Science.gov

Sample records for lake bracciano central

  1. Competing invaders: Performance of two Anguillicola species in Lake Bracciano

    PubMed Central

    Dangel, K.C.; Keppel, M.; Le, T.T.Y.; Grabner, D.; Sures, B.

    2015-01-01

    Anguillicola crassus is one of the most successful parasitic invasive species as it has spread from its original habitat in East Asia throughout the world and has acquired five new eel host species in the course of its invasion within the last three decades. Records from an Italian lake indicate that this species has even displaced an established population of its close relative A. novaezelandiae originating from New Zealand. In order to analyze the reasons for its high invasive potential, this review highlights recent studies, which substantiate the selective advantages of A. crassus over A. novaezelandiae. Laboratory infection experiments revealed that A. crassus features a less synchronized development compared to A. novaezelandiae in the European eel, which enables this species to emit eggs over a longer period of time. Differences in the time period required for first egg output and in the maturation process of second stage larvae in intermediate hosts could also be detected, which may lead to differences in infection potential. Finally, microsatellite analyses have shown that hybridization processes are possible, but might only occur between A. crassus males and A. novaezelandiae females. Taken as a whole, the sum of minor selective advantages and differences in life cycle traits could have considerably contributed to a replacement of one species by the other. PMID:25830111

  2. Geology of central Lake Michigan.

    USGS Publications Warehouse

    Wood, R.J.; Paull, R.A.; Wolosin, C.A.; Friedel, R.J.

    1981-01-01

    The geology beneath central Lake Michigan is interpreted from a synthesis of 1,700 km of continuous seismic reflection profile data, bathymetry, grab samples, and onshore surface and subsurface information. The map of unconsolidated sediment (primarily Pleistocene) shows thicknesses ranging from 180 m in a steep- walled, northeast-trending valley to less than 10 m over a mid-lake topographic high. These are the dominant features developed on the gently eastward-dipping Paleozoic rocks along this part of the western flank of the Michigan basin. Two structural-stratigraphic cross sections of the study area were constructed. The cross sections, grab samples and other information were used to construct a Paleozoic geologic map. Speculations are made about the petroleum potential beneath Lake Michigan. -from Authors

  3. Geology of central Lake Michigan

    SciTech Connect

    Wold, R.J.; Paull, R.A.; Wolosin, C.A.; Friedel, R.J.

    1981-09-01

    The geology beneath Lake Michigan between 43/sup 0/00' and 44/sup 0/00'N and between 86/sup 0/30' and 87/sup 0/40' W is interpreted from a synthesis of 1,700 km of continuous seismic reflection profile data, bathymetry, grab samples, and onshore surface and subsurface information. The continuous seismic reflection profiles and bathymetry provided information for maps of unconsolidated sediment thickness and Paleozoic bedrock topography. Two structural-stratigraphic cross sections of the study area were constructed by utilizing a composite subsurface-surface section for eastern Wisconsin and two control wells in western Michigan. The cross sections, grab samples previously described in the literature, the bedrock topographic map, and published maps were used to construct a Paleozoic geologic map for central Lake Michigan. Rocks from Middle Silurian through Early Mississippian age form subcrops beneath the study area, whereas rocks of Early Silurian, Ordovician, and Late Cambrian age are present at greater depth. The Upper Cambrian rocks unconformably overlie Precambrian igneous and metamorphic rocks. The structural-stratigraphic cross sections also allow speculation about the petroleum potential beneath Lake Michigan. The possibility of oil occurrences within the Silurian is enhanced by major east-west facies changes, and other horizons with promise are present in Devonian and Ordovician rocks. Although Michigan and Wisconsin laws currently prohibit petroleum exploration in Lake Michigan, it is an area with future potential.

  4. Hydrology of Central Florida Lakes - A Primer

    USGS Publications Warehouse

    Schiffer, Donna M.

    1998-01-01

    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

  5. Lake whitefish and lake herring population structure and niche in ten south-central Ontario lakes

    USGS Publications Warehouse

    Carl, Leon M.; McGuiness, Fiona

    2006-01-01

    This study compares simple fish communities of ten oligotrophic lakes in south-central Ontario. Species densities and population size structure vary significantly among these lake communities depending on fish species present beyond the littoral zone. Lake whitefish are fewer and larger in the presence of lake herring than in their absence. Diet analysis indicates that lake whitefish shift from feeding on both plankton and benthic prey when lake herring are absent to a primarily benthic feeding niche in the presence of lake herring. When benthic round whitefish are present, lake whitefish size and density decline and they move lower in the lake compared to round whitefish. Burbot are also fewer and larger in lakes with lake herring than in lakes without herring. Burbot, in turn, appear to influence the population structure of benthic coregonine species. Lower densities of benthic lake whitefish and round whitefish are found in lakes containing large benthic burbot than in lakes with either small burbot or where burbot are absent. Predation on the pelagic larvae of burbot and lake whitefish by planktivorous lake herring alters the size and age structure of these populations. As life history theory predicts, those species with poor larval survival appear to adopt a bet-hedging life history strategy of long-lived individuals as a reproductive reserve.

  6. Microplastic pollution in lakes and lake shoreline sediments - A case study on Lake Bolsena and Lake Chiusi (central Italy).

    PubMed

    Fischer, Elke Kerstin; Paglialonga, Lisa; Czech, Elisa; Tamminga, Matthias

    2016-06-01

    Rivers and effluents have been identified as major pathways for microplastics of terrestrial sources. Moreover, lakes of different dimensions and even in remote locations contain microplastics in striking abundances. This study investigates concentrations of microplastic particles at two lakes in central Italy (Lake Bolsena, Lake Chiusi). A total number of six Manta Trawls have been carried out, two of them one day after heavy winds occurred on Lake Bolsena showing effects on particle distribution of fragments and fibers of varying size categories. Additionally, 36 sediment samples from lakeshores were analyzed for microplastic content. In the surface waters 2.68 to 3.36 particles/m(3) (Lake Chiusi) and 0.82 to 4.42 particles/m(3) (Lake Bolsena) were detected, respectively. Main differences between the lakes are attributed to lake characteristics such as surface and catchment area, depth and the presence of local wind patterns and tide range at Lake Bolsena. An event of heavy winds and moderate rainfall prior to one sampling led to an increase of concentrations at Lake Bolsena which is most probable related to lateral land-based and sewage effluent inputs. The abundances of microplastic particles in sediments vary from mean values of 112 (Lake Bolsena) to 234 particles/kg dry weight (Lake Chiusi). Lake Chiusi results reveal elevated fiber concentrations compared to those of Lake Bolsena what might be a result of higher organic content and a shift in grain size distribution towards the silt and clay fraction at the shallow and highly eutrophic Lake Chiusi. The distribution of particles along different beach levels revealed no significant differences. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Geological Character and Mineral Resources of South Central Lake Erie.

    DTIC Science & Technology

    1982-10-01

    AD-A123 085 GEOLOGICAL CHARACTERAND MINERAL RESOURCES OF SOUTH 1/ CENTRAL LAKE ERIE(U) COASTAL ENGINEERING RESEARCH CENT ER FORT E LVOIR VA S d...CHART NATMOAL BUREAU Of STANDARDS-1963-A 1.1 lilt. AR MR 82-9 Geological Character and Mineral Resources of South Central Lake Erie by S. Jeff ress...GEOLOGICAL CHARACTER AND MINERAL RESOURCES Miscellaneous Report OF SOUTH CENTRAL LAKE ERIE 6. PERFORMING ORG. REPORT NUMBER 7. AUTHORI’.) S. CONTRACT

  8. Sedimentary Feature in Lake Terkhiin Tsagaan and Lake Ugii, Central Mongolia

    NASA Astrophysics Data System (ADS)

    Orkhonselenge, Alexander; Davaagatan, Tuyagerel

    2016-04-01

    We present characteristics of lacustrine sediments recorded from Lake Terkhiin Tsagaan and Lake Ugii at near latitudes in Central Mongolia. Physical-chemical properties of eight core sediments collected from these lakes show impact of different montane and prairie landscapes on the lacustrine sediments. Lake Terkhiin Tsagaan indicating a montane landscape with higher contents of organic matter and biogenic silica, and finer sediments differs from Lake Ugii reflecting a prairie landscape with higher contents of carbonates and minerals, and coarser sediments. Stratigraphical sequences of the lacustrine sediments recommend that these two lakes have experienced a numerous of environmental conditions during the arid mid Holocene and humid late Holocene reconstructed from the adjacent lakes in Central Mongolia. These Holocene climatic changes inferred from dramatic fluctuations in temperature and precipitation might have been responsible for the identical environmental conditions, resulting in the sedimentary feature in Lake Terkhiin Tsagaan and Lake Ugii. More investigations with precise dating are thus needed from the both lakes for determining lacustrine sedimentations and reconstructing paleoenvironmental changes in Central Mongolia.

  9. Bacterial Communities of Three Saline Meromictic Lakes in Central Asia

    PubMed Central

    Baatar, Bayanmunkh; Chiang, Pei-Wen; Rogozin, Denis Yu; Wu, Yu-Ting; Tseng, Ching-Hung; Yang, Cheng-Yu; Chiu, Hsiu-Hui; Oyuntsetseg, Bolormaa; Degermendzhy, Andrey G.; Tang, Sen-Lin

    2016-01-01

    Meromictic lakes located in landlocked steppes of central Asia (~2500 km inland) have unique geophysiochemical characteristics compared to other meromictic lakes. To characterize their bacteria and elucidate relationships between those bacteria and surrounding environments, water samples were collected from three saline meromictic lakes (Lakes Shira, Shunet and Oigon) in the border between Siberia and the West Mongolia, near the center of Asia. Based on in-depth tag pyrosequencing, bacterial communities were highly variable and dissimilar among lakes and between oxic and anoxic layers within individual lakes. Proteobacteria, Bacteroidetes, Cyanobacteria, Actinobacteria and Firmicutes were the most abundant phyla, whereas three genera of purple sulfur bacteria (a novel genus, Thiocapsa and Halochromatium) were predominant bacterial components in the anoxic layer of Lake Shira (~20.6% of relative abundance), Lake Shunet (~27.1%) and Lake Oigon (~9.25%), respectively. However, few known green sulfur bacteria were detected. Notably, 3.94% of all sequencing reads were classified into 19 candidate divisions, which was especially high (23.12%) in the anoxic layer of Lake Shunet. Furthermore, several hydro-parameters (temperature, pH, dissolved oxygen, H2S and salinity) were associated (P< 0.05) with variations in dominant bacterial groups. In conclusion, based on highly variable bacterial composition in water layers or lakes, we inferred that the meromictic ecosystem was characterized by high diversity and heterogenous niches. PMID:26934492

  10. Bacterial Communities of Three Saline Meromictic Lakes in Central Asia.

    PubMed

    Baatar, Bayanmunkh; Chiang, Pei-Wen; Rogozin, Denis Yu; Wu, Yu-Ting; Tseng, Ching-Hung; Yang, Cheng-Yu; Chiu, Hsiu-Hui; Oyuntsetseg, Bolormaa; Degermendzhy, Andrey G; Tang, Sen-Lin

    2016-01-01

    Meromictic lakes located in landlocked steppes of central Asia (~2500 km inland) have unique geophysiochemical characteristics compared to other meromictic lakes. To characterize their bacteria and elucidate relationships between those bacteria and surrounding environments, water samples were collected from three saline meromictic lakes (Lakes Shira, Shunet and Oigon) in the border between Siberia and the West Mongolia, near the center of Asia. Based on in-depth tag pyrosequencing, bacterial communities were highly variable and dissimilar among lakes and between oxic and anoxic layers within individual lakes. Proteobacteria, Bacteroidetes, Cyanobacteria, Actinobacteria and Firmicutes were the most abundant phyla, whereas three genera of purple sulfur bacteria (a novel genus, Thiocapsa and Halochromatium) were predominant bacterial components in the anoxic layer of Lake Shira (~20.6% of relative abundance), Lake Shunet (~27.1%) and Lake Oigon (~9.25%), respectively. However, few known green sulfur bacteria were detected. Notably, 3.94% of all sequencing reads were classified into 19 candidate divisions, which was especially high (23.12%) in the anoxic layer of Lake Shunet. Furthermore, several hydro-parameters (temperature, pH, dissolved oxygen, H2S and salinity) were associated (P< 0.05) with variations in dominant bacterial groups. In conclusion, based on highly variable bacterial composition in water layers or lakes, we inferred that the meromictic ecosystem was characterized by high diversity and heterogenous niches.

  11. Water quality of Belton Lake, central Texas

    USGS Publications Warehouse

    Mendieta, H.B.; Pate, Dale L.

    1982-01-01

    The maximum concentrations of chlorinated hydrocarbon insecticides or their degradation products detected in bottom sediments collected from the lake during four lake surveys included 1.1 micrograms per kilogram of DDT, 3.0 micrograms per kilogram of DDD, 11 micrograms per kilogram of DDE, and 2 micrograms per kilogram of chlordane.

  12. Internal loading of phosphate in Lake Erie Central Basin.

    PubMed

    Paytan, Adina; Roberts, Kathryn; Watson, Sue; Peek, Sara; Chuang, Pei-Chuan; Defforey, Delphine; Kendall, Carol

    2017-02-01

    After significant reductions in external phosphorus (P) loads, and subsequent water quality improvements in the early 1980s, the water quality of Lake Erie has declined considerably over the past decade. The frequency and magnitude of harmful algal blooms (primarily in the western basin) and the extent of hypoxic bottom waters in the central basin have increased. The decline in ecosystem health, despite meeting goals for external P loads, has sparked a renewed effort to understand P cycling in the lake. We use pore-water P concentration profiles and sediment cores incubation experiments to quantify the P flux from Lake Erie central basin sediments. In addition, the oxygen isotopes of phosphate were investigated to assess the isotopic signature of sedimentary phosphate inputs relative to the isotopic signature of phosphate in lake water. Extrapolating the total P sediment flux based on the pore-water profiles to the whole area of the central basin ranged from 300 to 1250metric tons per year and using the flux based on core incubation experiments an annual flux of roughly 2400metric tons of P is calculated. These estimates amount to 8-20% of the total external input of P to Lake Erie. The isotopic signature of phosphate in the extractable fraction of the sediments (~18‰) can explain the non-equilibrium isotope values of dissolved phosphate in the deep water of the central basin of Lake Erie, and this is consistent with sediments as an important internal source of P in the Lake.

  13. Geology and evolution of lakes in north-central Florida

    USGS Publications Warehouse

    Kindinger, J.L.; Davis, J.B.; Flocks, J.G.

    1999-01-01

    Fluid exchange between surficial waters and groundwater in karst environments, and the processes that control exchange, are of critical concern to water management districts and planners. High-resolution seismic data were collected from 30 lakes of north-central Florida. In each case study, lake structure and geomorphology were controlled by solution and/or mechanical processes. Processes that control lake development are twofold: (1) karstification or dissolution of the underlying limestone, and (2) the collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone. Case studies have shown that lakes can be divided by geomorphic types into progressive developmental phases: (1) active subsidence or collapse phase (young); (2) transitional phase (middle age); (3) baselevel phase (mature); and (4) polje (drowned prairie) - broad flat-bottom that have one or all phases of sinkhole. Using these criteria, Florida lakes can be classified by size, fill, subsurface features, and geomorphology.Fluid exchange between surficial waters and groundwater in karst environments, and the processes that control exchange, are of critical concern to water management districts and planners. High-resolution seismic data were collected from 30 lakes of north-central Florida. In each case study, lake structure and geomorphology were controlled by solution and/or mechanical processes. Processes that control lake development are twofold: (1) karstification or dissolution of the underlying limestone, and (2) the collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone. Case studies have shown that lakes can be divided by geomorphic types into progressive developmental phased: (1) active subsidence or collapse phase (young); (2) transitional phase (middle age); (3) baselevel phase

  14. The hydrology of Lake Rousseau, west-central Florida

    USGS Publications Warehouse

    German, E.R.

    1978-01-01

    Lake Rousseau, about 4 miles southwest of Inglis, Florida, was formed in 1909 by impoundment of the Withlacooche River by Inglis Dam, west of Dunnellon, Florida. The lake was to have been part of the Cross-Florida Barge Canal; a lock and channel associated with the presently inactive project were completed in 1969. Lake Rousseau is about 11 miles long, covers about 4,000 acres, and contains about 34,000 acre-feet of water at the normal pool elevation of 27.5 feet above mean sea level. Inflow to the lake is relatively constant and responds slowly to rainfall. The estimated 100-year peak inflow, 10,400 cubic feet per second, is only 19 percent higher than the 100-year high monthly inflow. Water in Lake Rousseau is a calcium-bicarbonate type and is hard. Mean total phosphorus and organic nitrogen concentrations are considerably lower in Lake Rousseau than in north-central Florida lakes which have been considered to be eutrophic by other investigators, however, the lake supports of prolific aquatic plant community. Dissolved-oxygen concentrations near the water surface are occasionally less than 3 mg/liter. (Woodard-USGS)

  15. Bathymetry of Walker Lake, West-Central Nevada

    USGS Publications Warehouse

    Lopes, Thomas J.; Smith, J. LaRue

    2007-01-01

    Walker Lake lies within a topographically closed basin in west-central Nevada and is the terminus of the Walker River. Much of the streamflow in the Walker River is diverted for irrigation, which has contributed to a decline in lake-surface altitude of about 150 feet and an increase in dissolved solids from 2,500 to 16,000 milligrams per liter in Walker Lake since 1882. The increase in salinity threatens the fresh-water ecosystem and survival of the Lahontan cutthroat trout, a species listed as threatened under the Endangered Species Act. Accurately determining the bathymetry and relations between lake-surface altitude, surface area, and storage volume are part of a study to improve the water budget for Walker Lake. This report describes the updated bathymetry of Walker Lake, a comparison of results from this study and a study by Rush in 1970, and an estimate of the 1882 lake-surface altitude. Bathymetry was measured using a single-beam echosounder coupled to a differentially-corrected global positioning system. Lake depth was subtracted from the lake-surface altitude to calculate the altitude of the lake bottom. A Lidar (light detection and ranging) survey and high resolution aerial imagery were used to create digital elevation models around Walker Lake. The altitude of the lake bottom and digital elevation models were merged together to create a single map showing land-surface altitude contours delineating areas that are currently or that were submerged by Walker Lake. Surface area and storage volume for lake-surface altitudes of 3,851.5-4,120 feet were calculated with 3-D surface-analysis software. Walker Lake is oval shaped with a north-south trending long axis. On June 28, 2005, the lake-surface altitude was 3,935.6 feet, maximum depth was 86.3 feet, and the surface area was 32,190 acres. The minimum altitude of the lake bottom from discrete point depths is 3,849.3 feet near the center of Walker Lake. The lake bottom is remarkably smooth except for mounds near

  16. Late Pleistocene and Holocene Paleoenvironments of Chalco Lake, Central Mexico

    NASA Astrophysics Data System (ADS)

    Lozano-García, Maria Socorro; Ortega-Guerrero, Beatriz; Caballero-Miranda, Margarita; Urrutia-Fucugauchi, Jaime

    1993-11-01

    In order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record.

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

    NASA Astrophysics Data System (ADS)

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

    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 km 2 (09/1995) and 25 km 2 (08/1979). Above average rainfall was responsible for the extreme lake size in May 1997 (104 km 2). 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.

  18. Geophysical studies of Mono Lake, east-central California

    NASA Astrophysics Data System (ADS)

    Athens, N. D.; Ponce, D. A.

    2012-12-01

    Magnetic and gravity investigations were undertaken in Mono Lake, California to study regional crustal structures and to aid understanding the geologic framework of Mono Lake, in particular regarding potential geothermal resources and volcanic hazards throughout Mono Basin. Recent geophysical surveys included over 600 line-kilometers of high-resolution ship-borne magnetometer data that augmented existing airborne data, 22 line-kilometers of ground magnetic data that were collected along six traverses across Paoha Island, 56 gravity stations that were collected on Paoha and Negit Islands, and 28 rock samples that were collected for physical property data. Magnetic highs in the study area occur to the east and west of Mono Lake, where pre-Tertiary basement is exposed. Magnetic data indicate that Mono Lake itself is dominated by three prominent magnetic anomalies that are from west to east: a magnetic high along the northwest part of the lake associated with the moderately magnetic basalt cinder cone at Black Point, a magnetic high associated with the young volcanic centers at Paoha and Negit Islands, and a broad magnetic high along the eastern margin of the lake probably associated with moderately magnetic granitic basement rocks at depth. Because volcanic rocks exposed at the surface of Paoha and Negit Islands are only weakly magnetic, magnetic data suggest that more mafic volcanic rocks probably occur at depth and are the source of the anomaly. The linear and steep magnetic gradient across the eastern part of the lake may reflect a fault. A fault may also be imaged in the northeastern part of the lake, where a possible laterally offset magnetic anomaly may be present. Within Mono Lake, gravity station control is poor because land-based gravity stations are limited to Paoha and Negit Islands. The gravity low in the basin reflects a moderately deep sedimentary basin filled with low density lacustrine and volcanic deposits. Isostatic gravity data indicate the central

  19. Sustainable management of Mogan and Eymir Lakes in Central Turkey

    NASA Astrophysics Data System (ADS)

    Yagbasan, Ozlem; Yazicigil, Hasan

    2009-01-01

    Mogan and Eymir Lakes, located 20 km south of Ankara in Central Turkey, are important aesthetic, recreational, and ecological resources. Dikilitas and Ikizce reservoirs, constructed on upstream surface waters, are two man-made structures in the basin encompassing an area of 985 km2. The purpose of this study is to quantify groundwater components in lakes’ budgets and to assess the potential impacts of upstream reservoirs on lake levels for sustainable management of the system. Available data have been used to develop a conceptual model of the system. A three-dimensional groundwater model, incorporating a lake component, has been developed for the system. The model has been calibrated successfully under transient conditions over a period of 6 years using monthly periods. The results show that groundwater inflows and outflows have the lowest contribution to the overall lakes’ budget. The model has been subsequently used to evaluate the impacts of upstream reservoirs. The results show that these reservoirs have a significant effect on lake stages but not on groundwater levels. A trade-off curve between the quantum of water released and the average stage in Lake Mogan has been developed to enhance decision makers’ ability for sustainable management of the system in the long term.

  20. Repeated Lake-Stream Divergence in Stickleback Life History within a Central European Lake Basin

    PubMed Central

    Moser, Dario; Roesti, Marius; Berner, Daniel

    2012-01-01

    Life history divergence between populations inhabiting ecologically distinct habitats might be a potent source of reproductive isolation, but has received little attention in the context of speciation. We here test for life history divergence between threespine stickleback inhabiting Lake Constance (Central Europe) and multiple tributary streams. Otolith analysis shows that lake fish generally reproduce at two years of age, while their conspecifics in all streams have shifted to a primarily annual life cycle. This divergence is paralleled by a striking and consistent reduction in body size and fecundity in stream fish relative to lake fish. Stomach content analysis suggests that life history divergence might reflect a genetic or plastic response to pelagic versus benthic foraging modes in the lake and the streams. Microsatellite and mitochondrial markers further reveal that life history shifts in the different streams have occurred independently following the colonization by Lake Constance stickleback, and indicate the presence of strong barriers to gene flow across at least some of the lake-stream habitat transitions. Given that body size is known to strongly influence stickleback mating behavior, these barriers might well be related to life history divergence. PMID:23226528

  1. Lake sediments as natural seismographs: Earthquake-related deformations (seismites) in central Canadian lakes

    NASA Astrophysics Data System (ADS)

    Doughty, M.; Eyles, N.; Eyles, C. H.; Wallace, K.; Boyce, J. I.

    2014-11-01

    Central Canada experiences numerous intraplate earthquakes but their recurrence and source areas remain obscure due to shortness of the instrumental and historic records. Unconsolidated fine-grained sediments in lake basins are 'natural seismographs' with the potential to record ancient earthquakes during the last 10,000 years since the retreat of the Laurentide Ice Sheet. Many lake basins are cut into bedrock and are structurally-controlled by the same Precambrian basement structures (shear zones, terrane boundaries and other lineaments) implicated as the source of ongoing mid-plate earthquake activity. A regional seismic sub-bottom profiling of lakes Gull, Muskoka, Joseph, Rousseau, Ontario, Wanapitei, Fairbanks, Vermilion, Nipissing, Georgian Bay, Mazinaw, Simcoe, Timiskaming, Kipawa, Parry Sound and Lake of Bays, encompassing a total of more than 2000 kilometres of high-resolution track line data supplemented by multibeam and sidescan sonar survey records show a consistent sub-bottom stratigraphy of relatively-thick lowermost lateglacial facies composed of interbedded semi-transparent mass flow facies (debrites, slumps) and rhythmically-laminated silty-clays. Mass flows together with cratered ('kettled') lake floors and associated deformations reflect a dynamic ice-contact glaciolacustrine environment. Exceptionally thick mass flow successions in Lake Timiskaming along the floor of the Timiskaming Graben within the seismically-active Western Quebec Seismic Zone (WQSZ), point to a higher frequency of earthquakes and slope failure during deglaciation and rapid glacio-isostatic rebound though faulting continues into the postglacial. Lateglacial faulting, diapiric deformation and slumping of coeval lateglacial sediments is observed in Parry Sound, Lake Muskoka and Lake Joseph, which are all located above prominent Precambrian terrane boundaries. Lateglacial sediments are sharply overlain by relatively-thin rhythmically-laminated and often semi

  2. EPA Awards Great Lakes Restoration Initiative Grant to Central Michigan University to Monitor Coastal Wetlands

    EPA Pesticide Factsheets

    CHICAGO -- The U.S Environmental Protection Agency today announced that Central Michigan University in Mt. Pleasant, Michigan, has received a $10 million Great Lakes Restoration Initiative grant to monitor coastal wetlands around the Great Lakes basin over

  3. Chemical characteristics of south-central Lake Huron

    USGS Publications Warehouse

    Allen, Herbert E.

    1964-01-01

    Water samples were collected for chemical analysis during eight cruises of the U.S. Bureau of Commercial Fisheries M/V CISCO in south-central Lake Huron in June-October 1956. Temperature, pH, conductivity, and the concentrations of Na+, K+, Ca++, C1-, SO4-, SiO2, and dissolved oxygen were determined for 233 samples from stations at the mouth of Saginaw Bay and along a transect from Harbor Beach, Michigan, to Goderich, Ontario. The chemical compostion, with the exception of silica, did not vary with season or depth. Water flowing into the lake from Saginaw Bay sometimes caused marked increases in the concentration of chemicals in surface samples at certain stations. Prevailing currents determined the location of these areas of higher salt concentration.

  4. Mercury in the central European lake district - case study Plešné lake

    NASA Astrophysics Data System (ADS)

    Navratil, Tomas; Rohovec, Jan; Novakova, Tereza; Matouskova, Sarka; Kopacek, Jiri; Kana, Jiri

    2017-04-01

    The central European lake district extends within the Bohemian forest and Bavarian forest Mountains. It includes 8 glacial lakes extending in altitudes from 935 to 1087 m a.s.l. All of them have been oligotrophic and forests of the lake catchments are dominated by Norway spruce (Picea abies). Plešné lake (PL) catchment is at 1087 m .a.s.l. and it covers area of 0.67 km2. In 2004, the forest at PL catchment was infested by the bark beetle (Ips typographus) and 88%-99% of trees had died by 2011. In contrast to relatively detailed research of North American and Scandinavian lake ecosystems the information concerning Hg contamination of central European lake ecosystems are rather scarce. The PL ecosystem can provide base for assessment of Hg contamination as well as for changes induced by the bark beetle infestation. In 2016, mean annual Hg concentration in bulk precipitation at Plešné lake reached 3.0 ng/L and bulk Hg deposition flux amounted at 4.6 µg/m2. The most important pathway of Hg deposition to the forest ecosystems has been litterfall. The highest Hg concentrations in litterfall material at PL were found in lichens 205 µg/kg, mixture of unidentifiable organic debris 159 µg/kg and bark 123 µg/kg. Litterfall spruce needles averaged at 56 µg/kg, only. Removal of spruce due to bark beetle infestation caused decrease of litterfall Hg fluxes. Recent litterfall fluxes in the unimpacted stands reached 55.8 µg/m2, while in the impacted dead stands they amounted 23.0 µg/m2, only. The qualitative composition of the litterfall in the infested stands was typical with absence of needles and prevalence of twigs and bark. To assess changes in Hg distribution within the soil profile due to forest dieback the soil data from year 1999 were compared with 2015 data. The mean Hg concentrations in the O horizons decreased from 424 to 311 µg/kg between years 1999 and 2015, and in A horizons the situation was reversed and an increase from 353 to 501 µg/kg occurred. The

  5. Drought Analysis in the Tuz Lake Basin, Central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Ustaoglu, Beyza; Akın, Burcu

    2017-04-01

    The research area, Tuz Lake Basin is located in Central Anatolia Region in Turkey. The drought is observed in this area with the result of the meteorological data analysis, satellite imagery and field research. The aim of this study is to determine temporal and spatial characterists of the drought, frequency and extreme droughtness possibilities, drought period, amplitude of the drought and its severity which is observed in Tuz Lake within the context of climate change process effects in Turkey, by using Standart Precipitation Index (SPI) Palmer Drought Harshness Index, De Martonne and Erinç Method. Since the indexes which are used in the study have different parameters, not only meteorological results but also agricultural and hydrological drought results can be inferred. For this purpose, measurements of 12 meteorological stations in the basin between the years 1975-2015 will be studied applying the aforementioned methods in MATLAB. SRTM satellite images used in the study is provided by American Geological Survey (USGS). The findings from satellite imagery and meteorological data integrated into Geographic Information Systems Software ArcMap 10.1, then the effects of the drought to the Tuz Lake were analyzed. The findings of the analysis will be interpreted with the support of the field studies.

  6. Hydrology of Lake June in winter, Highlands County, South-central Florida

    USGS Publications Warehouse

    Belles, Roger G.; Martin, Edward H.

    1985-01-01

    Lake June in Winter is in central Highlands County near the town of Lake Placid in south-central Florida. Recreation and citrus-grove irrigation are the major uses of lake water. Land use around the lake is residential citrus, and undeveloped. Most of the land use in the 44-square mile lake-drainage area is undeveloped. The surface area of the lake is approximately 5.7 square miles with water-surface altitude average of 74 feet. The extremes in lake altitude for the period 1945-82 were 77.58 feet in October 1948, and 71.62 feet in May 1981. Flow into Lake June in Winter is from Lake Placid to the south through Catfish Creek. Flow out of the Lake is northward through Stearns Creek to Lake Francis, and eventually by Josephine Creek to Lake Istokpoga. The quality of water in Lake June in Winter is good. Specific conductance was found to be generally low, ranging between 90 umho/cm to 170 umho/cm, indicating a lack of dissolved solids present in the lake. The lake is clear, with transparency values between 3 and 14 feet. Total nitrogen was found to be 0.60 mg/L indicating a minimal effect from nitrogen fertilizer washoff or septic-tank discharge. (USGS)

  7. Acidity of Lakes and Impoundments in North-Central Minnesota

    Treesearch

    Elon S. Verry

    1981-01-01

    Measurements of lake and impoundment pH for several years, intensive sampling within years, and pH-calcium plots verify normal pH levels and do not show evidence of changes due to acid precipitation. These data in comparison with general lake data narrow the northern Lake States area in which rain or snow may cause lake acidification.

  8. Subglacial Lake McGregor, south-central Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Munro-Stasiuk, Mandy J.

    2003-08-01

    It is proposed that a lake, here named "Subglacial Lake McGregor", existed beneath the Laurentide Ice Sheet at, or near, the last glacial maximum. The lake resided in the ancient buried McGregor and Tee Pee preglacial valleys, which are now mostly filled with glacigenic deposits. The greatest thickness of sediment in the valleys is in the form of chaotically deposited lake beds that were laid down in a subaqueous environment by a number of process: gravity flow, water transport, and suspension settling. Topographic, sedimentary, and stratigraphic evidence point to a subglacial, not a proglacial, origin for the beds. During the early stages of lake existence, ice movement was significant as there are numerous sets of shear planes in the sedimentary beds. This indicates that the lake filled (lake sedimentation) and drained (shearing of the beds by overlying ice when ice contacted the bed) often. Thus, early in its history, the lake(s) was/were ephemeral. During the later stages of lake existence, the lake was relatively stable with no rapid draining or influx of sediment. Gradual drainage of the lake resulted in lowering of the ice onto the lake beds resulting in subglacial till deposition. Drainage was not a single continuous event. Rather it was characterized by multiple phases of near total drainage (till deposition), followed by water accumulation (lake sedimentation). Water accumulation events became successively less significant reflected by thinning of lake beds and thickening of till beds higher in the stratigraphic sequence. Since subglacial lake sedimentation appears to be restricted to the subglacial valleys, it is suggested that the valleys acted as a large-scale interconnected cavity system that both stored and transported water. It is also suggested that these acted as the main routes of water flow beneath the Laurentide Ice Sheet.

  9. Glacial lake expansion in the central Himalayas by Landsat images, 1990-2010.

    PubMed

    Nie, Yong; Liu, Qiao; Liu, Shiyin

    2013-01-01

    Glacial lake outburst flood (GLOF) is a serious hazard in high, mountainous regions. In the Himalayas, catastrophic risks of GLOFs have increased in recent years because most Himalayan glaciers have experienced remarkable downwasting under a warming climate. However, current knowledge about the distribution and recent changes in glacial lakes within the central Himalaya mountain range is still limited. Here, we conducted a systematic investigation of the glacial lakes within the entire central Himalaya range by using an object-oriented image processing method based on the Landsat Thematic Mapper (TM) or Enhanced Thematic Mapper (ETM) images from 1990 to 2010. We extracted the lake boundaries for four time points (1990, 2000, 2005 and 2010) and used a time series inspection method combined with a consistent spatial resolution of Landsat images that consistently revealed lake expansion. Our results show that the glacial lakes expanded rapidly by 17.11% from 1990 to 2010. The pre-existing, larger glacial lakes, rather than the newly formed lakes, contributed most to the areal expansion. The greatest expansions occurred at the altitudinal zones between 4800 m and 5600 m at the north side of the main Himalayan range and between 4500 m and 5600 m at the south side, respectively. Based on the expansion rate, area and type of glacial lakes, we identified 67 rapidly expanding glacial lakes in the central Himalayan region that need to be closely monitored in the future. The warming and increasing amounts of light-absorbing constituents of snow and ice could have accelerated the melting that directly affected the glacial lake expansion. Across the main central Himalayas, glacial lakes at the north side show more remarkable expansion than those at the south side. An effective monitoring and warning system for critical glacial lakes is urgently needed.

  10. Glacial Lake Expansion in the Central Himalayas by Landsat Images, 1990–2010

    PubMed Central

    Nie, Yong; Liu, Qiao; Liu, Shiyin

    2013-01-01

    Glacial lake outburst flood (GLOF) is a serious hazard in high, mountainous regions. In the Himalayas, catastrophic risks of GLOFs have increased in recent years because most Himalayan glaciers have experienced remarkable downwasting under a warming climate. However, current knowledge about the distribution and recent changes in glacial lakes within the central Himalaya mountain range is still limited. Here, we conducted a systematic investigation of the glacial lakes within the entire central Himalaya range by using an object-oriented image processing method based on the Landsat Thematic Mapper (TM) or Enhanced Thematic Mapper (ETM) images from 1990 to 2010. We extracted the lake boundaries for four time points (1990, 2000, 2005 and 2010) and used a time series inspection method combined with a consistent spatial resolution of Landsat images that consistently revealed lake expansion. Our results show that the glacial lakes expanded rapidly by 17.11% from 1990 to 2010. The pre-existing, larger glacial lakes, rather than the newly formed lakes, contributed most to the areal expansion. The greatest expansions occurred at the altitudinal zones between 4800 m and 5600 m at the north side of the main Himalayan range and between 4500 m and 5600 m at the south side, respectively. Based on the expansion rate, area and type of glacial lakes, we identified 67 rapidly expanding glacial lakes in the central Himalayan region that need to be closely monitored in the future. The warming and increasing amounts of light-absorbing constituents of snow and ice could have accelerated the melting that directly affected the glacial lake expansion. Across the main central Himalayas, glacial lakes at the north side show more remarkable expansion than those at the south side. An effective monitoring and warning system for critical glacial lakes is urgently needed. PMID:24376778

  11. Rapid Expansion of Glacial Lakes Caused by Climate and Glacier Retreat in the Central Himalayas

    NASA Astrophysics Data System (ADS)

    Wang, W.

    2016-12-01

    Glacial lake outburst floods are among the most serious natural hazards in the Himalayas. Such floods are of high scientific and political importance because they exert trans-boundary impacts on bordering countries. The preparation of an updated inventory of glacial lakes and the analysis of their evolution are an important first step in assessment of hazards from glacial lake outbursts. Here, we report the spatiotemporal developments of the glacial lakes in the Poiqu River basin, a trans-boundary basin in the Central Himalayas, from 1976 to 2010 based on multi-temporal Landsat images. Studied glacial lakes are classified as glacierfed lakes and non-glacier-fed lakes according to their hydrologic connection to glacial watersheds. A total of 119 glacial lakes larger than 0.01 km2 with an overall surface area of 20.22 km2 (±10.8%) were mapped in 2010, with glacier-fed lakes being predominant in both number (69, 58.0%) and area (16.22 km2, 80.2%). We found that lakes connected to glacial watersheds (glacier-fed lakes) significantly expanded (122.1%) from 1976 to 2010, whereas lakes not connected to glacial watersheds (non-glacier-fed lakes) remained stable (+2.8%) during the same period. This contrast can be attributed to the impact of glaciers. Retreating glaciers not only supply meltwater to lakes but also leave space for them to expand. Compared with other regions of the Hindu Kush Himalayas (HKH), the lake area per glacier area in the Poiqu River basin was the highest. This observation might be attributed to the different climate regimes and glacier status along the HKH. The results presented in this study confirm the significant role of glacier retreat on the evolution of glacial lakes.

  12. Monitoring lake level changes by altimetry in the arid region of Central Asia

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Liao, J. J.; Shen, G. Z.; Zhang, X. L.

    2017-07-01

    The study of lake level changes in arid region of Central Asia not only has important significance for the management and sustainable development of inland water resources, but also provides the basis for further study on the response of lakes to climate change and human activities. Therefore, in this paper, eleven typical lakes in Central Asia were observed. The lake edges were obtained through image interpretation using the quasi-synchronous MODIS image, and then water level information with long period (2002-2015) was acquired using ENVISAT/RA-2 and Cryosat-2 satellite borne radar altimeter data. The results show that these 11 lakes all have obvious seasonal changes of water level in a year with a high peak at different month. During 2002 - 2015, their water levels present decreased trend generally except Sarygamysh Lake, Alakol Lake and North Aral Sea. The alpine lakes are most stables, while open lakes’ levels change the most violently and closed lakes change diversely among different lakes.

  13. Cercarial dermatitis and lake eutrophication in south-central Chile

    PubMed Central

    VALDOVINOS, C.; BALBOA, C.

    2008-01-01

    SUMMARY Cercarial dermatitis is caused by exposure to the cercariae of schistosome species which have birds or mammals as their definitive hosts. A public alarm was raised in the summer of 2004 when this parasitic disease was observed for the first time in south-central Chile at Laguna Chica de San Pedro (36° 51″ S, 73° 05″ W). Swimmers at this eutrophic lake were surveyed in order to estimate the amount of cercarial dermatitis in the area; participants were observed during the summers of 2004 and 2005 for clinical signs of cercarial dermatitis and 25 Chilina dombeyana snails were collected monthly from Laguna Chica de San Pedro during one year and then examined for animal schistosome cercariae. We found that 3% of the swimmers had pruritic maculopapular rashes on their legs, arms, necks, or other body parts and that between 9·1% (May 2006) and 52·4% (November 2004) of the snails examined were infected with the bird schistosome cercariae Trichobilharzia sp. PMID:17553177

  14. Assessment of lake trout spawning habitat quality in central Lake Huron by submarine

    USGS Publications Warehouse

    Manny, Bruce A.; Edsall, Thomas A.

    1989-01-01

    Interstitial water quality was measured using a submersible at seven locations on Six Fathom Bank. Historically, the bank was an important lake trout spawning ground. It is currently the focus of coordinated, interagency efforts to rehabilitate lake trout in Lake Huron. Water quality, evaluated from measurements of biochemical oxygen demand, dissolved oxygen, ammonia, and hydrogen sulfide among the rocks, would not prevent lake trout eggs from hatching successfully on the bank.

  15. Geochemical evidence of hydrothermal recharge in Lake Baringo, central Kenya Rift Valley

    NASA Astrophysics Data System (ADS)

    Tarits, Corinne; Renaut, Robin W.; Tiercelin, Jean-Jacques; Le Hérissé, Alain; Cotten, Jo; Cabon, Jean-Yves

    2006-06-01

    Lake Baringo, a freshwater lake in the central Kenya Rift Valley, is fed by perennial and ephemeral rivers, direct rainfall, and hot springs on Ol Kokwe Island near the centre of the lake. The lake has no surface outlet, but despite high evaporation rates it maintains dilute waters by subsurface seepage through permeable sediments and faulted lavas. New geochemical analyses (major ions, trace elements) of the river, lake, and hot spring waters and the suspended sediments have been made to determine the main controls of lake water quality. The results show that evaporative concentration and the binary mixing between two end members (rivers and thermal waters) can explain the hydrochemistry of the lake waters.Two zones are recognized from water composition. The southern part of the lake near sites of perennial river inflow is weakly influenced by evaporation, has low total dissolved species (TDS), and has a seasonally variable load of mainly detrital suspended sediments. In contrast, waters of the northern part of the lake show evidence for strong evaporation (TDS of up to eight times inflow). Authigenic clay minerals and calcite may be precipitating from those more concentrated fluids.The subaerial hot-spring waters have a distinctive chemistry and are enriched in some elements that are also present in the lake water. Comparison of the chemical composition of the inflowing surface waters and lake water shows (1) an enrichment of some species (HCO3-, Cl, SO42-, F, Na, B, V, Cr, As, Mo, Ba and U) in the lake, (2) a depletion in SiO2 in the lake, and (3) a possible hydrothermal origin for most F. The rare earth element distribution and the F/Cl and Na/Cl ratios give valuable information on the rate of mixing of the river and hydrothermal fluids in the lake water. Calculations imply that thermal fluids may be seeping upward locally into the lake through grid-faulted lavas, particularly south of Ol Kokwe Island.

  16. Glacial lakes amplify glacier recession in the central Himalaya

    NASA Astrophysics Data System (ADS)

    King, Owen; Quincey, Duncan; Carrivick, Jonathan; Rowan, Ann

    2016-04-01

    The high altitude and high latitude regions of the world are amongst those which react most intensely to climatic change. Across the Himalaya glacier mass balance is predominantly negative. The spatial and temporal complexity associated with this ice loss across different glacier clusters is poorly documented however, and our understanding of the processes driving change is limited. Here, we look at the spatial variability of glacier hypsometry and glacial mass loss from three catchments in the central Himalaya; the Dudh Koshi basin, Tama Koshi basin and an adjoining section of the Tibetan Plateau. ASTER and SETSM digital elevation models (2014/15), corrected for elevation dependant biases, co-registration errors and along or cross track tilts, are differenced from Shuttle Radar Topographic Mission (SRTM) data (2000) to yield surface lowering estimates. Landsat data and a hypsometric index (HI), a classification scheme used to group glaciers of similar hypsometry, are used to examine the distribution of glacier area with altitude in each catchment. Surface lowering rates of >3 m/yr can be detected on some glaciers, generally around the clean-ice/debris-cover boundary, where dark but thin surface deposits are likely to enhance ablation. More generally, surface lowering rates of around 1 m/yr are more pervasive, except around the terminus areas of most glaciers, emphasising the influence of a thick debris cover on ice melt. Surface lowering is only concentrated at glacier termini where glacial lakes have developed, where surface lowering rates are commonly greater than 2.5 m/yr. The three catchments show contrasting hypsometric distributions, which is likely to impact their future response to climatic changes. Glaciers of the Dudh Koshi basin store large volumes of ice at low elevation (HI > 1.5) in long, debris covered tongues, although their altitudinal range is greatest given the height of mountain peaks in the catchment. In contrast, glaciers of the Tama Koshi

  17. Diversity of extremophilic purple phototrophic bacteria in Soap Lake, a Central Washington (USA) Soda Lake.

    PubMed

    Asao, Marie; Pinkart, Holly C; Madigan, Michael T

    2011-08-01

    Culture-based and culture-independent methods were used to explore the diversity of phototrophic purple bacteria in Soap Lake, a small meromictic soda lake in the western USA. Among soda lakes, Soap Lake is unusual because it consists of distinct upper and lower water bodies of vastly different salinities, and its deep waters contain up to 175 mM sulfide. From Soap Lake water new alkaliphilic purple sulfur bacteria of the families Chromatiaceae and Ectothiorhodospiraceae were cultured, and one purple non-sulfur bacterium was isolated. Comparative sequence analysis of pufM, a gene that encodes a key photosynthetic reaction centre protein universally found in purple bacteria, was used to measure the diversity of purple bacteria in Soap Lake. Denaturing gradient gel electrophoresis and subsequent phylogenetic analyses of pufMs amplified from Soap Lake water revealed that a significant diversity of purple bacteria inhabit this soda lake. Although close relatives of several of the pufM phylotypes obtained from cultured species could also be detected in Soap Lake water, several other more divergent pufM phylotypes were also detected. It is possible that Soap Lake purple bacteria are major contributors of organic matter into the ecosystem of this lake, especially in its extensive anoxic and sulfidic deep waters. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  18. Ancient ice islands in salt lakes of the Central Andes

    USGS Publications Warehouse

    Hurlbert, S.H.; Chang, Cecily C.Y.

    1984-01-01

    Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer.

  19. Glacial Lake Musselshell: Late Wisconsin slackwater on the Laurentide ice margin in central Montana, USA

    USGS Publications Warehouse

    Davis, N.K.; Locke, W. W.; Pierce, K.L.; Finkel, R.C.

    2006-01-01

    Cosmogenic surface exposure ages of glacial boulders deposited in ice-marginal Lake Musselshell suggest that the lake existed between 20 and 11.5 ka during the Late Wisconsin glacial stage (MIS 2), rather than during the Late Illinoian stage (MIS 6) as traditionally thought. The altitude of the highest ice-rafted boulders and the lowest passes on the modern divide indicate that glacial lake water in the Musselshell River basin reached at least 920-930 m above sea level and generally remained below 940 m. Exposures of rhythmically bedded silt and fine sand indicate that Lake Musselshell is best described as a slackwater system, in which the ice-dammed Missouri and Musselshell Rivers rose and fell progressively throughout the existence of the lake rather than establishing a lake surface with a stable elevation. The absence of varves, deltas and shorelines also implies an unstable lake. The changing volume of the lake implies that the Laurentide ice sheet was not stable at its southernmost position in central Montana. A continuous sequence of alternating slackwater lake sediment and lacustrine sheetflood deposits indicates that at least three advances of the Laurentide ice sheet occurred in central Montana between 20 and 11.5 ka. Between each advance, it appears that Lake Musselshell drained to the north and formed two outlet channels that are now occupied by extremely underfit streams. A third outlet formed when the water in Lake Musselshell fully breached the Larb Hills, resulting in the final drainage of the lake. The channel through the Larb Hills is now occupied by the Missouri River, implying that the present Missouri River channel east of the Musselshell River confluence was not created until the Late Wisconsin, possibly as late as 11.5 ka. ?? 2005 Elsevier B.V. All rights reserved.

  20. Multidisciplinary characterisation of sedimentary processes in a recent maar lake (Lake Pavin, French Massif Central) and implication for natural hazards

    NASA Astrophysics Data System (ADS)

    Chapron, E.; Albéric, P.; Jézéquel, D.; Versteeg, W.; Bourdier, J.-L.; Sitbon, J.

    2010-09-01

    Sedimentation processes occurring in the most recent maar lake of the French Massif Central (Lake Pavin) are documented for the first time based on high resolution seismic reflection and multibeam bathymetric surveys and by piston coring and radiocarbon dating on a sediment depocentre developed on a narrow sub aquatic plateau. This new data set confirms the mid Holocene age of maar lake Pavin formation at 6970±60 yrs cal BP and highlights a wide range of gravity reworking phenomena affecting the basin. In particular, a slump deposit dated between AD 580-640 remoulded both mid-Holocene lacustrine sediments, terrestrial plant debris and some volcanic material from the northern crater inner walls. Between AD 1200 and AD 1300, a large slide scar mapped at 50 m depth also affected the southern edge of the sub aquatic plateau, suggesting that these gas-rich biogenic sediments (laminated diatomite) are poorly stable. Although several triggering mechanisms can be proposed for these prehistoric sub-aquatic mass wasting deposits in Lake Pavin, we argue that such large remobilisation of gas-rich sediments may affect the gas stability in deep waters of meromictic maar lakes. This study highlights the need to further document mass wasting processes in maar lakes and their impacts on the generation of waves, favouring the development of dangerous (and potentially deadly) limnic eruptions.

  1. Water quality of Lake Granbury, north-central Texas

    USGS Publications Warehouse

    Andrews, Freeman L.; Strause, Jeffrey L.

    1982-01-01

    Seasonal-temperature variations and variations in the concentration of dissolved oxygen result in dissolved iron and manganese, total inorganic nitrogen, and total phosphorus being recycled within the lake; however, no significant accumulations of these constituents were detected.

  2. Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa).

    PubMed

    Tiodjio, Rosine E; Sakatoku, Akihiro; Nakamura, Akihiro; Tanaka, Daisuke; Fantong, Wilson Y; Tchakam, Kamtchueng B; Tanyileke, Gregory; Ohba, Takeshi; Hell, Victor J; Kusakabe, Minoru; Nakamura, Shogo; Ueda, Akira

    2014-08-21

    The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos.

  3. Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa)

    PubMed Central

    Tiodjio, Rosine E.; Sakatoku, Akihiro; Nakamura, Akihiro; Tanaka, Daisuke; Fantong, Wilson Y.; Tchakam, Kamtchueng B.; Tanyileke, Gregory; Ohba, Takeshi; Hell, Victor J.; Kusakabe, Minoru; Nakamura, Shogo; Ueda, Akira

    2014-01-01

    The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos. PMID:25141868

  4. Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa)

    NASA Astrophysics Data System (ADS)

    Tiodjio, Rosine E.; Sakatoku, Akihiro; Nakamura, Akihiro; Tanaka, Daisuke; Fantong, Wilson Y.; Tchakam, Kamtchueng B.; Tanyileke, Gregory; Ohba, Takeshi; Hell, Victor J.; Kusakabe, Minoru; Nakamura, Shogo; Ueda, Akira

    2014-08-01

    The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos.

  5. Hydrology of Little Rock Lake in Vilas County, north-central Wisconsin

    USGS Publications Warehouse

    Rose, W.J.

    1993-01-01

    Water budgets were developed for Little Rock Lake for October 1983 through September 1990 as part of a study to evaluate the chemical and biological effects of artificially acidifying one basin of the two-basin lake. The 17.9-hectare seepage lake is situated in 60- to 90-meter-thick, predominantly sand and gravel glacial deposits of Vilas County, north-central Wisconsin. Annual precipitation during the study varied from 647 to 926 mm (millimeters). Average annual precipitation during 1951-80, based on nearby National Weather Service stations, was 825 mm. Annual evaporation from the lake surface ranged from 495 to 648 mm. Total lake-stage fluctuation was 930 mm during the study. Lake volume at the maximum stage was 31 percent greater than at the minimum lake stage. Inflow to the lake was dominated by precipitation, which was about 99 percent of total inflow. Ground-water inflow to the lake was transient, occurring only intermittently during October 1983 through September 1986, and amounted to only about 1 percent of total inflow. No ground water flowed into the lake from October 1986 through September 1990. Evaporation accounted for about two-thirds of total outflow from the lake, and lake water discharging to the underlying aquifer accounted for the remainder. The average hydraulic residence times for the 7-year study period were 3.9, 3.3, and 4 years for the entire lake, the south basin, and the north basin, respectively; corresponding chemical residence times were 10.9, 9.3, and 10 years.

  6. Geologic controls on the formation of lakes in north-central Florida

    USGS Publications Warehouse

    Kindinger, Jack G.; Davis, Jeffrey B.; Flocks, James G.; Pitman, Janet K; Carroll, Alan R.

    1998-01-01

    Fluid exchange between surficial waters and groundwater, as well as the processes that control this exchange, are of critical concern to water management districts and planners. Digital high-resolution seismic systems were used to collect geophysical data from 30 lakes of north-central Florida. Although using seismic profile data in the past has been less than successful, the use of digital technology has increased the potential for success. Seismic profiles collected from the lakes of north-central Florida have shown the potential application of these techniques in understanding the formation of individual lakes. In each case study, lake structure and geomorphology were controlled by solution and/or mechanical processes. Processes that control lake development are twofold: 1) karstification or dissolution of the underlying limestone, and 2) me collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone. Lake size and shape are a factor of the thickness of overburden and size of the collapse or subsidence and/or clustering of depressions allowing for lake development. Lake development is through progressive sequence stages to maturity that can be delineated into geomorphic types. Case studies have shown that lakes can be divided by geomorphic types into progressive developmental phases: (1) active subsidence or collapse phase (young) - the open to partially filled collapse structures typically associated with sink holes; (2) transitional phase (middle age) - the sinkhole is plugged as the voids within the collapse are filled with sediment, periodic reactivation may occur; (3) baselevel phase (mature) - active sinkholes are progressively plugged by the continual erosion of material into the basin, and eventually sediment fills the basins; and (4) polje (drowned prairie) - broad flat-bottom basins located within the epiphreatic zone that are inundated at high

  7. Lake-levels, vegetation and climate in Central Asia during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Amosov, Mikhail

    2014-05-01

    Central Asian region is bounded in the east corner of the Greater Khingan Range and the Loess Plateau, and to the west - the Caspian Sea. This representation of region boundaries is based on classical works of A.Humboldt and V.Obruchev. Three typical features of Central Asia nature are: climate aridity, extensive inland drainage basins with numerous lakes and mountain systems with developed glaciation. Nowadays the extensive data is accumulated about lake-levels during the Last Glacial Maximum (LGM) in Central Asia. Data compilation on 20 depressions, where lakes exist now or where they existed during LGM, shows that most of them had usually higher lake-level than at present time. This regularity could be mentioned for the biggest lakes (the Aral Sea, the Balkhash, the Ysyk-Kol etc.) and for small ones that located in the mountains (Tien Shan, Pamir and Tibet). All of these lake basins get the precipitation due to westerlies. On the other hand lakes, which are located in region's east rimland (Lake Qinghai and lakes in Inner Mongolia) and get the precipitation due to summer East Asian monsoons, do not comply with the proposed regularity. During LGM these lake-levels were lower than nowadays. Another exception is Lake Manas, its lake-level was also lowered. Lake Manas is situated at the bottom of Junggar Basin. There are many small rivers, which come from the ranges and suffer the violent fluctuation in the position of its lower channel. It is possible to assume that some of its runoff did not get to Lake Manas during LGM. Mentioned facts suggest that levels of the most Central Asian lakes were higher during LGM comparing to their current situation. However, at that period vegetation was more xerophytic than now. Pollen data confirm this information for Tibet, Pamir and Tien Shan. Climate aridization of Central Asia can be proved by data about the intensity of loess accumulation during LGM. This evidence received for the east part of region (the Loess Plateau) and

  8. Water budget and vertical conductance for Lowry (Sand Hill) Lake in north-central Florida, USA

    NASA Astrophysics Data System (ADS)

    Motz, Louis H.; Sousa, Gregory D.; Annable, Michael D.

    2001-09-01

    Water-budget components and the vertical conductance were determined for Lowry (Sand Hill) Lake in north-central Florida, USA. In this type of lake, which interacts with both the surface-water and groundwater systems, the inflow components are precipitation, surface-water inflow, groundwater inflow, and direct runoff (i.e. overland flow), and the outflow components are evaporation, groundwater outflow, and surface-water outflow. In a lake and groundwater system that is typical of many karst lakes in Florida, a large part of the groundwater outflow occurs by means of vertical leakage through an underlying confining unit to a deeper, highly transmissive aquifer called the upper Floridan aquifer. The water-budget component that represents vertical leakage to the upper Floridan aquifer was calculated as a residual using the water-budget equation. For the 13 month period from August 1994 to August 1995, relative to the surface area of the lake, rainfall at Lowry Lake was 1.55 m yr -1, surficial aquifer inflow was 0.79 m yr -1, surface-water inflow was 1.92 m yr -1, and direct runoff was 0.01 m yr -1. Lake evaporation was 1.11 m yr -1, and surface-water outflow was 1.61 m yr -1. The lake stage increased 0.07 m yr -1, and the vertical leakage to the upper Floridan aquifer was 1.48 m yr -1. Surficial aquifer outflow from the lake was negligible. At Lowry Lake, vertical leakage is a major component of the water budget, comprising about 35% of the outflow during the study period. The vertical conductance ( KV/ b), a coefficient that represents the average of the vertical conductances of the hydrogeologic units between the bottom of a lake and the top of the upper Floridan aquifer, was determined to be 2.51 × 10 -4 day -1 for Lowry Lake.

  9. The interdependence of lake ice and climate in central North America

    NASA Technical Reports Server (NTRS)

    Jelacic, A. J. (Principal Investigator)

    1972-01-01

    There are no author-identified significant results in this report. This investigation is to identify any correlations between the freeze/ thaw cycles of lakes and regional weather variations. ERTS-1 imagery of central Canada and north central United States is examined on a seasonal basis. The ice conditions of certain major study lakes are noted and recorded on magnetic tape, from which the movement of a freeze/thaw transition zone may be deduced. Weather maps and tables are used to establish any obvious correlations. The process of selecting major study lakes is discussed, and a complete lake directory is presented. Various routines of the software support library are described, accompanied by output samples. Procedures used for ERTS imagery processing are presented along with the data analysis plan. Application of these procedures to selected ERTS imagery has demonstrated their utility. Preliminary results show that the freeze/thaw transition zone can be monitored from ERTS.

  10. Sublake geologic structure from high-resolution seismic-reflection data from four sinkhole lakes in the Lake Wales Ridge, Central Florida

    USGS Publications Warehouse

    Tihansky, A.B.; Arthur, J.D.; DeWitt, D.W.

    1996-01-01

    Seismic-reflection profiles from Lake Wales, Blue Lake, Lake Letta, and Lake Apthorp located along the Lake Wales Ridge in central Florida provide local detail within the regional hydrogeologic framework as described by litho- and hydrostratigraphic cross sections. Lakes located with the mantled karst region have long been considered to be sinkhole lakes, originating from subsidence activity. High-resolution seismic- reflection data confirm this origin for these four lakes. The geologic framework of the Lake Wales Ridge has proven to be a suitable geologic setting for continuous high-resolution seismic-reflection profiling in lakes; however, the nature of the lake-bottom sediments largely controls the quality of the seismic data. In lakes with significant organic-rich bottom deposits, interpretable record was limited to areas where organic deposits were minimal. In lakes with clean, sandy bottoms, the seismic-reflection methods were highly successful in obtaining data that can be correlated with sublake subsidence features. These techniques are useful in examining sublake geology and providing a better understanding of how confining units are affected by subsidence in a region where their continuity is of significant importance to local lake hydrology. Although local geologic control around each lake generally corresponds to the regional geologic framework, local deviations from regional geologic trends occur in sublake areas affected by subsidence activity. Each of the four lakes examined represents a unique set of geologic controls and provides some degree of structural evidence of subsidence activity. Sublake geologic structures identified include: (1) marginal lake sediments dipping into bathymetric lows, (2) lateral discontinuity of confining units including sags and breaches, (3) the disruption and reworking of overlying unconsolidated siliciclastic sediments as they subside into the underlying irregular limestone surface, and (4) sublake regions where

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

    SciTech Connect

    Hester, P.M. )

    1989-09-01

    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}.

  12. Temporal CO2 flux variations of Lake Nam Co in the central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Xia, H.; Zhou, S.

    2016-12-01

    Lakes are important CO2 sources or sinks in the global carbon cycle. However, the role of a lake acting as a source or a sink of CO2 in different environments still remains uncertain due to data paucity and differing methods adopted. The lake-atmosphere CO2 fluxes have not been observed within the expanse of central Tibetan Plateau (TP) due to the harsh climate and inaccessibility. In this study, eddy covariance (EC) method was used to obtain CO2 fluxes over Lake Nam Co, the highest and second largest lake on the TP. This is the first long-term observation of CO2 fluxes over a lake in the central TP. The observations were conducted from 2012 to 2014. Daily-averaged CO2 flux over the lake ranged from -292 mmol m-2d-1 to 81 mmol m-2d-1 and displayed a decreasing trend during the observation period from July to October. Average daily CO2 flux was -48 mmol m-2d-1 in the observation period, indicating a CO2 sink.

