyre, P.; Montz, P.; Noges, P.; Noges, T.; O'Reilly, C.; Read, J.; Sandilands, K.; Schindler, D.; Schneider, P.; Silow, E.; Straile, D.; Van Cleave, K.; Zhdanov, F.

2011-12-01

310

Contaminants in American alligator eggs from Lake Apopka, Lake Griffin, and Lake Okeechobee, Florida  

USGS Publications Warehouse

Residues of organochlorine pesticides, polychlorinated biphenyls (PCBs), and 16 elements were measured in American alligator (Alligator mississippiensis) eggs collected in 1984 from Lakes Apopka, Griffin, and Okeechobee in central and south Florida. Organochlorine pesticides were highest in eggs from Lake Apopka. None of the elements appeared to be present at harmful concentrations in eggs from any of the lakes. A larger sample of eggs was collected in 1985, but only from Lakes Griffin, a lake where eggs were relatively clean, and Apopka, where eggs were most contaminated. In 1985, hatching success of artificially incubated eggs was lower for Lake Apopka, and several organochlorine pesticides were higher than in eggs from Lake Griffin. However, within Lake Apopka, higher levels of pesticides in chemically analyzed eggs were not associated with reduced hatching success of the remaining eggs in the clutch. Therefore, it did not appear that any of the pesticides we measured were responsible for the reduced hatching of Lake Apopka eggs.

Heinz, G.H.; Percival, H.F.; Jennings, M.L.

1991-01-01

311

Evidence of Lake Trout reproduction at Lake Michigan's mid-lake reef complex  

USGS Publications Warehouse

The Mid-Lake Reef Complex (MLRC), a large area of deep (> 40 m) reefs, was a major site where indigenous lake trout (Salvelinus namaycush) in Lake Michigan aggregated during spawning. As part of an effort to restore Lake Michigan's lake trout, which were extirpated in the 1950s, yearling lake trout have been released over the MLRC since the mid-1980s and fall gill net censuses began to show large numbers of lake trout in spawning condition beginning about 1999. We report the first evidence of viable egg deposition and successful lake trout fry production at these deep reefs. Because the area's existing bathymetry and habitat were too poorly known for a priori selection of sampling sites, we used hydroacoustics to locate concentrations of large fish in the fall; fish were congregating around slopes and ridges. Subsequent observations via unmanned submersible confirmed the large, fish to be lake trout. Our technological objectives were driven by biological objectives of locating where lake trout spawn, where lake trout fry were produced, and what fishes ate lake trout eggs and fry. The unmanned submersibles were equipped with a suction sampler and electroshocker to sample eggs deposited on the reef, draw out and occasionally catch emergent fry and collect egg predators (slimy sculpin Cottus cognatus). We observed slimy sculpin to eat unusually high numbers of lake trout eggs. Our qualitative approaches are a first step toward quantitative assessments of the importance of lake trout spawning on the MLRC.

Janssen, J.; Jude, D. J.; Edsall, T. A.; Paddock, R. W.; Wattrus, N.; Toneys, M.; McKee, P.

2006-01-01

312

Monitoring crustal deformation in The Geysers-Clear Lake geothermal area, California  

Microsoft Academic Search

Geodetic surveys since 1972-1973 reveal significant crustal deformation in The Geysers-Clear Lake region. Resurveys of precise control networks are measuring both vertical and horizontal ground movement, with most of the change continuing in the area of geothermal fluid withdrawal. Preliminary evidence suggests right-lateral horizontal movement on northwest-trending fault systems and vertical and horizontal compression of the deep geothermal reservoir system.

Lofgren

1978-01-01

313

Accurate Linking of Lake Erie Water Level with Shoreline Datum Using GPS Buoy and Satellite Altimetry  

Microsoft Academic Search

There is a need to accurately link the water level to the shoreline vertical datum for various applications including coastal management, lake\\/river\\/estuary\\/wetland hydrological or storm surge modeling\\/forecasting. Coastal topography is historically surveyed and referenced to the predetermined vertical datum in terms of orthometric heights, or the heights above the geoid, which is poorly known in terms of accuracy and lack

Kai-Chien Cheng; Chung-Yen Kuo; C. K. Shum; Xutong Niu; Rongxing Li; Keith W. Bedford

2008-01-01

314

Simulating climate change impacts on lake stratification on a continental scale  

NASA Astrophysics Data System (ADS)

Lake stratification is to a large extent determined by regional climatic conditions. Changes in climate patterns like increasing air temperature or wind speed will lead to a shift in lake characteristics, thus changing the physical basis for live in the aquatic system. A vertical one-dimensional hydrodynamic model supported by a simple ice cover model is used to simulate abiotic lake characteristics like thermocline depth, timings of the start and end of stratification, ice break-up dates, as well as biological characteristics linked to the physical environment like the timing of maximum Daphnia abundance. To account for hydrodynamic differences due to lake morphometry and trophic state, we use several model lakes differing in depth (from 5 m to 100 m) and light absorption coefficients (0.3 1/m for oligotrophic lakes to 2.4 1/m for eutrophic lakes), respectively. The model lakes are forced by mean meteorological data for the years 1961-1990 as well as for future climate scenarios prescribed on a 0.5 degree grid over Europe. This results in several tens of thousands of simulations of lake temperatures and turbulent diffusivities over several annual cycles, from which we extract cardinal events and values such as the onset of stratification, length of stratification period, thermocline depth or ice cover duration. Using the reference meteorological conditions our simulations describe differences in lake hydrodynamics and ecology, e.g. start of the algal spring bloom, length of the algal growing period, across latitudinal, longitudinal and altitudinal gradients. It also allows for the quantification of changes in lake characteristics due to climate change, e.g. increasing periods of stratification or earlier ice break up. This large scale simulation approach reveals physical and biological lake characteristics over a wide geographic range in Western Europe. It serves as a baseline for a comparative plankton ecology by setting up a physical frame to allow for cross regional comparison of plankton succession.

Joehnk, Klaus; Straile, Dietmar

2013-04-01

315

Quantifying methane ebullition in thermokarst lakes with space borne synthetic aperture radar (SAR)  

NASA Astrophysics Data System (ADS)

Northern high latitude wetlands and thermokarst lakes in permafrost regions have been identified as strong sources for methane (CH4), a powerful greenhouse gas. Quantifying the spatial distribution and magnitude of CH4 sources in these regions has become increasingly important in the current scenario of global warming and amidst concerns of partial release of the large permafrost soil carbon pool through thawing by thermokarst lakes. Ebullition (bubbling) is an important mode of CH4 emission from thermokarst lakes to the atmosphere. However, due to its sporadic behavior, large uncertainties remain in estimating the magnitude of ebullition emissions from lakes. Synthetic Aperture Radar (SAR) remote sensing of lake ice is a potentially valuable tool to constrain bottom-up estimates of lake ebullition in regions where lake ice forms. Here we explored various SAR imaging parameters as they correlate to field measurements of CH4 ebullition bubbles in the ice of ten thermokarst lakes on the northern Seward Peninsula, Alaska. We found that ebullition bubbles trapped in frozen lakes were strongly correlated with L-band single polarized horizontal (HH) SAR (R2 = 0.70, P = 0.002) and with the 'roughness' component of a classic Pauli decomposition of PALSAR L-band quad-polarized signal (R2 = 0.77, P = 0.001). We found no such correlation with ERS-2 C-band single polarized vertical (VV) SAR. We present the results of our single-pol and quad-pol SAR geospatial analysis, a discussion of probable scattering mechanisms of ebullition bubbles in frozen thermokarst lakes and our recommendation for the optimal season for SAR observation. Our results indicate that calibrated L-band SAR could be a valuable tool for estimating methane ebullition in lakes on a regional scale by evaluating the backscatter intensity from early winter lake ice.

Engram, M. J.; Walter Anthony, K.; Meyer, F. J.; Grosse, G.

2011-12-01

316

4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe (VTL). Machining the fixture for GE Turboshroud. G.S. O'Brien, operator. - Juniata Shops, Machine Shop No. 1, East of Fourth Avenue at Third Street, Altoona, Blair County, PA

317

Satellite view of Swim Lake and nearby lakes.  

USGS Multimedia Gallery

Satellite view of Swim Lake (upper right) and nearby lakes in Polk County, Florida, surrounded by citrus groves. Courtesy Florida State University, 2008; Southwest Florida Water Management District, 2008....

2009-06-12

318

Hydrogeologic Controls on Lake Level at Mountain Lake, Virginia  

NASA Astrophysics Data System (ADS)

Mountain Lake in Giles County, Virginia has a documented history of severe natural lake-level changes involving groundwater seepage that extend over the past 4200 years. Featured in the 1986 movie Dirty Dancing, the natural lake dried up completely in September 2008 and levels have not yet recovered. A hydrogeologic investigation was undertaken in an effort to determine the factors influencing lake level changes. A daily water balance, dipole-dipole electrical resistivity surveying, well logging and chemical sampling have shed light on: 1) the influence of a fault not previously discussed in literature regarding the lake, 2) the seasonal response to precipitation of a forested first-order drainage system in fractured rock, and 3) the possibility of flow pathways related to karst features. Geologic controls on lake level were investigated using several techniques. Geophysical surveys using dipole-dipole resistivity located possible subsurface flowpaths both to and from the lake. Well logs, lineament analysis, and joint sampling were used to assess structural controls on lake hydrology. Major ions were sampled at wells, springs, streams, and the lake to evaluate possible mixing of different sources of water in the lake. Groundwater levels were monitored for correlation to lake levels, rainfall events, and possible seismic effects. The hydrology of the lake was quantified with a water balance on a daily time step. Results from the water balance indicate steady net drainage and significant recharge when vegetation is dormant, particularly during rain-on-snow melt events. The resistivity survey reveals discrete areas that represent flow pathways from the lake, as well as flowpaths to springs upgradient of the lake located in the vicinity of the fault. The survey also suggests that some flowpaths may originate outside of the topographic watershed of the lake. Chemical evidence indicates karst may underlie the lakebed. Historical data suggest that artificial intervention to mitigate seepage would be required for lake level recovery in the near future.

Roningen, J. M.; Burbey, T. J.

2011-12-01

319

Sensitivity of Lake-Enhanced Snowfall to Lake Ice Cover in the Great Lakes Region  

NASA Astrophysics Data System (ADS)

The Great Lakes exert a significant influence on the regional climate of northern United States and southern Canada, including enhancement of cold-season precipitation on and downwind of the leeward shores. Lake-enhanced snowfall occurs when air that is significantly colder than the lake's surface temperature travels over the lake. Enhanced surface sensible and latent heat fluxes relative to the surrounding land surface result in moistening and destabilization of the atmosphere and subsequent development of low-level convection. In the Great Lakes region, lake-enhanced snow occurs during late fall through early winter, with decreasing numbers of events in the late winter due to the formation of widespread lake ice. Lake ice reduces both sensible and latent heat fluxes from the surface, thereby increasing atmospheric stability and reducing lake induced convection. The degree to which ice coverage may change in future climate scenarios is largely unknown, but it is clear that any change to the fraction and duration of lake ice coverage will have an effect on lake-atmosphere interaction and the development and intensity of lake-enhanced precipitation. This study uses the NCAR Weather, Research, and Forecasting (WRF) model to examine how changes in Great Lakes fractional ice coverage affect the presence, intensity, and quantity of lake-enhanced precipitation. Sensitivity studies are used to evaluate the evolution and change in intensity of lake-enhanced snowfall in the Great Lakes region for scenarios that include (1) lake ice cover obtained from analysis fields (control simulation), (2) ice-free lakes, and (3) 100% ice coverage. Distinct lake-effect snow bands were observed in both the control and ice-free simulations, with placement of these bands further to the south and propagating further inland in the ice-free case. Melted precipitation totals increased on the order of 10 mm for ice-free lakes along the southern edges of Lake Superior, Lake Erie, and the eastern coast of Lake Ontario, while complete ice coverage extinguished nearly all lake-effect snow bands.

Wright, D. M.; Posselt, D. J.; Steiner, A. L.

2011-12-01

320

42. Peaks of Otter, Abbott Lake. View across lake to ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

42. Peaks of Otter, Abbott Lake. View across lake to peaks of Outter Lodge, completed in 1964. Construction of the lake got underway in 1964. Looking east-northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

321

Biogeochemical silica mass balances in Lake Michigan and Lake Superior  

Microsoft Academic Search

Silica budgets for Lake Michigan and Lake Superior differ in several respects. Mass balance calculations for both lakes agree with previous studies in that permanent burial of biogenic silica in sediments may be only about 5% of the biogenic silica produced by diatoms. Because dissolution rates are large, good estimates of permanent burial of diatoms can not be obtained indirectly

Claire L. Schelske

1985-01-01

322

Socioeconomic Aspects of Lake Trout Rehabilitation in the Great Lakes  

Microsoft Academic Search

During the 1940s and 1950s, the major fisheries for lake trout Salvelinus namaycush in the Great Lakes declined precipitously because of predation by sea lampreys Petromyzon marinus and overfishing. The need to control the sea lamprey and rehabilitate lake trout resulted in the establishment of institutional arrangements among the responsible state, provincial, and federal fishery agencies. The early arrangements were

Randy L. Eshenroder

1987-01-01

323

Phytoplankton periodicity in a subtropical lake (Lake Kinneret, Israel)  

Microsoft Academic Search

Lake kinneret is a subtropical monomictic lake characterized by a Pyrrhophyta-Chlorophyta assemblage, supplemented by Cyanophyta in some years. Concerning their abundance and seasonal occurrence, the phytoplanktonic algae belong to two groups: algae appearing in quantity at a definite annual period and algae present throughout the year. Four stages of algal succession occur in the lake. There is a marked periodicity

Utsa Pollingher

1986-01-01

324

Swan Lake Restoration. Phase 1.  

National Technical Information Service (NTIS)

Shallowness, siltation/sedimentation, low water levels, and dense algal blooms in Swan Lake, Iowa have dropped oxygen concentrations below levels that can support fish. The recommendations are: lake deepening (dredging), reduction of shallow areas, expans...

R. Bachmann B. Lohnes D. Bonneau

1982-01-01

325

Great Lakes Monthly Hydrologic Data.  

