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1

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

2

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

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

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

5

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

6

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

7

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

8

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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

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

18

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.

19

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

20

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

21

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

22

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

23

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

24

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

25

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

26

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

27

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

28

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

29

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

30

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

31

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

32

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

33

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

34

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

35

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

36

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

37

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

38

Coping With Lake Kivu, East Africa  

Microsoft Academic Search

Workshop on Tropical Rift Lake Systems: Integrated Volcanogenic, Tectonic, Biogeochemical, and Geohazard Assessment of Lake Kivu; Gisenyi, Rwanda, 13-15 January 2010; Situated in the volcanic highlands of the East African Rift Valley's western branch, Lake Kivu contains one of the most unusual and fascinating aquatic ecosystems on the planet. Bottom waters in the 480-meter-deep lake are warmer and saltier than

Thomas C. Johnson; Christopher A. Scholz

2010-01-01

39

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

40

7. View southwest, east facade of Lake Forest (original Forest ...  

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

7. View southwest, east facade of Lake Forest (original Forest Cottage structure incorporated into renamed structure) - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

41

5. View north, south and east facade of Lake Forest ...  

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

5. View north, south and east facade of Lake Forest (original Forest Cottage structure incorporated into renamed structure) - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

42

200 MAIN STREET, SALT LAKE CITY, UT. VIEW LOOKING EAST ...  

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

200 MAIN STREET, SALT LAKE CITY, UT. VIEW LOOKING EAST OF "MAIN' STREET. REPHOTOGRAPH OF HISTORIC SHIPLER PHOTO # 18273, UTAH STATE HISTORICAL SOCIETY COLLECTION. - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

43

INTERSECTION OF 445 NORTH & 1040 EAST, SALT LAKE CITY, ...  

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

INTERSECTION OF 445 NORTH & 1040 EAST, SALT LAKE CITY, UT. VIEW LOOKING SOUTH. REPHOTOGRAPH OF HISTORIC SHIPLER PHOTO # 18272, UTAH STATE HISTORICAL SOCIETY COLLECTION. - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

44

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

45

PLAT X41601 EAST (SALT LAKE CITY CEMETERY LOCATER), SALT LAKE ...  

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

PLAT X-4-160-1 EAST (SALT LAKE CITY CEMETERY LOCATER), SALT LAKE CITY, UT. VIEW LOOKING SOUTH AT CEMETERY BETWEEN OLIVE STREET (1020 EAST) AND 1000 EAST STREET, REPHOTOGRAPH OF HISTORIC SHIPLER PHOTO # 12049, UTAH STATE HISTORICAL SOCIETY COLLECTION. - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

46

IDEAL Symposium on the East African Lakes  

NASA Astrophysics Data System (ADS)

A vast array of interdisciplinary problems presented by the African Great Lakes were highlighted at the International Symposium on the Limnology, Climatology and Paleoclimatology of the East African Lakes, organized by the International Decade for the East African Lakes (IDEAL) February 17-21 in Jinja, Uganda. Approximately 125 scientists attended from North America, Europe, Africa, and New Zealand. Jinja is located on the northern shore of Lake Victoria at the head-waters of the Nile and is the site of the host institution for the symposium, the Uganda Freshwater Fisheries Research Organization (UFFRO). The conveners of the symposium were Tom Johnson of Duke University, George Kitaka of UNESCO-ROSTA, and Eric Odada of the University of Nairobi.

Johnson, T. C.; Kelts, K.; Lehman, J. T.; Wuest, A.

47

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

48

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

49

Recent rapid salinity rise in three East Antarctic lakes  

Microsoft Academic Search

Research in East Antarctica has shown several recent environmental changes that may be linked to human impacts on climate. In order to detect the influence and context of these changes on coastal aquatic ecosystems we examined lake sediment cores from three lakes in the Windmill Islands, East Antarctica; Beall Lake, Holl Lake and ?8Lake M?9. Cores were sectioned at?2.5 mm intervals.

Donna Roberts; Dominic A. Hodgson; Andrew McMinn; Elie Verleyen; Bruce Terry; Christine Corbett; Wim Vyverman

2006-01-01

50

Coping With Lake Kivu, East Africa  

NASA Astrophysics Data System (ADS)

Workshop on Tropical Rift Lake Systems: Integrated Volcanogenic, Tectonic, Biogeochemical, and Geohazard Assessment of Lake Kivu; Gisenyi, Rwanda, 13-15 January 2010; Situated in the volcanic highlands of the East African Rift Valley's western branch, Lake Kivu contains one of the most unusual and fascinating aquatic ecosystems on the planet. Bottom waters in the 480-meter-deep lake are warmer and saltier than its surface waters. The concentrations of dissolved carbon dioxide and methane are so high in the deep water that catastrophic overturn, an abrupt upwelling of deep water and gas driven by the buoyancy of expanding gas bubbles as they rise from the depths, could well happen in the coming century. Were this to occur, human fatalities would likely number in the hundreds of thousands—a disaster similar to what occurred when Lake Nyos (Cameroon) in 1986 emitted a large amount of carbon dioxide, causing hundreds of local residents to suffocate—but with orders-of-magnitude more gas release.

Johnson, Thomas C.; Scholz, Christopher A.

2010-07-01

51

SEXTON'S HOUSE. 200 NORTH N STREET (895 EAST), SALT LAKE ...  

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

SEXTON'S HOUSE. 200 NORTH N STREET (895 EAST), SALT LAKE CITY, UT. VIEW OF THE NORTHEAST. REPHOTOGRAPH OF HISTORIC SHIPLER PHOTO # 18996, UTAH STATE HISTORICAL SOCIETY COLLECTION. - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

52

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

53

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

54

Influx of meltwater to subglacial Lake Concordia, East Antarctica  

Microsoft Academic Search

We present evidence for melting at the base of the ice that overlies Lake Concordia, an 800 km2 subglacial lake near Dome Concordia, East Antarctica, via a combination of glaciohydraulic melting (associated with the tilted ice ceiling and its influence on lake circulation\\/melting temperature) and melting by extreme strain heating (where the ice sheet is grounded). An influx of water

Anahita A. Tikku; Robin E. Bell; Michael Studinger; Garry K. C. Clarke; Ignazio Tabacco; Fausto Ferraccioli

2005-01-01

55

Does water hyacinth on East African lakes promote cholera outbreaks?  

PubMed

Cholera outbreaks continue to occur regularly in Africa. Cholera has been associated with proximity to lakes in East Africa, and Vibrio cholerae has been found experimentally to concentrate on the floating aquatic plant, water hyacinth, which is periodically widespread in East African lakes since the late 1980s. From 1994 to 2008, Nyanza Province, which is the Kenyan province bordering Lake Victoria, accounted for a larger proportion of cholera cases than expected by its population size (38.7% of cholera cases versus 15.3% of national population). Yearly water-hyacinth coverage on the Kenyan section of Lake Victoria was positively associated with the number of cholera cases reported in Nyanza Province (r = 0.83; P = 0.0010). Water hyacinth on freshwater lakes might play a role in initiating cholera outbreaks and causing sporadic disease in East Africa. PMID:20682884

Feikin, Daniel R; Tabu, Collins W; Gichuki, John

2010-08-01

56

Does Water Hyacinth on East African Lakes Promote Cholera Outbreaks?  

PubMed Central

Cholera outbreaks continue to occur regularly in Africa. Cholera has been associated with proximity to lakes in East Africa, and Vibrio cholerae has been found experimentally to concentrate on the floating aquatic plant, water hyacinth, which is periodically widespread in East African lakes since the late 1980s. From 1994 to 2008, Nyanza Province, which is the Kenyan province bordering Lake Victoria, accounted for a larger proportion of cholera cases than expected by its population size (38.7% of cholera cases versus 15.3% of national population). Yearly water-hyacinth coverage on the Kenyan section of Lake Victoria was positively associated with the number of cholera cases reported in Nyanza Province (r = 0.83; P = 0.0010). Water hyacinth on freshwater lakes might play a role in initiating cholera outbreaks and causing sporadic disease in East Africa.

Feikin, Daniel R.; Tabu, Collins W.; Gichuki, John

2010-01-01

57

A BAC library of the East African haplochromine cichlid fishAstatotilapia burtoni  

Microsoft Academic Search

A BAC library was constructed from Astatotilapia burtoni, a haplochromine cichlid that is found in Lake Tanganyika, East Africa, and its surrounding rivers. The library was generated from genomic DNA of blood cells and comprises 96,768 individual clones. Its median insert size is 150kb and the coverage is expected to represent about 14 genome equivalents. The coverage evaluation was based

Michael Lang; Tsutomu Miyake; Ingo Braasch; Deborah Tinnemore; Nicol Siegel; Walter Salzburger; Chris T. Amemiya; Axel Meyer

2006-01-01

58

Basin neotectonics of Lakes Edward and George, East African Rift  

Microsoft Academic Search

The Edward and George lake basins are located in the western branch of the East African Rift System (EARS). Both basins occupy half grabens with the main boundary fault located in the west and are separated by a high relief accommodation zone. This structural high formed where the NNE–SSW trend of the Miocene rifting and NW–SE oriented basement lineaments interfere.

Tine Lærdal; Michael R Talbot

2002-01-01

59

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

60

330 NORTH & CENTER STREET (990 EAST) (8E1684E, SALT LAKE ...  

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

330 NORTH & CENTER STREET (990 EAST) (8-E-16-8-4E, SALT LAKE CITY CEMETERY LOCATER), SALT LAKE CITY, UT. VIEW LOOKING SOUTHWEST OVER THE CEMETERY. - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

61

75 FR 34362 - Safety Zone; Festivals & Fireworks Celebration, East Moran Bay, Lake Huron, St. Ignace, MI  

Federal Register 2010, 2011, 2012, 2013

...USCG-2010-0452] RIN 1625-AA00 Safety Zone; Festivals & Fireworks Celebration, East Moran Bay, Lake Huron, St...a portion of Lake Huron during the Festivals & Fireworks Celebration fireworks display taking place on ten separate...

2010-06-17

62

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

63

Solar variability and the levels of Lake Victoria, East Africa, during the last millenium  

Microsoft Academic Search

A new diatom series with 1–6 year resolution from Lake Victoria, East Africa, shows that lake level minima occurred ca. 820–760, 680–660, 640–620, 370–340, and 220–150 calendar years BP. Inferred lake levels were exceptionally high during most of the ‘Little Ice Age’ (ca. 600–200 calendar years BP). Synchrony between East African high lake levels and prolonged sunspot minima during much of

J. Curt Stager; David Ryves; Brian F. Cumming; L. David Meeker; Juerg Beer

2005-01-01

64

Environmental magnetic responses of urbanization processes: evidence from lake sediments in East Lake, Wuhan, China  

NASA Astrophysics Data System (ADS)

We present a study on the environmental magnetic response to urbanization processes from nine sediment cores from East Lake in Wuhan, China. The concentration of magnetic particles, heavy metals and organic matter in the upper 2-18 cm of the sediment cores have been significantly elevated due to the input of coarse magnetite grains from industrial (e.g. power generation and steelmaking) and other anthropogenic activities (e.g. vehicle emissions). Concentration-related magnetic parameters, such as magnetic susceptibility (?), saturation isothermal remanent magnetization and anhysteretic remanent magnetization, are significantly correlated with concentration of heavy metals and organic matter, for example, Pearson's correlation coefficients are 0.921 for ?-Cu, 0.660 for ?-Pb and 0.848 for ?-loss-on-ignition, respectively. The magnetic properties of the lake sediments document the pollution history caused by human impact on the lake catchment during urbanization. The environmental quality of the lake was fairly good before the 1960s. Magnetic, heavy metal and organic matter contents of the sediments were low and relatively constant, which indicates relatively stable natural inputs from the lake catchment. Pollution trends since the 1960s are reflected in downcore magnetic property variations of the lake sediment. The concentration of magnetic particles in the lake sediments started to increase since 1957, when the Wuhan Iron and Steel Company and the Qingshan Thermal Power Plant, which are located upwind of the lake, were built and put into production. Lake pollution was further aggravated since the acceleration of industrialization and urbanization in East Lake area in the 1980s, which is verified by the elevated concentration of heavy metals and organic matter in the sediments. The magnetic mineral concentration in the lake sediment increased continuously until it peaked in the 1990s and has remained a high level since then. These results suggest that magnetic properties respond sensitively to environmental status, and that the magnetic properties of sediments can provide an excellent record of the industrial and anthropogenic history in an urban lake catchment.

Yang, Tao; Liu, Qingsheng; Zeng, Qingli; Chan, Lungsang

2009-11-01

65

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

66

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

67

Compaction and subsidence in Lake Maracaibo East Coast field  

SciTech Connect

The role of heavy crudes, extra-heavy crudes, and bitumens in Venezuelan reserves is presented and the importance of compaction/subsidence related to recoveries of these types of crudes is discussed. A very short review of discovery, development, and different exploitation phases and the geological and reservoir characteristics of the Lake Maracaibo East Coast fields is presented. Interpretations of the causes of the compaction and subsidence during natural depletion periods is discussion as well as reactivation of compaction/subsidence as a consequence of steam injection. Subsidence effects on environment are presented, and historical records and subsidence predictions are discussed. The approach to dykes stability multidisciplinary studies is indicated, including seismicity, geotechniques, oceanography, physical-mathematical modeling, and prediction aspects involved.

Sancevic, Z.A.; Boesi, T. (Maraven S.A., Caracas (Venezuela))

1990-05-01

68

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

69

The Human Dimensions Studies on the East African Lake Regions: A Review  

Microsoft Academic Search

Several studies have been carried out under the auspices of the IDEAL (International Decade for East African Lakes) programme\\u000a on the physical and biological factors affecting the East African lakes. These include aspects such as geological and sedimentary\\u000a processes, climate dynamics and variability, limnology, food webs and fisheries, and paleoenvironment. However, the human\\u000a dimensions research has not been part of

MARY MAGDALENE OPONDO

70

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

71

Egg banks in hypersaline lakes of the South-East Europe  

Microsoft Academic Search

The cyst banks of 6 coastal hypersaline lakes of South-East Europe have been investigated. The study concerned the bottom sediments of Khersonesskoe and Koyashskoe lakes in the Crimea (Ukraine), Nartë saltworks (Albania), Vecchia Salina at Torre Colimena (Apulia, Italy), Pantano Grande and Pantano Roveto at Vendicari (Sicily, Italy). A total of 19 cyst types were recognised. The cyst banks of

Salvatore Moscatello; Genuario Belmonte

2009-01-01

72

Late Holocene changes in ultraviolet radiation penetration recorded in an East Antarctic lake  

Microsoft Academic Search

Late Holocene changes in the ultraviolet radiation (UVR) penetration in a lake in the Larsemann Hills (East Antarctica) were reconstructed using sediment core proxies based on fossil pigments (scytonemins and its derivatives) and siliceous microfossils. The influence of changes in lake depth on the UVR proxy was excluded by applying a correction, based on the non-linear relation between modern scytonemin

Elie Verleyen; Dominic A. Hodgson; Koen Sabbe; Wim Vyverman

2005-01-01

73

Fish Faunal Resurgence in Lake Nabugabo, East Africa  

Microsoft Academic Search

In Lake Nabugabo, Uganda, a small satellite of the equatorial Lake Victoria, approximately 50% of the indigenous fish species disappeared from the open waters subsequent to establishment of the introduced predatory Nile perch ( Lates niloticus ). However, several of these species persisted in wetland refugia. Over the past decade, Nile perch in Lake Nabugabo have been intensively fished. Herein

Lauren J. Chapman; Colin A. Chapman; Pamela J. Schofield; John P. Olowo; Les Kaufman; Ole Seehausen; Richard Ogutu-Ohwayo

2003-01-01

74

Lake Qinghai Drilling Project: Evolution History of Lake Qinghai and East Asian Monsoon Changes since the Late Miocene  

NASA Astrophysics Data System (ADS)

As a closed continental lake on the north-east margin of the Tibetan Plateau, Lake Qinghai is sensitive to climate variations as well as the environmental effects of Plateau growth/uplift. Supported by Chinese funding agencies and ICDP, onshore and offshore lake cores were drilled in 2005. We compare our preliminary chronostratigraphic, sedimentologic, and geochemical results with climatic records from the Loess Plateau, South China Sea, Arctic and global oceans, and we discuss the evolution of Lake Qinghai at different time scales since the late Miocene. Lake Qinghai is shown to have intimate linkages with the warm/moist East Asian summer monsoon, the cold/dry East Asian winter monsoon, and the growth/uplift of the Tibetan Plateau. Magnetostratigraphic studies of the onshore drill cores indicate that thick greenish clays were deposited during Late Miocene, suggesting the initial formation of the Qinghai Lake basin. Consistent with proxies from the Loess Plateau and the South China Sea, they imply summer-monsoon strengthening and inland intrusion. These changes may be related to a growth event of the Tibetan Plateau at 10-8 Ma, which led to the uplift of Qinghai Nanshan, formation of faulted lake basins, and enhanced summer monsoon circulation. From 6 to 4.6Ma eolian red clays in the core indicate lake basin dessication, as Loess Plateau dust flux increased with the strengthening of the winter monsoon and coincident with intense Arctic ice rafting at 6-5 Ma. From 4.6 to 3.5 Ma thick greenish clays were deposited as modern Lake Qinghai formed. Significantly increased fluxes of TOC, C/N and total sediment might be related to uplift of Qinghai Nanshan and basin subsidence at that time, and they are coeval with the increasing strength of East Asian monsoon during early Pliocene. At 3.5-2.6 Ma, continued strengthening of the East Asian summer monsoon, inland aridification, and increases in global ice volume suggest another growth event of the Tibetan Plateau. Shallow-water silty clays were deposited in the lake basin at this time. Since 2.6 Ma, deposition in the basin was characterized by shallow-water silty clays, intercalated with layers of loess- like material, eolian sand, gravel, and sand, indicating multiple lake expansion/dessication cycles, presumably at orbital frequencies, reflecting multiple migrations of the East Asian summer monsoon front driven by solar radiation and global ice volume changes over this region. Several previous studies of cores as much as 7m long from the depositional basins of Lake Qinghai have documented monsoon climate and environmental changes at the lake from the deglacial period through the Holocene, which are generally consistent with northern Hemisphere summer insolation and its seasonality changes. A wide variety of proxies have been used, and some cores have been studied at very high temporal resolution, especially for the last several hundred years. Results suggest that solar activity influences decadal regional temperatures, and that it is the East Asian summer monsoon as opposed to the Indian summer monsoon that acts as the dominate moisture source at the decadal scale within the local region. Offshore GLAD800 drill cores obtained in 2005 sampled fine-grained sediments before encountering thick units of sand. The fine-grained sections are 2-3 times longer than previous cores from similar sites. Paleolimnological proxy studies are underway on these cores to extend the young part of the paleoenvironmental record back to significantly before the last glacial maximum.

An, Z.; Colman, S.

2007-12-01

75

Ice flow field over Lake Vostok, East Antarctica inferred by structure tracking  

NASA Astrophysics Data System (ADS)

Here, we present a flow field for the East Antarctic ice sheet over Lake Vostok based on tracking structures across the lake inherited from the western, upstream shoreline. The structures, distinctive peaks and troughs identified in the ice sheet internal layers, are imaged in ice-penetrating radar data collected in a systematic grid over the lake. These structures are resolved in three distinct internal layers at depths between 900 and 3750 m. Ridges in the internal layers are associated with prominent topographic highs along the western shoreline, and troughs are correlated with shoreline topographic lows. Lake Vostok is bisected by a topographic ice divide; south of this topographic divide the ice flow is dominantly NNW to SSE and north of the divide the ice flow is W to E. The flow over the lake is also deflected by the small (˜0.02%) southward lake surface slope. Accretion ice, lake water frozen to the bottom of the ice sheet, is preferentially imaged along flowlines emanating from topographic ridges. The coincidence of the accretion ice reflector with our flowlines both provides independent support for our new flow field, and suggests focused accretion along the western shoreline. Global positioning system (GPS) data provide additional independent support for our new flow field in the southern lake. The new flow field will be crucial for subsequent analyses of mass exchange between the ice sheet and the lake, identifying areas of melting above the lake and estimating residence times.

Tikku, Anahita A.; Bell, Robin E.; Studinger, Michael; Clarke, Garry K. C.

2004-11-01

76

Depositional environments of Late Triassic lake, east-central New Mexico  

SciTech Connect

The Redonda Member of the Chinle Formation represents deposition in a large, polymictic lake during the Late Triassic (Norian) in east-central New Mexico. This study documents and defines an extensive lacustrine system situated in western Pangaea which was influenced by both tectonic and climatic events. Areal extent of the lake may have been as much as 5,000 km{sup 2}.

Hester, P.M. (Bureau of Land Management, Albuquerque, NM (USA))

1989-09-01

77

Methane efflux from bubbles suspended in ice-covered lakes in Syowa Oasis, East Antarctica  

Microsoft Academic Search

This is the first estimation of methane efflux from bubbles in lake ice in Antarctica. Bubbles suspended in shallow ice in 20 lakes were observed as part of the operations of the 45th Japanese Antarctic Research Expedition in ice-free rocky areas along the eastern coast of Lützow-Holm Bay (Syowa Oasis) in East Antarctica in 2004. Anomalous methane concentrations in bubbles

Masafumi Sasaki; Satoshi Imura; Sakae Kudoh; Takashi Yamanouchi; Shinji Morimoto; Gen Hashida

2009-01-01

78

Air-lake exchange of methane during the open water season in Syowa Oasis, East Antarctica  

Microsoft Academic Search

Dissolved methane (DM) concentrations were measured in 17 lakes as part of the operations of the 45th Japanese Antarctic Research Expedition in ice-free rocky areas along the eastern coast of Lützow-Holm Bay (Syowa Oasis) in East Antarctica in the summer of 2003–2004. DM at the surfaces of 14 lakes ranged from the atmospheric equilibrium concentration (about 4 nmol L?1 for

Masafumi Sasaki; Noboru Endoh; Satoshi Imura; Sakae Kudoh; Takashi Yamanouchi; Shinji Morimoto; Gen Hashida

2010-01-01

79

Sunspots, El Niño, and the levels of Lake Victoria, East Africa  

Microsoft Academic Search

An association of high sunspot numbers with rises in the level of Lake Victoria, East Africa, has been the focus of many investigations and vigorous debate during the last century. In this paper, we show that peaks in the ?11-year sunspot cycle were accompanied by Victoria level maxima throughout the 20th century, due to the occurrence of positive rainfall anomalies

J. Curt Stager; Alexander Ruzmaikin; Declan Conway; Piet Verburg; Peter J. Mason

2007-01-01

80

Mercury Concentrations in Water, Sediment, and Biota from Lake Victoria, East Africa  

Microsoft Academic Search

Lake Victoria, East Africa, is the site of the world's most productive freshwater fishery. Mercury in muscle tissue of the 2+ and 3+ year old Nile perch (Lates niloticus), presently the largest constituent of the fishery, was 90 to 250 ng \\/g wet weight. This is similar to the range of mercury in fish muscle reported for the commercial fish

Patricia S. Ramlal; Fred W. B. Bugenyi; George W. Kling; Jerome O. Nriagu; John W. M. Rudd; Linda M. Campbell

2003-01-01

81

Calibration and application of the branched GDGT temperature proxy on East African lake sediments  

NASA Astrophysics Data System (ADS)

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a novel proxy for mean annual air temperature (MAAT) and have the potential to be broadly applicable to climate reconstruction using lacustrine sediments. Several calibrations have been put forth relating brGDGT distributions to MAAT using a variety of linear regressions, including the methylation (MBT) and cyclization (CBT) indices of brGDGTs, the relative abundances of the major, non-cyclized brGDGTs (MbrGDGTs), and best subsets regression (BSR) of the fractional abundances of the nine most common brGDGTs. However, these calibrations have rarely been applied to lake sediment cores to reconstruct temperatures and test the applicability of this proxy as a paleothermometer.We present an expanded East African lakes surface sediment brGDGT dataset based upon 111 lakes and examine three methods of calibrating brGDGTs to MAAT. These methods include recalculations of the East African lake MBT/CBT calibration and MbrGDGTs calibrations, as well as a new stepwise forward selection (SFS) calibration that uses the four combined brGDGTs that explain the most variance in temperature in our calibration set. We apply these new calibrations as well as five previously published lacustrine brGDGT calibrations to the brGDGT distributions of our surface sediment dataset and a 48 kyr sediment core from Sacred Lake, Mt. Kenya, producing the first brGDGT temperature reconstruction available from a small tropical lake. We compare the reconstructed temperatures to previously published paleotemperature records from East Africa to help us assess the performance of the brGDGT calibrations. We find that the SFS calibration has a consistently low root mean squared error of prediction (RMSEP) over the entire range of MAAT, while the MBT/CBT and MbrGDGT calibrations have relatively large RMSEPs, particularly between lakes with similar temperatures but variable pH. This suggests that these techniques do not properly deconvolve the temperature and pH signals recorded in the distributions of the brGDGTs. We further find that only the SFS calibration produces a credible reconstructed temperature history from Sacred Lake when compared to other last glacial maximum paleotemperature estimates from East Africa. Thus, we advocate for the use of the SFS calibration when reconstructing paleotemperatures from brGDGTs in East Africa.

Loomis, Shannon E.; Russell, James M.; Ladd, Bethany; Street-Perrott, F. Alayne; Sinninghe Damsté, Jaap S.

2012-12-01

82

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

83

Resource–consumer relationships in Lake Victoria, East Africa  

Microsoft Academic Search

Resource–consumer relationships in Lake Victoria were investigated by use of stable isotope data. d13C and d15N signatures were determined for organisms at a deep (22 m) and a littoral (5 m) site in the Napoleon Gulf near Jinja, Uganda. Results suggest that two food chains operate at the deep site, one leading from a shrimp (Caridina nilotica) to juvenile Nile

Donn K. Branstrator; Lucas Mwebaza-Ndawula; Joseph P. Montoya

2003-01-01

84

Pelagic Nitrogen Fixation in Lake Victoria (East Africa)  

Microsoft Academic Search

Between 1994 and 1998 biological nitrogen fixation was measured using the acetylene reduction method at inshore and offshore sites on northern Lake Victoria. Rates of biological N-fixation were high and often exceeded 0.5 ?g N\\/L\\/h. Average rates of volumetric N-fixation at optimal irradiance were 8 times higher at inshore locations than in the offshore. Rates of annual areal N-fixation, modeled

Rose Mugidde; Robert E. Hecky; Len L. Hendzel; William D. Taylor

2003-01-01

85

Strontium Isotopes as Palaeohydrological Tracers in the White Nile Headwater Lakes, East Africa  

NASA Astrophysics Data System (ADS)

Strontium isotopes (87Sr/86Sr) provide a powerful method for reconstructing ancient hydrological networks in East Africa where contrasting geological terrains yield surface runoff with distinctly different Sr-isotopic signatures. In particular, waters from catchments dominated by Archaean and Proterozoic basement rich in radiogenic 87Sr are readily distinguished from those derived from Cenozoic volcanic rocks characterised by low 87Sr/86Sr values. In an earlier study, the Sr-isotopic composition of shell carbonate and fish phosphate was used to show that water originating from Lake Victoria was making a major contribution to the flow of the White Nile at Khartoum by 13.5 cal. ka BP, following a prolonged period of low lake levels and reduced river discharge. Overflow of Victoria at that time is, however, still disputed. Lake Albert provides the critical link between Lake Victoria and the White Nile system, as Lake Victoria water must pass through Albert to reach the main Nile. In this study we use Sr-isotopes to resolve the timing of Victoria's overflow into Lake Albert by establishing a Sr-isotope stratigraphy for the latter waterbody. During the LGM, Lake Albert was a closed, possibly desiccated basin and high 87Sr/86Sr values indicate that it was completely isolated from Lakes Victoria and Edward. Refilling of the basin commenced at ca. 15 ka. Within 1000 years of the change to a positive water balance, a major excursion to lower 87Sr/86Sr values is recorded, indicating contact with Lakes Edward and Victoria. This age is consistent with previous evidence for Lake Victoria waters reaching the White Nile during the terminal Pleistocene. During the early Holocene, Lake Albert was strongly influenced by volcanic Sr, due either to high discharge from Lake Edward or local volcanic activity. The Sr-isotope record also confirms the existence of a hiatus in the Albert basin at ca. 4.6 - 5.8 ka, which was probably related to a lowstand. When sedimentation recommenced, the dominant inflow came initially from Lake Edward, suggesting that Lake Victoria may at this time have been closed. This was probably a major reason for the coeval records of low discharge in the middle and lower reaches of the Nile.

Talbot, M. R.; Brendeland, K. I.

2001-12-01

86

Lake Challa (Mt. Kilimanjaro) sediments as recorder of present and past seasonality in equatorial East Africa  

NASA Astrophysics Data System (ADS)

In discussions on the impact of global warming on moisture balance and human water resources, natural archives of past hydrological variability in tropical regions are attracting increasing attention. The EuroCLIMATE project CHALLACEA studies the sediment archive of Lake Challa, a 4.5 km² and ~94 m deep crater lake located on the lower eastern slope of Mt. Kilimanjaro with the aim to produce a continuous, high-resolution and multi-proxy reconstruction of past temperature and moisture-balance variability in equatorial East Africa over the past 25,000 years. Lake Challa is a freshwater lake with a water budget controlled mostly by sub-surface in- and outflow and lake-surface evaporation. Accordingly, microscopic thin-section investigation of sediment composition reveals an overall dominance of autochthonous components (diatom frustules, calcite, and organic matter). First results from an ongoing sediment trap study point to distinct seasonality in sediment input: calcite and organic matter accumulate during the warm southern hemisphere summer months (November - March), whereas the principal diatom blooms occur during the cool and windy period between June and October. Here we present the results of physical and chemical investigations of the lake water column between September 1999 and November 2007, which document the concomitant seasonal changes in lake mixing/stratification and related element cycling. High-resolution ?XRF profiles of these elements in the laminated sediments of Lake Challa thus also show marked seasonal cycles, as well as longer-term variability. In particular, variability in the Mn/Fe ratio along the top 15 cm of the sediment record is interpreted to reflect changes in lake stratification during the last ~100 years. This proxy record is evaluated in comparison with records of historical weather variability in East Africa, and of potentially influencing parameters such as the El Niño Southern Oscillation and the Indian Ocean Dipole. Eventually these exercises may contribute to high-resolution reconstruction of tropical East African climate variability over the last 25,000 years.

Kristen, I.; Wolff, C.; Schettler, G.; Dulski, P.; Naumann, R.; Haug, G. H.; Blaauw, M.; Verschuren, D.

2008-12-01

87

Environmental controls on branched tetraether lipid distributions in tropical East African lake sediments  

NASA Astrophysics Data System (ADS)

Quantifying past continental temperature changes is an important aspect of paleoclimate research as it allows us to constrain the amplitude of natural variability, test predictive climate models, and provide a proper context for changes that may arise in response to anthropogenically-induced climate change. The recently developed biomarker-based methylation index of branched tetraethers/cyclization ratio of branched tetraethers (MBT/CBT) proxy shows potential as a new method for continental temperature reconstruction, but thus far it has only been applied successfully in ocean margin sediments. To assess whether this proxy is also applicable to the sedimentary record in tropical lacustrine systems, we investigated the distribution of branched glycerol dialkyl glycerol tetraethers (GDGTs) in recently deposited sediments from 46 lakes in tropical East Africa. These lakes span a substantial range in surface elevation (770-4500 m above sea level), and thus also a wide gradient of mean annual temperature. We find that, saline lakes excepted, branched GDGTs are universally abundant in the lakes investigated and can be used to predict mean annual air temperature (MAAT) with a high degree of accuracy. However, the existing global MBT/CBT calibration for MAAT based on soils predicts inaccurate temperatures when applied to our African lake dataset. This observation, together with the fact that surface water pH, and to lesser extent, lake depth appear to influence the distribution of branched GDGTs among sites, leads us to conclude that in situ production of branched GDGTs in lakes is likely. The robust relationship between branched GDGT distribution and the temperature and pH of African freshwater lakes makes these compounds suitable for paleoenvironmental reconstruction, however we urge caution in using branched GDGTs in lake sediments to infer past temperatures, unless their exact origin can be determined.

Tierney, J. E.; Russell, J. M.; Eggermont, H.; Hopmans, E. C.; Verschuren, D.; Sinninghe Damsté, J. S.

2010-09-01

88

Climate driven changes in salinity of East African Rift Valley lakes through 2050  

NASA Astrophysics Data System (ADS)

Lakes in endorheic basins are useful sentinels of climate change. Increases in net evaporation due to higher temperature and lower precipitation can lead to lower lake level and higher salinity with concurrent decreases in biodiversity and potentially an increase in dust emissions from more-frequently dry lake beds. We use downscaled output from three different coupled atmosphere-ocean general circulation models as input to a hydrologic model in a GIS-framework to estimate changes in lake level and salinity of the endorheic lakes in the East African Rift Valley. Overall, there is a drying trend through 2050 with salinity increasing to various degrees in the target lakes; however, some emission scenarios under certain model runs predict a large enough precipitation increase to affect a decrease in annual net evaporation and hence an increase in water level and decrease in salinity. We explore the fundamental uncertainties in the GCM predictions and attempt to provide robust bounds on the estimates to make policy-relevant predictions.

Ballatore, T. J.; Muhandiki, V. S.; Sato, K.

2008-12-01

89

Airborne gravity over Lake Vostok and adjacent highlands of East Antarctica  

Microsoft Academic Search

Lake Vostok and a 1200 km transect were the targets of aerogeophysical surveys in East Antarctica during the austral summer of 2000\\/2001. The measurement of gravity anomalies for geologic studies was the primary goal. A total of 24,459 line-km of data were acquired. Favorable weather, aircraft navigation, and instrument performance contributed to excellent data quality. Multiple carrier-phase GPS solutions to

John W. Holt; Thomas G. Richter; Scott D. Kempf; David L. Morse; Donald D. Blankenship

2006-01-01

90

Holocene Sites North-East of Lake Turkana: A Preliminary Report  

Microsoft Academic Search

Mr Barthelme is engaged in research for a Ph.D. degree for the University of California at Berkeley. His work, of which this is a preliminary report, has been undertaken under the auspices of the Koobi Fora Research Project of the National Museums of Kenya.SummaryThe area to the north-east of Lake Turkana has proved to be extremely rich in archaeological material.

John Barthelme

1977-01-01

91

Egg banks in hypersaline lakes of the South-East Europe.  

PubMed

The cyst banks of 6 coastal hypersaline lakes of South-East Europe have been investigated. The study concerned the bottom sediments of Khersonesskoe and Koyashskoe lakes in the Crimea (Ukraine), Nartë saltworks (Albania), Vecchia Salina at Torre Colimena (Apulia, Italy), Pantano Grande and Pantano Roveto at Vendicari (Sicily, Italy). A total of 19 cyst types were recognised. The cyst banks of lakes were found to be well separated in the representation derived from a statistical multivariate data analysis. For all the lakes examined a comparison was possible between the resting community in sediments (cyst bank) and the active one in the water. The cyst banks contained more species than those recorded over a multi-year sampling effort in the water column. The study of cyst hatching, performed on 5 cyst types under lab conditions, demonstrated that cysts do not hatch under the same conditions. Furthermore, each cyst type shows a wide range of preferential hatching conditions, which allow us to confirm the ecological generalism of salt lake species. PMID:19292906

Moscatello, Salvatore; Belmonte, Genuario

2009-03-17

92

Egg banks in hypersaline lakes of the South-East Europe  

PubMed Central

The cyst banks of 6 coastal hypersaline lakes of South-East Europe have been investigated. The study concerned the bottom sediments of Khersonesskoe and Koyashskoe lakes in the Crimea (Ukraine), Nartë saltworks (Albania), Vecchia Salina at Torre Colimena (Apulia, Italy), Pantano Grande and Pantano Roveto at Vendicari (Sicily, Italy). A total of 19 cyst types were recognised. The cyst banks of lakes were found to be well separated in the representation derived from a statistical multivariate data analysis. For all the lakes examined a comparison was possible between the resting community in sediments (cyst bank) and the active one in the water. The cyst banks contained more species than those recorded over a multi-year sampling effort in the water column. The study of cyst hatching, performed on 5 cyst types under lab conditions, demonstrated that cysts do not hatch under the same conditions. Furthermore, each cyst type shows a wide range of preferential hatching conditions, which allow us to confirm the ecological generalism of salt lake species.

Moscatello, Salvatore; Belmonte, Genuario

2009-01-01

93

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

94

Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica.  

PubMed

A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years. PMID:11543521

Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T

2000-01-01

95

Limnological changes in Dom Helvécio Lake (South-East Brazil): natural and anthropogenic causes.  