  13. Sediment Characteristics of a High-Mountain Lake in South Central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Ataselim, Zeynep; Leroy, Suzanne; Gurbuz, Alper; Gurbuz, Esra; Onur Yucel, Tahsin; Yedek, Ozgur; Koc, Koray

    2016-04-01

    Lake Dipsiz is at the top of Mount Erenler, located 55 km west of Konya city in Central Anatolia, Turkey. Mount Erenler is the largest part of Central Anatolia Volcanic Province and consists of Miocene-Pliocene calc-alkaline lavas together with pyroclastic rocks and covers an area approximately 2000 km2. The peak of the Mount Erenler is at 1900 m while Lake Dipsiz is located at 1600 m altitude. Despite the small surface area (0.33 km2), the depth is relatively high (16 m). The drainage area of the lake is 8 km2. Although the topography of the lake points out to glacier presence, it formed as a landslide-dammed lake. Lake Dipsiz geographically is between mountainous Mediterranean region and Central Anatolia plateau. Climatically, the lake is in a transition zone between Taurids and Central Anatolia. In this study, we investigated sedimentation in a high altitude lake at a climatic transition. For this purpose, three cores (D1, D2 and D3) which are 50 cm length are taken with a hand corer from the coastline of the lake. D1 and D2 cores are sampled in every 2 cm and D3 core is samples in every 1 cm. Geochemical, total organic carbon, magnetic susceptibility and total carbonate analyses were performed on all sample sets. Lake sediments are brownish/green clay and silt in composition. Despite the proximity of the sediment source, no sand or more coarse grains were observed in the sedimentary filling. Organic matter content is between 2 - 28 %. According to one 14C date, the sequence indicates a Late Holocene age. δ13C isotope values are between -28.9 and -25.3 ‰ and it means that the sediment composed of terrestrial C3 organic matter. The detrital input in the lake has increased in the last 1000 years. Sedimentation rate was low between 3000 and cal. 1700 BP to the contrary of significant increasing from 250 BP to nowadays. Our data show that the sedimentation in this high altitude lake is more sensitive to other environmental conditions rather than climate.

  14. Escherichia Coli monitoring in the Spring Mill Lake watershed in south-central Indiana

    USGS Publications Warehouse

    Hasenmueller, N.R.; Comer, J.B.; Zamani, D.D.; ,

    2003-01-01

    The escherichila (E) coli monitoring in the Spring Mill lake watershed in South-Central Indiana was presented. Water flowing from the springs in the park were analyzed to determine potential nonpoint-source contaminants entering Spring Mill Lake. E. Coli concentrations from the monitoring sites within the Spring Mill Lake watersheds varied greatly from concentrations below the detection limit, <1 most probable number (MPN) of organisms per 100 milliliters (mL) of water, to 980,000 MPN/100 mL. E. coli appears to be a potential health risk at several of the springs within the park, particularly at the Rubble site.

  15. Composition, Diversity, and Stability of Microbial Assemblages in Seasonal Lake Ice, Miquelon Lake, Central Alberta

    PubMed Central

    Bramucci, Anna; Han, Sukkyun; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2013-01-01

    The most familiar icy environments, seasonal lake and stream ice, have received little microbiological study. Bacteria and Eukarya dominated the microbial assemblage within the seasonal ice of Miquelon Lake, a shallow saline lake in Alberta, Canada. The bacterial assemblages were moderately diverse and did not vary with either ice depth or time. The closest relatives of the bacterial sequences from the ice included Actinobacteria, Bacteroidetes, Proteobacteria, Verrucomicrobia, and Cyanobacteria. The eukaryotic assemblages were less conserved and had very low diversity. Green algae relatives dominated the eukaryotic gene sequences; however, a copepod and cercozoan were also identified, possibly indicating the presence of complete microbial loop. The persistence of a chlorophyll a peak at 25–30 cm below the ice surface, despite ice migration and brine flushing, indicated possible biological activity within the ice. This is the first study of the composition, diversity, and stability of seasonal lake ice. PMID:24832796

  16. Anthropogenic changes in Lake Korttajärvi, central Finland, during the last 400 years

    NASA Astrophysics Data System (ADS)

    Kehusmaa, Karoliina; Tammelin, Mira; Saarinen, Timo; Varjo, Eila

    2016-04-01

    Many European lakes have been heavily affected by human activity. These human-induced changes often relate to the post-1850s industrialization and modern agriculture. Lake sediments record these changes as variation in the physical and chemical properties of the sediment and in the species assemblages of the biological remains that are preserved in the sediment. In addition, anoxic conditions at the bottom of deep lake basins allow the formation of varved lake sediments. These can be inexpensively and rapidly used for dating the changes recorded in the sediment. Therefore, varved lakes are excellent archives for examining environmental change and the effect of humans on lakes. In this study, we investigated the human-induced changes in the varved Lake Korttajärvi in central Finland during the last 400 years. The sediment core was dated by varve counting to the year 1600 CE and divided into subsamples covering 10 years. From each subsample, we determined the sediment total phosphorus (S-TP), identified diatoms, examined their species turnover with multivariate analysis, and reconstructed the diatom-inferred total phosphorus (DI-TP) values of the past lake water. Three different phosphorus fractions will also be determined from the subsamples. In addition, the magnetic susceptibility (MS) of the whole core was measured prior to subsampling. According to our preliminary results, a constant diatom species turnover in Lake Korttajärvi started in the 1840s. However, the most notable anthropogenic deterioration phase was from the 1920s to the 1970s. During that time period catchment erosion and DI-TP increased, planktonic diatoms became more abundant in relation to benthic diatoms, and S-TP decreased. In the 1970s, municipal waste water treatment reduced nutrient loading into the lake. This started a recovery phase during which an opposite trend in these parameters can be observed. Currently, the diatom assemblage in Lake Korttajärvi resembles those of the early 20th

  17. Excess warming of a Central European lake driven by solar brightening

    NASA Astrophysics Data System (ADS)

    Schmid, M.; Köster, O.

    2016-10-01

    Recent trends in summer surface temperatures of many lakes exceed the corresponding air temperature trends. This disagrees with expectations from lake surface heat budgets, which predict that lake surface temperatures should increase by 75-90% of the increase in air temperatures. Here we investigate the causes for this excess warming for Lower Lake Zurich, a representative deep and stratified Central European lake, by a combined data analysis and modeling approach. Lake temperatures are simulated using a one-dimensional vertical model driven by 33 years of homogenized meteorological data. The model is calibrated and validated using an equally long time series of monthly water temperature profiles. The effects of individual forcing parameters are investigated by scenarios where the trends of single variables are retained while those of all other forcing variables are removed. The results show that ˜60% of the observed warming of spring and summer lake surface temperatures were caused by increased air temperature and ˜40% by increased solar radiation. The effects of the trends of all other forcing variables were small. Following projections of climate models, the increasing trends in solar radiation, and consequently the excess warming of lake surface temperatures, are not likely to continue in the future.

  18. Mining, metallurgy and the historical origin of mercury pollution in lakes and watercourses in Central Sweden.

    PubMed

    Bindler, Richard; Yu, Ruilian; Hansson, Sophia; Classen, Neele; Karlsson, Jon

    2012-08-07

    In Central Sweden an estimated 80% of the lakes contain fish exceeding health guidelines for mercury. This area overlaps extensively with the Bergslagen ore region, where intensive mining of iron ores and massive sulfide ores occurred over the past millennium. Although only a few mines still operate today, thousands of mineral occurrences and mining sites are documented in the region. Here, we present data on long-term mercury pollution in 16 sediment records from 15 lakes, which indicate that direct release of mercury to lakes and watercourses was already significant prior to industrialization (lakes show increases in mercury from 3-fold-equivalent to the enrichment factor in many remote lakes today-to as much as 60-fold already during the period AD 1500-1800, with the highest values in the three lakes most closely connected to major mines. Although the timing and magnitude of the historical increases in mercury are heterogeneous among lakes, the data provide unambiguous evidence for an incidental release of mercury along with other mining metals to lakes and watercourses, which suggests that the present-day problem of elevated mercury concentrations in the Bergslagen region can trace its roots back to historical mining.

  19. An earthquake study in the Lake Baringo basin of the central Kenya Rift

    NASA Astrophysics Data System (ADS)

    Tongue, Jane; Maguire, Peter; Burton, Paul

    1994-09-01

    A 100 × 80 km 2 earthquake recording network was operated for three months (January-March 1990) in the Lake Baringo region of the Kenya Rift Valley. Twenty-nine seismic sites were occupied by short-period stations over a region including the Elgeyo escarpment, the Kerio Valley, the Tugen Hills and Lake Baringo itself. Eighty local events of ML < 2.0 have been located within 50 km of the network. These events are situated within the central part of the rift, showing some association with the main rift faults but mainly clustering beneath Lake Baringo at a depth of about 5 km and occurring as swarm activity. Ninety percent of the events occurred at depths shallower than 12 km. The brittle-ductile transition zone in this area is determined at a depth of 12-16 km, similar to that in the Lake Bogoria area immediately to the south. A preliminary study of focal mechanisms of suitable events indicates WNW-ESE extension across the Lake Baringo basin and suggests the presence of sub-vertical rupture surfaces beneath the lake. These may be caused by the insertion of basic dykes into the upper crust, and the rupture process assisted by high temperature and pressure geothermal fluids. The inversion of local P-wave arrival time data for the upper crustal velocity structure beneath Lake Baringo identifies a low-velocity zone beneath surface geothermal activity, a relationship previously demonstrated for the Lake Bogoria region.

  20. Regression Analysis of Stage Variability for West-Central Florida Lakes

    USGS Publications Warehouse

    Sacks, Laura A.; Ellison, Donald L.; Swancar, Amy

    2008-01-01

    -water exchange in controlling the stage of karst lakes in Florida. Regression equations were used to predict lake-stage variability for the recent period for 12 additional lakes, and the median difference between predicted and observed values ranged from 11 to 23 percent. Coefficients of determination for the historical period were considerably lower (maximum R2 of 0.28) than for the recent period. Reasons for these low R2 values are probably related to the small number of lakes (20) with stage data for an equivalent time period that were unaffected by ground-water pumping, the similarity of many of the lake types (large surface-water drainage lakes), and the greater uncertainty in defining historical basin characteristics. The lack of lake-stage data unaffected by ground-water pumping and the poor regression results obtained for that group of lakes limit the ability to predict natural lake-stage variability using this method in west-central Florida.

  1. Magnetic properties of lake sediments from Lake Chalco, central Mexico, and their palaeoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Ortega Guerrero, Beatriz; Thompson, Roy; Urrutia Fucugauchi, Jaime

    2000-02-01

    Lake Chalco (99.0°W, 19.5°N) in the Basin of Mexico, was formed during the Pleistocene after the emplacement of the Chichinautzin volcanic field that closed the former drainage system. The lake sediment record has been influenced by a number of factors, including glacial-interglacial cycles, local volcanism, erosion of soils and anthropogenic disturbances. The magnetic properties of the lake sediments and the associated tephra layers of the last 16500 yr have been studied. It is found that the magnetic properties of the Lake Chalco sediments are very distinctive. Magnetic concentration varies by a factor of 1000 and magnetic stability also varies over an extremely wide range. The predominant magnetic mineral is titanomagnetite in addition to an imperfect antiferromagnetic phase, possibly goethite. An unusually large range of coercivities is found in certain of the tephras. Down-core variations in magnetic properties closely follow climatic/environmental changes previously established by other proxy methods. The late Pleistocene and late Holocene lake sediments display a higher concentration of magnetic minerals than the early-middle Holocene sediments. In the non-volcanic sediments, fluctuations in the magnetic concentration reflect changes in both the intensity of erosion, as represented by ferrimagnetic and paramagnetic minerals, and by the maturing of soils, as represented by geothite.

  2. Exposure and effects of perfluoroalkyl compounds on tree swallows nesting at Lake Johanna in east central Minnesota, USA

    USGS Publications Warehouse

    Custer, Christine M.; Custer, Thomas W.; Schoenfuss, Heiko L.; Poganski, Beth H.; Solem, Laura

    2012-01-01

    Tree swallow (Tachycineta bicolor) samples were collected at a reference lake and a nearby lake (Lake Johanna) in east central Minnesota, USA contaminated with perfluorinated carboxylic and sulfonic acids. Tissues were analyzed for a suite of 13 perfluoroalkyl compounds (PFCs) to quantify exposure and to determine if there was an association between egg concentrations of PFCs and reproductive success of tree swallows. Concentrations of perfluoroocatane sulfonate (PFOS) were elevated in all tree swallow tissues from Lake Johanna compared to tissues collected at the reference lake. Other PFCs, except for two, were elevated in blood plasma at Lake Johanna compared to the reference lake. PFOS was the dominant PFC (>75%) at Lake Johanna, but accounted for <50% of total PFCs at the reference lake. There was a negative association between concentrations of PFOS in eggs and hatching success. Reduced hatching success was associated with PFOS levels as low as 150 ng/g wet weight.

  3. The water balance equations in saline playa lakes: comparison between experimental and recent data from Quero Playa Lake (central Spain)

    NASA Astrophysics Data System (ADS)

    Sánchez-Moral, S.; Ordóñez, S.; Benavente, D.; García del Cura, M. A.

    2002-04-01

    The Quero Playa Lake is an ephemeral saline playa lake located in the La Mancha region of central Spain. In this study, a daily monitoring of the brine physical properties, water activity, brine depth and main climatic parameters was simultaneously carried out together with determining the precipitation sequence of minerals. Field data were compared with the results of simulating the water evaporation in an environmental chamber. In this simulation, a similar hydrochemical composition for the saline lake was used, and the main climatic parameters, temperature and humidity, were controlled. The water balance equation for saline lakes has usually been described using the Wood and Sanford equation [Econ. Geol., 85(1990) 1226-1235]. Our experimental results required us to revise the water balance equation for the brine depth variations (d h/d t), that may be expressed as follows: {dh }/{dt }=p 1+k {A B}/{A L}+S I-S O-ξ-H+D, where p (mm) is the precipitation; k is the drainage coefficient of the lake; AL is the lake surface; AB is the drainage basin surface; SI and SO are the contribution of influent and effluent seepage to the depth of brine in the lake. The term ξ is the evaporation/condensation, defined as ξ= kpW( aW-RH), where k is the mass transfer coefficient (Dalton's equation); pW is the water pressure in equilibrium with the air; aW is the water activity of the brine; RH is the relative humidity. The other terms: H and D, correct the brine depth loss or/and gain a consequence of hydrated saline mineral precipitation and early diagenetic hydration/dehydration reactions. As a consequence of the above, we suggest that the water balance equation for saline lakes can be an important consideration in the interpretation of their evolution. The precipitation of hydrated saline minerals and the early diagenetic dehydration/hydration reactions imply changes in the d h/d t curves. As a result, the interpretation of the sequence of primary saline minerals in older

  4. The relative influences of climate and volcanic activity on Holocene lake development inferred from a mountain lake in central Kamchatka

    NASA Astrophysics Data System (ADS)

    Self, A. E.; Klimaschewski, A.; Solovieva, N.; Jones, V. J.; Andrén, E.; Andreev, A. A.; Hammarlund, D.; Brooks, S. J.

    2015-11-01

    A sediment sequence was taken from a closed, high altitude lake (informal name Olive-backed Lake) in the central mountain range of Kamchatka, in the Russian Far East. The sequence was dated by radiocarbon and tephrochronology and used for multi-proxy analyses (chironomids, pollen, diatoms). Although the evolution of Beringian climate through the Holocene is primarily driven by global forcing mechanisms, regional controls, such as volcanic activity or vegetation dynamics, lead to a spatial heterogeneous response. This study aims to reconstruct past changes in the aquatic and terrestrial ecosystems and to separate the climate-driven response from a response to regional or localised environmental change. Radiocarbon dates from plant macrophytes gave a basal date of 7800 cal yr BP. Coring terminated in a tephra layer, so sedimentation at the lake started prior to this date, possibly in the early Holocene following local glacier retreat. Initially the catchment vegetation was dominated by Betula and Alnus woodland with a mosaic of open, wet, aquatic and semi-aquatic habitats. Between 7800 and 6000 cal yr BP the diatom-inferred lake water was pH 4.4-5.3 and chironomid and diatom assemblages in the lake were initially dominated by a small number of acidophilic/acid tolerant taxa. The frequency of Pinus pumila (Siberian dwarf pine) pollen increased from 5000 cal yr BP and threshold analysis indicates that P. pumila arrived in the catchment between 4200 and 3000 cal yr BP. Its range expansion was probably mediated by strengthening of the Aleutian Low pressure system and increased winter snowfall. The diatom-inferred pH reconstructions show that after an initial period of low pH, pH gradually increased from 5500 cal yr BP to pH 5.8 at 1500 cal yr BP. This trend of increasing pH through the Holocene is unusual in lake records, but the initially low pH may have resulted directly or indirectly from intense regional volcanic activity during the mid-Holocene. The chironomid

  5. Water Quality and Evaluation of Pesticides in Lakes in the Ridge Citrus Region of Central Florida

    USGS Publications Warehouse

    Choquette, Anne F.; Kroening, Sharon E.

    2009-01-01

    Water chemistry, including major inorganic constituents, nutrients, and pesticide compounds, was compared between seven lakes surrounded by citrus agriculture and an undeveloped lake on the Lake Wales Ridge (herein referred to as the Ridge) in central Florida. The region has been recognized for its vulnerability to the leaching of agricultural chemicals into the subsurface due to factors including soils, climate, and land use. About 40 percent of Florida's citrus cultivation occurs in 'ridge citrus' areas characterized by sandy well drained soils, with the remainder in 'flatwoods citrus' characterized by high water tables and poorly drained soils. The lakes on the Ridge are typically flow-through lakes that exchange water with adjacent and underlying aquifer systems. This study is the first to evaluate the occurrence of pesticides in lakes on the Ridge, and also represents one of the first monitoring efforts nationally to focus on regional-scale assessment of current-use pesticides in small- to moderate-sized lakes (5 to 393 acres). The samples were collected between December 2003 and September 2005. The lakes in citrus areas contained elevated concentrations of major inorganic constituents (including alkalinity, total dissolved solids, calcium, magnesium, sodium, potassium, chloride, and sulfate), total nitrogen, pH, and pesticides compared to the undeveloped lake. Nitrate (as N) and total nitrogen concentrations were typically elevated in the citrus lakes, with maximum values of 4.70 and 5.19 mg/L (milligrams per liter), respectively. Elevated concentrations of potassium, nitrate, and other inorganic constituents in the citrus lakes likely reflect inputs from the surficial ground-water system that originated predominantly from agricultural fertilizers, soil amendments, and inorganic pesticides. A total of 20 pesticide compounds were detected in the lakes, of which 12 compounds exceeded the standardized reporting level of 0.06 ug/L (microgram per liter). Those

  6. Monitoring variations of inland lakes in the arid region of Central Asia

    NASA Astrophysics Data System (ADS)

    Bai, Jie; Chen, Xi; Yang, Liao; Fang, Hui

    2012-06-01

    Inland lakes are the major surface water resource in the arid regions of Central Asia. Therefore, the surface area changes in inland lakes have been a sensitive indicator of climate changes and human activities, and have often been the focus of ecological and environmental research. This study aimed to monitor the changes in surface area of nine major lakes over a 32-year period. The water body was extracted from MSS images from the mid-1970s, TM images from the early 1990s, ETM + images in the late 1990s, and TM images in 2007. The results indicated that the total surface area of these nine lakes had decreased over time to 50.38% of the area, from 91402.06 km2 in 1975 to 46049.23 km2 in 2007. As the surface area of lakes in the western part of Central Asia was larger than that in the eastern part, the shrinking trend of lake area was more significant in the west than in the east. There was a varied reduction of closed lakes in flat regions. The most substantial decrease was in the surface area of closed lakes in flat regions. Most significantly, the area of the Aral Sea was reduced by 75.7% from its original area in 1975. The area of alpine lakes remained relatively stable; the change in surface area was less than 0.7% during the period 1975-2007. The area change in opened lakes with outlets was notably different from the other two types. The area of Zaysan had increased sharply by 5.85%, and that of Bosten had decreased by 9.1%. Sasykkol had hardly any changes in this period. Due to global climate warming, vapor transfer to the south via westerly winds had been blocked, resulting in a decrease of much-needed precipitation in the western parts of Turkmenistan, Uzbekistan, and Kazakhstan between 1970 and 2000. The decrease in precipitation and the increase in water consumption for agricultural irrigation resulted in the decrease of river runoff. Consequently, the area of inland lakes in Central Asia shrank over the past 32 years.

  7. Magnetic and gravity studies of Mono Lake, east-central, California

    USGS Publications Warehouse

    Athens, Noah D.; Ponce, David A.; Jayko, Angela S.; Miller, Matt; McEvoy, Bobby; Marcaida, Mae; Mangan, Margaret T.; Wilkinson, Stuart K.; McClain, James S.; Chuchel, Bruce A.; Denton, Kevin M.

    2014-01-01

    From August 26 to September 5, 2011, the U.S. Geological Survey (USGS) collected more than 600 line-kilometers of shipborne magnetic data on Mono Lake, 20 line-kilometers of ground magnetic data on Paoha Island, 50 gravity stations on Paoha and Negit Islands, and 28 rock samples on Paoha and Negit Islands, in east-central California. Magnetic and gravity investigations were undertaken in Mono Lake to study regional crustal structures and to aid in understanding the geologic framework, in particular regarding potential geothermal resources and volcanic hazards throughout Mono Basin. Furthermore, shipborne magnetic data illuminate local structures in the upper crust beneath Mono Lake where geologic exposure is absent. Magnetic and gravity methods, which sense contrasting physical properties of the subsurface, are ideal for studying Mono Lake. Exposed rock units surrounding Mono Lake consist mainly of Quaternary alluvium, lacustrine sediment, aeolian deposits, basalt, and Paleozoic granitic and metasedimentary rocks (Bailey, 1989). At Black Point, on the northwest shore of Mono Lake, there is a mafic cinder cone that was produced by a subaqueous eruption around 13.3 ka. Within Mono Lake there are several small dacite cinder cones and flows, forming Negit Island and part of Paoha Island, which also host deposits of Quaternary lacustrine sediments. The typical density and magnetic properties of young volcanic rocks contrast with those of the lacustrine sediment, enabling us to map their subsurface extent.

  8. Water quality of Somerville Lake, south-central Texas

    USGS Publications Warehouse

    McPherson, Emma; Mendieta, H.B.

    1983-01-01

    The concentration of dissolved solids ranged from 139 to 292 milligrams per liter and averaged about 220 milligrams per liter. Dissolved chloride concentrations ranged from 20 to 68 milligrams per liter and averaged 43 milligrams per liter. Dissolved sulfate concentrations ranged from 30 to 130 milligrams per liter and averaged 63 milligrams per liter. The total hardness of the water ranged from 75 to 140 milligrams per liter, expressed as calcium carbonate, placing it in the moderately hard to hard (61 to 180 milligrams per liter) classification. The concentrations of principal dissolved constituents indicate that Somerville Lake is an excellent source of water for municipal, industrial, or agricultural use.

  9. Hydrologic reconnaissance of the Sevier Lake area, west-central Utah

    USGS Publications Warehouse

    Wilberg, Dale E.

    1991-01-01

    The hydrologic system of the Sevier Lake area, at the terminus of the Sevier Lake drainage basin in west-central Utah, was studied during 1987-88 to determine baseline hydrologic conditions prior to anticipated development.  Sevier Lake was reestablished during 1983-87 on the normally dry playa as a result of record volumes of surface-water runoff, but the lake was receding during the study.  In June 1985, the lake reached a maximum depth of about 13 feet, with a water-surface altitude of 4,527 feet above sea level.The basin-fill aquifer includes a coarse-grained facies at higher altitudes of the alluvial slopes, and a fine-grained facies at lower altitudes around Sevier Lake.  Water levels indicate a potential for lateral groundwater movement away from the lake and toward the northwest, west, and south.Transmissivity of the coarse-grained facies, determined from one well, was 4,120 feet squared per day. Transmissivity values for the fine-grained facies ranged from 1 X 10-3 to 5 X 10-2 foot squared per day, determined from slug tests of shallow wells near the shoreline of the lake, and 5.2 feet squared per day determined from a well in the lakebed.The predominant constituents of water sampled in the Sevier Lake area are sodium, sulfate, and chloride. The concentration of dissolved solids ranges from 480 to 120,000 milligrams per liter. Smaller concentrations of dissolved solids were determined for water from wells completed in the coarse-grained facies, and larger concentrations were determined for water from wells completed in the fine-grained facies.

  10. Sublacustrine precipitation of hydrothermal silica in rift lakes: evidence from Lake Baringo, central Kenya Rift Valley

    NASA Astrophysics Data System (ADS)

    Renaut, R. W.; Jones, B.; Tiercelin, J.-J.; Tarits, C.

    2002-04-01

    Many lakes in volcanic regions are fed by hot springs that, in some basins, can contribute a large percentage of the annual recharge, especially during times of aridity. It is important to recognize any contemporary hydrothermal contribution in paleoenvironmental reconstruction of lake basins because recharge from thermal waters can potentially confuse paleoclimatic signals preserved in the lacustrine sedimentary record. Hot spring deposits (travertine, sinter) provide the most tangible evidence for thermal recharge to lakes. Although subaerial spring deposits have been widely studied, lacustrine thermal spring deposits, especially sublacustrine siliceous sinters, remain poorly known. Detailed field, petrographic and scanning electron microscope (SEM) studies have been made of fossil sublacustrine sinter exposed at Soro hot springs along the northeastern shoreline of Ol Kokwe, a volcanic island in Lake Baringo, Kenya. Modern hot springs at Soro, which discharge Na-HCO 3-Cl waters from a deep reservoir (˜180 °C ), have thin (1-10 mm), friable microbial silica crusts around their subaerial vents, but thicker (>1 cm) sinter deposits are not forming. The fossil sinter, which is present as intergranular cements and crusts in littoral conglomerates and sandstones, is composed mainly of opaline silica (opal-A). Three types of fossil sinter are recognized: (1) massive structureless silica, which fills intergranular pores and forms crusts up to 5 cm thick; (2) pore-lining silica, some of which is isopachous, and (3) laminated silica crusts, which formed mainly on the upper surfaces of detrital particles. All three types contain well-preserved diatoms including lacustrine planktonic forms. Microbial remains, mainly filamentous and coccoid bacteria (including cyanobacteria) and extracellular polymeric gels, are locally abundant in the opaline silica, together with detrital clays and thin laminae composed of authigenic chlorite (?). Most of the hydrothermal silica

  11. Human Impact on Biogeochemical Cycles and Deposition Dynamics in Karstic Lakes: El Tobar Lake Record (Central Iberian Range, Spain)

    NASA Astrophysics Data System (ADS)

    Barreiro-Lostres, F.; Moreno-Caballud, A.; Giralt, S.; Hillman, A. L.; Brown, E. T.; Abbott, M. B.; Valero-Garces, B. L.

    2014-12-01

    Karstic lakes in the Iberian Range (Central Spain) provide a unique opportunity to test the human impact in the watersheds and the aquatic environments during historical times. We reconstruct the depositional evolution and the changes in biogeochemical cycles of El Tobar karstic lake, evaluating the response and the resilience of this Mediterranean ecosystem to both anthropogenic impacts and climate forcing during the last 1000 years. Lake El Tobar (40°32'N, 3°56'W; 1200 m a.s.l.; see Figure), 16 ha surface area, 20 m max. depth and permanent meromictic conditions, has a relatively large watershed (1080 ha). Five 8 m long sediment cores and short gravity cores where recovered, imaged, logged with a Geotek, described and sampled for geochemical analyses (elemental TOC, TIC, TN, TS), XRF scanner and ICP-MS, and dated (137Cs and 10 14C assays). The record is a combination of: i) laminated dark silts with terrestrial remains and diatoms and ii) massive to banded light silts (mm to cm -thick layers) interpreted as flood deposits. Sediments, TOC, and Br/Ti and Sr/Ca ratios identify four periods of increased sediment delivery occurred about 1500, 1800, 1850 and 1900 AD, coinciding with large land uses changes of regional relevance such as land clearing and increased population. Two main hydrological changes are clearly recorded in El Tobar sequence. The first one, marked by a sharp decrease in Mg, Ca and Si concentrations, took place about 1200 AD, and during a period of increasing lake level, which shifted from shallower to deeper facies and from carbonatic to clastic and organic-rich deposition. This change was likely related to increased water availability synchronous to the transition from the Medieval Climate Anomaly to the Little Ice Age. The second one was a canal construction in 1967 AD when a nearby reservoir provided fresh water influx to the lake, and resulted in stronger meromictic conditions in the system after canal construction, which is marked by lower

  12. Late Pleistocene/Holocene paleoclimate reconstruction and eruptive history of Central American volcanoes from lake bottom sediments of Lake Nicaragua

    NASA Astrophysics Data System (ADS)

    Wulf, S.; Dull, R. A.; Mann, P.; McIntosh, K. D.; Gardner, J. E.

    2007-12-01

    A shallow coring program in Lake Nicaragua was completed in May/June 2006 by the University of Texas (UT Department of Geography and UT Institute for Geophysics). A total of 35 sediment cores with lengths ranging between 12 cm and 100 cm along with five longer cores were extracted from the lake using a gravity corer and a modified manual square rod piston corer, respectively. Analyses of lake sediments have the following objectives: 1) to correlate the geophysical results with the core data to provide a stratigraphic framework for the shallow lake sediments; 2) to constrain past climate variability in this rather poorly investigated area; and 3) to establish a time series of explosive volcanic activity based on the identification and dating of tephra layers in the cores. Initial measurements of magnetic susceptibility, dry density, loss on ignition and XRF scanning indicated a dominance of fine-grained homogeneous diatomaceous sediments cover most of the lake floor. Increasing values in magnetic susceptibility in the upper part of several short cores most likely reflect increased erosion caused by land-use changes during the Spanish colonial period (1522-1822). Results on the two longest cores from the northeastern (355 cm) and southwestern (478 cm) parts of the lake reveal complete Holocene paleoclimate records in both areas that are comparable to other terrestrial and marine records in the Central and South- American tropics (i.e. Cariaco Basin). A lithologic change from homogeneous gyttia (diatomaceous mud) to blue- grayish waxy clay at the bottom of these records marks the Late Pleistocene-Holocene transition as indicated by a radiocarbon dating on plant remains. The latter dense clay forms a distinctive stratigraphic marker in the lake basin. Tephra layers to date were detected in most gravity cores recovered west of Ometepe Island (Volcan Concepcion), and in long records in the northeastern basin (San Antonio Tephra, Masaya volcano, ca. 7,400 interpolated cal

  13. Hydrologic data; North Canadian River from Lake Overholser to Lake Eufaula, central Oklahoma

    USGS Publications Warehouse

    Havens, J.S.

    1984-01-01

    The data contained in this report were gathered during the period 1982 to 1984 for use in constructing a digital model of the North Canadian River from Lake Overholser, in the western part of Oklahoma City, to Lake Eufaula, in eastern Oklahoma. Locations of test holes and sampling sites are show in figure 1. Information on well depths and water levels in table 1 was gathered in the summer of 1982. Some information in the table was reported by well owners. Field water-quality data for water temperatures, specific conductance, and pH were measured at the time the wells were inventoried in 1982 and appear in table 2. Forty-nine test holes were augered to provide more comprehensive lithologic and water-level data along the North Canadian River. Lithologic logs of these test holes appear in table 3. Thirty-eight of the test holes were completed as observations wells by placing perforated plastic casing in the holes. Water levels were measured in these observations wells from the time of completion in mid-1982 through mid-1984. Hydrographs of the observation wells are shown in figures 2 through 15. The data are presented graphically for clarity. Hydrographs of water-level fluctuations in two wells equipped with continuous water-level recorders and hydrographs of stage fluctuations on the North Canadian River at nearby gaging stations are shown in figures 16 and 17. Two sets of low-flow measurements for the North Canadian River showing gains and losses in flow between measuring sites in the reach from Lake Overholser to Lake Eufaula are given in table 4. Measurements of flow on tributary streams are also given in this table. Analyses of water-quality samples collected at the time of the low-flow measurements are given in table 5.

  14. Stable carbon and nitrogen isotopes and amino acids in Holocene sediments of Lake Lonar, central India

    NASA Astrophysics Data System (ADS)

    Menzel, Philip; Gaye, Birgit; Wiesner, Martin; Basavaiah, Nathani; Prasad, Sushma; Stebich, Martina; Anoop, Ambili; Riedel, Nils

    2013-04-01

    Investigations on surface sediments and a sediment core from Lake Lonar in central India were carried out within the framework of the HIMPAC (Himalaya: Modern and Past Climate) programme. The aim was to understand recent productivity, sedimentation, and degradation processes and to reconstruct variations in Holocene lake conditions on the basis of biogeochemical analysis on a 10 m long sediment core retrieved from the centre of Lake Lonar. Located in India's core monsoon zone, Lake Lonar offers valuable information about the climate development of the whole region. The lake is situated at the floor of a meteorite impact structure on the Deccan plateau basalt. The modern lake is characterised by brackish water, high alkalinity, severe eutrophication, and bottom water anoxia. The lake is about 6 m deep and fed by rainfall during the SW monsoon season and three perennial streams. Since no out-flowing stream is present and no seepage loss occurs, the lake level is highly sensitive to the balance of precipitation and evaporation. Here we present C/N, carbon and nitrogen isotope, and amino acid data of bulk organic matter from modern lake and Holocene core sediments. Modern conditions are mainly related to human activity which started to have persistent influence on the biological and chemical lake properties at ~1200 cal a BP. The distribution of δ13C in the modern sediments is driven by the ratio between terrestrial and aquatic organic matter, while δ15N seems to be influenced by redox conditions at the sediment-water-interface with elevated values at shallow oxic stations. Differences in the amino acid assemblages of oxic and anoxic surface sediment samples were used to calculate an Ox/Anox ratio indicating the redox conditions during organic matter degradation. The onset of the monsoon reconstructed from the sediment core occurred at ca. 11450 cal a BP. The early Holocene core sediments are characterised by low sedimentation rate, low aquatic productivity, and

  15. Size, distribution and evolution of thermokarst lakes in Central Yakutia, Russia

    NASA Astrophysics Data System (ADS)

    Ulrich, M.; Iijima, Y.; PARK, H.; Fedorov, A. N.

    2015-12-01

    The permafrost landscape of Central Yakutia is subject to rapid modifications as a result of intensive land use, extreme weather, and the current global warming. With regard to the predicted increase in precipitation and temperature due to climate change, quantitative knowledge of the small-scale variability of active thermokarst processes is required. Here, we analyzed size and frequency distribution of lakes >0.1ha on different geomorphological ice-rich permafrost terraces east of Yakutsk using Landsat 8 data and we mapped the change of thermokarst and alas lakes since 1944 at the Yukechi study site using historical airborne and current satellite data and analyzed growth rates and thaw subsidence. Generally, larger lakes in higher frequency are dominating lower and younger terraces, while higher and older terraces are dominated by smaller lakes. In particular, smaller lakes in less density are distributed on older and more ice-rich terraces while the younger and less ice-rich terraces are characterized by highest lake densities and larger lakes. Remote sensing analysis at the Yukechi study site indicate that lake-level changes of residual alas lakes during the past 70 years were mainly affected by the winter precipitation and the annual water balance. In the meanwhile, extensive agricultural use in the post-war period led to the disturbance of the thermal and hydrological balance of the permafrost and results in rapid and sustained growth of young thermokarst lakes on undegraded ice-rich permafrost deposits. Climatic parameters, however, are affecting only growing rates within certain time periods. The mean growth rate of all mapped thermokarst lakes at Yukechi is 0.8 ±0.6 m a-1, with a mean thaw subsidence of 7.0 ±1.6 cm a-1. Our results indicate that topography, geomorphology, and surficial cryolithology are important controlling factors on the distribution of lakes. Furthermore, thermokarst activity is influenced by climatic parameters but it is accelerated

  16. Monitoring of Bashkara glacial lakes (the Central Caucasus) and modelling of their potential outburst.

    NASA Astrophysics Data System (ADS)

    Krylenko, I.; Norin, S.; Petrakov, D.; Tutubalina, O.; Chernomorets, S.

    2009-04-01

    In recent decades due to glacier retreat the glacial lakes in the Central Caucasus, as well as in other high-mountainous areas of the world, have expanded intensively. As result the risk of lake outbursts and destructive floods is raising. In this paper we present one of the most potentially hazardous lakes of this region - a group of glacial lakes near the Bashkara glacier in the upper Adylsu river valley, to the southeast of Mt. Elbrus. Total area of these lakes is about 100,000m2, and a total volume exceeds 1,000,000 m3. The biggest of them - the Bashkara lake has formed in late 1930s - early 1940s and the small Lapa lake has appeared in the end of 1980s. The Bashkara lake outburst occurred twice in the end of 1950s and produced devastating debris flows of ca. 2 million m3. We have monitored these lakes since 1999. Our work includes detailed field research: constant measurements of water level during warm period, annually repeated bathymetric surveys, geodetic surveys, observations on dam condition and some special measurements (i.e. water temperature distribution, current velocity). Also we use aerial and satellite images to obtain data about dynamic of areas for the lakes. From 2001 to 2006 years volume of the Lapa lake has increased 5 times (from 30,000 m3 to 140,000 m3), the Bashkara lake in this period was quasi-stable. In 2006-2008 volume of the Lapa lake has decreased due to sedimentation, however, rapid growth of water level in Bashkara lake (more than 20 sm. per day) has suddenly begun. As a result, volume of the Bashkara lake exceeded 1,000000 m3 in July 2008 whereas in 2001 -2007 year it was about 800,000 m3. Previous maximum of water level was exceeded on 3,5 m, moraine dam with ice core was overtopped and overflow has started. Thus, Bashkara glacier lakes are unstable and risk of outburst is increasing. To assess parameters and zones of potential outburst flood in the Adylsu River valley we have carried out hydrodynamic simulation. Two computer

  17. Sedimentary Evidence of Environmental Degradation in Sanliqi Lake, Daye City (A Typical Mining City, Central China).

    PubMed

    Zeng, Linghan; Ning, Dongliang; Xu, Lei; Mao, Xin; Chen, Xu

    2015-09-01

    To reconstruct the history of environmental degradation in Sanliqi Lake (Daye City, central China), multiple proxies were analyzed in a sedimentary core which was dated using (137)Cs and spheroidal carbonaceous particles (SCPs). The results show that Sanliqi Lake has experienced serious degradation during the past 60 years, resulting from a large influx of metals and nutrients. Expansion of agricultural and industrial activities between 1945 and 1993 enhanced nutrient and metal enrichment, indicated by increases in metals, SCPs, magnetic susceptibility, total phosphorus, total nitrogen and total organic carbon. Further enrichment of Zn, Cd, Ni and Cr after 1993 was linked to a recent intensification of mining activities. Decreases in Cu and Pb after 2006 probably resulted from recent environmental remediation. This study verified the coupling between lake sediment pollution and human activities in Daye City during the past 60 years. The reconstructed history of lake pollution can provide reference information for continued restoration of Sanliqi Lake and other similar heavily polluted lakes in the developing regions.

  18. Sediment toxicity and deformities of chironomid larvae in Lake Piediluco (Central Italy).

    PubMed

    Di Veroli, Alessandra; Selvaggi, Roberta; Pellegrino, Roberto Maria; Goretti, Enzo

    2010-03-01

    The chemical analysis of the bottom sediments of the Lake Piediluco (Central Italy) has been carried out in order to individuate the potential correlation between the sediment toxicity and the high incidence of mouthpart deformities in chironomid larvae (biological indicators) found in this lake. The environmental contamination has been analyzed by determining the concentrations of the main heavy metals (lead, copper, cadmium, chromium, zinc and nickel), and the concentrations of organic compounds of anthropic source: PAHs, NPPs and OCPs. Heavy metals concentrations have pointed out a non-elevated contamination grade for the Lake Piediluco. The highest level of metals has been detected in the western area that feels the effect of the continuous tributaries incoming load. Also, concerning PAHs, NPPs and OCPs the lake does not present high values of pollution. The highest concentrations of the organic toxicants has been observed in the eastern sector of the lake, which presents typical lentic characteristics. A clear relationship has not found between the toxic substances present in the lacustrine sediments and the deformities incidence for chironomid larvae, which represent an index of environmental alteration. Probably, the mouthpart deformities found in the chironomid larvae of Chironomus plumosus are affected by a synergic action due to the whole toxic mixture present in the sediments of the Lake Piediluco. Copyright 2010 Elsevier Ltd. All rights reserved.

  19. Late Quaternary ostracode-based paleoenvironmental reconstructions from Lake Petén Itzá, Guatemala and Lake Chalco, central Mexico

    NASA Astrophysics Data System (ADS)

    Perez, L.; Lozano, S.; Caballero, M.; Brenner, M.; Schwalb, A.

    2013-05-01

    Modern and fossil ostracodes in lakes from central Mexico (Chalco) to lowland Guatemala (Petén Itzá) were used to infer paleoenvironmental conditions during the last 45 ka. Ostracode-based paleoenvironmental reconstruction from sediment cores in Lake Petén Itzá was based on a modern calibration data set from 63 water bodies in Guatemala, Mexico (Yucatán Peninsula) which provided information on the modern ecological preferences of 29 ostracode species. Statistical analysis indicated that lake water conductivity and chemical composition determine ostracode distributions on the Yucatán Peninsula and that lake level is a strong determinant of species distribution in Lake Petén Itzá. Transfer functions were applied to fossil species assemblages in long sediment cores from Lake Petén Itzá to infer past conductivity and lake level. Over the past 45 ka, ostracodes in Lake Petén Itzá were sensitive to fluctuations in lake water chemical composition and lake stage. Relative abundances of ostracode taxa and stable isotope values in their shells indicate large environmental changes from the LGM to deglaciation, and into the Holocene. The LGM was characterized by low species richness (n=4), dominance of benthic taxa, cold conditions and moderate to high lake levels. The deglaciation displayed higher species richness (n=6), dominance of nektobenthic taxa, and alternating dry and wet conditions, with low to relatively high lake levels. The Holocene was dominated by the deep-water ostracode Physocypria globula, indicating warmer temperatures and higher lake levels. Preliminary results from Lake Chalco sediment cores indicate ostracodes were scarce during the LGM and deglacial, but displayed higher abundances in older deposits. Ostracodes identified in the sediment record include Limnocythere sp., Candona patzcuaro and Darwinula stevensoni. The only species in common with the Lake Petén Itzá record is D. stevensoni. Deglacial species richness in Chalco (n=3) was lower

  20. Decadal and Seasonal Variations of Alpine Lakes in Glacierized areas of Central Asia during 1990-2015

    NASA Astrophysics Data System (ADS)

    Li, J.; Warner, T.; Chen, X.; Bao, A.

    2016-12-01

    Central Asia is one of the world's most vulnerable areas responding to global change. Glacier lakes in the alpine regions remain sensitive to climatic change and fluctuate with temperature and precipitation variations. Study shows that glaciers in Central Asia have retreated dramatically, leading to the expansion of the existing glacial lakes and the emergence of many new glacier lakes. The existence of these lakes increases the possibility of outburst flood during the ice melting season, which can bring a disaster to the downstream area. Mapping glacial lakes and monitoring their changes would improve our understanding of regional climate change and glacier-related hazards. Glacial lakes in Central Asia are mainly located at the Tianshan Mountains, the Altai Mountains, the Kunlun Mountains and the Pamirs with average elevation more than 1500 meters. Most of these lakes are supplied with the glaciers or snowmelt water during the summer seasons. Satellite remote sensing provides an efficient and objective tool to analyze the status and variations of glacial lakes. The increased availability of remote sensing sensors with appropriate spatial and temporal resolutions, broad coverage makes lake investigations more feasible and cost-effective. The paper intends to map glacier lake changes in glacierized alpine mountains with Landsat TM/ETM+ imagery. More than 600 scenes of Landsat images in circa 1990, circa 2000, circa 2010 and circa 2015 are used to map the decadal glacial lake changes over the Central Asia, and about 8 expanding glacial lakes are selected to map seasonal changes. Over 12000 glacial lakes were mapped in circa 1990, and in 2015, lake number are more than 16000, most of these new lakes are emerging in the last 10 years. The result shows that the number and area of the glacial lakes in the Altain Mountain remain stable, while the Tianshan Mountain have experienced expanding changes in the last two decades, and about a half number of lake areas are

  1. Tuffaceous ephemeral lake deposits on an alluvial plain, Middle Tertiary of central California

    USGS Publications Warehouse

    Bartow, J.A.

    1994-01-01

    The Oligocene and Miocene Valley Springs Formation represents a large fluvial depositional system that extended westward from sediment-filled palaeovalleys in the high Sierra Nevada to a piedmont alluvial plain under the present Central Valley. The Valley Springs Formation consists largely of tuffaceous mudrocks, tuffaceous sandstone, polymict conglomerate and rhyodacitic tuff. The tuffaceous mudrock lithofacies probably represents a complex of ephemeral lake and marsh environments on a low gradient alluvial plain. The inferred abundance of shallow lakes, ponds and marshes implies a climate that was wetter than the semi-arid climate of the region today. -from Author

  2. Estimating ground-water inflow to lakes in central Florida using the isotope mass-balance approach

    USGS Publications Warehouse

    Sacks, Laura A.

    2002-01-01

    The isotope mass-balance approach was used to estimate ground-water inflow to 81 lakes in the central highlands and coastal lowlands of central Florida. The study area is characterized by a subtropical climate and numerous lakes in a mantled karst terrain. Ground-water inflow was computed using both steady-state and transient formulations of the isotope mass-balance equation. More detailed data were collected from two study lakes, including climatic, hydrologic, and isotopic (hydrogen and oxygen isotope ratio) data. For one of these lakes (Lake Starr), ground-water inflow was independently computed from a water-budget study. Climatic and isotopic data collected from the two lakes were similar even though they were in different physiographic settings about 60 miles apart. Isotopic data from all of the study lakes plotted on an evaporation trend line, which had a very similar slope to the theoretical slope computed for Lake Starr. These similarities suggest that data collected from the detailed study lakes can be extrapolated to the rest of the study area. Ground-water inflow computed using the isotope mass-balance approach ranged from 0 to more than 260 inches per year (or 0 to more than 80 percent of total inflows). Steady-state and transient estimates of ground-water inflow were very similar. Computed ground-water inflow was most sensitive to uncertainty in variables used to calculate the isotopic composition of lake evaporate (isotopic compositions of lake water and atmospheric moisture and climatic variables). Transient results were particularly sensitive to changes in the isotopic composition of lake water. Uncertainty in ground-water inflow results is considerably less for lakes with higher ground-water inflow than for lakes with lower ground-water inflow. Because of these uncertainties, the isotope mass-balance approach is better used to distinguish whether ground-water inflow quantities fall within certain ranges of values, rather than for precise

  3. Changes in the area of inland lakes in arid regions of central Asia during the past 30 years.

    PubMed

    Bai, Jie; Chen, Xi; Li, Junli; Yang, Liao; Fang, Hui

    2011-07-01

    Inland lakes are major surface water resource in arid regions of Central Asia. The area changes in these lakes have been proved to be the results of regional climate changes and recent human activities. This study aimed at investigating the area variations of the nine major lakes in Central Asia over the last 30 years. Firstly, multi-temporal Landsat imagery in 1975, 1990, 1999, and 2007 were used to delineate lake extents automatically based on Normalized Difference Water Index (NDWI) threshold segmentation, then lake area variations were detailed in three decades and the mechanism of these changes was analyzed with meteorological data and hydrological data. The results indicated that the total surface areas of these nine lakes had decreased from 91,402.06 km(2) to 46,049.23 km(2) during 1975-2007, accounting for 49.62% of their original area of 1975. Tail-end lakes in flat areas had shrunk dramatically as they were induced by both climate changes and human impacts, while alpine lakes remained relatively stable due to the small precipitation variations. With different water usage of river outlets, the variations of open lakes were more flexible than those of other two types. According to comprehensive analyses, different types of inland lakes presented different trends of area changes under the background of global warming effects in Central Asia, which showed that the increased human activities had broken the balance of water cycles in this region.

  4. Differences in behavior and distribution of permafrost-related lakes in Central Yakutia and their response to climatic drivers

    NASA Astrophysics Data System (ADS)

    Ulrich, M.; Matthes, H.; Schirrmeister, L.; Schütze, J.; Park, H.; Iijima, Y.; Fedorov, A. N.

    2017-02-01

    The Central Yakutian permafrost landscape is rapidly being modified by land use and global warming, but small-scale thermokarst process variability and hydrological conditions are poorly understood. We analyze lake-area changes and thaw subsidence of young thermokarst lakes on ice-complex deposits (yedoma lakes) in comparison to residual lakes in alas basins during the last 70 years for a local study site and we record regional lake size and distribution on different ice-rich permafrost terraces using satellite and historical airborne imagery. Statistical analysis of climatic and ground-temperature data identified driving factors of yedoma- and alas-lake changes. Overall, lake area is larger today than in 1944 but alas-lake levels have oscillated greatly over 70 years, with a mean alas-lake-radius change rate of 1.6 ± 3.0 m/yr. Anthropogenic disturbance and forest degradation initiated, and climate forced rapid, continuous yedoma-lake growth. The mean yedoma lake-radius change rate equals 1.2 ± 1.0 m/yr over the whole observation period. Mean thaw subsidence below yedoma lakes is 6.2 ± 1.4 cm/yr. Multiple regression analysis suggests that winter precipitation, winter temperature, and active-layer properties are primary controllers of area changes in both lake types; summer weather and permafrost conditions additionally influence yedoma-lake growth rates. The main controlling factors of alas-lake changes are unclear due to larger catchment areas and subsurface hydrological conditions. Increasing thermokarst activity is currently linked to older terraces with higher ground-ice contents, but thermokarst activity will likely stay high and wet conditions will persist within the near future in Central Yakutian alas basins.

  5. Limnology of Big Lake, south-central Alaska, 1983-84

    USGS Publications Warehouse

    Woods, Paul F.

    1992-01-01

    The limnological characteristics and trophic state of Big Lake in south-central Alaska were determined from the results of an intensive study during 1983-84. The study was begun in response to concern over the potential for eutrophication of Big Lake, which has experienced substantial residential development and recreational use because of its proximity to Anchorage. The east and west basins of the 1,213 square-hectometer lake were each visited 36 times during the 2-year study to obtain a wide variety of physical, chemical, and biological data. During 1984, an estimate was made of the lake's annual primary production. Big Lake was classified as oligotrophic on the basis of its annual mean values for total phosphorus (9.5 micrograms per liter), total nitrogen (209 micrograms per liter), chlorophyll-a (2.5 micrograms per liter), secchi-disc transparency (6.3 meters), and its mean daily integral primary production of 81.1 milligrams of carbon fixed per square meter. The lake was, however, uncharacteristic of oligotrophic lakes in that a severe dissolved-oxygen deficit developed within the hypolimnion during summer stratification and under winter ice cover. The summer dissolved-oxygen deficit resulted from the combination of strong and persistent thermal stratification, which developed within 1 week of the melting of the lake's ice cover in May, and the failure of the spring circulation to fully reaerate the hypolimnion. The autumn circulation did reaerate the entire water column, but the ensuing 6 months of ice and snow cover prevented atmospheric reaeration of the water column and led to development of the winter dissolved-oxygen deficit. The anoxic conditions that eventually developed near the lake bottom allowed the release of nutrients from the bottom sediments and facilitated ammonification reactions. These processes yielded hypolimnetic concentrations of nitrogen and phosphorus compounds, which were much larger than the oligotrophic concentrations measured

  6. Challenges in understanding, modelling, and mitigating Lake Outburst Flood Hazard: experiences from Central Asia

    NASA Astrophysics Data System (ADS)

    Mergili, Martin; Schneider, Demian; Andres, Norina; Worni, Raphael; Gruber, Fabian; Schneider, Jean F.

    2010-05-01

    Lake Outburst Floods can evolve from complex process chains like avalanches of rock or ice that produce flood waves in a lake which may overtop and eventually breach glacial, morainic, landslide, or artificial dams. Rising lake levels can lead to progressive incision and destabilization of a dam, to enhanced ground water flow (piping), or even to hydrostatic failure of ice dams which can cause sudden outflow of accumulated water. These events often have a highly destructive potential because a large amount of water is released in a short time, with a high capacity to erode loose debris, leading to a powerful debris flow with a long travel distance. The best-known example of a lake outburst flood is the Vajont event (Northern Italy, 1963), where a landslide rushed into an artificial lake which spilled over and caused a flood leading to almost 2000 fatalities. Hazards from the failure of landslide dams are often (not always) fairly manageable: most breaches occur in the first few days or weeks after the landslide event and the rapid construction of a spillway - though problematic - has solved some hazardous situations (e.g. in the case of Hattian landslide in 2005 in Pakistan). Older dams, like Usoi dam (Lake Sarez) in Tajikistan, are usually fairly stable, though landsildes into the lakes may create floodwaves overtopping and eventually weakening the dams. The analysis and the mitigation of glacial lake outburst flood (GLOF) hazard remains a challenge. A number of GLOFs resulting in fatalities and severe damage have occurred during the previous decades, particularly in the Himalayas and in the mountains of Central Asia (Pamir, Tien Shan). The source area is usually far away from the area of impact and events occur at very long intervals or as singularities, so that the population at risk is usually not prepared. Even though potentially hazardous lakes can be identified relatively easily with remote sensing and field work, modeling and predicting of GLOFs (and also

  7. Legacies of Glacio-fluvial Interactions in the Finger Lakes, Central New York

    NASA Astrophysics Data System (ADS)

    Safran, E. B.; Fountain, A. G.

    2011-12-01

    The Finger Lakes region of central New York exhibits spectacular examples of the interplay between glacial and fluvial processes. The Finger Lakes themselves were carved by ice sheets and related subglacial hydrologic processes that enlarged, over-deepened, and reversed the drainage direction of pre-existing fluvial valleys. The region's famous gorges flank the glacial troughs and reflect ongoing fluvial adjustment to glacially driven base level variations. Modern tools of topographic analysis permit quantification of the imprint that glacial processes leave on fluvial form and process. Regionally, ice sheet erosion is maximized along the north end of the Seneca/Cayuga trough. Local relief ranges from ~100 m at the north end of Seneca and Cayuga lakes to 250-400 m on the southern ends of these lakes and on the smaller, flanking lakes (Keuka, Canandaigua, Skaneateles, Owasco). Concavity indices for lake-tributary stream profiles are predominantly in the range of -7 to 0, reflecting a convex initial form imposed by glacial processes, while normalized channel steepness (ksn) indices are generally under 40 (reference concavity of 0.45), reflecting the gentle gradients of the glacial uplands. Concavity index and ksn values are maximized (>0, and >75, respectively) along short segments at the downstream ends of the so-called interglacial or post-glacial gorge reaches, again maximized at the southern and peripheral parts of the Seneca/Cayuga trough. Finally, streams that cross former channel courses buried by subglacial debris typically have more numerous and/or more pronounced knickpoints and more concave long profile segments than streams that do not. In short, the legacy of glaciations from the regional to the reach scale appears to be driving patterns of fluvial response in the Finger Lakes.

  8. Coastal lake sediments reveal 5500 years of tsunami history in south central Chile

    NASA Astrophysics Data System (ADS)

    Kempf, Philipp; Moernaut, Jasper; Van Daele, Maarten; Vandoorne, Willem; Pino, Mario; Urrutia, Roberto; De Batist, Marc

    2017-04-01

    We present an exceptionally long and continuous coastal lacustrine record of ∼5500 years from Lake Huelde on the west coast of Chiloé Island in south central Chile. The study area is located within the rupture zone of the giant 1960 CE Great Chilean Earthquake (MW 9.5). The subsequent earthquake-induced tsunami inundated Lake Huelde and deposited mud rip-up clasts, massive sand and a mud cap in the lake. Long sediment cores from 8 core sites within Lake Huelde reveal 16 additional sandy layers in the 5500 year long record. The sandy layers share sedimentological similarities with the deposit of the 1960 CE tsunami and other coastal lake tsunami deposits elsewhere. On the basis of general and site-specific criteria we interpret the sandy layers as tsunami deposits. Age-control is provided by four different methods, 1) 210Pb-dating, 2) the identification of the 137Cs-peak, 3) an infrared stimulated luminescence (IRSL) date and 4) 22 radiocarbon dates. The ages of each tsunami deposit are modelled using the Bayesian statistic tools of OxCal and Bacon. The record from Lake Huelde matches the 8 regionally known tsunami deposits from documented history and geological evidence from the last ∼2000 years without over- or underrepresentation. We extend the existing tsunami history by 9 tsunami deposits. We discuss the advantages and disadvantages of various sedimentary environments for tsunami deposition and preservation, e.g. we find that Lake Huelde is 2-3 times less sensitive to relative sea-level change in comparison to coastal marshes in the same region.

  9. Hydrologic influence on methane and carbon dioxide dynamics at two north-central Minnesota lakes

    USGS Publications Warehouse

    Striegl, R.G.; Michmerhuizen, C.M.

    1998-01-01

    Annual emissions of (CH4 + CO2) to the atmosphere were proportional to net hydrologic inputs of C, mostly by groundwater, at two lakes in the Shingobee River watershed in north-central Minnesota. Williams Lake (WL), a closed basin lake near the top of the watershed, had a hydraulic residence time of 2-4 yr and groundwater exchange of about +2 mol dissolved inorganic carbon (DIC) and -0.1 mol dissolved organic carbon (DOC) m-2 lake area yr-1. The Shingobee River flows through Shingobee Lake (SL) that had a hydraulic residence of 0.3-0.4 yr and received net groundwater plus surface-water inputs of +5.3 to +7.3 mol DIC and fewer than +1.3 mol (DOC + particulate organic carbon) m-2 yr-1. Approximately 60-80% of net annual C input to SL was from groundwater. Lake storage of CH4 and CO2 was greatest in late winter, with maximum emissions to the atmosphere immediately following ice melt. The lakes emitted CH4 continuously during open water, having annual losses of -1.6 mol CH4 m-2 yr-1 at WL and -1.9 mol CH4 m-2 yr-1 at SL. Although the WL epilimnion was CO2 depleted throughout summer, net annual CO2 exchange with the atmosphere was near zero because springtime emission offset summertime uptake. CO2 supersaturation resulted in emission of -8.0 mol CO2 m-2 yr-1 at SL.

  10. Spatio-temporal development of high-mountain lakes in the headwaters of the Amu Darya River (Central Asia)

    NASA Astrophysics Data System (ADS)

    Mergili, Martin; Müller, Johannes P.; Schneider, Jean F.

    2013-08-01

    The sources of the Amu Darya, one of the major Central Asian rivers draining to the Aral Sea, are located in the glacierized high-mountain areas of Tajikistan, Kyrgyzstan and Afghanistan. There, climate change and the resulting retreat of glaciers have led to the formation of numerous new glacial lakes. Other lakes in the area are embedded in older glacial landscapes (erosion lakes) or retained by block or debris dams (e.g., Lake Sarez). A multi-temporal lake inventory is prepared and analysed, based on remotely sensed data. Corona images from 1968 are used as well as more up-to-date ASTER and Landsat 7 scenes. 1642 lakes are mapped in total, 652 out of them are glacial lakes. 73% of all lakes are located above 4000 m a.s.l. Glacial lakes, abundant in those areas where glacier tongues retreat over flat or moderately steep terrain, have experienced a significant growth, even though changes are often superimposed by short-term fluctuations. The analysis results also indicate a shifting of the growth of glacial lakes from the south western Pamir to the central and northern Pamir during the observation period. This trend is most likely associated with more elevated contribution areas in the central and northern Pamir. The lakes of the other types have remained constant in size in general. The lake development reflects changes in the state of the water resources in the study area on the one hand and determines the level of lake outburst hazards on the other hand.

  11. Diatom assemblage responses to changing environment in the conspicuously eutrophic Kiuruvesi lake route, central-eastern Finland

    NASA Astrophysics Data System (ADS)

    Tammelin, Mira; Kauppila, Tommi

    2016-04-01

    Lakes and their water quality have been affected by anthropogenic actions for centuries. The most intensive changes have often occurred since the mid-19th century. Industrialization, modern agriculture, forest ditching and artificial lowering of water level are examples of these changes that have usually resulted in the deterioration of lake water quality. Many organisms, such as diatoms, are sensitive to these changes in their environmental conditions. Therefore, a marked species turnover is often seen between the pre and post human impact diatom assemblages. This turnover can be rapidly assessed simultaneously from many lakes by using multivariate methods and top-bottom sampling. Our study area consists of three adjacent lake routes in the grass cultivation and dairy production area of central-eastern Finland, where slash-and-burn cultivation and artificial water level lowering were common practice during the past centuries. The centermost Iisalmi lake route is particularly interesting because of the conspicuously eutrophic lakes in its Kiuruvesi subroute. We used the top-bottom approach to sample pre and post human impact samples from 47 lakes (50 sampling sites) located in the three lake routes. In addition, stratigraphic samples from the long cores of three lakes (one larger central basin and two small upstream lakes) in the Kiuruvesi subroute were studied in more detail. Multivariate methods were used to assess diatom assemblage change within the long cores and between the pre-disturbance and modern samples. The results indicate that most study lakes have undergone a marked shift in their diatom assemblages since the onset of human impact in the area. The lake routes are characterized by differing pre-impact diatom assemblages. However, human influence has reduced their natural variation. Similar diatom species are common in the modern samples of the heavily impacted lakes in all three lake routes. The detailed examination of the diatom assemblage turnover in

  12. Chemical evidences of the effects of global change in high elevation lakes in Central Himalaya, Nepal

    NASA Astrophysics Data System (ADS)

    Tartari, Gianni; Lami, Andrea; Rogora, Michela; Salerno, Franco

    2016-04-01

    It is well known that the lakes integrate the pressure of their surrounding terrestrial environment and the climatic variability. Both the water column and sediments are capable to accumulate signals of global change, such as warming of the deep layers or mutation of diverse biological records (e.g., fossil diatoms) and the nutrient loads variability affecting the trophic state. Typically, the biological responses to climate change have been studied in several types of lakes, while documented changes in water chemistry are much rare. A long term study of 20 high altitude lakes located in central southern Himalaya (Mt Everest) conducted since the 90s has highlighted a general change in the chemical composition of the lake water: a substantial rise in the ionic content was observed, particularly pronounced in the case of sulphate. In a couple of these lakes, monitored on an annual basis, the sulphate concentrations increased over 4-fold. A change in the composition of atmospheric wet deposition, as well as a possible influence of decrease in seasonal snow cover duration, which could have exposed larger basin surfaces to alteration processes, were excluded. The chemical changes proved to be mainly related to the sulphide oxidation processes occurring in the bedrocks or the hydrographic basins. In particular, the oxidation processes, considered as the main factor causing the sulphate increase, occurred in subglacial environments characterized by higher glacier velocities causing higher glacier shrinkage. Associated to this mechanism, the exposure of fresh mineral surfaces to the atmosphere may have contributed also to increases in the alkalinity of lakes. Weakened monsoon of the past two decades may have partially contributed to the solute enrichment of the lakes through runoff waters. The almost synchronous response of the lakes studied, which differs in terms of the presence of glaciers in their basins, highlights the fact that the increasing ionic content of lake

  13. New insights on Illinoian deglaciation from deposits of Glacial Lake Quincy, central Indiana

    NASA Astrophysics Data System (ADS)

    Wood, J. R.; Forman, S. L.; Pierson, J.; Gomez, J.