National Technical Information Service (NTIS)

This report summarizes the monthly hydrologic data currently used by the Great Lakes Environmental Research Laboratory in their hydrologic and water resource studies of the Great Lakes. The data consist of precipitation, runoff, evaporation, connecting ch...

F. H. Quinn R. N. Kelley

1983-01-01

326

Functions and Vertical Line Test  

NSDL National Science Digital Library

This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.

2010-01-01

327

The anterior vertical SMAS lift  

Microsoft Academic Search

With minimal skin and SMAS undermining, as well as a rotation point that is closest to the nasolabial folds and jowls, the “anterior vertical SMAS lift” reduces the risk of hematoma while optimizing direct pull on those surface features that require improvement. The vertical rotation enhances the malar region and decreases preauricular skin excision. Further, the author has found this

Robert W. Bernard

2003-01-01

328

Fast vertical mining using diffsets  

Microsoft Academic Search

A number of vertical mining algorithms have been proposed recently for association mining, which have shown to be very effective and usually outperform horizontal approaches. The main advantage of the vertical format is support for fast frequency counting via intersection operations on transaction ids (tids) and automatic pruning of irrelevant data. The main problem with these approaches is when intermediate

Mohammed Javeed Zaki; Karam Gouda

2003-01-01

329

Emotional sounds influence vertical vection.  

PubMed

While viewing a large vertically moving sinusoidal luminance grating, the perception of upward self-motion (vection) was modulated by positive sounds (e.g., a baby's laughter). This may be because positive emotion and the spatial metaphor of vertical directions were unified in the mind. PMID:23155739

Sasaki, Kyoshiro; Seno, Takeharu; Yamada, Yuki; Miura, Kayo

2012-01-01

330

Mono Lake Excursion Reviewed  

NASA Astrophysics Data System (ADS)

The Mono Lake Excursion as recorded in the Mono Basin, CA, has an older part that is about negative 30 degrees inclination and about 300 degrees declination during low relative field intensity. Those paleomagnetic directions are closely followed by greater than 80 degrees positive inclination and east declination of about 100 degrees during higher relative field intensity. A path of the Virtual Geomagnetic Poles (VGPs) for the older part followed from old to young forms a large clockwise loop that reaches 35 degrees N latitude and is centered at about 35 degrees E longitude. That loop is followed by a smaller one that is counterclockwise and centered at about 70 degrees N latitude and 270 degrees E longitude (Denham & Cox, 1971; Denham, 1974; Liddicoat & Coe, 1979). The Mono Lake Excursion outside the Mono Basin in western North America is recorded as nearly the full excursion at Summer Lake, OR (Negrini et al., 1984), and as the younger portion of steep positive inclination/east declination in the Lahontan Basin, NV. The overall relative field intensity during the Mono Lake Excursion in the Lahontan Basin mirrors very closely the relative field intensity in the Mono Basin (Liddicoat, 1992, 1996; Coe & Liddicoat, 1994). Using 14C and 40Ar/39Ar dates (Kent et al., 2002) and paleoclimate and relative paleointensity records (Zimmerman et al., 2006) for the Mono Lake Excursion in the Mono Basin, it has been proposed that the Mono Lake Excursion might be older than originally believed and instead be the Laschamp Excursion at about 40,000 yrs B.P. (Guillou et al., 2004). On the contrary, we favor a younger age for the Mono Lake Excursion, about 32,000 yrs B.P., using the relative paleointensity in the Mono Basin and Lahontan Basin and 14C dates from the Lahontan Basin (Benson et al., 2002). The age of about 32,000 yrs B.P. is also in accord with the age (32,000- 34,000 yrs B.P.) reported by Channell (2006) for the Mono Lake Excursion at ODP Site 919 in the Irminger Basin in the North Atlantic Ocean, which contains as well an excursion lower in the core at about 40,000 yrs B.P. that he identifies as the Laschamp Excursion. The paths of VGPs for the Irminger Basin and the younger half of the Mono Lake Excursion in the Mono Basin are similar in that they are counterclockwise loops and nearly adjacent to each other, and quite different from the VGP path for the Laschamp Excursion.

Liddicoat, J. C.; Coe, R. S.

2007-05-01

331

Lake Nyos Dam  

NASA Astrophysics Data System (ADS)

Lake Nyos, or to be more precise, the upper 38 m of Lake Nyos, is held back by a natural dam (Figure 1) which, if it were to fail, would wreak havoc in the valleys to the north and cause a serious flood to surge down the Katsina Ala into Nigeria. Lockwood et al., [1987], who have been investigating the Lake Nyos gas disaster, which killed an estimated 1700 people in August 1986, presented a paper on the potential for disastrous failure of the Lake Nyos dam to the AGU Fall Meeting. Part of what they said was subsequently reported in New Scientist (December 10, 1987, p. 18). They have placed on record their view that the dam is only 400 years old and are reported to have stated that it is eroding away at the alarming rate of 1.5 m/yr. If their figures are correct, then surely the dam will fail within a decade or two at the most, and there is indeed cause for alarm and immediate action. However, teams from Cameroon, France, Italy, Japan , Switzerland, Britain, Nigeria, and Germany also visited Lake Nyos in the immediate aftermath of the gas disaster, and none of their reports have suggested that the dam is in itself an imminent threat.

Freeth, S. J.

332

33 CFR 162.220 - Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev.  

Code of Federal Regulations, 2010 CFR

...Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. 162.220...Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. (a) Lake...that portion of Lake Mohave (Colorado River) extending 4,500 feet...

2010-07-01

333

33 CFR 162.220 - Hoover Dam, Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev.  

Code of Federal Regulations, 2010 CFR

...Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. 162.220...Lake Mead, and Lake Mohave (Colorado River), Ariz.-Nev. (a) Lake...that portion of Lake Mohave (Colorado River) extending 4,500 feet...

2009-07-01

334

Living with the Great Lakes  

NSDL National Science Digital Library

This site was developed to assist students and educators with learning about the Great Lakes. The topics discussed include, grain size, langmuir circulation, longshore current, beach drift, river plumes, lake stratification, and waves. Lesson plans can be found on the following subjects: lake levels, sediments, stream flow, and water quality. Also included is a virtual flight along the Eastern Lake Michigan Shoreline which includes topo maps, 3D maps, and photos. A directory of related links is also available.

Videtich, Patricia

335

Great Lakes Region Sea Grant  

NSDL National Science Digital Library

Site dedicated to the Great Lakes Sea Grant program. Information on GLSG priorities and initiatives. Topics of increased importance to the Great Lakes include fisheries and invasive species. Links to sites featuring publications and photos of Great Lakes storms and seiches and wildlife.

336

Living With the Great Lakes  

NSDL National Science Digital Library

This site was developed to assist students and educators with learning about the Great Lakes. The links provide materials on basic earth science concepts, a set of lesson plans on the lakes, and other Great Lakes topics. Concepts covered include Langmuir circulation, longshore current and beach drift, sediments, stream flow, seasonal stratification and water quality.

337

Exploring Subglacial Antarctic Lake Environments  

Microsoft Academic Search

While subglacial lakes have been suspected, and speculated about, for more than 50 years, recent analyses of historical and new data have shown that liquid water environments are common beneath the vast Antarctic Ice Sheet. Airborne radar surveys have now documented more than 145 subglacial lakes, the largest being Lake Vostok located 4 km beneath the vast East Antarctic Ice

J. C. Priscu; M. C. Kennicutt III; R. E. Bell; S. A. Bulat; J. C. Ellis-Evans; V. V. Lukin; J.-R. Petit; R. D. Powell; M. J. Siegert; I. Tabacco

2005-01-01

338

Great Lakes: Great Decisions (A)  

Microsoft Academic Search

One of the few remaining producers of lead additives must decide whether to continue producing them for use abroad. Banned in the United States, lead additives were still legal in developing nations. Ellie Shannon, the division manager overseeing bromine production for the Indiana-based Great Lakes Chemical Corporation (Great Lakes), must advise Great Lakes' directors on whether the company should 1)

R. Freeman; Andrew Wicks; Patricia Werhane; Jenny Mead

339

Ecological study of Ghodaghodi lake  

Microsoft Academic Search

Wetlands comprise 5% of world's total land areas of Nepal. The present study Ghodaghodi Lake in the Far-West Nepal Terai manifested the physicochemical contamination in the lake. All the parameters were within the WHO guideline values except for Phosphate and Dissolved Oxygen. Water depth varies form 1-4 m. High phosphate level suggested that the lake is hypertrophic. Dissolved oxygen was

J. Diwakar; S Barjracharya; U. R. Yadav

2009-01-01

340

Lake-level frequency analysis for Devils Lake, North Dakota  

USGS Publications Warehouse

An annual lake-volume model and a statistical water mass-balance model were used to estimate future lake-level probabilities for Devils Lake. Comparison of the models indicates upper exceedance levels of the water mass-balance model increase much more rapidly than those of the annual lake-volume model. For simulation year 5, the 99-percent exceedance is 1,417.6 feet above sea level for the annual lake-volume model and 1,423.2 feet above sea level for the water mass-balance model.

Wiche, Gregg J.; Vecchia, Aldo V.

1996-01-01

341

Viruses in Antarctic lakes.  

PubMed

Water samples collected from four perennially ice-covered Antarctic lakes during the austral summer of 1996-1997 contained high densities of extracellular viruses. Many of these viruses were found to be morphologically similar to double-stranded DNA viruses that are known to infect algae and protozoa. These constitute the first observations of viruses in perennially ice-covered polar lakes. The abundance of planktonic viruses and data suggesting substantial production potential (relative to bacteria] secondary and photosynthetic primary production) indicate that viral lysis may be a major factor in the regulation of microbial populations in these extreme environments. Furthermore, we suggest that Antarctic lakes may be a reservoir of previously undescribed viruses that possess novel biological and biochemical characteristics. PMID:11543124

Kepner, R L; Wharton, R A; Suttle, C A

1998-11-01

342

Lake Tahoe Data Clearinghouse  

NSDL National Science Digital Library

Created and maintained by the U.S. Geological Survey (USGS) in partnership with federal, state, tribal, and local agencies and groups, this is a major gateway to information and data on Lake Tahoe and its basin. The primary goal of this clearinghouse is to facilitate the coordination of research, monitoring, and environmental management activities in the Lake Tahoe Basin, and to ensure the widest possible access to data and information resulting from such activities. Users have access to a wide range of data and GIS products. Examples include: high quality digital maps for the Lake Tahoe area (including Tahoe hydrography, roads, vegetation cover, forests, timber, soils), digital orthophoto quadrangles, and digital elevation models. Some of the data resides on the USGS server at the Western Mapping Center, Menlo Park, California. The bulk of the data and information, located in databases maintained by the partnering agencies, is accessible via hypertext links.

Evans, Alexander

343

Lake Mead Shrinks!  

NSDL National Science Digital Library

Lake Mead reservoir is nestled between Arizona and Nevada and runs up to the Hoover Dam. The reservoir stores Colorado River water and supplies it to farms, homes and business in Southern Nevada, Arizona, southern California and northern Mexico. Scientists at NASA are releasing dramatic pictures of the dwindling water supplies in the drought-stricken western United States. According to the Bureau of Reclamation, the Colorado Basin is in its fourth year of drought and computer models project water levels will go down another 15 to 20 feet (4.6 to 6.1 m) by next year. Despite low water levels, The National Park Service says there is still plenty of water for recreation. The Landsat 7 satellite captured images of Lake Mead May 2000, and May 2003. The 2003 image clearly shows a shrinking lake.

Snodgrass, Stuart; Newcombe, Marte; Williams, Darrel

2003-07-22

344

Ice tectonics during the rapid tapping of a supraglacial lake on the Greenland Ice Sheet  

NASA Astrophysics Data System (ADS)

The hydraulic fracture of ice during the rapid tapping of supraglacial lakes is proposed as one mechanism to establish efficient surface-to-bed hydraulic pathways through kilometre-thick ice. This study presents detailed records of lake discharge, ice motion, and passive seismicity capturing the behaviour and processes preceding, during and following the rapid (~2 h) tapping of a large (~4 km2) supraglacial lake through 1.1 km of the western margin of the Greenland Ice Sheet. Peak discharge (3300 m3s-1) was coincident with maximal rates of horizontal displacement and vertical uplift, indicating that surface water accessed the ice-bed interface causing widespread hydraulic separation and enhanced basal motion. The differential motion of four GPS located around the lake, record the opening and closure of fractures suggesting that on short time-scales the brittle fracture of ice dominates ice flow. We hypothesise that during lake tapping, drainage occurred through a ~3 km long longitudinal fracture with a mean width of ~0.4 m. The perennial location of the supraglacial lake and the observed pattern of fracturing and surface uplift evince control by the local subglacial topography and the gradient of hydraulic potential. Our observations support the assertion that water-filled crevasses can propagate without longitudinal extension. The tapping of the lake coincided with the rapid drainage of a cluster of supraglacial lakes located within the same elevation band coincident with a notable and isolated peak in the catchment-wide, proglacial Watson River hydrograph.

Doyle, S. H.; Hubbard, A. L.; Dow, C. F.; Jones, G. A.; Fitzpatrick, A.; Gusmeroli, A.; Kulessa, B.; Lindback, K.; Pettersson, R.; Box, J. E.

2012-09-01

345

Evaluation of groundwater discharge into small lakes based on the temporal distribution of radon-222  

USGS Publications Warehouse

In order to evaluate groundwater discharge into small lakes we constructed a model that is based on the budget of 222Rn (radon t1/2 5 3.8 d) as a tracer. The main assumptions in our model are that the lake's waters are wellmixed horizontally and vertically; the only significant 222Rn source is via groundwater discharge; and the only losses are due to decay and atmospheric evasion. In order to evaluate the groundwater-derived 222Rn flux, we monitored the 222Rn concentration in lake water over periods long enough (usually 1-3 d) to observe changes likely caused by variations in atmospheric exchange (primarily a function of wind speed and temperature). We then attempt to reproduce the observed record by accounting for decay and atmospheric losses and by estimating the total 222Rn input flux using an iterative approach. Our methodology was tested in two lakes in central Florida: one of which is thought to have significant groundwater inputs (Lake Haines) and another that is known not to have any groundwater inflows but requires daily groundwater augmentation from a deep aquifer (Round Lake). Model results were consistent with independent seepage meter data at both Lake Haines (positive seepage of ??? 1.6 ?? 104 m3 d-1 in Mar 2008) and at Round Lake (no net groundwater seepage). ?? 2011, by the American Society of Limnology and Oceanography, Inc.