PubMed

In order to verify changes in physical, chemical and biological features of Dom Helvécio Lake (South-East Brazil), this study compares previous and recent data obtained from limnological investigations over three decades. Plankton species composition and density together with environmental data from 1978, 1983, and during 1999 to 2006 showed changes driven by seasonal climatic forces or by anthropogenic causes. Changes in diversity are shown as a consequence of alternation of rainy and dry periods and introduction of exotic fish species. Finally, suggestions are made for improving conservation efforts in the area, through planned actions and monitoring programmes. PMID:21085784

Maia-Barbosa, P M; Barbosa, L G; Brito, S L; Garcia, F; Barros, C F A; Souza, M B G; Mello, N; Guimarães, A S; Barbosa, F A R

2010-10-01

96

Recent hydrological behavior of the East African great lakes region inferred from GRACE, satellite altimetry and rainfall observations  

NASA Astrophysics Data System (ADS)

We have jointly analysed space gravimetry data from the GRACE space mission, satellite altimetry data and precipitation over the East African Great Lakes region, in order to study the spatiotemporal variability of hydrological parameters (total water storage, lake water volume and rainfall). We find that terrestrial water storage (TWS) from GRACE and precipitation display a common mode of variability at interannual time scale, with a minimum in late 2005, followed by a rise in 2006-2007. We argue that this event is due to forcing by the strong 2006 Indian Ocean Dipole (IOD) on East African rainfall. We also show that GRACE TWS is linked to the El Niño-Southern Oscillation cycle. Combination of the altimetry-based lake water volume with TWS from GRACE over the lakes drainage basins allows estimating soil moisture and groundwater volume variations. Comparison with the WGHM hydrological model outputs is performed and discussed.

Becker, Mélanie; LLovel, William; Cazenave, Anny; Güntner, Andreas; Crétaux, Jean-François

2010-03-01

97

Exploring Subglacial Lake Connectivity via Groundwater Aquifers in the Dome C Region, East Antarctica  

NASA Astrophysics Data System (ADS)

Subglacial lakes lying under the Antarctic Ice Sheet form part of a dynamic, interconnected hydraulic system. Most research exploring the nature of this system has focused on flow along the ice-bed interface, neglecting the effects of groundwater transport, as such systems are thought to lack the transmissivity necessary to accommodate the inferred meltwater volume. In the Dome C region of East Antarctica, however, inferred melt water volumes are relatively low due to proximity to the ice divide and hydraulic gradients are relatively high due to steep subglacial bedrock topography, such that groundwater flow might be viable as a dominant means of water transport. This region contains many small subglacial lakes residing in bedrock depressions of steep basal topography. Preliminary analysis of radar sounding data does not always reveal an obvious hydraulic connection between these lakes despite readily apparent sources of melt feeding these bodies. Here we test several simple models for groundwater flow, including both fractured rock and porous media systems using ice-surface and bedrock geometry inferred from radio-echo sounding data and a published map of melt rates, with the purpose of defining a region in which a groundwater system can account for the majority of the water budget. We then compare these results against maps of basal reflectivity and subglacial lake distribution, as determined from radar sounding data. Areas in which groundwater flow is the dominant process will lack basal lubrication and demonstrate low basal reflectivities, but could still contain small subglacial lakes. While not spatially extensive with respect to the ice sheet, these groundwater-dominated areas could occupy the headwaters of most glacial catchments representing a unique and relatively stable subglacial environment.

Gooch, B. T.; Carter, S. P.; Blankenship, D. D.

2011-12-01

98

Composition and sources of extractable organic matter from a sediment core in Lake Kivu, East African rift valley  

Microsoft Academic Search

Lake Kivu is a gas-charged East African rift lake with currently anoxic bottom water. The extractable compounds and residual organic matter of a short sediment core have ?13C values typical of lacustrine microbial detritus. The total extracts consist primarily of polar compounds such as n-alkanoic acids, hydroxyalkanoic acids, triterpenoids, steroids and monosaccharides, with minor amounts of n-alkanes and n-alkanols. These

Khalid F. Al-Mutlaq; Laurel J. Standley; Bernd R. T. Simoneit

2008-01-01

99

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

100

Deltas of the Lake Malawi rift, east Africa: Seismic expression and exploration implications  

SciTech Connect

High-resolution, air-gun-sourced seismic reflection surveys over the offshore regions of five river deltas in Lake Malawi in the East African rift system reveal considerable variability in acoustic facies and stratigraphic architecture. This variability can largely be attributed to the influences of different structural settings, and to a lesser degree to high-amplitude (100-400 m) and high-frequency (1000 to 100,000 yr) fluctuations in lake level. Deltas on flexural and axial margins in the rift lake show well-developed progradational geometries. In contrast, a delta on a steep, accommodation zone margin distributes coarse sediments over a broad depositional apron, rather than concentrating sediment in discrete progradational lobes as on the other deltas. A large border fault margin river delta displays the most complex tectonic and stratigraphic architecture of all the deltas studied. It contains several delta-associated facies, including prograding clinoform packages, fan deltas stacked against a boundary fault, and extensive subaqueous fans. Flexural margin lowstand deltas may be the most prospective for hydrocarbon exploration due to their large, internally well-organized, progradational lobes and their close proximity to deep-water, high total organic carbon lacustrine source facies.

Scholz, C.A. [Univ. of Miami, FL (United States)

1995-11-01

101

Inversion of Airborne Gravity Data over Subglacial Lakes in East Antarctica  

NASA Astrophysics Data System (ADS)

The team of the University of Texas Institute for Geophysics (UTIG) has been performing airborne geophysical surveys in Antarctica since 1991. Over 260,000 line-km have been surveyed during nine field seasons. The UTIG airborne platform is a contracted DeHavilland Twin Otter instrumented with ice-penetrating radar, laser altimeter, magnetometer, and a gravimeter. The gravimeter utilized is a Bell Aerospace BGM-3 marine system, modified for airborne use, which provides measurements of vertical accelerations at 1 Hz, with verticality of the sensor maintained by a gyro-stabilized platform. The aerogeophysical surveys over subglacial Lake Concordia and Lake Vostok in East Antarctica were conducted by a team from UTIG over the course of the Antarctic field seasons. The region surrounding Lake Concordia was sampled by 6 profiles with a 10 km separation whereas the Lake Vostok survey block was 165 x 330 km with a line spacing of 7.5 km with 11.25 km and 22.5 km ties. 2D gravity inversion was performed for both lakes. The forward problem was solved using Talwani's algorithm for a 2D body of irregular shape. It is described by a non-linear equation between the body's shape and it's density contrast with surrounding rocks. The assumption was that the density contrast between ice/water and rock along the profile is constant. The densities of ice and water are close enough, so the ice and water of the lake can be considered as one body. For Lake Vostok the gravity data were inverted for 2-layered model, consisting of ice/water and sediment lying over dense bedrock. Inversion was performed by a conjugate gradient algorithm for several fixed values of density contrasts. The coordinates of layers' corners were chosen as model parameters. The model was constrained by the lake's boundaries and sub-ice topography, determined from radar sounding. Also, several pre-existing seismic soundings were used as `a priori' information incorporated into the model. The best agreement with seismic data was obtained for density contrast -1.6 g/cc between water and host rock and -0.6 g/cc between sediment and host rock. The differences in thickness of both water and sediment layers at the cross-points of the inverted profiles are within 50 m. The results of 2D inversion for several profiles over Lake Vostok are also used as constraints for 3D inversion. Lake Concordia is located at the very edge of a geophysical survey block. This creates uncertainty in obtaining a regional trend due to lack of data over one side of the lake. Also, there is no additional `a priori' seismic information. Inversion was performed for several values of density contrast between ice/water and surrounding rock. The obtained water thickness for all of density contrasts is not more than 200 m and a sediment layer can not be resolved.

Blankenship, D.

2003-12-01

102

Deliberations on Microbial Life in the Subglacial Lake Vostok, East Antarctica  

NASA Astrophysics Data System (ADS)

The objective was to estimate microbial contents of accretion (lake originating) ice from the Lake Vostok buried beneath 4-km thick East Antarctic ice sheet with the ultimate goal to discover microbial life in this extreme icy environment featured by no light, close to freezing point temperature, ultra-low DOC contents, and an excess of oxygen. The PCR based bacterial and archaeal 16S ribosomal RNA gene sequencing constrained by Forensic Biology and Ancient DNA research criteria was used as a main approach. Epifluorescent and confocal microscopies as well as flow cytometry were implemented. DNA study showed that the accretion ice is essentially bacteria- and archaea-free. Up to now, the only accretion ice type 1 featured by mica-clay sediments presence and namely one horizon of four studied (3607m) allowed the recovery a few bacterial phylotypes. This unexpectedly included the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus and two more unclassified phylotypes all passing numerous contaminant controls. In contrast, the deeper and cleaner accretion ice 2 (three cores) with no sediments presence and near detection limit gas contents gave no reliable signals. The microbes detected in accretion ice 1 are unbelievable to resist an excess of oxygen in the lake water body (700 - 1300 mg O2/l). They are supposed to be thriving in rather warm anoxic sediments in deep faults at the lake bottom and sporadically flushing out along with sediments to the lake veins in a shallow depth bay due to a seismotectonic activity likely operating in the lake environment. A few geophysical and geological evidences support this scenario. In the bay the presence of mica-clay sediments, higher accretion rate due to relief rise and likely oxygen-depleted upper layer of water can provide microbes with a chance to escape the high oxygen tension by the rapid entrapment into accretion ice 1. Sediment-free accretion ice 2, which forms above a deeper part of the lake, shows no evidence for reasonable source for microbe contribution given highly oxygenated lake water environment. Microscopy and flow cytometry trials on strictly decontaminated ice samples gave supporting results. While microscopy failed to reveal cells because the local concentrations were below the detection limit, the flow cytometry succeeded in a preliminary estimate of 9 and 24 cells/ml for accretion 1 (3561m) and control glacial (2054m) ice samples, respectively. However, given the ratio contaminants to indigenous cells is about 10:1 (from PCR results), the genuine microbial contents for both accretion and glacial ice samples is expected to be as low as 1 cell/ml what practically means "sterile" conditions. Thus, the accretion ice from Lake Vostok contains the very low unevenly distributed biomass indicating that the water body (at least upper layer) should also be hosting a highly sparse life, if any. By this, the Lake Vostok for the first time could present the big natural "sterile" water body on Earth providing a unique test area for searching for life on icy moons and planets. The search for life in Lake Vostok is constrained by a high chance of forward-contamination which can be minimized by using of stringent decontamination procedures and comprehensive biological controls.

Bulat, S.; Alekhina, I.; Lipenkov, V.; Lukin, V.; Marie, D.; Petit, J.

2004-12-01

103

Post-Depositional Behavior of Cu in a Metal-Mining Polishing Pond (East Lake, Canada)  

USGS Publications Warehouse

The post-depositional behavior of Cu in a gold-mining polishing pond (East Lake, Canada) was assessed after mine closure by examination of porewater chemistry and mineralogy. The near-surface (upper 1.5 cm) sediments are enriched in Cu, with values ranging from 0.4 to 2 wt %. Mineralogical examination revealed that the bulk of the Cu inventory is present as authigenic copper sulfides. Optical microscopy, energy-dispersion spectra, and X-ray data indicate that the main Cu sulfide is covellite (CuS). The formation of authigenic Cu-S phases is supported by the porewater data, which demonstrate that the sediments are serving as a sink for dissolved Cu below sub-bottom depths of 1-2 cm. The zone of Cu removal is consistent with the occurrence of detectable sulfide and the consumption of sulfate. The sediments can be viewed as a passive bioreactor that permanently removes Cu as insoluble copper sulfides. This process is not unlike that which occurs in other forms of bioremediation, such as wetlands and permeable reactive barriers. Above the zone of Cu removal, dissolved Cu maxima in the interfacial porewaters range from 150 to 450 ??g L-1 and reflect the dissolution of a Cu-bearing phase in the surface sediments. The reactive phase is thought to be a component of treatment sludges delivered to the lake as part of cyanide treatment. Flux calculations indicate that the efflux of dissolved Cu from the sediments to the water column (14-51 ??g cm-2 yr-1) can account for the elevated levels of dissolved Cu in lake waters (???50 ??g L-1). Implications for lake recovery are discussed.

Martin, A. J.; Jambor, J. L.; Pedersen, T. F.; Crusius, J.

2003-01-01

104

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

105

Searching for life in extreme environments relevant to Jovian's Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica)  

Microsoft Academic Search

The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice) from the subglacial Lake Vostok (Antarctica) buried beneath the 4-km thick East Antarctic ice sheet. The samples were extracted by heavy deep ice drilling from 3659 m below the surface. High pressure, a low carbon and chemical content, isolation, complete darkness and the

Sergey A. Bulat; Irina A. Alekhina; Dominique Marie; Jean Martins; Jean Robert Petit

2011-01-01

106

Impact of Invasive Water Hyacinth ( Eichhornia crassipes ) on Snail Hosts of Schistosomiasis in Lake Victoria, East Africa  

Microsoft Academic Search

Invasive plants may change ecologic conditions to contribute to transmission of human diseases. This study examined whether water hyacinth (Eichhornia crassipes) had an effect on the snails Biomphalaria sudanica and B. choanomphala, hosts of the disease organism Schistosoma mansoni in Lake Victoria, East Africa. Eight 16-m2 enclosures were established in shallow shoreline areas and were paired for water depth, substrate,

Mary L. Plummer

2005-01-01

107

Protecting The Mahakam Lakes In East Kalimantan Through An Eco-Regional Development Program For Sustainable Livelihoods  

Microsoft Academic Search

The Middle Mahakam Lakes area is an area of high socio-economic value for the fishing industry and a water-catch and river regulatory system. Moreover, this area has a high biodiversity potential and also hosts the symbol species of East Kalimantan, the Critically Endangered Irrawaddy dolphin. Major identified threats involve sedimentation and species habitat loss through logging and forest fires, pollution

Indah Blok

108

Sedimentary record of hydrophobic organic compounds in relation to regional economic development: A study of Taihu Lake, East China  

Microsoft Academic Search

Sediment cores taken from Taihu Lake, East China were analyzed for polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polybrominated biphenyl ethers (PBDEs). The results showed a general sharp increase of HCH, DDT, PAH and PBDE concentrations in the surface layers, corresponding to a sedimentation time of 1980 and 1990 onward in the Meiliang Bay and Xukou Bay, respectively. The

Guoqing Liu; Gan Zhang; Zhangdong Jin; Jun Li

2009-01-01

109

75 FR 38723 - Safety Zone; St. Ignace 4th of July Fireworks, East Moran Bay, Lake Huron, St. Ignace, MI  

Federal Register 2010, 2011, 2012, 2013

...Safety Zone; St. Ignace 4th of July Fireworks, East Moran Bay, Lake Huron, St...Bay during the St. Ignace 4th of July Fireworks display, July 4, 2010. This temporary...vessels from the hazards associated with a fireworks display. DATES: This rule is...

2010-07-06

110

Recent hydrological behaviour of the East African Great Lakes region from GRACE, satellite altimetry and rainfall observations  

NASA Astrophysics Data System (ADS)

We have jointly analysed space gravimetry data from the GRACE space mission, precipitation and satellite altimetry data over the East African Great Lakes region, in order to study the spatio-temporal variability of hydrological changes. We find that precipitation and terrestrial water storage (TWS) from GRACE show a common mode of variability at interannual time scale, with a minimum in late 2005, followed by rise in 2006-2007. We argue that the 2006-2007 TWS rise is due to forcing by the strong 2006 Indian Ocean Dipole on East African rainfall. We also show that GRACE TWS is related to the El Niño-Southern Oscillation cycle. Combination of the altimetry-based lake volume with TWS from GRACE over the lakes drainage basins allows estimating soil and underground water volume variations, with results in good agreement with the WGHM hydrological model outputs.

Becker, M.; Llovel, W.; Cazenave, A. A.; Güntner, A.; Cretaux, J.

2009-12-01

111

New Australopithecus boisei specimens from east and west Lake Turkana, Kenya.  

PubMed

New specimens of Plio-Pleistocene Australopithecus boisei are described from east and west Lake Turkana in Northern Kenya. These include a cranium and partial mandible from deposits close to 2.5 Myr and two partial crania and two mandibles from later horizons. The earlier fossils enable us to decipher, for the first time, some of the in situ evolution of this species within the Turkana Basin. The following are among the important changes in the cranium through time: 1) increase in size and change in shape of the braincase, 2) changes in the meningeal vessel pattern and possibly in the venous drainage pattern, 3) increased flexion of the cranial base and decreased prognathism, and 4) changes in the temporal bone to bring about a more vertical posterior face of the petrous pyramid and the development of a strong articular eminence. PMID:3136654

Leakey, R E; Walker, A

1988-05-01

112

Bacterial diversity of the rock-water interface in an East Antarctic freshwater ecosystem, Lake Tawani(P)†.  

PubMed

Schirmacher Oasis is one of the few ice-free plateaus in East Antarctica that maintains a unique distribution of over 120 microbial-rich, dynamic freshwater lakes, most of which are unexplored. In this study, we describe the bacterial diversity of the rock-water interface in Lake Tawani(P) using culture-independent Bacterial Tag Encoded FLX Amplicon Pyrosequencing (bTEFAP), clone library construction, and culture-based analysis targeting the eubacterial 16S rRNA gene. Lake Tawani(P)was formed in a fossil valley by the accumulation of snow and glacial melt through surface channels into a low-catchment depression. Overall this lake exhibited thirteen bacterial phyla and one-hundred and twelve genera. The Qiime bioinformatics analysis on the bTEFAP alone exhibited higher coverage of the bacterial composition in Lake Tawani(P) than the clone library construction or culture-based methodology. Particularly due to the higher sensitivity of the bTEFAP approach, we detected and differentiated members of the phyla: Chloroflexi, Gemmatimonadetes, Planctomycetes, Nitrospira, and Candidate Division TM7 that other methods were unable to reveal. Nevertheless we found that the use of multiple approaches identified a more complete bacterial community than by using any single approach. Investigating the bacterial diversity of the Schirmacher Oasis lakes, especially those connected through surface channels and encompassed by valleys, will help unravel the dynamic nature of these unique seasonal, freshwater lakes, which potentially harbors highly adapted bacterial taxa with defined ecological functions. PMID:23369372

Huang, Jonathan P; Swain, Ashit K; Thacker, Robert W; Ravindra, Rasik; Andersen, Dale T; Bej, Asim K

2013-02-01

113

East African mid-Holocene wet-dry transition recorded in palaeo-shorelines of Lake Turkana, northern Kenya Rift  

NASA Astrophysics Data System (ADS)

The 'wet' early to mid-Holocene of tropical Africa, with its enhanced monsoon, ended with an abrupt shift toward drier conditions and was ultimately replaced by a drier climate that has persisted until the present day. The forcing mechanisms, the timing, and the spatial extent of this major climatic transition are not well understood and remain the subject of ongoing research. We have used a detailed palaeo-shoreline record from Lake Turkana (Kenya) to decipher and characterise this marked climatic transition in East Africa. We present a high-precision survey of well-preserved palaeo-shorelines, new radiocarbon ages from shoreline deposits, and oxygen-isotope measurements on freshwater mollusk shells to elucidate the Holocene moisture history from former lake water-levels in this climatically sensitive region. In combination with previously published data our study shows that during the early Holocene the water-level in Lake Turkana was high and the lake overflowed temporarily into the White Nile drainage system. During the mid-Holocene (~ 5270 ± 300 cal. yr BP), however, the lake water-level fell by ~ 50 m, coeval with major episodes of aridity on the African continent. A comparison between palaeo-hydrological and archaeological data from the Turkana Basin suggests that the mid-Holocene climatic transition was associated with fundamental changes in prehistoric cultures, highlighting the significance of natural climate variability and associated periods of protracted drought as major environmental stress factors affecting human occupation in the East African Rift System.

Garcin, Yannick; Melnick, Daniel; Strecker, Manfred R.; Olago, Daniel; Tiercelin, Jean-Jacques

2012-05-01

114

Reconstructing Late Holocene Climate Variability in North East China From Varved Maar Lake Sediments  

NASA Astrophysics Data System (ADS)

Reconstructing climatic variability over the past c. 2 ka years is recognised as a key PAGES timeframe (focus 2). However few high-resolution records exist from the climate sensitive region of N) China which receives the majority of its precipitation from the east Asian summer monsoon (EASM). Interactions between the EASM and the global climate system have great resonance. Such examples include how the EASM responded to changes in climate over the documented e.g. "Medieval Warm Period" (c. AD 900 - 1300), "Little Ice Age" (c. AD 1350-1850) and recent warming. At present, literature remains contradictory to such environmental changes in NE China over this time-frame due to poor chronological control, low resolution of existing studies and even due to the inexact terminology of these climatic periods. Xiaolongwan Lake (XLW) is a small, closed, maar lake located in the Long Gang Volcanic Field, NE China (42°18'N; 126°19'E). It is at an elevation of 655 m a.s.l. with a maximum depth of 15 m. A varve chronology has been created for a 143 cm composite core (2 cores collected in 2006), and here we present diatoms and organic geochemistry (?13C, TOC, C/N) evidence for environmental change over the past c. 2 ka years. Results show a gradual change in diatom species, moving from a composition where opportunistic species (e.g. Achnanthidium minutissimum) dominate (between c. 100 BC to 500 years AD) at the beginning of the record to one comprised of benthic/epiphytic species (e.g. Staurosira construens var venter, Punctastriata discoidea, Gomphonema parvulum). The introduction after c. 1850 years AD of the planktonic diatom species, Discotella woltereckii, not previously seen in the record, coincides with recent warming. This may be a response to changing limnological conditions, such as decreasing duration of lake ice-cover. Bulk organic ?13C results conducted on a short core collected from XLW in summer 2007, show that over the past c. 350 years there is a distinct decreasing trend in lake macrophytes. At the same time, trends in decreasing mean annual precipitation and an increasing trend in mean annual temperatures for the region are documented from meteorological records. It is possible that reduced EASM intensity may be affecting the limnology and therefore biology of XLW as seen in more recent years. Quantitative techniques (siZer) will later provide a method of assessing periodicities of EASM from this high-resolution record in order to compare with other independent palaeorecords.

Panizzo, V. N.; Mackay, A. W.; Rioual, P.; Chu, G.; Leng, M. J.

2008-12-01

115

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

116

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

117

Precise analysis of ICESat altimetry data and assessment of the hydrostatic equilibrium for subglacial Lake Vostok, East Antarctica  

NASA Astrophysics Data System (ADS)

Based on the Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, the hydrostatic equilibrium (HE) condition for the subglacial Lake Vostok, East Antarctica, is evaluated. A digital elevation model (DEM) of the ice surface is derived by a regional crossover adjustment. The analysis of the DEM and its comparison with GPS derived ice-surface elevations and an ice-surface DEM based on radar altimetry data reveal an overall accuracy of better than ± 0.7 m for the lake area. The DEM is combined with an ice-thickness model and a regional geoid model to determine the deviation of the local ice-surface height from HE. For large parts of the lake, the ice sheet fulfils the HE. Our results reveal a strong positive deviation of about 10 m along the lake shoreline. In addition, positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio-echo sounding. In the southern part of the lake, we find a linear negative deviation (-4.0 m) which coincides with the convoy route from Vostok station to Mirny base. In addition to the DEM, relative biases for the ICESat laser operational periods are determined in the regional crossover adjustment.

Ewert, H.; Popov, S. V.; Richter, A.; Schwabe, J.; Scheinert, M.; Dietrich, R.

2012-09-01

118

Saccharospirillum impatiens gen. nov., sp. nov., a novel c-Proteobacterium isolated from hypersaline Ekho Lake (East Antarctica)  

Microsoft Academic Search

Five Gram-negative, motile, aerobic to microaerophilic spirilla were isolated from various depths of the hypersaline, heliothermal and meromictic Ekho Lake (East Antarctica). The strains are oxidase- and catalase-positive, metabolize a variety of sugars and carboxylic acids and have an absolute requirement for sodium ions. The predominant fatty acids of the organisms are C16 : 1v7c ,C 16 : 0 and

Matthias Labrenz; Paul A. Lawson; Brian J. Tindall; Matthew D. Collins; Peter Hirsch

119

Magnetic signature of heavy metals pollution of sediments: case study from the East Lake in Wuhan, China  

Microsoft Academic Search

Detailed magnetic measurements and geochemical analyses were performed on 114 sediment samples collected from the East Lake,\\u000a Wuhan city, China, to establish a possible link between the enhanced concentration of anthropogenic magnetic particles and\\u000a heavy metals with known sources. Relatively higher magnetic susceptibility values (mass-specific, ?, >150 × 10?8 m3 kg?1) were observed for samples near the pollution sources: e.g. the Wuhan Iron and

Tao Yang; Qingsheng Liu; Lungsang Chan; Zhendong Liu

2007-01-01

120

Coastal wetlands: Proceedings of First Great Lakes Wetlands Colloquium, November 1984, East Lansing, Michigan  

Microsoft Academic Search

This book explores the wetlands of the Great Lakes. Topics considered include the effects of water level fluctuations on Great Lakes coastal marshes; environmental influences on the distribution and composition of wetlands in the Great Lakes Basin; vegetation dynamics, buried seeds, and water level fluctuations on the shoreline of the Great Lakes; preliminary observations on the flux of carbon, nitrogen,

H. H. Prince; F. M. DItri

1986-01-01

121

Food web structure and mercury transfer in two contrasting Ugandan highland crater lakes (East Africa)  

Microsoft Academic Search

Volcanic crater lakes scattered throughout western Uganda are important local sources of water and fish. Two representative but contrasting crater lakes near the Kibale National Park were sampled in 2000; the hyper-eutrophic Lake Saka, which is highly affected by agricultural prac- tices, and the mesotrophic Lake Nkuruba that is still sur- rounded by intact forest. The food web structures in

L. Campbell; R. E. Hecky; D. G. Dixon; L. J. Chapman

2006-01-01

122

Temporal trends of pollution Pb and other metals in east-central Baffin Island inferred from lake sediment geochemistry.  

PubMed

Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20 degrees latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the (206)Pb/(207)Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17-26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb-Pb co-isotopic plot ((206)Pb/(207)Pb vs.(208)Pb/(206)Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere. PMID:19665172

Michelutti, Neal; Simonetti, Antonio; Briner, Jason P; Funder, Svend; Creaser, Robert A; Wolfe, Alexander P

2009-08-07

123

Water Balance Modelling in a Semi-Arid Environment Using Remote Sensing, Lake Manyara, East African Rift, Tanzania  

NASA Astrophysics Data System (ADS)

We estimate the water balance in a semi-arid environment with limited in situ data by using a remote sensing approach. We use a semi-distributed hydrological model fed with remote sensing data to study the spatial and temporal variability of water balance parameters within the catchment. Satellite gravimetry GRACE data is used to verify the trends of the inferred lake level changes. The results show that the lake undergoes high spatial and temporal variations, characteristic of a semi-arid climate with high evaporation and low rainfall. We observe that the Lake Manyara water balance and GRACE equivalent water depth show comparable trends; a decrease after 2002 followed by a sharp increase in 2006-2007. Our modelling confirms the importance of the 2006-2007 Indian Ocean Dipole fluctuation in replenishing the groundwater reservoirs of East Africa. We therefore demonstrate that water balance modelling can be performed accurately using remote sensing data even in complex climatic settings. Despite the small size of Lake Manyara, GRACE data are useful and thus show great potential for hydrological research on smaller un-gauged lakes and catchments in semi-arid environments.

Deus, Dorothea; Gloaguen, Richard; Krause, Peter

2013-04-01

124

Mid to Late Holocene hydroclimatic and geochemical records from the varved sediments of East Lake, Cape Bounty, Canadian High Arctic  

NASA Astrophysics Data System (ADS)

A long sedimentary sequence from East Lake, Cape Bounty, Melville Island (74°55?N; 109°30?W) contains a 4200 year-long clastic varved record of paleohydrologic variations at high resolution. Sedimentary elemental geochemistry from micro X-ray fluorescence (?-XRF) and sediment fabric variability reflect changes in sediment sources and lacustrine conditions through time. The sedimentary environment progressed from marine in the mid-Holocene, to estuarian from 2195 BC to 243 AD, to fully lacustrine source after 244 AD. Correlation with local meteorological data indicates that varve thickness (VT) is positively correlated with snow depth on May 1st and negatively correlated with mean Sept-May temperatures. Our paleoclimatic reconstruction from VT series revealed high snow accumulation and warm Sept-May months before 1350 BC, and a period of low snow accumulation and cold Sept-May between 1600-1900 AD that may correspond to the Little Ice Age. The general trends of VT series from Cape Bounty are in phase with the ? 18 O series in Agassiz Ice Cap, and in anti-phase with the VT series from Lower Murray Lake in the northeastern of Queen’s Elizabeth Islands (QEI). Low mean Arctic temperatures coincide with clusters of high sediment yield events at East, Nicolay and South Sawtooth Lakes, especially during 1600-1750 AD and 1810-1910 AD. The East Lake record also exhibits the signature of the Atlantic Multidecadal Oscillation (AMO) for periods: 600-850 AD, 1400-1550 AD and 1750-1850 AD.

Cuven, Stéphanie; Francus, Pierre; Lamoureux, Scott

2011-09-01

125

Ground-Water Resources of the Mille Lacs Lake Area, East-Central Minnesota.  

National Technical Information Service (NTIS)

The purposes of this report are: (1) describe groundwater occurrence and quality in the surficial and uppermost buried aquifers of the Mille Lacs Lake area, (2) define the interaction between ground water and Lake Onamia, and (3) describe susceptibility t...

L. C. Trotta T. K. Cowdery

1998-01-01

126

The geochemistry, age, and origin of groundwater in a mafic pluton, East Bull Lake, Ontario, Canada  

NASA Astrophysics Data System (ADS)

The geochemistry of groundwater in the East Bull Lake gabbro-anorthosite pluton near Elliot Lake, Ontario, Canada, has been investigated. Three chemical types of groundwater are present to depths of about 650 m, and are controlled by the nature of the groundwater flow systems and the water/rock interactions in the fractures. Ca/HCO 3 water is present in the recharge area of the local flow system and evolves rapidly along the direction of groundwater flow to a high-pH, Na/HCO 3 water primarily by cation exchange reactions. Saline Na/Cl water is present below a depth of about 350 m. On the basis of its chemistry and hydraulic head measurements, the Na/Cl water is believed to be part of a deep regional groundwater flow system. Carbon-14 measurements of the Na/HCO 3 water suggest that this water was recharged shortly after the last Pleistocene deglaciation. This is supported by ? 18O values that are as much as 6%. lighter than shallow modern groundwater. Despite the high Mg content of the enclosing rocks, Mg 2+ concentrations in the groundwater of this unit are <1.0 mg L -1, and may be controlled by present-day serpentinization or formation of talc. Laumontite is thermodynamically stable in the Na/HCO 3 and Na/Cl waters and hence could still be forming under the present low-temperature conditions (<25°C). The stable isotope composition of the Na/Cl water suggests that this water type is not a geochemically evolved product of the overlying waters, although present-day albitization of the anorthosite could be responsible for the increased Ca/Na ratio in the Na/Cl water compared to the other water types. The salinity of this water appears to have been derived outside the pluton, possibly as an ancient infiltration into crystalline basement rocks of saline formation waters present in Paleozoic sedimentary rocks, which formerly overlay the pluton, or from nearby Proterozoic formations. This hypothesis is supported by Br/Cl ratios that are similar to sea water and many present-day formation waters, and the isotopic composition of the dissolved sulphate. The He "age" of the saline water is of the order of 10 8 years. Therefore both the saline water and many of its solutes appear to have ancient origins.

Bottomley, D. J.; Gascoyne, M.; Kamineni, D. C.

1990-04-01

127

Climate driven changes in salinity of East African Rift Valley lakes through 2050  

Microsoft Academic Search

Lakes in endorheic basins are useful sentinels of climate change. Increases in net evaporation due to higher temperature and lower precipitation can lead to lower lake level and higher salinity with concurrent decreases in biodiversity and potentially an increase in dust emissions from more-frequently dry lake beds. We use downscaled output from three different coupled atmosphere-ocean general circulation models as

T. J. Ballatore; V. S. Muhandiki; K. Sato

2008-01-01

128

Coastal wetlands: Proceedings of First Great Lakes Wetlands Colloquium, November 1984, East Lansing, Michigan  

SciTech Connect

This book explores the wetlands of the Great Lakes. Topics considered include the effects of water level fluctuations on Great Lakes coastal marshes; environmental influences on the distribution and composition of wetlands in the Great Lakes Basin; vegetation dynamics, buried seeds, and water level fluctuations on the shoreline of the Great Lakes; preliminary observations on the flux of carbon, nitrogen, and phosphorous in a Great Lakes coastal marsh; nutrient cycling by wetlands and possible effects of water levels; and avian wetland habitat functions affected by water level fluctuations.

Prince, H.H.; D'Itri, F.M.

1986-01-01

129

Fluxes and distribution of intact glycerol dialkyl glycerol tetraether membrane lipids in the water column of Lake Challa, East Africa  

NASA Astrophysics Data System (ADS)

Over the last years, glycerol dialkyl glycerol tetraether (GDGT) membrane lipids have become an interesting tool in palaeoclimate research. Both the TEX86 sea surface temperature proxy, based on isoprenoid GDGT membrane lipids derived from pelagic Crenarchaeota, and the MBT/CBT annual mean air temperature proxy, based on the distribution of branched GDGTs derived from soil bacteria, receive increasing interest to be also applied in lake sediments. Despite successful studies utilizing the TEX86 to reconstruct past lake surface temperatures in two large African lakes, other studies indicated that TEX86 values derived from lake surface sediments differed from what would be expected based on the lake surface water temperatures. In addition, in two tropical lake systems, the distribution of branched GDGT lipids in lake surface sediments appeared to differ from that in the surrounding soils. Both situations suggest production of GDGTs by additional sources in some lake systems, hampering application of earlier mentioned temperature proxies. In order to constrain the provenance and flux of GDGT lipids in one of these lakes, Lake Challa, a freshwater crater lake in East Africa, we used a novel separation technique to analyze both intact and core GDGT membrane lipids in monthly samples derived from a sediment trap installed at 35m depth in the lake. Intact GDGT lipids still contain a functional polar head group which is thought to be lost quickly after cell lysis. Therefore, the presence of such intact GDGT lipids is thought indicative for extant life, most likely autochthonous in origin. High fluxes of intact GDGT-0 lipids, maybe derived from methanogenic Archaea residing in anoxic micro niches in descending particles, occur in July and August during a diatom bloom. High fluxes of both the intact and core isoprenoid GDGT lipid crenarchaeol in December and January clearly reflect the bloom of Crenarchaeota. TEX86 values of both the intact and core isoprenoid GDGTs are similar, confirming they share a similar source, i.e. aquatic Crenarchaeota. As this distribution is different from that in the lake surface sediments, a contribution of GDGTs from a deep living community of anaerobic methanogenic Archaea is suggested. Branched GDGTs were expected to be present mainly in the form of core lipids, being fossilized material derived from soils surrounding the lake. This is, indeed, the case for July and August. Strikingly, however, high proportions of intact branched GDGTs are observed in December-February, coinciding with the crenarchaeotal bloom. Partly, this flux might reflect soil derived GDGTs that have not yet lost their functional head groups, but a contribution from a branched GDGT synthesizing community living in the water column cannot be fully excluded. Therefore, the MBT/CBT proxy in lakes can only be applied if the provenance of the branched GDGTs is well constrained.

Weijers, J.; Buckles, L.; Verschuren, D.; Sinninghe Damsté, J. S.

2009-12-01

130

Water quality, nutrient budget, and pollutant loads in Chinese mitten crab ( Eriocheir sinensis) farms around East Taihu Lake  

NASA Astrophysics Data System (ADS)

To understand the factors causing frequent outbreaks of harmful algae blooms in the Taihu Lake, China, we studied water quality and nutrient budget in Chinese mitten crab ( Eriocheir sinensis) farm ponds in the eastern part of the lake from November 2007 to December 2009. We estimated the nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) loads. Materials input and output ponds, water exchange, and applied management practices of 838.5-hm2 crab ponds were surveyed using questionnaires. Water quality of 12 ponds, which were located no more than 2 km from East Taihu Lake, were monitored. The results show that water quality in the crab ponds was better than reference data. Feeds, including corn seed, commercial feed, trash fish, and gastropod, were the major sources of N and P input in the crab ponds, contributing 88.7% and 94.9%, respectively. In total, 60.5% of N and 37.3% of P were sequestered by macrophytes, and only 15.7% and 8.5% of them were discharged as effluent. The net loads of N and P in effluent were 16.43 kg/hm2/cycle and 2.16 kg/hm2/cycle, respectively, while the COD load was -17.88 kg/hm2/cycle. This indicated that crab farming caused minor negative impact on the trophic status of the lake area, which was attenuated by macrophytes. However, wastewater purification is still necessary in crab faming.

Cai, Chunfang; Gu, Xiaohong; Huang, Hezhong; Dai, Xiuying; Ye, Yuantu; Shi, Chenjiang

2012-01-01

131

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

132

Selected hydrologic data from wells in the East Shore area of the Great Salt Lake, Utah, 1985  

USGS Publications Warehouse

This report contains hydrologic data for wells collected in the East Shore area of the Great Salt Lake, Utah. It includes water quality data, discharge measurements, water levels, and drillers logs. Most of the data in this report were collected from 1983 to 1985, and provide groundwater data for use by officials managing water resources and the general public and to supplement an interpretive report for the area that will be published later. Determinations can be made for the depth to water bearing units, water levels in wells, well yields, or chemical quality of groundwater at sites illustrated in this report. (Lantz-PTT)

Plantz, G. G.; Appel, C. L.; Clark, D. W.; Lambert, P. M.; Puryear, R. L.