    2010-03-01

    The deposits of Glacial Lake Quincy overlie a diamicton associated with the classically defined Illinoian limit in central Indiana. This lake covered at least 180 km 2 with a depth of > 20 m and developed when the Illinoian ice sheet retreated 15 km from the maximum limit, causing lake impoundment against Devore Ridge. Overflow from Glacial Lake Quincy eroded across the ridge forming a number of steeped-walled outlets. A section along Mill Creek exposes a sedimentologic sequence associated with Glacial Lake Quincy from a subglacial diamicton to ice-proximal to ice-distal glacial lacustrine sediments. We report new optical ages by multiple aliquot regenerative dose procedure for the fine-grained rhythmically bedded sediments presumed to represent the lowest energy depositional facies, dominated by suspension settling, which maximized sunlight exposure. In turn, optical ages were determined on the fine-grained (4-11 μm) polymineral and quartz fractions under infrared and blue excitation, which yielded statistically similar ages. Optical ages span from ca. 170 to 108 ka, with the average of 16 optical ages indicating deglaciation at ca. 135 ka, generally coincident with Marine Oxygen Isotope Stage 6-to-5 transition and rise in global sea level.

  14. Sediment evidence of early eutrophication and heavy metal pollution of Lake Mälaren, central Sweden.

    PubMed

    Renberg, I; Bindler, R; Bradshaw, E; Emteryd, O; McGowan, S

    2001-12-01

    Lake Mälaren is the water supply and recreation area for more than 1 million people in central Sweden and subject to considerable environmental concern. To establish background data for assessments of contemporary levels of trophy and heavy metal pollution, sediment cores from the lake were analyzed. Diatom-inferred lake-water phosphorus concentrations suggest that pre-20th century nutrient levels in Södra Björkfjärden, a basin in the eastern part of Mälaren, were higher (c. 10-20 micrograms TP L-1) than previously assumed (c. 6 micrograms TP L-1). Stable lead isotope and lead concentration analyses from 3 basins (S. Björkfjärden, Gisselfjärden and Asköfjärden) show that the lake was polluted in the 19th century and earlier from extensive metal production and processing in the catchment, particularly in the Bergslagen region. The lake has experienced a substantial improvement of the lead pollution situation in the 20th century following closure of the mining and metal industry. The lead pollution from the old mining industry was large compared to late-20th century pollution from car emissions, burning of fossil fuels and modern industries.

  15. The record of historic earthquakes in lake sediments of Central Switzerland

    NASA Astrophysics Data System (ADS)

    Monecke, Katrin; Anselmetti, Flavio S.; Becker, Arnfried; Sturm, Michael; Giardini, Domenico

    2004-12-01

    Deformation structures in lake sediments in Central Switzerland can be attributed to strong historic earthquakes. The type and spatial distribution of the deformation structures reflect the historically documented macroseismic intensities thus providing a useful calibration tool for paleoseismic investigations in prehistoric lake sediments. The Swiss historical earthquake catalogue shows four moderate to strong earthquakes with moment magnitudes of Mw=5.7 to Mw=6.9 and epicentral intensities of I0=VII to I0=IX that affected the area of Central Switzerland during the last 1000 years. These are the 1964 Alpnach, 1774 Altdorf, 1601 Unterwalden, and 1356 Basel earthquakes. In order to understand the effect of these earthquakes on lacustrine sediments, four lakes in Central Switzerland (Sarner See, Lungerer See, Baldegger See, and Seelisberg Seeli) were investigated using high-resolution seismic data and sediment cores. The sediments consist of organic- and carbonate-rich clayey to sandy silts that display fine bedding on the centimeter to millimeter scale. The sediments are dated by historic climate and environmental records, 137Cs activity, and radiocarbon ages. Deformation structures occur within distinct zones and include large-scale slumps and rockfalls, as well as small-scale features like disturbed and contorted lamination and liquefaction structures. These deformations are attributed to three of the abovementioned earthquakes. The spatial distribution of deformation structures in the different lakes clearly reflects the historical macroseismic dataset: Lake sediments are only affected if they are situated within an area that underwent groundshaking not smaller than intensity VI to VII. We estimate earthquake size by relating the epicentral distance of the farthest liquefaction structure to earthquake magnitude. This relationship is in agreement with earthquake size estimations based on the historical dataset.

  16. Stable carbon and oxygen isotope record of central Lake Erie sediments

    USGS Publications Warehouse

    Tevesz, M.J.S.; Spongberg, A.L.; Fuller, J.A.

    1998-01-01

    Stable carbon and oxygen isotope data from mollusc aragonite extracted from sediment cores provide new information on the origin and history of sedimentation in the southwestern area of the central basin of Lake Erie. Sediments infilling the Sandusky subbasin consist of three lithologic units overlying glacial deposits. The lowest of these is a soft gray mud overlain by a shell hash layer containing Sphaerium striatinum fragments. A fluid mud unit caps the shell hash layer and extends upwards to the sediment-water interface. New stable isotope data suggest that the soft gray mud unit is of postglacial, rather than proglacial, origin. These data also suggest that the shell hash layer was derived from erosional winnowing of the underlying soft gray mud layer. This winnowing event may have occurred as a result of the Nipissing flood. The Pelee-Lorain moraine, which forms the eastern boundary of the Sandusky subbasin, is an elevated area of till capped by a sand deposit that originated as a beach. The presence of both the shell hash layer and relict beach deposit strengthens the interpretation that the Nipissing flood was a critical event in the development of the southwestern area of the central basin of Lake Erie. This event, which returned drainage from the upper lakes to the Lake Erie basin, was a dominant influence on regional stratigraphy, bathymetry, and depositional setting.

  17. Assessing and addressing the re-eutrophication of Lake Erie: central basin hypoxia

    USGS Publications Warehouse

    Scavia, Donald; Allan, J. David; Arend, Kristin K.; Bartell, Steven; Beletsky, Dmitry; Bosch, Nate S.; Brandt, Stephen B.; Briland, Ruth D.; Daloğlu, Irem; DePinto, Joseph V.; Dolan, David M.; Evans, Mary Anne; Farmer, Troy M.; Goto, Daisuke; Han, Haejin; Höök, Tomas O.; Knight, Roger; Ludsin, Stuart A.; Mason, Doran; Michalak, Anna M.; Richards, R. Peter; Roberts, James J.; Rucinski, Daniel K.; Rutherford, Edward; Schwab, David J.; Sesterhenn, Timothy M.; Zhang, Hongyan; Zhou, Yuntao

    2014-01-01

    Relieving phosphorus loading is a key management tool for controlling Lake Erie eutrophication. During the 1960s and 1970s, increased phosphorus inputs degraded water quality and reduced central basin hypolimnetic oxygen levels which, in turn, eliminated thermal habitat vital to cold-water organisms and contributed to the extirpation of important benthic macroinvertebrate prey species for fishes. In response to load reductions initiated in 1972, Lake Erie responded quickly with reduced water-column phosphorus concentrations, phytoplankton biomass, and bottom-water hypoxia (dissolved oxygen 2) requires cutting total phosphorus loads by 46% from the 2003–2011 average or reducing dissolved reactive phosphorus loads by 78% from the 2005–2011 average. Reductions to these levels are also protective of fish habitat. We provide potential approaches for achieving those new loading targets, and suggest that recent load reduction recommendations focused on western basin cyanobacteria blooms may not be sufficient to reduce central basin hypoxia to 2000 km2.

  18. Crustal structure of central Lake Baikal: Insights into intracontinental rifting

    USGS Publications Warehouse

    ten Brink, U.S.; Taylor, M.H.

    2002-01-01

    The Cenozoic rift system of Baikal, located in the interior of the largest continental mass on Earth, is thought to represent a potential analog of the early stage of breakup of supercontinents. We present a detailed P wave velocity structure of the crust and sediments beneath the Central Basin, the deepest basin in the Baikal rift system. The structure is characterized by a Moho depth of 39-42.5 km; an 8-km-thick, laterally continuous high-velocity (7.05-7.4 km/s) lower crust, normal upper mantle velocity (8 km/s), a sedimentary section reaching maximum depths of 9 km, and a gradual increase of sediment velocity with depth. We interpret the high-velocity lower crust to be part of the Siberian Platform that was not thinned or altered significantly during rifting. In comparison to published results from the Siberian Platform, Moho under the basin is elevated by <3 km. On the basis of these results we propose that the basin was formed by upper crustal extension, possibly reactivating structures in an ancient fold-and-thrust belt. The extent and location of upper mantle extension are not revealed by our data, and it may be offset from the rift. We believe that the Baikal rift structure is similar in many respects to the Mesozoic Atlantic rift system, the precursor to the formation of the North Atlantic Ocean. We also propose that the Central Baikal rift evolved by episodic fault propagation and basin enlargement, rather than by two-stage rift evolution as is commonly assumed.

  19. Spatial and Temporal Trends of Snowfall in Central New York - A Lake Effect Dominated Region

    NASA Astrophysics Data System (ADS)

    Hartnett, Justin Joseph

    Central New York is located in one of the snowiest regions in the United States, with the city of Syracuse, New York the snowiest metropolis in the nation. Snowfall in the region generally begins in mid-November and lasts until late-March. Snow accumulation occurs from a multitude of conditions: frontal systems, mid-latitude cyclones, Nor'easters, and most notably lake-effect storms. Lake effect snowfall (LES) is a difficult parameter to forecast due to the isolated and highly variable nature of the storm. Consequently, studies have attempted to determine changes in snowfall for lake-effect dominated regions. Annual snowfall patterns are of particular concern as seasonal snowfall totals are vital for water resources, winter businesses, agriculture, government and state agencies, and much more. Through the use of snowfall, temperature, precipitation, and location data from the National Weather Service's Cooperative Observer Program (COOP), spatial and temporal changes in snowfall for Central New York were determined. In order to determine climatic changes in snowfall, statistical analyses were performed (i.e. least squares estimation, correlations, principal component analyses, etc.) and spatial maps analyzed. Once snowfall trends were determined, factors influencing the trends were examined. Long-term snowfall trends for CNY were positive for original stations (˜0.46 +/- 0.20 in. yr -1) and homogenously filtered stations (0.23 +/- 0.20 in. yr -1). However, snowfall trends for shorter time-increments within the long-term period were not consistent, as positive, negative, and neutral trends were calculated. Regional differences in snowfall trends were observed for CNY as typical lake-effect areas (northern counties, the Tug Hill Plateau and the Southern Hills) experienced larger snowfall trends than areas less dominated by LES. Typical lake-effect months (December - February) experienced the greatest snowfall trend in CNY compared to other winter months. The

  20. Early Pleistocene Glacial Lake Lesley, West Branch Susquehanna River valley, central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Ramage, Joan M.; Gardner, Thomas W.; Sasowsky, Ira D.

    1998-02-01

    Laurentide glaciers extended into north central Pennsylvania repeatedly during at least the last 2 million years. Early Pleistocene glaciation extended farther south into central Pennsylvania than any subsequent glaciation, reaching the West Branch Susquehanna River (WBSR) valley. Early Pleistocene ice dammed the northeast-flowing West Branch Susquehanna River at Williamsport, forming Glacial Lake Lesley, a 100-km-long proglacial lake. In this paper, we present compelling evidence for the lake and its age. Maximum lake volume (˜ 100 km 3) was controlled by the elevation of the lowest drainage divide, ˜ 340 m above sea level at Dix, Pennsylvania. Stratified deposits at McElhattan and Linden are used to reconstruct depositional environments in Glacial Lake Lesley. A sedimentary section 40 m thick at McElhattan fines upward from crossbedded sand to fine, wavy to horizontally laminated clay, consistent with lake deepening and increasing distance from the sediment source with time. At Linden, isolated cobbles, interpreted as dropstones, locally deform glacio-lacustrine sediment. We use paleomagnetism as an age correlation tool in the WBSR valley to correlate contemporaneous glaciofluvial and proglacial lacustrine sediments. Reversed remanent polarity in finely-laminated lacustrine clay and silt at McElhattan ( I = 20.4°, D = 146.7°, α95 = 17.7°) and in interbedded silt and sand at Linden ( I = 55.3°, D = 175.2°, α95 = 74.6°) probably corresponds to the latter part of the Matuyama Reversed Polarity Chron, indicating an age between ˜ 770 and ˜ 970 ka. At McElhattan, a diamicton deformed the finely laminated silt and clay by loading and partial fluidization during or soon after lake drainage. As a result, the deformed clay at McElhattan lacks discrete bedding and records a different characteristic remanent magnetism from underlying, undeformed beds. This difference indicates that the characteristic remanent magnetism is detrital. An electrical resistivity

  1. Geomorphology of the Chippewa River delta of Glacial Lake Saginaw, central Lower Michigan, USA

    NASA Astrophysics Data System (ADS)

    Connallon, Christopher B.; Schaetzl, Randall J.

    2017-08-01

    We introduce, characterize, and interpret the geomorphic history of a relict, Pleistocene-aged delta of the Chippewa River in central Lower Michigan. The broad, sandy Chippewa delta developed into various stages of Glacial Lake Saginaw, between ca. ≈ 17 and 15 ka·BP (calibrated ages). Although the delta was first identified in 1955 on a statewide glacial geology map, neither its extent nor its Pleistocene history had been previously determined. The delta is typically forested, owing to its wet, sandy soils, which stand out against the agricultural fields of the surrounding, loamy lake plain sediments. The delta heads near the city of Mt Pleasant and extends eastward onto the Saginaw Lowlands, i.e., the plain of Glacial Lake Saginaw. Data from 3285 water well logs, 180 hand augered sites, and 185 points randomly located in a GIS on two-storied (sand over loam) soils were used to determine the extent, textural properties, and thickness of the delta. The delta is ≈ 18 km wide and ≈ 38 km long and is sandy throughout. Deltaic sediments from neighboring rivers that also drained into Glacial Lake Saginaw merge with the lower Chippewa delta, obscuring its boundary there. The delta is thickest near the delta's head and in the center, but thins to 1-2 m or less on its eastern margins. Mean thicknesses are 2.3-2.9 m, suggestive of a thin sediment body, frequently impacted by the waves and fluctuating waters of the lakes. Although beach ridges are only weakly expressed across the delta because of the sandy sediment, the coarsest parts of the delta are generally coincident with some of these inferred former shorezones and have a broad, incised channel that formed while lake levels were low. The thick upper delta generally lies above the relict shorelines of Glacial Lakes Saginaw and Arkona (≈ 17.1 to ≈ 16 ka·BP), whereas most of the thin, distal delta is associated with Glacial Lake Warren (≈ 15 ka·BP). Together, these data suggest that the Chippewa delta formed

  2. Effects of recharge, Upper Floridan aquifer heads, and time scale on simulated ground-water exchange with Lake Starr, a seepage lake in central Florida

    USGS Publications Warehouse

    Swancar, Amy; Lee, Terrie Mackin

    2003-01-01

    Lake Starr and other lakes in the mantled karst terrain of Florida's Central Lake District are surrounded by a conductive surficial aquifer system that receives highly variable recharge from rainfall. In addition, downward leakage from these lakes varies as heads in the underlying Upper Floridan aquifer change seasonally and with pumpage. A saturated three-dimensional finite-difference ground-water flow model was used to simulate the effects of recharge, Upper Floridan aquifer heads, and model time scale on ground-water exchange with Lake Starr. The lake was simulated as an active part of the model using high hydraulic conductivity cells. Simulated ground-water flow was compared to net ground-water flow estimated from a rigorously derived water budget for the 2-year period August 1996-July 1998. Calibrating saturated ground-water flow models with monthly stress periods to a monthly lake water budget will result in underpredicting gross inflow to, and leakage from, ridge lakes in Florida. Underprediction of ground-water inflow occurs because recharge stresses and ground-water flow responses during rainy periods are averaged over too long a time period using monthly stress periods. When inflow is underestimated during calibration, leakage also is underestimated because inflow and leakage are correlated if lake stage is maintained over the long term. Underpredicted leakage reduces the implied effect of ground-water withdrawals from the Upper Floridan aquifer on the lake. Calibrating the weekly simulation required accounting for transient responses in the water table near the lake that generated the greater range of net ground-water flow values seen in the weekly water budget. Calibrating to the weekly lake water budget also required increasing the value of annual recharge in the nearshore region well above the initial estimate of 35 percent of the rainfall, and increasing the hydraulic conductivity of the deposits around and beneath the lake. To simulate the total

  3. Nitrate attenuation potential of hypersaline lake sediments in central Spain: flow-through and batch experiments.

    PubMed

    Carrey, R; Rodríguez-Escales, P; Otero, N; Ayora, C; Soler, A; Gómez-Alday, J J

    2014-08-01

    Complex lacustrine systems, such as hypersaline lakes located in endorheic basins, are exposed to nitrate (NO3(-)) pollution. An excellent example of these lakes is the hypersaline lake located in the Pétrola basin (central Spain), where the lake acts as a sink for NO3(-) from agricultural activities and from sewage from the surrounding area. To better understand the role of the organic carbon (Corg) deposited in the bottom sediment in promoting denitrification, a four-stage flow-through experiment (FTR) and batch experiments using lake bottom sediment were performed. The chemical, multi-isotopic and kinetic characterization of the outflow showed that the intrinsic NO3(-) attenuation potential of the lake bottom sediment was able to remove 95% of the NO3(-) input over 296days under different flow conditions. The NO3(-) attenuation was mainly linked with denitrification but some dissimilatory nitrate reduction to ammonium was observed at early days favored by the high C/N ratio and salinity. Sulfate reduction could be neither confirmed nor discarded during the experiments because the sediment leaching masked the chemical and isotopic signatures of this reaction. The average nitrogen reduction rate (NRR) obtained was 1.25mmold(-1)kg(-1) and was independent of the flow rate employed. The amount of reactive Corg from the bottom sediment consumed during denitrification was 28.8mmol, representing approximately 10% of the total Corg of the sediment (1.2%). Denitrification was produced coupled with an increase in the isotopic composition of both δ(15)N and δ(18)O. The isotopic fractionations (ε of (15)N-NO3(-) and (18)O-NO3(-)) produced during denitrification were calculated using batch and vertical profile samples. The results were -14.7‰ for εN and -14.5‰ for εO. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Dust transport and palaeoclimate during the Oldest Dryas in Central Europe - implications from varves (Lake Constance)

    SciTech Connect

    Niessen, F.; Lister, G.; Giovanoli, F.

    1992-10-01

    This paper evaluates evidence for seasonal loess deposits in peri-Alpine Lake Constance at the end of the last Glacial (Oldest Dryas chronozone). The sedimentology of laminated couplets comprising yellow and grey silts evaluates the couplets as varves comprising alternations of loess and glacial silt and clay. The laminae, less than 1 mm thick, include from bottom to top: (1) a matrix of well-sorted, non-graded fine yellow silt with sand-size intraclasts, (2) coarsening-upward grey silt with a cap of fining-upward silt to clay. This is typical and reflects summer and winter deposits (silt and clay, respectively). The authors propose that the lack of grading and the matrix supported fabric is indicative of aeolian transport and interpret the yellow laminae as loess deposits. Volcanic glass intraclasts in the loess layers are probably derived from volcanic terrain to the west of the lake, indicating an easterly palaeowind direction. Deposition of loess in the lake occurred regularly at the beginning of each annual cycle, suggesting the palaeowinds were associated with winter and/or spring conditions. Two transport scenarios are suggested to explain the sand grains scattered in this deep-water lacustrine record. 1. The grains may have been transported as bedload over the annual winter ice-cover of the lake under moderate wind strengths, frozen into the ice, and released for deposition during spring melt. 2. The sand grains were blown directly out onto the lake water by very strong winds during spring. The first scenario is contrary to the general view that loess was transported during summer, and that loess deposits thus reflect summer conditions only. Loess input to the lake shows a transitional decrease after ca. 14.3 kyr BP and cessation at ca. 14 kyr BP, probably as a result of a change of wind behaviour, increased humidity and/or vegetational changes during the Oldest Dryas in central Europe. 62 refs., 8 figs.

  5. A CHRONOLOGICAL FRAMEWORK FOR THE HOLOCENE VEGETATIONAL HISTORY OF CENTRAL MINNESOTA: THE STEEL LAKE POLLEN RECORD

    SciTech Connect

    Wright, H E; Stefanova, I; Tian, J; Brown, T A; Hu, F S

    2003-11-10

    Paleorecords from Minnesota and adjacent areas have often been used to evaluate large-scale climatic processes in the mid-continent of North America. However, most of these records are compromised by chronological flaws, making problematic any comparisons with climatic interpretations based on other records (e.g., GISP2 in Greenland). We report here a high-resolution pollen record with a secure chronology constrained by 26 {sup 14}C dates on terrestrial macrofossils from Steel Lake, central Minnesota. About 11,200 years ago (calibrated yr BP) the late-glacial Picea forest near Steel Lake was succeeded abruptly by Pinus banksiana and/or resinosa. The Pinus forest began to open 9.4 ka cal BP with the expansion of prairie taxa, and a pine parkland or savanna prevailed until about 8 ka cal BP, when Quercus replaced Pinus to become the dominant tree in the prairie areas for 4500 years. The close chronological control permits the correlation of key vegetational changes with those at other reliably dated sites in the eastern Dakotas and in Minnesota, suggesting that the abrupt decline of the spruce forest was time-transgressive from southwest to northeast during 2000 years, and that the development of prairie was time-transgressive in the same direction over 2600 years. Correlation of key pollen horizons at Steel Lake with those in the high-resolution pollen profiles of Elk Lake, ca. 50 km northwest of Steel Lake, suggests that the well-known Elk Lake varve chronology for the early Holocene is about 1000 years too young.

  6. Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

    NASA Astrophysics Data System (ADS)

    Sobrinho, R. L.; Bernardes, M. C.; Abril, G.; Kim, J.-H.; Zell, C. I.; Mortillaro, J.-M.; Meziane, T.; Moreira-Turcq, P.; Sinninghe Damsté, J. S.

    2016-01-01

    In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Mirituba and Curuai) which have different morphologies, hydrodynamics and vegetation coverages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ13Corg). These results were compared with lignin phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the crenarchaeol as an indicator of aquatic (rivers and lakes) OM. Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C3 plant-derived OM. However, a downstream increase in C4 macrophyte-derived OM contribution was observed along the gradient of increasing open waters - i.e., from upstream to downstream. Accordingly, we attribute the temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.

  7. The enigmatic Zerelia twin-lakes (Thessaly, Central Greece): two potential meteorite impact Craters

    NASA Astrophysics Data System (ADS)

    Dietrich, V. J.; Lagios, E.; Reusser, E.; Sakkas, V.; Gartzos, E.; Kyriakopoulos, K.

    2013-09-01

    Two circular permanent lakes of 150 and 250 m diameter and 6-8 m depth to an unconsolidated muddy bottom occur 250 m apart from each other in the agricultural fields SW of the town of Almiros (Thessaly, central Greece). The age of the lakes is assumed to be Late Pliocene to Early Holocene with a minimum age of approx. 7000 yr BP. The abundant polymict, quartz-rich carbonate breccia and clasts with a clay rich matrix in the shallow embankments of the lakes show weak stratification but no volcanic structures. The carbonate clasts and particles often display spheroidal shapes and consist of calcite aggregates with feathery, arborescent, variolitic to micro-sparitic textures and spheroidal fabrics, recrystallized and deformed glass-shaped fragments, calcite globules in quartz; thus indications of possible carbonate melting, quenching and devitrification. The carbonatic matrix includes small xenomorphic phases, such as chromspinel, zircon with blurred granular and skeletal textures, skeletal rutile and ilmenite, which are interpreted as relicts of partial melting and quenching under high temperatures of 1240-1800 °C. Only a few quartz fragments exhibit indistinct planar fractures. In several cases they include exotic Al-Si- and sulfur bearing Fe-phases, < 1-10 μm as globules. The modeled "Residual Gravity" profiles through the lakes indicate negative gravity anomalies of bowl-type structures down to 150 m for the eastern lake and down to 250 m for the larger western lake. Several hypotheses can be drawn upon to explain the origin of these enigmatic twin-lakes: (a) Maar-type volcanic craters; (b) hydrothermal or CO2/hydrocarbon gas explosion craters; (c) and (d) doline holes due to karstification; or (e) small meteorite impact craters, the latter being a plausible explanation due to geologic, petrologic, and geophysical evidence. The morphology and dimensions of the lakes as well as the density contrast tomography of the bedrock favor a meteorite impact hypothesis of a

  8. Pb isotopes in sediments of Lake Constance, Central Europe constrain the heavy metal pathways and the pollution history of the catchment, the lake and the regional atmosphere

    SciTech Connect

    Kober, B.; Wessels, M.; Bollhoefer, A.; Mangini

    1999-05-01

    Pb isotope ratios and Pb concentrations of well-dated sediments of Lake Constance, Central Europe have been analyzed using thermal ion mass spectrometry. Sequential extraction studies indicated isotope homogeneity of the leachable Pb components within the investigated layers. Since the middle of the 19th century a significant anthropogenic Pb component appeared in the lake sediments, and rapidly approaches concentration levels similar to that of the geogenic Pb background (20 ppm) at the beginning of the 20th century. Anthropogenic Pb was predominantly transferred to the lake sediments via the atmosphere. Pb sources were coal combustion, industrial ore processing and leaded gasoline. The flux of a fluvial Pb component to the lake sediments, additive to atmospheric Pb deposition, peaked in about 1960. This flux is attributed to (re)mobilization of Pb from polluted parts of the lake catchment, and indicates the change of catchment soils from a pollution sink to a heavy metal source. The strong reduction of anthropogenic Pb in the uppermost lake sediments since the 1960s has been caused by advances of environmental protection. The lake sediments record the changing fluxes and the isotope composition of the deposited aeolian Pb pollution. During the 20th century aeolian Pb fluxes to the lake sediments were in the range of 1--4 {micro}g/cm{sup 2}/a. During peak emission periods of gasoline Pb to the atmosphere (1960--1990) the aerosol Pb isotope composition was rather constant ({sup 206}Pb/{sup 207}Pb: 1.12--1.13) and probably a mixture of Canadian and Australian with Russian and Central European Pb types. Aeolian Pb isotope and Pb flux trends in the lake sediments as a whole agree well with the trends found in Alpine glaciers (Doering et al., 1997a,b) and in ombrotrophic peat bogs of Switzerland (Shotyk et al., 1996). However, different industrial Pb components were deposited in the archives of aeolian pollution during the early 20th century.

  9. Impacts of urban sprawl on the area of downtown lakes in a highly developing city on central China

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Zhang, Y.

    2016-12-01

    Wuhan city in central China is full of water resources and numerous lakes are located. Downtown lakes have significant ecological value and ornamental value for urban inhabitants in Wuhan. Under the rapid process of urban sprawl, downtown lakes are occupied by impervious areas. This research uses Landsat images to extract land uses from 1991 to 2013 in Wuhan city , and attempts to find out how urban sprawl affects the water body area decline in space. Two largest downtown lakes in Wuhan city, Donghu Lake located in central city and Tangxunhu Lake located in suburbs, are taken as case study area. A direction change index (DCI) is proposed to evaluate the changes of a specific land use in different directions. The results reveal that two downtown lakes are undergoing rapid water body area decline from 1991 to 2013, with decline rate are -0.022 in Donghu watershed and -0.011 in Tangxunhu watershed. 68.26% and 62.50% of the reduced water body is occupied by built-up land in Donghu watershed and Tangxunhu watershed, respectively. According to DCI, the water body reduce is highly correlated with built-up land increase in all direction. Moreover, it is found that in the Donghu watershed the north-west part suffered significant water body area decline, which is close to central city. While in Tangxunhu watershed, the area of water body declined in north-west, south-west and north-east part, and the area obstructed from central city by the lake was suffering less water body area decline. It is concluded that the water body area of downtown lakes are highly affected by the process of urban sprawl, and the lakes in central districts trends to suffer higher descend than that of the downtown lake located in suburbs. Meanwhile, even for the same downtown lake, the area orientating and close to the central city may suffer more rapid decline than the area that does not orientate to the central city.

  10. Land-cover changes in an urban lake watershed in a mega-city, Central China.

    PubMed

    Li, Yan; Zhao, Shuqing; Zhao, Kun; Xie, Ping; Fang, Jingyun

    2006-04-01

    Urbanization can exert a profound influence on land covers and landscape characteristics. In this study, we characterize the impact of urbanization on land cover and lacustrine landscape and their consequences in a large urban lake watershed, Donghu Lake watershed (the largest urban lake in China), Central China, by using Landsat TM satellite images of three periods of 1987, 1993 and 1999 and ground-based information. We grouped the land covers into six categories: water body, vegetable land, forested land, shrub-grass land, open area and urban land, and calculated patch-related landscape indices to analyze the effects of urbanization on landscape features. We overlaid the land cover maps of the three periods to track the land cover change processes. The results indicated that urban land continuously expanded from 9.1% of the total watershed area in 1987, to 19.4% in 1993, and to 29.6% in 1999. The vegetable land increased from 7.0% in 1987, 11.9% in 1993, to 13.9% in 1999 to sustain the demands of vegetable for increased urban population. Concurrently, continuous reduction of other land cover types occurred between 1987 and 1999: water body decreased from 30.4% to 23.8%, and forested land from 33.6% to 24.3%. We found that the expansion of urban land has at least in part caused a decrease in relatively wild habitats, such as urban forest and lake water area. These alterations had resulted in significant negative environmental consequences, including decline of lakes, deterioration of water and air quality, and loss of biodiversity.

  11. Environmental factors affecting chlorophyll-a concentration in tropical floodplain lakes, Central Brazil.

    PubMed

    de Oliveira Marcionilio, Suzana Maria Loures; Machado, Karine Borges; Carneiro, Fernanda Melo; Ferreira, Manuel Eduardo; Carvalho, Priscilla; Vieira, Ludgero Cardoso Galli; de Moraes Huszar, Vera Lúcia; Nabout, João Carlos

    2016-11-01

    Chlorophyll-a (Chl-a) has been widely used in the assessment and monitoring of aquatic environments. Local and regional factors can influence Chl-a concentrations; moreover, the connection between terrestrial and aquatic ecosystems is a major paradigm within aquatic ecology. Here, we investigate the spatial distribution of Chl-a concentrations in a tropical savannah floodplain in Central Brazil using a broad spatial data set (a 900-km north-south transect; 30 lakes). We determine the relative importance of local environmental variables (limnological and morphometric) and regional (land use) and spatial distances (spatial eigenvector) on Chl-a concentrations using partial linear regression. We evaluate the direct and indirect effects of local and regional variables on Chl-a with a path analysis. Our results indicate spatially autocorrelated patterns wherein lakes in closer proximity showed more similar levels of Chl-a than more distant lakes. Local environmental factors explained most variance in Chl-a (R (2)adj = 0.28; P = 0.02); more specifically, both lake area and total nitrogen significantly (P < 0.05) explained Chl-a concentrations (direct effects). Meanwhile, regional factors neither directly nor indirectly predicted Chl-a. Thus, internal processes, such as the resuspension of sediment (which is frequent in tropical floodplains), rather than external influences, were the main factors that explained Chl-a concentrations in this study. The importance of local variables in structuring Chl-a concentration may be used to guide the conservation of the aquatic ecosystems in these tropical floodplain lakes.

  12. The Mar Chiquita Lake: An indicator of intraplate deformation in the central plain of Argentina

    NASA Astrophysics Data System (ADS)

    Mon, Ricardo; Gutiérrez, Adolfo Antonio

    2009-10-01

    The Mar Chiquita saline lake is located in the lowest part of one of the largest endorreic saline basins of South America. With a surface area of 6000-6500 km 2, the lake is located in a tectonic depression with an asymmetric cross section. The Sierras Pampeanas foothills, (with altitudes near 1500 m) are to the west and a 100-m topographic high (San Guillermo high) is to the east whose western border is bounded by a buried Middle Pleistocene fault (the Tostado-Selva Fault). The main tributary of the lake is the Dulce River, which flows from north to south. The southward flow of the river was impeded by an obstacle that closed the Dulce Valley, generating the Mar Chiquita Lake. The megafans of the Primero, Segundo, and Tercero Rivers deposited a large amount of sediment against the faulted border of the San Guillermo high, generating an obstacle that impeded the normal flow of the rivers and diverted the Dulce and the Salado Rivers to their present positions. Precise data concerning the age of the impounding of Mar Chiquita does not exist, but lacustrine conditions are undoubtedly younger than the uplift of the San Guillermo high, which occurred in the Middle Pleistocene. The well-preserved dry valley of the Dulce River, located southward of Mar Chiquita, is still visible in satellite images and confirms the youth of the impounding. The observations introduced in this paper allow us to understand the origin of a significant feature of the central plains of South America. The generation of Mar Chiquita Lake and upstream wetlands produced a pronounced environmental change in the arid Chaco-Pampeana Plain, which favored human life by introducing changes in vegetation and fauna.

  13. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  14. Seasonal and interannual effects of hypoxia on fish habitat quality in central Lake Erie

    USGS Publications Warehouse

    Arend, Kristin K.; Beletsky, Dmitry; DePinto, Joseph; Ludsin, Stuart A.; Roberts, James J.; Rucinski, Daniel K.; Scavia, Donald; Schwab, David J.; Höök, Tomas O.

    2011-01-01

    1. Hypoxia occurs seasonally in many stratified coastal marine and freshwater ecosystems when bottom dissolved oxygen (DO) concentrations are depleted below 2–3 mg O2 L-1. 2. We evaluated the effects of hypoxia on fish habitat quality in the central basin of Lake Erie from 1987 to 2005, using bioenergetic growth rate potential (GRP) as a proxy for habitat quality. We compared the effect of hypoxia on habitat quality of (i) rainbow smelt, Osmerus mordax mordax Mitchill (young-of-year, YOY, and adult), a cold-water planktivore, (ii) emerald shiner, Notropis atherinoides Rafinesque (adult), a warm-water planktivore, (iii) yellow perch, Perca flavescens Mitchill (YOY and adult), a cool-water benthopelagic omnivore and (iv) round goby Neogobius melanostomus Pallas (adult) a eurythermal benthivore. Annual thermal and DO profiles were generated from 1D thermal and DO hydrodynamics models developed for Lake Erie’s central basin. 3. Hypoxia occurred annually, typically from mid-July to mid-October, which spatially and temporally overlaps with otherwise high benthic habitat quality. Hypoxia reduced the habitat quality across fish species and life stages, but the magnitude of the reduction varied both among and within species because of the differences in tolerance to low DO levels and warm-water temperatures. 4. Across years, trends in habitat quality mirrored trends in phosphorus concentration and water column oxygen demand in central Lake Erie. The per cent reduction in habitat quality owing to hypoxia was greatest for adult rainbow smelt and round goby (mean: -35%), followed by adult emerald shiner (mean: -12%), YOY rainbow smelt (mean: -10%) and YOY and adult yellow perch (mean: -8.5%). 5. Our results highlight the importance of differential spatiotemporally interactive effects of DO and temperature on relative fish habitat quality and quantity. These effects have the potential to influence the performance of individual fish species as well as population dynamics

  15. A potential new energy pathway in Central Lake Erie: The round goby connection

    USGS Publications Warehouse

    Johnson, T.B.; Bunnell, D.B.; Knight, C.T.

    2005-01-01

    Round gobies, invasive fish that entered Lake Erie in 1994, are altering energy, contaminant, and nutrient pathways. Our objective was to quantify how they alter energy pathways in the central basin of Lake Erie by describing their diet and identifying the degree to which predatory fish feed upon round gobies. We used bioenergetic models parameterized with data collected in the central basin between 1995 and 2002 to estimate the type and amount of prey eaten, the biomass accumulation rate for the round goby population, and a partitioning of the food energy into “new” energy derived from dreissenids as opposed to existing energy derived from zooplankton and non-dreissenid benthic prey. Mean (± SE) prey consumption peaked at 5.98 ± 2.17×104 tonnes wet mass in 1999 coincident with the maximum population size of 4.2 ± 1.5 billion round gobies. Zooplankton (40.2% by biomass) and dreissenid mussels (38.3%) dominated the prey consumed. Almost 90% of the zooplankton biomass was consumed by age-0 round gobies, while over 80% of the dreissenids were eaten by older ages. Standing stock biomass of round gobies ranged between 203 and 4,803 tonnes y−1 (interannual range), with an additional 475 to 8,943 tonnes of biomass accumulating through growth each year. Piscivorous fish showed an increasing reliance on round gobies as prey, with round gobies being the dominant prey fish in the diets of benthic-oriented predators. Hence, by being one of the few benthivores that exploit dreissenid mussels as prey, our analyses reveal that round gobies transfer new energy up the central Lake Erie food web.

  16. Population dynamics of Aedes albifasciatus (Diptera: Culicidae) south of Mar Chiquita Lake, central Argentina.

    PubMed

    Gleiser, R M; Gorla, D E; Schelotto, G

    2000-01-01

    Spatial and temporal changes in the abundance of adult female Aedes (Ochlerotatus) albifasciatus (Macquart) were studied using CDC miniature light traps at 7 sites along an 80-km transect parallel to the southern shore of Mar Chiquita Lake (central Argentina) during the rainy seasons between 1994 and 1997. Abundance was greatest and most variable at sites near larval habitats. Rainfall and an index combining rainfall and temperature predicted adult female abundance near larval habitats 7-15 d in advance. The spatial distribution of population abundance seemed to be influenced strongly by local factors, because temporal change at sampling sites located >10 km apart was asynchronous.

  17. Principal Facts for 463 Gravity Stations in the Vicinity of Tangle Lakes, East-Central Alaska

    USGS Publications Warehouse

    Morin, Robert L.; Glen, Jonathan M.G.

    2002-01-01

    During the summer of 2001, a gravity survey was conducted in the vicinity of Tangle Lakes, east-central Alaska. Measurements of 87 gravity stations were made. The Tangle Lakes area is located about 25 km west of Paxson and north of the Denali Highway. The gravity survey is located on the southwest corner of the Mt. Hayes and the northwest corner of the Gulkana 1:250,000 scale USGS topographic maps. The boundaries of the study area are 62 deg 30' to 63 deg 30' N. latitude and 145 deg 30' to 147 deg 00' W. longitude. A map showing the location of the study area is shown in figure 1. One gravity base station was used for control for this survey. This base station, TLIN is located at the Tangle Lakes Inn. The observed gravity of this station was calculated based on multiple ties to base stations ANCU in Anchorage, PALH in Palmer, BD27 in Gulkana, and base stations D42, and D57 along the Denali Highway.

  18. Hydrology of Lakes Clara and Vandercook in north-central Wisconsin

    USGS Publications Warehouse

    Wentz, D.A.; Rose, W.J.

    1991-01-01

    Hydrologic budgets show that lake inflow was dominated by precipitation (77 to 91 percent for Lake Clara and 79 to 87 percent for Vandercook Lake). Ground water accounted for the remaining inflow to Vandercook Lake; however, Lake Clara received approximately equal contributions from ground-water inflow and overland flow. Evaporation was the major form of lake outflow (59 to 75 percent for Lake Clara and 59 to 63 percent for Vandercook Lake). The remaining outflow from Vandercook Lake was to the ground-water system, but Lake Clara lost approximately equal amounts by surface and ground-water outflow. Hydraulic residence times were 4 to 5 years for both lakes. Chemical residence times for conservative constituents were 11 to 21 years for Lake Clara and 10 to 13 years for Vandercook Lake.

  19. Hydrology of the Hamilton lakes and vicinity, Polk County, central Florida

    USGS Publications Warehouse

    Anderson, Warren G.; Simonds, Edward P.

    1983-01-01

    The Hamilton lakes, headwaters of the eastern arm of the Peace River drainage system, consist of Lake Hamilton, Middle Lake Hamilton, and Little Lake Hamilton. The lakes, which are connected by canals that tend to equalize their levels, probably occupy coalesced sinkhole depressions. The drainage basin of Lake Hamilton contains several water-control structures which can alter the effective size of the area contributing water to the Hamilton lakes according to their gate settings. The chemical and biological conditions in the Hamilton lakes are such that the lakes are not sufficiently enriched to cause problems with excessive weed growth or algae blooms. (USGS)

  20. Late Holocene climate change at Goat Lake, Kenai Mountains, south-central Alaska

    NASA Astrophysics Data System (ADS)

    Daigle, T. A.; Kaufman, D. S.

    2006-12-01

    Lake sediments, glacier extents, and tree rings were used to reconstruct late Holocene climate changes from Goat Lake in the Kenai Mountains, south-central Alaska (60° 14' N/149° 54' W). Two sediment cores (3.7 and 5.6 m long) were dated with 16 AMS 14C ages and record changes in watershed (organic- matter content) and within-lake (biogenic silica) productivity since ~9500 cal yr BP. Sediment analyses focused on the last 1000 yr; this interval includes a sharp transition from gyttja to inorganic mud at ~1660 AD, which marks the fist time since Pleistocene deglaciation that the north goat outlet glacier (NGO) of the Harding Icefield overtopped the drainage divide at 590 m asl to spill meltwater into Goat Lake. One 14C age of ~1535 AD from a subfossil log in the NGO valley requires ~125 yr for the NGO to thicken 150 m to the elevation of the drainage divide where it remained until ~1930. Since ~1930, the NGO has thinned 150 m and retreated 1.4 km. Equilibrium-line altitudes (ELA) were reconstructed for 12 cirque glaciers nearby Goat Lake based on the accumulation-area ratio (AAR) method following field mapping of ice-marginal features formed during the maximum Little Ice Age (LIA) in the 19th century. Maximum LIA ELA data (AAR = 0.58) were compared with 1950 ELA and yield an average lowering of 50 ± 20 m. Application of the local lapse rate of 0.47°C/100 m indicates an average ablation-season temperature reduction of 0.3°C during the maximum LIA compared to 1950, assuming no change in winter precipitation. A new tree-ring chronology from 27 hemlock trees in the Goat Lake watershed correlates with mean March through August temperature from Kenai airport (r = 0.35) and a 207 yr reconstruction indicates an average temperature reduction of 1.0°C from 1800-1900 compared with 1930-1950. Assuming no change in winter precipitation, then a 1°C cooling should have been associated with an ELA lowering by 200 m. This did not occur, and we suggest that some degree of

  1. Genetic diversity of planktonic eukaryotes in high mountain lakes (Central Pyrenees, Spain).

    PubMed

    Triadó-Margarit, Xavier; Casamayor, Emilio O

    2012-09-01

    The genetic diversity of planktonic eukaryotic microorganisms (size range 3-40 µm) inhabiting 11 alpine lakes of the Central Pyrenees (Spain) was analysed by cloning and sequencing of the 18S rRNA gene. The selected lakes covered a wide range of environmental conditions representative of the regional landscape heterogeneity. Overall, we obtained 953 sequences (averaged length 750 bp) that were grouped in 343 representative OTUs (98% identity). The genetic richness was high, and the 18S rRNA gene sequences spread within nine high-rank taxonomic groups and grouped in 26 eukaryal classes. Most of the sequences affiliated with Stramenopiles (> 55% of total sequences, mostly Chrysophyceae), Cryptophyta and Alveolata (15% each). Three groups had relative abundance < 5%, i.e. Opisthokonta (mostly Fungi), Viridiplantae (mostly Chlorophyceae) and Rhizaria (cercomonads). Finally, minor groups were related to Katablepharidophyta, Euglenozoa and Telonemida. The lakes showed a different community structure being pH, and phosphorous and Chl a concentrations the main environmental drivers. The novelty level was high, and a quarter of the retrieved OTUs were notably divergent (< 97% identity) from any previously known sequence, mainly for Rhizaria and Opisthokonta. More than 50% of the sequences affiliated with clusters exclusively formed by uncultured protists. Cryptophyta and Viridiplantae showed the largest number of sequences closely related to cultured counterparts. This work is the first description of the genetic diversity of eukaryotic assemblages in ultraoligotrophic high mountain lakes, and the study unveils alpine environments as an important reservoir of microbial eukaryotic biodiversity. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

  2. Short-term cycle of eolian dust (Kosa) recorded in Lake Kawaguchi sediments, central Japan

    NASA Astrophysics Data System (ADS)

    Kyotani, Tomohiro; Koshimizu, Satoshi; Kobayashi, Hiroshi

    The fluctuation during the last 100 yr of the eolian dust (Kosa aerosol) originating from arid and semi-arid areas of China has been reconstructed by using the sediments from Lake Kawaguchi, central Japan with high temporal resolution. The quantification of Kosa contribution to the sediments was carried out by a new method using scanning electron microscopy-energy dispersive X-ray microanalysis (SEM-EDX) proposed by us. The correlation plot of (Na 2O+K 2O) contents against SiO 2 was used for individual Si-rich particles having SiO 2 content over 80%. The Kosa fraction of Si-rich particles in Lake Kawaguchi sediments during the last 100 yr is approximately 10-30%. The fluctuation of the Kosa fraction during the last 100 yr does not coincide with that of the total amount of Si-rich particles, because detrital components from Japanese igneous rocks control the fluctuation of the total number of Si-rich particles. The discrimination method based on single particle analysis is more effective than that of bulk analysis for the lake sediments formed by complex matrix components. We can first show a short-term (approximately 10-20 yr scale) cycle in Kosa aerosol fluctuation. Higher sedimentation rates (5-10 yr-cm) of the Lake Kawaguchi sediments and the new analytical method using SEM-EDX revealed a remarkable fluctuation pattern of Kosa aerosol, suggesting climate cycles much shorter than glacial-interglacial. Such short-term cycles may be related to sun-spots. The number of days of Kosa events during the last 30 yr, obtained by visual observation by Meteorological Agency of Japan, also supports the presence of such a short-term cycle.

  3. Variable viral and grazer control of prokaryotic growth efficiency in temperate freshwater lakes (French Massif Central).

    PubMed

    Ram, A S Pradeep; Palesse, S; Colombet, J; Sabart, M; Perriere, F; Sime-Ngando, T

    2013-11-01

    The effects of viral lysis and heterotrophic nanoflagellate grazing (top down forces) on prokaryotic mortality and their subsequent impact on their metabolism were estimated in the upper euphotic and deeper aphotic depth of 11 freshwater lakes located in the French Massif Central. The standing stocks of viruses (VA) and heterotrophic nanoflagellate (HNF) varied significantly (p < 0.05) with sampled depth. VA was substantially (twofold on an average) and significantly higher (p < 0.03) at the aphotic compared to euphotic depth, whereas the reverse was true (p < 0.02) for HNF. Among the prokaryote subgroup, high nucleic acid content prokaryotes explained for significant variability in the total VA and served as principle host target for viral proliferation. Like standing stocks, flagellate grazing and viral infection rates also followed similar patterns. In the investigated lakes, the mechanism for regulating prokaryotic production varied with sampled depth from grazing control in the euphotic to control due to viral lysis in the aphotic. We also tested the hypothesis of top down control on prokaryotic growth efficiency (PGE, which we used as an index of prokaryotic physiological and energetic status at the community level) at both depths. Overall, among the studied lakes, PGE varied widely (4-51 %) with significantly (p < 0.05) lower values in the aphotic (mean = 18 ± 4 %) than euphotic depth (mean = 32 ± 9 %). Contrasting observations on the top down control of PGE between sampled depths were observed. The presence of grazers was found to stimulate PGE at the euphotic, whereas viruses through their lytic infection had a strong negative impact on PGE at the aphotic depth. Such observed differences in PGE and the mechanism controlling prokaryotic production with depth could eventually have strong implication on carbon and nutrient flux patterns in the studied lakes.

  4. Morphotectonic setting of maar lakes in the Campo de Calatrava Volcanic Field (Central Spain, SW Europe)

    NASA Astrophysics Data System (ADS)

    Martín-Serrano, A.; Vegas, J.; García-Cortés, A.; Galán, L.; Gallardo-Millán, J. L.; Martín-Alfageme, S.; Rubio, F. M.; Ibarra, P. I.; Granda, A.; Pérez-González, A.; García-Lobón, J. L.

    2009-12-01

    In the Campo de Calatrava Volcanic Field (CCVF, Central Spain), the eruption of Pliocene-Pleistocene maar craters into two clearly distinct types of pre-volcanic rocks allows the observation and comparison of hard-substrate and soft-substrate maar lakes. Hard-substrate maars formed when phreatomagmatic processes affected the jointed, Paleozoic igneous and metamorphic rocks (hard substrate), giving rise to funnel-like maar lake basins. Soft-substrate maars resulted from phreatomagmatic volcanic processes affecting poorly-consolidated Pliocene sediments, forming bowl-like maar lake basins. Pre-volcanic bedrock determined the post-eruptive lacustrine architecture in the craters and favored a higher preservation of hard-substrate maars in comparison to soft-substrate maars. This is because the hard-substrate maars, surrounded by a deep stable crater wall, are more capable of collecting sediments in their basins. These sediments could be preserved for longer than similar deposits in broad, shallow maars with a soft substrate. Ancient soft-substrate maars do not usually preserve their original morphology well and can be identified only by their lacustrine deposits. Carbonate lacustrine/palustrine deposits surrounding a bowl-like depression are the remnants of this second type of maar lake, and allow reconstruction of the original morphology of ancient soft-substrate maar craters. Geophysical (electrical tomography ground surveys) and geomorphologic-geologic mapping techniques were combined with fieldwork and facies analysis in order to locate and accurately characterize the Pliocene-Pleistocene soft-substrate maar volcanic structures of the CCVF.

  5. Understanding the MIS 5e in Central America: the Chalco Lake perspective

    NASA Astrophysics Data System (ADS)

    Cardenes, G. M.; Lozano, S.; Correa-Metrio, A.; Bush, M. B.

    2013-05-01

    Southestern Mexico is a biogeographic divide between the Neotropics and temperate region. Prior work has established that Dansgaard-Oeschger and Heinrich events influenced Central America as well as North America, but there is a knowledge gap relating to rapid climate change associated with the termination and initiation of glacial episodes in the American tropics. Here we present pollen, charcoal and stratigraphic data derived from the lower part of a 122-m long composite sedimentary sequence from paleolake Chalco in Southeastern Mexico D.F. (19°14'40.99''N/98°53'30.99'', 2245 m.a.s.l.). This study established the paleoclimatic and vegetational dynamics of the northern Neotropics during MIS 6-4 using fossil pollen, charcoal and stratigraphic analysis. The history of Chalco Lake has been strongly influenced by volcanic activity around the basin, for example, four pumitic events and eight ash layers were found in the 20 m of core discussed here. Pollen data derived from the sediments showed abrupt changes in the vegetation assemblages throughout the period of study. Quercus, Pinus, Abies and Picea were dominant types at different times in the lake history reflecting changes in both temperature and precipitation. Our data indicate that at the peak of MIS5e Lake Chalco dried out, suggesting warm and dry conditions. Charcoal analysis indicated that except during the period when the lake dried out, natural fire was a component of this landscape. This study demonstrates that understanding MIS 5e, which was the last warm period before the present, is important to contextualize modern climate change and refine regional vegetation models.

  6. Ichthyoplankton assemblages of coastal west-central Lake Erie and associated habitat characteristics

    USGS Publications Warehouse

    McKenna, J.E.; Hunter, R. Douglas; Fabrizio, M.C.; Savino, J.F.; Todd, T.N.; Bur, M.

    2008-01-01

    Early life stage survival often determines fish cohort strength and that survival is affected by habitat conditions. The structure and dynamics of ichthyoplankton assemblages can tell us much about biodiversity and fish population dynamics, but are poorly understood in nearshore areas of the Great Lakes, where most spawning and nursery habitats exist. Ichthyoplankton samples were collected with a neuston net in waters 2-13 m deep weekly or biweekly from mid-April through August, during 3 years (2000-2002) as part of a study of fish assemblages in west-central Lake Erie. A suite of abiotic variables was simultaneously measured to characterize habitat. Cluster and ordination analyses revealed several distinct ichthyoplankton assemblages that changed seasonally. A lake whitefish (Coregonus clupeaformis) dominated assemblage appeared first in April. In May, assemblages were dominated by several percid species. Summer assemblages were overwhelmingly dominated by emerald shiner (Notropis atherinoides), with large gizzard shad (Dorosoma cepedianum) and alewife (Alosa pseudoharengus) components. This seasonal trend in species assemblages was also associated with increasing temperature and water clarity. Water depth and drift processes may also play a role in structuring these assemblages. The most common and widely distributed assemblages were not associated with substratum type, which we characterized as either hard or soft. The timing of hatch and larval growth separated the major groups in time and may have adaptive significance for the members of each major assemblage. The quality and locations (with reference to lake circulation) of spawning and nursery grounds may determine larval success and affect year class strength.

  7. Simulated influences of Lake Agassiz on the climate of central North America 11,000 years ago

    USGS Publications Warehouse

    Hostetler, S.W.; Bartlein, P.J.; Clark, P.U.; Small, E.E.; Solomon, A.M.

    2000-01-01

    Eleven thousand years ago, large lakes existed in central and eastern North America along the margin of the Laurentide Ice Sheet. The large-scale North American climate at this time has been simulated with atmospheric general circulation models, but these relatively coarse global models do not resolve potentially important features of the mesoscale circulation that arise from interactions among the atmosphere, ice sheet, and proglacial lakes. Here we present simulations of the climate of central and eastern North America 11,000 years ago with a high-resolution, regional climate model nested within a general circulation model. The simulated climate is in general agreement with that inferred from palaeoecological evidence. Our experiments indicate that through mesoscale atmospheric feedbacks, the annual delivery of moisture to the Laurentide Ice Sheet was diminished at times of a large, cold Lake Agassiz relative to periods of lower lake stands. The resulting changes in the mass balance of the ice sheet may have contributed to fluctuations of the ice margin, thus affecting the routing of fresh water to the North Atlantic Ocean. A retreating ice margin during periods of high lake level may have opened an outlet for discharge of Lake Agassiz into the North Atlantic. A subsequent advance of the ice margin due to greater moisture delivery associated with a low lake level could have dammed the outlet, thereby reducing discharge to the North Atlantic. These variations may have been decisive in causing the Younger Dryas cold even.

  8. Recent increases in atmospheric deposition of mercury to North-Central Wisconsin lakes inferred from sediment analyses

    USGS Publications Warehouse

    Rada, R.G.; Wiener, J.G.; Winfrey, M.R.; Powell, D.E.

    1989-01-01

    Profiles of total mercury (Hg) concentrations in sediments were examined in 11 lakes in north-central Wisconsin having a broad range of pH (5.1 to 7.8) and alkalinity (-12 to 769 μeq/L). Mercury concentrations were greatest in the top 15 cm of the cores and were much lower in the deeper strata. The Hg content in the most enriched stratum of individual cores ranged from 0.09 to 0.24 μg/g dry weight, whereas concentrations in deep, precolonial strata ranged from 0.04 to 0.07 μg/g. Sediment enrichment factors varied from 0.8 to 2.8 and were not correlated with lake pH. The increase in the Hg content of recent sediments was attributed to increased atmospheric deposition of the metal. Eight of the 11 systems studied were low-alkalinity lakes that presumably received most (≥90%) of their hydrologic input from precipitation falling directly onto the lake surface. Thus, the sedimentary Hg in these lakes seems more likely linked to direct atmospheric deposition onto the lake surfaces than to influxes from the watershed. The data imply that a potentially significant fraction of the high Hg burdens measured in game fish in certain lakes in north-central Wisconsin originated from atmospheric sources.

  9. Regional vegetation patterns at lake Son Kul reveal Holocene climatic variability in central Tien Shan (Kyrgyzstan, Central Asia)

    NASA Astrophysics Data System (ADS)

    Mathis, Marie; Sorrel, Philippe; Klotz, Stefan; Huang, Xiangtong; Oberhänsli, Hedi

    2014-04-01

    A multiproxy study was conducted on Holocene sediments from the alpine lake Son Kul (3010 m a.s.l, 41°48‧33N/75°07‧38E) in central Tien Shan (Kyrgyzstan). The combination of high-resolution pollen, palynofacies and magnetic susceptibility data allowed reconstruction of changes in sedimentary and vegetation dynamics regionally at Son Kul between 8350 and ca 2000 cal. BP. Using pollen data to quantify climatic parameters, a quantitative reconstruction of climatic conditions was performed using the "Modern Analogue Vegetation types" (MAV) method and a ranged index of seasonality. The most temperate (e.g. moister) climate conditions occurred between 8350 and 5000-4500 cal. BP when alpine meadow vegetation was enriched in plants requiring moister conditions and trees developed regionally. Conversely, more continental and arid conditions prevailed after 4500 cal. BP with the decline of arboreal vegetation (especially Juniperus) and the extension of an alpine steppe-meadow along with a regional decrease in Poaceae. This climate transition was associated with a change in seasonality as the continentality greatly intensified after 5000-4500 cal. BP. Our results are consistent with other records from the Tien Shan range and the Chinese Province Xinjiang showing that relatively wet conditions prevailed regionally before 5000 cal. BP, whereas reduced moisture conditions were established after that time. From a more global perspective, we highlight that regional rainfall in central Tien Shan and western Central Asia is likely to be predominantly controlled by the Eastern Mediterranean cyclonic system and North Atlantic climate, as based on the close correspondence between climatic archives from western Central Asia, the Levant, the Eastern Mediterranean and Caspian Sea regions. However, the effect of monsoonal dynamics on the regional climatic system in central Tien Shan still remains dubious, since recent modelling studies have shown that no dynamic link exists between

  10. Potential impact of Chironomus plumosus larvae on hypolimnetic oxygen in the central basin of Lake Erie

    USGS Publications Warehouse

    Soster, Frederick M.; Matisoff, Gerald; Schloesser, Donald W.; Edwards, William J.

    2015-01-01

    Previous studies have indicated that burrow-irrigating infauna can increase sediment oxygen demand (SOD) and impact hypolimnetic oxygen in stratified lakes. We conducted laboratory microcosm experiments and computer simulations with larvae of the burrowing benthic midge Chironomus plumosus to quantify burrow oxygen uptake rates and subsequent contribution to sediment oxygen demand in central Lake Erie. Burrow oxygen uptake and water flow velocities through burrows were measured using oxygen microelectrodes and hot film anemometry, respectively. Burrow oxygen consumption averaged 2.66 × 10− 10 (SE = ± 7.82 × 10− 11) mol O2/burrow/s at 24 °C and 9.64 × 10− 10 (SE = ± 4.86 × 10− 10) mol O2/burrow/s at 15 °C. In sealed microcosm experiments, larvae increased SOD 500% at 24 °C (density = 1508/m2) and 375% at 15 °C (density = 864/m2). To further evaluate effects of densities of C. plumosus burrows on SOD we developed a 3-D transport reaction model of the process. Using experimental data and chironomid abundance data in faunal surveys in 2009 and 2010, we estimated that bioirrigation by a population of 140 larvae/m2 could account for between 2.54 × 10− 11 mol/L/s (model results) and 5.58 × 10− 11 mol/L/s (experimental results) of the average 4.22 × 10− 11 mol/L/s oxygen depletion rate between 1970 and 2003, which could have accounted for 60–132% of the oxygen decline. At present, it appears that the population density of this species may be an important factor in development of hypoxic or anoxic conditions in central Lake Erie.

  11. Two times lowering of lake water at around 48 and 38 ka, caused by possible earthquakes, recorded in the Paleo-Kathmandu lake, central Nepal Himalaya

    NASA Astrophysics Data System (ADS)

    Sakai, Harutaka; Fujii, Rie; Sugimoto, Misa; Setoguchi, Ryoko; Paudel, Mukunda Raj

    2016-02-01

    Sedimentary facies and micro-fossil analyses, and AMS14C dating were performed in order to reveal the water-level fall events and draining process of the lake (Paleo-Kathmandu Lake) that existed in the past in the Central Nepal Himalaya. The sedimentary facies change from the lacustrine Kalimati Formation to the deltaic Sunakothi Formation in the southern and central Kathmandu basin, and the abrupt and prominent increase of phytoliths Bambusoideae and Pediastrum, and contemporaneous decrease of sponge spicule and charcoal grains around 48 and 38 ka support the lowering of water level at these times. According to the pollen analysis, both events occurred under rather warm and wet climate, thus supporting that they were triggered by tectonic cause and not by climate change. The first event might be linked to a possible occurrence of a large earthquake with an epicenter in the vicinity of the Paleo-Kathmandu Lake. The occurrence of a mega landslide in Langtang area close to the north of the Kathmandu Valley producing pseudotachylite dated at 51 ± 13 ka could be linked to this earthquake. Finally, the water was completely drained out from the remnant lake at the central part of the Kathmandu basin by ca.12 ka.