Dimova, N. T.; Burnett, W. C.

2011-01-01

346

Spatial and temporal variability of groundwater-surface water interactions along a lake shore  

NASA Astrophysics Data System (ADS)

Investigating the inflow dynamics of a groundwater dominated lake system is a major challenge as inflow is a) invisible to the eye and b) likely to be highly variable in space and possibly also in time. In this study the spatial and temporal variability of groundwater-surface water interactions along a lake shore is investigated by combining different experimental methods. Study area is Lake Hinnensee, situated 100 km north of Berlin in the TERENO Observatory of north-eastern Germany. The lake is a purely groundwater dominated with no surface inflows or outflows. The experimental approach includes the measurement of vertical hydraulic gradients along piezometer transects, spatial arrays of temperature profiles in the lake sediment and sediment surface temperature patterns investigated with fibre optic temperature sensing. We thus get an impression of both: spatial patterns as well as their temporal stability. This approach furthermore allows us to carry out a "cost-benefit" analysis for the different methodologies, comparing effort with scientific benefit. The results show that groundwater exfiltration into the lake is to some extent variable in time and it is highly variable in space: there is a strong gradient perpendicular to the lake shore as well as high heterogeneity along the lake shore.

Blume, T.; Krause, S.; Meinikmann, K.; Lewandowski, J.

2012-04-01

347

Mercury in lake sediments of the Precambrian Shield near Huntsville, Ontario, Canada  

USGS Publications Warehouse

Long sediment cores (> 1 m) were collected from eight Precambrian Shield lakes in southern Ontario, Canada and analyzed for mercury (Hg), loss-on-ignition (LOI), and a suite of 36 other elements. Results indicated at least 100-fold variation in sediment Hg concentrations between lakes in close proximity (from 450 ppb), comparable to the variation reported for lakes across the whole of Canada. Strong areal correlations between Hg concentrations and LOI (r2=0.77), between Hg and other trace element concentrations (Pb, Zn, Cd, Sb, As, Br), and similarities in the vertical concentration profiles of Hg and LOI, all point to the importance of organic matter in the release, transport and redistribution of metals in watershed systems. The spatial pattern of Hg concentrations in deep, precolonial sediments (>20 cm) was found to mirror the pattern of Hg concentrations in modern surface sediments, an observation that was confirmed in a follow-up survey (r2= 0.85; n = 25 lakes), indicating that natural processes govern the unequal distribution of Hg among these lakes. Between-lake differences in surface sediment Hg concentrations normalized to organic carbon (Hg/C) were also reflected by Hg concentrations in small-mouth bass normalized to 35 cm length (R2=0.63; n= 15 lakes). The latter relationship suggests that small-mouth bass and lake sediment indicators provide mutually supportive information regarding Hg loading to the lacustrine environment from geological sources in the watershed system.

Rasmussen, P. E.; Villard, D. J.; Fortescue, J. A. C.; Gardner, H. D.; Schiff, S. L.; Shilts, W. W.

1998-01-01

348

Remote sensing approach for hydrologic assessments of complex lake systems  

NASA Astrophysics Data System (ADS)

Lake studies play an important role in understanding water management, ecology, climatology, etc. because most of earth processes are strongly related to water dynamics. Because the studies have only used on-site gage readings, it is almost impossible to access individual lakes and to evaluate regional scale hydrology as a whole system. Especially in the Prairie Pothole Region (PPR) of North America has millions of potholes and lakes. Measuring lake levels in this region is one of the critical issues in hydrology or other related sciences and applications. The remote sensing approach with the Geographic Information System (GIS) technique could be used to overcome the difficulty associated with on-site measurements. In this study, the SRTM data was used as a main topographic dataset because the dataset provides accurate and consistent elevation data on a worldwide basis. The first chapter introduced the whole idea of this study. In the second chapter, the elevation values of the C-band SRTM 30-meter DEM were compared with point-wise elevations from the Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry for Otter Tail County, MN. The accuracy of SRTM DEM was measured as a function of land cover and geomorphologic characteristics. The typical mean vertical difference between the SRTM DEM and ICESat elevations in this study was determined for each classified land use type and the data properties were investigated. Also, the feasibility of using SRTM data for hydrologic applications, especially in a region of low relief exemplified by the Otter Tail basin in Minnesota, was examined in Chapter 3. For measuring lake levels, several lake-level estimation techniques using image processing and feature detection were tested with the Landsat imagery and SRTM data and the efficiency of the techniques were evaluated in Chapter 4. Lastly, the power law distribution of lake was simulated in Chapter 5. For the simulation, one-dimensional fractal landscapes were generated and precipitation and evaporation processes were added to the simulation algorithm to observe the effect of natural processes in lake formation. The simulation result for lake distribution was compared with real measurements and the lake distribution following the power law (linear scaling in logarithmic scale) distribution was shown.

Bhang, Kon Joon

349

33 CFR 207.170c - Kissimmee River, navigation locks between Lake Tohopekaliga and Lake Okeechobee, Fla.; use...  

Code of Federal Regulations, 2010 CFR

... Kissimmee River, navigation locks between Lake Tohopekaliga and Lake Okeechobee, Fla.; use, administration, and navigation...navigation locks between Lake Tohopekaliga and Lake Okeechobee, Fla.; use, administration, and...

2009-07-01

350

33 CFR 207.170c - Kissimmee River, navigation locks between Lake Tohopekaliga and Lake Okeechobee, Fla.; use...  

Code of Federal Regulations, 2010 CFR

... Kissimmee River, navigation locks between Lake Tohopekaliga and Lake Okeechobee, Fla.; use, administration, and navigation...navigation locks between Lake Tohopekaliga and Lake Okeechobee, Fla.; use, administration, and...

2010-07-01

351

Expansion of tubenose gobies Proterorhinus semilunaris into western Lake Erie and potential effects on native species  

USGS Publications Warehouse

The Eurasian freshwater tubenose goby Proterorhinus semilunaris (formerly Proterorhinus marmoratus) invaded the Laurentian Great Lakes in the 1990s, presumably via ballast water from transoceanic cargo ships. Tubenose gobies spread throughout Lake St. Clair, its tributaries, and the Detroit River system, and also are present in the Duluth-Superior harbor of Lake Superior. Using seines and bottom trawls, we collected 113 tubenose gobies between July 2007 and August 2009 at several locations in western Lake Erie. The number and range of sizes of specimens collected suggest that that tubenose gobies have become established and self-sustaining in the western basin of Lake Erie. Tubenose gobies reached maximum densities in sheltered areas with abundant macrophyte growth, which also is their common habitat in native northern Black Sea populations. The diet of tubenose gobies was almost exclusively invertebrates, suggesting dietary overlap with other benthic fishes, such as darters (Etheostoma spp. and Percina sp.), madtoms (Noturus spp.), and sculpins (Cottus spp.). A single mitochondrial DNA haplotype was identified, which is the most common haplotype found in the original colonization area in the Lake St. Clair region, suggesting a founder effect. Tubenose gobies, like round gobies Neogobius melanostomus, have early life stages that drift owing to vertical migration, which probably allowed them to spread from areas of colonization. The Lake St. Clair-Lake Erie corridor appears to have served as an avenue for them to spread to the western basin of Lake Erie, and abundance of shallow macrophyte-rich habitats may be a key factor facilitating their further expansion within Lake Erie and the remainder of the Laurentian Great Lakes.

Kocovsky, P. M.; Tallman, J. A.; Jude, D. J.; Murphy, D. M.; Brown, J. E.; Stepien, C. A.

2011-01-01

352

Response of the benthic nepheloid layer to near-inertial internal waves in southern Lake Michigan  

Microsoft Academic Search

Time series measurements of water transparency, water temperature, and current velocity were made at a station located in 58 m of water in southern Lake Michigan during the summer of 1995. Currents generated by near-inertial internal waves are correlated with variations in the thickness and in the vertical distribution of suspended sediment in the benthic nepheloid layer. Although a direct

Nathan Hawley

2004-01-01

353

Monitoring Crustal Deformation in The Geysers-Clear Lake Geothermal Area, California.  

National Technical Information Service (NTIS)

Geodetic surveys since 1972-1973 reveal significant crustal deformation in The Geysers-Clear Lake region. Resurveys of precise control networks are measuring both vertical and horizontal ground movement, with most of the change continuing in the area of g...

B. E. Lofgren

1978-01-01

354

Carbon as an indicator of Daphnia condition in an alpine lake  

Microsoft Academic Search

Carbon–length relationships can be used to indicate the condition of daphnids in natural situations. We examined the Daphnia galeata population of an alpine lake (Oberer, Arosasee, Switzerland), where most individuals display diel vertical migration behaviour (DVM). Normally, migrating daphnids face a trade-off between `predator safe areas' in the hypolimnion and `food rich areas' with high predation risk. However, in alpine

Monika Winder; Piet Spaak

2001-01-01

355

Double-diffusive deep water circulation in an iron-meromictic lake  

Microsoft Academic Search

From a small meromictic lake, we present observations of a circulation pattern that has not been documented in the limnological literature before. While surface cooling drives a vertical circulation of the upper water layer (mixolimnion), the deeper water layer (monimolimnion) is not included because of its higher salt concentration. However, double diffusion (higher diffusivity of heat than of dissolved substances)

Bertram Boehrer; Severine Dietz; Christoph von Rohden; Uwe Kiwel; Klaus D. Jöhnk; Sandra Naujoks; Johann Ilmberger; Dieter Lessmann

2009-01-01

356

A qualitative assessment of the influence of bioturbation in Lake Baikal sediments  

Microsoft Academic Search

The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The

Patrick Martin; Xavier Boes; Boudewijn Goddeeris; Nathalie Fagel

2005-01-01

357

Hypolimnetic Oxygen Depletion Dynamics in the Central Basin of Lake Erie  

Microsoft Academic Search

Hypolimnetic oxygen depletion has been recognized as a problem in the central basin of Lake Erie since the 1970s. However, recent expansion in distribution of the depletion after several years of low depletion rates in the 1990s has led investigators to explore the factors that influence the extent of the depletion. We have investigated the vertical oxygen budget in the

William J. Edwards; Joseph D. Conroy; David A. Culver

2005-01-01

358

Two Examples of Planetary Boundary Layer Modification Over the Great Lakes  

Microsoft Academic Search

Aircraft measurements of sensible and latent heat fluxes, surface and air temperature, mean wind and humidity were used to examine the boundary layer structure over the Great Lakes for two cases in late fall when the water was warmer than the air above. The sensible and latent vertical turbulent heat fluxes at the surface were in the range 5-10 mW

D. H. Lenschow

1973-01-01

359

The physical regime and the respective biogeochemical processes in the lower water mass of Lake Kinneret  

Microsoft Academic Search

Physical measurements made in Lake Kinneret, during the stratified period, indicate that the lower water mass (LWM) consists of two layers: a turbulent benthic boundary layer (BBL) and a hypolimnetic layer overlying the BBL. The water in the LWM moves in response to vertical mode one seiching of the metalimnion; this movement is accentuated near the perimeter of the metalimnion

A. Nishri; J. Imberger; W. Eckert; I. Ostrovsky; Y. Geifman

2000-01-01

360

Deformation of the Batestown till of the Lake Michigan lobe, Laurentide ice sheet  

Microsoft Academic Search

Deep, pervasive shear deformation of the bed to high strains (>100) may have been primarily responsible for flow and sediment transport of the Lake Michigan lobe of the Laurentide ice sheet. To test this hypothesis, we sampled at 0.2 m increments a basal till from one advance of the lobe (Batestown till) along vertical profiles and measured fabrics due to

Jason F. Thomason; Neal R. Iverson

2009-01-01

361

Aftershocks of the Coyote Lake, California, earthquake of August 6, 1979: A detailed study  

Microsoft Academic Search

Aftershock hypocenters and focal mechanism solutions for the Coyote Lake, California, earthquake reveal a geometrically complex fault structure, consisting of multiple slip surfaces. The faulting surface principally consists of two right stepping en echelon, northwest trending, partially overlapping, nearly vertical sheets and is similar in geometry to a slip surface inferred for the 1966 Parkfield, California, earthquake. The overlap occurs

P. Reasenberg; W. L. Ellsworth

1982-01-01

362

Testing the spatial and temporal framework of speciation in an ancient lake species flock: the leech genus Dina (Hirudinea: Erpobdellidae) in Lake Ohrid  

NASA Astrophysics Data System (ADS)

Ancient Lake Ohrid on the Balkan Peninsula is considered to be the oldest ancient lake in Europe with a suggested Plio-/Pleistocene age. Its exact geological age, however, remains unknown. Therefore, molecular clock data of Lake Ohrid biota may serve as an independent constraint of available geological data, and may thus help to refine age estimates. Such evolutionary data may also help unravel potential biotic and abiotic factors that promote speciation events. Here, mitochondrial sequencing data of one of the largest groups of endemic taxa in the Ohrid watershed, the leech genus Dina, is used to test whether it represents an ancient lake species flock, to study the role of potential horizontal and vertical barriers in the watershed for evolutionary events, to estimate the onset of diversification in this group based on molecular clock analyses, and to compare this data with data from other endemic species for providing an approximate time frame for the origin of Lake Ohrid. Based on the criteria speciosity, monophyly and endemicity, it can be concluded that Dina spp. from the Ohrid watershed, indeed, represents an ancient lake species flock. Lineage sorting of its species, however, does not seem to be complete and/or hybridization may occur. Analyses of population structures of Dina spp. in the Ohrid watershed indicate a horizontal zonation of haplotypes from spring and lake populations, corroborating the role of lake-side springs, particularly the southern feeder springs, for evolutionary processes in endemic Ohrid taxa. Vertical differentiation of lake taxa, however, appears to be limited, though differences between populations from the littoral and the profundal are apparent. Molecular clock analyses indicate that the most recent common ancestor of extant species of this flock is approximately 1.99 ± 0.83 million years (Ma) old, whereas the split of the Ohrid Dina flock from a potential sister taxon outside the lake is estimated at 8.30 ± 3.60 Ma. Comparisons with other groups of endemic Ohrid species indicated that in all cases, diversification within the watershed started ?2 Ma ago. Thus, this estimate may provide information on a minimum age for the origin of Lake Ohrid. Maximum ages are less consistent and generally less reliable. But cautiously, a maximum age of 3 Ma is suggested. Interestingly, this time frame of approximately 2-3 Ma ago for the origin of Lake Ohrid, generated based on genetic data, well fits the time frame most often used in the literature by geologists.