1985-01-01

133

A 75,000-year TEX86-based Temperature Record from Lake Malawi, East Africa  

Microsoft Academic Search

We present a record of tropical paleotemperature from one of the few continental sites available to date, Lake Malawi. Using the TEX86 molecular paleotemperature proxy, we have extended the previous Lake Malawi temperature record from 23,000 to 75,000 years. The record, taken from hole 2a Site MAL05-2A drilled during the Lake Malawi Drilling Project in 2005, ends at around 75

M. L. Woltering; J. P. Werne; T. C. Johnson; S. Schouten; J. S. Sinninghe Damste

2007-01-01

134

Novosphingobium fuchskuhlense sp. nov., isolated from the north-east basin of Lake Grosse Fuchskuhle.  

PubMed

A yellow pigmented, gram-negative, rod-shaped bacterium designated FNE08-7(T) was isolated from subsurface water of the north-east basin of the bog lake Grosse Fuchskuhle (Brandenburg, Germany). A first analysis of the nearly full-length 16S rRNA gene sequence analysis including environmental 16S rRNA gene sequences derived from freshwater ecosystems showed that strain FNE08-7(T) is the first cultured representative, to our knowledge, of the freshwater tribe Novo-A2. Further analysis indicates highest 16S rRNA gene sequence similarities to the type strains of Novosphingobium stygium (98.0?%) and Novosphingobium taihuense (97.4?%) and between 94.0?% and 96.9?% sequence similarity to other members of the genus Novosphingobium. Reconstruction of phylogenetic trees showed that strain FNE08-7(T) formed a distinct cluster with the type strains of N. stygium and N. taihuense supported by high bootstrap values. DNA-DNA hybridization of strain FNE08-7(T) with N. stygium SMCC B0712(T) and N. taihuense DSM 17507(T) revealed low similarity values of 18.4?% (reciprocal: 11.4?%) and 23.1?% (reciprocal: 54.2?%), respectively. The predominant fatty acid of the isolate is C(18?:?1)?7c (56.4?%) and two characteristic 2-hydroxy fatty acids, C(14?:?0) 2-OH (16.5?%) and C(15?:?0) 2-OH (3.3?%) occur. Ubiquinone Q-10 is the major respiratory quinone. The predominant polar lipids are phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylglycerol, sphingoglycolipid, phosphatidylcholine and minor amounts of diphosphatidylglycerol. Spermidine is the predominant polyamine. Characterization by genotypic, chemotaxonomic and phenotypic analysis indicate that strain FNE08-7(T) represents a novel species of the genus Novosphingobium within the Alphaproteobacteria. Therefore, we propose the species Novosphingobium fuchskuhlense sp. nov., with FNE08-7(T) (?=?DSM 25065(T)?=?CCM 7978(T)?=?CCUG 61508(T)) as the type strain. PMID:22544783

Glaeser, Stefanie P; Bolte, Kathrin; Martin, Karin; Busse, Hans-Jürgen; Grossart, Hans-Peter; Kämpfer, Peter; Glaeser, Jens

2012-04-27

135

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

136

Post-glacial paleoenvironments of the Lake Winnebago basin, east central Wisconsin, based on ostracodes  

SciTech Connect

Ostracodes were used to determine post-glacial paleoenvironments of the Lake Winnebago Basin. Following the retreat of the Wisconsinian Green Bay Lobe, Glacial Lake Oshkosh was dammed behind the ice sheet. As the modern Fox River was established, Glacial Lake Oshkosh shrank to form modern Lake Winnebago. Ostracodes were sampled from four vibracores in attempts to correlate sedimentary units and determine paleoenvironments. The oldest unit identified in their vibracores is grayish red clay that is thought to be reworked glacial till that was deposited in a lacustrine setting. This clay is dominated by Candona rawsoni, an ostracod species that prefers cold and deep water. The broken and eroded carapaces of the C. rawsoni in the greyish-red clay suggest reworking and transport, perhaps from the Lake Superior Basin. The contact between the clay and overlying sediments is an erosional unconformity, overlain in some places by gravel. The clay is overlain by coarsening-upward from sandy-silt to medium-grained sand, suggesting a decrease in lake levels and water depths. Raised shorelines 20 and 60 ft above present lake level constitute the geomorphic evidence for higher lake levels. Offshore, at depths of ten to twenty feet, the sediment type above is an olive black organic-rich mud where juveniles of C. rawsoni are the dominant species.

Fielder, R.F.; Smith, G.L.; Fitzgerald, T.M. (Lawrence Univ., Appleton, I (United States). Dept. of Geology)

1994-04-01

137

Alkalimonas amylolytica gen. nov., sp. nov., and Alkalimonas delamerensis gen. nov., sp. nov., novel alkaliphilic bacteria from soda lakes in China and East Africa  

Microsoft Academic Search

Two related novel alkaliphilic and slightly halophilic bacteria are described. They are strain N10 from Lake Chahannor in China and strain 1E1 from Lake Elmenteita in East Africa. Both strains are strictly aerobic, heterotrophic, alkaliphilic, mesophilic, and require NaCl for growth. The optimal conditions for growth were at pH 10–10.5 and 2–3% (w\\/v) NaCl. Cells of both strains were Gram-negative,

Yanhe Ma; Yanfen Xue; William D. Grant; Nadine C. Collins; Andrew W. Duckworth; Robert P. van Steenbergen; Brian E. Jones

2004-01-01

138

Analogy between natural gas found in lakes of rift valley system of east Africa and its allied gas in Japan  

SciTech Connect

The Afar triangle in northeastern Ethiopia is where the Red Sea rift, the Carlsberg Ridge of the Indian Ocean, and the Rift Valley system of east Africa meet. In 1979, J. Welhan and H. Craig reported that hydrothermal vents at 21/sup 0/N, on the East Pacific Rise, are discharging turbid waters. Mixtures of the plumes with ambient seawater contain significant amounts of dissolved H/sub 2/ and CH/sub 4/ as well as mantel-derived /sup 3/He-rich helium. The /sup 3/He//sup 4/He ratios of rock samples obtained earlier by J. Lupton and H. Craig from the Mid-Oceanic Ridge, including the Mid-Atlantic Ridge and the east Pacific Rise, are extremely high at an almost constant value of (1.3 +/- 0.2) x 10/sup -5/, which they defined as the MOR-type helium. However, the deep brines of the Red Sea contain about 1,000 times more methane than normal seawater does, according to Gold and Soter in 1980. Much evidence leads us to believe that large amounts of /sup 3/He-rich helium-bearing natural gas have been gushing out in many places of the Rift Valley of east Africa for a long time. In 1980, Gold and Soter stated that Lake Kivu, which occupies part of the East African rift valley, contains 50 million tons of dissolved methane for which there is no adequate microbial source. The Japanese Islands began to separate from the Asian continent during the early Miocene. The early Miocene was characterized by intensive volcanic activity that produced large amounts of pyroclastics and other volcanic rocks, generally called green tuff in Japan. It has been suggested that oil and gas in green tuff is derived from the upper mantle.

Fukuta, O.

1984-09-01

139

Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka.  

PubMed

The most explosive volcanic event of the Quaternary was the eruption of Mt. Toba, Sumatra, 75,000 y ago, which produced voluminous ash deposits found across much of the Indian Ocean, Indian Peninsula, and South China Sea. A major climatic downturn observed within the Greenland ice cores has been attributed to the cooling effects of the ash and aerosols ejected during the eruption of the Youngest Toba Tuff (YTT). These events coincided roughly with a hypothesized human genetic bottleneck, when the number of our species in Africa may have been reduced to near extinction. Some have speculated that the demise of early modern humans at that time was due in part to a dramatic climate shift triggered by the supereruption. Others have argued that environmental conditions would not have been so severe to have such an impact on our ancestors, and furthermore, that modern humans may have already expanded beyond Africa by this time. We report an observation of the YTT in Africa, recovered as a cryptotephra layer in Lake Malawi sediments, >7,000 km west of the source volcano. The YTT isochron provides an accurate and precise age estimate for the Lake Malawi paleoclimate record, which revises the chronology of past climatic events in East Africa. The YTT in Lake Malawi is not accompanied by a major change in sediment composition or evidence for substantial temperature change, implying that the eruption did not significantly impact the climate of East Africa and was not the cause of a human genetic bottleneck at that time. PMID:23630269

Lane, Christine S; Chorn, Ben T; Johnson, Thomas C

2013-04-29

140

A 250 ka oxygen isotope record from diatoms at Lake El'gygytgyn, far east Russian Arctic  

NASA Astrophysics Data System (ADS)

In 2003 sediment core Lz1024 was drilled at Lake El'gygytgyn, far east Russian Arctic, in an area of the Northern Hemisphere which has not been glaciated for the last 3.6 Ma. Biogenic silica was used for analysing the oxygen isotope composition (?18Odiatom) in the upper 13 m long section dating back about 250 ka with samples dominated by one taxa in the <10 ?m fraction (Cyclotella ocellata). Downcore variations in ?18O values show that glacial-interglacial cycles are present throughout the core and ?18Odiatom values are mainly controlled by ?18Oprecipitation. Changes reflect the Holocene Thermal Maximum, the Last Glacial Maximum and the interglacial periods corresponding to MIS 5e and MIS 7 with a peak-to-peak amplitude of ?18O = 5.3 ‰. Our record is the first continuous ?18Odiatom record from an Arctic lake sediment core directly responding to precipitation and dating back more than 250 ka and correlates well with the stacked marine ?18O LR04 (r = 0.58) and ?D EPICA Dome-C record (r = 0.69). With ?18O results indicating strong links to both marine and ice-core records, records from Lake El'gygytgyn can be used to further investigate the sensitivity of the Arctic climate to both past and future global climatic changes.

Chapligin, B.; Meyer, H.; Swann, G. E. A.; Meyer-Jacob, C.; Hubberten, H.-W.

2012-04-01

141

Diatom evidence for the timing and causes of eutrophication in Lake Victoria, East Africa  

Microsoft Academic Search

The determination of the history and causes of recent eutrophication and intensified thermal stratification in Lake Victoria\\u000a is still hampered by the sparsity of paleolimnologic coverage of the enormous lake. Five new diatom records from Ugandan waters\\u000a now show that a transition from Aulacoseira-dominated planktonic assemblages to those dominated by long Nitzschia spp., occurred in northern coastal sites from the

J. Curt StagerRobert; Robert E. Hecky; Dustin Grzesik; Brian F. Cumming; Hedy Kling

2009-01-01

142

Reproductive success of barn swallows nesting near a selenium-contaminated lake in east Texas, USA  

USGS Publications Warehouse

Reproductive success and contaminant levels in 1986 and 1987 were compared between Barn Swallows nesting at selenium-contaminated Martin Lake, Texas, USA, and swallows nesting at a reference site. Nests were initiated about the same time or earlier at Martin Lake than at the reference site and clutch size was similar between the two locations. Nest success was significantly higher at Martin Lake than at the reference site and no embryo or chick deformities were documented. Selenium concentrations in 14 of 20 eggs from Martin Lake were above background (> 3 ppm, dry weight); two of 20 eggs contained > 5 ppm, a concentration associated with a 20% embryo mortality/deformity rate in some bird species. Selenium concentrations in the kidneys of adult swallows were higher at Martin Lake (mean = 14 ppm dry weight) than at the reference site (5.8 ppm). DDE, the only detected organochlorine compound, was in two of 10 eggs from Martin Lake; these concentrations were below those associated with chronic poisoning and reproductive problems. The maximum mercury concentration in livers of adult Barn Swallows (0.83 ppm, dry weight) was within the range for background levels (< 5 ppm).

King, K.A.; Custer, T.W.; Weaver, D.A.

1994-01-01

143

Reproductive success of barn swallows nesting near a selenium-contaminated lake in east Texas, USA  

USGS Publications Warehouse

Reproductive success and contaminant levels in 1986 and 1987 were compared between Barn Swallows nesting at selenium-contaminated Martin Lake, Texas, USA, and swallows nesting at a reference site. Nests were initiated about the same time or earlier at Martin Lake than at the reference site and clutch size was similar between the two locations. Nest success was significantly higher a Martin Lake than at the reference site and no embryo or chick deformities were documented. Selenium concentrations in 14 of 20 eggs from Martin Lake were above background ( gt 3 ppm, dry weight); two of 20 eggs contained gt 5 ppm, a concentration associated with a 20% embryo mortality/deformity rate in some bird species. Selenium concentrations in the kidneys of adult swallows were higher at Martin Lake (mean = 14 ppm dry weight) than at the reference site (5.8 ppm). DDE, the only detected organochlorine compound, was in two of 10 eggs from Martin Lake; these concentrations were below those associated with chronic poisoning and reproductive problems. The maximum mercury concentration in livers of adult Barn Swallows (0.83 ppm, dry weight) was within the range for background levels ( lt 5 ppm).

King, K. A.; Custer, T. W.; Weaver, D. A.

1994-01-01

144

Seasonal variation of fish abundance and biomass in gillnet catches of an East Mediterranean lake: Lake Doirani.  

PubMed

The seasonal variation of fish species composition and abundance in gillnet catches (14-90 mm knot-to-knot) from the Greek part of the transboundary Lake Doirani was studied during the period 2006-2007. A total of 8,419 specimens weighing 182.3 kg and belonging to 9 species were caught. Catch composition differed with season. Thus, Rhodeus meridionalis dominated in terms of NPUE the spring, Perca fluviatilis the summer and Albumus macedonicus the autumn and winter catches. Cyprinids were generally the most abundant, with the cyprinids:percids biomass ratio ranging from 1.7 in summer to 14.8 in winter, supporting the eutrophic character of the lake. Richness and Shannon-Wiener diversity and evenness indices differed seasonally (ANOVA; p < 0.05). The abundance-biomass comparative (ABC) curves showed that fish communities were dominated by one or a few opportunistic species (e.g. Rhodeus meridionalis, Albumus macedonicus), which while dominated in number did not dominate in biomass, being small bodied. PMID:21506488

Bobori, Dimitra C; Salvarina, Ioanna

2010-11-01

145

Searching for life in extreme environments relevant to Jovian's Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica)  

NASA Astrophysics Data System (ADS)

The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice) from the subglacial Lake Vostok (Antarctica) buried beneath the 4-km thick East Antarctic ice sheet. The samples were extracted by heavy deep ice drilling from 3659 m below the surface. High pressure, a low carbon and chemical content, isolation, complete darkness and the probable excess of oxygen in water for millions of years characterize this extreme environment. A decontamination protocol was first applied to samples selected for the absence of cracks to remove the outer part contaminated by handling and drilling fluid. Preliminary indications showed the accretion ice samples to be almost gas free with a low impurity content. Flow cytometry showed the very low unevenly distributed biomass while repeated microscopic observations were unsuccessful.We used strategies of Ancient DNA research that include establishing contaminant databases and criteria to validate the amplification results. To date, positive results that passed the artifacts and contaminant databases have been obtained for a pair of bacterial phylotypes only in accretion ice samples featured by some bedrock sediments. The phylotypes included the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus and one unclassified phylotype. Combined with geochemical and geophysical considerations, our results suggest the presence of a deep biosphere, possibly thriving within some active faults of the bedrock encircling the subglacial lake, where the temperature is as high as 50 °C and in situ hydrogen is probably present.Our approach indicates that the search for life in the subglacial Lake Vostok is constrained by a high probability of forward-contamination. Our strategy includes strict decontamination procedures, thorough tracking of contaminants at each step of the analysis and validation of the results along with geophysical and ecological considerations for the lake setting. This may serve to establish a guideline protocol for studying extraterrestrial ice samples.

Bulat, Sergey A.; Alekhina, Irina A.; Marie, Dominique; Martins, Jean; Petit, Jean Robert

2011-08-01

146

High-latitude environmental change during MIS 9 and 11: biogeochemical evidence from Lake El'gygytgyn, Far East Russia  

NASA Astrophysics Data System (ADS)

Marine isotope stages (MIS) 11 has been proposed as an analog for the present interglacial; however, terrestrial records of this time period are rare. Sediments from Lake El'gygytgyn (67°30' N, 172°5' E) in Far East Russia contain a 3.56 Ma record of climate variability from the Arctic. Here, we present the first terrestrial Arctic reconstruction of environmental and climatic changes from MIS 8 through 12 (289 to 464 ka) using organic geochemical proxies. Terrestrial vegetation changes, as revealed by plant leaf wax (n-alkane) indices and concentrations of arborinol (a biomarker for trees), show increased tree cover around the lake during interglacial periods, with higher concentrations observed during MIS 11 as compared to MIS 9. A similar pattern is also observed in records of aquatic productivity revealed by molecular indicators from dinoflagellates (dinosterol), eustigmatophyte algae (long-chain (C28-C32) 1, 15 n-alkyl diols) in addition to short-chain n-alkanes, where aquatic productivity is highest during MIS 11. Changes recorded in these molecular proxies show a similar structure to relative temperature variability as recorded by the MBT/CBT (Methylation of Branched Tetraether/Cyclization of Branched Tetraether) paleothermometer, based on branched glycerol dialkyl glycerol tetraethers (GDGTs). Additionally, relative MBT/CBT temperature changes generally track pollen and diatom ?18O temperature estimates, compiled by other studies, which suggest glacial-interglacial temperature changes of ~ 9 to 12 °C. These records of environmental and climatic change indicate Arctic sensitivity to external forcings such as orbital variability and atmospheric greenhouse gas concentrations. Overall, this study indicates that organic geochemical analyses of the Lake El'gygytgyn sediment archive can provide critical insight into the response of lake ecosystems and their sensitivity in high latitude regions.

D'Anjou, R. M.; Wei, J. H.; Castañeda, I. S.; Brigham-Grette, J.; Petsch, S. T.; Finkelstein, D. B.

2013-03-01

147

Searching for life in extreme environments relevant to Jovian’s Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica)  

Microsoft Academic Search

The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice) from the subglacial Lake Vostok (Antarctica) buried beneath the 4-km thick East Antarctic ice sheet. The samples were extracted by heavy deep ice drilling from 3659m below the surface. High pressure, a low carbon and chemical content, isolation, complete darkness and the probable

Sergey A. Bulat; Irina A. Alekhina; Dominique Marie; Jean Martins; Jean Robert Petit

2011-01-01

148

GENE EXPRESSION ALTERATIONS OBSERVED IN PRIMARY CULTURED RAT HEPATOCYTES AFTER TREATMENT WITH CHLORINATED OR CHLORINATED AND OZONATED DRINKING WATER FROM EAST FORK LAKE, OHIO  

EPA Science Inventory

Drinking water from East Fork Lake was spiked with iodide and bromide, disinfected with chlorine or ozone + chlorine, concentrated ~100-fold using reverse osmosis, and volatile disinfection by-products (DBPs) added back. Primary rat hepatocytes were exposed to full-strength, 1:10...

149

High-resolution past environmental reconstruction in East Asia using annually laminated lake sediments of Lake Megata in northeastern Japan  

NASA Astrophysics Data System (ADS)

37 m-long non-glacial varved sequences were taken from Ichi-no-Megata maar in Oga Peninsula, Akita, northern part of Japan. Ichi-no-Megata maar occupies 0.25 km2 with a maximum water depth of ca. 45.1 m. The shape of lake is a kettle-type basin and the deepest bottom basin is very flat. We took core samples (named IMG06 core) at the center of the lake in November to December in 2006. In order to take completely continuous maar sediment, we drilled three holes and take every sample from each hole which apart only few meters. In this drilling campaign, we can 37 m-long continuous maar sediment except thick volcanic deposits from 26.5 to 31.7m in core. The sedimentological feature of IMG06 core is dominated by thin lamination clay/silt from most top part up to 37 m with turbidites characterized upward fining structure. The SEM image observation of lamination reveals that sponge-like lamina consists of diatom assemblage against dark colored lamina consists of mixture of detritus minerals, clay minerals, and diatom. It means sponge-like lamina deposits during spring season, and later one deposits during another three seasons, and then these thin lamination of IMG06 core could be identified as annual lamination (varves). This interpretation is supported by the correlation of historic event as earthquake and tunnel construction. In this IMG06 core, six volcanic ashes are found and we have also analyzed radiocarbon dating from 38 horizons of the core to use leaf and seeds inter-bedded varves. As the results, the IMG06 core covers from 25,000 to 4,000 14C yr BP with stable sedimentation rates (0.71mm/year).

Yamada, K.; Gotanda, K.; Yonenobu, H.; Shinozuka, Y.; Kitagawa, J.; Makohonienko, M.; Schwab, M.; Haraguchi, T.; Yasuda, Y.

2007-12-01

150

History and timing of human impact on Lake Victoria, East Africa.  

PubMed Central

Lake Victoria, the largest tropical lake in the world, suffers from severe eutrophication and the probable extinction of up to half of its 500+ species of endemic cichlid fishes. The continuing degradation of Lake Victoria's ecological functions has serious long-term consequences for the ecosystem services it provides, and may threaten social welfare in the countries bordering its shores. Evaluation of recent ecological changes in the context of aquatic food-web alterations, catchment disturbance and natural ecosystem variability has been hampered by the scarcity of historical monitoring data. Here, we present high-resolution palaeolimnological data, which show that increases in phytoplankton production developed from the 1930s onwards, which parallels human-population growth and agricultural activity in the Lake Victoria drainage basin. Dominance of bloom-forming cyanobacteria since the late 1980s coincided with a relative decline in diatom growth, which can be attributed to the seasonal depletion of dissolved silica resulting from 50 years of enhanced diatom growth and burial. Eutrophication-induced loss of deep-water oxygen started in the early 1960s, and may have contributed to the 1980s collapse of indigenous fish stocks by eliminating suitable habitat for certain deep-water cichlids. Conservation of Lake Victoria as a functioning ecosystem is contingent upon large-scale implementation of improved land-use practices.

Verschuren, Dirk; Johnson, Thomas C; Kling, Hedy J; Edgington, David N; Leavitt, Peter R; Brown, Erik T; Talbot, Michael R; Hecky, Robert E

2002-01-01

151

Phylogeny of a rapidly evolving clade: The cichlid fishes of Lake Malawi, East Africa  

Microsoft Academic Search

ABSTRACT Lake Malawi contains a f lock of >500 spe- cies of cichlid fish that have evolved from a common ancestor within the last million years. The rapid diversification of this group has been attributed to morphological adaptation and to sexual selection, but the relative timing and importance of these mechanisms is not known. A phylogeny of the group would

R. C. Albertson; J. A. M Arkert; P. D. D Anley; T. D. Kocher

1999-01-01

152

Microcrystalline sphalerite in resin globules suspended in Lake Kivu, East Africa  

USGS Publications Warehouse

The origin and chemical nature of micron-sized spheres found as suspended particles in Lake Kivu are examined. It can be shown that the hollow spheres, with a wall thickness of 500 A??, consist of a complex polymeric resinous material which has little functionality, except for hydroxyl groups. The spheres arise in the process of degassing of water samples at depth. Tiny gas bubbles, about 1 micron in size, act as scavengers of dissolved resinous material. The newly created resinous membrane promotes the selective coordination of zinc dissolved in the water column. In the prevailing H2S regime, formation of sphalerite crystals in induced. The size range of the crystals, 5 to 50 A??, corresponds to 1 to 10 unit cells and suggests that the resinous membrane also acts as a template in sphalerite growth processes. The sources of the zinc and dissolved gases (CO2, CH4, H2S) are hydrothermal springs seeping from the lake bottom into the basin. Water discharge is substantial; about 100 years are required to fill the lake to its present level (ca. 550 km3 water). The average Kivu water contains 2 ppm zinc. Thus, 1 million tons of zinc are contained in Lake Kivu in the form of sphalerite. ?? 1972 Springer-Verlag.

Degens, E. T.; Okada, H.; Honjo, S.; Hathaway, J. C.

1972-01-01

153

Microcrystalline sphalerite in resin globules suspended in Lake Kivu, East Africa  

Microsoft Academic Search

The origin and chemical nature of micron-sized spheres found as suspended particles in Lake Kivu are examined. It can be shown that the hollow spheres, with a wall thickness of 500 Å, consist of a complex polymeric resinous material which has little functionality, except for hydroxyl groups. The spheres arise in the process of degassing of water samples at depth.

E. T. Degens; H. Okada; S. Honjo; J. C. Hathaway

1972-01-01

154

DIATOM DIVERSITY IN HAUSBURG TARN, A GLACIAL LAKE ON MOUNT KENYA, EAST AFRICA  

Microsoft Academic Search

The investigation of 30 fossil diatom samples found in a 500-year sediment record from Hausburg Tarn, a glacial lake located in the Alpine zone of Mount Kenya, revealed a diatom diversity of 57 specific and infraspecific taxa. Of the eight taxa (14% of total species diversity) with a distribution restricted to the African continent, two species (3.5%) are unique to

Christine Cocquyt

2007-01-01

155

Tectonically controlled subglacial lakes on the flanks of the Gamburtsev Subglacial Mountains, East Antarctica  

Microsoft Academic Search

The morphology of surface lakes strongly influences their ecology and limnology (Wetzel, 2001). This morphology is a result of both the geologic processes that produce topographic basins and the regional climatic and local hydrologic processes that control water depth and sediment infilling (Carroll and Bohacs, 1999). Although basin forming processes range from glacial scour to meteorite impacts (Cohen, 2003), the

Robin E. Bell; Michael Studinger; Mark A. Fahnestock; Christopher A. Shuman

2006-01-01

156

Fluxes and distributions of core and intact tetraether membrane lipids in the water column of Lake Challa, East Africa  

NASA Astrophysics Data System (ADS)

Relative distributions of isoprenoid glycerol dialkyl glycerol tetraether (GDGT) membrane lipids derived from pelagic Crenarchaeota are used as sea surface temperature proxy TEX86. Similarly, the MBT/CBT proxy for annual mean air temperature (MAT) utilises distributions of branched GDGTs derived from soil bacteria. The ratio between branched and isoprenoid GDGTs (BIT index) is used in aquatic sediments as a proxy for the relative input of soil organic matter. Whereas the TEX86 proxy has been recently calibrated for and applied successfully in some lakes, the lacustrine application of the MBT/CBT proxy is still very much in its infancy. The debate centres on the possible in-situ production of branched GDGTs in lakes, as some studies have found a mismatch between the distributions of these GDGTs in catchment area soils versus those found in lake sediments. In order to investigate the potential of the MBT/CBT palaeotemperature proxy in lakes and to constrain its application, it is necessary to look at modern fluxes of GDGTs in lake systems to resolve the sources and distributions of these compounds. This study concentrates on Lake Challa, a stratified crater lake in equatorial East Africa. Twenty-six months of sediment trap material (Dec ‘07 to Jan ‘10) from 35m depth were analysed. Using a novel separation method, GDGTs are split into intact polar tetraether membrane lipids (IPLs) and core tetraether membrane lipids (CLs). IPLs are commonly believed to degrade rapidly upon cell lysis when the labile polar head group is hydrolysed, thereby converting the ‘living’ IPLs to the more stable ‘fossil’ CLs. This makes it possible, in theory, to use IPLs as a tracer for recently produced GDGTs. High fluxes of sedimenting intact GDGT-0 between September and November are clearly associated with the end of the annual diatom bloom (Jul-Aug). This suggests that methanogens are active even in the oxic waters above 35m depth. Crenarchaeotal lipid fluxes are generally low, leading to a relatively high BIT index for most of the year. However, during the annual bloom (Nov-Feb) both IPL and CL fluxes of crenarchaeol rise dramatically. This means that over this period of study, the BIT index is primarily controlled by Crenarchaeotal productivity rather than precipitation. Remarkably, high fluxes of both intact and core branched tetraethers do not correspond to observed precipitation events. MBT/CBT indices of both IPLs and CLs are similar, indicating that the two forms of tetraether likely share a single source. Notably, a seasonal trend in the MBT/CBT index is present; however, minima and maxima are apparently offset by 5-6 months from MAT. This would argue for at least an in-situ source next to an allochthonous source of sedimenting branched GDGTs in Lake Challa. However, a flux-weighted yearly average of branched GDGT distributions did yield annual MATs within the error margin of the MBT/CBT proxy.

Buckles, L. K.; Weijers, J.; Reichart, G.; Verschuren, D.; Sinninghe Damste, J. S.

2010-12-01

157

Hydrology of the Wolf Branch sinkhole basin, Lake County, east-central Florida  

USGS Publications Warehouse

A 4-year study of the hydrology of the Wolf Branch sinkhole basin in Lake County, Florida, was conducted from 1991-95 by the U.S. Geological Survey to provide information about the hydrologic characteristics of the drainage basin in the vicinity of Wolf Sink. Wolf Branch drains a 4.94 square mile area and directly recharges the Upper Floridan aquifer through Wolf Sink. Because of the direct connection of the sinkhole with the aquifer, a contaminant spill in the basin could pose a threat to the aquifer. The Wolf Branch drainage basin varies in hydrologic characteristics from its headwaters to its terminus at Wolf Sink. Ground- water seepage provides baseflow to the stream north of Wolf Branch Road, but the stream south of State Road 46 is intermittent and the stream can remain dry for months. A single culvert under a railroad crossing conducts flow from wetlands just south of State Road 46 to a well-defined channel which leads to Wolf Sink. The basin morphology is characterized by karst terrain, with many closed depressions which can provide intermittent surface-water storage. Wetlands in the lower third of the basin (south of State Road 46) also provide surface water storage. The presence of numerous water-control structures (impoundments, canals, and culverts), and the surface-water storage capacity throughout the basin affects the flow characteristics of Wolf Branch. Streamflow records for two stations (one above and one below major wetlands in the basin) indicate the flow about State Road 46 is characterized by rapid runoff and continuous baseflow, whereas below State Road 46, peak discharges are much lower but of longer duration than at the upstream station. Rainfall, discharge, ground-water level, and surface-water level data were collected at selected sites in the basin. Hydrologic conditions during the study ranged from long dry periods when there was no inflow to Wolf Sink, to very wet periods, as when nearly 7 inches of rain fell in a 2-day period in November 1994, following an extended wet season. A comparison to long-term rainfall record (40 years) indicates that this range in hydrologic conditions during the 4-year study is representative of the range of conditions expected during a much longer time period. Two dye-trace studies conducted during the study indicated no direct connections between the sink and local wells. The path of a constituent entering the aquifer through Wolf Sink generally would be to the east, following the gradient of the regional ground-water flow system. The conductance of Wolf Sink (the rate at which the sink conducts water to the underlying aquifer) was estimated from streamflow data, ground-water levels, and water levels in Wolf Sink. The range of hydrologic conditions during the study provided a basis for the determination of a representative conductance value. The regression of streamflow as a function of head difference between the sink water level and the potentiometric surface at an observation well (an approximation of the potentiometric level beneath Wolf Sink) resulted in a significant relation r2=0.91, mean square error = 1.60 cubic feet per second); and the slope of the regression line, representing sink conductance, was 1.48 cubic feet per second per foot of head difference. Flow and storm-volume frequency curves for selected time periods (1-day, 7-days, 14-days, 21-days, and 30-days) were generated based on streamflow data from January 10, 1992, to September 30, 1995. These curves indicate that, based on the available record, the volume of water that would have to be stored (in the event that streamflow had to be diverted from Wolf Sink) during a 30-day period would be equal to or less than about 11 acre-fee 30 percent of the time and 161 acre-feet 80 percent of the time. The maximum volume that would be generated during a 30-day period, based on this study, would be about 570 acre-feet.

Schiffer, D. M.

1996-01-01

158

Recent changes in the level of Lake Naivasha, Kenya, as an indicator of equatorial westerlies over East Africa  

Microsoft Academic Search

A previously unpublished record of lake levels from Lake Naivasha, Kenya from 1880 to 1976 has been analysed and shows little similarity to the level record from nearby Lake Victoria. Level changes from year to year of the two lakes show no significant correlation (at 5%) and spectral analysis of the two records shows no common significant peaks. Both lakes

C. E. Vincent; T. D. Davies; A. K. C. Beresford

1979-01-01

159

Late Holocene Centennial Records of Climate Change in Lake Hazar, East Anatolia, Turkey  

NASA Astrophysics Data System (ADS)

Gül Sürmelihindi, Naci Görür, M. Nami k ÇaÄ?atay Faculty of Mines, EMCOL (Eastern Mediterranean Centre for Oceanography and Limnology), Istanbul Technical University, 34469 Maslak Istanbul, Turkey e-mail: surmelihindie@itu.edu.tr Geochemical and physical property proxy analyses (stable oxygen and carbon isotopes, TOC, TIC, XRF Core Scanner, MSCL) of two sediment cores from the Lake Hazar indicate that the lake underwent significant centennial scale climatic changes during the last 4000 years. These changes were global in nature as suggested by the correlation of our proxy data with the ^ 18O isotope values of the Greenland's Ice Cores. Accelerator Mass Spectrometry 14C dating shows that some of the changes correspond to The Late Bronze Age to Early Iron Age transition, Medieval Warm Period and Little Ice Age.

Surmelihindi, G.; Gorur, N.; Cagatay, M. N.

2009-04-01

160

LONG-TERM CHANGES IN A BRACKISH LAGOON, LADY'S ISLAND LAKE, SOUTH-EAST IRELAND  

Microsoft Academic Search

Lady's Island Lake is a natural, percolating, coastal lagoon, isolated from the sea but subject to wide fluctuations in water-level and salinity as a result of more or less regular breaching of the dune barrier. Observations over seventeen years revealed changes in the salinity regime every two to four years, with poly-euhaline phases alternating with oligo-mesohaline phases. The dominant macrophytes

Brenda Healy

1997-01-01

161

Quantitative reconstruction of lake conductivity in the Quaternary of the Near East (Israel) using ostracods  

Microsoft Academic Search

Surface sediments, water samples and environmental data from 37 lakes, ponds and streams in Israel were analysed to determine\\u000a the main variables controlling ostracod species distributions. Multivariate statistical analysis revealed that the greatest\\u000a amounts of variation in the distribution of the ostracod taxa among the 37 water bodies were explained by the host water ?D\\u000a value (12.9%), water temperature (11.0%),

Steffen Mischke; Ahuva Almogi-Labin; Reuven Ortal; Arik Rosenfeld; Markus J. Schwab; Ian Boomer

2010-01-01

162

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

163

Remote forcing of East African rainfall and relationships with fluctuations in levels of Lake Victoria  

NASA Astrophysics Data System (ADS)

This study investigates the climatological variables responsible for fluctuations in Lake Victoria levels, in particular the causal mechanism responsible for a major anomaly that occurred in 1961. A Lake Victoria rainfall series (LVRS) correlates significantly (5%) with Lake Victoria levels and is utilized for subsequent analysis of rainfall variability. Relationships between annual and seasonal (March-May and October-December (OND)) LVRS and a number of tropical and extra-tropical series were analyzed. The results illustrate the dominance of the El Niño-Southern Oscillation phenomenon in modulating LVRS. The greatest correlation is found between LVRSOND and the Southern Oscillation index (r = -0.39, significant at the 1% level), although the relationship is non-linear over the course of the century.Velocity potential is employed as the principal diagnostic variable. Seasonal composite maps and empirical orthogonal function (EOF) analysis of Indian Ocean region -fields are utilized to test the hypothesis that an Indian Ocean Walker cell is responsible for the anomalous 1961 rainfall episode. Subsequent analysis leads to the rejection of this hypothesis. EOF analysis of OND 200 hPa -fields reveals a number of modes of tropical variability. EOF analysis of the Indian Ocean basin illustrates the emergence of a meridional circulation directed over the Indian Ocean (EOF5). This time series correlates significantly with LVRSOND (r = -0.40, 1% level), although the spatial pattern only explains a small proportion (2.35%) of the total variance. analysis for OND over the broader tropical region reveals significant relationships (5%) between OND EOF3* and July-September Sahel rainfall for the preceding season and subsequent year. This relationship may assist future long-lead seasonal forecast schemes for the Sahel region.