  12. Mapping lake level changes using ICESat/GLAS satellite laser altimetry data: a case study in arid regions of central Asia

    NASA Astrophysics Data System (ADS)

    Li, JunLi; Fang, Hui; Yang, Liao

    2011-12-01

    Lakes in arid regions of Central Asia act as essential components of regional water cycles, providing sparse but valuable water resource for the fragile ecological environments and human lives. Lakes in Central Asia are sensitive to climate change and human activities, and great changes have been found since 1960s. Mapping and monitoring these inland lakes would improve our understanding of mechanism of lake dynamics and climatic impacts. ICESat/GLAS satellite laser altimetry provides an efficient tool of continuously measuring lake levels in these poorly surveyed remote areas. An automated mapping scheme of lake level changes is developed based on GLAS altimetry products, and the spatial and temporal characteristics of 9 typical lakes in Central Asia are analyzed to validate the level accuracies. The results show that ICESat/GLAS has a good performance of lake level monitoring, whose patterns of level changes are the same as those of field observation, and the max differences between GLAS and field data is 3cm. Based on the results, it is obvious that alpine lakes are increasing greatly in lake levels during 2003-2009 due to climate change, while open lakes with dams and plain endorheic lakes decrease dramatically in water levels due to human activities, which reveals the overexploitation of water resource in Central Asia.

  13. Development stages of hazardous mountain lakes and simulation of their outbursts (Central Caucasus, Russia; Sichuan mountain region, China).

    NASA Astrophysics Data System (ADS)

    Kidyaeva, Vera; Krylenko, Inna; Chernomorets, Sergey; Petrakov, Dmitry

    2013-04-01

    The importance of mountain lakes studies is related to the increasing threat of natural disasters, associated with lake outbursts and debris flows formation, because of population growth on exposed areas. The outburst hazard has not been sufficiently researched, there is a lack of data because of the lakes inaccessibility and remote sensing data is usually not detailed enough. The main scientific topics include assessment of outburst possibility and further simulation of possible outbursts scenarios. There are two types of mountain lakes: glacial (cirque, cirque-moraine, barrier-moraine, glacial-barrier, etc.) lakes and barrier (landslide, rockfall, debris flow, etc.) lakes. The first type was studied in the Central Caucasus (Russia), and the second type - in the Sichuan mountain region (China). The group of scientists, including authors, has been monitoring glacial lakes in the Mnt. Elbrus area for more than ten years. The unique data were collected, including detailed hydrological characteristics of more than ten lakes (water level dynamics, temperature, morphometrical characteristics, water balance components, etc.). Outbursts of at least three glacial lakes were observed. Hydrological characteristics of landslide Tangjiashan Lake were collected with Chinese colleagues during field studies in 2010 and 2011 years. Analysis of the collected data was used to understand the outburst mechanisms, formation factors, dam breaking factors, development stages of mountain lakes. Statistical methods of analysis in this case can be applied with some limitations because of the lack of sufficient monitoring objects, and therefore the results has been verified by experts. All types of possible outbursts mechanisms were divided by the authors into five groups: geomorphologic (caused by changes in lake dams), seismic, or geodynamic (caused by seiches, waves from rockfalls, landslides), glacial (caused by breaks in impounding glaciers, ice floating and melting), water

  14. Evidence of Uppermost Proterozoic to Lower Cambrian miogeoclinal rocks and the Mojave-Snow Lake Fault: Snow Lake Pendant, central Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Lahren, Mary M.; Schweickert, Richard A.; Mattinson, James M.; Walker, J. Douglas

    1990-12-01

    Displaced uppermost Precambrian to Lower Cambrian miogeoclinal strata occur within Snow Lake pendant in the central Sierra Nevada. These rocks have been correlated with the Stirling Quartzite, the Wood Canyon Formation, the Zabriskie Quartzite, and the Carrara Formation in the western Mojave Desert and the San Bernardino Mountains (Lahren and Schweickert, 1989; Lahren, 1989). This correlation is based on new, updated, and previously reported data including (1) lithologic similarities, (2) overall stratigraphic sequence, (3) vertical sequence within individual formations, (4) approximate stratigraphic thicknesses, (5) Skolithos in the correct stratigraphie position, (6) depositional environments, and (7) petrographic character and provenance of quartz arenites. The correlation is strengthened by the fact that Snow Lake pendant and the western Mojave share many other close similarities including (1) initial 87Sr/86Sr ratios of associated granitic rocks >0.706, (2) passive margin tectonic setting of Precambrian to Cambrian miogeoclinal rocks, (3) dikes of the Independence dike swarm, (4) possible Lower Triassic overlap sequence, the Fairview Valley Formation, (5) petrographically similar gabbroic complexes of the same age, (6) associated eugeoclinal rocks, and (7) identical(?) pre-Tertiary structural configuration. New U/Pb zircon geochronology unequivocally shows that dikes at Snow Lake pendant are coeval with the Independence dike swarm of the eastern Sierra and the western Mojave desert and that associated gabbroic complexes in both the Mojave and Snow Lake pendant are the same age. Correlation of Snow Lake pendant with the western Mojave requires about 400 km of dextral displacement of the rocks of Snow Lake pendant, together with associated rocks (Snow Lake block), from the western Mojave Desert along the Mojave-Snow Lake fault. Displacement most likely occurred after 150 Ma, the age of the Independence dike swarm, and before about 110 Ma, the age of major

  15. Origin and evolution of Sariñena Lake (central Ebro Basin): A piping-based model

    NASA Astrophysics Data System (ADS)

    Castañeda, Carmen; Javier Gracia, F.; Rodríguez-Ochoa, Rafael; Zarroca, Mario; Roqué, Carles; Linares, Rogelio; Desir, Gloria

    2017-08-01

    The origin and nature of the numerous lakes in the central Ebro Basin have been interpreted according to the prevailing arid or semiarid conditions, the easily-eroded materials and the solubility of the gypsum- and/or carbonate-rich Tertiary/Cenozoic substratum, involving important dissolution (karstic) and/or aeolian deflation. However, the origin of Sariñena Lake, the largest in the central Ebro Basin, remains unknown since the typical lake-generating processes in the region are not applicable. This work provides significant clues to the genesis and evolution of Sariñena Lake in a regional context. The combination of geomorphological mapping and high resolution LiDAR data together with sedimentological observations, the characterisation of soils and sediments around the lake, and the application of high-resolution geophysical techniques suggest that piping is the major genetic process driving the evolution of the Sariñena depression and lake. Field evidence demonstrates that piping is, at present, the most important erosive process in the region, generating significant collapse and surface lowering. Sariñena Lake is located within a deep endorheic depression excavated from Na-rich Tertiary materials. This work hypothesises that once an early, fluvially-originated palustrine area had developed, the progressive lowering of the regional water table linked to regional fluvial incision favoured the establishment of a hydrological gradient high enough to trigger piping processes within the claystones and siltstones underlying the original palustrine area. The Quaternary evolution of the Sariñena lacustrine basin was then controlled by successive water table fluctuations, linked to different phases of incision and alluvial deposition in the surrounding fluvial systems. All the evidence supporting a piping-related origin for this lake, together with examples of lakes generated by similar processes in different contexts, is used to propose a new genetic type of

  16. High-resolution single-channel seismic reflection surveys of Orange Lake and other selected sites of north central Florida

    USGS Publications Warehouse

    Kindinger, Jack G.; Davis, Jeffrey B.; Flocks, James G.

    1994-01-01

    The potential fluid exchange between lakes of north central Florida and the Floridan aquifer and the process by which exchange occurs is of critical concern to the St. Johns Water Management District. High-resolution seismic tools with relatively new digital technology were utilized in collecting geophysical data from Orange, Kingsley, Lowry and Magnolia Lakes, and the Drayton Island area of St. Johns River. The data collected shows the application of these techniques in understanding the formation of individual lakes, thus aiding in the management of these natural resources by identifying breaches or areas where the confining units are thin or absent between the water bodies and the Floridan aquifer. Orange Lake, the primary focus of the study, is a shallow flooded plain that was formed essentially as an erosional depression in the clayey Hawthorn formation. The primary karstic features identified in the lake were cover subsidence, cover collapse and buried sinkholes structures in various sizes and stages of development. Orange Lake was divided into three areas southeast, southwest, and north-central. Karst features within the southeast area of Orange Lake are mostly cover subsidence sinkholes and associated features. Many of the subsidence features found are grouped together to form larger composite sinkholes, some greater than 400 m in diameter. The size of these composite sinkholes and the number of buried subsidence sinkholes distinguish the southeast area from the others. The potential of lake waters leaking to the aquifer in the southeast area is probably controlled by the permeability of the cover sediments or by fractures that penetrate the lake floor. The lake bottom and subsurface of the north-central areas are relatively subsidence sinkholes that have no cover sediments overlying them, implying that the sinks have been actively subsiding with some seepage into the aquifer from the lake in this area due to the possible presence of the active subsidence

  17. The Central Lake Malawi (Nyasa) Rift: single or multiple rift segments?

    NASA Astrophysics Data System (ADS)

    McCartney, T.; Scholz, C. A.; Shillington, D. J.; Accardo, N. J.; Chindandali, P. R. N.; Kamihanda, G.

    2015-12-01

    Accommodation zones connect rift segments, which are fundamental elements of continental rift architecture. The sedimentary record aids our assessment of the evolution of this linkage. The central basin of Lake Malawi is one of the most structurally complex regions of the Malawi Rift. Border fault margins have been interpreted on both shorelines; three structures within the basin have been interpreted as segments of a corresponding accommodation zone. We investigate these structures by integrating single- and multi-channel reflection seismic data, including new MCS acquired in 2015 for the SEGMeNT project. The stratigraphic record in the central basin, inferred from seismic reflection profiles, provides compelling evidence that most fault-related subsidence is accommodated by the western border fault. Strata on both sides of all three structures dip to the west. The pre-rift basement in the sub-basin west of the central structure is considerably deeper (~ 4 s TWTT sub-bottom) than that in the broader eastern sub-basin (~ 2.5 s TWTT sub-bottom). A syncline in the eastern sub-basin shows little variation in seismic facies, particularly over the last 1.3 m.y. In contrast, the western sub-basin exhibits seismic facies indicative of fluvial input from two major rivers, siliciclastic input from the border fault footwall rising > 1000 m above lake level, and mud diapirs in the deepest part of the sub-basin. Horizons pierced by these diapirs onlap the central structure, suggesting diapir rise postdates relative uplift of the structure. Correlations with the age model from a 2005 scientific drilling project will better constrain this timing. The structural high helps focus siliciclastic sediments into the sub-basin, resulting in the overpressure conditions required for mud diapirism. We hypothesize that the diapirs are the result of sediment loading in the deep main depocenter of the central basin rather than fault mechanisms. The basement highs in the central basin control

  18. Sedimentation and subsidence patterns in the central and north basins of Lake Baikal from seismic stratigraphy

    USGS Publications Warehouse

    Moore, T.C.; Klitgord, Kim D.; Golmshtok, A.J.; Weber, E.

    1997-01-01

    Comparison of sedimentation patterns, basement subsidence, and faulting histories in the north and central basins of Lake Baikal aids in developing an interbasinal seismic stratigraphy that reveals the early synrift evolution of the central portion of the Baikal rift, a major continental rift system. Although there is evidence that the central and northern rift basins evolved at approximately the same time, their sedimentation histories are markedly different. Primary sediment sources for the initial rift phase were from the east flank of the rift; two major deltas developed adjacent to the central basin: the Selenga delta at the south end and the Barguzin delta at the north end. The Barguzin River system, located at the accommodation zone between the central and north basins, also fed into the southern part of the north basin and facilitated the stratigraphic linkage of the two basins. A shift in the regional tectonic environment in the mid Pliocene(?) created a second rift phase distinguished by more rapid subsidence and sediment accumulation in the north basin and by increased subsidence and extensive faulting in the central basin. The Barguzin delta ceased formation and parts of the old delta system were isolated within the north basin and on Academic Ridge. These isolated deltaic deposits provide a model for the development of hydrocarbon plays within ancient rift systems. In this second tectonic phase, the dominant sediment fill in the deeper and more rapidly subsiding north basin shifted from the flexural (eastern) margin to axial transport from the Upper Angara River at the north end of the basin.

  19. Seasonal drainage of supraglacial lakes on debris-covered glaciers in the Tien Shan Mountains, Central Asia

    NASA Astrophysics Data System (ADS)

    Narama, Chiyuki; Daiyrov, Mirlan; Tadono, Takeo; Yamamoto, Minako; Kääb, Andreas; Morita, Reira; Ukita, Jinro

    2017-06-01

    Using field surveys in 2013, 2014, and 2016 plus satellite data from the 1999-2015 period, we analyze the seasonal drainage cycle of supraglacial lakes on seven debris-covered glaciers in the central Tien Shan. We characterize this cycle by the number of lakes and their water levels. The cycle of the Southern Inylchek Glacier starts to increase in the beginning of April, reaches a maximum in May-June, and decreases sharply in June-July. The increase in April to June comes from an inflow of meltwater from snow and ice, and the subsequent decrease arises from a greater connectivity to the englacial drainage network. For the Southern Inylchek Glacier, 94% of the supraglacial lakes that exist and appear during 2013-2015 drain during all three years, indicating that most lakes could connect to the englacial drainage network for three years. Concerning the water level, lakes in close proximity and with the same base-level tend to synchronize their seasonal water levels through the englacial channels. Although the maximum water level of the three-year, field-measured lake is about the same from 2014 through 2016, the date of maximum water level varies between mid-May and mid-June. During this period, the lifetime and size of the supraglacial lakes are controlled by the timing of their connectivity to the englacial drainage network.

  20. Biomineralization of iron-phosphates in the water column of Lake Pavin (Massif Central, France)

    NASA Astrophysics Data System (ADS)

    Cosmidis, Julie; Benzerara, Karim; Morin, Guillaume; Busigny, Vincent; Lebeau, Oanez; Jézéquel, Didier; Noël, Vincent; Dublet, Gabrielle; Othmane, Guillaume

    2014-02-01

    The availabilities of iron and phosphorus have considerably impacted biological productivity in past and present natural aquatic environments, and therefore have been key regulators of climate changes over geological time scales. Microbial organisms are known to play important roles in reactions that drive Fe and P cycling at redox interfaces in Earth's surface environments. Here we study the depth variations of Fe and P speciation in Lake Pavin (Massif Central, France), a deep (bottom depth ˜92 m) and permanently stratified lake with anoxic and ferruginous conditions in the water column below ˜60 m depth. We particularly focus on the potential roles of microbes on Fe and P transformations and traces left by these processes in the sedimenting particular matter. Bulk chemical analyses, powder X-ray diffraction and X-ray absorption spectroscopy (XAS) at the Fe K-edge were performed to characterize the mineralogy and Fe oxidation state of solid particles at different depths in the water column and in sediments deposited at the bottom of the lake. Fe is mainly hosted by Fe(III)-(oxyhydr)oxides and phyllosilicates in the shallower oxygenated water column of the lake (25 m). The amount of Fe in suspended matter increases with depth, and an additional amorphous Fe(II)-Fe(III)-phosphate phase is detected close to the chemocline (at 56 m depth), while vivianite (an Fe(II)-phosphate with a formula of Fe(II)3(PO4)2·8(H2O)) becomes dominant in the deeper anoxic water (67 m and 86 m depths). Fe-(oxyhydr)oxides are preserved down to these depths in the water column suggesting that Fe-reduction has little impact on the particulate Fe budget over the monimolimnion. These Fe-(oxyhydr)oxides undergo reductive dissolution at the surface of the sediments, where vivianite is the main Fe-bearing phase. These results are confirmed by imaging at the micrometer and nano-scales using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and synchrotron-based scanning

  1. Late Holocene Drought Record From Castor Lake, North-Central Washington State

    NASA Astrophysics Data System (ADS)

    Nelson, D. B.; Abbott, M. B.; Polissar, P. J.; Finney, B.

    2006-12-01

    The effects of recent and historic drought in the North American west provide motivation for understanding the natural variability and underlying causes of these events. We present a 6,000-year lake sediment record of water balance from Washington State in an effort to address these questions. A series of overlapping sediment cores were collected and chronological control was established through a combination of radiocarbon, tephrochronology, and cesium isotope activity. Modern basin morphometry and lake water oxygen and hydrogen isotope data indicate closed-basin hydrology and the strong influence of evaporative enrichment on lake water composition, and therefore sensitivity of the system to changes in regional water balance and drought. Samples of endogenic aragonite precipitates were isolated from sediment cores at an average sampling interval of 3.7mm, corresponding to a temporal resolution of approximately 7 years. Grayscale data were generated from digital images of the cores collected under controlled light conditions and are shown to track changes in oxygen isotope values, with darker layers corresponding to periods of increased isotopic composition. In addition to supporting the notion that oxygen isotope data are primarily recording changes in water balance as opposed to changes in water source or temperature, the increased resolution of the grayscale record improves the resolution of the climate signal to the sub-millimeter scale of the laminations. There is a significant correlation between the most recent portion of the Castor Lake grayscale record and a 1,500-yr Palmer Drought Severity Index (PDSI) reconstruction from central Washington (1). The strong association between changes in the Castor Lake record and changes in the PDSI reconstruction provides convincing method validation and strengthens the interpretation of both as drought signals. Spectral analyses of the grayscale record using singular spectrum analysis (SSA), maximum entropy method (MEM

  2. Comparison of evaporation at two central Florida lakes, April 2005–November 2007

    USGS Publications Warehouse

    Swancar, Amy

    2015-09-25

    Both lakes are seepage lakes (no surface-water inflow or outflows) that are dependent on groundwater inflow from their basins to offset an atmospheric deficit, because long-term rainfall in this area is less than evaporation. The Lake Starr basin, where sandy, well-drained ridges surround the lake, has a greater capacity to store infiltrating rain than the Lake Calm basin, which is flat and has poorly drained soils. The storage capacities of the basins affect groundwater exchange with the lakes. Rainfall and net groundwater exchange, which is related to basin characteristics, varied more between these two lakes than did evaporation during this study.

  3. Variability of Water Chemistry in Tundra Lakes, Petuniabukta Coast, Central Spitsbergen, Svalbard

    PubMed Central

    Mazurek, Małgorzata; Paluszkiewicz, Renata; Rachlewicz, Grzegorz; Zwoliński, Zbigniew

    2012-01-01

    Samples of water from small tundra lakes located on raised marine terraces on the eastern coast of Petuniabukta (Ebbadalen, Central Spitsbergen) were examined to assess the changes in water chemistry that had occurred during the summer seasons of 2001–2003 and 2006. The unique environmental conditions of the study region include the predominance of sedimentary carbonate and sulphate rocks, low precipitation values, and an active permafrost layer with a maximum thickness of 1.2 m. The average specific electric conductivity (EC) values for the three summer seasons in the four lakes ranged from 242 to 398 μS cm−1. The highest EC values were observed when the air temperature decreased and an ice cover formed (cryochemical effects). The ion composition was dominated by calcium (50.7 to 86.6%), bicarbonates (39.5 to 86.4%), and sulphate anions. The high concentrations of HCO3 −, SO4 2−, and Ca2+ ions were attributed to the composition of the bedrock, which mainly consists of gypsum and anhydrite. The average proportion of marine components in the total load found in the Ebbadalen tundra lake waters was estimated to be 8.1%. Precipitation supplies sulphates (as much as 69–81%) and chlorides (14–36%) of nonsea origin. The chief source of these compounds may be contamination from the town of Longyearbyen. Most ions originate in the crust, the active layer of permafrost, but some are atmospheric in origin and are either transported or generated in biochemical processes. The concentrations of most components tend to increase during the summer months, reaching a maximum during freezing and partially precipitating onto the bottom sediments. PMID:22654629

  4. Variability of water chemistry in Tundra Lakes, Petuniabukta Coast, Central Spitsbergen, Svalbard.

    PubMed

    Mazurek, Małgorzata; Paluszkiewicz, Renata; Rachlewicz, Grzegorz; Zwoliński, Zbigniew

    2012-01-01

    Samples of water from small tundra lakes located on raised marine terraces on the eastern coast of Petuniabukta (Ebbadalen, Central Spitsbergen) were examined to assess the changes in water chemistry that had occurred during the summer seasons of 2001-2003 and 2006. The unique environmental conditions of the study region include the predominance of sedimentary carbonate and sulphate rocks, low precipitation values, and an active permafrost layer with a maximum thickness of 1.2 m. The average specific electric conductivity (EC) values for the three summer seasons in the four lakes ranged from 242 to 398 μS cm(-1). The highest EC values were observed when the air temperature decreased and an ice cover formed (cryochemical effects). The ion composition was dominated by calcium (50.7 to 86.6%), bicarbonates (39.5 to 86.4%), and sulphate anions. The high concentrations of HCO(3) (-), SO(4) (2-), and Ca(2+) ions were attributed to the composition of the bedrock, which mainly consists of gypsum and anhydrite. The average proportion of marine components in the total load found in the Ebbadalen tundra lake waters was estimated to be 8.1%. Precipitation supplies sulphates (as much as 69-81%) and chlorides (14-36%) of nonsea origin. The chief source of these compounds may be contamination from the town of Longyearbyen. Most ions originate in the crust, the active layer of permafrost, but some are atmospheric in origin and are either transported or generated in biochemical processes. The concentrations of most components tend to increase during the summer months, reaching a maximum during freezing and partially precipitating onto the bottom sediments.

  5. Twentieth century atmospheric metal fluxes into Central Park Lake, New York City

    SciTech Connect

    Chillrud, S.N.; Simpson, H.J.; Bopp, R.F.

    1999-03-01

    It is generally assumed that declining atmospheric lead concentrations in urban centers during the 1970s and 1980s were due almost entirely to the progressive introduction of unleaded gasoline. However, most environmental data are from monitoring programs that began only two to three decades ago, which limits their usefulness. Here, trace metal and radionuclide data from sediment cores in Central Park Lake provide a record of atmospheric pollutant deposition in New York City through the 20th century, which suggests that leaded gasoline combustion was not the dominant source of atmospheric lead for NYC. Lead deposition rates, normalized to known Pb-210 atmospheric influxes, were extremely high, reaching maximum values from the late 1930s to early 1960s, decades before maximum emissions from combustion of leaded gasoline. Temporal trends of lead, zinc, and tin deposition derived from the lake sediments closely resemble the history of solid waste incineration in New York City. Furthermore, widespread use of solid waste incinerators in the United States and Europe over the last century suggests that solid waste incineration may have provided the dominant source of atmospheric lead and several other metals to many urban centers.

  6. Twentieth Century Atmospheric Metal Fluxes into Central Park Lake, New York City

    PubMed Central

    CHILLRUD, STEVEN N.; BOPP, RICHARD F.; SIMPSON, H. JAMES; ROSS, JAMES M.; SHUSTER, EDWARD L.; CHAKY, DAMON A.; WALSH, DAN C.; CHOY, CRISTINE CHIN; TOLLEY, LAEL-RUTH; YARME, ALLISON

    2011-01-01

    It is generally assumed that declining atmospheric lead concentrations in urban centers during the 1970s and 1980s were due almost entirely to the progressive introduction of unleaded gasoline. However, most environmental data are from monitoring programs that began only two to three decades ago, which limits their usefulness. Here, trace metal and radionuclide data from sediment cores in Central Park Lake provide a record of atmospheric pollutant deposition in New York City through the 20th century, which suggests that leaded gasoline combustion was not the dominant source of atmospheric lead for NYC. Lead deposition rates, normalized to known Pb-210 atmospheric influxes, were extremely high, reaching maximum values (>70 μg cm−2 yr−1) from the late 1930s to early 1960s, decades before maximum emissions from combustion of leaded gasoline. Temporal trends of lead, zinc, and tin deposition derived from the lake sediments closely resemble the history of solid waste incineration in New York City. Furthermore, widespread use of solid waste incinerators in the United States and Europe over the last century suggests that solid waste incineration may have provided the dominant source of atmospheric lead and several other metals to many urban centers. PMID:21850150

  7. Twentieth Century Atmospheric Metal Fluxes into Central Park Lake, New York City.

    PubMed

    Chillrud, Steven N; Bopp, Richard F; Simpson, H James; Ross, James M; Shuster, Edward L; Chaky, Damon A; Walsh, Dan C; Choy, Cristine Chin; Tolley, Lael-Ruth; Yarme, Allison

    1999-03-01

    It is generally assumed that declining atmospheric lead concentrations in urban centers during the 1970s and 1980s were due almost entirely to the progressive introduction of unleaded gasoline. However, most environmental data are from monitoring programs that began only two to three decades ago, which limits their usefulness. Here, trace metal and radionuclide data from sediment cores in Central Park Lake provide a record of atmospheric pollutant deposition in New York City through the 20th century, which suggests that leaded gasoline combustion was not the dominant source of atmospheric lead for NYC. Lead deposition rates, normalized to known Pb-210 atmospheric influxes, were extremely high, reaching maximum values (>70 μg cm(-2) yr(-1)) from the late 1930s to early 1960s, decades before maximum emissions from combustion of leaded gasoline. Temporal trends of lead, zinc, and tin deposition derived from the lake sediments closely resemble the history of solid waste incineration in New York City. Furthermore, widespread use of solid waste incinerators in the United States and Europe over the last century suggests that solid waste incineration may have provided the dominant source of atmospheric lead and several other metals to many urban centers.

  8. Hydrology of the Floral City Pool of Tsala Apopka Lake, west-central Florida

    USGS Publications Warehouse

    Bradner, L.A.

    1988-01-01

    Tsala Apopka Lake, in west-central Florida, has an area of about 19,000 acres and is divided into three water-management pools, with the Floral City Pool, the most upgradient. The Floral City Pool, which has a surface area of approximately 4,750 acres, contains an extensive combination of lakes, wetlands, and connecting canals. The Pool receives inflow from the Withlacoochee River through two canals. Outflow is through one manmade canal and one natural slough. Canal flow is partially controlled by manmade structures. A cumulative deficit of 19.4 inches of rainfall from August 1984 through May 1985 reduced surface-water inflow to the Floral City Pool to about 0.5 cu ft/sec by May 1985. During May 1985, pool levels declined approximately 0.04 ft/day. By the end of May, there was no observable outflow. From June 1985 through September 1985, 39.8 inches of rainfall caused above-average inflow to the Floral City Pool and a pool-level increase of 6.2 ft. The inflow of 340 CFS nearly equaled the outflow of 338 CFS by the end of September. (USGS)

  9. The impact of introduced round gobies (Neogobius melanostomus) on phosphorus cycling in central Lake Erie

    USGS Publications Warehouse

    Bunnell, D.B.; Johnson, T.B.; Knight, C.T.

    2005-01-01

    We used an individual-based bioenergetic model to simulate the phosphorus flux of the round goby (Neogobius melanostomus) population in central Lake Erie during 1995-2002. Estimates of round goby diet composition, growth rates, and population abundance were derived from field sampling. As an abundant introduced fish, we predicted that round gobies would influence phosphorus cycling both directly, through excretion, and indirectly, through consumption of dreissenid mussels, whose high mass-specific phosphorus excretion enhances recycling. In 1999, when age-1+ round gobies reached peak abundance near 350 million (2.4 kg??ha-1), annual phosphorus excretion was estimated at 7 t (1.4 ?? 10-3 mg P??m-2??day -1). From an ecosystem perspective, however, round gobies excreted only 0.4% of the phosphorus needed by the benthic community for primary production. Indirectly, round gobies consumed <0.2% of dreissenid population biomass, indicating that round gobies did not reduce nutrient availability by consuming dreissenids. Compared with previous studies that have revealed introduced species to influence phosphorus cycling, round gobies likely did not attain a sufficiently high biomass density to influence phosphorus cycling in Lake Erie. ?? 2005 NRC Canada.

  10. An 8,000 year oxygen isotope record of hydroclimatic change from Paradise Lake, central British Columbia

    NASA Astrophysics Data System (ADS)

    Hillman, A. L.; Abbott, M. B.; Steinman, B. A.; Pompeani, D. P.; Cwiklik, J. P.

    2013-12-01

    Climate in the Pacific Northwest over the Holocene has primarily been controlled by the position of the Aleutian Low (AL), which is interconnected to the Pacific Decadal Oscillation (PDO) and the El Nino Southern Oscillation (ENSO). Stable isotopes of authigenic calcite precipitated from lake water and archived as lake sediment can be used to reconstruct changes in precipitation/evaporation (P/E) balance over timescales ranging from individual years to millennia. Several records of this type from southern British Columbia and northern Washington (e.g., Castor and Cleland Lakes), as well as from the southern Yukon Territory (e.g., Marcella and Rantin Lakes) have been produced, but few records from between these two regions exist. Here, we present a record of δ18O and δ13C measurements of authigenic calcite from Paradise Lake, British Columbia (54.68259°N, 122.61154°W), a surficially closed basin, groundwater throughflow lake located in the central interior of British Columbia. A total of 14 AMS radiocarbon dates were used to provide age control for the Paradise Lake record. In sediment from 8,000-4,500 years BP, oxygen isotope values vary around a mean value of -18.0‰. From 4,500-2,000 years BP, a general trend towards more positive oxygen isotope values occurs, with increased variability in both δ18O and δ13C. A gradual shift of ~2‰ in δ18O measurements (to a mean value of -16.0‰) occurs over the last 2,000 years of the record, likely due to lower lake levels. The large magnitude mean state shifts in oxygen isotopes over the last 8,000 years are similar to that observed in the Marcella Lake record (Anderson et al., 2007), although they are of a smaller magnitude. We hypothesize that significant groundwater throughflow at Paradise Lake likely causes a muted hydrologic and isotopic response to climate forcing relative to Marcella Lake, which has more isotopically enriched water and loses a greater proportion of water via evaporation. The Paradise lake

  11. Relating actual with subfossil chironomid assemblages. Holocene habitat changes and paleoenvironmental reconstruction of Basa de la Mora Lake (Central Pyrenees)

    NASA Astrophysics Data System (ADS)

    Tarrats, Pol; Rieradevall, Maria; González-Sampériz, Penélope; Pérez-Sanz, Ana; Valero-Garcés, Blas; Moreno, Ana

    2014-05-01

    Analyses of subfossil and actual macroinvertebrate fauna and Chironomidae larvae (Insecta: Diptera) assemblages of Basa de la Mora Lake (Central Pyrenees, Spain, 1914 m a.s.l.) improves the environmental calibration for lake paleoreconstruction and allow to infer lake habitat changes throughout the Holocene. The results of the actual Chironomidae community are consistent with other mountain lake studies (either in the Pyrenees or other regions), with a few mismatching due to lake specific conditions. The actual and the subfossil Chironomidae taxa present in Basa de la Mora Lake are the same, which is an essential requirement to apply the analogue methods. Although we could not find habitat-specific taxa, significant differences between the different habitats present in the lake were found. This circumstance allowed applying the Modern Analogue Technique (MAT) to infer lake habitat changes. The MAT method relates the actual community, defined from the species abundance matrix and an environmental variable (which is the object of the inference), and the past community, defined from the species abundance matrix downcore. Because the first axis of DCA carried out for the study of the actual Chironomidae larvae explained the assemblage changes between the different habitats, the scores of this first axis were used as representative of the environmental variable (dominant habitat type) to be inferred. The application of the MAT has allowed identifying two periods of lake productivity increase through the Holocene: i) around 2800 cal. yrs BP, which coincides with the first documented human occupation of the area, and ii) the last four centuries, synchronous to the maximum population of mountain areas in the Pyrenees and development of stockbreeding activities.

  12. The Early Proterozoic structural and tectonic history of the south central Lake Superior Region

    NASA Astrophysics Data System (ADS)

    Ueng, Wen-Long C.; Larue, Dave K.

    1988-06-01

    The early Proterozoic tectonic evolution of the south central Lake Superior region is complex, owing to the presence of four tectonostratigraphic terranes, which were affected by six phases of deformation. The four terranes are the passive margin of the Superior craton, two paraautochthonous passive margin terranes (Crystal Falls and Florence-Niagara terranes), and a southern magmatic arc complex which is probably allochthonous with respect to the other terranes. Four of the six deformational episodes accompanied subhorizontal shortening, while two were caused by subvertical shortening. The first and the most penetrative phase of deformation is marked by subhorizontal shortening in a NNE-SSW direction. The second and fourth deformations were characterized by subvertical shortening and did not significantly modify the structural orientations from previous events in the study area. The third, fifth, and sixth deformations mostly caused open folding, and shortening directions were NW, NE, and W, respectively. Because all the terranes in the south central Lake Superior region share parallel deformational histories, it is suggested that the accretion of these terranes occurred during the first deformational episode. After removal of younger deformational effects, including open folding of the suture zone, the tectonostratigraphic assemblages in this region show the following sequence from NNE to SSW: a platformal assemblage overlying sialic basement, a basinal assemblage of tholeiitic volcanic rocks overlain by deep-water turbidites, an assemblage of basin floor deposits (Crystal Falls terrane) with apparently no demonstratably underlying crystalline basement, a fault-bounded terrane with highly strained passive margin strata (Florence-Niagara terrane), and a calc-alkaline magmatic arc assemblage. Such an arrangement of tectonostratigraphic assemblages is comparable with cross sections through Phanerozoic accretionary continental margins and therefore supports an arc

  13. Mineralogy, geochemistry and genesis of the modern sediments of Seyfe Lake, Kırşehir, central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Önalgil, Nergis; Kadir, Selahattin; Külah, Tacit; Eren, Muhsin; Gürel, Ali

    2015-02-01

    Seyfe Lake (Kırşehir, Turkey) is located within a depression zone extending along a NW-SE-trending fault in central Anatolia. Evaporite and carbonate sediments occur at the bottom of the lake which is fed by high-sulfate spring and well waters circulating N-S through salt domes. The recent sediments of Seyfe Lake are deposited in delta, backshore, beach, mud-flat and shallow lake environments. In the mud-flat environment, calcite, gypsum, halite, and thenardite are associated with fine-grained detrital sediments. Sediments from the margin to the lake center are distributed as calcite, gypsum and halite ± thenardite, yielding an annular distribution pattern. An increase in Na2O, SO3, and S, and a decrease in CaO toward the lake center are due to sediment distribution. On the other hand, a positive correlation of SiO2 with MgO, K2O, Na2O, Al2O3, and Fe2O3 + TiO2 is attributed to the presence of smectite, illite and feldspar. In addition, a positive correlation of Sr and Ba with CaO is related to the amount of gypsum in the sediments. Strontium is associated with in situ gypsum crystals; it increases in the intermediate and central zones of the lake as a result of a relative increase in salinity toward the lake center. The association of Sr with gypsum in the sediments suggests that Ca and Sr were derived from Sr-bearing evaporites and their carbonate host rocks, which were the likely aquifers for the brine. The S- and O-isotopic compositions of sulfate crystals range from +19.1‰ to +21.7‰ and from +16.9‰ to +20.9‰ SMOW, respectively, suggesting precipitation in a closed lake system. A relative increase of oxygen and sulfur isotope ratios toward the lake center suggests dissolution of gypsum in the host rock, with contributions from circulating groundwater and sulfate reduction (possibly by bacterial reduction). 87Sr/86Sr isotope ratios range from 0.707286 to 0.707879, suggesting a non-marine Oligo-Pliocene evaporitic host rock source for precipitation in

  14. Effects of climatic warming on Lakes of the central boreal forest

    SciTech Connect

    Schindler, D.W.; Beaty, K.G.; Fee, E.J.; Cruikshank, D.R.; DeBruyn, E.R.; Findlay, D.L.; Linsey, G.A.; Shearer, J.A.; Stainton, M.P.; Turner, M.A. )

    1990-11-16

    Twenty years of climatic, hydrologic, and ecological records for the Experimental Lakes Area of northwestern Ontario show that air and lake temperatures have increased by 2{degree}C and the length of the ice-free season has increased by 3 weeks. Higher than normal evaporation and lower than average precipitation have decreased rates of water renewal in lakes. Concentrations of most chemicals have increased in both lakes and streams because of decreased water renewal and forest fires in the catchments. In Lake 239, populations and diversity of phytoplankton also increased, but primary production showed no consistent trend. Increased wind velocities, increased transparency, and increased exposure to wind of lakes in burned catchments caused thermoclines to deepen. As a result, summer habitats for cold stenothermic organisms like lake trout and opossum shrimp decreased. Our observations may provide a preview of the effects of increased greenhouse warming on boreal lakes. 27 refs., 1 fig.

  15. Seasonal and spatial contrasts of sedimentary organic carbon in floodplain lakes of the central Amazon basin.

    NASA Astrophysics Data System (ADS)

    Sobrinho, Rodrigo; Kim, Jung-Hyun; Abril, Gwenaël; Zell, Claudia; Moreira-Turcq, Patricia; Mortillaro, Jean-Michel; Meziane, Tarik; Damsté, Jaap; Bernardes, Marcelo

    2014-05-01

    Three-quarters of the area of flooded land in the world are temporary wetlands (Downing, 2009), which play a significant role in the global carbon cycle(Einsele et al., 2001; Cole et al., 2007; Battin et al., 2009; Abril et al., 2013). Previous studies of the Amazonian floodplain lakes (várzeas), one important compartment of wetlands, showed that the sedimentation of organic carbon (OC) in the floodplain lakes is strongly linked to the periodical floods and to the biogeography from upstream to downstream(Victoria et al., 1992; Martinelli et al., 2003). However, the main sources of sedimentary OC remain uncertain. Hence, the study of the sources of OC buried in floodplain lake sediments can enhance our understanding of the carbon balance of the Amazon ecosystems. In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Miratuba, and Curuai) which have different morphologies, hydrodynamics and vegetation coverage. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as C:N ratio and stable isotopic composition of organic carbon (δ13COC). These results were compared with lignin-phenol parameters as an indicator of vascular plant detritus (Hedges and Ertel, 1982) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the soil OC from land to the aquatic settings (Hopmans et al., 2004). Our data showed that during the RW and FW seasons, the concentration of lignin and brGDGTs were higher in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of a mixture of C3 plant detritus and soil OC. However, a downstream increase in C4 plant-derived OC contribution was observed along the gradient of increasingly open waters, i

  16. Characterization of lake water and ground water movement in the littoral zone of Williams Lake, a closed-basin lake in North central Minnesota

    USGS Publications Warehouse

    Schuster, P.F.; Reddy, M.M.; LaBaugh, J.W.; Parkhurst, R.S.; Rosenberry, D.O.; Winter, T.C.; Antweiler, R.C.; Dean, W.E.

    2003-01-01

    Williams Lake, Minnesota is a closed-basin lake that is a flow-through system with respect to ground water. Ground-water input represents half of the annual water input and most of the chemical input to the lake. Chemical budgets indicate that the lake is a sink for calcium, yet surficial sediments contain little calcium carbonate. Sediment pore-water samplers (peepers) were used to characterize solute fluxes at the lake-water-ground-water interface in the littoral zone and resolve the apparent disparity between the chemical budget and sediment data. Pore-water depth profiles of the stable isotopes ??18O and ??2H were non-linear where ground water seeped into the lake, with a sharp transition from lake-water values to ground-water values in the top 10 cm of sediment. These data indicate that advective inflow to the lake is the primary mechanism for solute flux from ground water. Linear interstitial velocities determined from ??2H profiles (316 to 528 cm/yr) were consistent with velocities determined independently from water budget data and sediment porosity (366 cm/yr). Stable isotope profiles were generally linear where water flowed out of the lake into ground water. However, calcium profiles were not linear in the same area and varied in response to input of calcium carbonate from the littoral zone and subsequent dissolution. The comparison of pore-water calcium profiles to pore-water stable isotope profiles indicate calcium is not conservative. Based on the previous understanding that 40-50 % of the calcium in Williams Lake is retained, the pore-water profiles indicate aquatic plants in the littoral zone are recycling the retained portion of calcium. The difference between the pore-water depth profiles of calcium and ??18O and ??2H demonstrate the importance of using stable isotopes to evaluate flow direction and source through the lake-water-ground-water interface and evaluate mechanisms controlling the chemical balance of lakes. Published in 2003 by John Wiley

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

    PubMed

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

    2009-10-15

    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.

  18. Evolution of the banks of thermokarst lakes in Central Yakutia (Central Siberia) due to retrogressive thaw slump activity controlled by insolation

    NASA Astrophysics Data System (ADS)

    Séjourné, A.; Costard, F.; Fedorov, A.; Gargani, J.; Skorve, J.; Massé, M.; Mège, D.

    2015-07-01

    As observed in most regions in the Arctic, the thawing of ice-rich permafrost (thermokarst) has been developing in Central Yakutia. However, the relationship between thermokarst development and climate variations is not well understood in this region, in particular the development rate of thaw slumps. The objective of this paper is to understand the current development of thermokarst by studying the evolution of the banks of thermokarst lakes. We studied retrogressive thaw slumps and highly degraded ice-wedge polygons (baydjarakhs), indicative of thermokarst, using high resolution satellite images taken in 2011-2013 and conducting field studies. The retrogressive thaw slump activity results in the formation of thermocirque with a minimum and maximum average headwall retreat of 0.5 and 3.16 m·yr- 1 respectively. The thermocirques and the baydjarakhs are statistically more concentrated on the south- to southwest-facing banks of thermokarst lakes. Moreover, the rate of headwall retreat of the thermocirques is the most important on the south-facing banks of the lakes. These observations indicate a control of the current permafrost thaw on the banks of thermokarst lakes by insolation. In the context of recent air temperature increase in Central Yakutia, the rate of thermocirque development may increase in the future.

  19. Establishing the geometry and nature of sediments trapped in either natural or artificial dam lakes in contrasted drainage basins from Western Europe (French Massif Central and Pyrenees)

    NASA Astrophysics Data System (ADS)

    Chapron, Emmanuel; Chassiot, Léo; Zouzou, Claude; Simonneau, Anaelle; Galop, Didier; Di Giovanni, Christian

    2016-04-01

    Lacustrine sedimentary archives from artificial dam lakes are poorly documented both in terms of basin fill geometries and dominating sedimentary processes. In order to better understand their sensitivities to regional environmental changes, we performed a similar multidisciplinary study of French natural and artificial dam lakes in contrasted drainage basins from the volcanic Massif Central (lakes Aydat and Crégut) and two granitic sectors of the northern Pyrenees (lakes Fourcat and Orédon). Our approach combined high-resolution sub bottom profiling (14 kHz and 4 kHz chirp) and a detailed study of sediment cores based on qualitative and quantitative analysis (radiographies, sediment physical and chemical properties) together with radionuclide and radiocarbon dates. In all cases either changes in land uses within the drainage basin or the flooding of natural lakes by dams and the production of hydroelectricity induced changes in sedimentation rates and modes. Human activities affecting either the catchment or the lake itself favored enhanced clastic sediment supply in the lake basins and/or higher and fluctuating lake levels. Subaquatic slopes failures are also identified in Lake Aydat formed by a lava flow 8.5 kYrs ago and in glacial lakes Crégut (Massif Central) and Orédon (Pyrenees) now used to produce hydroelectricity and suggest that lake level changes and ground accelerations during earthquakes can remobilize distinct sectors of the basin fills and not only deltaic environments.

  20. δ18O and δD of lake waters across the Coast Range and Cascades, central Oregon: Modern insights from hydrologically open lakes into the control of landscape on lake water composition in deep time

    NASA Astrophysics Data System (ADS)

    Finkelstein, D. B.; Curtin, T.

    2016-12-01

    Reconstructing the stable isotopic composition of paleolake water normally requires an assumption of paleotemperature. However, hydrologically open paleolakes with short water residence times may have recorded paleoprecipitation along topographic gradients that are independent of lake water temperature. To identify the environmental and geographic controls on the isotopic composition of lake water, we sampled 22 natural lakes and reservoirs along a longitudinal and elevation gradient from the Pacific Ocean up and over the Coast and Cascade Ranges of central Oregon to the High Lava Plains in 2013 and 2015. The transect spans lakes of different origins, 6 geomorphic regions and an elevation range of 2-1942 m absl. The Coast Range lakes are sand hosted whereas the remaining are bedrock (volcanic and sedimentary) hosted. The lakes are hydrologically open and dominated by meteoric recharge. The water residence time ranges from months to decades. Samples were analyzed for temperature, pH, and total dissolved solids (TDS) in the field, and alkalinity and major cations and anions and stable isotopes of D and O in the lab. The pH ranges from 7 to 9.8 and shows no systematic variation based on substrate type or elevation. The lakes are dilute (avg. TDS = 35.8 ppm) and have low alkalinties (18.9 mg/L CaCO3) except for those in the High Lava Plains (avg. TDS = 337 ppm, alk: 291.2 mg/L CaCO3). In the Coast Range, Na is the major cation on an equivalent basis, reflecting proximity to the ocean. The easternmost lakes within the Coast Range are dominated by Ca, reflecting different drainage basins and substrate type. Lakes in the Western and High Cascades are dominated by Ca. The dominant cation and stable isotopic analyses clearly differentiate waters from different geomorphic regions. The δ18O ranges from -5.7 to -9.3 ‰ (VSMOW), and δD ranges from -37.8 to -63.6 ‰ (VSMOW) in the Coast Range whereas the δ18O ranges from -9.7 to -12.1 ‰ (VSMOW) and δD ranges from -71

  1. Hydrology and water quality of Park Lake, south-central Wisconsin

    USGS Publications Warehouse

    Kammerer, P.A.

    1996-01-01

    Park Lake extends to the northeast from the village of Pardeeville in Columbia County (fig. 1). Local residents perceive water-quality problems in the lake that include excessive algae and aquatic plant growth. Algae and plant growth in a lake are controlled, in part, by the availability of phosphorus in the water. However, no measurements of phosphorus enter- ing the lake or of other factors that affect lake-water quality had been made, and available data on water quality were limited to 2 years of measurements at one site in the lake in 1986- 87. To obtain the data and in- formation needed to address the water-quality problems at Park Lake and to develop a management plan that would limit the input of phosphorus to the lake, the U.S. Geologi- cal Survey, in cooperation with the Park Lake Management District, studied the hydrology of the lake and collected data needed to determine sources and amount of phosphorus en- tering the lake. This Fact Sheet summarizes the results of that study. Data collected during the study were published in a separate report (Holmstrom and others, 1994, p. 70-85).

  2. Deglaciation of the Central Lake Superior Basin Imaged by High-Resolution Seismic-Reflection Profiles

    NASA Astrophysics Data System (ADS)

    Colman, S. M.; Breckenridge, A. J.; Wattrus, N. J.

    2015-12-01

    The Lake Superior basin experienced multiple episodes of glaciation, resulting in a variety of glacial deposits and landforms, most of which date to the final retreat of Laurentide ice from the basin. Prominent among these features are moraines and thick glacial lacustrine varve sequences in the central part of the lake. Because these features are now beneath deep water, they can be well imaged by modern marine seismic-reflection methods, providing a variety of insights into glacial processes and history. Two prominent moraines occur east of Isle Royale, and other morainal deposits exist. The prominent moraines are as much as 75 m high, asymmetric, and locally concave down-ice in plan view. They are steeper up-ice than down, but vary in morphology along strike. Air-gun seismic-reflection data show that the moraines are underlain by thick, acoustically massive deposits (till) over a smooth bedrock surface, and that, in front of the moraines, the till grades laterally into increasingly stratified deposits interpreted as glacial lacustrine outwash. Such lateral relations between till and outwash are rarely displayed so well in natural exposures. The moraines relate to the Marquette advance of the Laurentide ice sheet, but they are difficult to directly correlate with the terrestrial deposits used to define that advance. Overlying the till and moraines is a thick sequence of glacial lacustrine varves, which are well imaged by high-resolution CHIRP seismic-reflection profiles. Although the CHIRP data cannot resolve even the thickest of the individual varves, the section comprises distinct acoustic packages. The CHIRP data show that the base of the varve sequence becomes younger to the northeast, the direction of ice retreat. Throughout the varved sequence are lenses of acoustically massive material and local features interpreted as iceberg plow marks, which are especially concentrated at one horizon. Limited 3-D seismic data show the curvilinear plan view of the plough

  3. Effect of phosphorous concentrations on sedimentary distributions and isotopic composition of algal lipid biomarkers in lakes from central Switzerland

    NASA Astrophysics Data System (ADS)

    Ladd, N.; Dubois, N.; Schubert, C. J.

    2015-12-01

    Lakes in the Swiss central plateau experienced increasing anthropogenic phosphorous loading throughout much of the 20th century. Since the 1980s concerted remediation efforts on the part of the Swiss government have significantly reduced P concentrations in most lakes and reversed previous eutrophication. However, P concentrations remain elevated above their preindustrial levels in many sites. High quality monitoring of lake nutrient levels since the 1950s, along with several lakes of wide-ranging P concentrations in close proximity, make central Switzerland an ideal location for studying the ways in which nutrient loading affects the organic composition of lacustrine sediments. Results of such studies can be used to develop proxies of eutrophication in sites where fewer historical data exist, and to reconstruct historical P concentrations in local lakes from the time before record keeping began. We analyzed the distributions of algal lipid biomarkers from surface sediment and sediment traps collected in the spring of 2015 from ten lakes with variable P concentrations in central Switzerland. Sedimentary lipid distributions from these lakes confirm that biomarkers associated with algal and cyanobacterial sources are more abundant in the sediment of lakes with greater P loading. The dry sedimentary concentrations of biomarkers such as brassicasterol (primarily diatom source) and diplopterol (cyanobacteria source), as well as the less source specific short-chain n-alkanols, linearly increase from 0.3 - 1.9 μg/g as total phosphorous in the upper water column increases by 1 μg/L over a range of 7 - 50 μg/L. We also present preliminary hydrogen isotope data from these biomarkers. Hydrogen isotopes of algal lipids primarily reflect the source water in which the algae grew, and this relationship has been developed as a paleohydrologic proxy. However, laboratory cultures of marine algae demonstrate that they discriminate more against 2H under nutrient replete conditions

  4. Organic carbon contents and isotopic compositions in the Lake Cuitzeo sediments from the central Mexico during the past 45 Ka: Changes in lake level and climate

    NASA Astrophysics Data System (ADS)

    Kuo, T.; Bischoff, J. L.; Alcantara, I. I.; Garduño-Monroy, V. H.; Li, H.

    2009-12-01

    A 27-m long core was retrieved from Lake Cuitzeo in south-central Mexico (19°56’N, 101°5’W). A total of 163 sediment samples have been treated by 0.5N HCl to remove carbonates, then washed and frozen dried. The samples were analyzed for total organic carbon (TOC) and δ13Corg by EA-IRMS. High TOC contents present in the intervals of 0.6~1.6, 2.3~3.6, 6.7~6.8 and 8.5~9.5m while the δ13Corg of these intervals are generally heavier (ranging from -22‰ ~ -13‰). The TOC contents in other depths are generally lower than 1 wt.% with relatively light δ13Corg values ranging from -26‰ ~ -20‰. Since the chronology of the upper 9.2m of the core is more reliable, we are able to interpret the lake history and the corresponding climatic and vegetation variations during the past 45 Ka, based on the TOC, CaCO3% (reflected by weight loss of acid-leaching) and δ13Corg. There are four scenarios in the record: (1) During the periods of 2~8, 33~34 and 43~45Ka, TOC and CaCO3% covary at moderate levels with heavy δ13Corg values (>-20‰). The lake was closed and had high productivity under high saline and alkaline conditions. (2) High CaCO3%, low TOC and δ13Corg values during the periods of 8~12, 20~24, 28~31 and 35~38Ka, indicate that the lake dropped in level and became close. (3) High TOC but very low CaCO3% with gradually enriched δ13Corg value during the period of 14~20Ka reflect a fresh, cold and deep lake. However, the high TOC content might be caused by terrestrial input around the lake. (4) All other periods had low CaCO3%, TOC and δ13Corg values (-21‰ ~ -24‰), showing a deep and fresh lake under cold and wet climates.

  5. Analysis of lake level changes in Nam Co in central Tibet utilizing synergistic satellite altimetry and optical imagery

    NASA Astrophysics Data System (ADS)

    Kropáček, Jan; Braun, Andreas; Kang, Shichang; Feng, Chen; Ye, Qinghua; Hochschild, Volker

    2012-07-01

    The fluctuations of closed basin lakes on the Tibetan Plateau are a valuable record of climate change induced water balance alterations within the catchments. Since these basins are remote and hard to access, multisensoral remote sensing is a valuable method to gather the necessary water budget components with appropriate spatial coverage and with high temporal resolutions. Thus the lake level elevation changes of the central Tibetan lake Nam Co were examined in example by a comparison of satellite altimetry (RA-2/ENVISAT, GFO radar altimeters and GLAS/ICESat laser altimeter for the period 2000-2009) and the evaluation of a time series of optical satellite data dating back to 1976 (Landsat) and 1965 (Corona) in order to validate hydrological water budget modelling results. The combination of all three altimeters revealed a rising trend of lake level on average by 0.31 m/year in the period 2000-2009 which corresponds to a total volume change of 6.2 km3. This is in a good agreement with simulated average lake level rise of 0.35 m/year obtained from distributed hydrological modelling (Krause et al., 2010). The movements of lakeshore measured on the satellite imagery confirm the trend revealed by the altimetry data and they also indicate the rising trend since 1965. While GFO provides a dense time series of data the more accurate ENVISAT/RA-2 data unfortunately feature large data gaps over Tibet. The measurements from time limited campaigns of ICESat validate the results of radar altimetry and they provide unlike radar altimeters a valid height over lake ice during winter and spring period. The results show that the presented approach is a valuable contribution to understand the impact of changing climate on the hydrology of Tibetan lakes.

  6. The hydrological and environmental evolution of shallow Lake Melincué, central Argentinean Pampas, during the last millennium

    NASA Astrophysics Data System (ADS)

    Guerra, Lucía; Piovano, Eduardo L.; Córdoba, Francisco E.; Sylvestre, Florence; Damatto, Sandra

    2015-10-01

    Lake Melincué, located in the central Pampean Plains of Argentina, is a shallow (∼4 m), subsaline lake (TDS > 2000 ppm), highly sensitive to hydrological changes. The modern shallow lake system is composed of: (a) a supralittoral area, which includes a narrow mudflat, a vegetated mudflat and wetlands subenvironments; and (b) the main water body, comprising lacustrine marginal and inner areas. The development and extension of these subenvironments are strongly conditioned upon lake surface fluctuations. Past environmental changes were reconstructed through sedimentological, physical and geochemical proxy analyses of two short sedimentary cores (∼127 cm). Well-constrained 210Pb ages profiles were modeled and radiocarbon chronologies were determined, covering a period from ∼AD 800 to the present. The analyzed sedimentary cores from Lake Melincué allowed for the reconstruction of past hydrological scenarios and associated environmental variability, ranging from extremely low lake levels during dry phases to pronounced highstands at wet periods. The paleohydrological reconstruction revealed very shallow conditions in the period between AD 806 and AD 1880, which was registered by massive deposits with low organic matter. Relatively wetter phases disrupting this dry period were represented by organic matter increases. A major wet phase was registered by AD 1454, after the end of the Medieval Climate Anomaly. A subsequent abrupt shift from this wet phase to drier conditions could be matching the transition between the end of the Medieval Climatic Anomaly and the beginning of the Little Ice Age. The occurrence of sedimentary hiatuses between AD 1492 and AD 1880 in Melincué sequence could correspond to intensive droughts during the Little Ice Age. After AD 1880, banded and laminated, autochthonous, organic matter-rich sediments registered an important lacustrine transgression and the onset of a permanent shallow lake, corresponding to the beginning of the current

  7. Fate of Metals in Relation to Water and Sediment Properties in a Subtropical Lake in Central Himalaya, India.

    PubMed

    Inaotombi, Shaikhom; Gupta, Prem Kumar

    2017-04-01

    Lakes of Himalaya are one of the most fragile ecosystems on earth. Tourism and urban development in the upland region strongly affect its water resources. The high rate of sedimentation and organic matter deposition alters the ecological state of sediment bed, which indirectly influences on dynamics of metallic elements. We investigated spatial and temporal variations of water and sediment characteristic in Lake Sattal of Central Himalaya, India. Samples were collected seasonally from four sampling locations from January 2011 to December 2012. Pearson's correlation and Canonical correspondence analysis (CCAs) were applied to examine the dynamics and behaviors of heavy metals. Concentrations of elements were in the order of fluoride (Fl) > zinc (Zn) > copper (Cu) > iron (Fe) > manganese (Mn). Sand size fraction was higher in the littoral zone while clay particle was dominant in the profundal zone of the lake. Dissolved oxygen at sediment-water-interface (SWI) and water temperature were the major factors influencing the dynamics of metallic contents in the water column. Spatially, total organic matter (TOM) was higher in the deeper portion of the lake. Our study revealed that mobility of Fe is temperature-dependent, whereas speciation of Mn and Cu are primarily controlled by the suboxic condition of SWI in organic-rich site. Upland lakes are more vulnerable to anoxic condition and have severe implications on heavy metals speciation. Proper implementation of land use policies and management practices, including stormwater detention, can be integrated into resolving such problems.

  8. The Cinder Lake Intrusive Complex, Knee Lake area, Central Manitoba: a Syenite- Carbonatite Association from a Neoarchean Continental Margin

    NASA Astrophysics Data System (ADS)

    Chakhmouradian, A. R.; Böhm, C. O.; Kressall, R. D.; Lenton, P. G.

    2009-05-01

    The Cinder Lake intrusive complex is the only known occurrence of feldspathoid rocks in Manitoba. These rocks were initially mapped in the southeastern part of the Lake by Elbers (in Gilbert, 1985) and Lenton (1985), but have not been adequately studied. On the basis of new field, petrographic and geochemical evidence acquired in 2008, three discrete intrusive phases can be presently identified at Cinder Lake: fine-grained aegirine-nepheline syenite, fine-grained biotite-vishnevite syenite and syenitic pegmatite. There is also convincing mineralogical and geochemical evidence for the presence of unexposed clinopyroxenite and carbonatitic units genetically associated with the alkaline syenitic rocks. The evidence for the presence of unexposed carbonatite includes pervasive calcitization of the syenitic rocks, occurrence of rare-earth minerals (britholite, monazite and REE-rich apatite) in association with Sr-rich calcite in metasomatised pegmatite, and andradite veins crosscutting the syenites. The geochemistry of the Cinder Lake rocks is most consistent with the HFSE-depleted, potassic, high-Ba/La and high-Th/Nb signature of arc magmas (Edwards et al., 1994). In common with island-arc and continental-margin phonolites, the Cinder Lake syenites are potassic rocks with a chondritic Zr/Hf ratio, strong enrichment in Ba relative to La and Th relative to Nb. Uranium-lead dating of zircon crystals recovered from the biotite-vishnevite syenite yielded an age of 2705±2 Ma, interpreted as the timing of syenite emplacement. This value is close to the age of the incipient accretion of subprovinces in the northwestern Superior province at 2.70-2.71 Ga (Davis et al. 2005). Given this age relationship, the Cinder Lake complex is probably derived from magmas produced in a Neoarchean subduction zone underlying the North Caribou microcontinent. The regional geological setting of the complex (abundance of tonalite and granodiorite among the plutonic rocks and the predominance of

  9. Hydrogeochemical investigations in a drained lake area: the case of Xynias basin (Central Greece).

    PubMed

    Charizopoulos, Nikos; Zagana, Eleni; Stamatis, Georgios

    2016-08-01

    In Xynias drained Lake Basin's area, central Greece, a hydrogeochemical research took place including groundwater sampling from 30 sampling sites, chemical analysis, and statistical analysis. Groundwaters present Ca-Mg-HCO3 as the dominant hydrochemical type, while their majority is mixed waters with non-dominant ion. They are classified as moderately hard to hard and are characterized by oxidizing conditions. They are undersaturated with respect to gypsum, anhydrite, fluorite, siderite, and magnesite and oversaturated in respect to calcite, aragonite, and dolomite. Nitrate concentration ranges from 4.4 to 107.4 mg/L, meanwhile 13.3 % of the samples exceed the European Community (E.C.) drinking water permissible limit. The trace elements Fe, Ni, Cr, and Cd present values of 30, 80, 57, and 50 %, respectively, above the maximum permissible limit set by E.C. Accordingly, the majority of the groundwaters are considered unsuitable for drinking water needs. Sodium adsorption ratio values (0.04-3.98) and the electrical conductivity (227-1200 μS/cm) classify groundwaters as suitable for irrigation uses, presenting low risk and medium soil alkalization risk. Factor analysis shows that geogenic processes associated with the former lacustrine environment and anthropogenic influences with the use of fertilizers are the major factors that characterized the chemical composition of the groundwaters.

  10. Molecular Tracers of Saturated and Polycyclic Aromatic Hydrocarbon Inputs into Central Park Lake, New York City

    PubMed Central

    YAN, BEIZHAN; ABRAJANO, TEOFILO A.; BOPP, RICHARD F.; CHAKY, DAMON A.; BENEDICT, LUCILLE A.; CHILLRUD, STEVEN N.