Trajanovski, S.; Albrecht, C.; Schreiber, K.; Schultheiß, R.; Stadler, T.; Benke, M.; Wilke, T.

2010-11-01

363

Impacts of climate, lake size, and supra- and sub-permafrost groundwater flow on lake-talik evolution, Yukon Flats, Alaska (USA)  

NASA Astrophysics Data System (ADS)

In cold regions, hydrologic systems possess seasonal and perennial ice-free zones (taliks) within areas of permafrost that control and are enhanced by groundwater flow. Simulation of talik development that follows lake formation in watersheds modeled after those in the Yukon Flats of interior Alaska (USA) provides insight on the coupled interaction between groundwater flow and ice distribution. The SUTRA groundwater simulator with freeze-thaw physics is used to examine the effect of climate, lake size, and lake-groundwater relations on talik formation. Considering a range of these factors, simulated times for a through-going sub-lake talik to form through 90 m of permafrost range from ˜200 to > 1,000 years (vertical thaw rates < 0.1-0.5 m yr-1). Seasonal temperature cycles along lake margins impact supra-permafrost flow and late-stage cryologic processes. Warmer climate accelerates complete permafrost thaw and enhances seasonal flow within the supra-permafrost layer. Prior to open talik formation, sub-lake permafrost thaw is dominated by heat conduction. When hydraulic conditions induce upward or downward flow between the lake and sub-permafrost aquifer, thaw rates are greatly increased. The complexity of ground-ice and water-flow interplay, together with anticipated warming in the arctic, underscores the utility of coupled groundwater-energy transport models in evaluating hydrologic systems impacted by permafrost.

Wellman, Tristan P.; Voss, Clifford I.; Walvoord, Michelle A.

2013-02-01

364

Contaminants in American alligator eggs from Lake Apopka, Lake Griffin, and Lake Okeechobee, Florida  

Microsoft Academic Search

Residues of organochlorine pesticides, polychlorinated biphenyls (PCBs), and 16 elements were measured in American alligator (Alligator mississippiensis) eggs collected in 1984 from Lakes Apopka, Griffin, and Okeechobee in central and south Florida. Organochlorine pesticides were highest in eggs from Lake Apopka. None of the elements appeared to be present at harmful concentrations in eggs from any of the lakes. A

Gary H. Heinz; H. Franklin Percival; Michael L. Jennings

1991-01-01

365

Volcanic lakes of the Azores archipelago (Portugal): Geological setting and geochemical characterization  

NASA Astrophysics Data System (ADS)

A representative set of 30 lakes from the Azores archipelago (Portugal) has been studied to obtain data on their volcanic setting and water geochemistry. The majority of the studied lakes are located inside volcanic craters and subsidence calderas, while the remaining lakes are located in topographic depressions not associated with volcanic centres, in depressions of tectonic origin and inside lava caves. In general, the Azorean volcanic lakes are small, with surface areas between 8.94 × 10- 4 km2 and 4.35 km2 and volumes between 2.4 × 103 and 4.78 × 107 m3; median = 3.99 × 104 m3, presenting maximum depths between 0.8 and 33 m. Mostly of the Na Cl to Na HCO3 type, the lake waters are generally low temperature (11.9 24.6 °C), very dilute (TDS range between 11.0 and 356.2 mg/L; median = 36.8 mg/L) and a clear exception is Furna do Enxofre lake (Graciosa island) that shows a Mg trend. Two types of lake waters can be recognized: 1) one is characterized by Na/Cl ratio close to the seawater value and have evolved, and evolve by marine contribution; and 2) Na HCO3 type waters that, in addition to sea-salt input, have been influenced by other processes (e.g., water rock interaction, hydrothermal seepage into the lake bottom) evident from higher total CO2 content (365.1 mg/L) and SiO2 content (74.9 mg/L), as well demonstrated by in the Furna do Enxofre lake. Nevertheless, volcanic contribution cannot be excluded for some lakes as Furna do Enxofre. Vertical profiles made at the deepest lakes of São Miguel reveal that major-ion content varies little with depth, largely independent of the occurrence of thermally driven density stratification in summer for some lakes. However, dissolved CO2 increases with depth and is kept in the hypolimnion in summer, whereas the HCO3- content is stable, suggesting that CO2 release exceeds acidity neutralization by water rock interaction. During winter, without stratification, the dissolved CO2 increase is less sharp for the majority of the lakes, with the exception of Furnas and Furna do Enxofre lakes. The CO2 enrichment observed for certain lakes (e.g., Furna do Enxofre and Furnas) implies a volcanic input. Moreover, as these lakes themselves are located near hydrothermal surface manifestations, they therefore offer good targets of volcano monitoring in the Azores.

Cruz, J. V.; Antunes, P.; Amaral, C.; França, Z.; Nunes, J. C.

2006-08-01

366

INAA Study of the Vertical Distribution of Some Major and Trace Elements in Lacustrine Sediments of the Danube Delta  

Microsoft Academic Search

The vertical profiles of 4 major (Na, K, Ca and Fe) and 17 trace elements (Rb, Cs, Ba, Sc, La, Ce, Sm, Eu, Tb, Yb, Lu, Th, U, Hf, Ta, Co and Cr) have been investigated in cores collected from three lakes: Lung, Mesteru and Furtuna, all of them situated in the Fluvio-lacustrine region of the Danube Delta. All profiles

L. C. Dinescu; O. G. Duliu; E. I. Andries

2000-01-01

367

Mechanism and control of lake eutrophication  

Microsoft Academic Search

A review about lake naturally eutrophicating, the internal loading of nutrients from lake sediment as well as the mechanism\\u000a of algal blooms and the control practices was made, especially the eutrophication problem of shallow lakes since seventy percent\\u000a of fresh water lakes in China are shallow lakes. It was found that shallow lakes are apt toward eutrophication than deep lakes.

Boqiang Qin; Liuyan Yang; Feizhou Chen; Guangwei Zhu; Lu Zhang; Yiyu Chen

2006-01-01

368

Institutional aspects of lake management  

NASA Astrophysics Data System (ADS)

The major barriers to successful lake management are institutional. However, in contrast to the technical and limnological dimensions of lake management, the institutional aspects of managing lakes have received little attention. The institutional factors that are important for successful lake management outcomes are: overlapping areal jurisdiction among governmental units, fragmented functional program responsibilities, ineffective coordination, limited authority, financial constraints, private sector roles, and inadequate public awareness and consensus. The range of typical institutional problems confronting lake management are well illustrated through experiences from the state of Wisconsin, USA. Because lake management programs with institutional shortcomings rarely realize their goals, it is critical to assimilate, evaluate, and apply our experience to date with the institutional arrangements necessary to effectively manage lake resources.

Born, Stephen M.; Rumery, Carolyn

1989-01-01

369

Major and trace elements in 35 lake and reservoir sediment cores from across the United States, 1994-2001  

USGS Publications Warehouse

This report presents data on major and trace element concentrations in sediment cores collected from 35 lakes and reservoirs during 1994-2001. The lakes and reservoirs are located in or near 18 major urban areas across the United States and provide a geographically diverse coverage of urban land use for the country as well as some reference settings. Vertical intervals of the cores were analyzed for eight major elements and eight trace elements.

Van Metre, Peter C.; Mahler, Barbara J.; Wilson, Jennifer T.; Callender, Edward

2006-01-01

370

33 CFR 162.132 - Connecting waters from Lake Huron to Lake Erie; communications rules.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Connecting waters from Lake Huron to Lake Erie; communications rules. 162.132 Section 162...162.132 Connecting waters from Lake Huron to Lake Erie; communications rules. (a) Radio listening...

2010-07-01

371

33 CFR 162.132 - Connecting waters from Lake Huron to Lake Erie; communications rules.  

Code of Federal Regulations, 2010 CFR

... 2009-07-01 false Connecting waters from Lake Huron to Lake Erie; communications rules. 162.132 Section 162...162.132 Connecting waters from Lake Huron to Lake Erie; communications rules. (a) Radio listening...

2009-07-01

372

14 CFR 93.69 - Special requirements, Lake Campbell and Sixmile Lake Airports.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 false Special requirements, Lake Campbell and Sixmile Lake Airports. 93.69 Section 93.69 Aeronautics...Terminal Area § 93.69 Special requirements, Lake Campbell and Sixmile Lake Airports. Each...

2013-01-01

373

Lakes, Lagerstaetten, and Evolution  

Microsoft Academic Search

The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method

E. G. Kordesch; L. E. Park

2001-01-01

374

Choking Lake Winnipeg  

Microsoft Academic Search

The problems of waterway eutrophication and coastal zone hypoxia are reaching epidemic proportions. Fresh water and coastal marine environments around the world are suffering unprecedented pollution loadings. We are developing an education program to address the dramatic need for public, community and K-12 education about the harsh impacts of elevated nutrient loads on fresh and marine water environments. The Lake

J. M. Byrne; L. J. Little; K. A. Dodgson; R. J. MacDonald; J. Graham

2009-01-01

375

Great Minds? Great Lakes!  

ERIC Educational Resources Information Center

|This booklet introduces an environmental curriculum for use in a variety of elementary subjects. The lesson plans provide an integrated approach to incorporating Great Lakes environmental issues into the subjects of history, social studies, and environmental sciences. Each of these sections contains background information, discussion points, and…

Environmental Protection Agency, Chicago, IL. Great Lakes National Program Office.

376

LAKE TAHOE VISIBILITY STUDY  

EPA Science Inventory

Visibility monitoring and airborne particulate sampling in the Lake Tahoe Basin were used to document visual air quality levels and to assess the relative impacts of major contributing emission source categories. Visibility data were obtained by long path contrast and particle sc...

377

The lakes of Titan  

Microsoft Academic Search

The surface of Saturn's haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface. Initial visible and radar imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface. Here we provide definitive evidence for

E. R. Stofan; C. Elachi; J. I. Lunine; R. D. Lorenz; B. Stiles; K. L. Mitchell; S. Ostro; L. Soderblom; C. Wood; H. Zebker; S. Wall; M. Janssen; R. Kirk; R. Lopes; F. Paganelli; J. Radebaugh; L. Wye; Y. Anderson; M. Allison; R. Boehmer; P. Callahan; P. Encrenaz; E. Flamini; G. Francescetti; Y. Gim; S. Hensley; W. T. K. Johnson; K. Kelleher; D. Muhleman; P. Paillou; G. Picardi; F. Posa; L. Roth; R. Seu; S. Shaffer; S. Vetrella

2007-01-01

378

Lake Ontario: Nearshore Variability  

EPA Science Inventory

We conducted a high-resolution survey with towed electronic instrumentation along the Lake Ontario nearshore (720 km) at a 20 meter contour. The survey was conducted September 6-10, 2008 with a shorter 300 km survey conducted August 14-15 for comparing of temporal variability. ...

379

Pictures of Mono Lake  

NSDL National Science Digital Library

This site briefly introduces the history and ecology of Mono Lake. It is comprised of 27 professional photographs, each offering a visual insight into the community's unusual landscape. All images are accompanied with a brief description. Downloads and wallpaper are available with a paid membership.

Luong, Quang-Tuan; Terra Galleria Photography, QTL@terragalleria.com

380

POLLUTION IN LAKES (OUTLINE)  

Microsoft Academic Search

We present a model of two interconnected reservoirs and solutes flowing into them. We derive a system of dierential equation for the time- dependent concentrations of solutes in the two reservoirs. Then we apply our model to simulate concentration of pollutants in lakes Erie and Ontario. This project is based on a case study in the course's textbook (1) with

ROUBEN ROSTAMIAN

381

Lake Michigan: Nearshore Variability  

EPA Science Inventory

We conducted a high-resolution survey in the nearshore of Lake Michigan at a 20 meter contour using towed electronic instrumentation. The nearly 1200 km survey was conducted Sep 8-15, 2010. We also conducted six cross-contour tows. Along the survey tracks we sampled fixed stat...

382

Predation of lake trout and lake whitefish embryos by crayfish: Implications of shifts in crayfish dominance in Lake Simcoe  

Microsoft Academic Search

We compared predation rates of two Lake Simcoe crayfish, Orconectes virilis and Orconectes propinquus, on lake trout and lake whitefish eggs and alevins in laboratory experiments and assessed the potential impact of predation on egg survival in the lake. Experiments were conducted at 4 and 8°C on gravel and one or three layers of cobble substrate. Predation rates on lake

Kristine Mason; David O. Evans

2011-01-01

383

Comparative environmental analyses of paddy fields in two lake catchment areas: Lake Taihu, China and Lake Biwa, Japan  

Microsoft Academic Search

Eutrophication in Taihu Lake has become a serious environmental problem. In this paper, environmental conditions in paddy fields in Taihu Lake's catchment area were compared with those in Lake Biwa's catchment area, which revealed issues on social development at different stages and raised questions over restoration of Taihu Lake from an environmental sociology perspective. Keywords-lake; eutrophication; paddy field; non-point source;

Yang Ping; Zhu Wei; Tan Xiao

2011-01-01

384

Vertical axis wind turbine airfoil  

SciTech Connect

A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

2012-12-18

385

Mated Vertical Ground Vibration Test.  

National Technical Information Service (NTIS)

The Mated Vertical Ground Vibration Test (MVGVT) was considered to provide an experimental base in the form of structural dynamic characteristics for the shuttle vehicle. This data base was used in developing high confidence analytical models for the pred...