Mistry, Vinay V.; Conway, Declan

2003-01-01

164

8. EAST PORTAL AND DECK VIEW, FROM EAST, SHOWING PORTAL ...  

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

8. EAST PORTAL AND DECK VIEW, FROM EAST, SHOWING PORTAL CONFIGURATION AND LATERAL BRACING, STEEL MESH FLOOR, METAL RAILINGS, AND PORTION OF EAST APPROACH - Glendale Road Bridge, Spanning Deep Creek Lake on Glendale Road, McHenry, Garrett County, MD

165

The Potential Link Between El Nino and Water Hyacinth Blooms in Winam Gulf of Lake Victoria, East Africa: Evidence from Satellite Imagery  

Microsoft Academic Search

This study evaluates the link between the occurrence of El Nino events in East Africa and water hyacinth blooms in Winam Gulf\\u000a of Lake Victoria using remote sensing technology. A time-series of the Normalized Difference Vegetation Index (NDVI) analyzed\\u000a from data acquired by the multispectral Aqua\\/Terra sensors aboard the Moderate Resolution Imaging Spectroradiometer (MODIS)\\u000a satellite are used to monitor areal

Lawrence M. Kiage; Joyce Obuoyo

166

Recent land?cover\\/use change associated with land degradation in the Lake Baringo catchment, Kenya, East Africa: evidence from Landsat TM and ETM+  

Microsoft Academic Search

Many parts of East Africa are experiencing dramatic changes in land?cover\\/use at a variety of spatial and temporal scales, due to both climatic variability and human activities. Information about such changes is often required for planning, management, and conservation of natural resources. Several methods for land cover\\/change detection using Landsat TM\\/ETM+ imagery were employed for Lake Baringo catchment in Kenya,

L. M. Kiage; N. D. Walker; N. Lam; O. K. Huh

2007-01-01

167

Variation and distribution of total mercury in water, sediment and soil from northern Lake Victoria, East Africa  

Microsoft Academic Search

Lake Victoria, the world's largest tropical freshwater lake, is an important resource, ecologically and economically. THg distribution in the northern parts of the lake are not well known, so to answer this gap, patterns in total mercury (THg) in water, soil and two dated sediment cores from northern Lake Victoria were determined. Water THg concentrations ranged from 0.7 to 5.8

L. M. Campbell; R. E. Hecky; R. Muggide; D. G. Dixon; P. S. Ramlal

2003-01-01

168

Variation and distribution of total mercury in water, sediment and soil from northern Lake Victoria, East Africa  

Microsoft Academic Search

Lake Victoria, the world's largest tropical freshwater lake, is an important resource, ecologi- cally and economically. THg distribution in the northern parts of the lake are not well known, so to answer this gap, patterns in total mercury (THg) in water, soil and two dated sediment cores from north- ern Lake Victoria were determined. Water THg concentrations ranged from 0.7

L. M. CAMPBELL; R. E. HECKY; R. MUGGIDE; D. G. DIXON

2003-01-01

169

East Tibetan lakes harbour novel clusters of picocyanobacteria as inferred from the 16S-23S rRNA internal transcribed spacer sequences.  

PubMed

Planktonic picocyanobacteria abundance and diversity were investigated in nine lakes on the East Tibetan Plateau spanning a salinity gradient of 0.4-22.6 g l(-1). The investigation was conducted using epifluorescence microscopy (EFM) and terminal restriction fragment polymorphism analysis of 16S-23S rRNA internal transcribed spacer (ITS) PCR amplicons followed by sequence analyses of large ITS clone libraries of seven selected samples. EFM showed that picocyanobacteria comprised 7-19% of the total prokaryotic cells found in surface water. Most of the clones were classified into six clusters and grouped within the "picocyanobacterial clade", which consists exclusively of freshwater Synechococcus. Four new phylogenetic clusters and one new subcluster of Synechococcus spp. were found, none of which are members of any known picocyanobacterial clusters. The new clusters and subcluster were the most abundant picocyanobacteria (about 96% of the sequences) in the samples collected. Sequence analyses indicated that members of the four new Synechococcus groups were only found in freshwater lakes (<1.0 g l(-1) of total dissolved solid), while members of the new subcluster were found in all the investigated Tibetan lakes, over a large salinity gradient of 0.4-22.6 g l( -1). This suggests that there is ecologically significant microdiversity within the observed Synechococcus group as defined by ITS sequences. Collectively our study demonstrated abundant and potentially novel Synechococcus in East Tibetan lakes that are likely the result of evolutionary adaptations to regional conditions. PMID:19904569

Wu, Qinglong L; Xing, Peng; Liu, Wen-Tso

2009-11-12

170

Nesterenkonia lacusekhoensis sp. nov., isolated from hypersaline Ekho Lake, East Antarctica, and emended description of the genus Nesterenkonia.  

PubMed

An aerobic and heterotrophic isolate, designated IFAM EL-30T, was obtained from hypersaline Ekho Lake (Vestfold Hills, East Antarctica). The isolate consisted of Gram-positive cocci or short rods which occasionally exhibited branching. The organism was moderately halotolerant, required thiamin.HCI and was stimulated by biotin and nicotinic acid. It grew well with glucose, acetate, pyruvate, succinate, malate or glutamate, and hydrolysed DNA but not gelatin, starch or Tween 80. Nitrate was aerobically reduced to nitrite. Chemical analysis revealed diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine and an unidentified glycolipid as the major polar lipids. The cellular fatty acids were predominantly of the anteiso and iso methyl-branched types, and the major menaquinone6 were MK-7 and MK-8. The peptidoglycan type was A4alpha, L-Lys-L-Glu. The DNA base ratio was 66.1 mol% G+C. Comparisons of 16S rRNA gene sequences showed that the unidentified organism was phylogenetically closely related to Nesterenkonia halobia, although a sequence divergence value of > 3% demonstrated that the organism represents a different species. On the basis of phenotypic and genotypic evidence, it is proposed that the unknown bacterium be designated as a new species of the genus Nesterenkonia, namely Nesterenkonia lacusekhoensis sp. nov., the type strain being IFAM EL-30T (= DSM 12544T = CIP 107030T). An emended description of the genus Nesterenkonia is given. PMID:12148619

Collins, Matthew D; Lawson, Paul A; Labrenz, Matthias; Tindall, Brian J; Weiss, N; Hirsch, Peter

2002-07-01

171

Vegetation responses to interglacial warming in the Arctic: examples from Lake El'gygytgyn, Far East Russian Arctic  

NASA Astrophysics Data System (ADS)

Preliminary analyses of Lake El'gygytgyn sediment indicate a wide range of ecosystem responses to warmer than present climates. While palynological work describing all interglacial vegetation is ongoing, sufficient data exist to compare recent warm events (the postglacial thermal maximum, PGTM, and marine isotope stage, MIS5) with "super" interglaciations (MIS11, MIS31). Palynological assemblages associated with these climatic optima suggest two types of vegetation responses: one dominated by deciduous taxa (PGTM, MIS5) and the second by evergreen conifers (MIS11, MIS31). MIS11 forests show a similarity to modern Picea-Larix-Betula-Alnus forests of Siberia. While dark coniferous forest also characterizes MIS31, the pollen taxa show an affinity to the boreal forest of the lower Amur valley (southern Russian Far East). Despite vegetation differences during these thermal maxima, all glacial-interglacial transitions are alike, being dominated by deciduous woody taxa. Initially Betula shrub tundra established and was replaced by tundra with tree-sized shrubs (PGTM), Betula woodland (MIS5), or Betula-Larix (MIS11, MIS31) forest. The consistent occurrence of deciduous forest and/or high shrub tundra before the incidence of maximum warmth underscores the importance of this biome for modeling efforts. The El'gygytgyn data also suggest a possible elimination or massive reduction of Arctic plant communities under extreme warm-earth scenarios.

Lozhkin, A. V.; Anderson, P. M.

2013-06-01

172

The subglacial Lake Vostok (East Antarctica) surface snow is Earth-bound DNA (and dust)-free  

NASA Astrophysics Data System (ADS)

The objective was to assess the microbial cell abundance in the surface snow in Central East Antarctica and the fate of microbial genomic DNA during summer short-time exposure to surface climatic (and radiation) conditions at Vostok using flow cytometry and DNA-based methods. The surface snow (until 4m deep) was collected as clean as possible in the vicinity of the Vostok station (3 sites - courtesy of A Ekaykin and ASC Lebedev Physical Iinstitute RAS) and towards the Progress station (4 more sites with one just 29km from the coast - courtesy of A Ekaykin and S Popov) in specially decontaminated plastic crates or containers of various volumes (up to 75 kg of snow). All subsequent snow treatment manipulations (melting, concentrating, genomic DNA extraction, primary PCR set up) were performed in clean room laboratory facilities (LGGE, UJF-CNRS, Grenoble, France). Cell concentrations were determined on meltwater aliquots prepared under clean room conditions using flow cytofluorometry (Biostation, Roscoff, France). The highly concentrated meltwater (until 10000 times down) was used to extract gDNA which were subjected to bacterial 16S rRNA genes amplification in PCR and sequencing. The gDNA of a complex mesophile microbial community for exposure trials were also prepared and put onto a filter under strict clean room conditions. The filters were got exposed open to solar radiation and surface temperature at Vostok during January for various time duration periods (from 25 to 1 day). As a result no microbial cells were confidently detected in surface snow samples differed by sampling sites and people asked to collect as well. Complementary the mineral dust particle abundance did not exceed 16 mkg per liter with the particle size mode about 2.5 mkm as shown using Coulter counter. Preliminary amongst the microparticles no unusual findings (e.g. spherules of cosmic origin) were observed by shape and element composition using electron scanning microscopy. The gDNA studies came up with only contaminant bacterial phylotypes (mostly of human source). The bioexposure trials showed that even in one day of open exposure the gDNA of rather complex microbial community composition was fatally damaged in terms of long-, mid-range and short-size amplicon generation in PCR. All this testify for very harsh conditions for life to survive the climate conditions of Central East Antarctica which could be considered as a presentday 'zone mortale' or 'polar desert' for known Earthbound microbial life forms. In addition this means that no life seeds are expected to reach subglacial lakes and water reservoirs and establish indigenous lake microbiota during their transit through the thick and aged Antarctic ice sheet upon its bottom melting. In general the subglacial Lake Vostok surface (ice sheet as well) environ represents the unique test area (sterile - in fact Earth-bound DNA-free and clean - in fact Earth-bound dust-free) for advancing extraterrestrial (ET) life detection technologies and searching for ET life indices in AMMs and IDPs.

Bulat, S.; Marie, D.; Bulat, E.; Alekhina, I.; Petit, J.-R.

2012-09-01

173

Distribution and Food-web Transfer of Mercury in Napoleon and Winam Gulfs, Lake Victoria, East Africa  

Microsoft Academic Search

Mercury (Hg) concentrations were measured for the food webs and water of Napoleon Gulf (Uganda) and Winam Gulf (Kenya) in northern Lake Victoria. Water total mercury (THg) concentrations in Lake Victoria range from 1.7 to 5.8 ng\\/L, while methylmercury (MeHg) concentrations range from 0.2 to 1 ng\\/L. Water Hg concentrations in Lake Victoria are higher than in temperate great lakes,

Linda M. Campbell; Robert E. Hecky; Joseph Nyaundi; Rose Muggide; D. George Dixon

2003-01-01

174

Lake Challa (Kenya/Tanzania) sediments, a varved climate archive of environmental variability in equatorial East Africa of the last 25.000 years  

NASA Astrophysics Data System (ADS)

Recently, an increasing number of climate records from low-latitude regions underscore the importance of tropical atmospheric processes in the global climate system. Nevertheless, the regional synchrony of temperature and humidity variations, as well as teleconnecting mechanisms between high and low latitudes are still poorly understood. The EuroCLIMATE project CHALLACEA aims to provide a continuous high- resolution multi-proxy record of temperature and moisture-balance variability in equatorial East Africa from the Last Glacial Maximum (25 ka BP) to the present. Lake Challa is a crater lake located about 40 km east of Mt. Kilimanjaro at an altitude of 880 m a.s.l. It is a freshwater lake whose water column is stratified during most of the year. It is fed by subsurface inflow which derives mainly from percolation of precipitation falling in the montane forest zone higher up the mountain. Within the lake form lacustrine deposits which predominantly consist of autochthonous components (carbonate, biogenic silica, organic matter). The present study focuses on microfacies analyses and isotope measurements. Fine laminations are preserved over wide parts of a 22 m long sediment profile. Microfacies analyses reveal that the light/dark couplets represent true calcite varves. The darker layers contain organic matter and endogenic calcite. Sediment trap studies show that these layers form during the warm season (Nov to Mar) when water temperatures are high and the lake is biological productive. The light layers consist predominantly of diatom frustules. They accumulate in the sediment trap between June and October. By counting and measuring the thickness of the varves on thin sections, we establish a varve record that currently covers the last 1500 years. Stable isotope analyses on bulk carbonates will complement this record and give further insights into the hydrological variability of the region and enhance our knowledge of climate change in the highly sensitive climate region of the Mt. Kilimanjaro area.

Wolff, C.; Haug, G.; Plessen, B.; Kristen, I.; Verschuren, D.; Participants, C.

2008-12-01

175

27. View east, foreground north facade of Forest Hall, background ...  

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

27. View east, foreground north facade of Forest Hall, background north facade of Forest East Suites. - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

176

19. View west, foreground, north facade of Forest East Suites, ...  

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

19. View west, foreground, north facade of Forest East Suites, background north & east facades of Forest Hall. - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

177

A biomarker record of Lake El'gygytgyn, Far East Russian Arctic: investigating sources of organic matter and carbon cycling during marine isotope stages 1-3  

NASA Astrophysics Data System (ADS)

Arctic paleoenvironmental archives serve as sensitive recorders of past climate change. Lake El'gygytgyn (Far East Russian Arctic) is a high-latitude crater impact lake that contains a continuous sediment record influenced by neither glaciation nor glacial erosion since the time of impact 3.58 Ma ago. Prior research on sediments collected from Lake El'gygytgyn suggest times of permanent ice cover and anoxia corresponding to global glacial intervals, during which the sediments are laminated and are characterized by the co-occurrence of high total organic carbon, microscopic magnetite grains that show etching and dissolution, and negative excursions in bulk sediment organic matter carbon isotope (?13C) values. Here we investigate the abundance and carbon isotopic composition of lipid biomarkers recovered from Lake El'gygytgyn sediments spanning marine isotope stages 1-3 to identify key sources of organic matter (OM) to lake sediments, to establish which OM sources drive the negative ?13C excursion exhibited by bulk sediment OM, and to explore if there are molecular and isotopic signatures of anoxia in the lake during glaciation. We find that during marine isotope stages 1-3, direct evidence for water column anoxia is lacking. A ~4‰ negative excursion in bulk sediment ?13C values during the Local Last Glacial Maximum (LLGM) is accompanied by more protracted, higher magnitude negative excursions in n-alkanoic acid and n-alkanol ?13C values that begin 20 kyr in advance of the LLGM. In contrast, n-alkanes and the C30 n-alkanoic acid do not exhibit a negative ?13C excursion at this time. Our results indicate that the C24, C26 and C28 n-alkanoic acids do not derive entirely from terrestrial OM sources, while the C30 n-alkanoic acid at Lake El'gygytgyn is a robust indicator of terrestrial OM contributions. Overall, our results strongly support the presence of a nutrient-poor water column, which is mostly isolated from atmospheric carbon dioxide during glaciation at Lake El'gygytgyn.

Holland, A. R.; Petsch, S. T.; Castañeda, I. S.; Wilkie, K. M.; Burns, S. J.; Brigham-Grette, J.

2013-01-01

178

Tectonic Evolution of the Northern Malawi rift, East Africa: Structural Controls on Sediment Dispersal in a Large Lake Basin.  

NASA Astrophysics Data System (ADS)

The Malawi Rift is an integral part of the East African Rift system (EARs), the type example of a rift system in its youthful stages of development. Understanding the spatio-temporal evolution of this rift system provides insights into the past histories and controls on more ancient rift basins. Fundamental questions remain regarding the structural styles, partitioning, and sediment dispersal patterns within large lacustrine basins that are common to young rifts. Such basins are particularly useful recorders of climatic fluctuations. In areas with pronounced climatic variability and high evaporation/precipitation ratios this may lead to, often transient, basin isolation that may dramatically affect sediment and facies distribution. We investigate the structural evolution and sedimentation patterns of the North basin, Malawi Rift. We utilise two seismic reflection data sets: the first, collected by project PROBE, records the entire basin-fill (Sequences 1-3) at medium resolution; the second provides a closely-spaced high-resolution survey of the past ~1 Ma (Sequence 3). These data document the development of the basin-bounding and intra-basin faults. Throughout its history, the basin-bounding fault has accommodated the greatest strain and therefore exerted the fundamental control on the distribution of sediment within the rift. Present-day sediments enter the basin axially, although there is evidence that transverse supply was also important in the past. We identify 11 intra-basin structures that strike parallel or sub-parallel to this border fault. These intra-basin faults, active from the earliest stages, have initial segment lengths of ~30 km, but rapidly reach lengths in excess of 80 km in the north of the basin, and 60 km in the south. Much of the sedimentation along the faults occurred during Sequence 2 (~2.7-1.6 Ma), a period of relative over-filling of the basin. While the basin-bounding fault controls the overall sediment architecture, all 11 intra-basin structures have remained active and have, in particular during the most recent depositional history, played an important role in sediment dispersal within the basin during lake-level lowstands. Such long-lengths and long-lived activity on almost exclusively synthetic intra-basin faults is, however, unusual. This pattern is possibly attributed to one or a combination of factors including: underlying structural fabrics; the geometry of the detachment at depth; sediment loading at the mouths of feeder systems; or loading by a volcanic centre to the north.

Mortimer, E.; Paton, D.; Scholz, C.; Strecker, M.

2005-12-01

179

The spatial and temporal distribution of fossil-fuel dervied pollutants in the sediment record of Lake Baikal, east Siberia  

Microsoft Academic Search

Spatial and temporal patterns of spheroidal carbonaceous particles (SCP) extracted from lake sediments provide an unambiguous record of the distributions of fossil-fuel derived pollutants. When applied to sediment cores taken from Lake Baikal spatial patterns show good agreement with the distribution of industry, with the highest concentrations found in the southern basin nearest to Irkutsk. SCP were found to occur

N. L. Rose; P. G. Appleby; J. F. Boyle; A. W. Mackay; R. J. Flower

1998-01-01

180

NORTH GATE AT 11TH AVENUE (490 NORTH & 900 EAST), ...  

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

NORTH GATE AT 11TH AVENUE (490 NORTH & 900 EAST), SALT LAKE CITY, UT. VIEW LOOKING SOUTH AT CEMETERY'S NORTH GATE (WPA PROJECT, 1938-1941). - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

181

WEST PIER OF NORTH GATE (490 NORTH & 900 EAST), ...  

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

WEST PIER OF NORTH GATE (490 NORTH & 900 EAST), SALT LAKE CITY, UT. VIEW LOOKING SOUTH AT THE WEST PIER OF THE CEMETERY'S NORTH GATE. - Salt Lake City Cemetery, 200 N Street, Salt Lake City, Salt Lake County, UT

182

Linking isoprenoidal GDGT membrane lipid distributions with gene abundances of ammonia-oxidizing Thaumarchaeota and uncultured crenarchaeotal groups in the water column of a tropical lake (Lake Challa, East Africa).  

PubMed

Stratified lakes are important reservoirs of microbial diversity and provide habitats for niche differentiation of Archaea. In this study, we used a lipid biomarker/DNA-based approach to reveal the diversity and abundance of Archaea in the water column of Lake Challa (East Africa). Concentrations of intact polar lipid (IPL) crenarchaeol, a specific biomarker of Thaumarchaeota, were enhanced (1?ng l(-1) ) at the oxycline/nitrocline. The predominance of the more labile IPL hexose-phosphohexose crenarchaeol indicated the presence of an actively living community of Thaumarchaeota. Archaeal 16S rRNA clone libraries revealed the presence of thaumarchaeotal groups 1.1a and 1.1b at and above the oxycline. In the anoxic deep water, amoA gene abundance was an order of magnitude lower than at the oxycline and high abundance (??90?ng l(-1) ) of an IPL with the acyclic glycerol dialkyl glycerol tetraether (GDGT-0) was evident. The predominance of archaeal 16S rRNA sequences affiliated to the uncultured crenarchaeota groups 1.2 and miscellaneous crenarchaeotic group (MCG) points to an origin of GDGT-0 from uncultured crenarchaeota. This study demonstrates the importance of thermal stratification and nutrient availability in the distribution of archaeal groups in lakes, which is relevant to constrain and validate temperature proxies based on archaeal GDGTs (i.e. TEX86 ). PMID:23560451

Buckles, Laura K; Villanueva, Laura; Weijers, Johan W H; Verschuren, Dirk; Damsté, Jaap S Sinninghe

2013-04-08

183

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

184

Late Glacial–Holocene diatom record of water chemistry and lake level change from the tropical East African Rift Lake Abiyata (Ethiopia)  

Microsoft Academic Search

Diatom study of a 12.6-m long sediment core (AB95II) from Lake Abiyata (Ethiopian Rift, ?8°N) revealed large amplitude changes in the water level and chemistry over the past 13.4 cal kyr BP. Past water conductivity, pH and water chemical facies, reflected by ionic ratios, are quantitatively reconstructed, based on diatom transfer functions previously established. Conductivity has varied from 400 to

Françoise Chalié; Françoise Gasse

2002-01-01

185

Genetically distinct strains of Cassava brown streak virus in the Lake Victoria basin and the Indian Ocean coastal area of East Africa.  

PubMed

Six isolates of Cassava brown streak virus (CBSV, genus Ipomovirus; Potyviridae) from the Lake Victoria basin in Uganda and Tanzania were characterized. Virus particles were 650 nm long. The complete coat protein (CP)-encoding sequences (1,101 nucleotides, nt) were 90.7-99.5 and 93.7-99.5% identical at the nt and amino acid (aa) levels, respectively. The 3' untranslated region was 225, 226 or 227 nt long. These eight isolates were only 75.8-77.5% (nt) and 87.0-89.9% (aa) identical when compared to the partial CP sequences (714 nt) of six CBSV isolates characterized previously from the costal lowlands of Tanzania and Mozambique. Hence, two genetically different and geographically separated populations of CSBV exist in East Africa. PMID:19184340

Mbanzibwa, D R; Tian, Y P; Tugume, A K; Mukasa, S B; Tairo, F; Kyamanywa, S; Kullaya, A; Valkonen, Jari P T

2009-01-30

186

The evolutionary relationships of two families of cottoid fishes of Lake Baikal (east Siberia) as suggested by analysis of mitochondrial DNA.  

PubMed

Fragments of mtDNA genes Cyt B, ATPase 6, and ATPase 8 of six cottoid fishes species of Lake Baikal (East Siberia) were amplified and sequenced. In addition mtDNAs of the same fish were subjected to restriction analysis. The data obtained were used to construct phylogenetic trees. The topology of the ATPase tree differs from those of the Res (restriction) and Cyt B trees. Clustering of species within the trees confirms the viewpoint of Taliev (1955, Baicalian Sculpins (Cottoidei)) according to which Baikalian cottoids originate from two ancestral forms. The times of branching obtained do not confirm the existing viewpoint according to which the two golomyankas (Comephorus baicalensis and Comephorus dybowskii) are pre-Baikal (Myocene) relicts: these two species may have originated 1.2-1.8 million years ago in Baikal, and they seem to represent an example of rapid morphological evolution which resulted in the formation of a new family. PMID:7769616

Slobodyanyuk SJa; Kirilchik, S V; Pavlova, M E; Belikov, S I; Novitsky, A L

1995-04-01

187

Bioaccumulation of heavy metals in mullet (Mugil cephalus) and oyster (Crassostrea madrasensis) from Pulicat lake, south east coast of India.  

PubMed

The accumulation of six heavy metals (Cr, Cd, Cu, Zn, Pb and Ni) in sediment, water and in tissue parts of Mugil cephalus and Crassostrea madrasensis was studied in two locations of Pulicat lake, Southeast coast of India, which receives considerable quantity of effluents from industries located in North Chennai coastal region. The results reveal that the metal concentration in water is decreasing in the following order of Zn > Ni > Cu > Cr > Pb > Cd both in lake and barmouth and highest concentration was observed for Zn (32.5 ?g L(-1) in lake and 25.2 ?g L(-1) in bar mouth). Metals were highly concentrated in sediments when compared to water and biota. Metals abundance in sediments has following sequential order of Cr > Ni > Zn > Cu > Pb > Cd and the accumulation pattern in barmouth showed minor variation indicating the following pattern of Zn > Ni > Cr > Cu > Pb > Cd. The geoaccumulation index (I(geo)) for Pulicat lake sediments indicate that the sediments are extremely contaminated with Cd and moderately contaminated with Cu and Ni. Bioaccumulation of heavy metals in Mugil cephalus and Crassostrea madrasensis showed marked differences in the accumulation patterns. It is observed that Zn, Cu and Pb are accumulated in elevated concentrations in various parts of the fish and oyster when compared with other metals. PMID:20921056

Laxmi Priya, S; Senthilkumar, B; Hariharan, G; Paneer Selvam, A; Purvaja, R; Ramesh, R

2010-10-04

188

Preliminary assessment of heavy metal contamination in surface water and sediments from Honghu Lake, East Central China  

NASA Astrophysics Data System (ADS)

Heavy metal concentrations in surface water and sediments collected from Honghu Lake in Hubei Province, China were analyzed, and ecological risks were evaluated according to the sediment quality guidelines. The results showed that the average concentrations of heavy metals in surface water were ranked as: As>Zn> Cu>Cr>Pb>Ni>Cd>Hg. In comparison with results reported in other rivers and the background values, The Honghu Lake was polluted by As, Cr, Pb, Cu and Ni. Most of metals might be mainly from fertilizers, industrial effluent and domestic wastewater around the lake. Heavy metals concentrations were relatively higher in the inlet area than in other areas. Negative correlations were observed between most heavy metals and pH, while a significant positive correlation was present between Zn, Cd and Pb. In the sediment core, Cu, Zn, Cr and Ni showed a decreasing trend while Cd present an increasing trend. The decrease of As, Cu, Zn, Cr and Ni in the 1990s might due to the flood event in 1998. The analysis of ecological risk assessment based on sediment quality guidelines suggested that heavy metals in most sediments from the Honghu Lake had moderate toxicity, with Cr being the highest priority pollutant.

Hu, Ying; Qi, Shihua; Wu, Chenxi; Ke, Yanping; Chen, Jing; Chen, Wei; Gong, Xiangyi

2012-03-01

189

Lake-groundwater relationships and fluid-rock interaction in the East African Rift Valley: isotopic evidence  

Microsoft Academic Search

The assessment of water resources in the Rift Valley environment is important for population, agriculture and energy-related issues and depends on a good understanding of the relationship between freshwater lakes and regional groundwater. This can be hampered by the amount of fluid-rock interaction which occurs throughout the rift, obscuring original hydrochemical signatures. However, O and H stable isotope ratios can

W. George Darling; Berhanu Gizaw; Musa K. Arusei

1996-01-01

190

Secondary production and energetics of the shrimp Caridina nilotica in Lake Victoria, East Africa: model development and application  

Microsoft Academic Search

Measurements of body mass, carbon content, respiration, growth, and egestion are combined in a model of secondary production by the tropical freshwater shrimp Caridina. The model is developed to permit its direct application to empirical data for abundances and size frequency distributions of field populations. Model calculations combined with population data for offshore Lake Victoria over a period of two

Marcy Ignatow; Godfrey Mbahinzireki; John T. Lehman

1996-01-01

191

Impact of canal development on intertidal microalgal productivity: Comparative assessment of Patterson Lakes and Ralphs Bay, South East Australia  

Microsoft Academic Search

We assessed the potential impact of a proposed canal development in an estuarine sandflat at Ralphs Bay, Tasmania on intertidal microalgal productivity and species composition, by comparing it over summer and winter seasons with a well- established (30 year old) canal estate at Patterson Lakes, Victoria. Pulse amplitude modulation (PAM) fluorometry was used to generate a relative measure of photosynthetic

S. S. Cook; J. L. Roberts; G. M. Hallegraeff; A. McMinn

2007-01-01

192

Biophysical Suitability of Smallholder Integrated Aquaculture-Agriculture Systems (Fingerponds) in East Africa's Lake Victoria Freshwater Wetlands  

Microsoft Academic Search

Most riparian communities living along the shores of Lake Victoria rely on wetland farming or harvesting of natural wetland products for their livelihoods. The benefits from these ecosystems can be enhanced through smallholder aquaculture systems that can be integrated into existing farming activities. Ponds dug into the wetlands can be used for fish production while excavated soil is used to

J. KIPKEMBOI; A. A. VAN DAM; P. DENNY

193

75 FR 53735 - Notice of Final Federal Agency Actions on East Lake Sammamish Master Plan Trail in King County, WA  

Federal Register 2010, 2011, 2012, 2013

...starting at Gilman Boulevard in Issaquah, Washington and ending at Bear Creek Trail in Redmond, Washington. Those actions grant licenses...side of Lake Sammamish from Gilman Boulevard in Issaquah, WA to Bear Creek Trail in Redmond, WA. The project will be an...

2010-09-01

194

Geochemical fractionation of heavy metals in Chilka Lake (east coast of India)—a tropical coastal lagoon  

Microsoft Academic Search

Chilka lake, the largest coastal lagoon of Asia is one of the most dynamic ecosystems along the Indian coast. Historically the lagoon has undergone a considerable reduction in surface area due, in part, to input from natural processes but mostly due to human activities. The purpose of this investigation is to document the heavy metals' affinity for specific geochemical phases

D. Panda; V. Subramanian; R. C. Panigrahy

1995-01-01

195

A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic: refining the pattern of climate modes by means of cluster analysis  

NASA Astrophysics Data System (ADS)

Rock magnetic, biochemical and inorganic records of the sediment cores PG1351 and Lz1024 from Lake El'gygytgyn, Chukotka peninsula, Far East Russian Arctic, were subject to a hierarchical agglomerative cluster analysis in order to refine and extend the pattern of climate modes as defined by Melles et al. (2007). Cluster analysis of the data obtained from both cores yielded similar results, differentiating clearly between the four climate modes warm, peak warm, cold and dry, and cold and moist. In addition, two transitional phases were identified, representing the early stages of a cold phase and slightly colder conditions during a warm phase. The statistical approach can thus be used to resolve gradual changes in the sedimentary units as an indicator of available oxygen in the hypolimnion in greater detail. Based upon cluster analyses on core Lz1024, the published succession of climate modes in core PG1351, covering the last 250 ka, was modified and extended back to 350 ka. Comparison to the marine oxygen isotope (?18O) stack LR04 (Lisiecki and Raymo, 2005) and the summer insolation at 67.5° N, with the extended Lake El'gygytgyn parameter records of magnetic susceptibility (?LF), total organic carbon content (TOC) and the chemical index of alteration (CIA; Minyuk et al., 2007), revealed that all stages back to marine isotope stage (MIS) 10 and most of the substages are clearly reflected in the pattern derived from the cluster analysis.

Frank, U.; Nowaczyk, N. R.; Minyuk, P.; Vogel, H.; Rosén, P.; Melles, M.

2013-07-01

196

Evolution of the mitochondrial DNA control region in the mbuna (Cichlidae) species flock of lake Malawi, East Africa  

Microsoft Academic Search

Considerable controversy has surrounded the application of mitochondrial DNA data to reconstruction of evolutionary relationships\\u000a among the endemic cichlids of Lake Malawi. Central to this debate has been the issue of whether lineage sorting is complete,\\u000a and thus whether these data actually reflect species phylogeny, or simply gene genealogy. Review of all mtDNA control region\\u000a sequences available for members of

Alex Parker; Irv Kornfield

1997-01-01

197

The twilight of Paleolithic Siberia: Humans and their environments east of Lake Baikal at the late-glacial\\/Holocene transition  

Microsoft Academic Search

Numerous archaeological sites in Eastern Siberia and the Russian Far East are assigned to the Younger Dryas that testify to human occupation of the area despite a re-advance of steppe biota beginning around 11,000 14C BP (ca. 12,850 cal BP). Archaeological sites are primarily associated with low-energy alluvial landforms where preservation is excellent, but some are heavily disturbed by cryogenic

Ian Buvit; Karisa Terry

2011-01-01

198

30. VIEW TO NORTH NORTHWEST FROM EAST SIDE OF WELLS ...  

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

30. VIEW TO NORTH NORTHWEST FROM EAST SIDE OF WELLS AND SOUTH OF LAKE STREET. WELLS-LAKE TURN. - Union Elevated Railroad, Union Loop, Wells, Van Buren, Lake Streets & Wabash Avenue, Chicago, Cook County, IL

199

A new interpretation from geophysical data of the crustal architecture of the East Antarctic craton between Vostok Lake and Adventure Subglacial depression  

NASA Astrophysics Data System (ADS)

Numerical modelling of the Earth surface has been extensively used to investigate regional tectonic settings. The East Antarctic Craton (EAC) is a fragment of the Gondwanaland Precambrian shield as confirmed from the sea floor geophysical reconstruction. Despite the progress achieved in the last decades for the understanding of the tectonic evolution of the EAC, our knowledge of the subglacial geology derives from sparse rocks outcrop around the perimeter of the continent since the ice sheet prevents from direct investigations. Since the onset of the East Antactic Ice Sheet (EAIS), the tectonic activity represents the major modelling agent of the subglacial landscape, due to the mostly dry ice cap-bedrock contact preventing any significant erosional or sedimentary episode. Compressional, extensional, transcurrent tectonic styles of deformation produce characteristic morphological signatures. These landscapes were replicated by a series of numerical Hybrid Cellular Automata (HCA) models. The comparison and tuning of these models with the bedrock morphology allowed to constrain the extensional tectonic style responsible for the formation of the subglacial depressions in the huge region between Vostok and Adventure. Results from the numerical modelling suggest the tectonic origin of the Aurora depression, of the Concordia Trough and of the Adventure Subglacial basin. Crustal listric faults with normal displacements of the order of hundreds to thousands of meters created the necessary space beneath the ice cap to develop the present day subglacial morphologies as derived from RES data and their characteristic geophysical signatures. An original and alternative origin is proposed for the Lake Vostok depression based on the re-interpretation of published geophysical data. The integration of the results allows us to speculate on the existence of an intraplate transtensional deformation belt within the EAC since Cenozoic times.

Cianfarra, Paola; Salvini, Francesco

2013-04-01

200

GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage  

NASA Astrophysics Data System (ADS)

While GRACE (Gravity Recovery and Climate Experiment) satellites are increasingly being used to monitor water storage changes globally, the impact of spatial distribution of water storage within a basin is generally ignored but may be substantial. In many basins, water may be stored in reservoirs, lakes, flooded areas, small aquifer systems, and other localized regions with sizes typically below GRACE resolution. The objective of this study was to assess the impact of non-uniform water storage distribution on GRACE estimates as basin-wide averages, focusing on surface water reservoirs. Analysis included numerical experiments testing the effect of mass size and position within a basin, and application to the Lower Nile (Lake Nasser) and Tigri-Euphrates (TE) basins as examples. Numerical experiments show that by assuming uniform mass distribution, GRACE estimates may under- or over-estimate basin-average water storage by up to a factor of two, depending on reservoir location and extent. Although their spatial extent may be unresolved by GRACE, reservoir storage may dominate in some basins. For example, it accounts for 95% of seasonal variations in the Lower Nile and 10% in the TE basins. Because reservoirs are used to mitigate droughts and buffer against climate extremes, their influence on interannual time scales can be large, for example accounting for 50% of total water storage decline during the 2007-2009 drought in the TE basin. Effects on GRACE estimates are not easily accounted for via simple multiplicative scaling, but in many cases independent information may be available to improve estimates. Accurate estimation of the reservoir contribution is critical, especially when separating groundwater from GRACE total water storage changes. Because the influence of spatially concentrated water storage - and more generally water distribution - is significant, GRACE estimates will be improved when it is possible to combine independent spatial distribution information with GRACE observations, even when reservoir storage is not a major factor. In this regard, data from the upcoming Surface Water Ocean Topography (SWOT) satellite mission should be an especially important companion to GRACE-FO observations.

Longuevergne, L.; Wilson, C. R.; Scanlon, B. R.; Crétaux, J. F.

2012-10-01

201

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

202

Simulation of a semi-permanent wetland basin in the Cottonwood Lake area, east-central North Dakota  

USGS Publications Warehouse

A coupled surface/subsurface hydrologic model was developed to examine the effects of climatic conditions on stage fluctuations within a semi-permanent wetland located in the Prairie Pothole region of east-central North Dakota. Model calibration was accomplished using data collected from 1981 to 1996 to encompass extreme climatic conditions. Results show that the processes of precipitation largely control wetland stage. Surface runoff produces short duration, high magnitude flows typically associated with spring thaw. On the other hand, groundwater contribution provides flows smaller in magnitude but higher in duration and these become increasingly important with respect to wetland stage during extended periods of drought and flood. Peak groundwater fluxes lag one-to-two months behind peak recharge rates and therefore occur predominantly during the month of June. Groundwater fluxes then attenuate slowly for the remainder of the year to the point where water may move out of the wetland and into the underlying aquifer during the fall and winter months. Despite an over simplification of the complex groundwater component of the wetland system it was found that this modeling approach was able to predict system response over 15 years, under extreme climatic conditions and with relatively easily attainable data input.

Carroll, R. W. H.; Pohll, G. M.; Tracy, J. C.; Winter, T. C.