    2011-01-01

    Saturated hydrocarbons (SH) and polycyclic aromatic hydrocarbons (PAHs) have been quantified in a sediment core obtained from Central Park Lake, New York City. Radionuclides 210Pb and 137Cs were used to assign approximate dates to each individual section in the core. The dating profile based on 210Pb matches very well with the time constraints provided by 137Cs. Radionuclide-derived depositional dates are consistent with temporal information from the petroleum-indicator ratio U/R [the ratio of unresolved complex mixture (UCM) to saturated hydrocarbons in the aliphatic fraction] and the history of fuel use in the NYC area. Ratios of 1,7-dimethylphenanthrane (DMP) to 1,7-DMP plus 2,6-DMP [1,7/(1,7 + 2,6)-DMP], retene to retene plus chrysene [Ret/(Ret + Chy)], and fluoranthene to fluoranthene plus pyrene [Fl/(Fl + Py)] provide additional source discrimination throughout the core. Results show that the ratio U/R is sensitive to petroleum inputs and Ret/(Ret + Chy) is responsive to contributions from softwood combustion, whereas both Fl/(Fl + Py) and 1,7/(1,7 + 2,6)-DMP can be used to discriminate among wood, coal, and petroleum combustion sources. Combined use of these ratios suggests that in New York City, wood combustion dominated 100 years ago, with a shift to coal combustion occurring from the 1900s to the 1950s. Petroleum use began around the 1920s and has dominated since the 1940s. PMID:16201624

  11. Molecular and isotopic characteristics of gas hydrate-bound hydrocarbons in southern and central Lake Baikal

    NASA Astrophysics Data System (ADS)

    Hachikubo, Akihiro; Khlystov, Oleg; Krylov, Alexey; Sakagami, Hirotoshi; Minami, Hirotsugu; Nunokawa, Yutaka; Yamashita, Satoshi; Takahashi, Nobuo; Shoji, Hitoshi; Nishio, Shin'ya; Kida, Masato; Ebinuma, Takao; Kalmychkov, Gennadiy; Poort, Jeffrey

    2010-06-01

    We investigated the molecular composition (methane, ethane, and propane) and stable isotope composition (methane and ethane) of hydrate-bound gas in sediments of Lake Baikal. Hydrate-bearing sediment cores were retrieved from eight gas seep sites, located in the southern and central Baikal basins. Empirical classification of the methane stable isotopes (δ13C and δD) for all the seep sites indicated the dominant microbial origin of methane via methyl-type fermentation; however, a mixture of thermogenic and microbial gases resulted in relatively high methane δ13C signatures at two sites where ethane δ13C indicated a typical thermogenic origin. At one of the sites in the southern Baikal basin, we found gas hydrates of enclathrated microbial ethane in which 13C and deuterium were both highly depleted (mean δ13C and δD of -61.6‰ V-PDB and -285.4‰ V-SMOW, respectively). To the best of our knowledge, this is the first report of C2 δ13C-δD classification for hydrate-bound gas in either freshwater or marine environments.

  12. Avian use of Sheyenne Lake and associated habitats in central North Dakota

    USGS Publications Warehouse

    Faanes, Craig A.

    1982-01-01

    A study of avian use of various habitats was conducted in the Sheyenne Lake region of central North Dakota during April-June 1980. Population counts of birds were made in wetlands of various classes, prairie thickets, upland native prairie, shelterbelts, and cropland. About 22,000 breeding bird pairs including 92 species that nested occupied the area. Population means for most species were equal to or greater than statewide means. Red-winged blackbird (Agelaius phoeniceus), yellow-headed blackbird (Xanthocephalus xanthocephalus), mourning dove (Zenaida macroura), and blue-winged teal (Anas discors) were the most numerous species, and made up 32.9% of the total population . Highest densities of breeding birds occurred in shelterbelts, semipermanent wetlands, and prairie thickets. Lowest densities occurred in upland native prairie and cropland. The study area was used by 49.6% of the total avifauna of the State, and 51% of the breeding avifauna of North Dakota probably nested in the study area. The diversity of birds using the area was unusual in that such a large number of species occupied a relatively small area. The close interspersion of many native habitats, several of which are unique in North Dakota, probably accounted for this diversity. Data on dates of occurrence, nesting records, and habitat use are presented for the 175 species recorded in 1980. Observations of significance by refuge staff are also provided.

  13. Greenhouse gas fluxes of a shallow lake in south-central North Dakota, USA

    USGS Publications Warehouse

    Tangen, Brian; Finocchiaro, Raymond; Gleason, Robert A.; Dahl, Charles F.

    2016-01-01

    Greenhouse gas (GHG) fluxes of aquatic ecosystems in the northern Great Plains of the U.S. represent a significant data gap. Consequently, a 3-year study was conducted in south-central North Dakota, USA, to provide an initial estimate of GHG fluxes from a large, shallow lake. Mean GHG fluxes were 0.02 g carbon dioxide (CO2) m−2 h−1, 0.0009 g methane (CH4) m−2 h−1, and 0.0005 mg nitrous oxide (N2O) m−2 h−1. Fluxes of CO2 and CH4 displayed temporal and spatial variability which is characteristic of aquatic ecosystems, while fluxes of N2O were consistently low throughout the study. Comparisons between results of this study and published values suggest that mean daily fluxes of CO2, CH4, and N2O fromLong Lakewere low, particularly when compared to the well-studied prairie pothole wetlands of the region. Similarly, cumulative seasonal CH4 fluxes, which ranged from 2.68–7.58 g CH4 m−2, were relatively low compared to other wetland systems of North America. The observed variability among aquatic ecosystems underscores the need for further research.

  14. A Survey and Analysis of Reading Habits and Library Use Patterns of the Central City Residents of Salt Lake City, Utah.

    ERIC Educational Resources Information Center

    Freebairn, Mark R.; Palmer, Rita

    The purpose of this study was to survey and analyze two census tracts of Salt Lake City proper, a residential area frequently referred to as Central City. This study was commissioned by Richard J. Rademacher, Director, Salt Lake City Public Library. A questionnaire was formulated through an analysis of other surveys at the conclusion of an…

  15. Sedimentation in Whitewater Lake, Union County, east-central Indiana, 1959-88

    USGS Publications Warehouse

    Renn, D.E.

    1993-01-01

    Potential decreases in the storage capacity of Whitewater Lake based on whether dredging is continued or discontinued were estimated for the 29-year period 1989-2017. If dredging is continued, the potential for future decreases in the storage capacity of the lake is small. If dredging is discontinued, the volume of water in the lake in 2017 is estimated to be 88.2 percent of the 1959 volume; 11.8 percent of the 1959 volume of the lake would be filled with sediment.

  16. Quantifying evaporation and its decadal change for Lake Nam Co, central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Lazhu, Kun Yang; Wang, Junbo; Lei, Yanbin; Chen, Yingying; Zhu, Liping; Ding, Baohong; Qin, Jun

    2016-07-01

    Most lakes in the interior Tibetan Plateau have expanded rapidly since the late 1990s. Because of a lack of observations, lake water balances and their changes are far from well understood. Evaporation is a component of the lake water balance, and this study quantifies its magnitude, decadal change, and its contribution to the water balance changes in Lake Nam Co, one of the largest lakes on the Tibetan Plateau (with an area of approximately 2000 km2 and a mean depth of approximately 40 m). The lake temperature and the evaporation are simulated by the Flake model. The simulation results are validated against observed lake temperature profile from 2013 and Moderate Resolution Imaging Spectroradiometer lake surface temperature data from 2000 to 2014. The simulated latent heat flux and sensible heat flux are validated against Bowen ratio-derived estimates for 2013. Based on the validated simulation results, the long-term mean annual evaporation is approximately 832 ± 69 mm, and this value is much less than the potential evaporation estimated using the Penman-Monteith equation. The annual evaporation from 1980 to 2014 displays a complex decadal oscillation, mainly due to the changes in energy-related terms (air temperature and radiation). The mean lake evaporation since the late 1990s is greater than previous periods; thus, this change in evaporation has suppressed the recent expansion of Nam Co.

  17. Multiproxy and multicore evidence of late Holocene monsoon reduction on the central Tibetan Plateau from Lake Taro Co

    NASA Astrophysics Data System (ADS)

    Turner, Falko; Lu, Xinmiao; Ahlborn, Marieke; Schwarz, Anja; Zhu, Liping; Haberzettl, Torsten; Wang, Junbo; Guo, Yun; Ju, Jianting; Frenzel, Peter; Wang, Yongbo; Mäusbacher, Roland; Alivernini, Mauro; Schwalb, Antje

    2016-04-01

    In lake ecosystems, climate change usually causes responses of multiple environmental factors. A reduction in the amount of precipitation for example may result in decreasing inflow, falling water level and rising ion concentration. While some of these factors as conductivity will influence biota in the entire lake, others will impact certain habitats more strongly. A drop in lake level for instance may severely change the extent and structure of littoral biota but might have only a minor impact on the deep profundal of large lakes. Here we present geochemical (XRF-) and organismic (pollen, chironomid, diatom, Pediastrum algae, ostracod) data for the past 7.2 ka from Taro Co, a large and deep lake on the Tibetan Plateau (31°03'- 31°13' N, 83°55' - 84°20' E, 4,567 m a.s.l., maximum depth 132 m). In addition to this multiproxy approach, three cores from different settings (central basin / profundal, sublittoral and subaquatic prodelta) are analysed to infer complementary information on mid- to late Holocene limnological changes. Independent radiocarbon chronologies for the three cores are established and patterns of the geochemical records are used to evaluate age models against each other. A pollen based quantitative reconstruction indicates a shift to increasingly arid conditions from 6 to 4 ka BP. Geochemical data and changes in species composition of diatom and Pediastrum assemblages in the profundal sediment core indicate increasing conductivity during the last 4 ka, while a chironomid-derived quantitative lake level record shows a 40 m lake level drop around 4.5 ka BP. In the prodelta sediment core, a strong lithological change from delta front to prodelta sediment and decreasing percentages of lotic chironomid taxa indicate a decreasing inflow around 4.5 ka BP. This approach to use several proxies in sediment cores from distinctive settings in one lake thus enables to infer a more complete and reliable picture of limnological changes associated with late

  18. Extending the record of lacustrine phases beyond the last interglacial for Lake Eyre in central Australia using luminescence dating

    NASA Astrophysics Data System (ADS)

    Fu, Xiao; Cohen, Tim J.; Arnold, Lee J.

    2017-04-01

    We show with multiple luminescence dating techniques that the sedimentary record for Lake Eyre, Australia's largest lake, extends beyond 200 thousand years (ka) to Marine Isotope Stage (MIS) 7. Transgressive clayey sand and finely laminated clays overlying the Miocene Etadunna Formation in Lake Eyre North document the deep-lake phases of central South Australia in the past. Until now, unresolved chronology has hampered our ability to interpret these sedimentary records, which are important for understanding the timing of the wettest phase of central Australia's late Quaternary climate. In this study, we apply quartz optically stimulated luminescence (OSL) dating, thermally-transferred OSL (TT-OSL) dating and K-feldspar post infrared infrared stimulated luminescence (pIRIR) dating to lake-floor sediments near Williams Point in Madigan Gulf to provide new age constraint for the lacustrine sediments of Lake Eyre. Methodological studies on quartz and K-feldspar demonstrate that these luminescence dating procedures are suitable for the Lake Eyre lacustrine samples and produce consistent replicate ages. A Bayesian model applied to the new dating results provides a chronological model of lacustrine deposition and shows that the transgressive clayey sand were deposited 221 ± 19 ka to 201 ± 10 ka and that the deep-water sediments were laid down in early MIS 6 (191 ± 9 ka to 181 ± 9 ka). We also find evidence for a potential depositional hiatus in mid MIS 6 and the likely formation of a palaeo-playa later in MIS 6 from 158 ± 11 ka to 143 ± 15 ka. In contrast, the MIS 5 sediments are characterised by oscillating deep- and shallow-water lacustrine units deposited 130 ± 16 ka to 113 ± 20 ka. This study is the first of its kind to provide evidence for a wet desert interior in Australia beyond the last glacial cycle using comprehensive numerical dating. Our results show that past deep-lake episodes of central South Australia, which were previously thought to represent

  19. Natural attenuation processes of nitrate in a saline lake-aquifer system: Pétrola Basin (Central Spain)

    NASA Astrophysics Data System (ADS)

    Valiente, Nicolas; Menchen, Alfonso; Jirsa, Franz; Hein, Thomas; Wanek, Wolfgang; Gomez-Alday, Juan Jose

    2016-04-01

    Saline wetlands associated with intense agricultural activities in semi-arid to arid climates are among the most vulnerable environments to NO3- pollution. The endorheic Pétrola Basin (High Segura River Basin, Central Spain) was declared vulnerable to NO3- pollution by the Regional Government of Castilla-La Mancha in 1998. The hypersaline lake was classified as a heavily modified waterbody, due to the inputs of pollutants from agricultural sources and urban waste waters, the latest are discharged directly into the lake without proper treatment. Previous studies showed that the aquifer system has two main flow components: regional groundwater flow from recharge areas into the lake, and a density-driven flow from the lake to the underlying aquifer. The NO3- inputs derived from agriculture originate from nitrification of synthetic ammonium fertilizers, and afterwards, NO3- is expected to be attenuated by denitrification (up to 60%) in the saltwater-freshwater interface around the lake. However, the spatial and temporal pattern of nitrate reduction in lake sediments is not known. In this study, an isotope pairing technique was used in order to clarify the main pathways for the NO3- attenuation linked to the sediment-water interface. For that purpose mesocosm experiments were performed: organic-rich lake sediment (up to 23% organic carbon content) was incubated for 96 hours with the addition of 15N nitrate tracer. During the experiments two factors were modified: light and oxic conditions. Analyzing inorganic N-species (n=20) over time (72 hours) showed that NO3- attenuation was coupled with an increment in the NH4+ concentration (from 0.8 mg/L up to 5.3 mg/L) and a decrease in redox values (from 135.1 mV up to -422 mV) in the water column. The main outcome of this study was to elucidate the importance of different microbial pathways denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and anaerobic ammonium oxidation (Anammox), in controlling the fate

  20. Indications of human activity from amino acid and amino sugar analyses on Holocene sediments from lake Lonar, central India

    NASA Astrophysics Data System (ADS)

    Menzel, P.; Gaye, B.; Wiesner, M.; Prasad, S.; Basavaiah, N.; Stebich, M.; Anoop, A.; Riedel, N.; Brauer, A.

    2012-04-01

    The DFG funded HIMPAC (Himalaya: Modern and Past Climates) programme aims to reconstruct Holocene Indian Monsoon climate using a multi-proxy and multi-archive approach. First investigations made on sediments from a ca. 10 m long core covering the whole Holocene taken from the lake Lonar in central India's state Maharashtra, Buldhana District, serve to identify changes in sedimentation, lake chemistry, local vegetation and regional to supra-regional climate patterns. Lake Lonar occupies the floor of an impact crater that formed on the ~ 65 Ma old basalt flows of the Deccan Traps. It covers an area of ca. 1 km2 and is situated in India's core monsoon area. The modern lake has a maximum depth of about 5 m, is highly alkaline, and hyposaline, grouped in the Na-Cl-CO3 subtype of saline lakes. No out-flowing stream is present and only three small streams feed the lake, resulting in a lake level highly sensitive to precipitation and evaporation. The lake is eutrophic and stratified throughout most of the year with sub- to anoxic waters below 2 m depth. In this study the core sediments were analysed for their total amino acid (AA) and amino sugar (AS) content, the amino acid bound C and N percentage of organic C and total N in the sediment and the distribution of individual amino acids. The results roughly show three zones within the core separated by distinct changes in their AA content and distribution. (i) The bottom part of the core from ca. 12000 cal a BP to 11400 cal a BP with very low AA and AS percentage indicating high lithogenic contribution, most probably related to dry conditions. (ii) From 11400 cal a BP to 1200 cal a BP the sediments show moderate AA and AS percentages and low values for the ratios of proteinogenic AAs to their non-proteinogenic degradation products (e.g. ASP/β-ALA; GLU/γ-ABA). (iii) The top part of the core (< 1200 cal a BP) is characterised by an intense increase in total AA and AS, AA-C/Corg and AA-N/Ntotas well as in the ratio of

  1. Holocene Paleoenvironment of the North-central Great Basin: Preliminary Results from Favre Lake, Northern Ruby Mountains, Nevada

    NASA Astrophysics Data System (ADS)

    Starratt, S.; Wahl, D.; Wan, E.; Anderson, L.; Wanket, J.; Olson, H.; Lloyd-Davies, T.; Kusler, J.

    2009-12-01

    Little is known about Holocene climate variability in north-central Nevada. This study aims to assess changes in watershed vegetation, fire history, lake levels and limnological conditions in order to understand secular to millennial-scale changes in regional climate. Favre Lake (2,899 m a.s.l.; 12 m deep; 7.7 hectares) is a flow-through lake in the northern Ruby Mountains. The primary sources of influent, both of which appear to be intermittent, are Castle Lake (2,989 m a.s.l.) and Liberty Lake (3,077 m a.s.l.). The bedrock of the three lake basins is early Paleozoic marble and Mesozoic granite and metamorphic rocks. Bathymetric maps and temperature, pH, salinity, and conductivity profiles have been generated for Favre Lake. Surface samples and a series of cores were also collected using a modified Livingstone piston corer. The presence of the Mazama ash in the basal sediment (~4 m below the sediment/water interface) indicates the record extends to ~7,700 cal yr B.P. Magnetic susceptibility (MS) and loss-on-ignition data indicate that the sediments in the lowest part of the core contain primary and reworked Mazama ash. About 2,000 years ago CaCO3 increased from 2 to 3% of the inorganic sediment. The upper 25 cm of the core are marked by an increase in MS which may indicate increased erosion due to grazing. Between about 7,700 and 6,000 cal yr B.P. the diatom flora is dominated by a diverse assemblage of benthic species. The remainder of the core is dominated by Fragilaria, suggesting that lake level rose and flooded the shelf that surrounds the depocenter of the lake. This is supported by changes in the abundance of the aquatic fern Isoetes. Pinus and Artemisia dominate the pollen record, followed by subordinate levels of Poaceae, Asteraceae, Amaranthaceae, and Sarcobatus. The late early Holocene (7,700-6,000 cal yr B.P.) is dominated by Pinus which is present in reduced amounts during the middle Holocene (6,000-3,000 cal yr B.P.) and then returns to dominance in

  2. Solar Cycle Driven Environmental Changes on Decadal to Centennial Scale of Late Miocene Lake Sediments (tortonian, Lake Pannon, Central Europe)

    NASA Astrophysics Data System (ADS)

    Piller, W. E.; Kern, A. K.; Harzhauser, M.; Soliman, A.; Mandic, O.

    2012-12-01

    High time resolution is a key issue in reconstructing past climate systems. This is of particular importance when searching for model predictions of future climate change, such as the warm Late Miocene. For this study we selected Lake Pannon, a paleo-ancient, alkaline, brackish lake in Europe during the Tortonian (early Late Miocene). On a continuous sediment core including the interval from ca. 10.5 - 10.4 Ma we show the power of high resolution multiproxy analyses for reconstructing paleoclimatology on a decadal scale over several millennia of Late Miocene time. To demonstrate this high-resolution interpretation we selected a core from the western margin of Lake Pannon and studied it in respect to 2 different time resolutions. A continuous 6-m-core clearly displays regular fluctuations and modulations within three different environmental proxies (natural gamma radiation, magnetic susceptibility, total abundance of ostracods). Lomb-Scargle and REDFIT periodograms next to wavelet spectra of all data sets reveal distinct frequencies. Only few of these are deciphered in all proxy data sets at the same power, while some occur only in two or one proxies. A higher resolution study was conducted on a 1.5-m-long core interval based on pollen and dinoflagellate cysts, ostracod abundance, carbon and sulfur contents as well as magnetic susceptibility and natural gamma radiation. Based on an already established age model the study covers about two millennia of Late Miocene time with a resolution of ~13.7 years per sample. No major ecological turnovers are expected in respect to this very short interval. Thus, the pollen record suggests rather stable wetland vegetation with a forested hinterland. Shifts in the spectra can be mainly attributed to variations in transport mechanism, represented by few phases of fluvial input but mainly by changes in wind intensity and probably also wind direction. Even within this short time span, dinoflagellates document rapid changes between

  3. A new high-resolution sediment record from Lake Gościąż (central Poland)

    NASA Astrophysics Data System (ADS)

    Bonk, Alicja; Błaszkiewicz, Mirosław; Brauer, Achim; Brykała, Dariusz; Gierszewski, Piotr; Kramkowski, Mateusz; Plessen, Brigit; Schwab, Markus; Słowiński, Michał; Tjallingii, Rik

    2017-04-01

    The varved sediments from Lake Gościąż, located in the Vistula Valley in Central Poland, are an iconic record for palaeoclimate and palaeoenvironmental reconstruction (Goslar et al. 2000, Hajdas et al. 1995, Ralska-Jasiewiczowa et al. 1998). Recently, we obtained a set of new sediment cores from Lake Gościąż and established a 21 m long sediment profile. Except of the topmost part of the core, it is continuously laminated down to glacial sands. We aim at applying a comprehensive multi-proxy core analyses combined with monitoring of present-day sedimentation processes. Sediment investigations will include new methods that have been developed or advanced since the previous studies on the Lake Gościąż sediments including continuous micro-facies analyses, μXRF core scanning and tephrochronology. The main aims of our new project are a revision of the existing floating chronology and to synchronise the Lake Gościąż sediment record based on independent isochrones with other European varved lake records like, e.g. Lake Meerfelder Maar, in order to investigate in detail proxy responses to climate change and to decipher regional leads and lags in climate change. Here, we will present (1) the objectives of our new project on this key record of past climate and environmental change and, (2) preliminary results including magnetic susceptibility, μ-XRF core scanning and microfacies images. This study is a contribution to scientific project financed by the National Science Centre, Poland - No DEC-2015/19/B/ST10/03039.

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

    PubMed

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

    2011-12-01

    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 isotope and chemical composition of lake water and adjoining glacier ice suggests strong differences in the long-term evolution between the lakes Untersee and Obersee. First data from a lakelet, embedded in the large morainic area to the west of Lake Untersee, are of special interest: the δ(2)H values of the lakelet water are lower than those of recent regional glacier ice by 50‰ SMOW. This fact indicates that the lakelet is fed episodically by Pleistocene dead ice, covered by the morainic material.

  5. Water level monitoring using radar remote sensing data: Application to Lake Kivu, central Africa

    NASA Astrophysics Data System (ADS)

    Munyaneza, Omar; Wali, Umaru G.; Uhlenbrook, Stefan; Maskey, Shreedhar; Mlotha, McArd J.

    Satellite radar altimetry measures the time required for a pulse to travel from the satellite antenna to the earth’s surface and back to the satellite receiver. Altimetry on inland lakes generally shows some deviation from in situ level measurements. The deviation is attributed to the geographically varying corrections applied to account for atmospheric effects on radar waves. This study was focused on verification of altimetry data for Lake Kivu (2400 km 2), a large inland lake between Rwanda and the Democratic Republic of Congo (DRC) and estimating the lake water levels using bathymetric data combined with satellite images. Altimetry data obtained from ENVISAT and ERS-2 satellite missions were compared with water level data from gauging stations for Lake Kivu. Gauge data for Lake Kivu were collected from the stations ELECTROGAZ and Rusizi. ENVISAT and ERS-2 data sets for Lake Kivu are in good agreement with gauge data having R2 of 0.86 and 0.77, respectively. A combination of the two data sets improved the coefficient of determination to 95% due to the improved temporal resolution of the data sets. The calculated standard deviation for Lake Kivu water levels was 0.642 m and 0.701 m, for ENVISAT and ERS-2 measurements, respectively. The elevation-surface area characteristics derived from bathymetric data in combination with satellite images were used to estimate the lake level gauge. Consequently, the water level of Lake Kivu could be estimated with an RMSE of 0.294 m and an accuracy of ±0.58 m. In situations where gauges become malfunctioning or inaccessible due to damage or extreme meteorological events, the method can be used to ensure data continuity.

  6. A 400-ka tephrochronological framework for Central America from Lake Petén Itzá (Guatemala) sediments

    NASA Astrophysics Data System (ADS)

    Kutterolf, S.; Schindlbeck, J. C.; Anselmetti, F. S.; Ariztegui, D.; Brenner, M.; Curtis, J.; Schmid, D.; Hodell, D. A.; Mueller, A.; Pérez, L.; Pérez, W.; Schwalb, A.; Frische, M.; Wang, K.-L.

    2016-10-01

    Lake Petén Itzá, northern Guatemala, lies within a hydrologically closed basin in the south-central area of the Yucatán Peninsula, and was drilled under the auspices of the International Continental Scientific Drilling Program (ICDP) in 2006. At 16°55‧N latitude, the lake is ideally located for study of past climate and environmental conditions in the Neotropical lowlands. Because of its great depth (>160 m), Lake Petén Itzá has a record of continuous sediment accumulation that extends well into the late Pleistocene. A key obstacle to obtaining long climate records from the region is the difficulty of establishing a robust chronology beyond ∼40 ka, the limit of 14C dating. Tephra layers within the Lake Petén Itzá sediments, however, enable development of age/depth relations beyond 40 ka. Ash beds from large-magnitude, Pleistocene-to-Holocene silicic eruptions of caldera volcanoes along the Central American Volcanic Arc (CAVA) were found throughout drill cores collected from Lake Petén Itzá. These ash beds were used to establish a robust chronology extending back 400 ka. We used major- and trace-element glass composition to establish 12 well-constrained correlations between the lacustrine tephra layers in Lake Petén Itzá sediments and dated deposits at the CAVA source volcanoes, and with their marine equivalents in eastern Pacific Ocean sediments. The data also enabled revision of eight previous determinations of erupted volumes and masses, and initial estimates for another four eruptions, as well as the designation of source areas for 14 previously unknown eruptions. The new and revised sedimentation rates for the older sediment successions identify the interglacial of MIS5a between 84 and 72 ka, followed by a stadial between 72 and 59 ka that corresponds to MIS4. We modified the age models for the Lake Petén Itzá sediment sequences, extended the paleoclimate and paleoecological record for this Neotropical region to ∼400 ka, and determined the

  7. Analysis and simulation of ground-water flow in Lake Wales Ridge and adjacent areas of central Florida

    USGS Publications Warehouse

    Yobbi, Dann K.

    1996-01-01

    The Lake Wales Ridge is an uplands recharge area in central Florida that contains many sinkhole lakes. Below-normal rainfall and increased pumping of ground water have resulted in declines both in ground-water levels and in the water levels of many of the ridge lakes. A digital flow model was developed for a 3,526 square-mile area to help understand the current (1990) ground-water flow system and its response to future ground-water withdrawals. The ground-water flow system in the Lake Wales Ridge and adjacent area of central Florida consists of a sequence of sedimentary aquifers and confining units. The uppermost water-bearing unit of the study area is the surficial aquifer. This aquifer is generally unconfined and is composed primarily of clastic deposits. The surficial aquifer is underlain by the confined intermediate aquifer and confining units which consists of up to three water-bearing units composed of interbedded clastics and carbonate rocks. The lowermost unit of the ground- water flow system, the confined Upper Floridan aquifer, consists of a thick, hydraulically connected sequence of carbonate rocks. The Upper Floridan aquifer is about 1,200 to 1,400 feet thick and is the primary source for ground-water withdrawals in the study area. The generalized ground-water flow system of the Lake Wales Ridge is that water moves downward from the surficial aquifer to the intermediate aquifer and the Upper Floridan aquifer in the central area, primarily under the ridges, with minor amounts of water flow under the flatlands. The water flows laterally away fromn the central area, downgradient to discharge areas to the west, east, and south, and locally along valleys of major streams. Upward leakage occurs along valleys of major streams. The model was initially calibrated to the steady-state conditions representing September 1989. The resulting calibrated hydrologic parameters were then tested by simulating transient conditions for the period October 1989 through 1990. A

  8. Palaeoenvironmental and palaeoclimatic implications of the Late-Quaternary sediment record of Vico volcanic lake (central Italy)

    NASA Astrophysics Data System (ADS)

    Narcisi, Biancamaria

    2001-03-01

    A 15-m-long sediment core recovered from the Lago di Vico caldera lake in central Italy has been the subject of macrofacies description and sedimentological (organic carbon content, grain size and mineralogy) investigation. The results have been integrated with the pollen data from the same core in order to provide a regional climatic and environmental history, with inferences on past lake levels and on moisture and temperature regimes. Radiometric (14C and 40Ar/39Ar) dating, biostratigraphical considerations and tephra analyses provide a chronological framework and indicate that the sequence spans the last 90 000 yr. Several moist periods have been identified that were characterised by enhanced weathering by hydrolysis of the catchment rocks. These alternated with relatively dry phases associated with lowering of lake-levels. The lowest hydrolysis efficiency of the whole record, accompanied by notable aeolian deposition, was attained during the last glacial phase but moisture conditions were such that the lake-level did not decrease, probably owing to reduced temperatures. Evidence for cool climate also emerges for the early Pleniglacial. The highest available moisture was achieved within the Holocene at 5 kyr BP. The Late Holocene does not show either increase of aridity or degradation of the vegetation cover, until at least Roman times.

  9. Molecular tracers of saturated and polycyclic aromatic hydrocarbon inputs into Central Park Lake, New York City

    SciTech Connect

    Beizhan Yan; Teofilo A. Abrajano; Richard F. Bopp; Damon A. Chaky; Lucille A. Benedict; Steven N. Chillrud

    2005-09-15

    Saturated hydrocarbons (SH) and polycyclic aromatic hydrocarbons (PAHs) have been quantified in a sediment core obtained from Central Park Lake, New York City. Radionuclides {sup 210}Pb and {sup 137}Cs were used to assign approximate dates to each individual section in the core. The dating profile based on {sup 210}Pb matches very well with the time constraints provided by {sup 137}Cs. Radionuclide-derived depositional dates are consistent with temporal information from the petroleum-indicator ratio U/R (the ratio of unresolved complex mixture (UCM) to saturated hydrocarbons in the aliphatic fraction) and the history of fuel use in the NYC area. Ratios of 1,7-dimethylphenanthrane (DMP) to 1,7-DMP plus 2,6-DMP (1,7/(1,7 + 2,6)-DMP), retene to retene plus chrysene (Ret/(Ret + Chy)), and fluoranthene to fluoranthene plus pyrene (Fl/(Fl + Py))) provide additional source discrimination throughout the core. Results show that the ratio U/R is sensitive to petroleum inputs and Ret/(Ret + Chy) is responsive to contributions from softwood combustion, whereas both Fl/(Fl + Py) and 1,7/(1,7 + 2,6)-DMP can be used to discriminate among wood, coal, and petroleum combustion sources. Combined use of these ratios suggests that in New York City, wood combustion dominated 100 years ago, with a shift to coal combustion occurring from the 1900s to the 1950s. Petroleum use began around the 1920s and has dominated since the 1940s. 33 refs., 3 figs., 2 tabs.

  10. Stratigraphy and Facies Analysis of a 122 M Long Lacustrine Sequence from Chalco Lake, Central Mexico

    NASA Astrophysics Data System (ADS)

    Herrera, D. A.; Ortega, B.; Caballero, M.; Lozano, S.; Pi, T.; Brown, E. T.

    2010-12-01

    Chalco lake is located SE of the outskirts of Mexico City, at the central part of the Trans Mexican Volcanic Belt. Previous studies show the importance of this lacustrine sequence as an archive of paleoenvironmental and paleoclimatic changes. A set of five cores up to 122 m depth were drilled in the basin, in order to analyze the sedimentary record and to extent the previous knowledge of past environmental changes in central Mexico. As an initial step, in this work we present the identification and classification of sedimentary facies. Preliminary paleomagnetism analyses recognize the possible record of the Blake Event (ca. 120 kyr BP), and suggest that the sequence might span the last 240 kyr. In this case, variations in sedimentary facies could reflect the conditions of the MIS 1-7. The facies are mostly diatom ooze, carbonate mud, organic rich silt and volcaniclastic, both massive and laminated, and massive dark gray to reddish brown silt. From 1 to 8 m depth dominates the organic rich silt facies, which correlates with the MIS 1. Intercalations of reddish brown and grayish brown silt facies, between 8 to 60 m depth, indicate changes occurred during MIS 2 to 5d. Between 60-75 m depth the sequence is characterized by dark grayish silty clay facies, which possibly coincide with the MIS 5e. At 79 m depth (ca. 130 kyr BP) we found struvite (MgNH4PO4.6H2O), which may be related to dry conditions. The laminated diatom ooze facies dominates between 90 to 122 m depth and indicates rhythmic changes in the sediment deposition of the basin. The volcaniclastic facies is represented by lapilli and ash deposits in more than 100 individual tephra layers of both mafic and felsic composition. Some of them correspond to main volcanic eruptions, as the Upper Toluca Pumice (13,500 cal yr BP), from the Nevado de Toluca volcano and the Pómez con Andesita (17,700 cal yr BP) from the Popocatépetl volcano. The carbonate mud facies is composed of calcite and siderite, with frequent

  11. Late Quaternary herpetofauna of the Central Great Lakes region, U.S.A.: Zoogeographical and paleoecological implications

    NASA Astrophysics Data System (ADS)

    Holman, J. Alan

    Late Quaternary herpetological records from the Central Great Lakes States of Michigan, Illinois, Indiana and Ohio allow for reflections on reinvasion of herpetological species into previously uninhabitable areas, as well as some comments on paleoclimate. Advances of the Wisconsinan Laurentide ice sheet obliterated herpetological habitat in all of Michigan as well as much of Illinois, Indiana and Ohio; it also restricted herpetological habitat in the southern parts of the three latter states. By about 15-14 ka BP a rich herpetofauna, similar to the one that occurs in the area today, and suggesting a moderate climate, occurred in southwestern Indiana. Turtle faunas in central Indiana (13-12 ka BP) and west-central Ohio (11-10 ka BP) suggest that warm summer climates existed in those areas at the time. On the other hand authentic reptile records are unknown from the Pleistocene of Michigan, and considering the pollen record, that state probably had a much colder climate during postglacial Late Wisconsinan times. A well-developed turtle fauna associated with temperate deciduous forest occurred in southern Michigan about 6 ka BP, and a rich herpetofauna, similar to the one that occurs in the area today, occurred in southwestern Indiana about 4 ka BP. This evidence suggests the possibility that the herpetological reinvasion of the Central Great Lakes region might have been nearly complete by Mid-Holocene times.

  12. Role of lake regulation on glacier fed rivers in enhancing salmon productivity: The Cook Inlet watershed south central Alaska, USA

    USGS Publications Warehouse

    Hupp, C.R.

    2000-01-01

    Rivers fed by glaciers constitute a major part of the freshwater runoff into the Cook Inlet basin of south-central Alaska. This basin is very important to the economy of the State of Alaska because it is home to more than half of the population and it supports multi-million dollar commercial, subsistence and sport fisheries. Hence an understanding of how glacial runoff influences biological productivity is important for managing rivers that drain into Cook Inlet. This paper examines the ways in which the regulation of glacier-fed rivers by proglacial lakes affects salmon productivity, with particular reference to the Kenai River. Salmon escapement per unit channel length on the Kenai River is between two and ten times that found for rain-and-snowmelt dominated rivers and glacier-fed rivers lacking lake regulation. Lakes are shown to influence biological processes in glacier-fed rivers by attenuating peak flows, sustaining high flows throughout the summer, supplementing winter low flows, settling suspended sediment, and increasing river temperatures. Downstream from large lakes, glacier-fed rivers are less disturbed, channels are relatively stable and have well-developed salmonid habitats. The positive influences are indicated by the high diversity and abundances of benthic macroinvertebrates, which are important food resources for juvenile salmonids. High summer flows allow access for up-river salmon runs and lakes also provide both overwintering and rearing habitat. Copyright ?? 2000 John Wiley & Sons, Ltd.Rivers fed by glaciers constitute a major part of the freshwater runoff into the Cook Inlet basin of south-central Alaska. This basin is very important to the economy of the State of Alaska because it is home to more than half of the population and it supports multi-million dollar commercial, subsistence and sport fisheries. Hence an understanding of how glacial runoff influences biological productivity is important for managing rivers that drain into Cook Inlet

  13. Age, growth, sex ratio, and maturity of the whitefish in central Green Bay and adjacent waters of Lake Michigan

    USGS Publications Warehouse

    Mraz, Donald

    1964-01-01

    This study is based on 1,023 whitefish, Coregonus clupeaformis (Mitchill)--819 in seven samples from five localitites in central Green Bay in 1948-49 and 1851-52 and 204 in a single 1948 collection from northwestern Lake Michigan proper. Records of age indicated unusual strength for only one year class--1943 which strongly dominated the 1948 sample from Lake Michigan and the 1949 sample from Green Bay and was well represented in the 1948 collection from green Bay. Collection of 1951-52 without exception were dominated by age group III. Length distributions of samples varied widely according to the age composition. Among fish more than 2 years old, the length distributions of age groups overlapped broadly. Several 1-inch intervals included fish of four age groups. The length-weight relation varied considerably among central Green Bay samples, but differences among localitites were nearly equalled by the year-to-year difference at a single locality. Lake Michigan whitefish were generally lighter than those from Green Bay. Weight increased to the 3.386 power of length in Green Bay (combined samples) and the 3.359 power in Lake Michigan. Growth in length, calculated by direct proportion from diameter measurements of growth fields on scales, differed among localities in central Green Bay and between samples of different years at a single locality. If permanent locality differences exist they are not large and can be obscured by the evident annual fluctuations of growth. The grand average calculated length of Green Bay whitefish (combined collections) exceeded that of Lake Michigan fish in all years of life. The advantage was greatest (2.2 inches) at 3 years (calculated lengths of 16.0 inches and 13.8 inches) and subsequently declined to 0.5 inch at 9 years (lengths of 24.6 and 24.1 inches). Both groups reached the minimum legal length of 17 inches during the fourth growing season. Green Bay whitefish also had the larger calculated weights. The advantage reached 9

  14. Widespread waterborne pollution in central Swedish lakes and the Baltic Sea from pre-industrial mining and metallurgy.

    PubMed

    Bindler, Richard; Renberg, Ingemar; Rydberg, Johan; Andrén, Thomas

    2009-07-01

    Metal pollution is viewed as a modern problem that began in the 19th century and accelerated through the 20th century; however, in many parts of the globe this view is wrong. Here, we studied past waterborne metal pollution in lake sediments from the Bergslagen region in central Sweden, one of many historically important mining regions in Europe. With a focus on lead (including isotopes), we trace mining impacts from a local scale, through a 120-km-long river system draining into Mälaren--Sweden's third largest lake, and finally also the Baltic Sea. Comparison of sediment and peat records shows that pollution from Swedish mining was largely waterborne and that atmospheric deposition was dominated by long-range transport from other regions. Swedish ore lead is detectable from the 10th century, but the greatest impact occurred during the 16th-18th centuries with improvements occurring over recent centuries, i.e., historical pollution > modern industrial pollution.

  15. InSAR measurement of the deformation around Siling Co Lake: Inferences on the lower crust viscosity in central Tibet

    NASA Astrophysics Data System (ADS)

    Doin, Marie-Pierre; Twardzik, Cédric; Ducret, Gabriel; Lasserre, Cécile; Guillaso, Stéphane; Jianbao, Sun

    2015-07-01

    The Siling Co Lake is the largest endorheic lake in Central Tibet. Altimetric measures, combined with lake contours, show that in 1972-1999 its water level remained stable, while it increased by about 1.0 m/yr in the period 2000-2006. The increased rate gradually stepped down to 0.2 m/yr in 2007-2011. The ground motion associated with the water load increase is studied by interferometric synthetic aperture radar (InSAR) using 107 ERS and Envisat SAR images during the period 1992-2011. The deformation amplitude closely follows the lake level temporal evolution, except that subsidence continues in 2008-2011, while the lake level stagnated. This temporal evolution suggests a non elastic relaxation process taking place at a decade timescale. Phase delay maps are used to constrain possible layered viscoelastic rheological models. An elastic model could partly explain the observed subsidence rate if elastic moduli are about twice lower than those extracted from VP/VS profiles. The surface deformation pattern is also extracted by projecting the phase delay maps against the best fit model temporal behavior. It shows that deep relaxation in the asthenosphere is negligible at the decade timescale and favors the existence of a ductile channel in the deep crust above a more rigid mantle. Overall, the best fit model includes a ductile lower crust, with a viscosity of 1-3 × 1018 Pa s between 25 and 35 km and the Moho (at 65 km), overlying a rigid mantle.

  16. Reconstruction of Holocene Climate Variability within the Central Mediterranean Using Lake Sediments from the Akrotiri Peninsula, Crete

    NASA Astrophysics Data System (ADS)

    Magill, C. R.; Rosenmeier, M. F.; Cavallari, B. J.; Curtis, J. H.; Weiss, H.

    2005-12-01

    Middle and late Holocene geochemical records from the Limnes depression, a small sinkhole located within the Akrotiri Peninsula, Crete, document centennial and millennial-scale climate variability within the central Mediterranean region. The oldest sediments of the basin consist largely of fibrous plant macrofossils and organic matter and likely indicate lake filling and expansion of wetland vegetation beginning ~5700 radiocarbon years before present (14C-yrs B.P.) (4550 B.C.). The basal peat layers grade into predominantly open water and less shallow lacustrine deposits by 4500 14C-yrs B.P (3200 B.C.). Continuous open water sedimentation within the Limnes core is interrupted by a number of distinct lag deposits and peaty deposits centered at 3700, 1600, and 350 14C-yrs B.P (2100 B.C., 500 A.D., and 1500 A.D.) indicating periods of significantly lowered lake level or perhaps lake desiccation. These ages coincide roughly with oxygen isotope (δ18O) minima measured in biogenic carbonates (ostracod shells) and support the inference for low lake stage. Trace element (Ca, Mg, and Sr) concentrations in ostracod shells from the Limnes core parallel the oxygen isotope record, suggesting that the data reflect basin hydrology rather than changes in the isotopic composition of rainfall. Furthermore, covariance in both δ18O and Mg concentrations eliminate temperature as a control on the oxygen isotope record. Sediments from the basin also contain aragonite remains of the green alga Chara and isotope analysis of the calcite may record additional paleoenvironmental information. The paleoclimate history inferred from the Limnes record correlates temporally (albeit tenuously) to previous paleoenvironmental data that document abrupt onset of arid conditions in the eastern Mediterranean and western Asia ca. 2200 B.C. Moreover, stratigraphic and geochemical evidence of low lake level (drying) within the Limnes basin at 2100 B.C. may correspond to the termination of the Early Minoan

  17. Forest responses to late Holocene climate change in north-central Wisconsin: a high- resolution study from Hell's Kitchen Lake.

    NASA Astrophysics Data System (ADS)

    Urban, M. A.; Booth, R. K.; Jackson, S. T.; Minckley, T. A.

    2007-12-01

    Forest dynamics at centennial to millennial timescales can be identified using paleoecological records with high spatial, temporal, and taxonomic resolution. These dynamics are linked to climate changes by comparing the paleoecological records with independent paleoclimate records of complementary sensitivity and temporal resolution. We analyzed plant macrofossils at contiguous 1cm intervals (representing 5 to 35 yr/cm) from late Holocene sediments of Hell's Kitchen Lake (3 ha) in north-central Wisconsin. Most of the plant macrofossils derive from trees growing on the slopes directly adjacent to the lake, and were identified to the species. We also analyzed pollen at an approximately100 year resolution to provide a regionally integrated record of forest composition. We then compared the macrofossil and pollen records with independent records of climate change in the region, particularly paleohydrological records from kettle bogs. The most notable feature of the late Holocene record occurs between 2300-2000 cal yr BP. During this period yellow birch (Betula alleghaniensis) macrofossils first appear in the record, along with a corresponding increase in pollen percentages. Hemlock (Tsuga canadensis) macrofossils and pollen also show a marked increase at this time. These changes coincide with a major transition towards wetter conditions recorded in the testate amoebae record of Hornet Bog (~200km northwest) and in a number of other kettle bog records from the region. Directly following this transition, tamarack (Larix laricina) and Sphagnum macrofossils at Hell's Kitchen Lake increase dramatically, likely representing the initiation of bog-mat growth along the southwest margin of the lake during the wet period. . We are continuing our high-resolution sampling downcore at Hell's Kitchen Lake. This will permit us to examine additional ecologic and climatic events in the early and mid-Holocene.

  18. Hydrologic reconnaissance of the southern Great Salt Lake Desert and summary of the hydrology of west-central Utah

    USGS Publications Warehouse

    Gates, Joseph S.; Kruer, Stacie A.

    1981-01-01

    This report is the last of 19 hydrologic reconnaissances of the basins in western Utah. The purposes of this series of studies are (1) to analyze available hydrologic data and describe the hydrologic system, (2) to evaluate existing and potential water-resources development, and (3) to identify additional studies that might be needed. Part 1 of this report gives an estimate of recharge and discharge, an estimate of the potential for water-resources development, and a statement on the quality of water in the southern Great Salt Lake Desert part of west-central Utah. Part 2 deals with the same aspects of west-central Utah as a whole. Part 2 also summarizes the evidence of interbasin ground-water flow in west-central Utah and presents a theory for the origin of the water discharged from Fish Springs.

  19. Remotely sensed surface temperature variation of an inland saline lake over the central Qinghai-Tibet Plateau

    NASA Astrophysics Data System (ADS)

    Ke, Linghong; Song, Chunqiao

    2014-12-01

    Research on surface water temperature (SWT) variations in large lakes over the Qinghai-Tibet Plateau (QTP) has been limited by lack of in situ measurements. By taking advantage of the increased availability of remotely sensed observations, this study investigated SWT variation of Siling Co in central QTP by processing complete MODIS Land surface temperature (LST) images over the lake covering from 2001 to 2013. The temporal (diurnal, intra-annul and inter-annul) variations of Siling Co SWT as well as the spatial patterns were analyzed. The results show that on average from late December to mid-April the lake is in a mixing state of water and ice and drastic diurnal temperature differences occur, especially along the shallow shoreline areas. The extent of spatial variations in monthly SWT ranges from 1.25 °C to 3.5 °C, and particularly large at nighttime and in winter months. The spatial patterns of annual average SWT were likely impacted by the cooling effect of river inflow from the west and east side of the lake. The annual cycle of spatial pattern of SWT is characterized by seasonal reversions between the shallow littoral regions and deep parts due to different heat capacity. Compared to the deep regions, the littoral shallow shoreline areas warms up quickly in spring and summer, and cool down drastically in autumn and winter, showing large diurnal and seasonal variation amplitudes of SWT. Two cold belt zones in the western and eastern side of the lake and warm patches along the southwestern and northeastern shorelines are shaped by the combined effects of the lakebed topography and river runoff. Overall, the lake-averaged SWT increased at a rate of 0.26 °C/decade during 2001-2013. Faster increase of temperature was found at nighttime (0.34 °C/decade) and in winter and spring, consistent with the asymmetric warming pattern over land areas reported in prior studies. The rate of temperature increase over Siling Co is remarkably lower than that over Bangoin

  20. Hydrological and sedimentological regime of lower Vistula fluvial lakes (North Central Poland)

    NASA Astrophysics Data System (ADS)

    Kordowski, Jarosław; Kubiak-Wójcicka, Katarzyna; Tyszkowski, Sebastian; Solarczyk, Adam

    2015-04-01

    Regarding the outflow the Vistula River is the largest river in the Baltic catchment. In its lower course it has developed an anastomosing channel pattern modified strongly by intensive human hydrotechnical activity and by the regulation which have intensified about 200 years ago. Channel regulation apart from already existing lakes have left many new artificially created ones. This activity have also altered the hydrological and sedimentary regime. It turned out that only the small portion of the lakes infilled rapidly but the majority have persisted to present day almost unchanged in spite of regulation. The reason of this resistence to silting is connected with specific interaction of sediment removing during high flood water episodes and strong groundwater circulation in former river arms transformed in present-day lakes. As an example of a lake with an intensive groundwater exchange rate with the main Vistula channel and supposed Quaternary and Tertiary aquifers was selected the Old Vistula lake (Stara Wisła) near Grudziądz town. It has got an area of 50 ha, mean depth 1,73 m, maximum depth 8 m, length about 4 km and medium width about 100 m. In the years 2011-2015 in its surficial water were conducted measures with two weeks frequency which included: temperature, pH, Eh, suspended matter amount, total and carbonaceous mineralization. For comparison similar measurements were also conducted in other fluvial lakes and Vistula tributaries. Hydrological data were supplemented by geological investigations of floodplain sediments cover which has important impact on the rate of groundwater migration and circulation. Investigations carried proved that there exists distinct gradient of carbonaceous mineralization from small values in the Vistula channel to high values at the valley edges. PH and Eh parameters in the Old Vistula lake were different than in all other surveyed sites what leads to conclusion that it is fed by deeper groundwaters than in the case of other

  1. Hydrologic analysis of two headwater lake basins of differing lake pH in the west-central Adirondack Mountains of New York

    USGS Publications Warehouse

    Murdoch, Peter S.; Peters, N.E.; Newton, R.M.

    1987-01-01

    Hydrologic analysis of two headwater lake basins in the Adirondack Mountains, New York, during 1980-81 indicates that the degree of neutralization of acid precipitation is controlled by the groundwater contribution to the lake. According to flow-duration analyses, daily mean outflow/unit area from the neutral lake (Panther Lake, pH 5-7) was more sustained and contained a higher percentage of groundwater than that of the acidic lake (Woods Lake, pH 4-5). Outflow recession rates and maximum base-flow rates, derived from individual recession curves, were 3.9 times and 1.5 times greater, respectively, in the neutral-lake basin than in the acidic-lake basin. Groundwater contribution to lake outflow was also calculated from a lake-water budget; the groundwater contribution to the neutral lake was about 10 times greater than that to the acidic lake. Thick sandy till forms the groundwater reservoir and the major recharge area in both basins but covers 8.5 times more area in the neutral-lake basin than in the acidic-lake basin. More groundwater storage within the neutral basin provides longer contact time with neutralizing minerals and more groundwater discharge. As a result, the neutral lake has relatively high pH and alkalinity, and more net cation transport. (USGS)

  2. Preliminary Results of a Multi-Proxy Lake Sediment Core Study in East-Central France

    NASA Astrophysics Data System (ADS)

    Misner, T.; Meyers, S.; Rosenmeier, M.; Strano, S.; Straffin, E.

    2008-12-01

    This paper presents the preliminary results of a multi-proxy study of natural and human-induced changes in the Burgundian environment, as recorded in the sediment geochemistry of three small freshwater basins within the Arroux River Valley, east-central France. Accelerator mass spectrometry radiocarbon dates constrain the age of core material collected from the basins, and indicate that these mill and farm ponds were constructed by at least 1200 A.D. The pond sediments are predominantly massive, organic-rich muds that contain discrete sand and gravel lenses likely related to episodic flooding and/or basin drainage. In this study, continuous X-ray fluorescence (XRF) scanning is used to quantify bulk geochemical variability throughout the lake sediment cores, and to investigate specific elemental proxies for paleoenvironmental change (detrital flux, biogenic flux, and redox state). The high-resolution XRF data are supplemented by sediment magnetic susceptibility measurements, and organic matter concentration as determined by loss on ignition. These records demonstrate a general increase in detrital sediment input from 1200 to 1300 A.D., during a period of known regional agricultural expansion. We infer these changes to be the consequence of increased catchment soil erosion and material flux to the water bodies. The data also suggest changes in mill and farm pond primary productivity, also related to soil erosion and changing transport of soil nutrients to the basins. Near the onset of the Little Ice Age (ca. 1500 A.D.) pond productivity reductions are apparent, likely indicating colder climates. These mill and farm pond sedimentary archives, in conjunction with historic records, can be used to better understand past land management strategies. Furthermore, historically documented landscape changes can be examined within the context of prevailing climatic conditions over the last ~800 years in an effort to establish future best management practices and the most

  3. Findings of historical Icelandic (Askja AD 1875) tephras in varved lake records from Lake Tiefer See and Lake Czechowskie: a new potential for synchronizing the recent environmental history in NE Germany and N central Poland

    NASA Astrophysics Data System (ADS)

    Wulf, Sabine; Dräger, Nadine; Ott, Florian; Serb, Johanna; Brauer, Achim

    2014-05-01

    Identification of remnants of volcanic ashes (tephras) intercalated in lake sediments has become a crucial point for dating purposes and for synchronization of different sediment records. During the Late Glacial and the Holocene Northeastern Germany and Northern-central Poland were episodically impacted by ash clouds of larger eruptions from Icelandic volcanoes (e.g. Saksunarvatn, 10.2 cal ka BP, and Vedde Ash, 12.1 cal ka BP); the most recent ones in 2010 and 2011 occurred from rather low-scale eruptions from Eyjafjallajökull and Grimsvötn resulting in an interruption of air traffic and local deposition of fine grained ash. We have started an intense search for traces of these volcanic ashes (cryptotephras) and other historic Icelandic tephras in two annually laminated palaeoclimate records, Lake Tiefer See (NE Germany) and Lake Czechowskie (N central Poland), in order to verify the 14C supported varve chronologies of these sequences. Lake Czechowskie and Lake Tiefer See are both located within the terminal moraine of the Pomeranian ice advance of the last glaciation and encompass continuous sediment records since the Late Glacial. First results of tephrochronological investigations revealed a cryptotephra finding of the rhyolitic Askja AD 1875 ash in both sequences. The Phreatoplinian Askja AD 1875 eruption is considered as the largest Icelandic eruption in history, comparable with the 1991-Pinatubo eruption. Due to strong westerly winds the Askja AD 1875 Tephra was distributed towards the east as evidenced by documentary records and occurrences in numerous peat bogs in Norway and Sweden. A tentative finding was reported from Grambower Moor in N Germany suggesting a subsequent southward moving ash cloud over Sweden (van den Bogaard and Schmincke, 2002). With the ultra-distal cryptotephra findings in Lake Tiefer See and Lake Czechowskie, ca. 2060 km and 2300 km SE of the Icelandic source, respectively, we can confirm the southward ash dispersal and provide an

  4. Lava Flows, Rivers, and Lakes: Complex Interactions Along the McKenzie River, Central Oregon

    NASA Astrophysics Data System (ADS)

    Deligne, N. I.; Cashman, K. V.; Grant, G. E.

    2008-12-01

    There are few studies of lava - surface water interactions, undoubtedly because most contemporary research on lava flows has been carried out in places with little surface water (e.g., Hawaii and Mt Etna). However, as described by a written account of the 1783 Laki eruption in Iceland, this interaction can be quite dynamic and dramatic: lava flows can disrupt water sources and rivers, simultaneously causing water shortages downstream and severe flooding upstream. In the Cascade volcanic range there are numerous examples of pre-historic Holocene lava - surface water interaction. For example, multiple lava flows have entered the McKenzie River, which occupies the western margin of High Cascades graben. Clear Lake, at the head of the McKenzie River, formed when lava flows from the Sand Mountain chain entered the ancestral McKenzie River and dammed it; dated drowned trees preserved on the lake bottom suggest that damming occurred c. 3000 years ago. While the modern forest masks the location and extent of the damming lava flow, principle components analysis of Landsat imagery helps to define flow boundaries and areal extent. This extensive flow is at least 54 meters thick and flowed west until it encountered the graben wall, at which point it flowed south, burying and damming the ancestral McKenzie River. The river currently overtops the lava dam and travels south along the graben wall. Poorly vegetated flows enter Clear Lake on its eastern margin; while early workers mapped two separate flow units around Clear Lake with younger flows distinguished by their lack of vegetation, recent workers have mapped all flows bordering Clear Lake as part of the same complex. We agree with earlier interpretations and additionally use bathymetric studies to show that the lake prematurely stopped the advance of these younger lava flows. Further downstream, flows from Belknap volcano entered the McKenzie River approximately 1500 years after the formation of Clear Lake. While these flows

  5. Lake Tangra Yumco as an archive for paleo-monsoon dynamics on the central Tibetan Plateau (China)

    NASA Astrophysics Data System (ADS)

    Kasper, T.; Haberzettl, T.; Daut, G.; Mäusbacher, R.; Wang, J.; Zhu, L.

    2011-12-01

    In previous studies Nam Co (Co=lake) was figured out to be a suitable site for monsoon reconstruction on the Tibetan Plateau (TP). Here we present first results from Tangra Yumco (4535 m a.s.l.; 31°06'N; 86°37'E; 818 km^2) which is the prerequisite resumption of an E-W transect across the TP to advance in the reconstruction of paleo-monsoon dynamics. Hydro-acoustic data were recorded at Tangra Yumco to gather information on the bathymetry as well as on the structure and thickness of the sediments. Sediment gravity cores were recovered from the deepest part of the lake. A multi-dating approach using radiocarbon dating and paleomagnetic measurements was applied to establish a reliable chronology. High-resolution XRF core-scans, radiographic imaging and grain size analyses were carried out. The N-S-oriented lake reveals two separate parts with different water depths of ~100 m in the South and ~220 m in the North. Seismic records show well layered deposits up to 25 m (no basement detected) within different acoustic units, slump- and tectonic structures as well as subaqueous lake-level terraces and beach berms/dunes down to 45 m below the recent lake level. On the other hand terraces of lake level high stands are evident up to ~205 m above the today's lake level. Within the recovered sediment records event layers are intercalated between finely laminated sediments. The processes causing these structures up to now are not completely understood, but might be linked to lake level variations (terrace formation), heavy rainfall events or even earthquakes as the lake is situated in a tectonic highly active area. The two sediment cores recovered from the northern part of the lake (TAN 10/1, 168 cm, western slope, ~180 m water depth; TAN 10/4, 163 cm, central basin, ~220 m water depth) were dated using bulk radiocarbon dating. A carbon-reservoir effect was determined to be ~2120 (+110/-90) years. This was obtained by dating the sediment surface at each coring site as well as

  6. Elemental profiles in feather samples from a mercury-contaminated lake in central california

    PubMed

    Cahill; Anderson; Elbert; Perley; Johnson

    1998-07-01

    Flight feathers from six bird species at Clear Lake, CA were analyzed to determine the extent and distribution of mercury contamination from an abandoned mercury mine and associated levels of 14 other elements. Feather samples were collected from adult and juvenile osprey (Pandion haliaetus), including juvenile osprey from three additional comparison sites; adult western grebes (Aechmophorus occidentalis); adult great blue herons (Ardea herodias); adult mallards (Anas platyrhynchos); adult turkey vultures (Cathartes aura); and juvenile double-crested cormorants (Phalacrocorax auritus). Samples were analyzed by a multielemental x-ray fluorescence method. The osprey from Clear Lake showed significantly elevated mercury concentrations relative to the comparison sites. Different species at Clear Lake had different mercury concentrations based on trophic status; osprey exhibited the highest mercury concentrations and the mallards showed the lowest. Lastly, we quantified differences in elemental concentrations, including mercury, between adult and juvenile osprey from Clear Lake. Elements known to be nutrients, such as sulfur and zinc, did not vary significantly among species or sites. Reproductive success of osprey at Clear Lake was monitored from 1992 to 1996 to determine if osprey reproduction was depressed. During this five-year period, the breeding population grew from 10 to 20 nesting pairs and the average reproductive rate was 1.4 fledglings per nesting attempt. Although the osprey showed the highest mercury levels of any species sampled, their reproduction does not appear to be depressed.

  7. Lake-Level Responses to Abrupt Climate Changes in North-Central Pennsylvania since >16 ka

    NASA Astrophysics Data System (ADS)

    Halstead, T. M.; Shuman, B. N.

    2016-12-01

    Water levels in small lakes and ponds have widely responded to late-Quaternary climate changes, and we use a combination of geophysical surveys and sediment cores to reconstruct the hydrologic history of Sunfish Pond near Leroy, Pennsylvania (41°38'N 76°41'W). The small lake sits atop Barclay Mountain, a narrow ridge of the Appalachian Mountains near the southern limit of the Wisconsin glaciation. Ground-penetrating radar (GPR) profiles and a transect of three sediment cores indicate that the shoreline position of the lake has shifted over time with sandy littoral sediments extending outward into the lake stratigraphy, which is primarily composed of organic-rich muds. Calibrated radiocarbon ages from a sediment core collected in 2.25 m of water indicate that the lake formed by ca. 16.1 ka. Deposition of organic-rich muds in the near-shore core indicates moderately high water levels during the period of Heinrich Event 1, the Younger Dryas, and portions of the early Holocene. Sand layers and exceptionally low sediment accumulation rates indicate low water, however, from <16-12.5 ka and again from 5.5-2.8 ka. The water level has been near its modern high level since 2.8 ka based on extensive deposition of rapidly accumulating, organic-rich muds across the basin. The changes coincide with major changes in regional pollen records, and confirm the hydrologic significance of late-Pleistocene abrupt events in the Mid-Atlantic region.

  8. Analysing the temporal water quality dynamics of Lake Basaka, Central Rift Valley of Ethiopia

    NASA Astrophysics Data System (ADS)

    Olumana Dinka, Megersa

    2017-01-01

    This study presents the general water quality status and temporal quality dynamics of Lake Basaka water in the past about 5 decades. Water samples were collected and analysed for important physico-chemical quality parameters following standard procedures. The result showed that Lake Basaka water is highly saline and alkaline and experiencing a general reducing trends in ionic concentrations of quality parameters due to the dilution effect. About 10-fold reduction of total ionic concentration occurred in the Lake over the period of 2 decades (1960-1980). There was a sharp and fast decline in EC, Cl, SO4, Na, and K ions from early 1960s up to the late 1980s, and then became relatively stable. Some ions (eg. Na, Ca, Mg, Cl, SO4) are showing increment in recent years. This characteristics of the lake water is terrible in relation to its potential to inundate the nearby areas in the near future. The expansion of such quality water has negative effects on the water resources of the region, especially soil quality, drainage and groundwater, in terms of salinity, sodicity and specific ion toxicity. The regimes of soil moisture, solute and groundwater could be affected, concurrently affecting the productivity and sustainability of the sugar estate. Thus, there is an urgent need to identify the potential sources of water and chemicals to the lake and devise an appropriate mitigation and/or remedial measures.