E. W. Ivey

1980-01-01

386

Horizontal Inequity and Vertical Redistribution  

Microsoft Academic Search

Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together, horizontalinequity measures loss of vertical performance. The identification problem,which has previously been thought insuperable, is addressed by

Peter J. Lambert; Xavier Ramos

1997-01-01

387

Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology  

NASA Astrophysics Data System (ADS)

A new catalog of 210 open-basin lakes (lakes with outlet valleys) fed by valley networks shows that they are widely distributed in the Noachian uplands of Mars. In order for an outlet valley to form, water must have ponded in the basin to at least the level of the outlet. We use this relationship and the present topography to directly estimate the minimum amount of water necessary to flood these basins in the past. The volumes derived for the largest lakes (˜3×10 to ˜2×10 km) are comparable to the largest lakes and small seas on modern Earth, such as the Caspian Sea, Black Sea, and Lake Baikal. We determine a variety of other morphometric properties of these lakes and their catchments (lake area, mean depth, volume, shoreline development, outlet elevation, and watershed area). Most candidate lakes have volumes proportional to and commensurate with their watershed area, consistent with precipitation as their primary source. However, other lakes have volumes that are anomalously large relative to their watershed areas, implying that groundwater may have been important in their filling. Candidate groundwater-sourced lakes are generally concentrated in the Arabia Terra region but also include the Eridania basin [Irwin, R.P., Howard, A.D., Maxwell, T.A., 2004a. J. Geophys. Res. 109, doi: 10.1029/2004JE002287. E12009; Irwin, R.P., Watters, T.R., Howard, A.D. Zimbelman, J.R., 2004b. J. Geophys. Res. 109, doi: 10.1029/2004JE002248. E09011] and several lakes near the dichotomy boundary. This areal distribution is broadly consistent with where groundwater should have reached the surface as predicted by current models. Both surface runoff and groundwater flow appear to have been important sources for lakes and lake chains, suggesting a vertically integrated hydrological system, the absence of a global cryosphere, and direct communication between the surface and subsurface hydrosphere of early Mars.

Fassett, Caleb I.; Head, James W.

2008-11-01

388

SIMULATIONS OF ENVIRONMENTAL CONDITIONS CONDUCIVE TO THE FORMATION OF LAKE-TO-LAKE BANDS  

Microsoft Academic Search

Lake-effect snow has a large influence on the Great Lakes region, often enhancing snowfall downwind of the lakes. Several different types of lake-effect bands exist, but lake-to-lake (L2L) bands remain the least studied. L2L bands are cloud bands that extend from one lake across intervening land and a downwind lake, and occur due to preconditioning in the heat and moisture

Joanna T. George; Mark R. Hjelmfelt; William J. Capehart

389

Toxic Contaminants in the Great Lakes  

SciTech Connect

Examines the effects and problems of toxic contaminants entering into and moving through the Great Lakes, describing the physical and chemical processes of lake pollution. With a view to control these processes, this volume includes methodologies for environmental monitoring. Analyzes the processes and effects of major contaminants including lead, PCBs, and dioxin. Contents: Perspectives on Human Health Concerns from Great Lakes Contaminants Atmospheric Inputs of Chlorinated Hydrocarbons to the Great Lakes; Petroleum Contaminants in the Great Lakes; Distribution of Polycyclic Aromatic Hydrocarbons in the Great Lakes; Organic Pollutants in Lake Ontario Partitioning of Toxic Trace Metals Between Solid and Liquid Phases in the Great Lakes; Inorganic Contaminants in Lake Michigan Sediments.

Nriagu, J.O.; Simons, M.S.

1983-01-01

390

Lake Mead--clear and vital  

USGS Publications Warehouse

Lake Mead – Clear and Vital” is a 13 minute documentary relating the crucial role of science in maintaining high water quality in Lake Mead. The program was produced coincident with release of the Lakes Mead and Mohave Circular a USGS publication covering past and on-going research in the lakes and tributaries of the Lake Mead National Recreation Area.

Wessells, Stephen M.; Rosen, Michael

2013-01-01

391

Lake Erie...Take a Bow.  

ERIC Educational Resources Information Center

|This elementary school teaching unit was developed as a part of a series of teaching units that deal with Lake Erie. This unit was developed to enable children to: (1) identify the Great Lakes and pick out Lake Erie on a map; (2) demonstrate knowledge of Lake Erie's origin and geography; (3) list some uses of Lake Erie; and (4) give examples of…

Canning, Maureen; Dunlevy, Margie

392

Predicting Maximum Lake Depth from Surrounding Topography  

EPA Science Inventory

Lake volume aids understanding of the physical and ecological dynamics of lakes, yet is often not readily available. The data needed to calculate lake volume (i.e. bathymetry) are usually only collected on a lake by lake basis and are difficult to obtain across broad regions. ...

393

Aquatic macrophytes as tools for lake management  

Microsoft Academic Search

Aquatic macrophytes can serve as useful indicators of water pollution along the littoral of lakes. In Bavaria, the sub- merged vegetation of about 100 lakes has been investigated by SCUBA diving over the past decade to evaluate the state of nutrient pollution. All lakes are marl lakes located in the northern calcareous alps and the prealpine region. The lakes differ

Arnulf Melzer

1999-01-01

394

Aquatic macrophytes as tools for lake management  

Microsoft Academic Search

Aquatic macrophytes can serve as useful indicators of water pollution along the littoral of lakes. In Bavaria, the submerged vegetation of about 100 lakes has been investigated by SCUBA diving over the past decade to evaluate the state of nutrient pollution. All lakes are marl lakes located in the northern calcareous alps and the prealpine region. The lakes differ in

Arnulf Melzer

1999-01-01

395

The effect of irradiance, vertical mixing and temperature on spring phytoplankton dynamics under climate change: long-term observations and model analysis  

Microsoft Academic Search

Spring algal development in deep temperate lakes is thought to be strongly influenced by surface irradiance, vertical mixing\\u000a and temperature, all of which are expected to be altered by climate change. Based on long-term data from Lake Constance, we\\u000a investigated the individual and combined effects of these variables on algal dynamics using descriptive statistics, multiple\\u000a regression models and a process-oriented

Katrin Tirok; Ursula Gaedke

2007-01-01

396

Deglacial and Lake Level Fluctuation History Recorded in Cores, Beaver Lake, Upper Peninsula, Michigan  

Microsoft Academic Search

Sediment cores collected from the littoral and pelagic zones of Beaver Lake, Michigan record fluctuations in the water level of Lake Superior. Beaver Lake is a small 300 ha lake in Pictured Rocks National Lakeshore (PRNL) now separated from Lake Superior by a dune-capped barrier bar. Cores were collected using a vibracorer from a lake-ice platform in February 1997. A

Timothy G. Fisher; Richard L. Whitman

1999-01-01

397

77 FR 39638 - Safety Zone; Barbara Harder Wedding Fireworks, Lake Erie, Lake View, NY  

Federal Register 2010, 2011, 2012, 2013

...Wedding Fireworks, Lake Erie, Lake View, NY AGENCY: Coast Guard, DHS. ACTION: Temporary...temporary safety zone on Lake Erie, Lake View, NY. This safety zone is intended to restrict...will be held on Lake Erie near Lake View, NY. The Captain of the Port Buffalo has...

2012-07-05

398

Internal Waves and Turbulence Production in Arctic Lakes  

NASA Astrophysics Data System (ADS)

We present time series measurements of lake thermal structure, internal waves, temperature-gradient microstructure, current velocities and eddy diffusivities in an arctic kettle lake 150 hectares in area. Lake numbers, a dimensionless index similar to the Wedderburn number, drop into critical ranges (W < 1 and 1 < W < 3.3) for internal bores or for surges and solitons due to the passage of atmospheric fronts with sustained winds. The coefficient of eddy diffusivity as measured by the heat budget method increases to values in excess of 10-6 m2 s-1 in the metalimnion and 10-5 m2 s-1 in the hypolimnion. Relaxation after the events produces 2nd vertical mode waves with frequencies higher than those predicted for seiches. Rate of dissipation of turbulent kinetic energy during these events is 10-9 m2s-3 and eddy diffusivities, computed following Osborn (1980) are in agreement with those from the heat budget method. Current speeds are at most 2 cm s-1 but Richardson numbers drop below critical with the expansion of the second vertical mode waves and upwelling.

MacIntyre, S.; Fram, J. P.; Benson, B.; Layns, A.

2008-12-01

399

A "GLIMPCE" of the deep crust beneath the Great Lakes  

NASA Astrophysics Data System (ADS)

Approximately 1350 km of multichannel seismic reflection data and an equivalent amount of seismic refraction data have been collected across the North American Great Lakes. The seismic surveys, sponsored by the Great Lakes International Multidisciplinary Program on Crustal Evolution (GLIMPCE), were designed to resolve the deep crustal structure of the 1.89-1.82 Ga Penokean orogen, the 1.3-1.0 Ga Grenville orogen and the 1.11-1.09 Ga Mid-continent rift system. In north-central Lake Huron a band of gently east-dipping reflections at about 18-20 km depth separates a complex and highly reflective lower crustal layer from a markedly less reflective upper crustal layer. The lower layer is interpreted as attenuated crust of the Superior cratonic margin and the upper layer is assumed to be composed of continental margin deposits of the Huron supergroup, an exotic mass that collided with the cratonic margin during the Penokean orogeny, and younger granites and rhyolites. The intervening band of gently east-dipping reflections may delineate a master decollement zone, active during the Penokean orogeny. All structures in north-central Lake Huron are truncated abruptly at the western end of Georgian Bay by the Grenville Front, represented by the westernmost event of a spectacular series of moderately east-dipping reflections. These reflections, which extend from the surface to about 55 km depth, are interpreted as discontinuities between gneissic and migmatitic rocks of varying lithology. Where exposed in the Grenville front tectonic zone, the different rock units are commonly juxtaposed along mylonite zones with a northwest thrust sense. Moho may deepen by 5-10 km along a narrow region just southeast of the Grenville front. Seismic reflection data from Lake Superior reveal an extraordinary thickness of Keweenawan mafic lavas and sedimentary rocks deposited in a number of discrete grabens/half-grabens of the Midcontinent (Keweenawan) rift system. Total vertical thickness of layered Keweenawan strata exceeds 30 km beneath some parts of the lake. The geometry of the central basin changes significantly along the axis of the Midcontinent rift system. In western Lake Superior the Keweenawan lavas thicken northward toward a south-dipping growth fault, in the center of the lake they thicken southward toward a northdipping growth fault, and in the eastern part of the lake the structures are relatively symmetric. These mega-grabens and mega-half-grabens with differing asymmetries are separated by transfer faults or accommodation zones recognized on potential field maps. The segmented character of the MRS is similar to that observed along some passive continental margins and the East African rift system.

Green, Alan G.; Cannon, W. F.; Milkereit, B.; Hutchinson, D. R.; Davidson, A.; Behrendt, J. C.; Spencer, C.; Lee, M. W.; Morel-á-l'Huissier, P.; Agena, W. F.

400

Genetic diversity of Diporeia in the Great Lakes: comparison of Lake Superior to the other Great Lakes  

EPA Science Inventory

Abundances of Diporeia have dropped drastically in the Great Lakes, except in Lake Superior, where data suggest that population counts actually have risen. Various ecological, environmental, or geographic hypotheses have been proposed to explain the greater abundance of Lake Supe...

401

78 FR 53675 - Safety Zone; Lake Erie Heritage Foundation, Battle of Lake Erie Reenactment; Lake Erie, Put-in...  

Federal Register 2010, 2011, 2012, 2013

...Guard 33 CFR Part 165 [Docket No. USCG-2013-0546] RIN 1625-AA00 Safety Zone; Lake Erie Heritage Foundation, Battle of Lake Erie Reenactment; Lake Erie, Put-in-Bay, OH AGENCY: Coast Guard, DHS. ACTION: Temporary final...

2013-08-30

402

A paleolimnological assessment of lake acidification in five Connecticut lakes  

Microsoft Academic Search

New England has received significant amounts of precipitation with a pH between 4.2 and 4.6. Paleolimnological studies based on siliceous microalgal remains support the hypothesis that some lakes in northern New England have acidified as a result of the acidic deposition. However, paleolimnological analyses from five software lakes in southern New England suggest that these lakes have not acidified in

Laurence J. Marsicano; Peter A. Siver

1993-01-01

403

A combined heat and water budget approach to quantify the groundwater inflow to a meromictic lake  

NASA Astrophysics Data System (ADS)

Groundwater exchange may have an important role in the mixing dynamics of certain lakes, and this may be comparable with near-surface mixing due to conventionally-defined surface radiation and turbulent heat fluxes. However, the heat and mass fluxes associated with groundwater input to a lake are often difficult to measure and are poorly constrained. Permanent bottom anoxia in meromictic lakes is sometimes associated with significant inputs of subsurface water, which creates a permanent upwelling system for phytoplankton blooms. This contribution presents the results of a 17 month experimental investigation of the heat and water budget of a meromictic lake in upstate New York. Fayetteville Green Lake is a good model system to conduct a combined heat and water budget analysis. It is a comparatively simple mass exchange system with one outflow stream and one significant inflow stream in addition to an important subsurface groundwater source. The lake is contained in a relatively deep (~50m) flat-bottomed basin with a groundwater injection depth at ~20m at the base of the mixolimnion. The heat budget was formulated from data from regional meteorological stations and a vertical array of temperature sensors on a subsurface mooring. The mass budget was created from continuous measurements of lake stage and precipitation data. The results highlight that groundwater input has an important effect on the overall heat budget of the lake, with an important role on the timing of the overturning of the mixolimnion in the spring and late autumn. Although lake heat budget studies have formerly been conducted to constrain the poorly-constrained evaporative term (latent heat) in the surface heat budget, the results of this study suggest that groundwater exchange may more important than the surface latent heat flux of certain lakes.