2001-01-01

203

51. Third Floor, Lake Forest, west center room, looking west, ...  

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

51. Third Floor, Lake Forest, west center room, looking west, part of original Forest Cottage as of 1901. - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

204

3. View northeast, west facade of Lake Forest (original Forest ...  

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

3. View northeast, west facade of Lake Forest (original Forest Cottage structure incorporated into renamed structure) - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

205

4. View southeast, west facade of Lake Forest (original Forest ...  

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

4. View southeast, west facade of Lake Forest (original Forest Cottage structure incorporated into renamed structure) - Lake Placid Club, Forest Wing, East side of Mirror Lake Drive, North of State Route 86 & Main, North Elba, Essex County, NY

206

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

207

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

208

Mono Lake's Radiocarbon Budget: An unsolved enigma  

Microsoft Academic Search

Mono Lake occupies a semiarid basin just east of the central Sierra Nevada in California. During the past 4 decades, diversion of the lake's tributary streams by the Los Angeles Department of Water and Power (LADWP) has caused the lake to shrink dramatically. This shrinkage has concentrated the salts that occur naturally in the lake, forcing the salinity to rise

Wallace Broecker; Scott Stine

1988-01-01

209

A multi-proxy study of lake-development in response to catchment changes during the Holocene at Lochnagar, north-east Scotland  

Microsoft Academic Search

This paper describes a multi-core lake sediment study using pollen, diatoms, and chironomids, together with magnetics and sediment biogeochemistry, as biotic and abiotic proxies to infer lake development in response to environmental change during the Holocene at Lochnagar in the eastern Highlands of Scotland. Diatoms are used to infer pH, chironomids to infer temperature, with pollen and plant megafossils acting

Catherine Dalton; H. J. B. Birks; Stephen J. Brooks; Nigel G. Cameron; Richard P. Evershed; Sylvia M. Peglar; Julie A. Scott; Roy Thompson

2005-01-01

210

The late holocene palaeoenvironment in the Lake Njupi area, west Cameroon: implications regarding the history of Lake Nyos  

Microsoft Academic Search

Lake Njupi, 1 km east of Lake Nyos, on the Cameroon Volcanic Line, was formed by the damming of a local crustal depression. Two cores from Lake Nyos were analysed which penetrated sediments at the margin of the lake. The older deposits give an age of 3400 years BP and this date is proposed as a minimum age for Lake

Appolinaire Zogning; Pierre Giresse; Jean Maley; François Gadel

1997-01-01

211

View of building 11050, showing two additions on east and ...  

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

View of building 11050, showing two additions on east and north side. Looking southwest. - Naval Ordnance Test Station Inyokern, China Lake Pilot Plant, Machine Shop, C Street, China Lake, Kern County, CA

212

View of building 11050, showing metal clad addition on east ...  

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

View of building 11050, showing metal clad addition on east elevation, looking southwest. - Naval Ordnance Test Station Inyokern, China Lake Pilot Plant, Machine Shop, C Street, China Lake, Kern County, CA

213

Oblique view of building 11050, showing east and south sides, ...  

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

Oblique view of building 11050, showing east and south sides, looking northwest. - Naval Ordnance Test Station Inyokern, China Lake Pilot Plant, Fire Station & Marine Barracks, D Street, at corner of 4th Street, China Lake, Kern County, CA

214

East-Asian monsoon variability between 15 000 and 2000 cal. yr BP recorded in varved sediments of Lake Sihailongwan (northeastern China, Long Gang volcanic field)  

Microsoft Academic Search

A palaeohydrological reconstruction on decadal scale for the period 15000-2000 cal. yr BP based on calculated net accumulation rates for biogenic silica (F-bSiO2) and additional proxies (sedimentological data, geochemical sediment characteristics and pollen) is derived from varved sediments of Lake Sihailongwan (SHL). In Lake SHL, F-bSiO2 is positively correlated with the inflow of nutrient-rich groundwater. Since groundwater inflow is mainly

Georg Schettler; Qiang Liu; Jens Mingram; Martina Stebich; Peter Dulski

2006-01-01

215

Predominance of Flavobacterium, Pseudomonas, and Polaromonas within the prokaryotic community of freshwater shallow lakes in the northern Victoria Land, East Antarctica.  

PubMed

A polyphasic approach that included PCR-dependent and PCR-independent molecular techniques was applied to analyze the prokaryotic community in surface waters of shallow Antarctic lakes. The in situ abundance of different bacterial groups was determined by the fluorescence in situ hybridization, whereas bacterial diversity was investigated by 16S rRNA gene sequencing of bacterial clones and isolates. The different approaches allowed the identification of the significant microbial components of the lake bacterioplanktonic communities, indicating a predominance of Flavobacterium, Pseudomonas, and Polaromonas (up to about 56% of total sequences). These genera also appear to be important in freshwater systems elsewhere in the world. Interestingly, closest blast matches to our sequences were predominantly from polar lakes and ponds, in addition to streams and glaciers, suggesting a bipolar distribution of freshwater lake bacterioplankton. Bacteria that are more traditionally associated with the marine environment were also detected, thus indicating an external input by atmospheric deposition and/or seabird excreta. Finally, a slightly different microbial community occurred in the lake at Inexpressible Island that was characterized by low N  :  P ratio and very high conductivity value, reinforcing the idea that physicochemical and trophic status may affect the structure and composition of the bacterioplankton assemblages in Antarctic lakes. PMID:22512730

Michaud, Luigi; Caruso, Consolazione; Mangano, Santina; Interdonato, Filippo; Bruni, Vivia; Lo Giudice, Angelina

2012-05-04

216

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

217

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

218

5. EAST SPAN, FROM SOUTH, SHOWING STRUCTURAL CONFIGURATION, INCLUDING POLYGONAL ...  

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

5. EAST SPAN, FROM SOUTH, SHOWING STRUCTURAL CONFIGURATION, INCLUDING POLYGONAL TOP CHORD, TRUSS PANELS, EAST ABUTMENT, AND CENTRAL PIER - Glendale Road Bridge, Spanning Deep Creek Lake on Glendale Road, McHenry, Garrett County, MD

219

A revised inventory of Antarctic subglacial lakes  

Microsoft Academic Search

The locations and details of 145 Antarctic subglacial lakes are presented. The inventory is based on a former catalogue of lake-type features, which has been subsequently reanalysed, and on the results from three additional datasets. The first is from Italian radio-echo sounding (RES) of the Dome C region of East Antarctica, from which 14 new lakes are identified. These data

MARTIN J. SIEGERT; SASHA CARTER; IGNAZIO TABACCO; SERGEY POPOV; DONALD D. BLANKENSHIP

2005-01-01

220

Phylogeny of a rapidly evolving clade: The cichlid fishes of Lake Malawi, East Africa (adaptive radiationysexual selectionyspeciationyamplified fragment length polymorphismylineage sorting)  

Microsoft Academic Search

Lake Malawi contains a f lock of >500 spe- cies of cichlid fish that have evolved from a common ancestor within the last million years. The rapid diversification of this group has been attributed to morphological adaptation and to sexual selection, but the relative timing and importance of these mechanisms is not known. A phylogeny of the group would help

R. C. ALBERTSON; J. A. M ARKERT; P. D. D ANLEY; T. D. KOCHER

221

Isolation of mercury resistant bacteria and influence of abiotic factors on bioavailability of mercury — A case study in Pulicat Lake North of Chennai, South East India  

Microsoft Academic Search

Pulicat Lake sediments are often severely polluted with mercury compounds and other toxic heavy metals. Several mercury-resistant bacteria were isolated and identified from the sediments and all the isolates exhibited broad spectrum resistance (both organic and inorganic mercuric compounds). Mercury volatilization showed that four of the isolated Bacillus cereus strains were able to reduce water soluble ionic form of mercury

S. Kamala Kannan; R. Krishnamoorthy

2006-01-01

222

Biogeochemical properties and diagenetic changes during the past 3.6 Ma recorded by FTIR spectroscopy in the sediment record of Lake El'gygytgyn, Far East Russian Arctic  

NASA Astrophysics Data System (ADS)

A number of studies have shown that Fourier transform infrared spectroscopy (FTIRS) can be applied to quantitatively assess lacustrine sediment constituents. In this study, we developed calibration models based on FTIRS for the quantitative determination of biogenic silica (BSi; n = 420; gradient: 0.9-56.5%), total organic carbon (TOC; n = 309; gradient: 0.02-2.89%), and total inorganic carbon (TIC; n = 153; gradient: 0.01-1.46%) in a 318 m long sediment record with a basal age of 3.6 Ma from Lake El'gygytgyn, Far East Russian Arctic. The developed partial least squares regression (PLSR) models yield high cross-validated (CV) R2CV = 0.85-0.91 and low root mean square error of cross-validation (RMSECV) (2.1-4.3% of the gradient for the different properties). The FTIRS-inferred concentrations of BSi, TOC, and TIC provide an initial insight into the climatic and environmental evolution at Lake El'gygytgyn throughout the late Pliocene and Quaternary showing a considerably high bioproductivity in the lake ecosystem between ~ 3.27-3.54 Ma during the early Pliocene warm period. Moreover, we found that the recorded FTIR spectra contain information on sample burial depth as a result of diagenetic changes (dehydration/dehydroxilation) of certain mineral phases. Despite the indicated post-depositional processes, the calibration models yield good statistical performances showing that general FTIRS models can be developed for several hundred meters long records extending several million years back in time. Our results highlight FTIRS to be a rapid, cost-effective alternative to conventional methods for quantification of biogeochemical properties.

Meyer-Jacob, C.; Vogel, H.; Melles, M.; Rosén, P.

2013-05-01

223

Evaluating the Impact of Gilgel Gibe Dam on the Lake Turkana Water Levels: An Illustration from an Endorheic Lake in Africa  

Microsoft Academic Search

Lake Turkana is one of the lakes in the Great Rift Valley, Africa. This lake has no outlet hence it is considered as closed or endorheic lake. To meet the demand of electricity in the east African region, Ethiopia is currently building Gilgel Gibe-III dam on the Omo River, which supplies up to 80% of the inflows to the Lake

N. Velpuri; G. B. Senay

2010-01-01

224

Population-structure and genetic diversity in a haplochromine fish cichlid of a satellite lake of Lake Victoria  

Microsoft Academic Search

The ? ? ? ? 500 species of the cichlid fish species flock of Lake Victoria, East Africa, have evolved in a record-setting 100 000 years and represent one of the largest adaptive radiations. We examined the population structure of the endangered cichlid species Xystichromis phytophagus from Lake Kanyaboli, a satellite lake to Lake Victoria in the Kenyan Yala wetlands.

ROMULUS ABILA; MARTA BARLUENGA; JOHANNES ENGELKEN; AXEL MEYER; WALTER SALZBURGER

2004-01-01

225

The evolution of saline lake waters: gradual and rapid biogeochemical pathways in the Basotu Lake District, Tanzania  

Microsoft Academic Search

The biogeochemical evolution of solutes markedly alters the chemistry in the closed-basin maar lakes that comprise the Basotu Lake District (Tanzania, East Africa). Examination of 11 (out of 13) lakes in the Basotu Lake District identified two distinct evolutionary pathways: a gradual path and a rapid path. During the course of biogeochemical evolution these waters follow either the gradual path

Peter Kilham; Paul L. Cloke

1990-01-01

226

The interaction of ground water with prairie pothole wetlands in the Cottonwood Lake area, east-central North Dakota, 1979–1990  

Microsoft Academic Search

The interaction of ground water with prairie wetlands in the Cottonwood Lake area has been the focus of research by the U.S.\\u000a Geological Survey and the U.S. Fish and Wildlife Service since 1977. During this time, climatic conditions at the site ranged\\u000a from near the driest to near the wettest of the century. Water levels in wetlands and in water-table

Thomas C. Winter; Donald O. Rosenberry

1995-01-01

227

Genetically distinct strains of Cassava brown streak virus in the Lake Victoria basin and the Indian Ocean coastal area of East Africa  

Microsoft Academic Search

Six isolates of Cassava brown streak virus (CBSV, genus Ipomovirus; Potyviridae) from the Lake Victoria basin in Uganda and Tanzania were characterized. Virus particles were 650 nm long. The complete coat\\u000a protein (CP)-encoding sequences (1,101 nucleotides, nt) were 90.7–99.5 and 93.7–99.5% identical at the nt and amino acid (aa)\\u000a levels, respectively. The 3? untranslated region was 225, 226 or 227 nt

D. R. Mbanzibwa; Y. P. Tian; A. K. Tugume; S. B. Mukasa; F. Tairo; S. Kyamanywa; A. Kullaya; Jari P. T. Valkonen

2009-01-01

228

The Reproductive Biology of Siscowet and Lean Lake Trout in Southern Lake Superior  

Microsoft Academic Search

Lean and siscowet morphotypes of lake trout Salvelinus namaycush in Lake Superior are thought to be genetically separate, but the reproductive isolating mechanism is unknown. The testicular and ovarian cycles and reproductive hormone levels of these morphotypes were determined from May to October in populations east and west of the Keweenaw Peninsula in southern Lake Superior. The gonadosomatic index (GSI)

Frederick Goetz; Shawn Sitar; Daniel Rosauer; Penny Swanson; Charles R. Bronte; Jon Dickey; Crystal Simchick

2011-01-01

229

Geomorphology, hydrology, and ecology of Lake Urema, central Mozambique, with focus on lake extent changes  

Microsoft Academic Search

Lake Urema is one of the most important ecological features of Gorongosa National Park, located in central Mozambique, in the East African Rift System. Understanding hydrology and ecology of the lake and its tributaries is particularly important for the conservation of the Park’s floodplain habitats and its biodiversity. There are concerns that hydrological boundary conditions and ecology of Lake Urema

Beate Böhme; Franziska Steinbruch; Richard Gloaguen; Hermann Heilmeier; Broder Merkel

2006-01-01

230

Stable isotope geochemistry of East African waters. [Abstract only  

SciTech Connect

Lakes and Rivers in East Africa have varied stable isotopic compositions. Lakes exhibit enriched delta13-C values (-2 to +5%), while their inflowing rivers show depleted values (-15 to -8%). Hot springs and standing pools of water have intermediate values. Some small lakes are extremely variable in delta18-0 or deltaD (+2 to +8% and +20 to +40%, respectively for Lake Naivasha), whereas larger lakes are relatively constant for long periods of time (+5.6 to 6.1 and +36 to 40, respectively for Lake Turkana). Isotopic values are unrelated to salinity for comparison between lakes. Stable isotopes also reveal the sources of hot spring discharges: the Kapedo hot springs probably originate from Maralel and not from Lake Baringo as local legend has it; the hot springs north of Lake Naivasha are of meteoric origin while those to the south of Lake Naivasha have similar isotopic compositions to Lake Naivasha.

Sayer, M.D.; Cerling, T.E.; Bowman, J.R.

1983-03-01

231

Water Hyacinth Eichhornia crassipes (Mart.) Solms-Laubach Dynamics and Succession in the Nyanza Gulf of Lake Victoria (East Africa): Implications for Water Quality and Biodiversity Conservation  

PubMed Central

This study, conducted in Nyanza Gulf of Lake Victoria, assessed ecological succession and dynamic status of water hyacinth. Results show that water hyacinth is the genesis of macrophyte succession. On establishment, water hyacinth mats are first invaded by native emergent macrophytes, Ipomoea aquatica Forsk., and Enydra fluctuans Lour., during early stages of succession. This is followed by hippo grass Vossia cuspidata (Roxb.) Griff. in mid- and late stages whose population peaks during climax stages of succession with concomitant decrease in water hyacinth biomass. Hippo grass depends on water hyacinth for buoyancy, anchorage, and nutrients. The study concludes that macrophyte succession alters aquatic biodiversity and that, since water hyacinth infestation and attendant succession are a symptom of broader watershed management and pollution problems, aquatic macrophyte control should include reduction of nutrient loads and implementing multifaceted approach that incorporates biological agents, mechanical/manual control with utilization of harvested weed for cottage industry by local communities.

Gichuki, John; Omondi, Reuben; Boera, Priscillar; Okorut, Tom; Matano, Ally Said; Jembe, Tsuma; Ofulla, Ayub

2012-01-01

232

Complete genome sequence of the halophilic bacterium Spirochaeta africana type strain (Z-7692T) from the alkaline Lake Magadi in the East African Rift  

PubMed Central

Spirochaeta africana Zhilina et al. 1996 is an anaerobic, aerotolerant, spiral-shaped bacterium that is motile via periplasmic flagella. The type strain of the species, Z-7692T, was isolated in 1993 or earlier from a bacterial bloom in the brine under the trona layer in a shallow lagoon of the alkaline equatorial Lake Magadi in Kenya. Here we describe the features of this organism, together with the complete genome sequence, and annotation. Considering the pending reclassification of S. caldaria to the genus Treponema, S. africana is only the second 'true' member of the genus Spirochaeta with a genome-sequenced type strain to be published. The 3,285,855 bp long genome of strain Z-7692T with its 2,817 protein-coding and 57 RNA genes is a part of the G enomic E ncyclopedia of B acteria and A rchaea project.

Liolos, Konstantinos; Abt, Birte; Scheuner, Carmen; Teshima, Hazuki; Held, Brittany; Lapidus, Alla; Nolan, Matt; Lucas, Susan; Deshpande, Shweta; Cheng, Jan-Fang; Tapia, Roxanne; Goodwin, Lynne A.; Pitluck, Sam; Pagani, Ioanna; Ivanova, Natalia; Mavromatis, Konstantinos; Mikhailova, Natalia; Huntemann, Marcel; Pati, Amrita; Chen, Amy; Palaniappan, Krishna; Land, Miriam; Rohde, Manfred; Tindall, Brian J.; Detter, John C.; Goker, Markus; Bristow, James; Eisen, Jonathan A.; Markowitz, Victor; Hugenholtz, Philip; Woyke, Tanja; Klenk, Hans-Peter; Kyrpides, Nikos C.

2013-01-01

233

Speciation via introgressive hybridization in East African cichlids?  

PubMed

Speciation caused by introgressive hybridization occurs frequently in plants but its importance remains controversial in animal evolution. Here we report a case of introgressive hybridization between two ancient and genetically distinct species of Lake Tanganyika cichlids that led to the formation of a new species. Neolamprologus marunguensis contains mtDNA haplotypes from both parental species varying on average by 12.4% in the first section of the control region and by 5.2% in a segment of the cytochrome b gene. All individuals have almost identical DNA sequences in the flanking regions of the single-copy nuclear DNA locus TmoM27, and show a mosaic of alleles derived from both parental lineages in six microsatellite loci. Hence, our finding displays another mode of speciation in cichlid fishes. The increase of genetic and phenotypic diversity due to hybridization may contribute to the uniquely rapid pace of speciation in cichlids. PMID:11918795

Salzburger, W; Baric, S; Sturmbauer, C

2002-03-01

234

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the North Canadian River from Oklahoma City to Eufaula Lake in east-central Oklahoma  

USGS Publications Warehouse

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries and maps of of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the North Canadian River from Oklahoma City to Eufaula Lake in east-central Oklahoma. Ground water in 710 square miles of Quaternary-age alluvial and terrace deposits along the North Canadian River is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer, composed of alluvial and terrace deposits, consists of sand, silt, clay, and gravel. The aquifer is underlain and in hydraulic connection with the upper zone of the Permian-age Garber-Wellington aquifer and the Pennsylvanian-age Ada-Vamoosa aquifer. Most of the lines in the four digital data sets were digitized from a published ground-water modeling report but portions of the aquifer boundary data set was extracted from published digital geologic data sets. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Adams, G. P.; Runkle, Donna; Rea, Alan; Becker, C. J.

1997-01-01

235

Geologic Control on the Setting of Antarctic Subglacial Lakes  

Microsoft Academic Search

Most Antarctic subglacial lakes are located in East Antarctica. The recently deglaciated Laurentian craton of North America provides an ideal analog. Consideration of the Laurentian analog leads to several lines of thought relevant to the interpretation of the tectonic environment of the East Antarctica lakes. First, the deep structural levels at which cratonic basement rocks are exposed, around the fringes

I. W. Dalziel

2006-01-01

236

Destruction of fisheries in Africa's lakes  

Microsoft Academic Search

The introduction of the Nile perch into Lake Victoria, East Africa, has had disastrous consequences. Fisheries have been not merely damaged but destroyed. Lake Malawi has the world's most species-rich fish fauna and the prospect of introduction of alien species could mean disaster.

C. D. N. Barel; R. Dorit; P. H. Greenwood; G. Fryer; N. Hughes; P. B. N. Jackson; H. Kawanabe; R. H. Lowe-McConnell; M. Nagoshi; A. J. Ribbink; E. Trewavas; F. Witte; K. Yamaoka

1985-01-01

237

Silica Depletion in Lake Victoria: Sedimentary Signals at Offshore Stations  

Microsoft Academic Search

Six short sediment cores from offshore stations in Lake Victoria (East Africa) were analyzed for evidence of recent change in the lake's pelagic ecosystem. Three stations were located on a NW-SE transect between 48 m water depth, near the present upper limit of seasonal hypolimnetic oxygen depletion, and the deepest point of Lake Victoria at 68 m. Four stations formed

Dirk Verschuren; David N. Edgington; Hedy J. Kling; Thomas C. Johnson

1998-01-01

238

Lake thresholds and the geomorphologic role of Göllü Polje (Eastern Anatolia, Turkey) during very high magnitude levels of Lake Van  

Microsoft Academic Search

Soda Lake Van is a very important reference site for Late Glacial and Holocene palaeoenvironmental records in the Caucasus, Near and Middle East. Influenced by past climatic regimes, changes in the hydrology of Lake Van being very sensitive to humidity and temperature changes, past climates and environments have been studied from deep lake sediments (Landman et al., 1996, Degens &.Kurtmann,

Ebru Akkopru; Catherine Kuzucuoglu; Ali Fuat Dogu; Damase Mouralis; Aurelien Christol; Daniel Brunstein; Halil Zorer

2010-01-01

239

Spatio-temporal variation of CO2 emission from Chilika Lake, a tropical coastal lagoon, on the east coast of India  

NASA Astrophysics Data System (ADS)

Biogeochemical Carbon cycling was studied in Asia's largest brackish lagoon, Chilika on the east coast of India. Systematic time-series observations were made at 35 hydrologically different stations over the entire lagoon. The first of these kinds of measurements reveal, inter and intra annual variability of partial pressure of CO2 (pCO2). A comparative analysis of pCO2, CO2 flux over four years (2005, 2009, 2010 and 2011) showed that the northern part of the lagoon maintained the highest levels of pCO2, with maximum CO2 efflux to the atmosphere associated with peak monsoon period. The high pCO2 corresponded to a significant decrease in pH (˜0.8) from the low to high flow periods. Higher bacterial abundance (1.55 ± 0.28 × 109 cells L-1) and bacterial respiration (185.31 ± 105.37 ?g C L-1 d-1), suggested high levels of organic carbon decomposition during the high flow period. In contrast, the southern sector was least affected by river discharge, with low pCO2 values and CO2 flux as in the dry period. The central part and outer channel of the lagoon had intermediate characteristics. During high flow, the air-water CO2 flux from the entire lagoon was estimated to be 31.2 mol C m-2 y-1, which was comparatively very high with respect to the mean CO2 emission from the entire subtropical and tropical estuaries. Highest CO2 flux (65.98 mol C m-2 y-1) was observed in the northern sector, followed by the outer channel (17.61 mol C m-2 y-1), central sector (15.69 mol C m-2 y-1) and southern sector (14.44 mol C m-2 y-1). The northern part of Chilika lagoon being an important river-influenced region was responsible for the biological transformation of organic carbon to inorganic carbon and emitting CO2 to the atmosphere. Such a sectoral approach would reveal zonal influences of CO2 within a water body along with conditions leading to sink or a source.

Muduli, Pradipta R.; Kanuri, Vishnu Vardhan; Robin, R. S.; Charan Kumar, B.; Patra, Sivaji; Raman, A. V.; Nageswarara Rao, G.; Subramanian, B. R.

2012-11-01

240

Multi-stage hydrothermal processes involved in "low-sulfide" Cu(-Ni)-PGE mineralization in the footwall of the Sudbury Igneous Complex (Canada): Amy Lake PGE zone, East Range  

NASA Astrophysics Data System (ADS)

The Amy Lake PGE zone is a "low-sulfide-type" Cu-(Ni-)PGE mineralization in the East Range footwall of the 1.85 Ga Sudbury Igneous Complex occurring in a 100-m-wide Sudbury Breccia belt that coincides with an impact-related major fracture zone (Bay Fault zone). Detailed hydrothermal alteration mapping, fluid inclusion, trace element, and stable isotope studies revealed a complex alteration and mineralization history in a multi-source, multi-stage Sudbury-related hydrothermal system. The two major stages of syn-Sudbury hydrothermal activity are characterized by similarly high-salinity, high-temperature fluids that are (1) locally derived from footwall granophyre bodies, and typified with high Ni/Cu and PGE/S ratios and high REE contents (magmatic-hydrothermal stage), and (2) a more voluminous Cu-Ni-PGE-rich fluid flux probably originated from the Sudbury Igneous Complex/footwall contact (hydrothermal stage). The second hydrothermal flux was introduced by brittle fractures in the area and resulted in a complex zonation of alteration assemblages and mineralization governed by local footwall composition. The Sudbury-related hydrothermal event was overprinted by shear-related epidote veining and calcite-chlorite replacement, both regionally present in the Sudbury structure. Based on analogies, the most important factors involved in the formation of hydrothermal low-sulfide mineralization are proposed to be (1) accumulation of PGE-enriched fluids, (2) large-scale brittle structures as conduits to these fluids, and (3) adequate host rock composition as a chemical trap resulting in sulfide and PGM precipitation. In environments meeting these criteria, hydrothermal PGE mineralization is known to have formed not only in the Sudbury footwall but also from mafic-ultramafic intrusions associated with primary magmatic PGE from several locations around the world.

Tuba, Györgyi; Molnár, Ferenc; Ames, Doreen E.; Péntek, Attila; Watkinson, David H.; Jones, Peter C.

2013-05-01

241

East Timor  

NSDL National Science Digital Library

This Week's In the News examines the escalation of violence and the proposal for autonomy in the Indonesian province of East Timor. Last weekend, anti-independence militiamen killed dozens of separatist activists in Dili, the East Timorese capital, intensifying the fierce bloodshed and political tumult in the province. The recent massacre is just one of several brutal episodes that have plagued East Timor in the past quarter-century. The people of the embattled island have suffered numerous human rights violations, have endured economic collapse, and have been decimated by guerrilla warfare, famine, and disease. Over 200,000 East Timorese -- or nearly one-fourth of the population -- have died in the troubles, which began in 1975 when Portugal abruptly abandoned East Timor after 400 years of colonial rule. Unstable and vulnerable, the newly independent East Timor was quickly invaded, occupied, and annexed in 1976 by Indonesia, a stronger nation that quashed all subsequent separatist movements. Last January, after years of political oppression, Indonesia's parliament finally succumbed to international pressure and announced that it would grant East Timor either full independence or autonomy within the Indonesian state. The United Nations, although it has never officially recognized Indonesia's sovereignty over East Timor, plans to supervise a vote, tentatively scheduled for July, wherein the East Timorese will determine whether they want full independence or provincial autonomy. Later this week, Foreign Ministers Ali Alatas of Indonesia and Jaime Gama of Portugal are meeting in New York with UN Secretary-General Kofi Annan to discuss the East Timorese autonomy option and plan for the pending UN-monitored poll. However, the recent resurgence of violence between anti- and pro-independence factions in and around Dili threatens the viability of the proposed poll and endangers the stability of East Timor's self-determination. The nine resources discussed offer background information, the latest news, political analysis, and social commentary.

Osmond, Andrew.

1999-01-01

242

Lacustrine strata sedimentology and lake-level history in ancient Zhuyeze Lake since the Last Deglaciation  

Microsoft Academic Search

The ancient Zhuyeze Lake lies in the east Hexi corridor of Northwest China and it is the interacting belt of the East Asian\\u000a summer monsoon and the westerly line. The research on paleoclimate of the lake facilitates the understanding of the processes\\u000a and mechanism of climate change in Northwest China since the Last Deglaciation. Related researches of this area started

Qiang Zhao; Nai’ang Wang; Xiumei Li

2008-01-01

243

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

244

14. LOOKING WEST INTO THE EAST PURSUIT PLANE BAY OF ...  

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

14. LOOKING WEST INTO THE EAST PURSUIT PLANE BAY OF AR-9. LOW WALLED CREW SHELTER AT RIGHT. - Edwards Air Force Base, South Base, Rammed Earth Aircraft Dispersal Revetments, Western Shore of Rogers Dry Lake, Boron, Kern County, CA

245

Interior view to the east of an empty computer room ...  

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

Interior view to the east of an empty computer room - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Six Transmitter Building, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

246

View of the highway, from just east of its crossing ...  

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

View of the highway, from just east of its crossing of the Beartooth Lake, looking northeast, showing retained alignment - Beartooth Highway, Red Lodge, Montana to Cooke City, Montana, Cody, Park County, WY

247

6. Photocopy of photograph, circa 1906 VIEW WESTSOUTHWEST SHOWING EAST ...  

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

6. Photocopy of photograph, circa 1906 VIEW WEST-SOUTHWEST SHOWING EAST ELEVATION AND SURROUNDING ENVIRONMENT (enlargement of 4' x 5' negative) - Gary Land Company Building, Gateway Park, Fourth Avenue & Penn Street (moved from Broadway), Gary, Lake County, IN

248

7. View east of southeast corner of filtration bed building. ...  

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

7. View east of southeast corner of filtration bed building. Laboratory building is at center left of photograph. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

249

11. View of east entry to central corridor of filtration ...  

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

11. View of east entry to central corridor of filtration bed building. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

250

8. DETAIL VIEW OF INCLINED OUTLET GATE WHEEL, LOOKING EAST ...  

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

8. DETAIL VIEW OF INCLINED OUTLET GATE WHEEL, LOOKING EAST - High Mountain Dams in Upalco Unit, Kidney Lake Dam, Ashley National Forest, 4.7 miles North of Miners Gulch Campground, Mountain Home, Duchesne County, UT

251

3. OVERALL VIEW OF DAM, SHOWING UPSTREAM FACE, LOOKING EAST ...  

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

3. OVERALL VIEW OF DAM, SHOWING UPSTREAM FACE, LOOKING EAST - High Mountain Dams in Upalco Unit, Kidney Lake Dam, Ashley National Forest, 4.7 miles North of Miners Gulch Campground, Mountain Home, Duchesne County, UT

252

VIEW FACING EAST. ORE TRESTLE WINDS AROUND THE INGOT MOLD ...  

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

VIEW FACING EAST. ORE TRESTLE WINDS AROUND THE INGOT MOLD CONDITIONING BUILDING IN FOREGROUND. PITTSBURGH & LAKE ERIE TRACKS WIND THROUGH TOWN TOWARDS PITTSBURGH AT RIGHT. - Pittsburgh Steel Company, Monessen Works, Donner Avenue, Monessen, Westmoreland County, PA

253

4. View north of Lake Whitney Dam. Wood shed at ...  

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

4. View north of Lake Whitney Dam. Wood shed at center of photograph houses a turbine installed in 1932. Brick structure to the left of the turbine shed is a gate house which houses the main valves controlling flow of lake to water to the filter plant. - Lake Whitney Water Filtration Plant, Lake Whitney Dam, East side of Whitney Avenue near intersection with Armory Street, Hamden, New Haven County, CT

254

Sulfate distribution in a multi-basin, saline lake  

Microsoft Academic Search

Devils Lake in northeastern North Dakota (USA) is a terminal lake of glacial origin with a substantial sulfate content. Since 1940, the lake water level has risen over 13.5m and salinity has decreased. Devils Lake consists of a series of interconnected basins with sulfate concentration increasing in an eastward direction from 450mg\\/l in West Bay to 3000mg\\/l in East Devils

Joe D. Manous; Heinz G. Stefan

2004-01-01

255

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

256

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...

257

Far East  

SciTech Connect

Petroleum activity throughout the Far East region was on the upswing during 1980. In spite of increased interest in many parts of the Far East, no major new discoveries were reported. From India to Indonesia, old fields are being rehabilitated and previously uneconomic areas are being looked at again. Indonesia set a new record in 1980 for the number of exploratory wells drilled. Peninsular Malaysia set a record for oil production. Overall, however, 1980 was a banner year for petroleum exploration in the Far East. Sri Lanka saw its first foreign contractor interest in several years. India made major moves toward increasing exploration by offering offshore and onshore blocks to foreign contractors . Bangladesh and even Burma signed exploitation contracts with Japanese investors in order to increase production. Malaysia offered new acreage blocks for the first time in several years. Indonesia and the Philippines also actively encouraged exploration by offering new contract areas. One country in the Far East that did not participate in the 1980 oil boom was China. Taiwan also carried on, as in previous years with the Chinese Petroleum Corporation as the only operator. Japanese and South Korean activities were at approximately the same level as in previous years, although drilling did start in the joint development zone. Total production of the Far East reporting region declined slightly. One significant aspect of 1980 petroleum activities throughout the Far East region is the growing acceptance by various Far East countries of Asian investment for developing and exploring for hydrocarbons. Japan is the major investor, but South Korean interests and the Chinese Petroleum Corporation also began to invest in petroleum rights in other Asian countries. The main area for investment continued to be Indonesia. 39 figures, 9 tables.

Fletcher, G.L.

1981-10-01

258

Hydrology of Central Florida Lakes - A Primer  

USGS Publications Warehouse

INTRODUCTION Lakes are among the most valued natural resources of central Florida. The landscape of central Florida is riddled with lakeswhen viewed from the air, it almost seems there is more water than land. Florida has more naturally formed lakes than other southeastern States, where many lakes are created by building dams across streams. The abundance of lakes on the Florida peninsula is a result of the geology and geologic history of the State. An estimated 7,800 lakes in Florida are greater than 1 acre in surface area. Of these, 35 percent are located in just four counties (fig. 1): Lake, Orange, Osceola, and Polk (Hughes, 1974b). Lakes add to the aesthetic and commercial value of the area and are used by many residents and visitors for fishing, boating, swimming, and other types of outdoor recreation. Lakes also are used for other purposes such as irrigation, flood control, water supply, and navigation. Residents and visitors commonly ask questions such as Whyare there so many lakes here?, Why is my lake drying up (or flooding)?, or Is my lake spring-fed? These questions indicate that the basic hydrology of lakes and the interaction of lakes with ground water and surface water are not well understood by the general population. Because of the importance of lakes to residents of central Florida and the many questions and misconceptions about lakes, this primer was prepared by the U.S. Geological Survey (USGS) in cooperation with the St. Johns River Water Management District and the South Florida Water Management District. The USGS has been collecting hydrologic data in central Florida since the 1920s, obtaining valuable information that has been used to better understand the hydrology of the water resources of central Florida, including lakes. In addition to data collection, as of 1994, the USGS had published 66 reports and maps on central Florida lakes (Garcia and Hoy, 1995). The main purpose of this primer is to describe the hydrology of lakes in central Florida, the interactions between lakes and ground- and surface-waters, and to describe how these interactions affect lake water levels. Included are descriptions of the basic geology and geomorphology of central Florida, origins of central Florida lakes, factors that affect lake water levels, lake water quality, and common methods of improving water quality. The geographic area discussed in this primer is approximate (fig. 1) and includes west and east-central Florida, extending from the Gulf of Mexico to the Atlantic Ocean coastlines, northward into Marion, Putnam, and Flagler Counties, and southward to Lake Okeechobee. The information presented here was obtained from the many publications available on lakes in central Florida, as well as from publications on Florida geology, hydrology, and primers on ground water, surface water, and water quality. Many publications are available that provide more detailed information on lake water quality, and this primer is not intended as an extensive treatise on that subject. The reader is referred to the reference section of this primer for sources of more detailed information on lake water quality. Lakes discussed in this report are identified in figure 2. Technical terms used in the report are shown in bold italics and are defined in the glossary. The classification of some water bodies as lakes is highly subjective. What one individual considers a lake another might consider a pond. Generally, any water- filled depression or group of depressions in the land surface could be considered a lake. Lakes differ from swamps or wetlands in the type and amount of vegetation, water depth, and some water-quality characteristics. Lakes typically have emergent vegetation along the shoreline with a large expanse of open water in the center. Swamps or wetlands, on the other hand, are characterized by a water surface interrupted by the emergence of many varieties of plant life, from saw grasses to cypress trees. Lakes may be na

Schiffer, Donna M.

1998-01-01

259

View of the highway, approach to the Frozen Lake switchback ...  

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

View of the highway, approach to the Frozen Lake switchback curve, looking east. Proposed realignment will shift the road slightly to the south (right) - Beartooth Highway, Red Lodge, Montana to Cooke City, Montana, Cody, Park County, WY

260

32. Otter Lake Dam. View from downstream show how the ...  

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

32. Otter Lake Dam. View from downstream show how the dam blends into its environment. Looking east-northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

261

24. Mormon Flat reservoir, or Canyon Lake. Photographer Mark Durben, ...  

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

24. Mormon Flat reservoir, or Canyon Lake. Photographer Mark Durben, 1988. Source: Salt River Project. - Mormon Flat Dam, On Salt River, Eastern Maricopa County, east of Phoenix, Phoenix, Maricopa County, AZ

262

A LINE POLE 1 IN FOREGROUND AND MYSTIC LAKE POWERHOUSE ...  