  9. Distribution and recent variations of supraglacial lakes on dendritic-type glaciers in the Khan Tengri-Tomur Mountains, Central Asia

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Mayer, C.; Liu, S.

    2013-12-01

    Supraglacial lakes are widely distributed on glaciers in the Tomur-Khan Tengri Tianshan Mountains, Central Asia. The existence and development of supraglacial lakes play an important role in the processes of ice melting and also in the storage and release of glacial runoff. Here we mapped the supraglacial lakes in the lower region of eight typical debris-covered dendritic-type glaciers around the Tomur-Khan Tengri peaks based on 9 Landsat TM/ETM+ images acquired in summers during 1990 and 2011. With a lower limit of 3600 m2 for the conservative identification of glacial lakes, we mapped 775 supraglacial lakes and 38 marginal glacial lakes in total. Our results indicate that supraglacial lakes in the study region are developed never beyond an elevation of about 3850 m a.s.l., 800 meter lower than the upper boundary of debris cover (4650 m a.s.l.). For the total area-elevation distribution, these lakes are prominently happened near the altitude of 3250 m a.s.l., where the clean ice is simultaneously vanished. The majority of the supraglacial lakes are found on the Tomur Glacier and the South Inylchek Glacier, two typical debris-covered dendritic-type glaciers in the region. As for the multi-year variation of lake area, the annual summer total and mean areas of supraglacial lakes show variability from 1990 and 2005 but expanded obviously during 2005 and 2011. The mean area of these lakes reached maximum in 2010. We found that the area of supraglacial lakes is positively correlated to the total precipitation in summer (July to September) but negatively to the mean air temperature over pre-summer (April to June). Air temperature fluctuations during the pre-summer likely have more impact on the different evolution proceedings of the development of glacial drainage from unconnected to connected systems, which may lead to the drainage of some larger supraglacial lakes and resulted in shrinkage of the total and mean lakes area over the summer seasons. Correlations between

  10. Present-day variability and Holocene dynamics of permafrost-affected lakes in central Yakutia (Eastern Siberia) inferred from diatom records

    NASA Astrophysics Data System (ADS)

    Pestryakova, Luidmila A.; Herzschuh, Ulrike; Wetterich, Sebastian; Ulrich, Mathias

    2012-09-01

    Thermokarst lakes are assumed to develop cyclically, driven by processes that are triggered by climate and maintained by internal feedbacks that may trigger lake drainage. However, the duration of these cycles remains uncertain, as well as whether or not they affect the stabilization of lake ecosystems in permafrost regions over millennial time scales. Our research has combined investigations into modern lake-to-lake variability with a study of the long-term development of individual lakes. We have investigated the physico-chemical and diatom compositions of a set of 101 lakes with a variety of different origins in central Yakutia (Eastern Siberia), including thermokarst lakes, fluvial-erosion thermokarst lakes, fluvial-erosion lakes, and dune lakes. We found a significant relationship between lake genesis and the present-day variability in environmental and diatom characteristics, as revealed by multi-response permutation procedures, indicator species analyses, and redundancy analyses. Environmental parameters also exhibit a significant correlation with variations in the diatom data, for which they may have been to a substantial extent responsible. Mg and SO4 concentrations, together with pH and water depth, were identified as the most important parameters, influencing the variations in the diatom data almost as much as the entire environmental parameter set. We were therefore able to establish a robust Mg-diatom transfer function, which was then applied to three Holocene lake records. From these reconstructions, together with a general interpretation of the diatom record (including, e.g., the ratio between benthic/epiphytic and planktonic taxa), we have been able to infer that all three of these lakes show (1) a continuous record with no desiccation events, (2) high lake water-levels during the early Holocene, (3) centennial to millennial scale variability, and (4) high levels of variability during the early Holocene but rather stable conditions during the late

  11. The effect of seasonality on the structure of rotifers in a black-water shallow lake in Central Amazonia.

    PubMed

    Nova, Clarice C; Lopes, Vanessa G; Souza, Leonardo Coimbra E; Kozlowsky-Suzuki, Betina; Pereira, Talita A A; Branco, Christina W C

    2014-09-01

    Rotifers have often been used as indicators of sudden changes in physical and chemical features of the aquatic environment. Such features vary greatly during flood pulse events in small lakes connected to major floodplains. However, few are the studies that investigate the consequences of the flood pulse in rotifer species composition, abundance, richness and diversity, especially in Amazonian lakes. We analyzed samples from a small blackwater lake of an "igarapé" connected permanently to the Negro river, in Central Amazonia. Samples were taken twice a year for two years, comprising flooding and receding periods of the flood pulse. Rotifer abundance increased significantly after draught events, and electrical conductivity and turbidity were intrinsically related to such variation. Species composition also changed from flooding to receding periods. Some taxa, such as Brachionus zahniseri reductus and Lecane remanei were restricted to receding periods, while Brachionus zahniseri, Brachionus gillardi and Lecane proiecta were only present during flooding. A shift in the composition of rotifer families was observed from one period to another, showing the effect of renewing waters of the flood pulse. These results suggest that the flood pulse acts as a driving force and stressing condition, considerably altering rotifer community dynamics, either changing species composition or decreasing abundance.

  12. Reconnaissance survey for lightweight and carbon tetrachloride extractable hydrocarbons in the central and eastern basins of Lake Erie: September 1978

    SciTech Connect

    Zapotosky, J.E.; White, W.S.

    1980-10-01

    A reconnaissance survey of the central and eastern basins of Lake Erie (22,240 km/sup 2/) was conducted from September 17 to 27, 1978. The survey provided baseline information on natural gas and oil losses from geologic formations, prior to any potential development of natural gas resources beneath the United States portion of the Lake. Lightweight hydrocarbons indicative of natural gas (methane, ethane, propane, isobutane, and n-butane) are introduced into the waters of Lake Erie by escape from geologic formations and by biological/photochemical processes. The geochemical exploration technique of hydrocarbon sniffing provided enough data to reveal significant distribution patterns, approximate concentrations, and potential sources. Twelve sites with elevated lightweight hydrocarbon concentrations had a composition similar to natural gas. In one area of natural gas input, data analysis suggested a potential negative effect of natural gas on phytoplanktonic metabolism (i.e., ethylene concentration). Samples taken for liquid hydrocarbon analysis (carbon tetrachloride extractable hydrocarbons) correlated best with biologically derived lightweight hydrocarbons.

  13. A link between North Atlantic cooling and dry events in the core SW monsoon region in Lonar Lake, central India

    NASA Astrophysics Data System (ADS)

    Menzel, Philip; Gaye, Birgit; Prasad, Sushma; Plessen, Birgit; Stebich, Martina; Anoop, Ambili; Riedel, Nils; Basavaiah, Nathani

    2014-05-01

    A sediment core from Lonar Lake in central India covers the complete Holocene and was used to reconstruct the monsoon history of the core SW-monsoon region. We compare C/N ratios, stable carbon and nitrogen isotopes, grain size, as well as amino acid derived degradation proxies with climatically sensitive proxies of other records from South Asia and the North Atlantic region. The comparison reveals some more or less contemporaneous climate shifts. At Lonar Lake, a general long term climate transition from wet conditions during the early Holocene to drier conditions during the late Holocene, delineating the insolation curve, can be reconstructed. Several phases of shorter term climate alteration that superimpose the general climate trend correlate with cold phases in the North Atlantic region. The most pronounced climate deteriorations indicated by our data occurred between 6.2 - 5.2, 4.65 - 3.9, and 2.05 - 0.55 cal ka BP. The strong dry phase between 4.65 - 3.9 cal ka BP at Lonar Lake corroborates the hypothesis that severe climate deterioration contributed to the decline of the Indus Civilisation about 3.9 ka BP.

  14. Fluctuating Eruption Style at Blue Lake Crater, Central Oregon Cascades: Insights from Deposit Granulometry and Componentry and Pyroclast Textures

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.

    2016-12-01

    Blue Lake crater in the central Oregon Cascades is one of the youngest Cascades volcanoes, erupting <3000 years ago. Based on the deep lake-filled crater excavated during the eruption, Blue Lake is commonly classified as a maar. However, little is known about this young eruption. This study focuses on mapping and detailed analyses of components and textures of the pyroclastic deposits to better understand changes in eruption style as the eruption progressed. Based on a new isopach map of the deposit thickness, the volume of erupted material is 4 x 107 m3. The deposits also suggest that the eruption was dominantly magmatic; phreatomagmatic surge deposits (<30 cm thick) occur locally at or near the base of the deposit but are overlain by much thicker scoria fall deposits. Detailed study of the pyroclasts from throughout the deposit reveal more subtle changes in the influence of external water over time. Granulometry from a complete deposit section (130 cm) reveals that the average grain size is finest immediately overlying the basal surge deposits and increases upsection. Componentry from this section shows that lithic and dense clasts are most abundant below and directly above the surges (near the deposit base) and decrease in abundance upsection, where vesicular scoria dominates. High magnification SEM BSE images of tephra clasts from throughout the deposit were obtained in order to better assess the changing role of external water during the eruption. Preliminary assessment of the images reveals that clasts from the eruption initiation have a glassier matrix compared to those upsection, which have a highly microcrystalline matrix, suggesting that early-erupted samples were likely quenched with external water. Taken together, these datasets suggest that the eruption initiated as dominantly phreatomagmatic but then rapidly transitioned to dominantly magmatic for the eruption duration. Further investigation of clast vesicularity and crystallinity will aid in

  15. Changing of dominant atmospheric circulation since LGM recorded by a lake core in the central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhu, L.; Wang, J.; Lu, X.; Daut, G.; Kasper, T.; Haberzettl, T.; Schwalb, A.; Maeusbacher, R.

    2013-12-01

    The mechanism of climate changes and some abrupt events on the Tibetan Plateau since LGM exists many uncertainties. Further understanding is possibly provided by a continue lake core records in the Nam Co (4718 asl, 2015 km2) on the central Tibetan Plateau. The 11m long core collected in 90m deep water area has a well age-depth distribution according to 32 14C dating data. 24-19 kaBP, higher Pediastrum suggested a shallow water condition. 19-16.5kaBP, decreased Pediastrum and Cyperaceae suggested water depth increasing and wetland reducing. Pinus, Picea and Abies were over than 30% during 24-16.5 kaBP, implying a different climate condition than it at present. 16.5-14.2 kaBP, humidity was enhanced according to Cyperaceae, Gramineae, Artemisia and Chenopodiacen. Pinus, Picea and Abies were less than 10%, suggesting climate shifted in lake area. 14.2-13.2 kaBP, Fe/Mn, Ca and Sr/Ba indicated water depth increase while total pollen concentration (TPC) and TOC (endogenesis source) reflected temperature rising. 13.2-11.5 kaBP, cold-dry climate was reflected by lake volume changing based upon Fe/Mn, Ca, Sr/Ba and Pediastrum, and the decreasing of TOC and TCP. 11.5-8.5 kaBP, a good water and heat condition was indicated by pollen assemblages and geochemistry, and the best period was within 10.2-9.3 kaBP. 8.5-5.8 kaBP, the best water-heat condition gradually weakened according to decreased TCP but stable TOC. After 5.8 kaBP, climate tended to be dry. In general, there were not only existed several climatic change events in the Nam Co lake area, but also occurred climatic type shifting since LGM.

  16. Peak-flow frequency and extreme flood potential for streams in the vicinity of the Highland Lakes, central Texas

    USGS Publications Warehouse

    Asquith, William H.; Slade, R.M.; Lanning-Rush, Jennifer

    1996-01-01

    The Highland Lakes on the Colorado River are in an area periodically threatened by large storms and floods. Many storms exceeding 10 inches (in.) in depth have been documented in the area, including some with depths approaching 40 in. These storms typically produce large peak discharges that often threaten lives and property. The storms sometimes occur with little warning. Steep stream slopes and thin soils characteristic of the area often cause large peak discharges and rapid movement of floods through watersheds. A procedure to predict the discharge associated with large floods is needed for the area so that appropriate peak discharges can be used in the design of flood plains, bridges, and other structures.The U.S. Geological Survey (USGS), in cooperation with the Lower Colorado River Authority (LCRA), studied flood peaks for streams in the vicinity of the Highland Lakes of central Texas. The Highland Lakes are a series of reservoirs constructed on the Colorado River. The chain of lakes (and year each was completed) comprises Lake Buchanan (1937), Inks Lake (1938), Lake Lyndon B. Johnson (1950), Lake Marble Falls (1951), Lake Travis (1942), and lake Austin (1890). The study area (fig. 1), which includes all or parts of 21 counties in the vicinity of the Highland Lakes, was selected because most streams in the area have flood characteristics similar to streams entering the Highland Lakes. The entire study area is in a region subject to large storms.The purpose of this report is to present (1) peak-flow frequency data for stations and equations to estimate peak-flow frequency for large streams with natural drainage basins in the vicinity of the Highland Lakes, and (2) a technique to estimate the extreme flood peak discharges for the large streams in the vicinity of the Highland Lakes. Peak-flow frequency in this report refers to the peak discharges for recurrence intervals of 2,5, 10,25,50, and 100 years. A large stream is defined as having a contributing drainage

  17. Possible effects on Lake Abert of a proposed impoundment on Chewaucan River, south-central Oregon

    USGS Publications Warehouse

    Van Denburgh, A.S.

    1975-01-01

    This statement is a response to questions raised by personnel of the U.S. Forest Service, Lakeview, Oregon, with respect to the possible effects on Lake Abert and its basin if the propos ed Coffeepot Reservoir is built on Chewaucan River. The responses are keyed to paragraphs in a letter of inquiry but are self-explanatory without reference to that letter.

  18. Isolation of Acholeplasma laidlawii from centrarchids in a Central Florida Lake

    USGS Publications Warehouse

    Francis-Floyd, R.; Reed, P.; Gibbs, P.; Shotts, E.; Bolon, B.; Coleman, W.; Klinger, R.

    1998-01-01

    In 1991, the poor physical condition of largemouth bass Micropterus salmoides from Lake Harris, Florida, was associated with the decline of the lake's fishery. The swim bladders of emaciated bass had mild inflammation and ecchymotic hemorrhages. A mycoplasma-like organism isolated from swim bladders was initially believed to be the causative agent. The organism was later identified as Acholeplasma laidlawii by using a fluorescent antibody procedure and was demonstrated to be nonpathogenic. Parenteral injection of the organism into healthy largemouth bass fingerlings produced no signs of disease or difference in growth rate compared with control fish during a 16-month period. Field studies resulted in isolation of A. laidlawii from black crappies Pomoxis nigromaculatus, bluegills Lepomis macrochirus, and redear sunfish L. microlophus, but not from noncentrarchids in Lake Harris or from any fish species in a control fishery (Lake Holly, Florida). The absence of organisms in all emaciated bass, our inability to reproduce the disease, and isolation of the organism from seemingly healthy fish suggest this organism was not pathogenic.

  19. Quantification of anthropogenic threats to lakes in a lowland county of central Sweden.

    PubMed

    Brunberg, A K; Blomqvist, P

    2001-05-01

    An evaluation of the negative effects caused by anthropogenic influence on lake ecosystems was performed, using data from 143 catchments in Uppsala County, Sweden. The study included i) technical encroachments; i.e. construction of dams, dikes, etc. as well as effects of drainage of land; ii) pollution, i.e. eutrophication, acidification, and contamination by toxic substances; iii) introduction of nonnative species; and iv) exploitation of species populations. Severe damage was caused mostly by drainage of land followed by pollution by toxic substances and, to a smaller extent, introduction of nonnative species and eutrophication. Most lakes were subject to several types of disturbances, interacting in a complex pattern, which made it difficult to link the visible effects to the true causes of the disturbance. Future lake management should include analyses of all disturbances to the lake catchments, taking into account the historical perspective, in order to balance the threats/damages, in an analysis of the possibilities for maintaining biodiversity and sustainability in the ecosystems.

  20. [Aquatic insects in dune lakes of the central region of the Gulf of Mexico].

    PubMed

    Peralta, Luis A; Deloya, Cuauhtémoc; Moreno-Casasola, Patricia

    2007-01-01

    The aim of this study is to register the presence of aquatic insects during the rainy and dry seasons, in 15 dune lakes of the Gulf of Mexico's coastal zone. These ecosystems lodge a wealth of 62 families, 60 of them present during the rainy season and 46 during the dry period. At both times Coleoptera is the order with a greater number of families, followed by Diptera. The first one is the most diverse, but Chironomidae (Diptera) is the most abundant, representing 40% of the total number of individuals. We used high rank taxa to quantify the biodiversity based on the principle that a high number of families or genus is supposed to include a greater number of species. There were not significant differences in the alpha diversity within the same lake during the two climatic seasons. The trophic structure is dominated by the detritivorous groups (57% of scrapers, collectors, gatherers, shredders), followed by predators (38%) and herbivores (5%). These numbers indicate that dune lakes have a great amount of organic matter. The results obtained contradict our working hypothesis, thus it was rejected, in summary, because there were no important differences in family composition, abundance of individuals and trophic structure of the lakes between the rainy and dry seasons.

  1. Seven thousand years of records on the mining and utilization of metals from lake sediments in central China.

    PubMed

    Lee, Celine S L; Qi, Shi-Hua; Zhang, Gan; Luo, Chun-Ling; Zhao, Lu Y L; Li, Xiang-Dong

    2008-07-01

    A 268 cm section of sediment core from Liangzhi Lake in Hubei province in central China was used to assess the use and accumulation of metals in the lake in the past 7,000 years. The concentrations of trace metals, including Cu, Pb, Ni, and Zn, and major elements, Ca, Fe, and Mg, in a 14C- dated segment of sediment core were analyzed. Historical trends on the input of metals to Liangzhi Lake from around 5000 BC to the present were recorded in the sediments, representing about 7,000 years of history on the mining and utilization of metals in central China. The concentrations of Cu, Ni, Pb, and Zn increased gradually from about 3000 +/- 328 BC, indicating the start of the Bronze Age in ancient China. During the period 467 +/- 257 to 215 +/- 221 AD, there was a rapid increase in the concentrations of these metals in the sediments, indicating enormous inputs of these metals at that time. This era corresponded to China's Warring States Period (475- 221 BC) and the early Han Dynasty (206 BC-220 AD), during which copper and lead were extensively used in making bronze articles such as vessels, tools, and weapons. From 1880 +/- 35 AD to the early 1900s, there was also a significant increase in the concentrations of metals such as Cu, Ni, and Pb, which probably reflected the metal emissions and utilization during the early period of industrial development and weapon manufacture during the wars in China. The Pb isotopic analysis showed that the surface and subsurface sediments had lower 206Pb/207Pb and 208Pb/ 207Pb ratios than the deeper layers, reflecting the additional input of Pb from mining activities that took place during the Bronze Age era and in modern times. This study provides direct evidence of the environmental impact of the mining and utilization of metals in the last 7,000 years in one of the important regions of Chinese civilization.

  2. Detailed study of selenium in soil, water, bottom sediment, and biota in the Sun River Irrigation Project, Freezout Lake Wildlife Management Area, and Benton Lake National Wildlife Refuge, west-central Montana, 1990-92

    USGS Publications Warehouse

    Nimick, D.A.; Lambing, J.H.; Palawski, D.U.; Malloy, J.C.

    1996-01-01

    Selenium and other constituents are adversely affecting water quality and creating a potential hazard to wildlife in several areas of the Sun River Irrigation Project, Freezout Lake Wildlife Management Area, and Benton Lake National Wildlife Refuge in west-central Montana. Selenium derived from Cretaceous shale and Tertiary and Quaternary deposits containing shale detritus is transported in the oxic shallow ground-water systems. At Freezout Lake Wildlife Management Area, drainage from irrigated glacial deposits is the primary source of selenium; drainage from non-irrigated farmland is a significant source locally. Benton Lake generally receives more selenium from natural runoff from its non-irrigated basin than from the trans-basin diversion of irrigation return flow. Selenium has accumulated in aquatic plants and invertebrates, fish, and water birds, particularly in wetlands that receive the largest selenium loads. Although selenium residues in biological tissue from some wetland units exceeded biological risk levels, water-bird reproduction generally has not been impaired. The highest selenium residues in biota commonly occurred in samples from Priest Butte Lakes, which also had the highest selenium concentration in wetland water. Selenium concentrations in all invertebrate samples from Priest Butte Lakes and the south end of Freezeout Lake exceeded the critical dietary threshold for water birds. Selenium delivered to wetlands accumulates in bottom sediment, predominantly in near-shore areas. Potential impacts to water quality, and presumably biota, may be greatest near the mouths of inflows. Most selenium delivered to wetlands will continue to accumulate in bottom sediment and biota.

  3. Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the North Canadian River from Canton Lake to Lake Overholser in Central Oklahoma

    USGS Publications Warehouse

    Adams, G.P.; Rea, Alan; Runkle, D.L.

    1997-01-01

    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 alluvial and terrace deposits along the North Canadian River from Canton Lake to Lake Overholser in central Oklahoma. Ground water in approximately 400 square miles of Quaternary-age alluvial and terrace aquifer is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer consists of clay, silt, sand, and gravel. Sand-sized sediments dominate the poorly sorted, fine to coarse, unconsolidated quartz grains in the aquifer. The hydraulically connected alluvial and terrace deposits unconformably overlie Permian-age formations. The aquifer is overlain by a layer of wind-blown sand in parts of the area. Most of the lines in the aquifer boundary, hydraulic conductivity, and recharge data sets were extracted from published digital surficial geology data sets based on a scale of 1:250,000. The ground-water elevation contours and some of the lines for the aquifer boundary, hydraulic conductivity, and recharge data sets were digitized from a ground-water modeling report about the aquifer published at a scale of 1:250,000. The hydraulic conductivity values and recharge rates also are from the ground-water modeling report. 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.

  4. Distribution and recent variations of supraglacial lakes on dendritic-type glaciers in the Khan Tengri-Tomur Mountains, Central Asia

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Mayer, C.; Liu, S.

    2013-09-01

    Supraglacial lakes are widely distributed on glaciers in the Tomur-Khan Tengri Tianshan Mountains, Central Asia. The existence and development of supraglacial lakes play an important role in the ice melting processes and also in the storage and release of glacial melt water. Here we mapped the supraglacial lakes of eight typical debris-covered dendritic-type glaciers around the Tomur-Khan Tengri peaks based on 9 Landsat TM/ETM+ images acquired in the summers of 1990 until 2011. With a lower area limit of 3600 m2 for a conservative identification of glacial lakes, we mapped 775 supraglacial lakes and 38 marginal glacial lakes in total. Our results indicate that supraglacial lakes (area > 3600 m2) in the study region never develop beyond an elevation of about 3850 m a.s.l., 800 m lower than the maximum upper boundary of debris cover (4650 m a.s.l.). The area-elevation distribution shows that lakes are predominantly occured close to the altitude of 3250 m a.s.l., where the clean ice simultaneously disappears. The majority of the supraglacial lakes are found on the Tomur Glacier and the South Inylchek Glacier, two strongly debris-covered dendritic-type glaciers in the region. As for the multi-year variation of lake area, the summer total and mean areas of supraglacial lakes show some variability from 1990 and 2005 but increased noticeably between 2005 and 2011. The mean area of the mapped lakes reached a maximum in 2010. We found that the area of supraglacial lakes is positively correlated to the total precipitation in summer (July to September) but negatively correlated to the mean spring air temperature (April to June). Pre-summer air temperature fluctuations likely have a stronger impact on the different evolution processes of glacial drainage, evolving from unconnected to connected systems, which may lead to the drainage of larger supraglacial lakes and results in shrinkage of the total and mean lake area during the summer.

  5. The history of paleoenvironmental change and its cyclic change during the Common Era in the Lake Hiruga, Fukui Prefecture, central Japan

    NASA Astrophysics Data System (ADS)

    Seto, K.; Irisawa, S.; Kitagawa, J.; Katsuki, K.; Yamada, K.

    2016-12-01

    Lake Hiruga, is one of the Five Lakes of Mikata, is a small lake of less than 1 km2, which is located in the Japan Sea side of central Japan. This lake is in contact with the Japan Sea by Hiruga channel, and with Lake Suigetsu by artificial Saga Tunnel. Although the salinity of lake water is close to the seawater, the bottom water shows the low water temperature (about 10°C) in the summer season, and shows the constantly anoxic environments, because the water depth of lake basin is deep (about 38m). In order to clarify the history of paleoenvironmental change at the Lake Hiruga, the coring was carried out around the center of lake. In this time, we report on the result of the analysis for 15HG-2C and 3C cores. 15HG-2C and 3C cores consist of mud sediments with the lamination at the integrated core length of 251cm. The distinct lamina (probably varve) is observed from core top to 50cm in core depth. AMS14C dating is carried out in 4 horizons. Based on the results, the age of core bottom is about 3300 years ago. Lake Hiruga was a freshwater lake until AD150, and changed to oligohaline lake from that time. Around the 10th century, the bottom water of this lake became to mixoeuhaline water. Judging from the bottom water exhibits a euxinic environment, it might have had a distinct stratified structure in water column. This change is considered to be due to the opening of Hiruga channel with the development of paddy fields at that time. From the 19th century, the lake basin shows high sedimentation rate, and varve is formed. It is considered that this is caused by the construction of the Saga tunnel. During the last 200 years, the 5 cyclic fluctuation of total organic carbon (TOC) contents, and the 10 cyclic fluctuation of total sulfur (TS) contents were recognized. It is considered that the cyclic fluctuation of TS contents is caused by different level of reduced environment due to differences in inflow of seawater with cyclic sea-level change. The 5 cyclic fluctuation

  6. Holocene climate variability in arid Central Asia as revealed from high-resolution sedimentological and geochemical analyses of laminated sediments from Lake Chatyr Kol (Central Tian Shan, Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Lauterbach, S.; Plessen, B.; Dulski, P.; Mingram, J.; Prasad, S.

    2013-12-01

    A pronounced trend from a predominantly wet climate during the early Holocene towards significantly drier conditions since the mid-Holocene, mainly attributed to the weakening of the Asian summer monsoon (ASM), is documented in numerous palaeoclimate records from the monsoon-influenced parts of Asia, e.g. the Tibetan Plateau and north- and southeastern China. In contrast, climate in the adjacent regions of mid-latitude arid Central Asia, located north and northwest of the Tibetan Plateau, is supposed to have been characterized by pronounced dry conditions during the early Holocene, wet conditions during the mid-Holocene and a rather moderate drying during the late Holocene, which is mainly attributed to the complex interplay between the mid-latitude Westerlies and the ASM. However, although mid-latitude Central Asia thus might represent a key region for the understanding of teleconnections between the ASM system and the Westerlies, knowledge about past climate development in this region is still ambiguous due to the limited number of high-resolution palaeoclimate records. Hence, new well-dated and highly resolved palaeoclimate records from this region are expected to provide important information about spatio-temporal changes in the regional interplay between Westerlies and ASM and thus aid the understanding of global climate teleconnections. As a part of the project CADY (Central Asian Climate Dynamics), aiming at reconstructing past climatic and hydrological variability in Central Asia, a sediment core of about 6.25 m length has been recovered from alpine Lake Chatyr Kol (40°36' N, 75°14' E, 3530 m a. s. l., surface area ~170 km2, maximum depth ~20 m), located in the Central Tian Shan of Kyrgyzstan. Sediment microfacies analysis on large-scale petrographic thin sections reveals continuously sub-mm scale laminated sediments throughout the record except for the uppermost ca. 60 cm. Microsedimentological characterization of these laminae, which are most probably

  7. Aqueous Geochemistry of Lake Tuscaloosa, West-Central Alabama, USA: Drought Response

    NASA Astrophysics Data System (ADS)

    Creech, L., Jr.; Donahoe, R. J.

    2008-12-01

    Lake Tuscaloosa was created in 1969 by the impoundment of the North River near Northport and Tuscaloosa, AL. The reservoir is 25 miles long with a capacity of 123,000 acre-feet, a surface area of 5,885 acres, and an estimated safe yield of 200 M gal/d. It is the receiving water body of a 432 square mile watershed. This project studies the aqueous geochemistry of surface waters using samples representative of different seasonal conditions and land cover. Of the 21 sample locations in this study, three are located on tributaries, four transect the axis of the lake, and the rest are divided among semi-restricted coves representing forested and residential land cover. Sample chemistry is quantified for major, minor, and trace cations, anions, and nutrients, total dissolved nitrogen, DOC, and ALK. The current study presents data collected from the lake and its tributaries during recent severe drought conditions impacting much of the southeastern United States. These data are compared with data from an identical study conducted five years ago during a more normal water year. For each sampling year, four seasonal sampling events were conducted. Both intra- and inter-annual results are reported. Historical USGS data for seven locations sampled since 1986 on a semi-annual basis illustrate a general increase in TDS and nutrients since the lake's creation. Some USGS sample locations coincide with those of the current study. Recently collected data agrees well with recent USGS data for the same locations. It is likely that trends observed in this study are related to anthropogenic effects along the lake shore, as evidenced by the geochemical differences between residential and forested coves. Long-term trends observed in historical data are likely the result of land use in the watershed related to mining, agriculture, and residential development. It is also observed that lower flow conditions are associated with increased solute concentrations, indicating that dilution by

  8. Late Early Permian continental ichnofauna from Lake Kemp, north-central Texas, USA

    USGS Publications Warehouse

    Lucas, S.G.; Voigt, S.; Lerner, A.J.; Nelson, W.J.

    2011-01-01

    Continental trace fossils of Early Permian age are well known in the western United States from Wolfcampian (~. Asselian to Artinskian) strata, but few examples are known from Leonardian (~. Kungurian) deposits. A substantial ichnofauna from strata of the lower part of the Clear Fork Formation at Lake Kemp, Baylor County, Texas, augments the meager North American record of Leonardian continental trace fossil assemblages. Ichnofossils at Lake Kemp occur in the informally-named Craddock dolomite member of the Clear Fork Formation, which is 12-15. m above the local base of the Clear Fork. The trace-bearing stratum is an up-to-0.3. m thick, laminated to flaser-bedded, dolomitic siltstone that also contains mud cracks, raindrop impressions, microbially induced mat structures, and some land-plant impressions. We interpret the Craddock dolomite member as the feather-edge of a marine transgressive carbonate deposit of an irregular coastline marked by shallow bays or estuaries on the eastern shelf of the Midland basin, and the trace-fossil-bearing stratum at Lake Kemp is an unchannelized flow deposit on a muddy coastal plain. The fossil site at Lake Kemp yields a low to moderately diverse fauna of invertebrate and vertebrate traces. A sparse invertebrate ichnofauna consists of arthropod feeding and locomotion traces assigned to Walpia cf. W. hermitensis White, 1929 and Diplichnites gouldi Gevers in Gevers et al., 1971. Tetrapod footprints are most common and assigned to Batrachichnus salamandroides (Geinitz, 1861), cf. Amphisauropus kablikae (Geinitz and Deichm??ller, 1882), and Dromopus lacertoides (Geinitz, 1861), which represent small temnospondyl, seymouriamorph, and basal sauropsid trackmakers. Both the traces and sedimentary features of the fossil horizon indicate a freshwater setting at the time of track formation, and the trace assemblage represents the Scoyenia ichnofacies and the Batrachichnus ichnofacies in an overbank environment with sheet flooding and shallow

  9. Phylogeny of the Lake Tanganyika cichlid species flock and its relationship to the Central and East African haplochromine cichlid fish faunas.

    PubMed

    Salzburger, Walter; Meyer, Axel; Baric, Sanja; Verheyen, Erik; Sturmbauer, Christian

    2002-02-01

    Lake Tanganyika, the oldest of the East African Great Lakes, harbors the ecologically, morphologically, and behaviorally most complex of all assemblages of cichlid fishes, consisting of about 200 described species. The evolutionary old age of the cichlid assemblage, its extreme degree of morphological differentiation, the lack of species with intermediate morphologies, and the rapidity of lineage formation have made evolutionary reconstruction difficult. The number and origin of seeding lineages, particularly the possible contribution of riverine haplochromine cichlids to endemic lacustrine lineages, remains unclear. Our phylogenetic analyses, based on mitochondrial DNA sequences of three gene segments of 49 species (25% of all described species, up to 2,400 bp each), yield robust phylogenies that provide new insights into the Lake Tanganyika adaptive radiation as well as into the origin of the Central- and East-African haplochromine faunas. Our data suggest that eight ancient African lineages may have seeded the Tanganyikan cichlid radiation. One of these seeding lineages, probably comprising substrate spawning Lamprologus-like species, diversified into six lineages that evolved mouthbrooding during the initial stage of the radiation. All analyzed haplochromines from surrounding rivers and lakes seem to have evolved within the radiating Tanganyikan lineages. Thus, our findings contradict the current hypothesis that ancestral riverine haplochromines colonized Lake Tanganyika to give rise to at least part of its spectacular endemic cichlid species assemblage. Instead, the early phases of the Tanganyikan radiation affected Central and East African rivers and lakes. The haplochromines may have evolved in the Tanganyikan basin before the lake became a hydrologically and ecologically closed system and then secondarily colonized surrounding rivers. Apparently, therefore, the current diversity of Central and East African haplochromines represents a relatively young and

  10. Cyanobacteria biennal dynamic in a volcanic mesotrophic lake in central Italy: Strategies to prevent dangerous human exposures to cyanotoxins.

    PubMed

    Manganelli, Maura; Stefanelli, Mara; Vichi, Susanna; Andreani, Paolo; Nascetti, Giuseppe; Scialanca, Fabrizio; Scardala, Simona; Testai, Emanuela; Funari, Enzo

    2016-06-01

    Vico Lake, a volcanic meso-eutrophic lake in Central Italy, whose water is used for drinking and recreational activities, experienced the presence of the microcystins (MC) producing cyanobacterium Planktothrix rubescens. In order to assess the human health risks and to provide the local health authorities with a scientific basis for planning tailored monitoring activities, we studied P. rubescens ecology and toxicity for two years. P. rubescens generally dominated the phytoplankton community, alternating with Limnothrix redekei, potentially toxic. P. rubescens was distributed throughout the water column during winter; in summer it produced intense blooms where drinking water is collected (-20 m); here MC were detected all year round (0.5-5 μg/L), with implications for drinking water quality. In surface waters, MC posed no risk for recreational activities in summer, while in winter surface blooms and foams (containing up to 56 μg MC/L) can represent a risk for people and children practicing water sports and for animals consuming raw water. Total phosphorus, phosphate and inorganic nitrogen were not relevant to predict densities nor toxicity; however, a strong correlation between P. rubescens density and aminopeptidase ectoenzymatic activity, an enzyme involved in protein degradation, suggested a role of organic nitrogen for this species. The fraction of potentially toxic population, determined both as mcyB(+)/16SrDNA (10-100%) and as the MC/mcyB(+) cells (0.03-0.79 pg MC/cell), was much more variable than usually observed for P. rubescens. Differently from other Italian and European lakes, the correlation between cell density or the mcyB(+) cells and MC explained only ∼50 and 30% of MC variability, respectively: for Vico Lake, monitoring only cell or the mcyB(+) cell density is not sufficient to predict MC concentrations, and consequently to protect population health. Finally, during a winter bloom one site has been sampled weekly, showing that

  11. Differences in the water-balance components of four lakes in the southern-central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Biskop, S.; Maussion, F.; Krause, P.; Fink, M.

    2016-01-01

    The contrasting patterns of lake-level fluctuations across the Tibetan Plateau (TP) are indicators of differences in the water balance over the TP. However, little is known about the key hydrological factors controlling this variability. The purpose of this study is to contribute to a more quantitative understanding of these factors for four selected lakes in the southern-central part of the TP: Nam Co and Tangra Yumco (increasing water levels), and Mapam Yumco and Paiku Co (stable or slightly decreasing water levels). We present the results of an integrated approach combining hydrological modeling, atmospheric-model output and remote-sensing data. The J2000g hydrological model was adapted and extended according to the specific characteristics of closed-lake basins on the TP and driven with High Asia Refined analysis (HAR) data at 10 km resolution for the period 2001-2010. Differences in the mean annual water balances among the four basins are primarily related to higher precipitation totals and attributed runoff generation in the Nam Co and Tangra Yumco basins. Precipitation and associated runoff are the main driving forces for inter-annual lake variations. The glacier-meltwater contribution to the total basin runoff volume (between 14 and 30 % averaged over the 10-year period) plays a less important role compared to runoff generation from rainfall and snowmelt in non-glacierized land areas. Nevertheless, using a hypothetical ice-free scenario in the hydrological model, we indicate that ice-melt water constitutes an important water-supply component for Mapam Yumco and Paiku Co, in order to maintain a state close to equilibrium, whereas the water balance in the Nam Co and Tangra Yumco basins remains positive under ice-free conditions. These results highlight the benefits of linking hydrological modeling with atmospheric-model output and satellite-derived data, and the presented approach can be readily transferred to other data-scarce closed lake basins, opening new

  12. Kame deltas provide evidence for a new glacial lake and suggest early glacial retreat from central Lower Michigan, USA

    NASA Astrophysics Data System (ADS)

    Schaetzl, Randall J.; Lepper, Kenneth; Thomas, Sarah E.; Grove, Leslie; Treiber, Emma; Farmer, Alison; Fillmore, Austin; Lee, Jordan; Dickerson, Bethany; Alme, Kayleigh

    2017-03-01

    In association with an undergraduate Honors Seminar at Michigan State University, we studied two small kame deltas in north-central Lower Michigan. These recently identified deltas provide clear evidence for a previously unknown proglacial lake (Glacial Lake Roscommon) in this large basin located in an interlobate upland. Our first goal was to document and characterize the geomorphology of these deltas. Because both deltas are tied to ice-contact ridges that mark the former position of the retreating ice margin within the lake, our second goal was to establish the age of one of the deltas, thereby constraining the timing of ice retreat in this part of Michigan, for which little information currently exists. Both deltas are composed of well-sorted fine and medium sands with little gravel, and have broad, nearly flat surfaces and comparatively steep fronts. Samples taken from the upper 1.5 m of the deltas show little spatial variation in texture, aside from a general fining toward their outer margins. Gullies on the outer margins of both deltas probably postdate the formation of the deltas proper; we suggest that they formed by runoff during a permafrost period, subsequent to lake drawdown. We named the ice lobe that once covered this area the Mackinac Lobe, because it had likely advanced into the region across the Mackinac Straits area. Five of six optically stimulated luminescence (OSL) ages from one of the deltas had minimal scatter and were within ± 1000 years of one another, with a mean age of 23.1 ± 0.4 ka. These ages suggest that the Mackinac Lobe had started to retreat from the region considerably earlier than previously thought, even while ice was near its maximum extent in Illinois and Indiana, and the remainder of Michigan was ice-covered. This early retreat, which appears to coincide with a short-lived warm period indicated from the Greenland ice core, formed an "opening" that was at least occasionally flooded. Thick and deep, fine-textured deposits

  13. Chemical composition and trophic state of shallow saline steppe lakes in central Asia (North Kazakhstan).

    PubMed

    Boros, Emil; Jurecska, Laura; Tatár, Enikő; Vörös, Lajos; Kolpakova, Marina

    2017-10-09

    The purpose of this study was to identify the prevailing chemical composition and trophic state of the shallow saline steppe lakes of North Kazakhstan along a wide size range (< 1-454 km(2)) and salinity gradient (2-322 g L(-1)) on a large spatial scale (1000 km), taking into account the potential effects of human disturbances. Water depth, Secchi disk transparency, temperature, pH, electric conductivity, major ions, total dissolved solids, total organic carbon, total nitrogen and phosphorus, nitrate, soluble reactive phosphorus, and chlorophyll a were measured. The equivalent percentage of major ions, Spearman rank correlation, multivariate analyses, equilibrium state of lakes, and spatial GIS autocorrelation were calculated. The impact of human disturbances (settlements, farms, and mines) on total organic carbon, nitrogen, phosphorus, and chlorophyll a were tested by Kruskal-Wallis ANOVA. The most common combinations of dominant ions were Na-Cl>SO4 and Na-Cl (n = 16; 64%); the Ca, Mg, HCO3, and SO4 ions precipitate with increasing salinity (2-322 g L(-1)); and ion composition shifts from Na>Mg-Cl>SO4 to Na-Cl. The most of the chemical variables positively, but chlorophyll a negatively, correlated with total dissolved solids, and the total phosphorus had no significant correlation with any variables. The trophic state of these lakes in most cases exceeded the hypertrophic level. The increase in salinity causes change in chemical composition and effects on the phytoplankton development independently from the size of water surface, and the human disturbances had negligible effect on the trophic state of shallow saline lakes in this region of Kazakhstan.

  14. [Relationships between urbanization and water resource utilization in Dongting Lake District of South-central China].

    PubMed

    Li, Jing-Zhi; Zhu, Xiang; Li, Jing-Bao; Xu, Mei

    2013-06-01

    By using analytic hierarchy process and entropy method, the evaluation index system and the response relationship model of comprehensive development level of urbanization and comprehensive development and utilization potential of water resources in Dongting Lake District were constructed, with the key affecting factors, their change characteristics, and response characteristics from 2001 to 2010 analyzed. During the study period, the Dongting Lake District was undergoing a rapid development of urbanization, and at a scale expansion stage. The economic and social development level was lagged behind the population and area increase, and the quality and efficiency of urbanization were still needed to be improved. With the advance of urbanization, the water consumption increased yearly, and the water resources utilization efficiency and management level improved steadily. However, the background condition of water resources and their development and utilization level were more affected by hydrological environment rather than urbanization. To a certain extent, the development of urbanization in 2001, 2002, 2005, 2006, 2007, 2009 was slowed down by the shortage of water resources. At present, Dongting Lake region was confronted with the dual task of improving the level and quality of urbanization, and hence, it would be necessary to reform the traditional epitaxial expansion of urbanization and to enhance the water resource support capability.

  15. Iron Isotopes in Lake Pavin (French Massif Central): A Window to the Precambrian Ocean

    NASA Astrophysics Data System (ADS)

    Busigny, V.; Jézéquel, D.; Louvat, P.; Viollier, E.; Michard, G.

    2008-12-01

    Consequences and timing of ocean oxygenation are still debated. It is generally considered that early ocean was anoxic and passed through a stratified state (oxic at the surface and anoxic in the deeper part) before being completely oxidized. Stratified ocean may have persisted more than 1Ga, thus representing an important period of the Earth history. The Fe isotope record in Precambrian sediments may provide constraints on the ocean evolution but a major question is what do the rocks tell us about the water column? This is an indirect way to get information and the geochemical signal may be modified later by diagenesis and metamorphism. The study of present stratified water body associated with sediments may help to decipher the isotopic signal from old sediments. Unlike marine complex environments, smaller and well-defined ecosystems such as lake can be useful to understand element transfer and processes. Lake Pavin is characterized by the presence of two stratified layers. The upper layer (mixolimnion) extends from the surface to 60m depth, and is oxidized. The deeper layer (monimolimnion), which extends from 70 to 92m depth, is permanently anoxic and separated from the mixolimnion by the mesolimnion where a drastic dissolved Fe gradient exists. In lake Pavin, Fe is oxidized and precipitated as Fe(III) in the mixolimnion. It is then dissolved in the deep layers (60 to 92m) and within the sediments and accumulates as aqueous Fe(II). Fe(II) either diffuses towards the mixolimnion or reacts with sulfides or phosphates to form FeS colloids and secondary minerals such as pyrite, vivianite or siderite. In order to characterize Fe isotope fractionations in this system, we measured Fe content and isotopic composition of aqueous Fe(II) along a vertical profile at different depths from the oxic-anoxic interface to the bottom of the lake. Fe content increases with depth, from less than 2 μmol/L above 60m depth to more than 1200 μmol/L at the bottom of the lake. δ56Fe

  16. Geothermal Flux, Basal Melt Rates, and Subglacial Lakes in Central East Antarctica

    NASA Astrophysics Data System (ADS)

    Carter, S. P.; Blankenship, D. D.; Morse, D. L.

    2002-12-01

    The lakes beneath the East Antarctic ice sheet represent a unique environment on Earth, entirely untouched by human interference. Life forms which survive in this cold, lightless, high pressure environment may resemble the life forms which survived through "snowball earth" and evolved into the life forms we know today (Kirchvink, 2000). Recent airborne radar surveys over Dome C and the South Pole regions allow us to assess where these lakes are most likely to exist and infer melting and freezing rates at base of the ice sheet. Lakes appear as strong, flat basal reflectors in airborne radar sounding data. In order to determine the absolute strength of the reflector it is important to accurately estimate signal loss due to absorption by the ice. As this quantity is temperature sensitive, especially in regions where liquid water is likely to exist, we have developed a one dimensional heat transfer model, incorporating surface temperature, accumulation, ice sheet thickness, and geothermal flux. Of the four quantities used for our temperature model, geothermal flux has usually proven to be the most difficult to asses, due to logistical difficulties. A technique developed by Fahnestock et al 2001 is showing promise for inferring geothermal flux, with airborne radar data. This technique assumes that internal reflectors, which result from varying electrical properties within the ice column, can be approximated as constant time horizons. Using ice core data from our study area, we can place dates upon these internal layers and develop an age versus depth relationship for the surveyed region, with margin of error of +- 50 m for each selected layer. Knowing this relationship allows us to infer the vertical strain response of the ice to the stress of vertical loading by snow accumulation. When ice is frozen to the bed the deeper ice will accommodate the increased stress of by deforming and thinning (Patterson 1994). This thinning of deeper layers occurs throughout most of our

  17. Distribution and interannual variability of supraglacial lakes on debris-covered glaciers in the Khan Tengri-Tumor Mountains, Central Asia

    NASA Astrophysics Data System (ADS)

    Qiao, Liu; Mayer, Christoph; Liu, Shiyin

    2015-01-01

    Supraglacial lakes are widely formed on debris-covered glaciers in the Khan Tengri-Tumor Mountains (KTTM), Tianshan, Central Asia. Study of their distribution characters based on regional-wide remote sensing investigations is still lacking, but it can promote our understanding about the influence of supraglacial lakes on the surface melting, hydrology and dynamics of debris-covered glaciers in this region. This study presents results of the supraglacial lake inventory in the KTTM region, based on multi-year Landsat images. We focus on the glacio-geomorphological characters of the supraglacial lakes and their late summer conditions, since all suitable Landsat images were acquired between August and September during 1990-2011. With a minimum threshold extent of 3600 m2 for conservative mapping results, we totally mapped 775 supraglacial lakes and 38 marginal glacial lakes on eight huge debris-covered glaciers. Supraglacial lakes are concentrated on the Tumor Glacier and the South Inylchek Glacier, two biggest glaciers in this region. Although most supraglacial lakes are short-lived, a number of lakes can be repeatedly identified between different Landsat images. Detailed investigation of these ‘perennial’ lakes on the Tumor Glacier indicates that their filling frequency and area contributions have increased since 2005. Analysis of the area-elevation distributions for all mapped supraglacial lakes shows that they predominantly occur close to the altitude of 3250 m a.s.l., as high as the lowest reach of clean ice where surface debris begins to appear, and can further develop upglacier to a limit of about 3950 m a.s.l.. Total and mean area of supraglacial lakes in the KTTM region during the late summer seasons show great variability between years. Correlation analysis between the annual lake area and the observed nearby meteorological conditions suggests that warmer springs seem related to the draining of some supraglacial lakes during the following seasons, due to

  18. Hydrogeologic comparison of an acidic-lake basin with a neutral-lake basin in the West-Central Adirondack Mountains, New York

    USGS Publications Warehouse

    Peters, N.E.; Murdoch, Peter S.

    1985-01-01

    Two small headwater lake basins that receive similar amounts of acidic atmospheric deposition have significantly different lake outflow pH values; pH at Panther Lake (neutral) ranges from about 4.7 to 7; that at Woods Lake (acidic) ranges from about 4.3 to 5. A hydrologic analysis, which included monthly water budgets, hydrograph analysis, examination of flow duration and runoff recession curves, calculation of ground-water storage, and an analysis of lateral flow capacity of the soil, indicates that differences in lakewater pH can be attributed to differences in the ground-water contribution to the lakes. A larger percentage of the water discharged from the neutral lake is derived from ground water than that from the acidic lake. Ground water has a higher pH resulting from a sufficiently long residence time for neutralizing chemical reactions to occur with the till. The difference in ground-water contribution is attributed to a more extensive distribution of thick till (<3m) in the neutral-lake basin than in the acidic-lake basin; average thickness of till in the neutral-lake basin is 24m whereas that in the other is 2.3m. During the snowmelt period, as much as three months of accumulated precipitation may be released within two weeks causing the lateral flow capacity of the deeper mineral soil to be exceeded in the neutral-lake basin. This excess water moves over and through the shallow acidic soil horizons and causes the lakewater pH to decrease during snowmelt.Two small headwater lake basins that receive similar amounts of acidic atmospheric deposition have significantly different lake outflow pH values; pH at Panther Lake (neutral) ranges from about 4. 7 to 7; that at Woods Lake (acidic) ranges from about 4. 3 to 5. A hydrologic analysis, which included monthly water budgets, hydrograph analysis, examination of flow duration and runoff recession curves, calculation of ground-water storage, and an analysis of lateral flow capacity of the soil, indicates that

  19. A digital model for planning water management at Benton Lake National Wildlife Refuge, west-central Montana

    USGS Publications Warehouse

    Nimick, David A.; McCarthy, Peter M.; Fields, Vanessa

    2011-01-01

    Benton Lake National Wildlife Refuge is an important area for waterfowl production and migratory stopover in west-central Montana. Eight wetland units covering about 5,600 acres are the essential features of the refuge. Water availability for the wetland units can be uncertain owing to the large natural variations in precipitation and runoff and the high cost of pumping supplemental water. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, has developed a digital model for planning water management. The model can simulate strategies for water transfers among the eight wetland units and account for variability in runoff and pumped water. This report describes this digital model, which uses a water-accounting spreadsheet to track inputs and outputs to each of the wetland units of Benton Lake National Wildlife Refuge. Inputs to the model include (1) monthly values for precipitation, pumped water, runoff, and evaporation; (2) water-level/capacity data for each wetland unit; and (3) the pan-evaporation coefficient. Outputs include monthly water volume and flooded surface area for each unit for as many as 5 consecutive years. The digital model was calibrated by comparing simulated and historical measured water volumes for specific test years.

  20. Active Growing of Siliceous Stromatolites in the Lake Specchio di Venere, Pantelleria Island, Central Mediterranean

    NASA Astrophysics Data System (ADS)

    Cangemi, M.; Bellanca, A.; Neri, R.; Hopkinson, L.

    2009-05-01

    Stromatolites are laminated organosedimentary structures produced by mediation of microbial communities that constitute a peculiar coupled geo-biosphere system. These deposits represent the earliest macroscopic evidence of life in the fossil record and contain potentially important palaeoenvironmental and biologic information. Stromatolites are not necessarily carbonatic but, even if more rarely, can be siliceous and evaporitic. Occurrences of siliceous stromatolites are mostly associated to geothermal fields in Iceland, Yellowstone, New Zealand and Kenya. This research reports the discovery of siliceous stromatolites actively growing in the lake Specchio di Venere (Pantelleria Island, Sicily), an endorheic saline lake within a calderic depression. At present, volcanic activity in the island is limited to low temperature fumarolic emissions and to thermal springs characterized by temperatures up to 90°C. The stromatolites were found in a scenario of very shallow waters and pools, close to small CO2 vents. The presence of living microbial communities is highlighted by different layers (microbial mats) ranging in colour from orange-red to green to reddish-brown, at the top, middle, and bottom, respectively, of stromatolites. The present work shows preliminary results obtained by petrographic (polarizing microscope and SEM), mineralogical (X-Ray diffractometry, Fourier Transfom Infrared, Fourier Transform Raman) and geochemical investigations of the Specchio di Venere lake stromatolites. Detailed observations under the microscope and SEM highlight the presence of biofilm, microbial filaments and silica spheres organized in alveolar structures. IR and Raman analyses point out the presence of different SiO2 mineralogical phases in the sedimentary layers related to an increasing maturation of silica. The REE patterns of these samples identify a typical enrichment in HREE, in the region Tm-Yb-Lu, probably linked to microbial activity.

  1. Biotic and abiotic response to palaeoenvironmental changes at Lake Pannons' western margin (Central Europe, Late Miocene)

    PubMed Central

    Gross, Martin; Piller, Werner E.; Scholger, Robert; Gitter, Frank

    2011-01-01

    A multidisciplinary study was performed on a c. 30 m thick, limnic–deltaic sequence in the Styrian Basin (Austria). Geophysical (gamma ray activity, rock magnetism), geochemical (organic carbon, sulphur) and sedimentological observations were combined with palaeontological information (mainly ostracods). On this base, several ecological factors were deduced (terrigenous influx, salinity, water depth and oxygenation). Based on integrated stratigraphy as well as on palaeomagnetic results the whole section is set to Chron C5r.2r−1n (11.308–11.263 Ma) and covers a period of less than 45 kyr. In addition to the long-term record, we analysed short-term changes by high-resolution sampling (5 mm sample interval; ostracods, magnetic susceptibility). This ~ 2.3 m-thick interval spans in total < 3500 yr with an individual sample resolution of a few years only. The combination of these data permit the description of the palaeoenvironmental evolution of the section in detail: at the base of the section, the development of a conifer swamp on the lakeside of Lake Pannon is documented. This almost freshwater swamp existed for some centuries before it became extinct within a few decades due to a rise of the water-table. The drowning is related to a transgression of Lake Pannon, which triggered the establishment of a brackish-water fauna as well as greigite formation in the lake sediments. In general, the ongoing transgression favoured benthic life due to increased salinity (up to mesohaline conditions). The high-resolution ostracod and magnetic susceptibility record reflect short-term fluctuations in bottom-water ventilation. These oscillations probably range in the order of centuries and decades and are possibly related to climatic shifts. Later, the successive deepening of the lake resulted in a significant faunal turnover. A meromictic system with a well-established, oxygen-depleted hypolimnion developed. Finally, the limnic phase was replaced by a prograding

  2. Abundance, composition, and distribution of crustacean zooplankton in relation to hypolimnetic oxygen depletion in west-central Lake Erie

    USGS Publications Warehouse

    Heberger, Roy F.; Reynolds, James B.

    1977-01-01

    Samples of crustacean zooplankton were collected monthly in west-central Lake Erie in April and June to October 1968, and in July and August 1970, before and during periods of hypolimnetic dissolved oxygen (DO) depletion. The water column at offshore stations was thermally stratified from June through September 1968, and the hypolimnion contained no DO in mid-August of 1968 or 1970. Composition, abundance, and vertical distribution of crustacean zooplankton changed coincidentally with oxygen depletion. From July to early August, zooplankton abundance dropped 79% in 1968 and 50% in 1970. The declines were attributed largely to a sharp decrease in abundance of planktonic Cyclops bicuspidatus thomasi. Zooplankton composition shifted from mainly cyclopoid copepods in July to mainly cladocerans and copepod nauplii in middle to late August. We believe that mortality of adults and dormancy of copepodites in response to anoxia was the probable reason for the late summer decline in planktonic C. b. thomasi.

  3. A TEX86 lake record suggests simultaneous shifts in temperature in Central Europe and Greenland during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Blaga, Cornelia I.; Reichart, Gert-Jan; Lotter, André F.; Anselmetti, Flavio S.; Sinninghe Damsté, Jaap S.

    2013-03-01

    High-resolution quantitative temperature records from continents covering glacial to interglacial transitions are scarce but important for understanding the climate system. We present the first decadal resolution record of continental temperatures in Central Europe during the last deglaciation (~14,600-10,600 cal. yr B.P.) based on the organic geochemical palaeothermometer TEX86. The TEX86-inferred temperature record from Lake Lucerne (Vierwaldstättersee, Switzerland) reveals typical oscillations during the Late Glacial Interstadial, followed by an abrupt cooling of 2°C at the onset of Younger Dryas and a rapid warming of 4°C at the onset of the Holocene, within less than 350 years. The remarkable resemblance with the Greenland and regional stable oxygen isotope records suggests that temperature changes in continental Europe were dominated by large-scale reorganizations in the northern hemispheric climate system.

  4. Spatial and Temporal Variations of Water Temperature in a High-altitude Deep Dimictic Mountain Lake (Nam Co), Central Tibetan Plateau, with Emphasis on Thermal Stratification

    NASA Astrophysics Data System (ADS)

    Wang, J.; Huang, L.; Lü, X.; Ju, J.; Daut, G.; Wang, Y.; Ma, Q.; Zhu, L.; Haberzettl, T.; Baade, J.; Maeusbacher, R.

    2016-12-01

    Water temperature and the related thermal structure and stratification of a lake are of great importance to lake ecosystems due to their significant impact on vertical exchanges of dissolved and particulate matters. Numerous lakes exist on the Tibetan Plateau (TP), but continuous characteristics of thermal stratification of these lakes are rarely reported. In this study, we present the seasonal variations of water temperature at different depth from a large deep lake (Nam Co) on the central Tibetan Plateau. Results show that Nam Co is a typical dimictic lake with the onset and end of thermal stratification in early June and early November, respectively. Increase of water temperature in spring in the eastern small sub-basin is approximately one month prior to that of the main basin, which is likely caused by the different water depth and transparency in both sub-basins. Daily mean surface water temperature of the main open lake area is highly correlated to air temperature but shows a hysteresis effect of 38 days. Temperature of the entire water body cools down to about 0.5 ° before freezing showing the intensive influence of strong wind exposure and the different behavior of warming up in different years has been ascribed to wind intensity and air temperature. Diurnal changes of water temperature during different seasons demonstrate the distinct influences of internal waves and seiches within the lake. The period of 24 h was observed in summer and autumn which is likely the result of external wind forcing dominated by the breeze variations of the wind at the lake surface. Maximum daily changes up to 3.59 ° at 21 m water depth where the thermocline strength is most intensive are observed in summer. Our results provide valuable validation for quantitative paleotemperature reconstructions using lake sediments by quantifying the difference of annual mean lake surface temperature and mean annual air temperature (6.62 °). As Nam Co is a typical lake in this area

  5. Littoral landforms and pedosedimentary sequences indicating late Holocene lake-level changes in northern central Europe - a case study from northeastern Germany

    NASA Astrophysics Data System (ADS)

    Kaiser, Knut; Küster, Mathias; Fülling, Alexander; Theuerkauf, Martin; Dietze, Elisabeth; Graventein, Hagen; Koch, Paul J.; Bens, Oliver; Brauer, Achim

    2014-05-01

    A multidisciplinary study was carried out at Lake Großer Fürstenseer See (LFS) in order to explore the potential of littoral sediments, palaeosols and landforms as indicators of historical lake-level changes. This research was initiated to investigate the extent to which lakes in northern central Europe responded hydrologically to climatic and land-use changes in the last millennium. The c. 2.5 km2 large lake is located in a glacial outwash plain and fed predominantly by precipitation and groundwater. Specific landforms investigated comprise lake terraces, beach ridges, local basins/peatlands and dunes, revealing a local wealth of sedimentary sub-environments at the lakeshore. Eleven sections were recorded with subsequent sedimentological-pedological, geochronological (OSL, 14C) and palaeobotanical (pollen, macro remains) analyses. Most of the pedosedimentary littoral sequences show a succession of basal glacial sand, intermediate palaeosols and lacustrine sand on top. A broader number of (semi-) terrestrial buried palaeosols along the lakeshore were systematically identified and analysed, providing evidence for changing hydrological site conditions during the late Holocene. Additional historical data from the last centuries (e.g. maps, aerial photos, public records) allow the lake-levels reconstructed from geoarchives to be connected with modern gauging data. All local data sources available enable a tracing of lake-level changes of the LFS during the last millennium, comprising periods of relatively low (c. 1200 AD, 2000s AD) and relatively high water levels (c. 1250-1450 AD, c. 1780 AD, 1980s AD). The amplitude of lake-level changes during the last c. 1000 years amounts to c. 3 m, so that the fluctuations of the last 30 years recorded by lake-level monitoring only reflect a small amount of the potential variability. Regional climate and local land-use history suggest that the Medieval lake-level dynamics of LFS were primarily governed by climate and

  6. A High Resolution Record of Central Asian Climate Change Over the Last 1,000 Years From Lake Issyk-Kul, Kyrgyzstan.

    NASA Astrophysics Data System (ADS)

    Ricketts, R. D.; Rasmussen, K. A.