Kettle, Anthony; Back, Richard

2013-04-01

404

A combined heat and water budget approach to quantify the groundwater inflow to a meromictic lake  

NASA Astrophysics Data System (ADS)

Groundwater exchange may have an important role in the mixing dynamics of certain lakes, in addition to the recognized effect of seasonally varying surface heat fluxes. However, the heat and mass fluxes associated with groundwater input to a lake are often difficult to measure and are poorly constrained. Permanent bottom anoxia in meromictic lakes is sometimes associated with significant inputs of surface water, which create a permanent upwelling system for phytoplankton blooms. In this contribution, we report the results of a 17 month experimental investigation of the heat and water budget of a meromictic lake in upstate New York. Fayetteville Green Lake is a good model system to conduct a combined heat and water budget analysis, with one outflow stream and a single inflow stream. The lake is contained in a relatively deep (~50m) flat-bottomed basin with a groundwater injection depth at ~20m at the base of the mixolimnion. The heat budget was formulated from data from regional meteorological stations and a vertical array of temperature sensors on a subsurface mooring. The mass budget was created from continuous measurements of lake stage and precipitation data. The results highlight that groundwater input has an important effect on the overall heat budget of the lake, with a critical role on the timing of the overturning of the mixolimnion in the spring and late autumn. Although lake heat budget studies have formerly been conducted to constrain the poorly-constrained evaporative term (latent heat) in the heat budget, our results suggest that groundwater exchange may dominate the surface latent heat flux of certain lakes.

Kettle, A.; Back, R.

2012-04-01

405

Note: Origins of rainbow smelt in Lake Ontario  

USGS Publications Warehouse

The first rainbow smelt (Osmerus mordax) to enter Lake Ontario were probably migrants from an anadromous strain introduced into New York's Finger Lakes. Since the upper Great Lakes were originally stocked with a landlocked strain from Green Lake, Maine, subsequent migration to Lake Ontario from Lake Erie makes Lake Ontario unique among the Great Lakes in probably having received introductions from two distinct populations.

Bergstedt, Roger A.

1983-01-01

406

Minneapolis Chain of Lakes Research and Demonstration Project.  

National Technical Information Service (NTIS)

Five lakes, Lake Harriet, Lake Calhoun, Lake of the Isles, Cedar Lake and Brownie Lake, comprise the Minneapolis Chain of Lakes. A previous study identified urban drainage as the major factor determining the water quality of the lakes. Subsequently, the C...

J. B. Erdmann E. J. Johnson N. C. Wenck E. A. Hickok

1981-01-01

407

A gazetteer of surface-mine lakes, Eastern Interior Coal Province, Illinois  

USGS Publications Warehouse

Hundreds of lakes have been formed as a result of surface mining in Area 35 of the Eastern Interior Coal Province in Illinois. This gazetteer contains physical and chemical data from 107 surface-mine lakes sampled from June through August 1983. Information collected includes location, morphology, and vertical profile measurements of water quality of the lakes. Sampled lakes range in size from 8.8 to 210 acres, and are from 4.0 to 92.0 feet deep. Maximum widths range from 0.03 to 0.35 mile, and maximum lengths range from 0.27 to 3.08 miles. Some lake waters were stratified, whereas others were completely mixed. General water quality differed widely among the lakes. Specific conductances ranged from 130 to 7,800 micromhos per centimeter (at 25 degrees Celsius). Specific conductances of 2 ,000 to 5,000 micromhos per centimeter were most prevalent. The pH values ranged from 1.8 to 9.6 at the surface, whereas bottom measurements ranged from 2.0 to 8.5. Water temperatures near the surface ranged from 22.5 degrees Celsius in June to 34.5 degrees Celsius in August. Dissolved-oxygen concentrations differed greatly among the lakes; concentrations near the surface ranged from 6.0 to 13.2 milligrams per liter. Transparencies ranged from 0.3 to 35.4 feet. (USGS)

Voelker, D. C.

1985-01-01

408

Vertical structure of debris discs  

NASA Astrophysics Data System (ADS)

Context: The vertical thickness of debris discs is often used as a measure of these systems' dynamical excitation, and as clues to the presence of hidden massive perturbers such as planetary embryos. However, this argument might be flawed because the observed dust should be naturally placed on inclined orbits by the combined effect of radiation pressure and mutual collisions. Aims: We critically reinvestigate this issue and numerically estimate the “natural” vertical thickness of a collisionally evolving disc, in the absence of any additional perturbing body. Methods: We use a deterministic collisional code, to follow the dynamical evolution of a population of indestructible test grains suffering mutual inelastic impacts. Grain differential sizes as well as the effect of radiation pressure are taken into account. Results: We find that, under the coupled effect of radiation pressure and collisions, grains naturally acquire inclinations of a few degrees. The disc is stratified with respect to grain sizes, the smallest grains having the largest vertical dispersion and the largest being clustered closer to the midplane. Conclusions: Debris discs should have a minimum “natural” observed aspect ratio hmin ~ 0.04±0.02 from visible to mid-IR wavelengths, where the flux is dominated by the smallest bound grains. These values are comparable to the estimated thicknesses of several vertically resolved debris discs, as illustrated by the specific example of AU Mic. For all systems with h ~ hmin, the presence (or absence) of embedded perturbing bodies cannot be inferred from the vertical dispersion of the disc.

Thébault, P.

2009-10-01

409

Laurentian Great Lakes Basin Climate Change Adaptation.  

National Technical Information Service (NTIS)

The NOAA Great Lakes Regional Collaboration Team, Great Lakes Sea Grant Network, and Old Woman Creek National Estuarine Research Reserve are working with the Great Lakes & Saint Lawrence Cities Initiative to develop specialized training to build the capac...

D. Forsythe D. Nelson H. Elmer R. Held S. Casey

2011-01-01

410

Limnology of Lake Champlain: 1965-1970.  

National Technical Information Service (NTIS)

This five year study assembled information on physical, chemical, and biological characteristics of Lake Champlain, Vermont, one of the largest and deepest lakes of the USA. The determinations included currents of the lake, water thermal and optical featu...

E. B. Henson M. Potash

1970-01-01

411

27 CFR 9.83 - Lake Erie.  

Code of Federal Regulations, 2010 CFR

...for determining the boundaries of the Lake Erie viticultural area are four U...1962). (c) Boundaries. The Lake Erie viticultural area is located along...shore and on the islands of Lake Erie across the States of New York,...

2009-04-01

412

27 CFR 9.83 - Lake Erie.  

Code of Federal Regulations, 2010 CFR

...for determining the boundaries of the Lake Erie viticultural area are four U...1962). (c) Boundaries. The Lake Erie viticultural area is located along...shore and on the islands of Lake Erie across the States of New York,...

2010-04-01

413

Columbia Lakes Diagnostic-Feasibility Study.  

National Technical Information Service (NTIS)

Land development has caused increased stormwater runoff, siltation and algal blooms in Wilde Lake, Lake Kittamagundi, and Lake Elkhorn, MD. The recommendations made for restoration are sediment ponds and manmade wetlands to be used as detention basins, lo...

F. X. Browne V. M. Ross

1982-01-01

414

Assessing the spatial and temporal variability of groundwater-lake exchange using DTS, seepage meters and natural tracers  

NASA Astrophysics Data System (ADS)

The rate of groundwater seepage into acid mine lakes can alter the biogeochemical conditions at the water-sediment interface, which control the release of acidity into the lake water. In turn long-term water quality depends on the rate of groundwater seepage. Therefore quantifying the spatial and temporal variability of lake-groundwater exchange is a great concern in remediation of such lakes. Groundwater-lake exchange was investigated in an acid mine lake in Eastern Germany using seepage meters, vertical chloride and temperature profiles and fibre optic distributed temperature sensing (DTS). During a year with relatively constant lake level distinct spatial patterns of groundwater inflow and outflow could be detected by using seepage meters. Seepage rates were found to be steady in time but highly variable in space (2-3 orders of magnitude). A general pattern with influent conditions (groundwater inflow) in the north and effluent conditions in the south was observed. Along the eastern and western shores of the lake transitional conditions were found. Local hot spots with groundwater seepage rates in excess of 200mm/d were found in the deeper sections of the lake suggesting preferential seepage via high-conductivity zones in the underlying aquifer. Local seepage rates from seepage meters could be verified with flux rates inverted from vertical chloride profiles obtained from pore water peepers at several locations. To identify further possible hot spots of groundwater seepage thermal anomalies were mapped on a smaller scale near the north shore using fibre optic distributed temperature sensing (DTS). Areas of preferential up-welling of groundwater are expected to show a lower daily temperature amplitude at the water-sediment interface than areas with little groundwater inflow. Areas with distinct anomalies in amplitude could be identified, which will serve as additional locations for further point measurements. In a planned lake-level manipulation experiment seepage rates will be altered to investigate the effects of temporal changes on biogeochemical processes and acidity generation.

Neumann, C.; Fleckenstein, J. H.; Hausner, M. B.; Tyler, S. W.

2009-04-01

415

Wisconsin's Great Lakes Shipwrecks  

NSDL National Science Digital Library

What better way to beat the heat than to imagine diving into the deep, cool waters of Lake Superior (average temp: Ten degrees above freezing) without having to leave your desk. This exceptional shipwreck site, produced by the Wisconsin Historical Society and the UW Madison Sea Grant Institute, allows the visitor to pick her or his lake, Superior or Michigan, and explore the many shipwrecks that are chronicled there. The exhibits include photo galleries and video, taking the visitor up-close with these fascinating underwater artifacts. Deeper in the site is a section called Notes in the Field, where scientists involved in this summer's exploration of the Kate Kelly, a schooner that reefed between Milwaukee and Chicago in 1895, provide a daily log of their activities. Also off of this link is another link to the Kids' Corner, which provides all sorts of good information for kids and teachers about underwater archaeology and shipwrecks. This is definitely a site worth diving into.

416

Hydrologic Data for Deep Creek Lake and Selected Tributaries, Garrett County, Maryland, 2007-08  

USGS Publications Warehouse

Introduction Recent and ongoing efforts to develop the land in the area around Deep Creek Lake, Garrett County, Maryland, are expected to change the volume of sediment moving toward and into the lake, as well as impact the water quality of the lake and its many tributaries. With increased development, there is an associated increased demand for groundwater and surface-water withdrawals, as well as boat access. Proposed dredging of the lake bottom to improve boat access has raised concerns about the adverse environmental effects such activities would have on the lake. The Maryland Department of Natural Resources (MDDNR) and the U.S. Geological Survey (USGS) entered into a cooperative study during 2007 and 2008 to address these issues. This study was designed to address several objectives to support MDDNR?s management strategy for Deep Creek Lake. The objectives of this study were to: Determine the current physical shape of the lake through bathymetric surveys; Initiate flow and sediment monitoring of selected tributaries to characterize the stream discharge and sediment load of lake inflows; Determine sedimentation rates using isotope analysis of sediment cores; Characterize the degree of hydraulic connection between the lake and adjacent aquifer systems; and Develop an estimate of water use around Deep Creek Lake. Summary of Activities Data were collected in Deep Creek Lake and in selected tributaries from September 2007 through September 2008. The methods of investigation are presented here and all data have been archived according to USGS policy for future use. The material presented in this report is intended to provide resource managers and policy makers with a broad understanding of the bathymetry, surface water, sedimentation rates, groundwater, and water use in the study area. The report is structured so that the reader can access each topic separately using any hypertext markup (HTML) language reader. In order to establish a base-line water-depth map of Deep Creek Lake, a bathymetric survey of the lake bottom was conducted in 2007. The data collected were used to generate a bathymetric map depicting depth to the lake bottom from a full pool elevation of 2,462 feet (National Geodetic Vertical Datum of 1929). Data were collected along about 90 linear miles across the lake using a fathometer and a differentially corrected global positioning system. As part of a long-term monitoring plan for all surface-water inputs to the lake, streamflow data were collected continuously at two stations constructed on Poland Run and Cherry Creek. The sites were selected to represent areas of the watershed under active development and areas that are relatively stable with respect to development. Twelve months of discharge data are provided for both streams. In addition, five water-quality parameters were collected continuously at the Poland Run station including pH, specific conductance, temperature, dissolved oxygen, and turbidity. Water samples collected at Poland Run were analyzed for sediment concentration, and the results of this analysis were used to estimate the annual sediment load into Deep Creek Lake from Poland Run. To determine sedimentation rates, cores of lake-bottom sediments were collected at 23 locations. Five of the cores were analyzed using a radiometric-dating method, allowing average rates of sedimentation to be estimated for the time periods 1925 to 2008, 1925 to 1963, and 1963 to 2008. Particle-size data from seven cores collected at locations throughout the study area were analyzed to provide information on the amount of fine material in lake-bed sediments. Groundwater levels were monitored continuously in four wells and weekly in nine additional wells during October, November, and December of 2008. Water levels were compared to recorded lake levels and precipitation during the same period to determine the effect of lake-level drawdown and recovery on the adjacent aquifer systems. Water use in the Deep Creek Lake wa

Banks, William S. L.; Davies, William J.; Gellis, Allen C.; LaMotte, Andrew E.; McPherson, Wendy S.; Soeder, Daniel J.

2010-01-01

417

Microbial diversity of soda lakes  

Microsoft Academic Search

Soda lakes are highly alkaline extreme environments that form in closed drainage basins exposed to high evaporation rates.\\u000a Because of the scarcity of Mg2+ and Ca2+ in the water chemistry, the lakes become enriched in CO3\\u000a 2? and Cl?, with pHs in the range 8 to >12. Although there is a clear difference in prokaryotic communities between the hypersaline\\u000a lakes

B. E. Jones; William D. Grant; A. W. Duckworth; G. G. Owenson

1998-01-01

418

Great Lakes estuaries  

Microsoft Academic Search

Conclusions  According to the geomorphology and physiography classification scheme for estuaries proposed by Pritchard (1967) and presented\\u000a in Kennish (1986), Great Lakes estuaries can be classified as Type A: drowned river valleys or rias. The termination of Wisconsinian\\u000a glaciation, which resulted in a eustatic rise in sea level of somewhat over 100 m and the formation of such Atlantic coast\\u000a estuaries

Charles E. Herdendorf

1990-01-01

419

Hydrocarbon lakes on Titan  

NASA Astrophysics Data System (ADS)

The Huygens Probe detected dendritic drainage-like features, methane clouds and a high surface relative humidity (˜50%) on Titan in the vicinity of its landing site [Tomasko, M.G., and 39 colleagues, 2005. Nature 438, 765-778; Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784], suggesting sources of methane that replenish this gas against photo- and charged-particle chemical loss on short (10-100) million year timescales [Atreya, S.K., Adams, E.Y., Niemann, H.B., Demick-Montelara, J.E., Owen, T.C., Fulchignoni, M., Ferri, F., Wilson, E.H., 2006. Planet. Space Sci. In press]. On the other hand, Cassini Orbiter remote sensing shows dry and even desert-like landscapes with dunes [Lorenz, R.D., and 39 colleagues, 2006a. Science 312, 724-727], some areas worked by fluvial erosion, but no large-scale bodies of liquid [Elachi, C., and 34 colleagues, 2005. Science 308, 970-974]. Either the atmospheric methane relative humidity is declining in a steady fashion over time, or the sources that maintain the relative humidity are geographically restricted, small, or hidden within the crust itself. In this paper we explore the hypothesis that the present-day methane relative humidity is maintained entirely by lakes that cover a small part of the surface area of Titan. We calculate the required minimum surface area coverage of such lakes, assess the stabilizing influence of ethane, and the implications for moist convection in the atmosphere. We show that, under Titan's surface conditions, methane evaporates rapidly enough that shorelines of any existing lakes could potentially migrate by several hundred m to tens of km per year, rates that could be detected by the Cassini orbiter. We furthermore show that the high relative humidity of methane in Titan's lower atmosphere could be maintained by evaporation from lakes covering only 0.002-0.02 of the whole surface.