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

A LINE POLE 1 IN FOREGROUND AND MYSTIC LAKE POWERHOUSE IN BACKGROUND. A LINE POLE 1 IS A MODERN REPLACEMENT STRUCTURE WITH BROWN PORCELAIN SUSPENSION-TYPE INSULATORS. VIEW TO EAST. - Mystic Lake Hydroelectric Facility, Electric Transmission A Line, Along West Rosebud Creek, Fishtail, Stillwater County, MT

263

Establishment, Spread and Impact of Neochetina spp. on Water Hyacinth in Lake Victoria, Kenya  

Microsoft Academic Search

The Kenya Agricultural Research Institute imported 12,300 curculionid weevils (Neochetina spp.) from diverse sources, for biological control of water hyacinth in Lake Victoria, as part of the World Bank-funded Lake Victoria Environmental Management Project in East Africa. In addition to the rearing and quarantine facility at Muguga, a second rearing facility was established in 1996 at Kibos, near Lake Victoria.

G. S. Ochiel; S. W. Njoka; A. M. Mailu; W. Gitonga

264

Weak mixing in Lake Kivu: New insights indicate increasing risk of uncontrolled gas eruption  

Microsoft Academic Search

The deep waters of the East African Rift Lake Kivu contain large amounts of dissolved carbon dioxide and methane. The release of a fraction of these gases, which could be triggered by a magma eruption within the lake, would have catastrophic consequences for the two million people living on its shore. Up to now the safety assessment of the lake

Martin Schmid; Michel Halbwachs; Bernhard Wehrli; Alfred Wüest

2005-01-01

265

Middle East  

SciTech Connect

Petroleum production in Middle East countries during 1980 totaled 6,747,719,000 bbl or an average rate of 18,436,390,000 bbl/d, down 13.9% from 1979. Increases were in Saudi Arabia and Syria. Significant decreases occurred in Iraq, Iran, Kuwait, and Turkey. New discoveries were made in Abu Dhabi, Iran, Saudi Arabia, Sharjah, and Oman. New areas were explored in Bahrain, Oman, Syria, and Yemen. 9 figures, 16 tables.

Hemer, D.O. (Mobil Oil Corp., New York, NY); Mason, J.F.; Hatch, G.C.

1981-10-01

266

Lake Taihu eddy flux mesonet for atmospheric and hydrological research  

NASA Astrophysics Data System (ADS)

Lakes play a unique role in global and regional carbon and water cycles. Information on the lake-air exchanges of energy, water vapor and CO2 are important to numerical weather models and climate change study. So far lake parameterizations of lakes in numerical weather models have been ocean studies and there have been few studies on lake-air fluxes of greenhouse gases. As a robust flux measurement method, eddy covariance is widely employed in studies on terrestrial ecosystems. However, long-term eddy covariance applications are still rare for lake systems. In this paper, we describe an eddy flux mesonet over Lake Taihu. The lake is large (with area of 2400 km2) and shallow (with depth of 2m) and is situated in the Yangtze River Delta, East China. Five eddy covariance systems were installed on platforms located in the north, east, south, west and middle of the lake, representing different biological attributes and wind-wave patterns. An additional eddy covariance site was established on land. Supporting measurements include general meteorological variables, net radiation components and water temperature profile. To our best knowledge, this is the first lake eddy flux mesonet. The data obtained with the mesonet provide powerful constraints for the studies on the temporal and spatial patterns of radiation, energy and water balances, CO2 exchange, and ecological characteristics of the lake and provide us opportunity to investigate the linkage between atmospheric and aquatic processes.

Liu, Shoudong; Xiao, Wei; Cao, Chang; Deng, Lichen; Hu, Cheng; Hu, Ning; Li, Hanchao; Liu, Cheng; Shen, Jing; Sun, Shiqiang; Wang, Wei; Xiao, Qitao; Xu, Jiaping; Yang, Dong; Zhang, Mi; Lee, Xuhui

2013-04-01

267

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...

268

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

269

Nutrient and phytoplankton responses to a flood event in a series of interconnected coastal lakes: Myall Lakes Australia  

Microsoft Academic Search

Myall Lakes is a large brackish coastal lake on the east coast of Australia that was considered pristine until the occurrence\\u000a of blue-green algal blooms in 1999. The temporal and spatial extent of chemical and biological changes to the water column\\u000a of Myall Lakes was studied intensively after a rain event in 2002. Water quality profiles (T, EC, pH, DO),

Joanne Wilson

2008-01-01

270

Taihu Lake, lower Yangtze drainage basin: evolution, sedimentation rate and the sea level  

NASA Astrophysics Data System (ADS)

The present study focuses on two Holocene sediment boreholes in Taihu Lake, sunk to examine the lake sediment including sedimentary texture and structure, microfossils, magnetic susceptibility and radiocarbon-dated Holocene stratigraphy. Results demonstrate that the early Taihu Lake area consisted primarily of West Taihu Lake depression and a low floodplain in the East Taihu Lake area. No hydraulic connection existed between the two sectors during the early Holocene when sea level stood at lower level. Core sediments, microfossil and magnetic evidence records that West Taihu Lake began to be inundated by brackish water prior to 6000 years ago, while East Taihu Lake still remained a freshwater setting. After 6000 B.P., a further rise in freshwater table in response to sea-level fluctuation progressively drowned the entire lake, coalescing the two parts after 4600-3500 B.P. Our coring revealed that the lacustrine sediment began to form in West Taihu Lake as early as 11,000 years ago, while it happened much later (only after 5700 B.P.) to form in East Taihu Lake. High sedimentation rates (0.42-0.35 mm/year) in lacustrine deposits of West Taihu Lake occurred between ~11,000 and 5000 B.P. In contrast, the high sedimentation rates (1.54 mm/year) in East Taihu Lake occurred only within a very short time period, from ~6500 to 5500 B.P. Since then, sedimentation rates have decelerated to a very low value (<0.10 mm/year) in both West and East Taihu Lakes. The low sedimentation rate of West and East Taihu Lake of the middle and late Holocene explains the deceleration of the sea-level rising after 5500 B.P. and the rapid coastal progradation seaward.

Wang, Jian; Chen, Xia; Zhu, Xiao-hua; Liu, Jin-ling; Chang, William Y. B.

2001-11-01

271

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

272

Mono Lake's Radiocarbon Budget: An unsolved enigma  

NASA Astrophysics Data System (ADS)

Mono Lake occupies a semiarid basin just east of the central Sierra Nevada in California. During the past 4 decades, diversion of the lake's tributary streams by the Los Angeles Department of Water and Power (LADWP) has caused the lake to shrink dramatically. This shrinkage has concentrated the salts that occur naturally in the lake, forcing the salinity to rise toward levels that will cause the extinction of the resident brine shrimp and brine flies that provide food for many hundreds of thousands of migratory waterfowl. The lake is now the focus of a pitched battle between conservationists who want to curtail diversions before serious ecological consequences occur and the LADWP, whose responsibility is to supply the city with water.

Broecker, Wallace; Stine, Scott

273

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

274

Field-mapping and petrographic analysis of volcanoes surrounding the Lake Natron Homo sapiens footprint site, northern Tanzania  

NASA Astrophysics Data System (ADS)

The Lake Natron Homo sapiens footprint site is located in northern Tanzania along the East African Rift escarpment. The site is positioned south of Lake Natron within an ephemeral channel of the Engare Sero River. The hominid footprints are preserved in a tuff, which originated from one of the volcanic centers surrounding the site. Two large volcanoes in the surrounding region, including the active carbonatite producing Oldoinyo L’engai and the now extinct Kerimasi are possible sources. This area also contains over 30 smaller tuff cones and tuff rings that have been poorly mapped and not analyzed in detail. The site is significant as it is the oldest modern human trackway in East Africa and one of the largest collections of hominid footprints in the world. Determining the source of the footprinted volcanic ash requires detailed field mapping, and both petrographic and geochemical analyses. Extensive field-mapping of the region revealed multiple regional beds that stratigraphically overlay the footprinted layer. Age dating as well as geochemical analysis is being conducted to relate these beds to the footprinted layer. Field-mapping showed that the footprinted tuff is over 35 cm thick, suggesting a large, sustained eruption. The bulk of the tuff cones examined in the field visibly varied in composition to the footprinted tuff and, based on proximity to the footprint site, are too small to produce the requisite volume of ash. Field analysis of samples collected from Oldoinyo L’engai reveal the most similar mineral assemblages to the footprinted layer, and the large volcano provides a source substantial enough to create a thick ash bed 10 km north of the summit. Preliminary research reveals that the footprinted tuff is a phonolite, characterized by silica depletion and the presence of sanidine, augite, and annite with interstitial calcite. XRD analysis of samples collected from Oldoinyo L’engai reveal a nepheline-rich phonolite with zeolites (ie. phillipsite) and calcite, both of which are likely secondary. Work by Dawson (1993)1 suggests that Oldoinyo L’engai had a phonolitic composition, which has evolved into a carbonatite. Samples collected from the two major volcanoes, including both modern and ancient samples, as well as numerous tuff cones will be analyzed with X-ray diffraction (XRD), scanning-electron microscopy (SEM), and both cathodoluminescence (CL) and transmitted light petrography, and then compared to the footprinted tuff. The goals of the geochemical and petrographic analyses are to determine similarities in bulk mineral composition between the target ash and the surrounding volcanics, find the source of the target ash, and confirm that Oldoinyo L’engai produced the footprinted tuff. 1Dawson, J.B., 1993. The Geology of Oldoinyo Lengai: Tanganyika Geological Survey, p. 350-387.

Hewitt, S. M.; Zimmer, B.; Liutkus, C.; Carmichael, S. K.; McGinnis, K.

2010-12-01

275

Changes in the dreissenid community in the lower Great Lakes with emphasis on southern Lake Ontario  

USGS Publications Warehouse

A field study was conducted in the lower Great Lakes to assess changes in spatial distribution and population structure of dreissenid mussel populations. More specifically, the westward range expansion of quagga mussel into western Lake Erie and toward Lake Huron was investigated and the shell size, density, and biomass of zebra and quagga mussel with depth in southern Lake Ontario in 1992 and 1995 were compared. In Lake Erie, quagga mussel dominated the dreissenid community in the eastern basin and zebra mussel dominated in the western basin. In southern Lake Ontario, an east to west gradient was observed with the quagga mussel dominant at western sites and zebra mussel dominant at eastern locations. Mean shell size of quagga mussel was generally larger than that of zebra mussel except in western Lake Erie and one site in eastern Lake Erie. Although mean shell size and our index of numbers and biomass of both dreissenid species increased sharply in southern Lake Ontario between 1992 and 1995, the increase in density and biomass was much greater for quagga mussels over the 3-year period. In 1995, zebra mussels were most abundant at 15 to 25 m whereas the highest numbers and biomass of quagga mussel were at 35 to 45 m. The quagga mussel is now the most abundant dreissenid in areas of southern Lake Ontario where the zebra mussel was once the most abundant dreissenid; this trend parallels that observed for dreissenid populations in the Dneiper River basin in the Ukraine.

Mills, Edward L.; Chrisman, Jana R.; Baldwin, Brad; Owens, Randall W.; O'Gorman, Robert; Howell, Todd; Roseman, Edward F.; Raths, Melinda K.

1999-01-01

276

Unraveling the climatic causes of past lake level change using lake energy and water balance models  

NASA Astrophysics Data System (ADS)

Lake level records provide a rich resource of information about past variations in surface water, a resource likely to experience significant impacts under future climate change. The water balance of a lake is controlled by a variety of climate variables, including precipitation, radiation, humidity, and wind speed, and it can be difficult to pinpoint the exact climatic causes of past lake level fluctuations. This understanding is crucial, however, for predicting whether surface water resources will diminish in the future. In this research, we use output from a coupled atmosphere-ocean general circulation model to force lake energy and water balance models over East Asia and Arid Central Asia to test hypotheses about the causes of lake level variations during the Holocene and Last Glacial Maximum. We find that changes in evaporation tend to work in concert with precipitation changes to maximize lake level fluctuations. This occurs because high levels of precipitation are associated with increased cloudiness and humidity and decreased shortwave radiation, which all lead to decreased lake evaporation. There is also a significant effect of changes in winter insolation on the annual duration of lake ice cover and lake evaporation. These findings help to explain some of the differences in lake level observed between monsoonal Asia and Arid Central Asia and can be generalized to other parts of the globe.

Morrill, C.; Li, Y.

2009-12-01

277

Geomorphology, hydrology, and ecology of Lake Urema, central Mozambique, with focus on lake extent changes  

NASA Astrophysics Data System (ADS)

Lake Urema is one of the most important ecological features of Gorongosa National Park, located in central Mozambique, in the East African Rift System. Understanding hydrology and ecology of the lake and its tributaries is particularly important for the conservation of the Park’s floodplain habitats and its biodiversity. There are concerns that hydrological boundary conditions and ecology of Lake Urema have changed in recent years. Possible causes for this change include climatic and land use changes as well as tectonic and geomorphological processes. In this study, a multi-temporal and multi-disciplinary approach was applied to investigate the dynamics and control mechanisms of Lake Urema. Principal methods comprised remote sensing analyses of time series of Landsat and ASTER data, geomorphological interpretations of a Digital Terrain Model (DTM) as well as field investigations such as analyses of water quality and sediment composition. The waters of Lake Urema have a low mineralization and pH values approximately neutral. The spatially dominant sediment type has a pure clay texture consisting of kaolinite and smectite. The sandy type consists of quartz, kali felspar, and plagioclase. The results of the supervised classifications for the satellite images from 1979 to 2000 showed that the lake’s extent ranged between 17 km2 (09/1995) and 25 km2 (08/1979). Above average rainfall was responsible for the extreme lake size in May 1997 (104 km2). The interpretations of the Digital Terrain Model demonstrated that alluvial fans limit the Urema basin from all sides and make Lake Urema a form of “reservoir lake”. The control mechanisms of the hydrological regime of Lake Urema, such as the contribution of groundwater, are not yet fully understood. The lake’s condition during the rainy season was not investigated. In the future, investigations of the sources and amounts of sediment input into the lake should be conducted.

Böhme, Beate; Steinbruch, Franziska; Gloaguen, Richard; Heilmeier, Hermann; Merkel, Broder

278

Lake-level change and fan delta evolution of glacial lakes in North Patagonia  

NASA Astrophysics Data System (ADS)

Large, cross-border glacial lakes, Lago General Carrea/Lago Buenos Aires (LGC/LBA) and Lago Cochrane/Lago Pueyrredon (LC/LP) occur on the east side of the northern Patagonian Icefield (NPI). Rivers emptying into the lakes have formed several fan deltas at their mouths in response to lake level changes. We examined the deltas around the both lakes based on field survey, aerial photograph interpretation, and analysis of digital elevation model (DEM). Two stepped fan deltas, named as fan deltas 1 and 2, except for the present one were observed widely at LGC/LBA. The features of fan delta deposits are similar to those of a Gilbert-type fan delta. The edges of these deltas were situated above 200 m and 100 m higher than the present lake level at a height of ca. 200 meters, suggesting that lake level fall with a magnitude of ~100 m occurred at least twice. The rate of each lake-level lowering would be very rapid, because the deltas have steep escarpments at the front and fluvial terraces cutting into the deltas are unclear along the rivers. The timings of emergence might be before 8.4 ka and soon after 6.2 ka based on the radiocarbon dates of the fan delta 1 and the existing numerical ages about the related landforms such as moraines and lacustrine deposits. Although there are also several, raised fan deltas at LC/LP, the altitudes of the deltas differ from those of LGC/LBA. Therefore both lakes were not merged even during the period of higher lake level after the Last Glacial Maximum. It is considered that outlet glaciers flowing toward the east from the NPI blocked the western end of the both lakes and separated them. Further study is required to clarify the relationship between behaviors of the glaciers and lake level fluctuations.

Aoki, T.; Hori, K.

2009-12-01

279

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

280

83. FIRST AND SECOND AQUEDUCTS LOOKING EAST/NORTHEAST Los Angeles ...  

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

83. FIRST AND SECOND AQUEDUCTS LOOKING EAST/NORTHEAST - Los Angeles Aqueduct, From Lee Vining Intake (Mammoth Lakes) to Van Norman Reservoir Complex (San Fernando Valley), Los Angeles, Los Angeles County, CA

281

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

282

Sub-fossil Chironomidae from East Africa. 2. Chironominae (Chironomini and Tanytarsini)  

Microsoft Academic Search

This paper and a companion article present illustrated guides to the identification of sub-fossil chironomid larvae (Insecta: Diptera: Chironomidae) preserved in the sediments of low- and mid-elevation lakes in East Africa. They are based on analysis of surface-sediment death assemblages from 61 lakes located in the humid to semi-arid environments in equatorial East Africa (Uganda, Kenya, Tanzania), supplemented with similar

Hilde Eggermont; Dirk Verschuren

2004-01-01

283

The sensitivity of a Tanzanian crater lake to catastrophic tephra input and four millennia of climate change  

Microsoft Academic Search

Diatom genera in many large East African lakes change little throughout the Holocene period suggesting relatively stable ecological conditions and some resilience to environmental change. Ecosystem stability is less common in smaller, more sensitive lakes, such as those within volcanic craters, where external impacts can cause abrupt and rapid fluctuations. A 4100-year diatom and cyanobacteria pigment record from Lake Massoko,

Philip Barker; Richard Telford; Ouassila Merdaci; David Williamson; Maurice Taieb; Annie Vincens; Elisabeth Gibert

2000-01-01

284

Processes within Lake Vostok and their implication for life in Antarctic Subglacial Lakes  

NASA Astrophysics Data System (ADS)

Our understanding of Lake Vostok, the huge subglacial lake beneath the East Antarctic Ice Sheet, has improved recently through the identification of key physical and chemical interactions between the ice sheet and the lake. The north of the lake, where the overlying ice sheet is thickest, is thought to be characterised by subglacial melting, whereas freezing of lake water occurs in the south, resulting in ˜210 m of ice accretion to the underside of the ice sheet. The accreted ice contains lower concentrations of the impurities normally found in glacier ice, suggesting a net transfer of material from meltwater into the lake. The small numbers of microbes found so far within the accreted ice have DNA profiles similar to those of contemporary surface microbes. Microbiologists expect, however, that Lake Vostok, and other subglacial lakes, will harbour unique species, particularly within the deeper waters and associated sediments. The extreme environments of subglacial lakes are characterized by high pressures, low temperatures, permanent darkness, limited nutrient availability and oxygen concentrations that are lower than in the ice that provides the meltwater.

Siegert, M. J.

2003-04-01

285

The hydrochemistry of Lake Vostok and the potential for life in Antarctic subglacial lakes  

NASA Astrophysics Data System (ADS)

Our understanding of Lake Vostok, the huge subglacial lake beneath the East Antarctic Ice Sheet, has improved recently through the identification of key physical and chemical interactions between the ice sheet and the lake. The north of the lake, where the overlying ice sheet is thickest, is characterized by subglacial melting, whereas freezing of lake water occurs in the south, resulting in 210 m of ice accretion to the underside of the ice sheet. The accreted ice contains lower concentrations of the impurities normally found in glacier ice, suggesting a net transfer of material from meltwater into the lake. The small numbers of microbes found so far within the accreted ice have DNA profiles similar to those of contemporary surface microbes. Microbiologists expect, however, that Lake Vostok, and other subglacial lakes, will harbour unique species, particularly within the deeper waters and associated sediments. The extreme environments of subglacial lakes are characterized by high pressures, low temperatures, permanent darkness, limited nutrient availability, and oxygen concentrations that are derived from the ice that provides the meltwater.

Siegert, Martin J.; Tranter, Martyn; Cynan Ellis-Evans, J.; Priscu, John C.; Berry Lyons, W.

2003-03-01

286

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

287

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

288

5. FLAME DEFLECTOR, COMPLETE X15 VEHICLE TEST STAND. Looking east. ...  

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

5. FLAME DEFLECTOR, COMPLETE X-15 VEHICLE TEST STAND. Looking east. - Edwards Air Force Base, X-15 Engine Test Complex, Rocket Engine & Complete X-15 Vehicle Test Stands, Rogers Dry Lake, east of runway between North Base & South Base, Boron, Kern County, CA

289

Mitochondrial phylogeny and phylogeography of East African squeaker catfishes (Siluriformes: Synodontis)  

Microsoft Academic Search

BACKGROUND: Squeaker catfishes (Pisces, Mochokidae, Synodontis) are widely distributed throughout Africa and inhabit a biogeographic range similar to that of the exceptionally diverse cichlid fishes, including the three East African Great Lakes and their surrounding rivers. Since squeaker catfishes also prefer the same types of habitats as many of the cichlid species, we hypothesized that the East African Synodontis species

Stephan Koblmüller; Christian Sturmbauer; Erik Verheyen; Axel Meyer; Walter Salzburger

2006-01-01

290

A coupled lake-atmosphere model (CLAM) and its application to Lake Kinneret  

NASA Astrophysics Data System (ADS)

Kinneret is a 166-km2 lake located in Northern Israel, in the central part of the Jordan Valley, a corridor running from north to south, between the Galilee hills in the west and the Golan Heights in the east. Both the Galilee hills and the Golan Heights reach an elevation of about 400 m above mean sea level (MSL), and the lake is about -210 m (MSL). North of the lake is the mountainous area of the Hermon, culminating at about 2800 m (MSL). About 120 km south of it is the Dead Sea, which is about -410 m (MSL), and about 45 km west of it is the Mediterranean Sea. The complexity of the terrain, combined with relatively arid soil and various ground covers surrounding the lake, results in a very complicated system of atmospheric and lake processes. To understand this system, especially the processes affecting the atmosphere and lake dynamics and thermodynamics, and their effects on Lake Kinneret evaporation, a coupled lake-atmosphere model (CLAM) was developed and applied to the lake region. The CLAM is based on the Regional Atmospheric Modeling System (RAMS) and the oceanic S-coordinate Rutgers University Model (SCRUM). Energy, mass, and momentum are conserved at the interface between the atmosphere and the lake, and appropriate balance equations are applied there. In the atmospheric module, two nested grids are employed to simulate Northern Israel at a resolution of 4 x 4 km2, and the near-lake region at a resolution of 1 x 1 km 2. Synoptic conditions obtained from the National Meteorological Center (NMC) reanalysis are assimilated by the model. Soil moisture, which appears to have a significant impact on atmospheric circulation in this region, was transformed from the normalized difference vegetation index (NDVI). Observations collected during two summers above and inside the lake emphasize the good capability of CLAM to simulate surface fluxes and other microclimatic conditions, as well as lake temperature and currents. Although the lake is small (about 12-km wide and 22-km long), the micrometeorological conditions, lake currents and thermal structure, and the lake-surface heat fluxes vary spatially very significantly, even on a daily basis. It is found that the daily-mean wind curl, which is predominantly determined by the passage of the Mediterranean Sea breeze (MSB) over the lake, is mostly responsible for the gyres in the lake. The thermocline oscillation in the lake is mainly controlled by the surface elevation set up by the time-dependent winds. The intense MSB over the lake in the late afternoon pushes the heated surface water eastward, forces the deep, cooler water to be advected westward, and creates strong mixing in the lake, resulting in a higher temperature off the eastern shore and a lower temperature off the western shore. The variation of lake-surface temperature not only directly affects the atmospheric processes over the lake, but it also changes the wind field, which then influences hydrodynamic processes in the lake. An analytical model of the flow response to spatial variation of atmospheric cooling in coastal ocean was also developed in this study. This model is used to explain the contribution of the spatial variation of latent heat flux to the circulation in Lake Kinneret, and also the cyclonic flow, which is observed in many lakes and semi-enclosed coastal oceans.

Pan, Hai

1999-08-01

291

40. HULETT ORE UNLOADER IN MOTION. VIEW LOOKING EAST. (Also ...  

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

40. HULETT ORE UNLOADER IN MOTION. VIEW LOOKING EAST. (Also see OH-18-14, OH-18-38, and OH-18-39) - Pennsylvania Railway Ore Dock, Lake Erie at Whiskey Island, approximately 1.5 miles west of Public Square, Cleveland, Cuyahoga County, OH

292

39. HULETT ORE UNLOADER IN MOTION. VIEW LOOKING EAST. (Also ...  

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

39. HULETT ORE UNLOADER IN MOTION. VIEW LOOKING EAST. (Also see OH-18-14, OH-18-38, and OH-18-40) - Pennsylvania Railway Ore Dock, Lake Erie at Whiskey Island, approximately 1.5 miles west of Public Square, Cleveland, Cuyahoga County, OH

293

2. View east of filtration bed building. Access bridge to ...  

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

2. View east of filtration bed building. Access bridge to earth covering over reinforced concrete roof is at center right of photograph. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

294

GARAGE EXTERIOR EAST SIDE AND REAR SHOWING PIER SUPPORTS UNDER ...  

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

GARAGE EXTERIOR EAST SIDE AND REAR SHOWING PIER SUPPORTS UNDER SHED-ROOFED REAR STORAGE COMPARTMENT, ASBESTOS SIDING OVER ORIGINAL WOOD SIDING, AND SINGLE CASEMENT WINDOW OVER REAR STORAGE COMPARTMENT. VIEW TO NORTHWEST - Big Creek Hydroelectric System, Big Creek Town, Operator House Garage, Orchard Avenue south of Huntington Lake Road, Big Creek, Fresno County, CA

295

9. View northwest of east entry to central corridor between ...  

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

9. View northwest of east entry to central corridor between the filtration beds. Note square chimney at right center of photograph which is a part of the Armory Street Pumping Station. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

296

26. Photocopied August 1978. CANAL SECTION II, LOOKING EAST, WINTER, ...  

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

26. Photocopied August 1978. CANAL SECTION II, LOOKING EAST, WINTER, 1900. EXCAVATION WORK IN THE EARTH SECTIONS, UNLIKE THE ROCK SECTION, WAS USUALLY CARRIED ON THROUGH THE WINTER. SOME OF THE PILES DRIVEN IN THE FALL OF 1900 IN AN UNSUCESSFUL ATTEMPT TO PREVENT BANK SLIDES APPEAR AT THE LEFT. (47) - Michigan Lake Superior Power Company, Portage Street, Sault Ste. Marie, Chippewa County, MI

297

19. Photocopied August 1978. CANAL SECTION I, LOOKING EAST, 1900, ...  

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

19. Photocopied August 1978. CANAL SECTION I, LOOKING EAST, 1900, WITH SEVERAL PARTIALLY SUBMERGED STEAM SHOVELS SHOWN IN THE FLOODED CANAL. ONE OF THE TEMPORARY BRIDGES CONSTRUCTED OVER THE CANAL RIGHT -OF-WAY IS VISIBLE IN THE BACKGROUND. (39) - Michigan Lake Superior Power Company, Portage Street, Sault Ste. Marie, Chippewa County, MI

298

117. Photocopied August 1978. VIEW OF EAST FOREBAY SHOWING COMPLETED ...  

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

117. Photocopied August 1978. VIEW OF EAST FOREBAY SHOWING COMPLETED APRON. NOVEMBER 24, 1926. CLAY LEFT OVER FROM REFILLING THE AREA BETWEEN FOREBAY FLOOR SILLS IS SHOWN HEAPED AGAINST THE FOREBAY WALL TO PROVIDE AN EXTRA MEASURE OF PROTECTION. (1051) - Michigan Lake Superior Power Company, Portage Street, Sault Ste. Marie, Chippewa County, MI

299

9. View east at rear of Armory Street Pump House ...  

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

9. View east at rear of Armory Street Pump House showing remains of original coal bunker. Area later was the location of an oil tank. - Lake Whitney Water Filtration Plant, Armory Street Pumphouse, North side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

300

The Helium Isotopic Chemistry of Lake Bonney, Taylor Valley, Antarctica: Timing of Late Holocene Climate Change in Antarctica  

Microsoft Academic Search

To better understand the long-term climate history of Antarctica, we studied Lake Bonney in Taylor Valley, Southern Victoria Land (78°S). Helium isotope ratios and He, Ne, Ar and N2 concentration data, obtained from hydrocasts in the East (ELB) and West (WLB) Lobes of Lake Bonney, provided important constraints on the lake’s Holocene evolution. Based on very low concentrations of Ar

Robert J. Poreda; Andrew G. Hunt; W. Berry Lyons; Kathleen A. Welch

2004-01-01

301

Public health assessment for US Smelter and Lead Refinery, Inc. (A/K/A USS Lead Refinery Inc. ) East Chicago, Lake County, Indiana, Region 5. Cerclis no. IND047030226. Final report  

SciTech Connect

The U.S. Smelter and Lead Refinery, Inc. (USS Lead), in East Chicago, Indiana, has been operating as a primary and secondary smelting facility since 1906. Wastes which were produced during smelting operations are calcium sulfate sludge, blast furnace flue-dust, baghouse bags, rubber and plastic battery casings, and waste slag. Limited sampling information is available, and indicates that on-site soils and wastes are contaminated with lead and other metals. Additional sampling off-site surface soils indicate that the contamination has spread off-site as far as one-half mile from the site. Surface water and sediment on-site has also become contaminated with lead and other metals, as well as waste oil. Based on the completed exposure pathways to lead through soil ingestion and dust inhalation, the Agency for Toxic Substances and Disease Registry concludes that contamination from the USS Lead site is a public health hazard.

Not Available

1994-08-24

302

Introduction and spread of the threespine stickleback (Gasterosteus aculeatus) in Lakes Huron and Michigan  

USGS Publications Warehouse

The threespine stickleback (Gasterosteus aculeatus) was not known to occur in the Great Lakes above Niagara Falls until 1980, when it was collected in South Bay, Manitoulin Island, in the Lake Huron basin. By 1984 this species had been found in tributaries of Lakes Huron and Michigan, and in the open waters of both lakes. All specimens identified were the completely plated morph that is most prevalent in fresh water along the east coast of North America. The status of this species in Lakes Huron and Michigan appears to be 'Possibly Established.' If threespine stickleback increase in abundance they may eventually provide additional forage for large salmonids.

Stedman, Ralph M.; Bowen, Charles A., II

1985-01-01

303

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

304

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

305

Are Antarctic Subglacial Lakes Markers of Geologic Boundaries?  

NASA Astrophysics Data System (ADS)

Airborne geophysics has revealed the locations of more than 150 subglacial lakes in the Antarctic interior. The spatial distribution of lakes beneath an ice sheet depends on geothermal flux at the ice-bed interface, ice thickness and flow, surface temperature and accumulation rate, as well as the occurrence of basins in the bed topography. The dynamics of the lake environment, as well as the diversity of controls acting on it, account for the difficulty in reproducing or predicting the distribution of known and probable lakes from models. To date, most efforts to predict the distribution of subglacial lakes have focused on the glaciological facets of the problem. Here we examine the role tectonics may play in the distribution of subglacial lakes. Lake Vostok lies along a tectonic boundary between two distinct geologic provinces-relatively flat-lying continental margin sediments to the west of the lake and folded and compressed crust material to the east. This suture is possibly the result of Precambrian tectonic activity which produced the Vostok basin and thus is the fundamental tectonic control on the location of Lake Vostok. This work examines the relative contribution of glaciological and tectonic controls to determine if other subglacial lakes may also reside on geologic or tectonic boundaries.

Smith, A. E.; Bell, R.; Studinger, M.

2005-12-01

306

Prokaryotic communities of the north-eastern Mongolian soda lakes  

Microsoft Academic Search

We have studied the activity and composition of several geochemically significant physiological groups of bacteria in more than twenty alkaline salt lakes of the north-east Mongolia steppe with water salinity from 3 to 390 g l–1 and pH values ranging from 9.0 to 10.6. Active and diverse microbial communities have been found in most of the lakes. The methanotrophic bacteria were represented

Dimitry Yu. Sorokin; Vladimir M. Gorlenko; Bair B. Namsaraev; Zorigto B. Namsaraev; Anatoly M. Lysenko; Bulat Ts. Eshinimaev; Valentina N. Khmelenina; Yuri A. Trotsenko; J. Gijs Kuenen

2004-01-01

307

Lake Muzahi, Rwanda: limnological features and phytoplankton production  

Microsoft Academic Search

Lake Muhazi, a small lake of Rwanda (East Africa) was studied from 1986 to 1990. A dramatic decrease of the catch of Oreochromis niloticus (350 T y?1 in the fifties vs 30 T y?1 in 1982) suggested a loss of productivity or overfishing. In the same period, other ecological changes occurred: the submerged\\u000a macrophytes regressed and there was a decrease

R. Mukankomeje; P. D. Plisnier; J. P. Descy; L. Massaut

1993-01-01

308

Hydrothermal vents of Yellowstone Lake, Yellowstone National Park, Wyoming  

SciTech Connect

Hydrothermal vent systems within Yellowstone Lake are located within the Yellowstone caldera in the northeastern and West Thumb sections of the lake. The vent systems lie within areas of extremely high geothermal gradients (< 1,000 C/km) in the lake sediments and occur as clusters of individual vents that expel both hydrothermal fluids and gas. Regions surrounding the vents are colonized by unique, chemotropic biologic communities and suggest that hydrothermal input plays an important role in the nutrient dynamics of the lake's ecosystem. The main concentration of hydrothermal activity occurs in the northeast region of the main lake body in a number of locations including: (1) along the shoreline from the southern edge of Sedge Bay to the inlet of Pelican Creek; (2) the central portion of the partially submerged Mary Bay phreatic explosion crater, within deep (30--50 m) fissures; (3) along the top of a 3 km long, steep-sided ridge that extends from the southern border of Mary Bay, south-southeast into the main lake basin; and (4) east of Stevenson Island along the lower portion of the slope (50--107 m) into the lake basin, within an anastomosing series of north to northwest trending, narrow troughs or fissures. Hydrothermal vents were also located within, and surrounding the West Thumb of Yellowstone Lake, with the main concentration occurring the offshore of the West Thumb and Potts Geyser Basin. Hydrothermal vents in Yellowstone Lake occur along fractures that have penetrated the lake sediments or along the tops of ridges and near shore areas. Underneath the lake, rising hydrothermal fluids encounter a semi-permeable cap of lake sediments. Upwardly convecting hydrothermal fluid flow may be diverted by the impermeable lake sediments along the buried, pre-existing topography. These fluids may continue to rise along topography until fractures are encountered, or the lake sediment cover is thinned sufficiently to allow egress of the fluids.

Kaplinski, M.A.; Morgan, P. (Northern Arizona Univ., Flagstaff, AZ (United States). Geology Dept.)

1993-04-01

309

Geometric dependency of Tibetan lakes on glacial runoff  

NASA Astrophysics Data System (ADS)

The Tibetan plateau is an essential source of water for South-East Asia. The run-off from its ~ 34 000 glaciers, which occupy an area of ~ 50 000 km2, feed Tibetan lakes and major Asian rivers like Indus and Brahmaputra. Reported glacial shrinkage likely has its impact on the run-off. Unfortunately, accurate quantification of glacial changes is difficult over the high relief Tibetan plateau. However, it has been recently shown that it is possible to directly assess water level changes of a significant part of the ~ 900 Tibetan lakes greater than one square kilometer. This paper exploits different remote sensing products to explicitly create links between Tibetan glaciers, lakes and rivers. The results allow us first to differentiate between lakes with and without outlet. In addition, we introduce the notion of geometric dependency of a lake on glacial runoff, defined as the ratio between the total area of glaciers draining into a lake and the area of the catchment of the lake. These dependencies are determined for all ~ 900 Tibetan lakes. To obtain these results, we combine the so-called CAREERI glacier mask, a lake mask based on the MODIS MOD44W water product and the HydroSHEDS river network product derived from SRTM elevation data. Based on a drainage network analysis, all drainage links between glaciers and lakes are determined. The results show that 25.3% of the total glacier area directly drains into one of 244 Tibetan lakes. The results also give the geometric dependency of each lake on glacial runoff. For example, there are 10~lakes with direct glacial runoff from at least 240 km2 of glacier. Three case studies, including one over the well-studied Nam Tso, demonstrate how the geometric dependency of a lake on glacial runoff can be directly linked to hydrological processes.

Phan, V. H.; Lindenbergh, R. C.; Menenti, M.