    2001-12-01

    Lake Issyk-Kul is a highly oligotrophic, brackish closed-basin lake located in the heart of central Asia. Its continental-interior position along the PAGES-PEP II transect in an area where relatively few records of past climate have been fully exploited makes it an interesting site for paleoclimate research. Sedimentary, geochemical and palynological analyses of sediment recovered from the lake indicate that the sediment contains carbonate, clastic and organic components that suggest that changes in lake-level and climate have affected the basin. Previous work on sediment from the basin has focused on piston cores that contain sediment deposited during the last 1,000 to 11,000 years, while this work focuses on sediment deposited more recently. Multicores were collected from the lake in order to recover the last 1,000 years of the sediment record. Two of these cores (3MC and 8MC) were selected for detailed analyses due to the proximity of their core sites to locations where longer and extensively analyzed piston cores had been recovered. These multicores were analyzed for AMS-radiocarbon and 210Pb ages, grain size, %carbonate, %TOC, carbonate mineralogy, and the stable isotope and trace element content of ostracode shells. Radiocarbon ages indicate that sediment in the relatively short (35 cm) multicores extends back approximately 1,000 years, which gives a sediment accumulation rate (0.35 mm/year) for the multicores that is similar to that found in piston cores collected from the lake. Instrumental records of lake level over the last 80 years and 14C dates from archeological sites indicate that the lake level of Issyk-Kul has fluctuated by approximately 20 meters over the last millennium. A comparison between the archeological/instrumental lake-level record and the climate record contained in sediment from the two multicores indicates some correlations between the records.

  7. Holocene evolution of the River Nile drainage system as revealed from the Lake Dendi sediment record, central Ethiopian highlands

    NASA Astrophysics Data System (ADS)

    Wagner, B.; Viehberg, F. A.; Wennrich, V.; Junginger, A.; Kolvenbach, A.; Rethemeyer, J.; Schaebitz, F.; Schmiedl, G. H.

    2015-12-01

    A 12 m long sediment sequence from Dendi Crater lakes, located on the central Ethiopian Plateau, was analysed with sedimentological and geochemical methods to reconstruct the regional environmental history. Bulk organic carbon samples from 23 horizons throughout the sequence were used for AMS radiocarbon dating and indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Microscope analyses and sedimentological data reveal three tephra layers, of which the most prominent layer with a thickness of ~2 m was deposited at 10.2 cal kyr BP and probably originates from an eruption of the Wenchi crater 12 km to the west of the Dendi lakes. Sedimentological data of the pelagic deposits indicate shifts in erosion and rainfall throughout the record. A decrease in Ca and Sr at 11.6 cal kyr BP is related to the shift of less humid condition during the Younger Dryas (YD) to the return to full humid conditions of the African Humid Period (AHP). Single thin horizons with high carbonate content or high Ti and K imply that short spells of dry conditions and significantly increased rainfall superimpose the generally more humid conditions during the AHP. The end of the AHP is gradual. Relatively stable and less humid conditions characterised the Dendi Crater lakes until around 3.9 cal kyr BP. A highly variable increase in clastic matter over the last 1500 years indicates higher erosion due to short-term variations in precipitation within the Dendi catchment. Overall, the sediment record suggests moderate change of precipitation during the Holocene, which is probably due to their exposed location in the Ethiopian highlands. The data from the Dendi Crater lakes show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile provided the main freshwater source for maintaining EMS stratification and sapropel S1 formation between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification is recorded from equatorial East Africa

  8. SOURCE APPORTIONMENT OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) INTO CENTRAL PARK LAKE, NEW YORK CITY, OVER A CENTURY OF DEPOSITION

    PubMed Central

    Yan, Beizhan; Bopp, Richard F.; Abrajano, Teofilo A.; Chaky, Damon; Chillrud, Steven N.

    2014-01-01

    Relative contributions of polycyclic aromatic hydrocarbons (PAHs) from combustion sources of wood, petroleum, and coal were computed in sediments from Central Park Lake in New York City (NY, USA) by chemical mass balance based on several reliable source indicators. These indicators are the ratio of retene to the sum of retene and chrysene, the ratio of 1,7-dimethylphenanthrene (DMP) to 1,7-DMP and 2,6-DMP, and the ratio of fluroanthene to fluroanthene and pyrene. The authors found that petroleum combustion–derived PAH fluxes generally followed the historical consumption data of New York State. Coal combustion-derived PAH flux peaked approximately in the late 1910s, remained at a relatively high level over the next 3 decades, then rapidly declined from the 1950s to the 1960s; according to historical New York State coal consumption data, however, there was a 2-peak trend, with peaks around the early 1920s and the mid-1940s. The 1940s peak was not observed in Central Park Lake, most likely because of the well-documented shift from coal to oil as the major residential heating fuel in New York City during the late 1930s. It was widely believed that the decreased PAH concentrations and fluxes in global sediments during the last century resulted from a major energy shift from coal to petroleum. The data, however, show that this shift occurred from 1945 through the 1960s and did not result in an obvious decline. The sharpest decrease, which occurred in the 1970s was not predominantly related to coal usage but rather was the result of multiple factors, including a decline in petroleum usage largely, the introduction of low sulfur–content fuel in New York City, and the introduction of emission-control technologies. PMID:24375577

  9. Source apportionment of polycyclic aromatic hydrocarbons (PAHs) into Central Park Lake, New York City, over a century of deposition.

    PubMed

    Yan, Beizhan; Bopp, Richard F; Abrajano, Teofilo A; Chaky, Damon; Chillrud, Steven N

    2014-05-01

    Relative contributions of polycyclic aromatic hydrocarbons (PAHs) from combustion sources of wood, petroleum, and coal were computed in sediments from Central Park Lake in New York City (NY, USA) by chemical mass balance based on several reliable source indicators. These indicators are the ratio of retene to the sum of retene and chrysene, the ratio of 1,7-dimethylphenanthrene (DMP) to 1,7-DMP and 2,6-DMP, and the ratio of fluroanthene to fluroanthene and pyrene. The authors found that petroleum combustion-derived PAH fluxes generally followed the historical consumption data of New York State. Coal combustion-derived PAH flux peaked approximately in the late 1910s, remained at a relatively high level over the next 3 decades, then rapidly declined from the 1950s to the 1960s; according to historical New York State coal consumption data, however, there was a 2-peak trend, with peaks around the early 1920s and the mid-1940s. The 1940s peak was not observed in Central Park Lake, most likely because of the well-documented shift from coal to oil as the major residential heating fuel in New York City during the late 1930s. It was widely believed that the decreased PAH concentrations and fluxes in global sediments during the last century resulted from a major energy shift from coal to petroleum. The data, however, show that this shift occurred from 1945 through the 1960s and did not result in an obvious decline. The sharpest decrease, which occurred in the 1970s was not predominantly related to coal usage but rather was the result of multiple factors, including a decline in petroleum usage largely, the introduction of low sulfur-content fuel in New York City, and the introduction of emission-control technologies. © 2013 SETAC.

  10. Temporal fluctuation and reproduction of Thermocyclops decipiens (Copepoda, Cyclopoida) in an eutrophic lake of central Brazil.

    PubMed

    Padovesi-Fonseca, Claudia; de Mendonça-Galvão, Luciana; Rocha, Diogo Libânio Pereira

    2002-03-01

    Lake Paranoá is an eutrophic reservoir situated in the urban region of Brasília. This study was carried out in a fixed collection station located in the Riacho Fundo branch of the reservoir. Zooplankton samples were collected at intervals of 3-5 d at 9:00 a.m. during two months in the dry and rainy seasons for two years (dry-1996, rainy-1997, dry-1997 and rainy-1998), using a 64 microns-mesh plankton net. The most predominant species was Thermocyclops decipiens (about 50% of the total zooplankton community), which during the whole period had a high reproductive rate. The highest densities were found in the dry-1996 season (1700 ind/l for nauplii), and also fluctuated widely overtime. Nauplii stages dominated during the four periods, comprising 50-75% of the total population density. Ovigerous females peaked in the dry-1996 and rainy-1997 seasons, with 20-30% of the total females. The largest peak in egg production occurred during the dry-1996 season, and the total egg production was 2.0 x 10(3) eggs/l. Mesocyclops longisetus is a first record for Lake Paranoá. The ecological factors that determine the success of T. decipiens in eutrophic systems are related to omnivorous feeding habits and prey-predator interactions.

  11. Gravity Data from Dry Lake and Delamar Valleys, east-central Nevada

    USGS Publications Warehouse

    Mankinen, Edward A.; Chuchel, Bruce A.; Moring, Barry C.

    2008-01-01

    Cenozoic basins in eastern Nevada and western Utah constitute major ground-water recharge areas in the eastern part of the Great Basin, and our continuing studies are intended to characterize the geologic framework of the region. Prior to these investigations, regional gravity coverage was variable over the region, adequate in some areas and very sparse in others. The current study in Nevada provides additional high-resolution gravity along transects in Dry Lake and Delamar Valleys to supplement data we established previously in Cave and Muleshoe Valleys. We combine all previously available gravity data and calculate an up-to-date isostatic residual gravity map of the study area. Major density contrasts are identified, indicating zones where Cenozoic tectonic activity could have been accommodated. A gravity inversion method is used to calculate depths to pre-Cenozoic basement rock and to estimate maximum alluvial/volcanic fill in the valleys. Average depths of basin fill in the deeper parts of Cave, Muleshoe, Dry Lake, and Delamar Valleys are approximately 4 km, 2 km, 5 km, and 3 km, respectively.

  12. Holocene pollen and sediment record from the tangle lakes area, central Alaska

    USGS Publications Warehouse

    Ager, Thomas A.; Sims, John D.

    1981-01-01

    Pollen and sediments have been analyzed from a 5.5 meter‐length core of lacustrine sediments from Tangle Lakes, in the Gulkana Upland south of the Alaska Range (63 ° 01 ‘ 46”; N. latitude, 146° 03 ‘ 48 “ W. longitude). Radiocarbon ages indicate that the core spans the last 4700 years. The core sediments are sandy silt and silty clay; the core shows distinct rhythmic laminations in the lower 398 cm. The laminae appear to be normally graded; peat fibers and macerated plant debris are more abundant near the tops of the laminae. Six volcanic‐ash layers are present in the upper 110 cm of the core.Present‐day vegetation of the Tangle Lakes area is mesic shrub tundra and open spruce woodland, with scattered patches of shrub willow (Salix), balsam poplar (P. balsamifera), spruce (Picea), paper birch (Betula papyrifera), and alder (Alnus). Pollen analysis of 27 core samples suggests that this vegetation type has persisted throughout the past 4700 years, except for an apparently substantial increase in Picea beginning about 3500 years B.P. Percentages of Picea pollen are very low (generally 1–3 percent) in the lower 2 meters of core (ca. 4700 to 3500 years B.P.), but rise to 13–18 percent in the upper 3.4 meters (ca. 3500 years B.P. to present). Previously reported data from this area indicate that Picea trees initially arrived in the Tangle Lakes area about 9100 years B.P., at least 2.5 to 3 thousand years after deglaciation of the region. The present investigation suggests that Picea trees became locally scarce or died out sometime after about 9000 years B.P. but before 4700 years B.P., then reinvaded the area about 3500 years B.P. If this extrapolated age for the Picea reinvasion is accurate it suggests that local expansion of the Picea population coincides with the onset of a Neoglacial interval of cooler, moister climate. This is an unexpected result, because intervals of cooler climate generally coincide with lowering of the altitudinal limit of

  13. Fuel treatments, fire suppression, and their interaction with wildfire and its impacts: the Warm Lake experience during the Cascade Complex of wildfires in central Idaho, 2007

    Treesearch

    Russell T. Graham; Theresa B. Jain; Mark Loseke

    2009-01-01

    Wildfires during the summer of 2007 burned over 500,000 acres within central Idaho. These fires burned around and through over 8,000 acres of fuel treatments designed to offer protection from wildfire to over 70 summer homes and other buildings located near Warm Lake. This area east of Cascade, Idaho, exemplifies the difficulty of designing and implementing fuel...

  14. The lacustrine carbon cycle as illuminated by the waters and sediments of two hydrologically distinct headwater lakes in North-Central Minnesota, U.S.A

    USGS Publications Warehouse

    Dean, W.E.; Schwalb, A.

    2002-01-01

    The accumulation rates of CaCO3 and organic carbon (OC) in lake sediments are delicately balanced between production in the epilimnion and destruction in the hypolimnion. The cycling of these two forms of carbon makes a "carbon pump" that greatly affects the biogeochemical cycles of other elements. To further understand these biogeochemical dynamics, the lakes, streams, and wetlands of the Shingobee River headwater area of north-central Minnesota have been subjected to intensive hydrologic and biogeochemical studies. Williams Lake, situated close to the highest point in the regional flow system, is hydrologically closed, with no surface inlet or outlet, and ground water and precipitation as the only sources of water. Shingobee Lake, situated at the lowest point in the regional flow system, has the Shingobee River as an inlet and outlet. The surface waters of both lakes are oversaturated, and the bottom waters undersaturated, with respect to CaCO3 during the summer. The small amount of CaCO3 that is precipitated in the epilimnion of Williams Lake during the summer is dissolved in the undersaturated hypolimnion and sediments with the result that no CaCO3 is incorporated into the profundal surface sediments. Because of the high phytoplankton productivity of Shingobee Lake, sufficient CaCO3 is produced in the epilimnion that large amounts survive the corrosive hypolimnion and sediments, and an average of 46 wt. % accumulates in surface sediments. Another consequence of higher phytoplankton productivity in Shingobee Lake is that the hypolimnion becomes oxygen deficient within a month after overturn in both the spring and fall. Because of reducing conditions that develop in the hypolimnion of Shingobee Lake, high concentrations of dissolved Fe and Mn accumulate there during summer stratification. Precipitation of Fe and Mn oxyhydroxides during periods of fall and spring overturn results in high concentrations of Fe and Mn in surface sediments. In Williams Lake, high

  15. Human-climate interactions in the central Mediterranean region during the last millennia: The laminated record of Lake Butrint (Albania)

    NASA Astrophysics Data System (ADS)

    Morellón, Mario; Anselmetti, Flavio S.; Ariztegui, Daniel; Brushulli, Brunhilda; Sinopoli, Gaia; Wagner, Bernd; Sadori, Laura; Gilli, Adrian; Pambuku, Arben

    2016-03-01

    Lake Butrint (39°47 N, 20°1 E) is a ca. 21 m deep, coastal lagoon located in SW Albania where finely-laminated sediments have been continuously deposited during the last millennia. The multi-proxy analysis (sedimentology, high-resolution elemental geochemistry and pollen) of a 12 m long sediment core, supported by seven AMS radiocarbon dates and 137Cs dating, enable a precise reconstruction of the environmental change that occurred in the central Mediterranean region during the last ∼4.5 cal kyrs BP. Sediments consist of triplets of authigenic carbonates, organic matter and clayey laminae. Fluctuations in the thickness and/or presence of these different types of seasonal laminae indicate variations in water salinity, organic productivity and runoff in the lake's catchment, as a result of the complex interplay of tectonics, anthropogenic forcing and climate variability. The progradation of the Pavllo river delta, favoured by variable human activity from the nearby ancient city of Butrint, led to the progressive isolation of this hydrological system from the Ionian Sea. The system evolved from an open bay to a restricted lagoon, which is consistent with archaeological data. An abrupt increase in mass-wasting activity between 1515 and 1450 BC, likely caused by nearby seismic activity, led to the accumulation of 24 homogenites, up to 17 cm thick. They have been deposited during the onset of finely laminated sedimentation, which indicates restricted, anoxic bottom water conditions and higher salinity. Periods of maximum water salinity, biological productivity, and carbonate precipitation coincide with warmer intervals, such as the early Roman Warm Period (RWP) (500 BC-0 AD), the Medieval Climate Anomaly (MCA) (800-1400 AD) and recent times (after 1800 AD). Conversely, lower salinity and more oxic conditions, with higher clastic input were recorded during 1400-500 BC, the Late Roman and the Early Medieval periods (0-800 AD) and during the Little Ice Age (1400-1800 AD

  16. Hydrological and chemical estimates of the water balance of a closed-basin lake in north central Minnesota

    USGS Publications Warehouse

    LaBaugh, J.W.; Winter, T.C.; Rosenberry, D.O.; Schuster, P.F.; Reddy, M.M.; Aiken, G.R.

    1997-01-01

    Chemical mass balances for sodium, magnesium, chloride, dissolved organic carbon, and oxygen 18 were used to estimate groundwater seepage to and from Williams Lake, Minnesota, over a 15-month period, from April 1991 through June 1992. Groundwater seepage to the lake and seepage from the lake to groundwater were determined independently using a flow net approach using data from water table wells installed as part of the study. Hydrogeological analysis indicated groundwater seepage to the lake accounted for 74% of annual water input to the lake; the remainder came from atmospheric precipitation, as determined from a gage in the watershed and from nearby National Weather Service gages. Seepage from the lake accounted for 69% of annual water losses from the lake; the remainder was removed by evaporation, as determined by the energy budget method. Calculated annual water loss exceeded calculated annual water gain, and this imbalance was double the value of the independently measured decrease in lake volume. Seepage to the lake determined from oxygen 18 was larger (79% of annual water input) than that determined from the flow net approach and made the difference between calculated annual water gain and loss consistent with the independently measured decrease in lake volume. Although the net difference between volume of seepage to the lake and volume of seepage from the lake was 1% of average lake volume, movement of water into and out of the lake by seepage represented an annual exchange of groundwater with the lake equal to 26-27% of lake volume. Estimates of seepage to the lake from sodium, magnesium, chloride, and dissolved organic carbon did not agree with the values determined from flow net approach or oxygen 18. These results indicated the importance of using a combination of hydrogeological and chemical approaches to define volume of seepage to and from Williams Lake and identify uncertainties in chemical fluxes.

  17. Deposition and chemistry of bottom sediments in Cochiti Lake, north-central New Mexico

    USGS Publications Warehouse

    Wilson, Jennifer T.; Van Metre, Peter C.

    2000-01-01

    Bottom sediments were sampled at seven sites in Cochiti Lake in September 1996. Sediment cores penetrating the entire lacustrine sediment sequence were collected at one site near the dam. Surficial sediments were sampled at the near-dam site and six other sites located along the length of the reservoir. Analyses included grain size, major and trace elements, organochlorine compounds, polycyclic aromatic hydrocarbons (PAH's), and radionuclides. Concentrations of trace elements, organic compounds, and radionuclides are similar to those in other Rio Grande reservoirs and are low compared to published sediment-quality guidelines. Most elements and compounds that were detected did not show trends in the age estimated sediment cores with the exception of a decreasing trend in total DDT concentrations from about 1980 to 1992. The mixture of PAH's suggests that the increase is caused by inputs of fuel-related PAH and not combustion- related PAH.

  18. Relation of adult size to movements and distribution of smallmouth bass in a central Maine Lake

    USGS Publications Warehouse

    Cole, M.B.; Moring, J.R.

    1997-01-01

    Forty-four smallmouth bass Micropterus dolomieu of three size-classes were radiotracked in Green Lake, Maine, during summer 1993 (10 June-1 September) to determine whether adult size influenced distribution and movement. Large smallmouth bass (>406 mm) used deep water (>8 m) more often than did small (248-279 mm) or medium-sized (305-356 mm) smallmouth bass during the late summer (15 July-1 September). Large smallmouth bass also were found at middepths (4-8 m) significantly more often than were small individuals during late summer. Small fish used cover more frequently than large ones during early summer (10 June-13 July). Both small and medium-sized individuals were associated with cover more frequently than large smallmouth bass were during the late summer. Small smallmouth bass exhibited significantly smaller summer total ranges than did large individuals, and mean active displacement differed among all three size-classes.

  19. Littoral landforms and pedosedimentary sequences indicating late Holocene lake-level changes in northern central Europe - A case study from northeastern Germany

    NASA Astrophysics Data System (ADS)

    Kaiser, Knut; Küster, Mathias; Fülling, Alexander; Theuerkauf, Martin; Dietze, Elisabeth; Graventein, Hagen; Koch, Paul Jörg; Bens, Oliver; Brauer, Achim

    2014-07-01

    A multidisciplinary study was carried out at Lake Großer Fürstenseer See (LFS) in order to explore the potential of littoral sediments, palaeosols and landforms as indicators of historical lake-level changes. This research was initiated to investigate the extent to which lakes in northern central Europe responded hydrologically to climatic and land-use changes in the last millennium. Specific landforms investigated comprise lake terraces, beach ridges, local basins/peatlands and dunes, revealing a wealth of sedimentary sub-environments at the lakeshore. Eleven sections were recorded with subsequent sedimentological-pedological, geochronological (OSL, 14C) and palaeobotanical (pollen, macro remains) analyses. Most of the pedosedimentary littoral sequences show a succession of basal glacial sand, intermediate palaeosols and lacustrine sand on top. A broader number of (semi-)terrestrial buried palaeosols along the lakeshore were systematically identified and analysed, providing evidence for changing hydrological conditions during the late Holocene. Additional historical data from the last centuries (e.g. maps, aerial photos, public records) allow the lake-levels reconstructed from geoarchives to be connected with modern gauging data. All local data sources available enable a tracing of lake level changes of the LFS during the last millennium, comprising periods of relatively low (c. 1200 AD, 2000s AD) and relatively high water levels (c. 1250-1450 AD, c. 1780 AD, 1980s AD). The amplitude of lake-level changes during the last c. 1000 years amounts to c. 3 m, so that the fluctuations of the last 30 years recorded by lake-level monitoring only reflect a small amount of the potential variability. Regional climate and local land-use history suggest that the Medieval lake-level dynamics of LFS were primarily governed by climate and secondarily influenced by human impact on the drainage system. At present the lake level is additionally influenced by the impact of highly

  20. Acid-leachable Li and Mg from Lake Cuitzeo sediments in the central Mexico: Paleoclimate change during the past 45 Ka

    NASA Astrophysics Data System (ADS)

    Li, H.; Alcantara, I. I.; Bischoff, J. L.; Wen, D.; Garduño-Monroy, V. H.

    2009-12-01

    Located in Michoacán state of south-central Mexico (19°56’N, 101°5’W), Lake Cuitzeo is an alkaline lake with an area of ~400 km2, average depth of 27m and elevation of 1821m. A 27-m long core was retrieved from the lake, covering about 127-kyr depositional history. The chronology of the upper 9.2m of the core has been reconstructed by radiocarbon dates, showing a continuous deposition during the past 45 Ka. Using 0.5N HCl for leaching the de-ionized water washed lake sediments, we have measured the acid-leachable (AL) elements including Na, K, Li, Mg and Si by ICP-OES. Comparing to the total Si content in bulk sediments ranging from 10 to 40 wt.% with an average of 25.2 ± 4.3 wt.%, the AL Si ranges from 0.064 to 0.375 wt.% with an average of 0.253 ± 0.048 wt.%. The AL Mg content has strongly linear correlation with the total Mg content in the bulk sediments, but accounts for ~55% of the total Mg content. When the carbonate content in the sediment is greater than 10%, the weight loss by the acid-leaching is mainly from dissolution of carbonate. In addition, when the AL Mg is less than 1%, AL Li and AL Mg appear strongly linear correlation. Thus, the AL Li and Mg contents are mainly from authigenic minerals formed in the lake, such as carbonate and sepiolite. When Mg was used up in the lake due to precipitation of carbonate and sepiolite, Li will substitute in sepiolite under the hyper saline and alkaline lake conditions. Therefore, AL Li and Mg contents in the lake sediments can be used as indicators of lake hydrological change under different climatic conditions. High CaCO3%, Li and Mg contents in the periods of 2~12Ka, 19~24Ka, 28~31Ka, 33~34Ka, 35~38Ka and 43~45Ka, indicate higher salinity and alkalinity of the lake hence lower lake levels might be caused by dry and/or warm climates. During 12~20Ka, the lake was relatively fresh and deeper, reflecting cold but wet climatic conditions due to jet stream shifted south during LGM.

  1. An empirical model of sediment deposition processes in Lake Kerkini, Central Macedonia Greece.

    PubMed

    Psilovikos, Aris; Margoni, Sofia

    2010-05-01

    The deposition processes in Kerkini Reservoir, since 1933, are examined in this paper. Built on the course of River Strymonas at the plain of Serres for anti-flooding control, it was gradually developed as a multipurpose reservoir for irrigation and a very important international wetland protected by the Ramsar Treaty. The deposition into Lake Kerkini is caused by the high rates of sediment transport by River Strymonas from the Bulgarian, Serbian and Former Yugoslav Republic of Macedonia territory drainage basin of Kerkini of 11,600 km(2). The life expectancy of the original reservoir was approximately 40 years. The sediment transport and the deposition volumes and rates were high during the first stages of Kerkini operation due to deforestations and stockbreeding activities against forested and agricultural areas in southwestern Bulgaria before World War II, which intensify erosion and deposition phenomena in Kerkini's catchment. They were gradually reduced due to the anti-erosion hydraulic works, extended reforestations mainly in the period 1962-1977, and the natural processes of Strymonas-Kerkini hydrosystem to attain its equilibrium. Based on six systematic bottom surveys of the reservoir from 1933 to 1991, two empirical formulas of the total deposition volume (Sigma V(s)) and the deposition rates (DeltaSigma V(s)/DeltaSigma t) through time (Sigma t) were developed. The results have been compared with other catchments of the broader Balkan area concerning the erosion, sediment yield, sediment deposition volumes, and rates, and it was found in accordance with the measured data. The obtained empirical model was used to estimate the life expectancy of the new rebuilt reservoir of Kerkini in 1984; in the case of natural processes, these do not change dramatically in the transboundary Lake Kerkini catchment. The deposition processes of Kerkini were the major causes of its development into an internationally important wetland and biotope. Kerkini offers development

  2. Chronology and climatic controls of late Quaternary lake-level fluctuations in Chewaucan, Fort Rock and Alkali basins, south-central Oregon

    SciTech Connect

    Freidel, D.E.

    1993-01-01

    In this study, lake-level chronologies of three closed-basin lakes in south-central Oregon were developed and compared with the chronologies of Lakes Bonneville and Lahontan in Utah and Nevada. Geomorphic and stratigraphic study of shoreline features, and radiocarbon dating of rock varnish and gastroped shells associated with high shorelines indicate that the three Oregon paleolakes reached their most recent high stands synchronously before 18,000 to 17,000 radiocarbon yrs B.P., three thousand to forty-five hundred years earlier than the high stands of Lakes Lahontan and Bonneville. Levels of the Oregon paleolakes began to drop at a time when Lakes Lahontan and Bonneville were still rising. This study employed water balance modelling to evaluate several climatic scenarios that would generate high stands in the three Oregon lakes. Latitudinal shifts in the polar jet stream and associated westerlies, that occurred in response to the growth and decay of the continental ice sheets, have been proposed as a mechanism for the timing and magnitude of the Northern Great Basin paleolake high stands. General circulation model simulations and paleoenvironmental evidence indicate that at 18,000 radiocarbon yrs B.P. colder and moister than present conditions prevailed in the Northern Great Basin, while very cold, arid climatic conditions prevailed in the Northwest due to strong, glacial anticyclonic circulation generated by the continental ice sheet. Water balance modelling in this study indicates that colder and moister than present climatic conditions caused the Oregon lakes to rise to their highest level. Climatic conditions of south-central Oregon at 18,000 radiocarbon yrs B.P. were probably influenced more by the westerlies associated with the jet stream to the south than by the glacial anticylonic circulation to the north.

  3. Karyotype characteristics, larval morphology and chromosomal polymorphism peculiarities of Glyptotendipes salinus Michailova, 1983 (Diptera, Chironomidae) from Tambukan Lake, Central Caucasus.

    PubMed

    Karmokov, Mukhamed Kh; Akkizov, Azamat Y

    2016-01-01

    Data on the karyotype characteristics, larval morphology and features of chromosomal polymorphism of a population of Glyptotendipes salinus Michailova, 1983 (Diptera, Chironomidae) from Tambukan Lake (on the northern macroslope of the central Caucasus) are presented. It was found that diagnostic larval characters of Glyptotendipes salinus from Caucasus in general are similar to those described in previous studies, but with some significant differences. By some morphological characteristics Caucasian larvae appeared to be closer to Glyptotendipes barbipes than to ones provided for European larvae of Glyptotendipes salinus by Contreras-Lichtenberg (1999). Obtained morphological data make possible to conclude that Caucasian population of Glyptotendipes salinus can be a markedly diverged population of the species, probably even subspecies. In the Caucasian population 12 banding sequences were found: two in arms A, B, C, E, and G, and one in arms D and F. Eight of these are already known for this species, and four, salA2, salB2, salEX, and salG3, are described for the first time. Genetic distances between all the previously studied populations of Glyptotendipes salinus were measured using Nei criteria (1972). The population of the central Caucasus occupies a distinct position on the dendrogram compared with populations from Altai and Kazakhstan. All the obtained morphological and cytogenetic data can indicate the plausible relative isolation and complexity of the Caucasus from the viewpoint of microevolution. More researches are required in other parts of Caucasus and other geographically distant regions for more specific allegations.

  4. Selection of prey by walleyes in the Ohio waters of the central basin of Lake Erie, 1985-1987

    USGS Publications Warehouse

    Wolfert, David R.; Bur, Michael T.

    1992-01-01

    Walleyes (Stizostedion vitreum vitreum) were collected at five locations in the central basin of Lake Erie in 1985-87. The contents of the fishes' stomachs were examined to identify the species of prey. The seasonal availability of potential prey was determined from sampling with trawl tows. Food electivity indexes for young-of-the-year (YOY) and older walleyes were calculated. Electivity indexes changed monthly in YOY walleyes that consumed mostly YOY gizzard shads (Dorosoma cepedianum) in July and fed moderately on gizzard shads, but more on smelts (Osmerus mordax), in August. In September and October YOY walleyes did not consume YOY white perch (Morone americana). During October, they continued to eat YOY gizzard shads moderately but consumed mostly emerald shiners (Notropis atherinoides). Older walleys were highly partial to YOY gizzard shads, emerald shiners, and smelts and consumed no YOY white perch. The numbers of YOY yellow perch (Perca flavescens) in stomachs were limited. Prey selection by walleyes in the central basin was species-specific irrespective of abundance of prey.

  5. Karyotype characteristics, larval morphology and chromosomal polymorphism peculiarities of Glyptotendipes salinus Michailova, 1983 (Diptera, Chironomidae) from Tambukan Lake, Central Caucasus

    PubMed Central

    Karmokov, Mukhamed Kh.; Akkizov, Azamat Y.

    2016-01-01

    Abstract Data on the karyotype characteristics, larval morphology and features of chromosomal polymorphism of a population of Glyptotendipes salinus Michailova, 1983 (Diptera, Chironomidae) from Tambukan Lake (on the northern macroslope of the central Caucasus) are presented. It was found that diagnostic larval characters of Glyptotendipes salinus from Caucasus in general are similar to those described in previous studies, but with some significant differences. By some morphological characteristics Caucasian larvae appeared to be closer to Glyptotendipes barbipes than to ones provided for European larvae of Glyptotendipes salinus by Contreras-Lichtenberg (1999). Obtained morphological data make possible to conclude that Caucasian population of Glyptotendipes salinus can be a markedly diverged population of the species, probably even subspecies. In the Caucasian population 12 banding sequences were found: two in arms A, B, C, E, and G, and one in arms D and F. Eight of these are already known for this species, and four, salA2, salB2, salEX, and salG3, are described for the first time. Genetic distances between all the previously studied populations of Glyptotendipes salinus were measured using Nei criteria (1972). The population of the central Caucasus occupies a distinct position on the dendrogram compared with populations from Altai and Kazakhstan. All the obtained morphological and cytogenetic data can indicate the plausible relative isolation and complexity of the Caucasus from the viewpoint of microevolution. More researches are required in other parts of Caucasus and other geographically distant regions for more specific allegations. PMID:28123679

  6. Hydrological changes in western Central Asia (Kyrgyzstan) during the Holocene as inferred from a palaeolimnological study in lake Son Kul

    NASA Astrophysics Data System (ADS)

    Huang, Xiangtong; Oberhänsli, Hedi; von Suchodoletz, Hans; Prasad, Sushma; Sorrel, Philippe; Plessen, Birgit; Mathis, Marie; Usubaliev, Raskul

    2014-11-01

    The hydrology of western Central Asia is highly sensitive to climatic perturbations. In order to understand its long-term variability and to infer linkages between precipitation and atmospheric and oceanic systems, we conducted a thorough sedimentary and geochemical study on a composite core retrieved in lake Son Kul (central Kyrgyzstan). A multi-proxy approach was conducted on lake sediments based on grain size analyses, magnetic susceptibility, total organic carbon (TOC), total nitrogen (TN) and carbon and oxygen isotope analyses on bulk and biogenic materials (ostracoda and molluscs shells) at a resolution equivalent to ca 40 years, aiming to characterise the sequence of palaeolimnological changes in Son Kul. As indicated by δ18O record of bulk carbonates, mainly consisting of aragonite, the Holocene hydrological balance was negative during most of time, suggesting an excess of evaporation (E) over precipitation (P). Limnological conditions fluctuated rapidly before 5000 cal yr BP indicating significant changes in regional hydrology and climate. In particular, the long-term negative hydrological balance was impeded by several short stages with marked increase of precipitation, lasting several decades to a few centuries (e.g., 8300-8200, 6900-6700, 6300-6100, 5500-5400, 5300-5200 and 3100-3000 cal yr BP). Precipitation changes as inferred from δ18O data are also documented by increased minerogenic detritus and higher TOC. We propose that the seasonal pattern of precipitation varied transiently in western Central Asia during the Holocene, although evaporation changes may also account for the rapid changes observed in δ18O data. When the annual water balance was less critical (P ≤ E), the excess of water might be ascribed to increased precipitation during cold seasons mainly because winter precipitation has more negative δ18O than its summer equivalent. Conversely, when the annual water balance is negative (P ≪ E), the moisture was mainly delivered during

  7. How well suited are maar lakes of Madagascar for palaeoenvironmental multi-proxy reconstructions? - First results from shallow seismic, sedimentological and hydrological investigations in Central and Northwest Madagascar.

    NASA Astrophysics Data System (ADS)

    Daut, Gerhard; Jasmin Krahn, Kim; Rabhobisoa, Jean-Jacques; Ornella Moanazafy, Sergénie; Haberzettl, Torsten; Kasper, Thomas; Mäusbacher, Roland; Schwalb, Antje

    2017-04-01

    Madagascar is well known for its unique flora and fauna which are frequently in the focus of scientific investigations. However, studies on environmental changes in Madagascar linked to Quaternary climatic and/or anthropogenic impact are scarce. The aim of this initial study is to evaluate the potential of maar lakes, situated in different climatic zones of Madagascar, for paleoenvironmental studies and to identify promising coring sites with continuous sediment sequences reaching far back in time. Therefore, in November 2016, a shallow seismic profiling campaign, combined with surface sediment, short gravity core (max. 1.8 m), water and plankton sampling was performed on three target sites. These were two deep maar lakes, i.e., Andraikiba (Central Madagascar, 50m waterdepth) as well as Amparahibe (46,5m waterdepth) and Andampy Ambatoloaka, a shallow (5m waterdepth during low tide) former maar lake now connected to the Ocean (both NW-Madagascar. Vertical water parameter measurements in Lake Amparahibe confirm anoxic bottom conditions, while dissolved oxygen values at the water surface are about 7.9 mg/L (103%). Temperature decreases with depth from 29.3 °C to 27.2 °C, and the lake is slightly alkaline with an electrical conductivity of around 245 µS/cm. Since Andampy Ambatoloaka is connected to the ocean, it shows slightly alkaline conditions as well, electrical conductivity is high ( 57.8 mS/cm) and dissolved oxygen and temperature values are relatively stable at about 8.2 mg/L (104%) and 28.1 °C, respectively. The shallow seismic survey shows an infill with layered sediments of >50 m thickness in Lake Andraikiba. In Lake Amparahibe natural gas in the sediment prevented deeper penetration, however the record shows 10 m of undisturbed, layered sediments in the uppermost part. Sediment cores obtained from both lakes consist of dark brownish to blackish, clayey to silty and partly laminated sediments. High values of magnetic susceptibilities (>1800*10-6 SI) and

  8. Scenario earthquake hazards for the Long Valley Caldera-Mono Lake area, east-central California

    USGS Publications Warehouse

    Chen, Rui; Branum, David M.; Wills, Chris J.; Hill, David P.

    2014-01-01

    As part of the U.S. Geological Survey’s (USGS) multi-hazards project in the Long Valley Caldera-Mono Lake area, the California Geological Survey (CGS) developed several earthquake scenarios and evaluated potential seismic hazards, including ground shaking, surface fault rupture, liquefaction, and landslide hazards associated with these earthquake scenarios. The results of these analyses can be useful in estimating the extent of potential damage and economic losses because of potential earthquakes and in preparing emergency response plans. The Long Valley Caldera-Mono Lake area has numerous active faults. Five of these faults or fault zones are considered capable of producing magnitude ≥6.7 earthquakes according to the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) developed by the 2007 Working Group of California Earthquake Probabilities (WGCEP) and the USGS National Seismic Hazard Mapping (NSHM) Program. These five faults are the Fish Slough, Hartley Springs, Hilton Creek, Mono Lake, and Round Valley Faults. CGS developed earthquake scenarios for these five faults in the study area and for the White Mountains Fault to the east of the study area. Earthquake scenarios are intended to depict the potential consequences of significant earthquakes. They are not necessarily the largest or most damaging earthquakes possible. Earthquake scenarios are both large enough and likely enough that emergency planners should consider them in regional emergency response plans. Earthquake scenarios presented here are based on fault geometry and activity data developed by the WGCEP, and are consistent with the 2008 Update of the United States National Seismic Hazard Maps (NSHM).For the Hilton Creek Fault, two alternative scenarios were developed in addition to the NSHM scenario to account for different opinions in how far north the fault extends into the Long Valley Caldera. For each scenario, ground motions were calculated using the current standard practice

  9. A comparison of aquatic trophic interactions (fish, benthic macroinvertebrates, and zooplankton) between the Lake Erie Central Basin and the Lake Erie Eastern Basin, 2011-2013

    USGS Publications Warehouse

    Bodamer Scarbro, Betsy L.

    2016-01-01

    Lake Erie Biological Station (LEBS), located in Sandusky, Ohio, is a field station of the USGS Great Lakes Science Center (GLSC). LEBS is the primary federal agency for applied fisheries science excellence in Lake Erie. From 2011-2013, LEBS carried out a project which addressed the effects of regional climate change on aquatic food webs in the Great Lakes. This study focused on Lake Erie, as it is a representative system with a high level of anthropogenic impacts, strong nutrient gradients, seasonal hypoxia, and spatial overlap of cold- and cool-water fish guilds. In Lake Erie and in large embayments throughout the Great Lakes basin, this situation is a concern for fishery managers, as climate change may exacerbate hypoxia and reduce habitat volume for some species. We examined fish community composition, fine-scale distribution, prey availability, diets, and biochemical tracers for dominant fishes from study areas with medium-high nutrient levels (mesotrophic, Fairport study area), and low nutrient levels (oligotrophic, Erie study area). This multi-year database (2011-2013) provides the ability to contrast years with wide variation in rainfall, winter ice-cover, and thermal stratification. In addition, multiple indicators of dietary and distributional responses to environmental variability will allow resource managers to select the most informative approach for addressing specific climate change questions.

  10. Comments on cladocerans of crater lakes of the Nevado de Toluca Volcano (Central Mexico), with the description of a new species, Alona manueli sp. nov.

    PubMed

    Sinev, Artem Y; Zawisza, Edyta

    2013-01-01

    Cladoceran communities of two lakes of Nevado de Toluca Volcano, Central Mexico, were studied. A new species of Aloninae, Alona manueli sp. nov., is described. It was previously confused with Palearctic Alona intermedia Sars, 1862, but clearly differs from it in the morphology of postabdomen, head shield and head pores, and thoracic limbs. Position of Alona manueli sp. nov. within the genus is unclear, it did not belong to any species-group within Alona s. lato. Other species recorded in the studied lakes are Alona ossiani Sinev, 1998, Alonella pulchella Herrick, 1884, Chydorus belonging to sphaericus-group, Eurycercus longirostris Hann, 1982 and Pleuroxus cf. denticulatus Birge, 1879.

  11. Linking hydro-climate to the sediment archive: a combined monitoring and calibration study from a varved lake in central Turkey

    NASA Astrophysics Data System (ADS)

    Roberts, C. Neil; Dean, Jonathan R.; Eastwood, Warren J.; Jones, Matthew D.; Allcock, Samantha L.; Leng, Melanie J.; Metcalfe, Sarah E.; Woodbridge, Jessie; Yiǧitbaşıoǧlu, Hakan

    2016-04-01

    Hydro-climatic reconstructions from lake sediment proxies require an understanding of modern formation processes and calibration over multiple years. Here we use Nar Gölü, a non-outlet, monomictic maar lake in central Turkey, as a field site for such a natural experiment. Fieldwork since 1997 has included observations and measurements of lake water and sediment trap samples, and automated data logging (Jones et al., 2005; Woodbridge and Roberts, 2010; Dean et al., 2015). We compare these data to isotopic, chemical and biotic proxies preserved in the lake's annually-varved sediments. Nar Gölü underwent a 3 m lake-level fall between 2000 and 2010, and δ18O in both water and carbonates is correlated with this lake-level fall, responding to the change in water balance. Over the same period, sedimentary diatom assemblages responded via changes in habitat availability and mixing regime, while conductivity inferred from diatoms showed a rise in inferred salinity, although with a non-linear response to hydro-climatic forcing. There were also non-linear shifts in carbonate mineralogy and elemental chemistry. Building on the relationship between lake water balance and the sediment isotope record, we calibrated sedimentary δ18O against local meteorological records to derive a P/E drought index for central Anatolia. Application to of this to the longer sediment core isotope record from Nar Gölü (Jones et al. 2006) highlights major drought events over the last 600 years (Yiǧitbaşıoǧlu et al., 2015). Although this lacustrine record offers an archive of annually-dated, decadally-averaged hydro-climatic change, there were also times of non-linear lake response to climate. Robust reconstruction therefore requires understanding of physical processes as well as application of statistical correlations. Dean, J.R., Eastwood, W.J., Roberts, N., Jones, M.D., Yiǧitbaşıoǧlu, H., Allcock, S.L., Woodbridge, J., Metcalfe, S.E. and Leng, M.J. (2015) Tracking the hydro

  12. Salt lakes of La Mancha (Central Spain): A hot spot for tiger beetle (Carabidae, Cicindelinae) species diversity

    PubMed Central

    Rodríguez-Flores, Paula C.; Gutiérrez-Rodríguez, Jorge; Aguirre-Ruiz, Ernesto F.; García-París, Mario

    2016-01-01

    Abstract The tiger beetle assemblage of the wetlands of La Mancha (central Spain) comprises nine species: Calomera littoralis littoralis, Cephalota maura maura, Cephalota circumdata imperialis, Cephalota dulcinea, Cicindela campestris campestris, Cicindela maroccana, Cylindera paludosa, Lophyra flexuosa flexuosa, and Myriochila melancholica melancholica. This assemblage represents the largest concentration of tiger beetles in a single 1º latitude / longitude square in Europe. General patterns of spatial and temporal segregation among species are discussed based on observations of 1462 specimens registered during an observation period of one year, from April to August. The different species of Cicindelini appear to be distributed over space and time, with little overlapping among them. Three sets of species replace each other phenologically as the season goes on. Most of the species occupy drying or dried salt lakes and salt marshes, with sparse vegetation cover. Spatial segregation is marked in terms of substrate and vegetation use. Calomera littoralis and Myriochila melancholica have been observed mainly on wet soils; Cephalota circumdata on dry open saline flats; Cephalota dulcinea and Cylindera paludosa in granulated substrates with typical halophytic vegetation; Cephalota maura is often present in man-modified areas. Cephalota circumdata and Cephalota dulcinea are included as species of special interest in the list of protected species in Castilla–La Mancha. Conservation problems for the Cicindelini assemblage arise from agricultural activities and inadequate use of sport vehicles. Attempts at restoring the original habitat, supressing old semi-industrial structures, may affect the spatial heterogeneity of the lakes, and have an effect on Cicindelinae diversity. PMID:27006617

  13. Holocene environment of Central Kamchatka, Russia: Implications from a multi-proxy record of Two-Yurts Lake

    NASA Astrophysics Data System (ADS)

    Hoff, Ulrike; Biskaborn, Boris K.; Dirksen, Veronika G.; Dirksen, Oleg; Kuhn, Gerhard; Meyer, Hanno; Nazarova, Larisa; Roth, Alexandra; Diekmann, Bernhard

    2015-11-01

    Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtochnoe in Russian) was chosen as the main scientific target area to decipher Holocene climate variability on Kamchatka. The 5 × 2 km large and 26 m deep lake is of proglacial origin and situated on the eastern flank of Sredinny Ridge at the northwestern end of the Central Kamchatka Valley, outside the direct influence of active volcanism. Here, we present results of a multi-proxy study on sediment cores, spanning about the last 7000 years. The general tenor of the TYL record is an increase in continentality and winter snow cover in conjunction with a decrease in temperature, humidity, and biological productivity after 5000-4500 cal yrs BP, inferred from pollen and diatom data and the isotopic composition of organic carbon. The TYL proxy data also show that the late Holocene was punctuated by two colder spells, roughly between 4500 and 3500 cal yrs BP and between 1000 and 200 cal yrs BP, as local expressions of the Neoglacial and Little Ice Age, respectively. These environmental changes can be regarded as direct and indirect responses to climate change, as also demonstrated by other records in the regional terrestrial and marine realm. Long-term climate deterioration was driven by decreasing insolation, while the short-term climate excursions are best explained by local climatic processes. The latter affect the configuration of atmospheric pressure systems that control the sources as well as the temperature and moisture of air masses reaching Kamchatka.

  14. Rock magnetic and geochemical proxies for iron mineral diagenesis in a tropical lake: Lago Verde, Los Tuxtlas, East Central Mexico

    NASA Astrophysics Data System (ADS)

    Ortega, Beatriz; Caballero, Margarita; Lozano, Socorro; Vilaclara, Gloria; Rodríguez, Alejandro

    2006-10-01

    Magnetic and non-magnetic mineral analyses were conducted on a lacustrine sequence from Lago Verde in the tropical coast along the Gulf of Mexico that covers the last 2000 years. The site witnessed the transformation of the environment since the early Olmec societies until forest clearance in the last century. Through these analyses we investigated the processes that affected the magnetic mineralogy in order to construct a model of past environmental changes, and compare this model with the archeological record and inferred climatic changes in the northern hemisphere of tropical America. Volcanic activity has played a major influence on sediment magnetic properties, as a purveyor of Ti-magnetites/Ti-maghemites, and as a factor of instability in the environment. Anoxic reductive conditions are evident in most of Lago Verde's sedimentary record. Direct observations of magnetic minerals and ratios of geochemical (Fe, Ti), and ferrimagnetic ( χf) and paramagnetic ( χp) susceptibility ( χ) data, are used as parameters for magnetite dissolution ( χp/ χ, Fe/ χf), and precipitation ( χf/Ti) of magnetic minerals. Intense volcanic activity and anoxia are recorded before A.D. 20, leading to the formation of framboidal pyrite. Increased erosion, higher evaporation rates, lower lake levels, anoxia and reductive diagenesis in non-sulphidic conditions are inferred for laminated sediments between A.D. 20-850. This deposit matches the period of historical crisis and multiyear droughts that contributed to the collapse of the Maya civilization. Dissolution of magnetite, a high organic content and framboidal pyrite point to anoxic, sulphidic conditions and higher lake levels after A.D. 850. Higher lake levels in Lago Verde broadly coincide with the increased precipitation documented during the Medieval Warm Period (A.D. 950-1350) in the northern tropical and subtropical regions of the American continent. For the Little Ice Age (A.D. 1400-1800), the relatively moist conditions

  15. Geochemical proxies and millennial-scale climate variability during MIS 3 at Lake Chalco, central Mexico

    NASA Astrophysics Data System (ADS)

    Torres, E.; Lozano, S.; Roy, P.; Ortega, B.; Caballero, M.

    2013-05-01

    The Basin of Mexico (20N, 99W; 2240 m.a.s.l.) is present at the northern limit of the American tropics and is surrounded by up to 5400 m high mountains. The Lake Chalco is situated at the southern part of the basin and spreads over 120 km2. The precipitation in the modern era is influenced by the seasonal displacement of the Intertropical Convergence Zone and the high-pressure belt located at about 35 N. Five cores were drilled (up to 122.5 m depth) in order to document climate variability in paleohydrological conditions during the late Quaternary. The age model includes several 14C dates and tephra layers present in the upper 25 m of the core. We documented millennial-scale events during MIS 3 based on geochemical data (total organic carbon (TOC), total inorganic carbon (TIC), C/N ratio) and abundance of charcoal particles. By temporal correlation with GISP2 core we founded that Greenland interstadials match with TOC percentages suggesting wet conditions while stadials match with high TIC percentages and high charcoal concentrations suggesting dry conditions. We compared our data with speleothem records (δ18O) from Fort Station Cave (New Mexico) and Terciopelo Cave (Costa Rica), our preliminary results indicate that Chalco record has a similar climatic signal as Terciopelo Cave, both presented wet interstadials and dry stadials which appear to have been regulated by the seasonal migration of the ITCZ.

  16. Age, growth, sexual maturity, and food of channel catfish in central Lake Oahe, 1968-69

    USGS Publications Warehouse

    Starostka, Victor J.; Nelson, William R.

    1974-01-01

    Channel catfish, Ictalurus punctatus, were collected with gill nets, trawl, and trap nets at three localities in Lake Oahe for the study of year-class strength, growth in length and weight, age composition, sexual maturity, and food. Fish were recruited to all the collection gears at age II. Relatively strong year classes were produced in 1962, 1965, and 1966. Youngest fish were captured in the upper end of the Moreau River embayment, which apparently serves as a nursery area. Growth of age 0 fish was poor probably because the growing season was short; optimum spawning temperature were not reached until mid-summer. Growth of age II and older fish reached a peak in 1963 and declined rather steadily in 1964-68. Males began to mature at age VIII, and all fish of both sexes were mature at age XI. The diet changed from zooplankton to fish as channel catfish increased in length; aquatic insects (primarily chironomid larvae and pupae) were important foods for fish of all sizes. Fish less than 300 mm long selected large zooplankters -- Leptodora kindtii and Daphnia spp -- over smaller copepods. Larger channel catfish ate principally yellow perch, Perca flavescens.

  17. Prolonged monsoon droughts and links to Indo-Pacific warm pool: A Holocene record from Lonar Lake, central India

    NASA Astrophysics Data System (ADS)

    Prasad, Sushma; Anoop, A.; Riedel, N.; Sarkar, S.; Menzel, P.; Basavaiah, N.; Krishnan, R.; Fuller, D.; Plessen, B.; Gaye, B.; Röhl, U.; Wilkes, H.; Sachse, D.; Sawant, R.; Wiesner, M. G.; Stebich, M.

    2014-04-01

    Concerns about the regional impact of global climate change in a warming scenario have highlighted the gaps in our understanding of the Indian Summer Monsoon (ISM, also referred to as the Indian Ocean summer monsoon) and the absence of long term palaeoclimate data from the central Indian core monsoon zone (CMZ). Here we present the first high resolution, well-dated, multiproxy reconstruction of Holocene palaeoclimate from a 10 m long sediment core raised from the Lonar Lake in central India. We show that while the early Holocene onset of intensified monsoon in the CMZ is similar to that reported from other ISM records, the Lonar data shows two prolonged droughts (PD, multidecadal to centennial periods of weaker monsoon) between 4.6-3.9 and 2-0.6 cal ka. A comparison of our record with available data from other ISM influenced sites shows that the impact of these PD was observed in varying degrees throughout the ISM realm and coincides with intervals of higher solar irradiance. We demonstrate that (i) the regional warming in the Indo-Pacific Warm Pool (IPWP) plays an important role in causing ISM PD through changes in meridional overturning circulation and position of the anomalous Walker cell; (ii) the long term influence of conditions like El Niño-Southern Oscillation (ENSO) on the ISM began only ca. 2 cal ka BP and is coincident with the warming of the southern IPWP; (iii) the first settlements in central India coincided with the onset of the first PD and agricultural populations flourished between the two PD, highlighting the significance of natural climate variability and PD as major environmental factors affecting human settlements.

  18. Long-term studies (1871-2000) on acidification and recovery of lakes in the Bohemian Forest (central Europe).

    PubMed

    Vrba, Jaroslav; Kopácek, Jirí; Fott, Jan; Kohout, Leos; Nedbalová, Linda; Prazáková, Miroslava; Soldán, Tomás; Schaumburg, Jochen

    2003-07-01

    This paper evaluates long-term changes in the atmospheric depositions of S and N compounds, lake water quality, and biodiversity at eight glacial lakes in the Bohemian Forest over the past 130 years. This time interval covers (i) the 'background' pre-acidification status of the lakes, (ii) a period of changes in the communities that can be partly explained by introduction of fish, (iii) a period of strong lake acidification with its adverse impacts on the communities, (iv) the lake reversal from acidity, which includes the recent status of the lakes. The lake water chemistry has followed-with a characteristic hysteresis-both the sharp increase and decline in the deposition trends of strong anions. Remarkable changes in biota have mirrored the changing water quality. Fish became extinct and most species of zooplankton (Crustacea) and benthos (Ephemeroptera and Plecoptera) retreated due to the lake water acidification. Independent of ongoing chemical reversal, microorganisms remain dominant in the recent plankton biomass as well as in controlling the pelagic food webs. The first signs of the forthcoming biological recovery have already been evidenced in some lakes, such as the population of Ceriodaphnia quadrangula (Cladocera) returning into the pelagial of one lake or the increase in both phytoplankton biomass and rotifer numbers in another lake.

  19. Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries.

    PubMed

    Thevenon, Florian; Graham, Neil D; Chiaradia, Massimo; Arpagaus, Philippe; Wildi, Walter; Poté, John

    2011-12-15

    This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge. Eventually, a new Pb isotope record of sediments from Lake Lucerne identifies the long-term increasing anthropogenic lead pollution after ca. 1500, probably due to the development of metallurgical activities during the High Middle Ages. These data furthermore allows to compare the recent anthropogenic sources of water pollution from three of the largest freshwater lakes of Western Europe (lakes Geneva, Lucerne, and Constance). High increases in Pb and Hg highlight the regional impact of industrial pollution after ca. 1750-1850, and the decrease of metal pollution in the 1980s due to the effects of remediation strategies such as the implementation of wastewater treatment plants (WWTPs). However, at all the studied sites, the recent metal concentrations remain higher than pre-industrial levels. Moreover, the local scale pollution data reveal two highly contaminated sites (>100 μg Pb/g dry weight sediment) by industrial activities, during the late-19th and early-20th centuries (Lake Lucerne) and during the second part of the 20th century (Vidy Bay of Lake Geneva). Overall, the regional scale pollution history inferred from the three large and deep perialpine lakes points out at the pollution of water systems by heavy metals during the last two centuries due to the discharge of industrial effluents. Copyright © 2011 Elsevier B.V. All rights reserved.

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

    NASA Technical Reports Server (NTRS)

    Bills, Bruce G.; De Silva, Shanaka L.; Currey, Donald R.; Emenger, Robert S.; Lillquist, Karl D.; Donnellan, Andrea; Worden, Bruce

    1994-01-01

    Sufficiently large lake loads provide a means of probing rheological stratification of the crust and upper mantle. Lake Minchin was the largest of the late Pleistocene pluvial lakes in the central Andes. Prominent shorelines, which formed during temporary still-stands in the climatically driven lake level history, preserve records of lateral variations in subsequent net vertical motions. At its maximum extent the lake was 140 m deep and spanned 400 km N-S and 200 km E-R. The load of surficial water contained in Lake Minchin was sufficient to depress the crust and underlying mantle by 20-40 m, depending on the subjacent rheology. Any other differential vertical motions will also be recorded as departures from horizontality of the shorelines. We recently conducted a survey of shoreline elevations of Lake Minchin with the express intent of monitoring the hydro-isostatic deflection and tectonic tilting. Using real-time differential Global Positioning System (GPS), we measured topographic profiles across suites of shorelines at 15 widely separated locations throughout the basin. Horizontal and vertical accuracies attained are roughly 30 and 70 cm, respectively. Geomorphic evidence suggests that the highest shoreline was occupied only briefly (probably less than 200 years) and radiocarbon dates on gastropod shells found in association with the shore deposits constrain the age to roughly 17 kyr. The basin-side pattern of elevations of the highest shoreline is composed of two distinct signals: (27 +/- 1) m of hydro-isostatic deflection due to the lake load, and a planar tilt with east and north components of (6.8 +/- 0.4) 10(exp -5) and 9-5.3 +/- 0.3) 10(exp -5). This rate of tilting is too high to be plausibly attributed to steady tectonism, and presumably reflects some unresolved combination of tectonism plus the effects of oceanic and lacustrine loads on a laterally heterogeneous substrate. The history of lake level fluctuations is still inadequately known to allow

  1. High Lytic Infection Rates but Low Abundances of Prokaryote Viruses in a Humic Lake (Vassivière, Massif Central, France)▿

    PubMed Central

    Pradeep Ram, A. S.; Rasconi, S.; Jobard, M.; Palesse, S.; Colombet, J.; Sime-Ngando, T.

    2011-01-01

    We explored the abundance and infection rates of viruses on a time series scale in the euphotic zone of the humic mesotrophic Lake Vassivière (Massif Central, France) and compared them to nonhumic lakes of contrasting trophy (i.e., the oligomesotrophic Lake Pavin and the eutrophic Lake Aydat) located in the same geographical region and sampled during the same period. In Lake Vassivière, the abundances of virus-like particles (range, 1.7 × 1010 to 2.6 × 1010 liter−1) were significantly (P < 0.001) lower than in Lakes Pavin and Aydat. The percentage of virus-infected prokaryotic cells (mean, 18.0%) was significantly higher (P < 0.001) in Vassivière than in Pavin (mean, 11.5%) and Aydat (mean, 9.7%). In Vassivière, the abundance of prokaryotes was a good predictor (r = 0.78, P < 0.001) of the number of virus-like particles, while the potential grazing rate from heterotrophic nanoflagellates was positively correlated to the viral infection rate (r = 0.75, P < 0.001; n = 20), indicating the prevalence of cycling interactions among viruses, prokaryotes, and grazers, which is in agreement with past experiments. The absence of correlation between chlorophyll a concentrations (Chl) and viral parameters suggested that the resources for the lytic activity of viruses in Vassivière were mainly under allochthonous control, through host activity. Indeed, compilation of data obtained from several nonhumic lakes in the French Massif Central revealed that Chl was positively correlated to the abundance of virus-like particles at concentrations above 0.5 μg Chl liter−1 and negatively at concentrations below 0.5 μg Chl liter−1, suggesting that phytoplankton-derived resources could force prokaryotic growth to attain a certain threshold level when the host availability is sufficient to boost the proliferation of viruses. Therefore, based on the high level of lytic infection rates in Lake Vassivière, we conclude that viruses are key agents for prokaryotic mortality and

  2. 5,000 years of water level changes infered from ostracod assemblages in a lowland lake in Romania (Central Eastern Europe)

    NASA Astrophysics Data System (ADS)

    Iepure, Sanda; Hutchinson, Simon; Namiotko, Tadeusz; Feurdean, Angelica

    2014-05-01

    Oscillations of lake levels in Central Eastern Europe during the Holocene are crucial records of past regional climatic conditions reflecting the balance between evaporation and precipitation in their catchment. Lake Stiucii (38 ha, 10 m depth) is located in Transylvanian Plain (NW Romania) at 296 m asl. A recently extracted sediment core from the central part of the lake provides the first ostracod sediment record of the lake water level fluctuations in this region covering the last 5000 cal years BP. The sediment sequence yielded approximately 1600 valves of 18 freshwater and halophile ostracod species of 11 genera. The most abundant and frequent in the entire record were Heterocypris salina (Brady 1868), Limnocythere inopinata (Baird 1843) and Plesiocypridopsis newtoni (Brady & Robertson 1870) (abundance range between 16-25%). The ostracod assemblages also show a marked variability in diversity and abundance over the past 5000 years, which appear to closely follow water level oscillations. The assemblages indicate three periods of low diversity and density of ostracods primarily represented by Candonidae between (i) 3800 and 3150 cal yr BP, (ii) 2900 and 2400 cal yr BP and (iii) 1600 and 1200 cal yr BP and probably reflect a response to low lake water levels. This inference is supported by the deposition of gyttja and low Zr concentrations. The dominance of Cyclocypris ovum (Jurine, 1820) and Candoninae in a ostracod community of otherwise poor density and diversity between 2200 and 1800 cal yr BP probably reflects littoral environments in the central, deepest part of the present lake. The ostracod assemblages diversified (up to 10 species) between 1100 and 250 cal yr BP and are dominated by co-occurrences of halophile species e.g. Heterocypris salina and Plesiocypridopsis newtoni until 700 cal yr BP, suggesting increased supply of salty water into the lake by salt springs. Thereafter Limnocythere inopinata, a typical shallow water species (<10 m) is dominant

  3. Organic Carbon Dynamics beyond the Perspective of Monitoring: Impact of Historical Landscape Utilization on the Past Lake-Water Carbon Trajectory in Central Boreal Sweden

    NASA Astrophysics Data System (ADS)

    Meyer-Jacob, C.; Tolu, J.; Bigler, C.; Bindler, R.