Mitri, Giuseppe; Showman, Adam P.; Lunine, Jonathan I.; Lorenz, Ralph D.

2007-02-01

420

Archaea in Yellowstone Lake  

PubMed Central

The Yellowstone geothermal complex has yielded foundational discoveries that have significantly enhanced our understanding of the Archaea. This study continues on this theme, examining Yellowstone Lake and its lake floor hydrothermal vents. Significant Archaea novelty and diversity were found associated with two near-surface photic zone environments and two vents that varied in their depth, temperature and geochemical profile. Phylogenetic diversity was assessed using 454-FLX sequencing (?51?000 pyrosequencing reads; V1 and V2 regions) and Sanger sequencing of 200 near-full-length polymerase chain reaction (PCR) clones. Automated classifiers (Ribosomal Database Project (RDP) and Greengenes) were problematic for the 454-FLX reads (wrong domain or phylum), although BLAST analysis of the 454-FLX reads against the phylogenetically placed full-length Sanger sequenced PCR clones proved reliable. Most of the archaeal diversity was associated with vents, and as expected there were differences between the vents and the near-surface photic zone samples. Thaumarchaeota dominated all samples: vent-associated organisms corresponded to the largely uncharacterized Marine Group I, and in surface waters, ?69–84% of the 454-FLX reads matched archaeal clones representing organisms that are Nitrosopumilus maritimus-like (96–97% identity). Importance of the lake nitrogen cycling was also suggested by >5% of the alkaline vent phylotypes being closely related to the nitrifier Candidatus Nitrosocaldus yellowstonii. The Euryarchaeota were primarily related to the uncharacterized environmental clones that make up the Deep Sea Euryarchaeal Group or Deep Sea Hydrothermal Vent Group-6. The phylogenetic parallels of Yellowstone Lake archaea to marine microorganisms provide opportunities to examine interesting evolutionary tracks between freshwater and marine lineages.

Kan, Jinjun; Clingenpeel, Scott; Macur, Richard E; Inskeep, William P; Lovalvo, Dave; Varley, John; Gorby, Yuri; McDermott, Timothy R; Nealson, Kenneth

2011-01-01

421

Method for lake restoration  

DOEpatents

A process for removing pollutants or minerals from lake, river or ocean sediments or from mine tailings is disclosed. Magnetically attractable collection units containing an ion exchange or sorbent media with an affinity for a chosen target substance are distributed in the sediments or tailings. After a period of time has passed sufficient for the particles to bind up the target substances, a magnet drawn through the sediments or across the tailings retrieves the units along with the target substance.

Dawson, Gaynor W. (Richland, WA); Mercer, Basil W. (Pasco, WA)

1979-01-01

422

Lake Tahoe Data Clearinghouse  

NSDL National Science Digital Library

The US Forest Service, Natural Resource and Conservation Service (NRCS), the USGS, and the Environmental Protection Agency (EPA) have worked together to provide the public with Lake Tahoe Basin data. Data include digital information from the USGS and watershed information from the EPA. Other data are available from regional agencies. Soils data from the NRCS are currently not available but are expected by the end of 1998.

423

Heterotrophic bacterioplankton control on organic and inorganic carbon cycle in stratified and non-stratified lakes of NW Russia  

NASA Astrophysics Data System (ADS)

Lakes of boreal zone regulate the fate of dissolved carbon, nutrients and trace metals during their transport from the watershed to the ocean. Study of primary production - mineralization processes in the context of carbon biogeochemical cycle allows determination of the rate and mechanisms of phytoplankton biomass production and its degradation via aquatic heterotrophic bacteria. In particular, comparative study of vertical distribution of Dissolved Organic Carbon (DOC) in stratified and non-stratified lakes allows establishing the link between biological and chemical aspects of the carbon cycle which, in turns, determines an environmental stability and recovering potential of the entire ecosystem. In order to better understand the biogeochemical mechanisms that control dissolved organic and inorganic carbon migration in surface boreal waters, we studied in 2007-2009 two strongly stratified lakes (15-20 m deep) and two shallow lakes (2-4 m deep) in the Arkhangelsk region (NW Russia, White Sea basin). We conducted natural experiments of the lake water incubation for measurements of the intensity of production/mineralization processes and we determined vertical concentration of DOC during four basic hydrological seasons (winter and summer stratification, and spring and autumn lake overturn). Our seasonal studies of production/mineralization processes demonstrated high intensity of organic matter formation during summer period and significant retard of these processes during winter stagnation. During spring period, there is a strong increase of bacterial destruction of the allochtonous organic matter that is being delivered to the lake via terrigenous input. During autumn overturn, there is a decrease of the activity of phytoplankton, and the degradation of dead biomass by active bacterial community. Organic matter destruction processes are the most active in Svyatoe lake, whereas in the Beloe lake, the rate of organic matter production is significantly higher than its bacterial degradation, and in the Maselgskoe lake the aerobic mineralization plays insignificant role. Seasonally-stratified lake Svyatoe demonstrates systematic decrease of DOC concentration from the surface to the bottom horizon during summer and winter stagnation, whereas lake Maselgskoe exhibits an increase of DOC in the bottom horizons during winter stratification. During the autumn and spring overturn, we observe rather constant concentration of DOC due to well mixing of the water masses and low activity of the phytoplankton community. Results of the present work allow the evaluation of biotic and abitioc components of the biogeochemical cycle of carbon in small stratified and non-stratified lakes of the Arctic Ocean basin. They allow quantification of the direct link between the processes of primary production/heterotrophic bacteria mineralization and vertical profile of organic and inorganic carbon concentration.

Shirokova, Liudmila; Vorobjeva, Taissia; Zabelina, Svetlana; Moreva, Olga; Klimov, Sergey; Shorina, Natalja; Chupakov, Artem; Pokrovsky, Oleg; Audry, Stephan; Viers, Jerome

2010-05-01

424

Geology of Crater Lake  

NSDL National Science Digital Library

The Geology of Crater Lake is a resource for an introductory course on the geology of Mount Mazama and the Crater Lake caldera. The actual course consists of two evening presentations and a one-day field trip. The presentations outline the mountain's geologic setting, eruptive history, and potential hazards. The field trip affords an opportunity to examine volcanic and glacial features around the caldera rim and to explore one of the most spectacular lakes in the world. Upon successful completion of this course a student will be capable of the following: to describe the geologic setting of Mount Mazama and the other Cascade volcanoes; to identify andesite, dacite, and basalt and explain how the compositions of the lavas that form these rocks influence their eruptive characters; and to outline the major types of hazards that future eruptions of Mount Mazama may pose to regional communities. Along with a course syllabus, a bibliography and related links are available. Those registered for the course can visit the Gradebook to view their marks.

Hirt, William

425

Predicting Maximum Lake Depth from Surrounding Topography  

Microsoft Academic Search

Information about lake morphometry (e.g., depth, volume, size, etc.) aids understanding of the physical and ecological dynamics of lakes, yet is often not readily available. The data needed to calculate measures of lake morphometry, particularly lake depth, are usually collected on a lake-by-lake basis and are difficult to obtain across broad regions. To span the gap between studies of individual

Jeffrey W. Hollister; W. Bryan Milstead; M. Andrea Urrutia; Guy J.-P. Schumann

2011-01-01

426

Development of Vertical Cable Seismic System  

NASA Astrophysics Data System (ADS)

In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by Institute of Industrial Science, the University of Tokyo. It generates high frequency acoustic waves around 1kHz. The acquired VCS data clearly shows the reflections and currently being processed for imaging the subsurface structure.

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2011-12-01

427

RHIC VERTICAL AC DIPOLE COMMISSIONING.  

SciTech Connect

The RHIC vertical ac dipole was installed in the summer of 2001. The magnet is located in the interaction region between sector 3 and sector 4 common to both beams. The resonant frequency of the ac dipole was first configured to be around half of the beam revolution frequency to act as a spin flipper. At the end of the RHIC 2002 run, the ac dipole frequency was reconfigured for linear optics studies. A 0.35 mm driven betatron oscillation was excited with the vertical ac dipole and the vertical betatron functions and phase advances at each beam position monitor (BPM) around the RHIC yellow ring were measured using the excited coherence. We also recorded horizontal turn-by-turn beam positions at each BPM location to investigate coupling effects. Analysis algorithms and measurement results are presented.

BAI,M.; DELONG,J.; HOFF,L.; PAI,C.; PEGGS,S.; PIACENTINO,J.; OERTER,B.; ODDO,P.; ROSER,T.; SATOGATA,T.; TRBOJEVIC,D.; ZALTSMAN,A.

2002-06-02

428

Unraveling the complex local-scale flows influencing ozone patterns in the southern Great Lakes of North America  

NASA Astrophysics Data System (ADS)

This study examines the complexity of various processes influencing summertime ozone levels in the southern Great Lakes region of North America. Results from the Border Air Quality and Meteorology (BAQS-Met) field campaign in the summer of 2007 are examined with respect to land-lake differences and local meteorology using a large array of ground-based measurements, aircraft data and simulation results from a high resolution (2.5 km) regional air-quality model, AURAMS. Analyses of average ozone mixing ratio from the entire BAQS-Met intensive campaign period support previous findings that ozone levels are higher over the southern Great Lakes than over the adjacent land. However, there is great heterogeneity in the spatial distribution of surface ozone over the lakes, particularly over Lake Erie during the day, with higher levels located over the southwestern end of the lake. Results suggest that some of these increased ozone levels are due to local emission sources in large nearby urban centers. The land-lake differences in ozone mixing ratios are most pronounced during the night in a shallow inversion layer of about 200 m above the surface. After sunrise, these differences have a limited effect on the total mass of ozone over the lakes during the day time, though they may cause elevated ozone levels in the lake breeze air. A large reservoir layer of ozone is predicted by the AURAMS model over Lake Erie at night, centered between 600-1000 m above ground and extending into the land over Cleveland. The model also predicts a vertical circulation during the day with an updraft over Detroit-Windsor and downdraft over Lake St. Clair, which transports ozone up to 1500 m above ground and results in high ozone over the lake. Oscillations in ground level ozone mixing ratios were observed on several nights and several ground monitoring sites, with amplitudes of up to 40 ppbv and time periods of 15-40 min.

Levy, I.; Makar, P. A.; Sills, D.; Zhang, J.; Hayden, K. L.; Mihele, C.; Narayan, J.; Moran, M. D.; Sjostedt, S.; Brook, J.

2010-08-01

429

Glacioisostasy and Lake-Level Change at Moosehead Lake, Maine  

USGS Publications Warehouse

Reconstructions of glacioisostatic rebound based on relative sea level in Maine and adjacent Canada do not agree well with existing geophysical models. In order to understand these discrepancies better, we investigated the lake-level history of 40-km-long Moosehead Lake in northwestern Maine. Glacioisostasy has affected the level of Moosehead Lake since deglaciation ca. 12,500 14C yr B.P. Lowstand features at the southeastern end and an abandoned outlet at the northwestern end of the lake indicate that the lake basin was tilted down to the northwest, toward the retreating ice sheet, by 0.7 m/km at 10,000 14C yr B.P. Water level then rose rapidly in the southeastern end of the lake, and the northwestern outlet was abandoned, indicating rapid relaxation of landscape tilt. Lowstand features at the northwestern end of the lake suggest that the lake basin was tilted to the southeast at ca. 8750 14C yr B.P., possibly as the result of a migrating isostatic forebulge. After 8000 14C yr B.P., water level at the southeastern end was again below present lake level and rose gradually thereafter. We found no evidence suggesting that postglacial climate change significantly affected lake level. The rebound history inferred from lake-level data is consistent with previous interpretations of nearby relative sealevel data, which indicate a significantly steeper and faster-moving ice-proximal depression and ice-distal forebulge than geophysical models predict. ?? 1998 University of Washington.

Balco, G.; Belknap, D. F.; Kelley, J. T.

1998-01-01

430

Long-term Observations of Crater Lake, Oregon: Energy, Carbon, and Nutrient Cycles in an Ultra-oligotrophic Ecosystem  

NASA Astrophysics Data System (ADS)

Large, deep lakes offer a unique resource for the study of the interaction of the atmosphere and aquatic biogeochemical cycles. The remarkable properties of Crater Lake result in the vertical stratification of the ecosystem reminiscent of pelagic marine systems. This ultraoligotrophic lake provides a powerful natural laboratory to study the coupling of biological processes, element cycles, and the physics of the environment. Over 20 years ago, Jack Dymond established a long-term, high-resolution biogeochemical study, including sediment traps, which today provides a powerful tool to constrain processes operating over seasonal and interannual time scales. These studies enable the validation of appropriate process models, leading to a better predictive capacity in this and other large aquatic ecosystems. - We have demonstrated and modeled relationships between climate-driven vertical mixing and the upwelling of hypolimnetic nitrogen into the euphotic zone. The impacts of this nitrogen on the ecosystem are complex and are not simply reflected in export production. - The lake edges are a locus of this vertical mixing, and mass balance calculations suggest they support elevated primary production which must contribute significant particulate organic matter to the interior hypolimnion. - The extended time-series observations have allowed us to observe interannual variations in vertical mixing, deep water ventilation, and the accumulation of salt and nitrogen. - The observations have constrained models of lake physics which help evaluate the first-order impact of climate change scenarios. A nitrogen-based ecosystem model has been coupled to the physical model and validated against biological time series observations. - The functioning of large lake ecosystems are finally reflected in their sediments and may provide one of the most powerful paleorecords of climate variability on the continents.. Because Crater Lake is the centerpiece of one of the premier National Parks in the USA, it provides a unique setting to directly engage the public with compelling educational experiences demonstrating the function of complex aquatic ecosystems and the methods of interdisciplinary field research.