2013-01-01

310

Reassessment of Lake Victoria Upper Nile River paleohydrology from oxygen isotope records of lake-sediment cellulose  

Microsoft Academic Search

Reconstruction of lake-water delta18O from analysis of cellulose delta18O in two sediment cores from Lake Victoria, East Africa, shows a large shift to lower values during the terminal Pleistocene. This shift records the transition from closed- to open-basin conditions following desiccation at the Last Glacial Maximum. Although oxygen isotope analysis of cellulose from one core had placed this overflow at

Kristina R. M. Beuning; Kerry Kelts; Jim Russell; Brent B. Wolfe

2002-01-01

311

Semi-empirical lake level (SELL) model for mapping lake water depths from partially clouded satellite data  

NASA Astrophysics Data System (ADS)

Information on the variability in surface water is critical to understand the impact of climate change and global water cycle. Surface water features such as lakes, or reservoirs can affect local weather and regional climate. Hence, there is a widespread demand for accurate and quantitative global observations of surface water variability. Satellite imagery provides a direct way to monitor variations in surface water. However, estimating accurate surface area from satellite imagery can be a problem due to clouds. Hence, the use of optical imagery for operational implementation has been a challenge for monitoring variations in surface water. In this research, a semi-empirical lake level (SELL) model is developed to derive lake/reservoir water levels from partially covered satellite imagery. SRTM elevation combined with bathymetry was used to derive the relationships between lake depth vs. surface area and shore line (L). Using these relationships, lake level/depth (D) was estimated from the surface area (A) and/or shore line (L) delineated from Landsat and MODIS data. The SELL model was applied on Lake Turkana, one of the rift valley lakes in East Africa. First, Lake Turkana water levels were delineated using cloud-free or partially clouded Landsat and MODIS imagery over 1993-2009 and 2002-2009 time periods respectively. Historic lake depths were derived using 1972-1992 Landsat imagery. Lake depths delineated using this approach were validated using TOPEX/Poseidon/Jason satellite altimetry data. It was found that lake depths derived using SELL model matched reasonably well with the satellite altimetry data. The approach presented in this research can be used to (a) simulate lake water level variations in data scarce regions (b) increase the frequency of observation in regions where cloud cover is a problem (c) operationally monitor lake water levels in ungauged basins (d) derive historic lake level information using satellite data.

Velpuri, N.; Senay, G. B.

2011-12-01

312

Water management sustainability in reclaimed coastal areas. The case of the Massaciuccoli lake basin (Tuscany, Italy)  

Microsoft Academic Search

The lake of Massaciuccoli (7 km2 wide and about 2 m deep) and its palustrine nearby areas (about 13 km2 wide) constitute a residual coastal lacustrine and marshy area largerly drained by 1930. In terms of hydrological boundaries, the lake watershed is bordered by carbonate to arenaceous reliefs on the east, by a sandy coastal shallow aquifer on the west

Rudy Rossetto; Ilaria Baneschi; Paolo Basile; Massimo Guidi; Chiara Pistocchi; Tiziana Sabbatini; Nicola Silvestri; Enrico Bonari

2010-01-01

313

Interpretation of seismic and potential field data from western New York State and Lake Ontario  

Microsoft Academic Search

Lithoprobe and industry seismic profiles have furnished evidence of major zones of easterly dipping Grenville deformed crust extending southwest from exposed Grenville rocks north of Lake Ontario. Additional constraints on subsurface structure limited to the postulated Clarendon–Linden fault system south of Lake Ontario are provided by five east–west reflection lines recorded in 1976. Spatial correlations between seismic structure and magnetic

Khaled Ouassaa; David A. Forsyth

2002-01-01

314

Interactions between calcite precipitation (natural and artificial) and phosphorus cycle in the hardwater lake  

Microsoft Academic Search

The influence of calcite precipitation on the phosphorus cycle in stratified hardwater lake was studied before and during experiments with a new restoration technique. Surveys of the chemical composition of water column and monitoring of settling particles of Lake Luzin (North–East) showed that calcite precipitation occurs each year over 2–3 periods during spring and summer. The change of the phosphorus

Maria Dittrich; Rainer Koschel

2002-01-01

315

Holocene vegetation and climate history at Hurleg Lake in the Qaidam Basin, northwest China  

Microsoft Academic Search

We present fossil pollen data and discuss their climatic interpretations from a 688-cm-long sediment core from Hurleg Lake, a freshwater lake located in the Qaidam Basin on the NE Tibetan Plateau, just beyond the northern limit of the East Asian summer monsoon influence. The reconstruction of the Holocene vegetation and climate history was aided by modern surface pollen analysis. The

Yan Zhao; Zicheng Yu; Fahu Chen; Emi Ito; Cheng Zhao

2007-01-01

316

Spatial distribution and temporal changes in the fish populations of Lake Victoria  

Microsoft Academic Search

The fisheries of Lake Victoria in East Africa must be managed effectively to ensure sustainable food supplies. This has been impossible in the past due to inadequate knowledge of commercially important fish stocks. Here we present the first acoustic abundance estimates of fish in Lake Victoria. Five lakewide acoustic surveys were conducted between 1999 and 2001, using the Simrad EY500

Albert Getabu; Rhoda Tumwebaze; David N MacLennan

2003-01-01

317

Strong Magnetic Levels in Lake Chapala Sediments (western Mexico): Their Mineralogy and Stratigraphic Significance  

Microsoft Academic Search

Lake Chapala, located 120 km northeast of Colima Volcano, lies at the north and northeast of the Citala rift in the Trans-Mexican\\u000a Volcanic Belt. It belongs to the watershed of the Lerma River, which originates from the Mexico City area, 450 km to the east.\\u000a Sediment cores, 0.5–2 m long, were collected from the lake. Magnetic susceptibility of the lake sediments generally ranges

François Michaud; Hermes U. Ramírez-Sánchez; Claude Parron; Pedro F. Zárate-del Valle; François Fernex; Geneviève Barci-Funel

2006-01-01

318

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.

319

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

320

Identification and correlation of visible tephras in the Lake Suigetsu SG06 sedimentary archive, Japan: chronostratigraphic markers for synchronising of east Asian/west Pacific palaeoclimatic records across the last 150 ka  

NASA Astrophysics Data System (ADS)

The Lake Suigetsu SG06 sedimentary archive from Honshu Island, central Japan, provides a high-resolution palaeoenvironmental record, including a detailed record of explosive volcanism from Japan and South Korea. Thirty visible tephra are recorded within the 73 m-long SG06 core, which spans the last ˜150 ka. Here we describe and characterise these tephras based on major element glass composition, which is useful for the identification and correlation of these tephras and the age models of the records in which they are found. Utilising the large number of radiocarbon measurements (n > 600) from terrestrial plant macrofossils in the Lake Suigetsu SG06 record, we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka. Glass compositional data of some of the largest eruptions from Japan (K-Ah, AT, Aso-4, Aso-A, Aso-D, and Ata; sampled at proximal outcrops) are also presented. These data show that the major element glass chemistry is distinctive for many of the visible SG06 tephra units, and allows some of the layers to be correlated to known eruptions from volcanoes in Japan and South Korea, namely K-Ah (SG06-0967), U-Oki (SG06-1288), AT (SG06-2650), Aso-4 (SG06-4963/SG06-4979), K-Tz (SG06-5181), Aso-ABCD (SG06-5287) and Ata (SG06-5181). The following ages were obtained for the SG06 tephra units: 3.966-4.064 cal. ka BP (95.4% probability range) for the SG06-0588 tephra, 10.242-10.329 cal. ka BP (95.4% probability range) for SG06-1293, 19.487 ± 112 SG062012 ka BP (2 ?) for SG06-1965, 28.425 ± 194 SG062012 ka BP (2 ?) for SG06-2504, 28.848 ± 196 SG062012 ka BP (2 ?) for SG06-2534, 29.765 ± 190 SG062012 ka BP (2 ?) for SG06-2601, 29.775 ± 191 SG062012 ka BP (2 ?) for SG06-2602, 43.713 ± 156 SG062012 ka BP (2 ?) for SG06-3485, 46.364 ± 202 SG062012 ka BP (2 ?) for SG06-3668, 49.974 ± 337 SG062012 ka BP (2 ?) for SG06-3912, 50.929 ± 378 SG062012 ka BP (2 ?) for SG06-3974, and improved ages for two of the most important tephra markers across Japan, the K-Ah (7.165-7.303 cal. ka BP at 95.4% probability range; SG06-0967) and AT tephra (30.009 ± 189 SG062012 ka BP at 2 ?; SG06-2650).

Suigetsu 2006 Project Members Smith, Victoria C.; Staff, Richard A.; Blockley, Simon P. E.; Bronk Ramsey, Christopher; Nakagawa, Takeshi; Mark, Darren F.; Takemura, Keiji; Danhara, Toru

2013-05-01

321

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

322

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

323

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

324

The precipitation response to the desiccation of Lake Chad  

SciTech Connect

Located in the semi-arid African Sahel, Lake Chad has shrunk from a surface area of 25000 km2 in 1960 to about 1350 km2 due to a series of droughts and anthropogenic influences. The disappearance of such a large open-water body can be expected to have a noticeable effect on the meteorology in the surroundings of the lake. The impact could extend even further to the west as westward propagating convective systems pass Lake Chad in the rainfall season. This study examines the sensitivity of the regional hydrology and convective processes to the desiccation of the lake using a regional atmospheric model. Three Lake Chad scenarios are applied reflecting the situation in 1960, the current situation and a potential future scenario in which the lake and the surrounding wetlands have disappeared. The model simulations span the months July-September in 2006, which includes the rainfall season in the Lake Chad area. Total precipitation amounts and the components of the hydrological cycle are found to be hardly affected by the existence of the lake. A filled Lake Chad does, however, increase the precipitation at the east side of the lake. The model results indicate that the boundary layer moisture and temperature are significantly altered downwind of the lake. By investigating a mesoscale convective system (MCS) case, this is found to affect the development and progress of the system. At first, the MCS is intensified by the more unstable boundary layer air but the persistence of the system is altered as the cold pool propagation becomes less effective. The proposed mechanism is able to explain the differences in the rainfall patterns nearby Lake Chad between the scenarios. This highlights the local sensitivity to the desiccation of Lake Chad whereas the large-scale atmospheric processes are not affected.

Lauwaet D.; VanWeverberg K.; vanLipzig, N. P. M., Weverberg, K. V., Ridderb, K. D., and Goyens, C.

2012-04-01

325

Topographic and hydrological controls on Subglacial Lake Ellsworth, West Antarctica  

NASA Astrophysics Data System (ADS)

Subglacial Lake Ellsworth (SLE) was identified using reconnaissance data collected in the 1970s, here we present more detailed surveys. SLE lies beneath 3.2 km of ice in a subglacial valley in West Antarctica. It has an area of only ~18 km2, is dissimilar to the large tectonically-controlled lakes beneath East Antarctica and is a strong candidate for in situ exploration. Our analysis indicates that the ice above SLE is floating on a fluid whose density is 950-1013 kg m-3. This could indicate freshwater, but certainly precludes seawater, or high salt, acid, or clathrate content. The water in the lake is unlikely to be produced solely by local melt; it is more likely delivered via subglacial drainage. Our surveys show no identifiable hydrological barrier to outflow, meaning SLE is effectively full; new water entering the lake is likely balanced by outflow, which would drain into another lake that we have also identified.

Vaughan, David G.; Rivera, Andrés; Woodward, John; Corr, Hugh F. J.; Wendt, Jens; Zamora, Rodrigo

2007-09-01

326

Integrating physical and chemical characteristics of lakes into the glacially influenced landscape of the Northern Cascade Mountains, Washington State, USA  

USGS Publications Warehouse

A basic knowledge of the physical and chemical characteristics of lakes is needed by management to make informed decisions to protect water resources. In this study we investigated some of the physical and chemical characteristics of 58 lakes in alpine, subalpine, and forest vegetation zones in a natural area (North Cascades National Park Service Complex) between 1989 and 1993. The objectives of the study were to: (1) document the time of ice-out relative to lake elevation; (2) determine how a sharp climate gradient west and east of the hydrologic divide affected the time of ice-out for subalpine lakes; and (3) assess how lake water quality was associated with lake elevation, lake depth, and basin geology. As expected, lake ice-out times occurred earlier with decreasing elevation. East-slope subalpine lakes iced-out earlier than did west-slope subalpine lakes because the east slope of the study area was drier and warmer than the west slope. On average, the lakes were relatively cold, neutral in pH, and low in dissolved substances and concentrations of nitrogen and phosphorus. Although some shallow lakes (depth ,10 m) exhibited the highest alkalinities, conductivities, and concentrations of phosphorus and nitrogen, most shallow lakes exhibited low values for these variables that were comparable to values observed in deep lakes. Geology did not play a major role in segregating the lakes based on water quality. Overall, lake temperature, pH, alkalinity, conductivity, and concentrations of total phosphorus and total Kjeldahl N increased with decreasing elevation. These changes in water quality with decreasing elevation in this temperate mountainous region corresponded with warmer air temperatures and increased vegetation biomass, soil depth and maturity, and dissolved substances and nutrients.

Larson, Gary L.; Lomnicky, G. A.; ; Liss, W. J.; Deimling, E.

1999-01-01

327

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

328

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

329

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

330

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.

331

A Water Balance Model for assessing Hydro Climatic Variability in Tropical Lake Systems: Application to Lake Babati and Lake Emakat, Nothern Tanzania  

NASA Astrophysics Data System (ADS)

A comprehensive understanding of lake hydrology is important to enhance the interpretation of information on past climatic variations retained in tropical lakes as well as to investigate the effect of future climate conditions on lake ecosystems. In this study, a lumped water balance model is developed to describe historical lake water levels and to investigate the impacts of hydro-climatological changes on Lake Emakat and Lake Babati, two closed tropical lakes in Northern Tanzania (East Africa). The model concept is based on maintaining the water mass balance of the lake system, which is simplified into three main modules: the lake, its catchment area and the connected groundwater reservoir. Water mass exchanges with the atmosphere occur through precipitation, the main input, and evaporation, calculated from meteorological variables using two different energy balance equations. The model also integrates lake and groundwater interaction, by letting the lake water surface balance with the water table in the surrounding groundwater reservoir after every time step. A FORTRAN code is used to solve the water balance equation on a year time step and give the lake volume change resulting from meteorological inputs. The associated lake surface area and lake level are then determined from a depth-volume-area relationship developed from a high resolution bathymetric and topographical maps of the lake and its catchment. The model parameters were calibrated using available meteorological data and corresponding lake level records. A sensitivity study to assess the relative importance of different hydro-meteorological parameters on the model response indicates that changes in cloud fraction have the largest impact on evaporation, the most important component of the water mass balance. This parameter, therefore, proved to be one of the ultimate control factors of the lakes water balance. The model application to Lake Emakat suggests that precipitation and cloud fraction changes are the only climate related factors that could justify the large volume change experienced by the Lake during a 200 year period, 10,000 years BP, as estimated by proxy data. On the other hand, the model was applied to establish the necessary ambient condition changes to produce a dry-out and an overflow condition of Lake Babati and to investigate the lake system response to future IPCC climate change projections in the study area. The model shows that a sustained temperature change of less than 3oC or a precipitation change of about 100 mm/year is sufficient to bring the lake from a dry-out to an overflow condition. Simulations of IPCC derived scenarios indicate a clear tendency of the lake to increase its volume and reach the overflow level in relatively short time (approximately 10 years). Despite the model uncertainties, mainly due to limited data, it provides a means for improved interpretation of proxy data of lake level and past climatic changes retrieved from lake sediments. Furthermore, the model ability to predict the lakes hydrological response to future variations in hydroclimatic conditions and catchment characteristics offers a valuable decision support tool for water resources management

Pericles Mbanguka, Rene; Girons Lopez, Marc; Jarsjö, Jerker

2013-04-01

332

Pleistocene lake level changes in Western Mongolia  

NASA Astrophysics Data System (ADS)

Global cooling in the Early Pleistocene caused extensive continental glaciation in the northern hemisphere including the arid areas of Central Asia. The reduction of temperatures (particularly summer temperatures) reduced evaporation and strengthened the importance of precipitation. The simultaneity of "lakes periods" (pluvials) and stages of glaciation is established experience confirmed by investigations in the west of North America and Russia. In the Mongolian Great Lakes Depression new evidence for similar conditions is found. The Great Lakes Depression is one of the largest in Central Asia, and is divided into 2 main Lakes basins: Hyargas Lake Basin and Uvs Lake Basin. The basin is 600-650 km in length with a width of 200-250 km in the north and 60-100 km in the south. Total catchment area is about 186600 km2. The elevation of the basin floor is from 1700 m a.s.l. to 760 m a.s.l., decreasing to the north and south-east. The depression extends south-north and is bounded by mountains: Tannu-Ola to the north, Hangai to the east; Gobi Altai to the south and Mongolian Altay to the west. The maximum elevation of the mountains is 4000 m a.s.l. There are some mountains with an elevation between 2000 and 3000 m a.s.l in the lake catchment. These mountains are not glaciated today. The geological record [1] suggests the Great Lakes Depression already existed in the Mesozoic, but assumed its modern form only during the Pliocene-Quaternary when tectonic movements caused the uplift of the surrounding mountains. A phase of tectonic stability occurred during the Late Quaternary. The depression is filled by Quaternary fluvial, aeolian and lacustrine deposits (e.g. sand, pebbles). The Neogene deposits are represented by coloured clay, marl, sand and sandstone [1]. Hyargas Lake is the end base level of erosion of the lake group consisting of the Hara-Us Nur, Dorgon, Hara Nur and Airag lakes. Hyargas is one of the largest lakes in Mongolia, with a water surface of 1,407 km2. The lake is 75 km long and 31 km wide. Its mean depth is 47 m, with the deepest point reaching 80 m, and its total water volume is 66,034 km3 and drainage basin 115,500 km2. The only water flowing into it is Galbiyn Hooloi. Hara-Us Nur Lake is a fresh-water (mineralization ca 107-348 mg/l, pH -7.8) basin situated in the Mongolian Great Lakes Depression [2]. Hara-Us Nur is fed by the Kobdo and Buyant rivers, which start in the Mongolian Altay, and outflows via the Chano-Hairkhan River into Hara-Us Nur Lake. Hara-Us Nur is divided by the Ak-Bashi Island into two subbasins. It has a water area of 1857 km2 with a length of 72.2 km and a maximum width of 27 km [4]. The maximum depth is 4 m and the average depth is ca 2 m [5,6]. The terraced lake shores are covered by steppe and desert vegetation. Pharagmites is abundant in the river deltas and close to the shore-line and the shallow-water littoral is covered by rich aquatic vegetation, including Myriophyllum verticulatum, Zannichelia pedunculata, Utricularia vulgaris [3]. Hara-Nur Lake is situated in the desert steppe subzone of the Mongolian Great Lakes Depression. The fresh-water Hara-Nur Lake receives inflow from Hara-Us Nur Lake via the Chano-Hairkhan River. There are two outflows from the lake one outflow is via a 10 km-long channel which flows to the Dzabhan River, which in turn flows into the closed Hyargas Lake. The other outflow is a small semi-permanent stream with flows southward into the closed brackish-water Dorgon Lake. Hara-Nur has a water area of 57,500 ha, with a length of 37 km and a maximum width of ca 24 km. The maximum depth is 7 m and the average depth is ca 4 m. The mean water mineralization is 260 mg/l and the pH is 8.0 [5]. The catchment area is ca 7,200,000 ha. Lake Ureg located in the Mongolian Altay at an altitude of 1425 m.a.s.1., this lake has an area 237.6 km2 and maximum depth of 48 m. Secchi disk transparency is to 8 m. Macrophyte beds cover up to 20 per cent of the lake area, with the common cane sedges and horsetails dominant. The benthic fauna is poor, and only single pecime

Borodavko, P. S.

2009-04-01

333

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

334

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

335

The Precambrian crustal structure of East Africa  

NASA Astrophysics Data System (ADS)

In this thesis, the Precambrian crustal structure of East African is investigated along with the crustal structures of three Cenozoic rift basins located in the western branch of the East African Rift System (EARS). In the first part of the thesis, P-wave receiver functions are modeled using the H-k method to obtain new insights about the bulk composition and thickness of the crust for Precambrian terrains throughout East Africa. The average crustal thickness for all but one of the terrains is between 37 and 39 km. An exception is the Ubendian terrain, which has an average crustal thickness 42 km. In all terrains, the average Poisson's ratio is similar, ranging from 0.25 to 0.26, indicating a bulk crustal composition that is felsic to intermediate. The main finding of this study is that crustal structure is similar across all terrains, which span more than 4.0 Ga of earth history. There is no discernable difference in the crustal thicknesses and Poisson's ratios between the Archean and Proterozoic terrains, or between the Proterozoic terrains, unlike the variability in Precambrian crustal structure found in many other continents. In the second part of the thesis, a joint inversion of Rayleigh wave phase and group velocities and receiver functions was used to investigate the shear wave velocity structure of the crust and uppermost mantle beneath the Precambrian terrains of East Africa. In comparison with other areas of similar age in southern and western Africa where the same joint inversion method has been applied, I find that while there is little difference in the mean shear wave velocities for the entire crust across all of the Precambrian terrains, and also few differences in the thickness of the crust, there exists substantial variability in lower crustal structure. This variability is reflected primarily in the thickness of the lower crustal layers with shear wave velocities ? 4.0 km/s. This variability is found both within terrains of the same age (i.e., Archean) as well as terrains of different ages. In global studies of continental crustal structure, it is shown that high velocity (Vp ˜ 7km/s and Vs ˜4.0 km/s) lower crustal layers indicate the presence of mafic rocks, and that such layers are common in most Precambrian terrains. In contrast, my results show large variability in lower crustal structure between terrains of similar age within Africa, suggesting that making generalizations about the structure and evolution of continental crust based on global averages of the crustal velocity structure is difficult to do. The results of this study indicate that the local geological history of each terrain can lead to significant variability in crustal structure, making the use of global averages less representative of global processes than previously thought. In the third part of this thesis, forward modeling of receiver functions is used to investigate the crustal structure beneath three of the rift basins in the western branch of the East African Rift System (Lake Albert, Lake Edward and the northern part of the Lake Malawi rifts). Modeling results reveal sediment thickness of about 1 km beneath stations BUTI and KATE, located at the margins of the Lake Albert and Lake Edward rifts, respectively, and about 1.5 km beneath station KYLA in the northern part of the Lake Malawi rift. The Poisson's ratio obtained (0.4) indicate that the sediments are poorly consolidated. A thin sedimentary layer (1--1.5 km) and high Poisson's ratio is consistent with the young age (Miocene) of the rift basins. The Ps from the Moho cannot be easily identified because the first 5--6 sec of data are dominated by the Ps conversion from the sediment-bedrock interface and its reverberations. Therefore crustal thickness beneath these stations remains unknown.

Tugume, Fred Alex

336

High Resolution Seismic Attenuation Tomography at Medicine Lake Volcano, California.  

National Technical Information Service (NTIS)

Medicine Lake Volcano, a broad shield volcano about 50km east of Mount Shasta in northern California, produced rhylotic eruptions as recently as 400 years ago. Because of this recent activity it is of considerable interest to producers of geothermal energ...

J. J. Zucca P. W. Kasameyer

1987-01-01

337

Species Distinction and the Biodiversity Crisis in Lake Victoria  

Microsoft Academic Search

Until the 1970s, the fish fauna of Lake Victoria in East Africa was dominated by about 500 endemic haplochromine cichlid species, which comprised about 80% of the demersal fish mass. The cichlids were extremely diverse ecologically; however, the small diversity in gross morphology and the presence of intraspecific variation made it difficult to distinguish among species. In the first half

F. Witte; J. H. Wanink; M. Kishe-Machumu

2007-01-01

338

JPRS Report, East Europe.  

National Technical Information Service (NTIS)

Partial Contents: East Europe, Party Activities, Socialist Party, Freedom Fighters, Education, Youth Training, Historian, Death Penalty, Peace Making Duties, Socialism, Communism, Economics, Restructuring, Catastrophic Condition, Computer Production, edit...

1988-01-01

339

Shores of Tibet: History of Changing Lake Levels across the Tibetan Plateau  

NASA Astrophysics Data System (ADS)

We present a new lake level chronology based on 14C-dated shoreline tufas (inorganic CaCO3) from closed-basin lake Ngangla Ring Tso in the western Tibetan Plateau that, consistent with other lake and climate records, suggests insolation-driven increase in monsoon intensity during the early Holocene led to increased precipitation on the interior of the plateau. Lake level rose abruptly at 10.1 ka BP to a highstand elevation 133 m above the modern lake level, stabilized there until 9.0 ka BP and then dropped periodically over the Holocene. Millenial-scale variability in lake level during the Holocene is similar to proxy records of the Indian Summer Monsoon, suggesting that this system is the dominant climatic influence on lake levels in western Tibet. During the early Holocene highstand, Ngangla Ring Tso was 5.1 times larger in area than modern. Comparison of modern areas and highest paleo-shoreline areas of 170 other closed-basin lakes across the plateau shows that this increase in area is consistent for lakes in the western plateau, but the magnitude decreases to little more than 1.2 times larger to the east. There is evidence to suggest that modern monsoon precipitation patterns on the plateau can be divided at ~86° E into a western region strongly correlated with the Indian Summer Monsoon, and an eastern region sharing characteristics of the East Asian Summer Monsoon. There is a modern gradient in annual precipitation from west to east on the plateau wherein the western plateau receives 60% less precipitation than the east. There is a significant correlation between precipitation and modern lake size, with larger lakes on average in the eastern plateau today. Landsat-based time-series of selected lakes, including Ngangla Ring Tso, for these two regions over the period 1972 to 2010 show distinctly different patterns of modern lake area variation. In the west, lakes are largest in the 1970's, and have smallest areas in the late 1990's. Lakes to the east are smallest during the 1970's, and increase continuously up to 34% greater in the late 2000's. We suggest, based on modern and paleoshoreline evidence, that the two regions of precipitation are an enduring feature of plateau climate, but strengthening of the Indian Summer Monsoon may reverse the observed precipitation gradient during insolation maxima.

Hudson, A. M.; Quade, J.; Lei, G.

2011-12-01

340

55. LOOKING EAST FROM HEAD OF PLANE 2 EAST. POWER ...  

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

55. LOOKING EAST FROM HEAD OF PLANE 2 EAST. POWER HOUSE AND FLUME VISIBLE TO RIGHT, TAILRACE RUNNING THROUGH CENTER OF PHOTOGRAPH. CRADLE TO INCLINED PLANE 3 EAST IS VISIBLE IN BACKGROUND TO LEFT. - Morris Canal, Phillipsburg, Warren County, NJ

341

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

342

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

343

A 100 year sedimentary record of heavy metal pollution in a shallow eutrophic lake, Lake Chaohu, China.  

PubMed

This study has worked on the evaluation of the temporal and spatial evolution of heavy metal contamination in sediment taken from a shallow eutrophic lake, Lake Chaohu, China, over the last 100 years, and thereby used (137)Cs and (210)Pb dating, a PIRLA procedure, statistical analysis, geochemical normalization and a enrichment factor calculation (EF). Concentrations of 5174, 29?325, 10.7, 36.4, 20.4, 386.0, 21.1 and 38.4 mg kg(-1) for Ti, Fe, Co, Cr, Cu, Mn, Pb and Zn, respectively, are proposed as natural background values for the Lake Chaohu based on a PIRLA procedure. The contamination history from the last 100 years can be divided into two periods. Before the 1960s, heavy metal contamination did not occur and there was no spatial difference for heavy metal distribution. Since the 1960s, heavy metal enrichment and contamination has occurred, and the west half of the lake region showed a higher degree of contamination than the east half to various intensified anthropogenic activities. In the east half of the lake region, the anthropogenic source of heavy metals mainly originated from agricultural intensification, whereas in the west half of the lake it originated from city runoff and industry as well as agriculture. In all anthropogenic heavy metals, Co is only from industry. PMID:21915415

Zan, Fengyu; Huo, Shouliang; Xi, Beidou; Su, Jing; Li, Xiang; Zhang, Jingtian; Yeager, Kevin M

2011-09-13

344

Geology and geomorphology of Bear Lake Valley and upper Bear River, Utah and Idaho  

USGS Publications Warehouse

Bear Lake, on the Idaho-Utah border, lies in a fault-bounded valley through which the Bear River flows en route to the Great Salt Lake. Surficial deposits in the Bear Lake drainage basin provide a geologic context for interpretation of cores from Bear Lake deposits. In addition to groundwater discharge, Bear Lake received water and sediment from its own small drainage basin and sometimes from the Bear River and its glaciated headwaters. The lake basin interacts with the river in complex ways that are modulated by climatically induced lake-level changes, by the distribution of active Quaternary faults, and by the migration of the river across its fluvial fan north of the present lake. The upper Bear River flows northward for ???150 km from its headwaters in the northwestern Uinta Mountains, generally following the strike of regional Laramide and late Cenozoic structures. These structures likely also control the flow paths of groundwater that feeds Bear Lake, and groundwater-fed streams are the largest source of water when the lake is isolated from the Bear River. The present configuration of the Bear River with respect to Bear Lake Valley may not have been established until the late Pliocene. The absence of Uinta Range-derived quartzites in fluvial gravel on the crest of the Bear Lake Plateau east of Bear Lake suggests that the present headwaters were not part of the drainage basin in the late Tertiary. Newly mapped glacial deposits in the Bear River Range west of Bear Lake indicate several advances of valley glaciers that were probably coeval with glaciations in the Uinta Mountains. Much of the meltwater from these glaciers may have reached Bear Lake via groundwater pathways through infiltration in the karst terrain of the Bear River Range. At times during the Pleistocene, the Bear River flowed into Bear Lake and water level rose to the valley threshold at Nounan narrows. This threshold has been modified by aggradation, downcutting, and tectonics. Maximum lake levels have decreased from as high as 1830 m to 1806 m above sea level since the early Pleistocene due to episodic downcutting by the Bear River. The oldest exposed lacustrine sediments in Bear Lake Valley are probably of Pliocene age. Several high-lake phases during the early and middle Pleistocene were separated by episodes of fluvial incision. Threshold incision was not constant, however, because lake highstands of as much as 8 m above bedrock threshold level resulted from aggradation and possibly landsliding at least twice during the late-middle and late Pleistocene. Abandoned stream channels within the low-lying, fault-bounded region between Bear Lake and the modern Bear River show that Bear River progressively shifted northward during the Holocene. Several factors including faulting, location of the fluvial fan, and channel migration across the fluvial fan probably interacted to produce these changes in channel position. Late Quaternary slip rates on the east Bear Lake fault zone are estimated by using the water-level history of Bear Lake, assuming little or no displacement on dated deposits on the west side of the valley. Uplifted lacustrine deposits representing Pliocene to middle Pleistocene highstands of Bear Lake on the footwall block of the east Bear Lake fault zone provide dramatic evidence of long-term slip. Slip rates during the late Pleistocene increased from north to south along the east Bear Lake fault zone, consistent with the tectonic geomorphology. In addition, slip rates on the southern section of the fault zone have apparently decreased over the past 50 k.y. Copyright ?? 2009 The Geological Society of America.

Reheis, M. C.; Laabs, B. J. C.; Kaufman, D. S.

2009-01-01

345

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

346

1. OVERVIEW OF EXTREME EAST END OF BIG CREEK TOWN ...  

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

1. OVERVIEW OF EXTREME EAST END OF BIG CREEK TOWN ACROSS POWERHOUSE NO. 2 FOREBAY (POWERHOUSE NO. 1 AFTERBAY). TOWER CARRYING TRANSMISSION LINES FROM POWERHOUSE NO. 1 IS AT PHOTO CENTER. BEHIND TOWER IS BUILDING 103. TO PHOTO LEFT OF BUILDING 103 IS BUILDING 105. VIEW TO NORTH. - Big Creek Hydroelectric System, Big Creek Town, Operator House, Orchard Avenue south of Huntington Lake Road, Big Creek, Fresno County, CA

347

2. EXTERIOR OF FRONT (EAST SIDE) OF BUILDING 105 SHOWING ...  

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

2. EXTERIOR OF FRONT (EAST SIDE) OF BUILDING 105 SHOWING RECESSED PORCH FRAMED BY CRISS-CROSS WOOD BALUSTRADE, STONE FACING ALONG ORIGINAL PORTION OF HOUSE FRONT, AND ORIGINAL PLANK DOOR TO PORCH BASEMENT AT LOWER PHOTO CENTER. WELDED STEEL PORCH RAILINGS VISIBLE AT PHOTO LEFT CENTER WERE ADDED IN 1972. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Worker Cottage, Rush Creek, June Lake, Mono County, CA

348

New US West-to-East Crudeline Project studied  

Microsoft Academic Search

The nine-company Grand Valley Pipeline Study Group is considering a west-to-east pipeline project which would: move crude from the Port of Long Beach, California, to Salt Lake City and other mountain refining areas; have an initial capacity of 55,000 bbl\\/day; use the Four Corners pipeline, operated by Atlantic Richfield Co., to move crude to the Pure Transportation Co. line in

Collman

1979-01-01

349

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

350

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

351

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

352

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

353

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.

354

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

355

Comparison between BCR sequential extraction and geo-accumulation method to evaluate metal mobility in sediments of Dongting Lake, Central China  

NASA Astrophysics Data System (ADS)

The form in which a metal exists strongly influences its mobility and thus, the effects on the environment. Operational methods of speciation analysis, such as the use of sequential extraction procedures, are commonly applied. The Dongting Lake, the second largest fresh-water lake in China, contains three China wetlands of international importance, the East Dongting Lake, South Dongting Lake, and West Dongting Lake. In this work, an optimized BCR sequential extraction procedure was used to assess the environmental risk of Cd, Cr, Cu, Ni, Pb and Zn in contaminated sediment of the Dongting Lake. The procedure was evaluated by using a certified reference material, BCR701. The results of the partitioning study indicated that in the lake sediments, more easily mobilized forms (acid exchangeable) were predominant for Cd, particularly in the samples from the East Dongting Lake. In contrast, the largest amount of Pb was associated with the iron and manganese oxide fractions and Cu, Zn, Cr, and Ni analyzed were mainly distributed in residual phase at an average percentage greater than 60% of the total metals. The potential risk to the lake’s water contamination was highest in the East Dongting Lake based on the calculated contamination factors. On the other hand, the total metal content was determined as well by inductively coupled plasma and mass spectrometry (ICP-MS) and assessed by using geo-accumulation index. The assessment results using geo-accumulation index were compared with the information on metal speciation. Both were correspondent with each other.

Yao, Zhigang

2008-02-01

356

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.

357

1. 728732 East Madison, southeast view of 700 block East ...  

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

1. 728-732 East Madison, southeast view of 700 block East Madison Street, 728 East Madison Street is first building on the right Hugh Foshee, Photographer, March 1980 - Phoenix Hill Historic District, 728 East Madison Street (House), Louisville, Jefferson County, KY

358

19. VIEW OF CRUDE ORE BINS FROM EAST. EAST CRUDE ...  

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

19. VIEW OF CRUDE ORE BINS FROM EAST. EAST CRUDE ORE BIN IN FOREGROUND WITH DISCHARGE TO GRIZZLY AT BOTTOM OF VIEW. CONCRETE RETAINING WALL TO LEFT (SOUTH) AND BOTTOM (EAST EDGE OF EAST BIN). - Bald Mountain Gold Mill, Nevada Gulch at head of False Bottom Creek, Lead, Lawrence County, SD

359

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.

360

Deglaciation, lake levels, and meltwater discharge in the Lake Michigan basin  

USGS Publications Warehouse

The deglacial history of the Lake Michigan basin, including discharge and routing of meltwater, is complex because of the interaction among (1) glacial retreats and re-advances in the basin (2) the timing of occupation and the isostatic adjustment of lake outlets and (3) the depositional and erosional processes that left evidence of past lake levels. In the southern part of the basin, a restricted area little affected by differential isostasy, new studies of onshore and offshore areas allow refinement of a lake-level history that has evolved over 100 years. Important new data include the recognition of two periods of influx of meltwater from Lake Agassiz into the basin and details of the highstands gleaned from sedimentological evidence. Major disagreements still persist concerning the exact timing and lake-level changes associated with the Algonquin phase, approximately 11,000 BP. A wide variety of independent data suggests that the Lake Michigan Lobe was thin, unstable, and subject to rapid advances and retreats. Consequently, lake-level changes were commonly abrupt and stable shorelines were short-lived. The long-held beliefs that the southern part of the basin was stable and separated from deformed northern areas by a hinge-line discontinuity are becoming difficult to maintain. Numerical modeling of the ice-earth system and empirical modeling of shoreline deformation are both consistent with observed shoreline tilting in the north and with the amount and pattern of modern deformation shown by lake-level gauges. New studies of subaerial lacustrine features suggest the presence of deformed shorelines higher than those originally ascribed to the supposed horizontal Glenwood level. Finally, the Lake Michigan region as a whole appears to behave in a similar manner to other areas, both local (other Great Lakes) and regional (U.S. east coast), that have experienced major isostatic changes. Detailed sedimentological and dating studies of field sites and additional development of geophysical models offer hope for reconciling the field data with our understanding of earth rheology. ?? 1995.

Colman, S. M.; Clark, J. A.; Clayton, L.; Hansel, A. K.; Larsen, C. E.

1994-01-01

361

Chemical and physical characteristics of lakes of the southeastern United States (journal version)  

SciTech Connect

A survey of the chemical status of 252 lakes, representing an estimated 2424 lakes, was conducted in the Southern Blue Ridge province and in Florida during Fall 1984. The survey was part of the Eastern Lake Survey designed to quantify the number of acidic lakes and lakes with low acid neutralizing capacity (ANC) with surface area greater than 4 ha. Of the 102 lakes sampled in the Southern Blue Ridge, none were acidic (ANC less than or equal to 0) and only 1.4% of the population of 258 lakes were estimated to have low ANC (less than or equal to 50 micro equiv/L). In contrast, an estimated 22% of the lakes in the Florida subregion were acidic, and 35.3% were estimated to have low ANC. Almost 90% of the lakes in the Southern Blue Ridge were reservoirs. These lakes generally had moderate ANC values (median = 250 micro equiv/L) and had low concentrations of aluminum, dissolved organic carbon (DOC), and sulfate compared to those of Florida, the upper Midwest, and the Northeast. The lakes in the Southern Blue Ridge showed a high degree of chemical homogeneity relative to those of other regions in the East.