Collier, R.; Crawford, G.; Fennel, K.; Larson, G.; Buktenica, M.; Dymond, J.

2004-12-01

431

Measurements of vertical bar Vcb vertical bar and vertical bar Vub vertical bar at BaBar  

SciTech Connect

We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical bar Vub vertical bar matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.

Rotondo, M. [Dipartimento di Fisica Galileo Galilei, Via Marzolo 8, Padova 35131 (Italy)

2005-10-12

432

Lake-atmosphere exchanges: the LATEX field experimental campaign  

NASA Astrophysics Data System (ADS)

Understanding the interaction of the atmosphere with underlying water surfaces is of great importance for a wide range of scientific fields such as water resources management, climate simulations and change impact studies, and regional weather forecasting in coastal areas. However, atmospheric dynamics over water surfaces have generally received less attention than land-atmosphere interactions, partially due to logistical difficulties in operating in-situ field studies. The Lake-Atmosphere Turbulent EXchanges (LATEX) field measurement was designed to address the issues of air-water interactions over lakes. The experiment was performed over Lake Geneva (Switzerland) on a 10 meter high tower situated 100 meters offshore. The main instrumentation consisted of a vertical array of four sonic anemometers and four open path gas analyzers measuring wind speed, temperature, and humidity at 20 Hz. Additional supporting measurements included net radiation, water surface temperature, relative humidity and temperature of air, and wave height and speed. The diurnal trends of momentum, heat, and water vapor fluxes for the whole experimental period are presented and several evaporation models of varying complexity are tested. A new model based on the Penman approach and sensible heat flux measurement is also proposed and tested. The roughness lengths of the surface (for momentum, heat, and water vapor) are investigated. The focus is then turned to the coherent structures over the lake and results from a quadrant analysis for momentum, heat and water vapor fluxes are analyzed. Under neutral and stable stratification, ejections and sweeps contribute equally to the vertical fluxes; as the atmospheric boundary layer turns to unstable, ejections begin to clearly dominate.

Bou-Zeid, E.; Vercauteren, N.; Huwald, H.; Lemmin, U.; Selker, J.; Parlange, M. B.

2008-12-01

433

Biology of young lake trout (Salvelinus namaycush) in Lake Michigan  

USGS Publications Warehouse

Experimental fishing with gill nets of 5 mesh sizes (2 3/8 to 3 inches) in Lake Michigan in 1930-32 yielded more than 16,000 young lake trout. Data are presented here on age, growth, length-weight relationship, abundance, geographical and bathymetric distribution, and other details of their biology.

Van Oosten, John; Eschmeyer, Paul H.

1956-01-01

434

The Honey Lake fault zone, northeastern California: Its nature, age, and displacement  

SciTech Connect

The Honey Lake fault zone of northeastern California is composed of en echelon, northwest trending faults that form the boundary between the Sierra Nevada and the Basin Ranges provinces. As such the Honey Lake fault zone can be considered part of the Sierra Nevada frontal fault system. It is also part of the Walker Lane of Nevada. Faults of the Honey Lake zone are vertical with right-lateral oblique displacements. The cumulative vertical component of displacement along the fault zone is on the order of 800 m and right-lateral displacement is at least 10 km (6 miles) but could be considerably more. Oligocene to Miocene (30 to 22 Ma) age rhyolite tuffs can be correlated across the zone, but mid-Miocene andesites do not appear to be correlative indicating the faulting began in early to mid-Miocene time. Volcanic rocks intruded along faults of the zone, dated at 16 to 8 Ma, further suggest that faulting in the Honey Lake zone was initiated during mid-Miocene time. Late Quaternary to Holocene activity is indicated by offset of the 12,000 year old Lake Lahontan high stand shoreline and the surface rupture associated with the 1950 Fort Sage earthquake.

Wagner, D.L.; Saucedo, G.J.; Grose, T.L.T.

1990-01-01

435

PCB concentrations in lake trout (Salvelinus namaycush) are correlated to habitat use and lake characteristics.  

PubMed

This study considers the importance of lake trout habitat as a factor determining persistent organochlorine (OC) concentration. Lake trout is a stenothermal, cold water species and sensitive to hypoxia. Thus, factors such as lake depth, thermal stratification, and phosphorus enrichment may determine not only which lakes can support lake trout but may also influence among-lake variability in lake trout population characteristics including bioaccumulation of OCs. A survey of 23 lakes spanning much of the natural latitudinal distribution of lake trout provided a range of lake trout habitat to test the hypothesis that lake trout with greater access to littoral habitat for feeding will have lower concentrations of OCs than lake trout that are more restricted to pelagic habitat. Using the delta13C stable isotope signature in lake trout as an indicator of influence of benthic littoral feeding, we found a negative correlation between lipid-corrected delta13C and sigmaPCB concentrations supporting the hypothesis that increasing accessto littoral habitat results in lower OCs in lake trout. The prominence of mixotrophic phytoplankton in lakes with more contaminated lake trout indicated the pelagic microbial food web may exacerbate the biomagnification of OCs when lake trout are restricted to pelagic feeding. A model that predicted sigmaPCB in lake trout based on lake area and latitude (used as proximate variables for proportion of littoral versus pelagic habitat and accessibility to littoral habitat respectively) explained 73% of the variability in sigmaPCBs in lake trout in the 23 lakes surveyed. PMID:19068800

Guildford, S J; Muir, D C G; Houde, M; Evans, M S; Kidd, K A; Whittle, D M; Drouillard, K; Wang, X; Anderson, M R; Bronte, C R; Devault, D S; Haffner, D; Payne, J; Kling, H J

2008-11-15

436

Vertical Integration: Networks, and Markets  

Microsoft Academic Search

The organization of supply relations varies across industries. This paper builds a theoretical framework to compare three alternative supply structures: vertical integration, networks, and markets. The analysis considers the relationship between uncertainty in demand for specific inputs, investment costs, and industrial structure. It shows that network structures are more likely when productive assets are expensive and firms experience large idiosyncratic

Rachel E. Kranton; Deborah F. Minehart

1999-01-01

437

Freezing in a vertical tube  

Microsoft Academic Search

Fundamental heat transfer experiments were performed for freezing of an initially superheated or nonsuperheated liquid in a cooled vertical tube. Measurements were made which yielded information about the freezing front and the frozen mass, about the various energy components extracted from the tube, and about the decay of the initial liquid superheat. Four component energies were identified and evaluated from

E. M. Sparrow; J. A. Broadbent

1983-01-01

438

Vertical tube liquid pollutant separators  

Microsoft Academic Search

A plurality of elongated hollow, circular, foraminous substantially vertical tubes contiguously stacked transversely to the direction flowing liquid such as waste water containing foreign matter, I.E., settable solids and free oil, in a coalescer-separator apparatus provide a filter body providing for significant surface area contact by the liquid on both inside and outside surfaces of the tubes to entrap the

1982-01-01

439

Vertical integration in group learning  

Microsoft Academic Search

This paper is mainly concerned with the teaching of Computer Science to first year (freshman) students. The method outlined is an attempt to change their generally 'convergent' attitudes into a more 'divergent' way of tackling problems. One of the most wasteful features of modern education is the vertical separation of students, so that the collective wisdom acquired by one generation

R. D. Parslow

1980-01-01

440

Control of vertically polarized glare.  

PubMed

Reflected glare often interferes with vision. Since such glare is usually polarized it can be controlled with polarizers. The use of polarized filters to eliminate vertically polarized glare from blackboards and glossy printed material is presented. Practical means for the construction of such filters are discussed. PMID:6863803

Peli, E

1983-05-01

441

Vertical Instability at IPNS RCS.  

SciTech Connect

The rapid cycling synchrotron (RCS) of the intense pulsed neutron source (IPNS) at ANL accelerates > 3.0 times 10{sup 12} protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During the acceleration cycle, the rf frequency varies from 2.21 MHz to 5.14 MHz. Presently, the beam current is limited by a vertical instability. By analyzing turn-by-turn beam position monitor (BPM) data, large- amplitude mode 0 and mode 1 vertical beam centroid oscillations were observed in the later part of the acceleration cycle. The oscillations start in the tail of the bunch, build up, and remain localized in the tail half of the bunch. This vertical instability was compared with a head-tail instability that was intentionally induced in the RCS by adjusting the trim sextupoles. It appears that our vertical instability is not a classical head-tail instability [1]. More data analysis and experiments were performed to characterize the instability.

Wang, S.; Brumwell, F. R.; Dooling, J. C.; Harkay, K. C.; Kustom, R.; McMichael, G. E.; Middendorf, M. E.; Nassiri, A.; Accelerator Systems Division (APS)

2008-01-01

442

Quantum well vertical cavity laser  

SciTech Connect

This patent describes an apparatus which comprises: quantum well laser vertical cavity structure for lasing in a direction non-parallel to the major dimensions of a quantum well, such laser consisting essentially of an active element containing one or two quantum wells and a cavity dependent upon reflectance as between two distributed feedback mirrors.

Huang, R.F.; Jewell, J.L.; McCall, S.L. Jr.; Tai, K.

1991-03-12

443

Crystal Lake, Montcalm County, Michigan.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1975-01-01

444

Lake Tarpon, Pinellas County, Florida.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1977-01-01

445

Lake Como 1991 Reservoir Survey.  

National Technical Information Service (NTIS)

This report presents the results of the first extensive survey of Lake Como by Reclamation since construction of Como Dam. The primary objective of the 1991 survey was to gather necessary data for computing the current total and active capacities of Lake ...

R. L. Ferrari

1992-01-01

446

Hayden Lake, Kootenai County, Idaho.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1977-01-01

447

The Great Lakes Food Web.  

ERIC Educational Resources Information Center

|Presents a play for students in grades four to nine that incorporates the scientific names, physical characteristics, feeding habits, interactions, and interdependence of the plants and animals that make up the Great Lakes food web to facilitate the learning of this complex system. Includes a Great Lakes food web chart. (AIM)|

Baker, Marjane L.

1997-01-01

448

TROPHIC EQUILIBRIUM OF LAKE WASHINGTON  

EPA Science Inventory

Sewage effluent was diverted progressively from Lake Washington during 1963-1968, and the chemical conditions changed in close relation to the amount of sewage entering. The total phosphorus content of the lake decreased rapidly to 1971 after which year it varied around a value o...

449

Seeley Lake, Missoula County, Montana.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1977-01-01

450

Winona Lake, Kosciusko County, Indiana.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1976-01-01

451

LAKE RESTORATION BY SEDIMENT REMOVAL  

EPA Science Inventory

Fresh water lake sediment removal is usually undertaken to deepen a lake and increase its volume to enhance fish production, to remove nutrient rich sediment, to remove toxic or hazardous material, or to reduce the abundance of rooted aquatic plants. Review of more than 60 projec...

452

GREAT LAKES WATER QUALITY IMPROVEMENT  

EPA Science Inventory

This paper outlines and evaluates phosphorus loadings in the Great Lakes and suggests a strategy for its control. he municipal industrial and commercial and agricultural contribution use to the Great Lakes waters has led to a concomitant deterioration of the water quality. e must...

453

PYRAMID LAKE RENEWEABLE ENERGY PLAN  

SciTech Connect

The Pyramid Lake Renewable Energy Plan covers these areas: energy potential (primarily focusing on geothermal resource potential, but also more generally addressing wind energy potential); renewable energy market potential; transmission system development; geothermal direct use potential; and business structures to accomplish the development objectives of the Pyramid Lake Paiute Tribe.

HIGH DESERT GEOCULTURE, LLC

2009-06-06

454

Lake Minnetonka, Hennepin County, Minnesota.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1975-01-01

455

Materials Budgets of Lake Champlain.  

National Technical Information Service (NTIS)

The objectives of the report were to ascertain the general water quality status of the tributaries discharging into Lake Champlain and to estimate the materials input to the lake. Water samples were collected from about 40 tributaries during the period 19...

E. B. Henson M. Potash

1976-01-01

456

Pruess Lake, Millard County, Utah.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1977-01-01

457

Spirit Lake, Dickinson County, Iowa.  

National Technical Information Service (NTIS)

Annual total phosphorus and total nitrogen loadings to the lake were estimated and subdivided according to either point or non-point source origin. An assessment of the lake's trophic condition and limiting nutrient is also provided. All data collected by...

1976-01-01

458

Estimating Potential Yeild and Harvest of Lake Trout 'Salvelinus namaycush' in Minnesota's Lake Trout Lakes, Exclusive of Lake Superior.  

National Technical Information Service (NTIS)

Given that lake trout are highly sought-after and are a limited resource in Minnesota, lake trout populations that may be stressed should be identified. They should be considered for greater protection from over-exploitation by anglers, and greater protec...

G. D. Siesennop

2000-01-01

459

Bernicle Geese on Coniston Lake  

Microsoft Academic Search

THIS afternoon while walking by this lake I saw four large birds flying overhead. These birds, after making several circuits in the air, pitched on the lake. I had with me an excellent pair of field-glasses, and as I succeeded in approaching within 20 yards of them, I was enabled to examine them with sufficient accuracy to convince me that

William R. Melly

1888-01-01

460

Radionuclides in Mono Lake, California  

Microsoft Academic Search

Several radioisotopes of the naturally occurring uranium and thorium decay series, in addition to fallout plutonium, have unusually high concentrations in the water column of Mono Lake, a natural alkaline, saline lake. Complexing by carbonate ions appears to be responsible for the enhanced solubility of actinide elements with oxidation states of IV to VI. In contrast, fallout strontium-90 has been

H. J. Simpson; R. M. Trier; J. R. Toggweiler; G. Mathieu; B. L. Deck; C. R. Olsen; D. E. Hammond; C. Fuller; T. L. Ku

1982-01-01