Eilers, J.M.; Landers, D.H.; Brakke, D.F.

1988-01-01

362

Treatment of East Bay, Alger County, Michigan, with toxaphene for control of sea lampreys  

USGS Publications Warehouse

An experiment was conducted to determine whether toxaphene can be used to eradicate lake-dwelling sea lampreys and to determine its effect on fish populations. In East Bay, a 78-acre lake on the Sucker River, Alger County, Mich., an estimated concentration of 100 parts per billion was maintained for 14 days. The sea lamprey larvae were more resistant to toxaphene than were the fish, but a complete kill was indicated. One year after treatment, sea lampreys were absent from the lake, while the fish population had recovered.

Gaylord, William E.; Smith, Bernard R.

1966-01-01

363

MIDDLE EAST CANCER CONSORTIUM  

Cancer.gov

MIDDLE EAST CANCER CONSORTIUM 1 Cancer Registry Steering Committee Hilton Hotel Istanbul, Turkey, March 29, 2007 Joe Harford . Dr The NCI’s Vision of the MECC program :00 10 - :00 9 . A • Management and support

364

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

365

Regionalization in East Asia  

Microsoft Academic Search

Institutional regionalization has come very late to East Asia compared with Europe, but its pace has dramatically increased\\u000a since the mid-1990s. Many agreements, including bilateral ones such as those signed between Japan and Singapore, or pluri-lateral\\u000a ones such as those between ASEAN countries, cover an ever increasing number of countries of the East Asian region, including\\u000a Japan, India, and China.

Michel Fouquin

2008-01-01

366

The Middle East  

Microsoft Academic Search

The Middle East currently produces more than a fifth of the world's oil output, yet still holds two-thirds of world published proved liquid oil reserves. The first part of the book reviews the structural evolution and stratigraphic development of the Middle East region, between Pre-Cambrian-Infra Cambrian and the Cenozoic. The second part provides a country-by-country survey of producing fields, unproduced

Beydoun

1988-01-01

367

East Timor's nonviolent resistance  

Microsoft Academic Search

When people think of East Timor they usually have images of a former Portuguese backwater that glimpsed self?determination from a brief decolonization program before plunging into a full scale civil war in August 1975. The victory of Fretilin—a coalition of political interests ranging from ‘Christian democrats’ to Maoist revolutionaries, caused the other major party—the Democratic Union of East Timor (UDT),

Michael Salla

1995-01-01

368

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

369

Chronology of Lake El'gygytgyn sediments  

NASA Astrophysics Data System (ADS)

A 318 m long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El'gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chrono-stratigraphic methods. The 12 km wide lake is sited in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the Earth's magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El'gygytgyn occurred in concert with global climatic cycles. The upper ~160 m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka-1, whereas the lower 160 m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka-1.

Nowaczyk, N. R.; Haltia, E. M.; Ulbricht, D.; Wennrich, V.; Sauerbrey, M. A.; Rosén, P.; Vogel, H.; Francke, A.; Meyer-Jacob, C.; Andreev, A. A.; Lozhkin, A. V.

2013-06-01

370

River-to-lake connectivities, water renewal, and aquatic habitat diversity in the Mackenzie River Delta  

NASA Astrophysics Data System (ADS)

Past and ongoing investigations have established that lakes in the Mackenzie River Delta collectively represent gradients in water transparency, nutrient regime, and biotic communities, each strongly linked to the sill elevations of the lakes. Analysis of 40 years of water levels in East Channel of the central delta, in combination with a floodplain geometry model to estimate river water volumes added to lake waters at the annual flood peak, permitted direct estimation of annual river-to-lake connection times, lake water renewal, and interannual variabilities in nine lakes spanning the full range of sill elevations in the delta. Results have revealed a broad range of river-to-lake connectivities and river water renewals that are temporally dynamic and vary considerably among the lakes of this river delta system. Lakes with short and variable connection times plus low and variable river water renewal yield groups of lakes with high degrees of individuality because they are strongly influenced by particular sequences of antecedent years (legacy effects) that may result in lakes simultaneously containing residual waters from multiple river inundation events separated by more than a decade. Lakes with long and less varying connection times plus high river water renewal with multiple possible river water resets per year yield lakes with high degrees of similarity. The full combination of lakes arranged in an intermittently connected continuum, creating variable connectivity for aquatic organisms and water intermixing, may be an important mechanism driving the collectively distinctive habitat productivity and biodiversity of aquatic communities in this system, relative to lakes on the surrounding landscape.

Lesack, Lance F. W.; Marsh, Philip

2010-12-01

371

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

372

Paleolimnology of Lake Tubutulik, an iron-meromictic Eocene Lake, eastern Seward Peninsula, Alaska  

USGS Publications Warehouse

Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual "iron-meromictic" Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a structural graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Late Cretaceous Darby Pluton, on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the river valley of the ancestral Tubutulik River in early Eocene time. Lake Tubutulik contained a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital layers containing mostly quartz and clay minerals. Both lacustrine facies contain turbidities. The lacustrine sediments graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake apparently occupied a small deep basin in a tectonically active area of high relief. Meromixus was probably stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixus decreased as the lake became shallower from sediment filling. The source of the iron, abundant in the monimolimnion of Lake Tubutulik, was probably the Eocene basalt. Based on carbon isotope analysis of the siderite, the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature (??13C = +16.9) consistent with residual carbon formed during methanogenic fermentation. ?? 1988.

Dickinson, K. A.

1988-01-01

373

A full lipid biomarker based record from Lake Challa, Tanzania  

NASA Astrophysics Data System (ADS)

The climate of the regions surrounding the Indian Ocean - East Africa, Arabian and Indian peninsulas - is strongly dominated by the dynamics of the seasonal monsoon. To understand the long and short term driving forces behind the natural climatic variability in this region it is highly important to reconstruct climatic changes in the past and, thereby, predict future changes taking into account also anthropogenic activities. Most low latitude locations lack continuous, highly resolved continental records with good age control. From the few existing records acquired from tropical glacier ice, cave stalagmites and fossil diatoms a thorough understanding of the climatic variations reflected (rainfall and drought or temperature and its effect on precipitation) is scanty. Chemically stratified crater lakes accumulate high-quality climate-proxy records as shown in very recent studies done on the continuous and finely laminated sediment record of Lake Challa situated on the lower East slope of Mt. Kilimanjaro (Verschuren et al. 2009; Wolff et al. 2011). The unique location of this lake in equatorial East Africa implies that the climate variability is influenced by the Indian Ocean and not by the Atlantic due to the Congo Air Boundary (Thierney et al. 2011). The objective of this study is to fully explore the biomarker content of the Lake Challa sedimentary record already characterized by an excellent time resolution and chronology. Various normal chain lipids (n-alkanes, n-fatty acids, n-alcohols), sterols, long-chain diols, triterpenoids and glycolipids in sedimentary organic matter, were determined in their solvent-extractable (free) and saponification-released forms (bound). The changing composition of organic matter content from the investigated lake is used as a framework to trace palaeo-humidity, terrestrial input, algal input, temperature in sediment traps and underlying sediments of Lake Challa to further our palaeo-environmental knowledge based on GDGT's and alkanes (Sinninghe Damsté et al. 2009, 2011).

Blaga, C. I.; de Leeuw, J. W.; Verschuren, D.; Sinninghe Damsté1, J. S.

2012-04-01

374

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

375

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

376

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

377

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

378

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

379

Contrasted evolution of glacial lakes along the Hindu-Kush Himalaya mountain range between 1990 and 2009  

NASA Astrophysics Data System (ADS)

In this study, we present the first assessment of glacial lake distribution and evolution in the Hindu Kush Himalaya (HKH). Seven sites have been selected between Bhutan and Afghanistan, to capture the climatic variability along the 2000-km long mountain range. For each site, glacial lakes have been mapped with LANDSAT satellite imagery acquired in 1990, 2000 and 2009, using an automatic classification. In the East (India, Nepal and Bhutan) glacial lakes are bigger and more numerous than in the West (Pakistan, Afghanistan), and have grown continuously between 1990 and 2009 by 20% to 65%. Conversely, during the same period, the glacial lake coverage has shrunk in the Hindu Kush (-50%) and the Karakorum (-30%). This east/west pattern of lake changes seems in agreement with sparse glaciological measurements that suggest less (or even no) ice loss in the western part of the HKH.

Gardelle, J.; Yves, A.; Berthier, E.

2011-12-01

380

1. EAST SIDE/NORTH END EXTERIOR OF RUSH CREEK POWERHOUSE SHOWING ...  

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

1. EAST SIDE/NORTH END EXTERIOR OF RUSH CREEK POWERHOUSE SHOWING ROLLING METAL DOOR ON NORTH END, SWITCHRACKS NORTH OF POWERHOUSE AND WORKER COTTAGES IN COMPLEX. VIEW TO SOUTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

381

East African Rift System (EARS) Plume Structure: Insights from Quaternary Mafic Lavas of Turkana, Kenya  

Microsoft Academic Search

Quaternary mafic lavas from Lake Turkana (northern Kenya) provide information on processes operating beneath the East African Rift in an area of anomalous lithospheric and crustal thinning. Inferred depths of melting beneath Turkana (15---20km) are shal- lower than those recorded elsewhere along the rift, consistent with the anomalously thin crustal section. The mafic lavas have elevated incompatible trace element contents

TANYA FURMAN; JULIA G. BRYCE; JEFFREY KARSON; ANNAMARIA IOTTI

2004-01-01

382

The species flocks of East African cichlid fishes: recent advances in molecular phylogenetics and population genetics  

Microsoft Academic Search

With more than 3,000 species, the fish family Cichlidae is one of the most species-rich families of vertebrates. Cichlids occur in southern and central America, Africa, Madagascar, and India. The hotspot of their biodiversity is East Africa, where they form adaptive radiations composed of hundreds of endemic species in several lakes of various sizes and ages. The unparalleled species richness

Walter Salzburger; Axel Meyer

2004-01-01

383

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

384

Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada  

NASA Astrophysics Data System (ADS)

Preliminary slip rates measured across the East Pyramid Lake fault, or the Lake Range fault, help provide new estimates of extension across the Pyramid Lake basin. Multiple stratigraphic horizons spanning 48 ka were tracked throughout the lake, with layer offsets measured across all significant faults in the basin. A chronstratigraphic framework acquired from four sediment cores allows slip rates of the Lake Range and other faults to be calculated accurately. This region of the northern Walker Lake, strategically placed between the right-lateral strike-slip faults of Honey and Eagle Lakes to the north, and the normal fault bounded basins to the southwest (e.g., Tahoe, Carson), is critical in understanding the underlying structural complexity that is not only necessary for geothermal exploration, but also earthquake hazard assessment due to the proximity of the Reno-Sparks metropolitan area. In addition, our seismic CHIRP imaging with submeter resolution allows the construction of the first fault map of Pyramid Lake. The Lake Range fault can be obviously traced west of Anahoe Island extending north along the east end of the lake in numerous CHIRP lines. Initial drafts of the fault map reveal active transtension through a series of numerous, small, northwest striking, oblique-slip faults in the north end of the lake. A previously field mapped northwest striking fault near Sutcliff can be extended into the west end of Pyramid Lake. This fault map, along with the calculated slip rate of the Lake Range, and potentially multiple other faults, gives a clearer picture into understanding the geothermal potential, tectonic regime and earthquake hazards in the Pyramid Lake basin and the northern Walker Lane. These new results have also been merged with seismicity maps, along with focal mechanisms for the larger events to begin to extend our fault map in depth.

Eisses, A.; Kell, A. M.; Kent, G.; Driscoll, N. W.; Karlin, R. E.; Baskin, R. L.; Louie, J. N.; Smith, K. D.; Pullammanappallil, S.

2011-12-01

385

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

386

Temporal variation in the water chemistry of northern Victoria Land lakes (Antarctica)  

Microsoft Academic Search

.  Concentrations of major ions, silicate and nutrients (total N and P) were measured in samples of surface water from 28 lakes\\u000a in ice-free areas of northern Victoria Land (East Antarctica). Sixteen lakes were sampled during austral summers 2001\\/02,\\u000a 2003\\/04, 2004\\/05 and 2005\\/06 to assess temporal variation in water chemistry. Although samples showed a wide range in ion\\u000a concentrations, their composition

Francesca Borghini; Andrea Colacevich; Tancredi Caruso; Roberto Bargagli

2008-01-01

387

Distribution and faunal richness of Cladocera in western Uganda crater lakes  

Microsoft Academic Search

In this study, we analyse the distribution and species richness of epibenthic and planktonic Cladocera (Crustacea: Branchiopoda)\\u000a in 62 Uganda crater lakes, spread across the climatic gradient between the sub-humid shoulder and semi-arid floor of the East\\u000a African Rift Valley. Together, these lakes cover large environmental gradients in salinity, trophic conditions and depth.\\u000a In total, 36 species of Cladocera were

Bob Rumes; Hilde Eggermont; Dirk Verschuren

388

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

389

Seismic investigation of Lake Issyk-Kul, Kyrgyzstan  

NASA Astrophysics Data System (ADS)

Lake Issyk-Kul is located in an intramontane basin of the Tien Shan mountains in Kyrgyzstan, Central Asia. It has formed in a tectonically active region with W-E striking major thrust zones north and south of the lake. The lake's modern surface level is at 1607 m above sea level, maximum depth in the central basin of the lake is roughly 670 m, and the total water volume is around 1736 km3. The lake is elongated with 180 km in west-east and 60 km in south-north direction. With a surface area of 6232 km2, Lake Issyk-Kul is the second largest lake in the higher altitudes. The lake is characterized by two large delta areas at its western and eastern end, with the deltaic area being as wide as up to 60 km in the eastern and 40 km in the western part, and by steep slopes at the northern and southern shore with only a rather narrow shallower shelf area. The lake contains the sediments of the past up to several million years, and has been proposed as a future target for deep drilling within ICDP. Three seismic surveys by Russian and Belgian groups in 1982, 1997 and 2001 revealed a thick sediment infill in Lake Issyk-Kul. At both the western and the eastern end of the lake, large delta systems were formed by actual and previous inlets, namely the Tyup and Djyrgalan rivers in the eastern part of the lake (still active) and the Chu River at the western end (currently bypassing the lake). Large sub-aquatic channel systems are visible in the lake's bathymetry in the shallower part of the delta systems close to the river mouths. They were quite likely formed by these rivers during a former lake level lowstand. The delta system consists of stacked prograding delta lobes with a characteristic topset-foreset-bottomset configuration. These lobes together with sub-aerial terraces found at several spots around the lake witness lake level fluctuations of up to >400 m. The sediments in the central plain of Lake Issyk-Kul are mainly well-layered with many turbiditic sequences intercalated with pelagic background sedimentation. Sediments are slightly inclined towards south with increasing angles with depth, suggesting a halfgraben structure of the lake basin. Mass transport deposits such as debris flows are a common feature close to the steeper flanks around the central plain. The southern flank is characterized by many small terraces and several canyons that are related to the small inlets at the southern shore. The northern flank, however, shows a small, shallow shelf area of 25 to 30 m water depth. This area is characterized by glacial outwash sediments brought to the lake by small rivers that drain the large terminal moraines which are located north of the lake.

Gebhardt, C.; Naudts, L.; De Mol, L.; De Batist, M.

2012-04-01

390

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

391

Question of East Timor  

NSDL National Science Digital Library

This new site from the United Nations offers a large collection of primary documents related to the history and future of East Timor. A June 11, 1999 Security Council Resolution (1246) established the United Nations Mission in East Timor (UNAMET), which is charged with organizing and conducting a "popular consultation" (scheduled for August 8) to determine the territory's future status. At the site, users can read the full text of the agreement between Indonesia and Portugal that set the groundwork for this consultation, as well as the official UN documents concerning East Timor (reports, resolutions, discussions), press briefings and releases (1996-99). Fifteen audio reports from UN Radio are also provided, although several were unavailable at time of writing.

392

The Middle East Institute  

NSDL National Science Digital Library

Dedicated to "keeping the public objectively informed about the Middle East," the Middle East Institute provides a number of resources to this end. Visitors to the site can access the table of contents, abstracts, and some complete articles from The Middle East Journal; read online policy briefs about current events in the region; review descriptions of the Institute's published monographs; and consult an online searchable catalog of over 2,400 scholarly works in Middle Eastern studies published in the 1990s. The XML-based catalog can be searched by keyword, title, author, or any of the cataloged fields. Two online texts are also posted here: An Introduction to Islam (see the September 3, 1999 Scout Report) and, in the rare books section of the library, Mehemet the Kurd and Other Tales by Charles Wells (requires multidoc pro to view TEI (SGML)).

2001-01-01

393

Allogenic sedimentary components of Bear Lake, Utah and Idaho  

USGS Publications Warehouse

Bear Lake is a long-lived lake filling a tectonic depression between the Bear River Range to the west and the Bear River Plateau to the east, and straddling the border between Utah and Idaho. Mineralogy, elemental geochemistry, and magnetic properties provide information about variations in provenance of allogenic lithic material in last-glacial-age, quartz-rich sediment in Bear Lake. Grain-size data from the siliciclastic fraction of late-glacial to Holocene carbonate-rich sediments provide information about variations in lake level. For the quartz-rich lower unit, which was deposited while the Bear River fl owed into and out of the lake, four source areas are recognized on the basis of modern fluvial samples with contrasting properties that reflect differences in bedrock geology and in magnetite content from dust. One of these areas is underlain by hematite-rich Uinta Mountain Group rocks in the headwaters of the Bear River. Although Uinta Mountain Group rocks make up a small fraction of the catchment, hematite-rich material from this area is an important component of the lower unit. This material is interpreted to be glacial fl our. Variations in the input of glacial flour are interpreted as having caused quasi-cyclical variations in mineralogical and elemental concentrations, and in magnetic properties within the lower unit. The carbonate-rich younger unit was deposited under conditions similar to those of the modern lake, with the Bear River largely bypassing the lake. For two cores taken in more than 30 m of water, median grain sizes in this unit range from ???6 ??m to more than 30 ??m, with the coarsest grain sizes associated with beach or shallow-water deposits. Similar grain-size variations are observed as a function of water depth in the modern lake and provide the basis for interpreting the core grain-size data in terms of lake level. Copyright ?? 2009 The Geological Society of America.

Rosenbaum, J. G.; Dean, W. E.; Reynolds, R. L.; Reheis, M. C.

2009-01-01

394

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

395

Phylogenetic relationships of the lamprologine cichlid genus Lepidiolamprologus (Teleostei: Perciformes) based on mitochondrial and nuclear sequences, suggesting introgressive hybridization  

Microsoft Academic Search

Using sequences of the mitochondrial NADH dehydrogenase subunit 2 gene (ND2, 1047bp) and a segment of the non-coding mitochondrial control region, as well as nuclear sequences including two introns from the S7 ribosomal protein and the loci TmoM25, TmoM27, and UME002, we explore the phylogenetic relationships of Lepidiolamprologus, one of seven lamprologine cichlid genera in Lake Tanganyika, East Africa. Analyses

Robert Schelly; Walter Salzburger; Stephan Koblmüller; Nina Duftner; Christian Sturmbauer

2006-01-01

396

Late Cenozoic Moisture History of East Africa  

NASA Astrophysics Data System (ADS)

Lake sediments in 10 Ethiopian, Kenyan, and Tanzanian rift basins suggest that there were three humid periods at 2.7 to 2.5 million years ago (Ma), 1.9 to 1.7 Ma, and 1.1 to 0.9 Ma, superimposed on the longer-term aridification of East Africa. These humid periods correlate with increased aridity in northwest and northeast Africa and with substantial global climate transitions. These episodes could have had important impacts on the speciation and dispersal of mammals and hominins, because a number of key events, such as the origin of the genus Homo and the evolution of the species Homo erectus, took place in this region during that time.

Trauth, Martin H.; Maslin, Mark A.; Deino, Alan; Strecker, Manfred R.

2005-09-01

397

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

398

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

399

The Middle East  

SciTech Connect

The Middle East currently produces more than a fifth of the world's oil output, yet still holds two-thirds of world published proved liquid oil reserves. The first part of the book reviews the structural evolution and stratigraphic development of the Middle East region, between Pre-Cambrian-Infra Cambrian and the Cenozoic. The second part provides a country-by-country survey of producing fields, unproduced discoveries, and future reserves as well as a summary of the main producing basins and formations in the region.

Beydoun, Z.R. (American Univ., Beirut (LB))

1988-01-01

400

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

401

3. East side, details of north half of east web; ...  

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

3. East side, details of north half of east web; also details of roadway, railing and overhead bracing; looking northeast - Dodd Ford Bridge, County Road 147 Spanning Blue Earth River, Amboy, Blue Earth County, MN

402

48. AUXILIARY CHAMBER (EAST END), VIEW LOOKING EAST SHOWING ELECTRICAL ...  

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

48. AUXILIARY CHAMBER (EAST END), VIEW LOOKING EAST SHOWING ELECTRICAL PENETRATION AND AIR LOCK (LOCATION GGG) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

403

12. VIEW EAST, ROUTE 30 EAST FROM ROUTE 130 SOUTH ...  

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

12. VIEW EAST, ROUTE 30 EAST FROM ROUTE 130 SOUTH ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

404

2. VIEW SOUTHEAST, ROUTE 30 EAST FROM ROUTE 30 EAST ...  

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

2. VIEW SOUTHEAST, ROUTE 30 EAST FROM ROUTE 30 EAST ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

405

10. BUILDING: SECOND FLOOR (East Section), VIEW SOUTH: EAST, SOUTH ...  

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

10. BUILDING: SECOND FLOOR (East Section), VIEW SOUTH: EAST, SOUTH AND WEST WALLS OF COLD STORAGE, ALSO SHOWING REMNANTS OF COOLING PIPES - Boston Beer Company, 225-249 West Second Street, South Boston, Suffolk County, MA

406

Detail east panel of east truss showing rollling panels and ...  

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

Detail east panel of east truss showing rollling panels and counter weights. View south - New York, New Haven & Hartford Railroad, Fort Point Channel Rolling Lift Bridge, Spanning Fort Point Channel, Boston, Suffolk County, MA

407

Perspective view looking from the east to the east northeast ...  

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

Perspective view looking from the east to the east northeast facade, with Swiss Chalet in background, to replicate the view shown in MD-1109-J-18 - National Park Seminary, Japanese Pagoda, 2805 Linden Lane, Silver Spring, Montgomery County, MD

408

29. SECOND FLOOR EAST SIDE APARTMENT EAST BEDROOM INTERIOR. ALUMINUMFRAME ...  

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

29. SECOND FLOOR EAST SIDE APARTMENT EAST BEDROOM INTERIOR. ALUMINUM-FRAME SLIDING-GLASS WINDOWS ARE REPLACEMENTS. VIEW TO NORTHEAST. - Lee Vining Creek Hydroelectric System, Triplex Cottage, Lee Vining Creek, Lee Vining, Mono County, CA

409

35. EAST FRONT OF POWERHOUSE AND CAR BARN: East front ...  

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

35. EAST FRONT OF POWERHOUSE AND CAR BARN: East front of powerhouse and car barn. 'Annex' is right end of building. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

410

East wing. Elevation of east side along Presidio Avenue, as ...  

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

East wing. Elevation of east side along Presidio Avenue, as seen from the rooftop of the Laurel Inn across the street. - Jewish Community Center of San Francisco, 3200 California Street, San Francisco, San Francisco County, CA

411

Record of Late Pleistocene Glaciation and Deglaciation in the Southern Cascade Range. II. Flux of Glacial Flour in a Sediment Core from Upper Klamath Lake, Oregon  

Microsoft Academic Search

During the late Wisconsin, glacial flour from alpine glaciers along the east side of the Cascade Range in southern Oregon was deposited in Upper Klamath Lake. Quantitative interpretation of magnetic properties and grain-size data of cored sediments from Caledonia Marsh on the west side of the lake provides a continuous record of the flux of glacial flour spanning the last

Joseph G. Rosenbaum; Richard L. Reynolds

2004-01-01

412

High crystalline quality of large single crystals of subglacial ice above Lake Vostok (Antarctica) revealed by hard X-ray diffraction  

Microsoft Academic Search

X-ray diffraction experiments carried out on large single crystals from accreted ice above Lake Vostok, a subglacial lake lying beneath the East Antarctic ice sheet, revealed a surprisingly very low lattice distortion. This crystalline quality does not seem to be affected by impurities. Chloride and sodium appear to be homogeneously distributed in the ice lattice in spite of their relatively

Maurine Montagnat; Paul Duval; P. Bastie; B. Hamelin; M. de Angelis; J. R. Petit; V. Ya Lipenkov

2003-01-01

413

Active high-resolution seismic tomography of compressional wave velocity and attenuation structure at Medicine Lake volcano, northern California Cascade Range  

Microsoft Academic Search

We determine compressional wave velocity and attenuation structures for the upper crust beneath Medicine Lake volcano in northeast California using a high-resolution active source seismic tomography method. Medicine Lake volcano is a basalt through rhyolite shield volcano of the Cascade Range, lying east of the range axis. The Pg wave from eight explosive sources which has traveled upward through the

John R. Evans; John J. Zucca

1988-01-01

414

Earthquake simulations in the Salt Lake Basin for the validation of the Wasatch CVM: long period (T>1.0-s) seismic response  

Microsoft Academic Search

The Wasatch Fault bounds the Salt Lake Basin (SLB), Utah to the east and is capable of producing M7 earthquakes. In order to characterize the seismic hazard that such earthquakes pose to Salt Lake City and other heavily populated regions along the Wasatch Front, we require estimates of potential earthquake ground motions. However, the long recurrence time of these events

M. P. Moschetti; L. Ramirez-Guzman

2010-01-01

415

Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 yr  

NASA Astrophysics Data System (ADS)

Equatorial East Africa has a complex, regional patchwork of climate regimes, with multiple interacting drivers. Recent studies have focussed on large lakes and reveal signals that are smoothed in both space and time, and, whilst useful at a continental scale, are of less relevance when understanding short-term, abrupt or immediate impacts of climate and environmental changes. Smaller-scale studies have highlighted spatial complexity and regional heterogeneity of tropical palaeoenvironments in terms of responses to climatic forcing (e.g. the Little Ice Age [LIA]) and questions remain over the spatial extent and synchroneity of climatic changes seen in East African records. Sediment cores from paired crater lakes in western Uganda were examined to assess ecosystem response to long-term climate and environmental change as well as testing responses to multiple drivers using redundancy analysis. These archives provide annual to sub-decadal records of environmental change. The records from the two lakes demonstrate an individualistic response to external (e.g. climatic) drivers, however, some of the broader patterns observed across East Africa suggest that the lakes are indeed sensitive to climatic perturbations such as a dry Mediaeval Climate Anomaly (MCA; 1000-1200 AD) and a relatively drier climate during the main phase of the LIA (1500-1800 AD); though lake levels in western Uganda do fluctuate. The relationship of Ugandan lakes to regional climate drivers breaks down c. 1800 AD, when major changes in the ecosystems appear to be a response to sediment and nutrient influxes as a result of increasing cultural impacts within the lake catchments. The data highlight the complexity of individual lake response to climate forcing, indicating shifting drivers through time. This research also highlights the importance of using multi-lake studies within a landscape to allow for rigorous testing of climate reconstructions, forcing and ecosystem response.

Mills, K.; Ryves, D. B.; Anderson, N. J.; Bryant, C. L.; Tyler, J. J.

2013-09-01

416

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

417

Reduced interannual rainfall variability in East Africa during the last ice age.  

PubMed

Interannual rainfall variations in equatorial East Africa are tightly linked to the El Niño Southern Oscillation (ENSO), with more rain and flooding during El Niño and droughts in La Niña years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall. PMID:21817050

Wolff, Christian; Haug, Gerald H; Timmermann, Axel; Sinninghe Damsté, Jaap S; Brauer, Achim; Sigman, Daniel M; Cane, Mark A; Verschuren, Dirk

2011-08-01

418

20. View of south side of East Ward Street east ...  

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

20. View of south side of East Ward Street east of South McDonald Avenue, facing southeast. - Gaskin Avenue Neighborhood, Bounded by Dart Street to east, CSX Railroad to south, Pearl & Madison Avenues to west, & Wilson & Gordon Streets to north, Douglas, Coffee County, GA

419

7. View of south side of East Ward Street east ...  

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

7. View of south side of East Ward Street east of South Coweta Avenue, facing southwest. - Gaskin Avenue Neighborhood, Bounded by Dart Street to east, CSX Railroad to south, Pearl & Madison Avenues to west, & Wilson & Gordon Streets to north, Douglas, Coffee County, GA

420

17. View of north side of East Ward Street east ...  

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

17. View of north side of East Ward Street east of North McDonald Avenue, facing northwest. - Gaskin Avenue Neighborhood, Bounded by Dart Street to east, CSX Railroad to south, Pearl & Madison Avenues to west, & Wilson & Gordon Streets to north, Douglas, Coffee County, GA

421

2. View of north side of East Ward Street east ...  

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

2. View of north side of East Ward Street east of North Coweta Avenue, facing northeast. - Gaskin Avenue Neighborhood, Bounded by Dart Street to east, CSX Railroad to south, Pearl & Madison Avenues to west, & Wilson & Gordon Streets to north, Douglas, Coffee County, GA

422

13. View of south side of East Ward Street east ...  

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

13. View of south side of East Ward Street east of Sibett Avenue, facing southwest. - Gaskin Avenue Neighborhood, Bounded by Dart Street to east, CSX Railroad to south, Pearl & Madison Avenues to west, & Wilson & Gordon Streets to north, Douglas, Coffee County, GA

423

50. View looking east. East bay is on the left. ...  

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

50. View looking east. East bay is on the left. The dismantling of the last crib. Note the identifying tags nailed to the crib sidewalls. Foundation timbers and the outline of the crib structure are visible in the foreground. - Wabash & Erie Canal, Lock No. 2, 8 miles east of Fort Wayne, adjacent to U.S. Route 24, New Haven, Allen County, IN

424

Understanding the Middle East.  

ERIC Educational Resources Information Center

|This nine-week unit on the Middle East for sixth graders was developed as part of a series by the Public Education Religion Studies Center at Wright State University. A major objective is to help students understand and appreciate sacred times and sacred places within this cultural setting. They learn how beliefs and practices cause the people to…

Owen, Evelyn C.

425

Intellectuals east and west  

Microsoft Academic Search

S the controversies sparked by a recent book by Paul Johnson (Intellectuals) indicate, the essential attributes and proper public roles of intellectuals remain in dispute. A comparison of intellectuals in the East and West may help to settle some of these matters and shed more light on the key characteristics of this group as they appear in somewhat different incarnations

Paul Hollander

1990-01-01

426

East Texas Storytellers.  

ERIC Educational Resources Information Center

Written and published by the students at Gary High School, Gary, Texas, "Loblolly Magazine" is published twice a year. Issues are frequently devoted to a distant theme. The theme of this issue, "East Texas Storytellers," attempts to capture some of the local color and regional history of eastern Texas. The first article, "Timothy Griffith, Master…

Anderson, Brandi, Ed.

1987-01-01

427

Understanding the Middle East.  

ERIC Educational Resources Information Center

This nine-week unit on the Middle East for sixth graders was developed as part of a series by the Public Education Religion Studies Center at Wright State University. A major objective is to help students understand and appreciate sacred times and sacred places within this cultural setting. They learn how beliefs and practices cause the people to…

Owen, Evelyn C.

428

East Texas Quilts.  

ERIC Educational Resources Information Center

Patchwork quilting is an original folk art in the United States. Pilgrims first used worn out scraps of cloth to make bed covers in an age of scarcity. Featured here are stories on East Texas Quilts, their origins, the love and hard work which goes into the making of a quilt (Ira Barr and others). The techniques needed to construct a quilt are…

Whiteside, Karen, Ed.

1986-01-01

429

Test Well, East River  

USGS Multimedia Gallery

USGS test well 10 34h363 in the East River, Brunswick, Ga. The U.S. Geological Survey drilled this test well in the early 1970's and at the time it was on the edge of the marsh at Andrews Island. It is now only accessible by boat or canoe at high tide. Despite being surrounded by saltwater the artes...

2008-12-04

430

Source parameters of the 1980 Mammoth Lakes, California earthquake sequence  

Microsoft Academic Search

From the more than 1500 Mammoth Lakes earthquakes recorded on three-component digital seismographs (Spudich et al., 1981), 150 were used in an analysis of the locations, mechanism, and source parameters. A composite fault plane solution of nine earthquakes 3.9?M?5.1 defines a right-lateral strike slip mechanism on a steeply dipping nearly east-west plane striking S75°E or left-lateral strike slip on a

Ralph J. Archuleta; Edward Cranswick; Charles Muller; Paul Spudich

1982-01-01

431

Sexual selection and speciation: mechanisms in Lake Victoria cichlid fish  

Microsoft Academic Search

The several hundred species of cichlid fish endemic to Lake Victoria (East-Africa) are textbook examples of explosive speciation. This thesis evaluates the hypothesis that sexual selection by female mate choice has contributed to this process of divergence, by investigating the mechanisms that drive the evolution and divergence of mating preferences for colour patterns. \\u000aI studied two representative model systems, the

Martine Elisabeth Maan

2006-01-01

432

The late holocene palaeoenvironment in the Lake Njupi area, west Cameroon: implications regarding the history of Lake Nyos  

NASA Astrophysics Data System (ADS)

Lake Njupi, 1 km east of Lake Nyos, on the Cameroon Volcanic Line, was formed by the damming of a local crustal depression. Two cores from Lake Nyos were analysed which penetrated sediments at the margin of the lake. The older deposits give an age of 3400 years BP and this date is proposed as a minimum age for Lake Njupi. Sedimentological, palynological and geochemical studies of a 2 m section provide an opportunity to reconstruct the Late Holocene environmental history. It is an organic-rich deposit (organic carbon up to 30%) with an abundant Silicospongia spicules fraction. An obvious sedimentary homogeneity is interrupted by 5 fine to coarse layers with sandy quartz and lignitic remains. Such inputs were denoted by carbohydrate maxima or sometimes by phenolic compounds. This study confirms the evidence of an arid period culminating between 2500 and 2000 yrs BP. This crisis began around 3000 yrs BP in the rain forest area of West Cameroon and also further to the south in Congo. Lake Njupi, situated today in a mostly grassland savanna environment known as the "Grass Fields", provides evidence for environmental changes from a mosaic of forest and savanna before 2500 years BP to a savanna characterised by high grass pollen contents (75 to 85%), with small islands of forest. The mountain vegetation characterised by Podocarpus and Olea capensis retreated around 2300 years BP at the time Elaeis guineensis (the Oil Palm) began its extension as a pioneer tree, later providing opportunities for its domestication by man.

Zogning, Appolinaire; Giresse, Pierre; Maley, Jean; Gadel, François

1997-04-01

433

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

434

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

435

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

436

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

437

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

438

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

439

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

440

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.

441

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

442

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

443

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

444

Association between winter precipitation and water level fluctuations in the Great Lakes and atmospheric circulation patterns  

SciTech Connect

Atmospheric precipitation in the Great Lakes basin, as a major mediating variable between atmospheric circulation and lake levels, is analyzed relative to both. The effect of cumulative winter precipitation on lake levels varies from lake to lake and depends on both the state of the lake level itself and air temperature. For periods with a quasi-stable temperature regime, the correlation coefficient between winter precipitation and changes in lake levels from November to spring months reaches 0.8. An analysis of composite maps of mean winter 700-mb heights and sea level pressure for the years with well-above and well-below normal precipitation in the lower Great Lakes basin (Lakes Michigan-Huron, St. Clair, Erie, and Ontario) has shown that changes in precipitation are associated with the wave train structure in the lower and midtroposphere that is similar to the Pacific/North American (PNA) teleconnection pattern. During the positive phase of the PNA-like pattern, when the upper-atmospheric ridge/trough system is amplified, cyclones passing over the Great Lakes basin are frequently of Alberta (Canada) origin and carry relatively small amounts of precipitation. As a result, lake levels tend to decline. On the contrary, during the negative phase of the pattern when the atmospheric circulation is more zonal, the main storm track is oriented from the southwest to the northeast and cyclones bring enough precipitation to induce a rise in lake levels. The effect of the position of the upper-atmospheric trough over the east coast of North America on the precipitation regime in the Great Lakes basin is also demonstrated. 42 refs., 11 figs., 4 tabs.

Rodionov, S.N. [National Center for Atmospheric Research, Boulder, CO (United States)

1994-11-01

445

Arctic lake ontogeny across multiple interglaciations  

NASA Astrophysics Data System (ADS)

Few lakes in the Arctic preserve sediments older than Holocene age because of pervasive glacial scour during the last ice age. Here we present sediment diatom and geochemical records from a lake on east-central Baffin Island (CF8, Nunavut, Canada) that captures three successive interglacial periods within the last 200,000 years: a portion of