    2014-12-01

    To date, the key drivers behind the recent observed increase in organic carbon (OC) concentrations in surface waters are still controversial. The lack of long-term monitoring data - over centuries and millennia - leaves us with an ambiguous understanding of the past trajectory of OC concentrations in surface waters, and inhibits a better mechanistic understanding of past and a reliable prediction of future changes in OC levels.By using a paleolimnological approach, we reconstructed past lake-water total organic carbon (TOC) concentrations in lakes across the boreal landscape of central Sweden. Reconstructions are based on a transfer function between visible near-infrared spectra of surface sediments and the corresponding TOC concentration in the water column. Potential drivers behind changes in TOC were determined by a multi-proxy analysis of one of the studied lake sediment records including organic and inorganic geochemistry as well as biological proxies (pollen, diatoms).Our results show a significant decrease in lake-water TOC beginning already ~550 years ago. This decline continued until the mid-20th century when TOC concentrations started to increase again. These dynamics in TOC coincide with changes in proxies indicating catchment disturbance by human activities. The chronology of these changes corresponds to the expansion and decline of a landscape-wide system of summer forest grazing and farming in central Sweden from the 15th century to the turn of the 20th century. Frequent grazing and exploitation of forests and mires reduce aboveground vegetation and physically disturb soils. This further affects the carbon cycling by enhancing carbon turnover, reducing the thickness of organic soils and consequently altering the transport of OC from the catchment to lakes.Our findings suggest that recent changes in lake-water TOC in Sweden are strongly associated with historical patterns in land use and not only on-going changes in climate or sulfur deposition.

  4. Chemical and biotic characteristics of prairie lakes and large wetlands in south-central North Dakota—Effects of a changing climate

    USGS Publications Warehouse

    Mushet, David M.; Goldhaber, Martin B.; Mills, Christopher T.; McLean, Kyle I.; Aparicio, Vanessa M.; McCleskey, R. Blaine; Holloway, JoAnn M.; Stockwell, Craig A.

    2015-09-28

    The climate of the prairie pothole region of North America is known for variability that results in significant interannual changes in water depths and volumes of prairie lakes and wetlands; however, beginning in July 1993, the climate of the region shifted to an extended period of increased precipitation that has likely been unequaled in the preceding 500 years. Associated changing water volumes also affect water chemical characteristics, with potential effects on fish and wildlife populations. To explore the effect of changing climate patterns, in 2012 and 2013, the U.S. Geological Survey revisited 167 of 178 prairie lakes and large wetlands of south-central North Dakota that were originally sampled in the mid-1960s to mid-1970s. During the earlier sampling period, these lakes and wetlands displayed a great range of chemical characteristics (for example, specific conductance ranged from 365 microsiemens per centimeter at 25 degrees Celsius to 70,300 microsiemens per centimeter at 25 degrees Celsius); however, increased water volumes have resulted in greatly reduced variation among lakes and wetlands and a more homogeneous set of chemical conditions defined by pH, specific conductance, and concentrations of major cations and anions. High concentrations of dissolved solids previously limited fish occurrence in many of the lakes and wetlands sampled; however, freshening of these lakes and large wetlands has allowed fish to populate and flourish where they were previously absent. Conversely, the freshening of previously saline lakes and wetlands has resulted in concurrent shifts away from invertebrate species adapted to live in these highly saline environments. A shift in the regional climate has changed a highly diverse landscape of wetlands (fresh to highly saline) to a markedly more homogeneous landscape that has reshaped the fish and wildlife communities of this ecologically and economically important region.

  5. Climate change and human occupations in the Lake Daihai basin, north-central China over the last 4500 years: A geo-archeological perspective

    NASA Astrophysics Data System (ADS)

    Xu, Lichen; Liu, Yan; Sun, Qianli; Chen, Jing; Cheng, Peng; Chen, Zhongyuan

    2017-05-01

    High-resolution climate variations since the last 4500 years in the monsoonal-arid transition zone of north-central China were revealed through the integration of proxies from sediment cores in the Lake Daihai basin. Human occupations in the lake basin deduced from archeological findings and historical literatures were then incorporated into the climate sequence to demonstrate the patterns of human responses to the climate changes, and the recent anthropogenic effects. It indicated that: (1) Climate dominated human-environment adaptations prevailed prior to ∼2700 cal yr BP. An amicable climate setting before ∼4100 cal yr BP would facilitate the growth of the Laohushan Culture (LC) in the lake basin, while a pronounced deterioration of water thermal condition after that had led to human exodus and the collapse of the LC. The reduced human activity in the lake basin indicated at ∼3800-3500 cal yr BP and a subsequent cultural blank at ∼3500-2700 cal yr BP, were both in response to the climate and lake level fluctuations during ∼3800-2800 cal yr BP. (2) Transition to a positive human adaptation was seen at ∼2700-1100 cal yr BP, represented by the exploitation of arable land for cultivation and animal husbandry as the lake contracted. (3) An increasing human presence that affected environmental processes became more severe over the last ∼1100 cal yr BP. This was basically due to the ongoing lake shore reclamation for cropping, and more recently heavy metals emissions from fossil fuel combustion and local industries.

  6. Role of lake regulation on glacier-fed rivers in enhancing salmon productivity: the Cook Inlet watershed, south-central Alaska, USA

    NASA Astrophysics Data System (ADS)

    Dorava, Joseph M.; Milner, Alexander M.

    2000-10-01

    Rivers fed by glaciers constitute a major part of the freshwater runoff into the Cook Inlet basin of south-central Alaska. This basin is very important to the economy of the State of Alaska because it is home to more than half of the population and it supports multi-million dollar commercial, subsistence and sport fisheries. Hence an understanding of how glacial runoff influences biological productivity is important for managing rivers that drain into Cook Inlet. This paper examines the ways in which the regulation of glacier-fed rivers by proglacial lakes affects salmon productivity, with particular reference to the Kenai River. Salmon escapement per unit channel length on the Kenai River is between two and ten times that found for rain-and-snowmelt dominated rivers and glacier-fed rivers lacking lake regulation.Lakes are shown to influence biological processes in glacier-fed rivers by attenuating peak flows, sustaining high flows throughout the summer, supplementing winter low flows, settling suspended sediment, and increasing river temperatures. Downstream from large lakes, glacier-fed rivers are less disturbed, channels are relatively stable and have well-developed salmonid habitats. The positive influences are indicated by the high diversity and abundances of benthic macroinvertebrates, which are important food resources for juvenile salmonids. High summer flows allow access for up-river salmon runs and lakes also provide both overwintering and rearing habitat.

  7. Extreme events in the sedimentary record of maar Lake Pavin: Implications for natural hazards assessment in the French Massif Central

    NASA Astrophysics Data System (ADS)

    Chassiot, Léo; Chapron, Emmanuel; Di Giovanni, Christian; Albéric, Patrick; Lajeunesse, Patrick; Lehours, Anne-Catherine; Meybeck, Michel

    2016-06-01

    A set of sedimentary cores, high resolution swath bathymetry and subbottom profiler data provides new insights on sedimentary processes in meromictic maar Lake Pavin, France. Three sedimentary environments (i.e., littoral, plateau and basin) have been identified in the lake from sediment composition using bulk organic geochemistry and the analysis of hydroacoustic images. Various forms of rapidly deposited layers (RDLs) have been identified and radiocarbon dated. An up to date stratigraphy of sedimentary events matching coeval RDLs across the lake is presented and illustrates a wide range of natural hazards linked to Lake Pavin during the last 2000 years. In AD 600, a sudden lake outburst triggered a slump deposit along with a 9 m lake-level drop that drove shifts in sedimentary organic matter composition. Outside the lake, outburst flood deposits have been described downstream and provide sedimentary evidence for this event. The lake-level drop also favored the generation of gravity reworking processes, as shown by (1) a regional earthquake-triggered large slope failure on the plateau connected to a mass-wasting deposit in the basin dated to AD 1300, and (2) a succession of turbidites in AD 1825 and AD 1860 contemporaneous to two historic earthquakes, suggesting that this lake is sensitive to earthquakes with a minimum epicentral intensity of V. Finally, past observations of lake water color changes in AD 1783 and AD 1936, similar to reports in other meromictic lakes, match iron-rich deposits identified in maar lake sediments and suggest that Lake Pavin could have undergone limnic eruptions.

  8. Climate and environmental changes over the past 150 years inferred from the sediments of Chaiwopu Lake, central Tianshan Mountains, northwest China

    NASA Astrophysics Data System (ADS)

    Ma, Long; Wu, Jinglu; Abuduwaili, Jilili

    2013-04-01

    We used a 55-cm sediment core from shallow Chaiwopu Lake in the central Tianshan Mountains of Xinjiang, northwest China, to investigate climate and environmental changes in this arid region over the past ~150 years. The core was dated using 137Cs. We compared temporal changes in several sediment variables with recent meteorological and tree-ring records. Organic matter had a positive correlation with the Palmer Drought Severity Index in the central Tianshan Mountains, and the δ13C of organic matter had a positive correlation with regional temperature. We applied constrained incremental sum-of-squares cluster analysis to element concentrations in the core and identified three distinct zones: (1) 55-46 cm, ~1860-1910, (2) 46-26 cm, ~1910-1952, and (3) 26-0 cm, 1952-present. Between 1880 and 1910 AD, following the Little Ice Age (LIA), the sediment environment was relatively stable, climate was cold and dry, and the lake water displayed high salinity, in contrast to conditions during the LIA. During the LIA, westerlies carried more water vapor into Central Asia when the North Atlantic Oscillation was in a negative phase, and encountered the enhanced Siberia High, which probably led to increased precipitation. In the period 1910-1950 AD, the lake was shallow and the regional climate was unstable, with high temperatures and humidity. In the last ~15-20 years, human activities caused an increase in sediment magnetic susceptibility, and heavy metal and total phosphorus concentrations in the sediment were substantially enriched. Mean annual temperature displays a warming trend over the past 50 years, and the lowest temperature was observed in the 1950s. There has been an increase in annual total precipitation since the 1990s. The combined influences of climate and human activity on the lake environment during this period were faithfully recorded in sediments of Chaiwopu Lake. This study provides a scientific basis for environmental management and protection.

  9. Pesticides and nitrate in groundwater underlying citrus croplands, Lake Wales Ridge, central Florida, 1999-2005.

    USGS Publications Warehouse

    Choquette, Anne F.

    2014-01-01

    This report summarizes pesticide and nitrate (as nitrogen) results from quarterly sampling of 31 surficial-aquifer wells in the Lake Wales Ridge Monitoring Network during April 1999 through January 2005. The wells, located adjacent to citrus orchards and used for monitoring only, were generally screened (sampled) within 5 to 40 feet of the water table. Of the 44 citrus pesticides and pesticide degradates analyzed, 17 were detected in groundwater samples. Parent pesticides and degradates detected in quarterly groundwater samples, ordered by frequency of detection, included norflurazon, demethyl norflurazon, simazine, diuron, bromacil, aldicarb sulfone, aldicarb sulfoxide, deisopropylatrazine (DIA), imidacloprid, metalaxyl, thiazopyr monoacid, oxamyl, and aldicarb. Reconnaissance sampling of five Network wells yielded detection of four additional pesticide degradates (hydroxysimazine, didealkylatrazine, deisopropylhydroxyatrazine, and hydroxyatrazine). The highest median concentration values per well, based on samples collected during the 1999–2005 period (n=14 to 24 samples per well), included 3.05 µg/L (micrograms per liter) (simazine), 3.90 µg/L (diuron), 6.30 µg/L (aldicarb sulfone), 6.85 µg/L (aldicarb sulfoxide), 22.0 µg/L (demethyl norflurazon), 25.0 µg/ (norflurazon), 89 µg/ (bromacil), and 25.5 mg/L (milligrams per liter) (nitrate). Nitrate concentrations exceeded the 10 mg/L (as nitrogen) drinking water standard in one or more groundwater samples from 28 of the wells, and the median nitrate concentration among these wells was 14 mg/L. Sampled groundwater pesticide concentrations exceeded Florida’s health-guidance benchmarks for aldicarb sulfoxide and aldicarb sulfone (4 wells), the sum of aldicarb and its degradates (6 wells), simazine (2 wells), the sum of simazine and DIA (3 wells), diuron (2 wells), bromacil (1 well), and the sum of norflurazon and demethyl norflurazon (1 well). The magnitude of fluctuations in groundwater pesticide

  10. Simultaneous abrupt shifts in hydrology and fish assemblage structure in a floodplain lake in the central Amazon.

    PubMed

    Röpke, Cristhiana P; Amadio, Sidinéia; Zuanon, Jansen; Ferreira, Efrem J G; Deus, Cláudia Pereira de; Pires, Tiago H S; Winemiller, Kirk O

    2017-01-10

    Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon.

  11. Simultaneous abrupt shifts in hydrology and fish assemblage structure in a floodplain lake in the central Amazon

    PubMed Central

    Röpke, Cristhiana P.; Amadio, Sidinéia; Zuanon, Jansen; Ferreira, Efrem J. G.; Deus, Cláudia Pereira de; Pires, Tiago H. S.; Winemiller, Kirk O.

    2017-01-01

    Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon. PMID:28071701

  12. Terminal Pleistocene to early Holocene volcanic eruptions at Zuni Salt Lake, west-central New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Onken, Jill; Forman, Steven

    2017-01-01

    Zuni Salt Lake (ZSL) is a large maar in the Red Hill-Quemado volcanic field located in west-central New Mexico in the southwestern USA. Stratigraphic analysis of sections in and around the maar, coupled with optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C dating, indicate that ZSL volcanic activity occurred between ˜13.4 and 9.9 ka and was most likely confined to a ≤500-year interval sometime between ˜12.3 and 11.0 ka. The basal volcanic unit consists of locally widespread basaltic ash fallout interpreted to represent a violent or wind-aided strombolian eruption tentatively attributed to Cerro Pomo, a scoria cone ˜10 km south of ZSL. Subsequent eruptions emanated from vents near or within the present-day ZSL maar crater. Strombolian eruptions of multiple spatter and scoria cones produced basaltic lava and scoria lapilli fallout. Next, a phreatomagmatic eruption created the maar crater and surrounding tephra rim and apron. ZSL eruptions ended with strombolian eruptions that formed three scoria cones on the crater floor. The revised age range of ZSL is younger and more precise than the 190-24 ka 2-sigma age range derived from previous argon dating. This implies that other morphologically youthful, argon-dated volcanoes on the southern margin of the Colorado Plateau might be substantially younger than previously reported.

  13. "A Liberal Arts Education of Enduring Value." Self-Study Report of Lake Forest College for the North Central Association of Colleges and Schools, Commission on Institutions of Higher Education.

    ERIC Educational Resources Information Center

    Gayle, Carol; And Others

    The purpose of Lake Forest College's 1986 self-study was to provide the North Central Association's Commission on Institutions of Higher Education Evaluation Team with materials needed for reaccreditation; to evaluate Lake Forest's efforts to fulfill the purposes and meet the goals established in the new mission statement; and to evaluate the…

  14. Tephra layers from Holocene lake sediments of the Sulmona Basin, central Italy: implications for volcanic activity in Peninsular Italy and tephrostratigraphy in the central Mediterranean area

    NASA Astrophysics Data System (ADS)

    Giaccio, B.; Messina, P.; Sposato, A.; Voltaggio, M.; Zanchetta, G.; Galadini, F.; Gori, S.; Santacroce, R.

    2009-12-01

    We present a new tephrostratigraphic record from the Holocene lake sediments of the Sulmona basin, central Italy. The Holocene succession is represented by whitish calcareous mud that is divided into two units, SUL2 (ca 32 m thick) and SUL1 (ca 8 m thick), for a total thickness of ca 40 m. These units correspond to the youngest two out of six sedimentary cycles recognised in the Sulmona basin that are related to the lake sedimentation since the Middle Pleistocene. Height concordant U series age determinations and additional chronological data constrain the whole Holocene succession to between ca 8000 and 1000 yrs BP. This includes a sedimentary hiatus that separates the SUL2 and SUL1 units, which is roughly dated between <2800 and ca 2000 yrs BP. A total of 31 and 6 tephra layers were identified within the SUL2 and SUL1 units, respectively. However, only 28 tephra layers yielded fresh micro-pumices or glass shards suitable for chemical analyses using a microprobe wavelength dispersive spectrometer. Chronological and compositional constraints suggest that 27 ash layers probably derive from the Mt. Somma-Vesuvius Holocene volcanic activity, and one to the Ischia Island eruption of the Cannavale tephra (2920 ± 450 cal yrs BP). The 27 ash layers compatible with Mt. Somma-Vesuvius activity are clustered in three different time intervals: from ca 2000 to >1000; from 3600 to 3100; and from 7600 to 4700 yrs BP. The first, youngest cluster, comprises six layers and correlates with the intense explosive activity of Mt. Somma-Vesuvius that occurred after the prominent AD 79 Pompeii eruption, but only the near-Plinian event of AD 472 has been tentatively recognised. The intermediate cluster (3600-3100 yrs BP) starts with tephra that chemically and chronologically matches the products from the "Pomici di Avellino" eruption (ca 3800 ± 200 yrs BP). This is followed by eight further layers, where the glasses exhibit chemical features that are similar in composition to the

  15. A multi-proxy intercomparison of environmental change in two maar lake records from central Turkey during the last 14 ka

    NASA Astrophysics Data System (ADS)

    Roberts, C. Neil; Allcock, Samantha L.; Arnaud, Fabien; Dean, Jonathan R.; Eastwood, Warren J.; Jones, Matthew D.; Leng, Melanie J.; Metcalfe, Sarah E.; Malet, Emmanuel; Woodbridge, Jessie; Yiǧitbaşıoǧlu, Hakan

    2016-04-01

    Individual palaeoenvironmental records are a combination of regional-scale (e.g. climatic) and local factors. In order to separate these signals, we compare multiple proxies from two nearby maar lake records, on the assumption that common signals are due to regional-scale forcing. On the other side, we infer that residual signals are likely to be local and site-specific, rather than reflecting regional climate changes. A new core sequence from Nar lake has been dated by varve counting and U-Th as covering the last 13,800 years (Dean et al., 2015; Roberts et al., 2016). Periods of marked dryness are associated with peaks in Mg/dolomite, elevated Diatom-Inferred Electrical Conductivity, an absence of laminated sediments, and low Quercus/chenopod ratios. These conditions occurred during the Late-Glacial stadial, at 4.3-3.7 and 3.2-2.6 ka BP. Wet phases occurred during the early Holocene and again 1.5-0.6 ka, characterised by negative δ18O values, calcite precipitation, high Ca/Sr ratios, a high % of planktonic diatoms, laminated sediments, and high Quercus/chenopod ratios. Comparison with the independently dated record from Eski Acıgöl (Roberts et al., 2001) shows good correspondence for many proxies, especially for δ18O. A ranking of multiple proxies shows the worst correspondence is for clastic lithogenic elements (e.g. Ti flux). Differences between the two lake records are caused by basin infilling at Eski Acıgöl, which fails to register climatic changes during the last 2 ka, and to catchment erosion and increased flux of lithogenic elements into Nar lake; this is catchment-specific and primarily anthropogenic rather than climatic in origin. In separating a regional signal from site-specific "noise", two lakes may therefore be better than one. Dean, J.R. et al. 2015 Eastern Mediterranean hydroclimate over the late glacial and Holocene, reconstructed from the sediments of Nar lake, central Turkey, using stable isotopes and carbonate mineralogy. Quaternary

  16. Remote sensing and GIS investigation of glacial features in the region of Devil's Lake State Park, South-Central Wisconsin, USA

    NASA Astrophysics Data System (ADS)

    Lytwyn, Jennifer

    2010-11-01

    This study utilizes Landsat TM, ASTER and Synthetic Aperture Radar (SAR)-derived DEMs in conjunction with Geographic Information Systems (GIS) in order to reevaluate previously-published interpretations of glacial landforms in and around Devil's Lake State Park, south-central Wisconsin, USA. Devil's Lake sits in a gorge carved into the southern flank of a doubly-plunging syncline known as the Baraboo Hills through which the Wisconsin or some other river flowed prior to the last ice age. During the last glacial maximum about 18,000 B.P., an outlet glacier of the Laurentide Ice Sheet called the Green Bay Lobe extended southward into south-central Wisconsin and left behind extensive glacial landforms such as moraines, drumlins and eskers. During advance of the Green Bay Lobe into the region, Devil's Lake Gorge was plugged at both ends by glacial deposits and resulted in formation of Devil's Lake. The Wisconsin River, if it originally flowed through Devil's Lake Gorge, found a new course to the east of the Baraboo Hills Syncline. This study utilizes the aforementioned remote sensing data to spatially image the following features: (1) Original extent of the Green Bay Lobe, (2) Moraines and streamlined glacial landforms as indicators of ice-flow directions, and (3) Former path of the old Wisconsin or some other river prior to being rerouted by the Green Bay Lobe. GIS analysis is also performed in order to test published interpretations of the regional glacial history. This study confirms that glacial features observed today are consistent with the former advance of the Green Bay Lobe into the area, formation of glacial Lake Wisconsin, plugging of Devil's Lake Gorge by a moraine to form Devil's Lake, and subsequent glacial retreat leading to the breaching of an ice dam and catastrophic flooding by ~ 14,000 years ago. The large aerial coverage of satellite imagery with resolutions up to 15 m are valuable for reevaluating regional interpretations previously based on local

  17. Land Use Controls on Stream and Lake Dissolved Silica Concentrations: A Case Study from the Finger Lakes, Central New York State, USA.

    NASA Astrophysics Data System (ADS)

    Halfman, J. D.

    2014-12-01

    Bedrock geology, climate and time are important controls on chemical weathering and release of dissolved silica. Forested land vs. other land uses was recently hypothesized as another control. The Finger Lakes region is an ideal natural laboratory to test this hypothesis as local watersheds vary in area, bedrock and agricultural to forested land cover in this rural setting. Annual mean dissolved silica data from 11 watersheds in our ongoing monitoring program ranged from 100 to 4,000 μg/L Si, analyzing filtered (0.45 μm) samples by spectrophotometer (molybdate indicator with metol/oxalic acid reagents). Like earlier work, only forested land use (12 to 73%) correlated to the mean silica concentrations (r2 = 0.3), which improves (r2 = 0.6) when a small, primarily (24%) developed watershed is excluded from the correlation. Bedrock (Devonian carbonates, 0 to 8% and clastics, 0 to 99% covered by till) and basin area (10 to 500 km2) did not correlate (r2 <= 0.1). Event and base flow samples of an agricultural (64%) watershed revealed peak to base flow fluctuations in silica concentrations that more closely mimic nitrates and other groundwater solutes than suspended particles, phosphates and other runoff signature parameters. Annual mean epilimnion and hypolimnion dissolved silica data from the 8 easternmost Finger Lakes in our ongoing monitoring program ranged from 250 to 1,500 μg/L Si. Forested cover (30 to 75%) positively correlated to epilimnion silica concentrations (r2 = 0.6). Lake water residence time (1 to 17 yr) negatively correlated to hypolimnion silica concentrations (r2 = 0.5). Agricultural land use, bedrock, and productivity indicators (chlorophyll-a, total phosphate, and secchi disk depth) lacked correlation (r2 <= 0.1). It suggested that land use impacts stream and, surprisingly, lake dissolved silica chemistry. Biogeochemical processes in the lakes like diatom uptake appears to increasingly decrease silica concentrations in lakes with longer residence

  18. Evaluation of the potential of organic geochemical proxies from lake sediments from Central India to reconstruct monsoon variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Sarkar, Saswati; Sachse, Dirk; Wilkes, Heinz; Prasad, Sushma; Brauer, Achim; Strecker, Manfred; Basavaiah, Nathani

    2010-05-01

    A better understanding of the past variations of the Indian Monsoon system, which has a deep societal impact on the subcontinent, is essential to determine its behavior under a changing global climate. We aim to reconstruct the variability of the Indian Monsoon, which has both spatially as well as temporally variable nature, during the last 10,000 years using lipid biomarker abundances and stable isotopes from continuous, high-resolution lake sediments in a climatically sensitive region of Central India. Previous sedimentological and geochemical studies on bulk material from a well dated long lake sediment core covering the last 11,000 years have already shown evidence of rapid changes in lithology, sedimentation rate, paleo lake productivity and supply of terrestrial organic matter. Changes in the abundance of source-specific organic compounds - lipid biomarkers - can be useful for the interpretation of past changes in hydrology and ecosystem of the lake and its catchment area as well as their relation to climatic factors. We have identified a number of suitable biomarker compounds for paleohydrological and environmental reconstruction from surface sediments and short cores. Identified biomarker compounds include both aquatic and terrestrial biomarkers. Among the aquatic biomarkers short chain n-alkanes and phytane, most probably derived from cyanobacteria and microbial biomarkers like moretene, diploptene and other hopenes were present. Additionally long chain n-alkanes from vascular land plants from the lake catchment area were identified. Interestingly, the triterpene lipid tetrahymanol and tetrahymanone was found to be the biomarker of highest concentration in all analyzed surface sediments, with concentrations higher than the ubiquitous short-chain fatty acids. Tetrahymanol is often attributed to certain protozoa and frequently found in hypersaline lakes. However, studies have shown that this lipid can also be found in sizable amounts in phototrophic bacteria

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

    USGS Publications Warehouse

    Schiffer, D.M.

    1996-01-01

    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

  20. The Potential Impact of Increased Phosphorus Loads in Lakes Acting as Heavy Metal Reservoirs: A case study from west-central Indiana

    NASA Astrophysics Data System (ADS)

    McLennan, D. A.; Latimer, J. C.; Smith, E.; Stone, J.

    2015-12-01

    Green Valley Lake is a designated state fishing area in west-central Indiana. Prior to this designation, the lake was a water supply reservoir for the adjacent and now abandoned Green Valley Coal Mine (Operating from 1948-1963). The Green Valley Coal Mine property continues to produce excess acidity despite reclamation efforts. The former mine property and the lake are connected by a channel that discharges acidic drainage directly into Green Valley Lake. To evaluate temporal variability in metal and phosphorus (P) geochemistry, two short cores were collected in spring 2014 (38cm) and spring 2015 (39cm). Metal concentrations were determined by a hand-held X-ray fluorescence analyzer after the samples had been dried and crushed. Approximately 20% of these metal concentrations will be verified by ICP-OES following extraction in 50% aqua regia. Detailed P geochemistry was determined using a sequential extraction technique (SEDEX). The sediments in Green Valley Lake are characterized by heavy metal concentrations that are elevated above typical background levels. These metals tend to be concentrated near the sediment water interface, often 3-5 times greater than the average concentration for the rest of the core, which suggests that they are diagenetically mobile and possibly diffusing out of the sediments under dysoxic to anoxic conditions and returning to the sediments under oxic conditions. Total sedimentary P averages 57 umol/g, but oscillates between 20 - 110 umol/g. The most dramatic shift in the detailed P geochemistry is the significant reduction of mineral P at 15 cm and the increasing importance of oxide-associated and adsorbed P upcore. Diatom assemblages suggest that the lake has become increasingly more eutrophic over time. As nutrient loads continue to increase, the oxygen depleted zone may expand impacting fish populations and changing water geochemistry significantly, in particular, mobilizing heavy metals.

  1. SIMULATION AND VALIDATION OF FISH THERMAL DO HABITAT IN NORTH-CENTRAL US LAKES UNDER DIFFERENT CLIMATE SCENARIOS. (R824801)

    EPA Science Inventory

    Abstract

    Fish habitat in lakes is strongly constrained by water temperature and available dissolved oxygen (DO). Suitable fish habitat for three fish assemblages (cold-, cool-, and warm-water) in Minnesota (US) lakes was therefore determined from simulated daily water ...

  2. SIMULATION AND VALIDATION OF FISH THERMAL DO HABITAT IN NORTH-CENTRAL US LAKES UNDER DIFFERENT CLIMATE SCENARIOS. (R824801)

    EPA Science Inventory

    Abstract

    Fish habitat in lakes is strongly constrained by water temperature and available dissolved oxygen (DO). Suitable fish habitat for three fish assemblages (cold-, cool-, and warm-water) in Minnesota (US) lakes was therefore determined from simulated daily water ...

  3. Atmospheric processes of organic pollutants over a remote lake on the central Tibetan Plateau: implications for regional cycling

    NASA Astrophysics Data System (ADS)

    Ren, Jiao; Wang, Xiaoping; Wang, Chuanfei; Gong, Ping; Yao, Tandong

    2017-01-01

    Atmospheric processes (air-surface exchange, and atmospheric deposition and degradation) are crucial for understanding the global cycling and fate of organic pollutants (OPs). However, such assessments over the Tibetan Plateau (TP) remain uncertain. More than 50 % of Chinese lakes are located on the TP, which exerts a remarkable influence on the regional water, energy, and chemical cycling. In this study, air and water samples were simultaneously collected in Nam Co, a large lake on the TP, to test whether the lake is a secondary source or sink of OPs. Lower concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were observed in the atmosphere and lake water of Nam Co, while the levels of polycyclic aromatic hydrocarbons (PAHs) were relatively higher. Results of fugacity ratios and chiral signatures both suggest that the lake acted as the net sink of atmospheric hexachlorocyclohexanes (HCHs), following their long-range transport driven by the Indian monsoon. Different behaviours were observed in the PAHs, which primarily originated from local biomass burning. Acenaphthylene, acenaphthene, and fluorene showed volatilization from the lake to the atmosphere, while other PAHs were deposited into the lake due to the integrated deposition process (wet/dry and air-water gas deposition) and limited atmospheric degradation. As the dominant PAH compound, phenanthrene exhibited a seasonal reversal of air-water gas exchange, which was likely related to the melting of the lake ice in May. The annual input of HCHs from the air to the entire lake area (2015 km2) was estimated as 1.9 kg yr-1, while input estimated for 15PAHs can potentially reach up to 550 kg yr-1. This study highlights the significance of PAH deposition on the regional carbon cycling in the oligotrophic lakes of the TP.

  4. Significant melting of ice-wedges and formation of thermocirques on hill-slopes of thermokarst lakes in Central Yakutia (Siberia)

    NASA Astrophysics Data System (ADS)

    Séjourné, Antoine; Costard, François; Gargani, Julien; Fedorov, Alexander; Skorve, Johnny

    2013-04-01

    On Earth, permafrost containing a high ice volume (referred as ice-rich) are sensible to climate change, they have been regionally degraded (thermokarst) during the early Holocene climatic optimum forming numerous thermokarst lakes in Central Yakutia (eastern Siberia). Recent temperature increases in the Arctic and Subarctic have been significantly greater than global averages. The frequency and magnitude of terrain disturbances associated with thawing permafrost are increasing in these regions and are thought to intensify in the future. Therefore, understand how is the current development of thermokarst is a critical question. Here, we describe the significant melting of ice-wedges on slopes of thermokarst lakes that leads to formation of amphitheatrical hollows referred as thermocirques. The evolution of thermocirques in Central Yakutia has been little studied and analyzing their formation could help to understand the recent thermokarst in relation to climate change in Central Yakutia. We studied the thermocirques at two scales: (i) field surveys of different thermocirques in July 2009-2010 and October 2012 to examine the processes and origin of melting of ice-wedges and; (ii) photo-interpretation of time series of satellite images (KH-9 Hexagon images of 6-9 m/pixel and GeoEye images of 50 cm/pixel) to study the temporal evolution of thermocirques. The melting of ground-ice on the scarp of thermocirque triggers falls and small mud-flows that induce the retreat of the scarp parallel to itself. Based on field studies and on GeoEye image comparison, we show that their rate of retrogressive growth is 1-2 m/year. On the hill-slopes of lakes, the thermokarst could be initiated by different processes that lead to the uncover and then melting of ice-wedges: thermal erosion by the waves of the ice-rich bluff; active-layer detachment (a form of slope failure linked to detachment of the seasonally thawed upper ground); flowing of water on the slope (precipitation) or

  5. Fluxes of deep CO 2 in the volcanic areas of central-southern Italy

    NASA Astrophysics Data System (ADS)

    Gambardella, Barbara; Cardellini, Carlo; Chiodini, Giovanni; Frondini, Francesco; Marini, Luigi; Ottonello, Giulio; Vetuschi Zuccolini, Marino

    2004-08-01

    Both the shallow (organic-derived) and deep (mantellic-magmatic-metamorphic) fluxes of CO 2 [ ΦCO 2, mass time -1] and specific fluxes of CO 2 [ ϕCO 2 mass time -1 surface -1] dissolving in the shallow groundwaters of the volcanic areas of Amiata, Vulsini-Vico-Sabatini, Albani, Roccamonfina, Vesuvio, Vulture, and Etna were evaluated by partitioning the composed population of total dissolved inorganic carbon in two individual populations and subsequent subtraction of local background population. The flux of deep CO 2 released from the geothermal fields of Piancastagnaio (Amiata), Torre Alfina, Latera, Marta, Bracciano south, Cesano, and Mofete and from the Overall Northern Latium Hydrothermal Reservoir were also evaluated by means of the total surface heat flux and the enthalpy and CO 2 molality of the single liquid phase circulating in each geothermal reservoir. These data suggest that the ϕCO 2 released to the atmosphere varies from 9.5×10 6 to 3.0×10 6 mol year -1 km -2, over the geothermal fields of Bracciano south and Cesano, respectively, and that a total ΦCO 2 of 3.8×10 8 mol year -1 is cumulatively released from the geothermal fields of Torre Alfina, Latera and Cesano extending over an area of only 66 km 2. In addition, a flux of ˜2.2×10 11 to 3.8×10 11 mol year -1 of gaseous CO 2 entering the atmosphere is obtained for the entire anomalous area of central Italy, extending from the Tyrrhenian coastline to the Apennine chain (45,000 km 2). Thus terrestrial CO 2 emission in central-southern Italy appears to be a significant carbon source.

  6. Estimation of water storage changes in small endorheic lakes in Burabay National Nature Park (Northern Kazakhstan, Central Asia); the effect of climate change and anthropogenic influences

    NASA Astrophysics Data System (ADS)

    Yapiyev, Vadim; Sagintayev, Zhanay; Verhoef, Anne; Samarkhanov, Kanat; Jumassultanova, Saltanat

    2017-04-01

    Both climate change and anthropogenic activities contribute to deterioration of terrestrial water resources and ecosystems worldwide. It has been observed in recent decades that water-limited steppe regions of Central Asia are among ecosystems found to exhibit enhanced responses to climate variability. In fact, the largest share of worldwide net loss of permanent water extent is geographically concentrated in the Central Asia and Middle East regions attributed to both climate variability/change and human activities impacts. We used a digital elevation model, digitized bathymetry maps and high resolution Landsat images to estimate the areal water cover extent and volumetric storage changes in small terminal lakes in Burabay National Nature Park (BNNP), located in Northern Central Asia, for the period 2000-2016. Based on the analysis of long-term climatic data from meteorological stations, hydrometeorological network observations as well as regional climate model projections we evaluate the impacts of past thirty years and future climatic conditions on the water balance of BNNP lake catchments. The anthropogenic water consumption was estimated based on data collected at a local water supply company and regulation authorities. One the one hand historical in-situ observations and future climate projections do not show a significant change in precipitation in BNNP. On the other hand both observations and the model demonstrate steadily rising air temperatures in the area. It is concluded that the long-term decline in water levels for most of these lakes can be largely attributed to climate change (but only via changes in air temperature, causing evaporation to exceed precipitation) and not to direct anthropogenic influences such as increased water withdrawals. In addition, the two largest lakes, showing the highest historical water level decline, do not have sufficient water drainage basin area to sustain water levels under increased evaporation rates.

  7. Hydrochemical and multivariate statistical interpretations of spatial controls of nitrate concentrations in a shallow alluvial aquifer around oxbow lakes (Osong area, central Korea).

    PubMed

    Kim, Kyoung-Ho; Yun, Seong-Taek; Choi, Byoung-Young; Chae, Gi-Tak; Joo, Yongsung; Kim, Kangjoo; Kim, Hyoung-Soo

    2009-07-21

    Hydrochemical and multivariate statistical interpretations of 16 physicochemical parameters of 45 groundwater samples from a riverside alluvial aquifer underneath an agricultural area in Osong, central Korea, were performed in this study to understand the spatial controls of nitrate concentrations in terms of biogeochemical processes occurring near oxbow lakes within a fluvial plain. Nitrate concentrations in groundwater showed a large variability from 0.1 to 190.6 mg/L (mean=35.0 mg/L) with significantly lower values near oxbow lakes. The evaluation of hydrochemical data indicated that the groundwater chemistry (especially, degree of nitrate contamination) is mainly controlled by two competing processes: 1) agricultural contamination and 2) redox processes. In addition, results of factorial kriging, consisting of two steps (i.e., co-regionalization and factor analysis), reliably showed a spatial control of the concentrations of nitrate and other redox-sensitive species; in particular, significant denitrification was observed restrictedly near oxbow lakes. The results of this study indicate that sub-oxic conditions in an alluvial groundwater system are developed geologically and geochemically in and near oxbow lakes, which can effectively enhance the natural attenuation of nitrate before the groundwater discharges to nearby streams. This study also demonstrates the usefulness of multivariate statistical analysis in groundwater study as a supplementary tool for interpretation of complex hydrochemical data sets.

  8. Hydrochemical and multivariate statistical interpretations of spatial controls of nitrate concentrations in a shallow alluvial aquifer around oxbow lakes (Osong area, central Korea)

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Ho; Yun, Seong-Taek; Choi, Byoung-Young; Chae, Gi-Tak; Joo, Yongsung; Kim, Kangjoo; Kim, Hyoung-Soo

    2009-07-01

    Hydrochemical and multivariate statistical interpretations of 16 physicochemical parameters of 45 groundwater samples from a riverside alluvial aquifer underneath an agricultural area in Osong, central Korea, were performed in this study to understand the spatial controls of nitrate concentrations in terms of biogeochemical processes occurring near oxbow lakes within a fluvial plain. Nitrate concentrations in groundwater showed a large variability from 0.1 to 190.6 mg/L (mean = 35.0 mg/L) with significantly lower values near oxbow lakes. The evaluation of hydrochemical data indicated that the groundwater chemistry (especially, degree of nitrate contamination) is mainly controlled by two competing processes: 1) agricultural contamination and 2) redox processes. In addition, results of factorial kriging, consisting of two steps (i.e., co-regionalization and factor analysis), reliably showed a spatial control of the concentrations of nitrate and other redox-sensitive species; in particular, significant denitrification was observed restrictedly near oxbow lakes. The results of this study indicate that sub-oxic conditions in an alluvial groundwater system are developed geologically and geochemically in and near oxbow lakes, which can effectively enhance the natural attenuation of nitrate before the groundwater discharges to nearby streams. This study also demonstrates the usefulness of multivariate statistical analysis in groundwater study as a supplementary tool for interpretation of complex hydrochemical data sets.

  9. Morphogenesis of the Czechowskie Lake as inferred from the sedimentological analysis of limnic, colluvial and glacifluvial deposits (Eastern Pomerania, North Central Poland)

    NASA Astrophysics Data System (ADS)

    Kordowski, Jaroslaw; Błaszkiewicz, Mirosław; Kramkowski, Mateusz; Słowiński, Michał; Tyszkowski, Sebastian; Brauer, Achim; Ott, Florian

    2014-05-01

    Czechowskie Lake is situated in north-central Poland in Tuchola Forest, about 100 kilometers SW away from Gdańsk. In the deepest parts of the lake bottom, there are hidden laminated sediments which hold the Late Glacial and Holcene climatic record. These deposits are subject of detailled work of the joint German-Polish Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association. It has the area of 76,6 ha. Actual water level is at 109,9 m a.s.l. The average depth is 9,59 m, maximal 32 m. The lake occupies a large subglacial channel, reproduced within the glacifluvial sediments of the Pomeranian Phase of the last glaciation. In the widest place it has the width of 1 kilometer. The maximal depth of the channel (counting from the channel edges to the reconstructed deepest lake mineral floor (after removal of the limnic sediments)) may reach 70 meters. Inside of the channel some throughs and small hills do exist which are built of outwash sediments but, considering internal structures, they bear some similarity to the dead ice moraines and kames. The vicinity of the channel consists of two outwash plain levels. The lower one was created on the dead ice blocks. The maximum infilling with the limnic and telmatic sediments reaches over 12 m. In the bottom of the lake there is a marked presence of many overdeepenings with the diameter of dozen or several dozen meters and the depth of up to 10 m with numerous, distinct throughs between them. They favoured the preservation of the lamination in the deepest parts of the lake due to waves hampering and stopping of the density circulation in the lake waterbody. In the colluvial and fluvioglacial deposits there were carried out carefull sedminetological analyses. Limnic sediments were identified by bore holes with preserved undisturbed structure. All done works revealed that some of the glacifluvial deposits were deposited in subglacial conditions in supercritical flow regime. They were

  10. A computational approach to Quaternary lake-level reconstruction applied in the central Rocky Mountains, Wyoming, USA

    NASA Astrophysics Data System (ADS)

    Pribyl, Paul; Shuman, Bryan N.

    2014-07-01

    Sediment-based reconstructions of late-Quaternary lake levels provide direct evidence of hydrologic responses to climate change, but many studies only provide approximate lake-elevation curves. Here, we demonstrate a new method for producing quantitative time series of lake elevation based on the facies and elevations of multiple cores collected from a lake's margin. The approach determines the facies represented in each core using diagnostic data, such as sand content, and then compares the results across cores to determine the elevation of the littoral zone over time. By applying the approach computationally, decisions are made systematically and iteratively using different facies classification schemes to evaluate the associated uncertainty. After evaluating our assumptions using ground-penetrating radar (GPR), we quantify past lake-elevation changes, precipitation minus evapotranspiration (ΔP-ET), and uncertainty in both at Lake of the Woods and Little Windy Hill Pond, Wyoming. The well-correlated (r = 0.802 ± 0.002) reconstructions indicate that water levels at both lakes fell at > 11,300, 8000-5500, and 4700-1600 cal yr BP when ΔP - ET decreased to - 50 to - 250 mm/yr. Differences between the reconstructions are typically small (10 ± 24 mm/yr since 7000 cal yr BP), and the similarity indicates that our reconstruction method can produce statistically comparable paleohydrologic datasets across networks of sites.

  11. Vegetation, climate and lake changes over the last 7000 years at the boreal treeline in north-central Siberia

    NASA Astrophysics Data System (ADS)

    Klemm, Juliane; Herzschuh, Ulrike; Pestryakova, Luidmila A.

    2016-09-01

    Palaeoecological investigations in the larch forest-tundra ecotone in northern Siberia have the potential to reveal Holocene environmental variations, which likely have consequences for global climate change because of the strong high-latitude feedback mechanisms. A sediment core, collected from a small lake (radius ∼100 m), was used to reconstruct the development of the lake and its catchment as well as vegetation and summer temperatures over the last 7100 calibrated years. A multi-proxy approach was taken including pollen and sedimentological analyses. Our data indicate a gradual replacement of open larch forests by tundra with scattered single trees as found today in the vicinity of the lake. An overall trend of cooling summer temperature from a ∼2 °C warmer-than-present mid-Holocene summer temperatures until the establishment of modern conditions around 3000 years ago is reconstructed based on a regional pollen-climate transfer function. The inference of regional vegetation changes was compared to local changes in the lake's catchment. An initial small water depression occurred from 7100 to 6500 cal years BP. Afterwards, a small lake formed and deepened, probably due to thermokarst processes. Although the general trends of local and regional environmental change match, the lake catchment changes show higher variability. Furthermore, changes in the lake catchment slightly precede those in the regional vegetation. Both proxies highlight that marked environmental changes occurred in the Siberian forest-tundra ecotone over the course of the Holocene.

  12. Paleoecological studies at Lake Patzcuaro on the west-central Mexican Plateau and at Chalco in the basin of Mexico

    USGS Publications Warehouse

    Watts, W.A.; Bradbury, J.P.

    1982-01-01

    A 1520-cm sediment core from Lake Patzcuaro, Michoacan, Mexico, is 44,000 yr old at the base. All parts of the core have abundant pollen of Pinus (pine), Alnus (alder), and Quercus (oak) with frequent Abies (fir). The interval dated from 44,000 to 11,000 yr ago has a homogeneous flora characterized by abundant Juniperus (juniper) pollen and frequent Artemisia (sagebrush). It is believed to represent an appreciably drier and colder climate than at present. The Holocene at Lake Patzcuaro is characterized by a moderate increase in Pinus pollen and the loss of Juniperus pollen, as the modern type of climate succeeded. Alnus was abundant until about 5000 yr ago; its abrupt decrease with the first appearance of herbaceous weed pollen may reflect the cutting of lake-shore and stream-course alder communities for agricultural purposes, or it may simply reflect a drying tendency in the climate. Pollen of Zea (corn) appears at Lake Patzcuaro along with low peaks of chenopod and grass pollen at 3500 yr B.P. apparently recording a human population large enough to modify the natural environment, as well as the beginning of agriculture. A rich aquatic flora in this phase suggests eutrophication of the lake by slope erosion. In the most recent period corn is absent from the sediments, perhaps reflecting a change in agricultural practices. The environment changes at Lake Patzcuaro are similar to and correlate with those in the Cuenca de Mexico, where diatom stratigraphy from the Chalco basin indicates fluctuations in lake levels and lake chemistry in response to variations in available moisture. Before 10,000 yr ago climates there were cool and dry, and the Chalco basin was occupied by a shallow freshwater marsh that drained north to Lake Texcoco, where saline water accumulated by evaporation. Increases in effective moisture and possible melting of glaciers during the Holocene caused lake levels to rise throughout the Cuenca de Mexico, and Lake Texcoco flooded the Chalco basin with

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

    SciTech Connect

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

    1988-01-01

    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.

  14. 3D Variations in Sediment Architecture in the Central Basin of Lake Malawi from the SEGMeNT Active-Source Experiment

    NASA Astrophysics Data System (ADS)

    Eatmon, A.; Accardo, N. J.; Shillington, D. J.; Onyango, E. A.; Scholz, C. A.; McCartney, T.; Ebinger, C. J.; Gaherty, J. B.; Nyblade, A.; Chindandali, P. R. N.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

    2016-12-01

    A fundamental question in geophysics is how continental rifts evolve from initiation to breakup. Our study aims to elucidate the controls on early-stage rifting utilizing recently collected active-source wide-angle refraction data from the weakly extended Malawi Rift, which is composed of a series of border-fault bound basins whose polarity reverses along strike. Our study focuses on the Central Basin of Lake Malawi. The Central Basin is bounded to the west by the 1,000 m high Central Basin border fault and contains a series of enigmatic structures within the basin. To constrain the thickness of synrift and pre-rift sediments and upper crustal structure associated with intrabasinal structure, we have undertaken 3D velocity modeling of the Central Basin using new active-source data acquired in Lake Malawi (Nyasa) as a part of the SEGMeNT project. We picked first arrivals on shots recorded on 12 "lake" bottom seismometers resulting in over 38,000 unique picks with maximum offsets of 90 km. We then inverted these picks using the First Arrival Seismic Tomography (FAST) package for the 3D structure. The resulting model spans 80 km north to south, 50 km east to west, and 10 km in depth. We also apply strict quality control measures to ensure only robust picks are utilized in the inversion. Starting models are built from smoothed inversion of picks at close offsets to ensure that shallow structure is not mapped to depth. Our results indicate a marked transition in the character of sedimentary basins within the Central Basin. Sediments thicken to the west at the southern end of the Central Basin reaching a maximum thickness of 4.5 km and in contrast, sediments thicken to the east at the northern end near Manda, Tanzania and reach a maximum thickness of 4.0 km. This may indicate that the west dipping border fault that bounds the eastern side of the basin to the north influences the Central Basin at its northern end. We image a linear, high-velocity feature that extends from

  15. Biogeochemical processes involving dissolved CO2 and CH4 at Albano, Averno, and Monticchio meromictic volcanic lakes (Central-Southern Italy)

    NASA Astrophysics Data System (ADS)

    Cabassi, Jacopo; Tassi, Franco; Vaselli, Orlando; Fiebig, Jens; Nocentini, Matteo; Capecchiacci, Francesco; Rouwet, Dmitri; Bicocchi, Gabriele

    2013-01-01

    This paper focuses on the chemical and isotopic features of dissolved gases (CH4 and CO2) from four meromictic lakes hosted in volcanic systems of Central-Southern Italy: Lake Albano (Alban Hills), Lake Averno (Phlegrean Fields), and Monticchio Grande and Piccolo lakes (Mt. Vulture). Deep waters in these lakes are characterized by the presence of a significant reservoir of extra-atmospheric dissolved gases mainly consisting of CH4 and CO2. The δ13C-CH4 and δD-CH4 values of dissolved gas samples from the maximum depths of the investigated lakes (from -66.8 to -55.6 ‰ V-PDB and from -279 to -195 ‰ V-SMOW, respectively) suggest that CH4 is mainly produced by microbial activity. The δ13C-CO2 values of Lake Grande, Lake Piccolo, and Lake Albano (ranging from -5.8 to -0.4 ‰ V-PDB) indicate a significant CO2 contribution from sublacustrine vents originating from (1) mantle degassing and (2) thermometamorphic reactions involving limestone, i.e., the same CO2 source feeding the regional thermal and cold CO2-rich fluid emissions. In contrast, the relatively low δ13C-CO2 values (from -13.4 to -8.2 ‰ V-PDB) of Lake Averno indicate a prevalent organic CO2. Chemical and isotopic compositions of dissolved CO2 and CH4 at different depths are mainly depending on (1) CO2 inputs from external sources (hydrothermal and/or anthropogenic); (2) CO2-CH4 isotopic exchange; and (3) methanogenic and methanotrophic activity. In the epilimnion, vertical water mixing, free oxygen availability, and photosynthesis cause the dramatic decrease of both CO2 and CH4 concentrations. In the hypolimnion, where the δ13C-CO2 values progressively increase with depth and the δ13C-CH4 values show an opposite trend, biogenic CO2 production from CH4 using different electron donor species, such as sulfate, tend to counteract the methanogenesis process whose efficiency achieves its climax at the water-bottom sediment interface. Theoretical values, calculated on the basis of δ13C-CO2 values, and

  16. The Interdependence of Lake Ice and Climate in Central North America. [correlation between freeze/than cycles of lakes and regional weather variations

    NASA Technical Reports Server (NTRS)

    Jelacic, A. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. A comparison of lake freeze transition zone migration with the movement of large pressure centers reveals the following consistencies: (1) polar continental cyclones originate within and/or travel along the trend of the transition zone; (2) polar continental anticyclones fail to cross the transition zone; (3) polar outbreak anticyclones pass through the transition zone, apparently unaffected. In addition, storm centers associated with the transition zone undergo significant intensification manifest by a deepening of the pressure through and increased precipitation outside the zone.

  17. Phylogenetic Analysis of a Microbialite-Forming Microbial Mat from a Hypersaline Lake of the Kiritimati Atoll, Central Pacific

    PubMed Central

    Schneider, Dominik; Arp, Gernot; Reimer, Andreas; Reitner, Joachim; Daniel, Rolf

    2013-01-01

    On the Kiritimati atoll, several lakes exhibit microbial mat-formation under different hydrochemical conditions. Some of these lakes trigger microbialite formation such as Lake 21, which is an evaporitic, hypersaline lake (salinity of approximately 170‰). Lake 21 is completely covered with a thick multilayered microbial mat. This mat is associated with the formation of decimeter-thick highly porous microbialites, which are composed of aragonite and gypsum crystals. We assessed the bacterial and archaeal community composition and its alteration along the vertical stratification by large-scale analysis of 16S rRNA gene sequences of the nine different mat layers. The surface layers are dominated by aerobic, phototrophic, and halotolerant microbes. The bacterial community of these layers harbored Cyanobacteria (Halothece cluster), which were accompanied with known phototrophic members of the Bacteroidetes and Alphaproteobacteria. In deeper anaerobic layers more diverse communities than in the upper layers were present. The deeper layers were dominated by Spirochaetes, sulfate-reducing bacteria (Deltaproteobacteria), Chloroflexi (Anaerolineae and Caldilineae), purple non-sulfur bacteria (Alphaproteobacteria), purple sulfur bacteria (Chromatiales), anaerobic Bacteroidetes (Marinilabiacae), Nitrospirae (OPB95), Planctomycetes and several candidate divisions. The archaeal community, including numerous uncultured taxonomic lineages, generally changed from Euryarchaeota (mainly Halobacteria and Thermoplasmata) to uncultured members of the Thaumarchaeota (mainly Marine Benthic Group B) with increasing depth. PMID:23762495

  18. Relationships between the parasites of some wild and cultured fishes in two lakes and a fish farm in central Finland.

    PubMed

    Valtonen, E T; Koskivaara, M

    1994-02-01

    A total of 526 Atlantic salmon and 500 brown trout from a fish farm were studied for parasites, as were 272 roach, 251 perch and 150 whitefish from the lake which formed the water source, and 196 roach and 136 perch from the effluent recipient lake. The cultured fish harboured 14 parasite species, of which most were protozoan generalist parasites. Nine species were found on salmon and 12 on brown trout. Epizootically the most important species were Ichthyobodo necator, Chilodonella cyprini and Ichthyophthirius multifiliis. The mean number of species per studied fish was 0.71 for salmon and 0.61 for brown trout. The seasonal occurrences of the ectoparasites were found to be irregular due to preventative bathing of the fish. The wild whitefish harboured 19 parasite species, roach 41 and perch 33. The proportions of the parasite species common to both wild and cultured fishes were 17% of the species from roach, 36% of those from perch and 47% of the species from whitefish. Jaccard's similarity index, indicating similarities between wild and farmed fish, was highest between whitefish and brown trout. It was concluded that the source of parasites in the fish farm is the water supplying lake, but the farm itself was unlikely to effect the fish parasite fauna of the water recipient lake, although some ectoparasites, which had high prevalences in this lake, could originate from the farm. The high standard of maintenance and hygiene in this farm kept problems caused by parasites under control.

  19. Evaluation of 11 equations for determining evaporation for a small lake in the North Central United States

    USGS Publications Warehouse

    Winter, T.C.; Rosenberry, D.O.; Sturrock, A.M.

    1995-01-01

    Eleven equations for calculating evaporation were compared with evaporation determined by the energy budget method for Williams Lake, Minnesota. Data were obtained from instruments on a raft, on land near the lake, and at a weather station 60 km south of the lake. The comparisons were based on monthly values for the open-water periods of 5 years, a total of 22 months. A modified DeBruin-Keijman, Priestley-Taylor, and a modified Penman equation resulted in monthly evaporation values that agreed most closely with energy budget values. To use these equations, net radiation, air temperature, wind speed, and relative humidity need to be measured near the lake. In addition, thermal surveys need to be made to determine change in heat stored in the lake. If data from distant climate stations are the only data available, and they include solar radiation, the Jensen-Haise and Makkink equations resulted in monthly evaporation values that agreed reasonably well with energy budget values.

  20. Predicting water-surface fluctuation of continental lakes: A RS and GIS based approach in Central Mexico

    USGS Publications Warehouse

    Mendoza, M.E.; Bocco, G.; Bravo, M.; Lopez, Granados E.; Osterkamp, W.R.

    2006-01-01

    Changes in the water-surface area occupied by the Cuitzeo Lake, Mexico, during the 1974-2001 period are analysed in this study. The research is based on remote sensing and geographic information techniques, as well as statistical analysis. High-resolution satellite image data were used to analyse the 1974-2000 period, and very low-resolution satellite image data were used for the 1997-2001 period. The long-term analysis (1974-2000) indicated that there were temporal changes in the surface area of the Cuitzeo Lake and that these changes were related to precipitation and temperatures that occurred in the previous year. Short-term monitoring (1997-2001) showed that the Cuitzeo Lake surface is lowering. Field observations demonstrated also that yearly desiccation is recurrent, particularly, in the western section of the lake. Results suggested that this behaviour was probably due to a drought period in the basin that began in the mid 1990s. Regression models constructed from long-term data showed that fluctuations of lake level can be estimated by monthly mean precipitation and temperatures of the previous year. ?? Springer Science + Business Media, Inc. 2006.

  1. Phylogenetic analysis of a microbialite-forming microbial mat from a hypersaline lake of the Kiritimati atoll, Central Pacific.

    PubMed

    Schneider, Dominik; Arp, Gernot; Reimer, Andreas; Reitner, Joachim; Daniel, Rolf

    2013-01-01

    On the Kiritimati atoll, several lakes exhibit microbial mat-formation under different hydrochemical conditions. Some of these lakes trigger microbialite formation such as Lake 21, which is an evaporitic, hypersaline lake (salinity of approximately 170‰). Lake 21 is completely covered with a thick multilayered microbial mat. This mat is associated with the formation of decimeter-thick highly porous microbialites, which are composed of aragonite and gypsum crystals. We assessed the bacterial and archaeal community composition and its alteration along the vertical stratification by large-scale analysis of 16S rRNA gene sequences of the nine different mat layers. The surface layers are dominated by aerobic, phototrophic, and halotolerant microbes. The bacterial community of these layers harbored Cyanobacteria (Halothece cluster), which were accompanied with known phototrophic members of the Bacteroidetes and Alphaproteobacteria. In deeper anaerobic layers more diverse communities than in the upper layers were present. The deeper layers were dominated by Spirochaetes, sulfate-reducing bacteria (Deltaproteobacteria), Chloroflexi (Anaerolineae and Caldilineae), purple non-sulfur bacteria (Alphaproteobacteria), purple sulfur bacteria (Chromatiales), anaerobic Bacteroidetes (Marinilabiacae), Nitrospirae (OPB95), Planctomycetes and several candidate divisions. The archaeal community, including numerous uncultured taxonomic lineages, generally changed from Euryarchaeota (mainly Halobacteria and Thermoplasmata) to uncultured members of the Thaumarchaeota (mainly Marine Benthic Group B) with increasing depth.

  2. Evaluation of DNA damage in Eurasian marsh frogs (Pelophylax ridibundus) by comet assay for determination of possible pollution in the different lakes in central Anatolia, Turkey.

    PubMed

    Erismis, Ugur Cengiz; Ciğerci, İbrahim Hakki; Konuk, Muhsin

    2013-06-01

    In the present study, adult Eurasian marsh frogs, Pelophylax ridibundus, and water samples were collected from a reference lake and three water bodies in central Anatolia, Turkey, to evaluate the water for chemical pollutants and possible effects of pollutants on the DNA of frog erythrocytes by using a comet assay. The results for DNA damage parameters of the comet assay (total comet length, tail intensity, and olive tail moment) and their statistical analysis by ANOVA demonstrated that P. ridibundus and the comet assay together represent an useful approach for the early detection of polluted water bodies.

  3. Rates, timing, and cyclicity of Holocene eolian activity in north-central United States: Evidence from varved lake sediments

    USGS Publications Warehouse

    Dean, W.E.

    1997-01-01

    Most of the sediment components that accumulated in Elk Lake, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium, and quartz, that enters the lake mostly as eolian dust. The eolian clastic influx to Elk Lake was considerably greater during the mid-Holocene (8-4 ka) than it has been for the past 4000 yr, when periods of increased eolian activity correspond to the time of the Little Ice Age and the dust bowl. Geochemical records of eolian activity exhibit distinct cyclicities with dominant periodicities of 400 and 84 yr.

  4. Potential hydrologic effects of peat mining in the Red Lake Peatlands, north-central Minnesota: A project plan

    USGS Publications Warehouse

    Siegel, Donald I.

    1979-01-01

    Peat is being considered for fuel in Minnesota. This study will investigate the potential effects of large-scale surface mining of peat on the hydrology and water quality of Upper Red Lake and the Tamarac River. The major aspects of the study are the characterization of the surface-water and groundwater hydrology and water quality, including the trace-metal content of the peat. Data will be collected to construct two- and three-dimensional digital models to simulate the movement of ground water and its relation to surface water in the peatlands, streams, and lakes. After the model is calibrated with field data, it will be used to evaluate the effect of mining peat on the hydrology and water quality of the Upper Red Lake and Tamarac River.

  5. Great Lakes Initiative (GLI) Clearinghouse

    EPA Pesticide Factsheets

    The Great Lakes Initiative Toxicity Clearinghouse is a central location for information on criteria, toxicity data, exposure parameters and other supporting documents used in developing water quality standards in the Great Lakes watershed.

  6. Estimation of the geothermal potential of the Caldara di Manziana site in the Mts Sabatini Volcanic District (Central Italy) by integrating geochemical data and 3D-GIS modelling.

    NASA Astrophysics Data System (ADS)

    Ranaldi, Massimo; Lelli, Matteo; Tarchini, Luca; Carapezza, Maria Luisa; Patera, Antonio

    2016-04-01

    High-enthalpy geothermal fields of Central Italy are hosted in deeply fractured carbonate reservoirs occurring in thermally anomalous and seismically active zones. However, the Mts. Sabatini volcanic district, located north of Rome, has an interesting deep temperatures (T), but it is characterized by low to very low seismicity and permeability in the reservoir rocks (mostly because of hydrothermal self-sealing processes). Low PCO2 facilitates the complete sealing of the reservoir fractures, preventing hot fluids rising and, determining a low CO2 flux at the surface. Conversely, high CO2 flux generally reflects a high pressure of CO2, suggesting that an active geothermal reservoir is present at depth. In Mts. Sabatini district, the Caldara of Manziana (CM) is the only zone characterized by a very high CO2 flux (188 tons/day) from a surface of 0.15 km2) considering both the diffuse and viscous CO2 emission. This suggests the likely presence of an actively degassing geothermal reservoir at depth. Emitted gas is dominated by CO2 (>97 vol.%). Triangular irregular networks (TINs) have been used to represent the morphology of the bottom of the surficial volcanic deposits, the thickness of the impervious formation and the top of the geothermal reservoir. The TINs, integrated by T-gradient and deep well data, allowed to estimate the depth and the temperature of the top of the geothermal reservoir, respectively to ~-1000 m from the surface and to ~130°C. These estimations are fairly in agreement with those obtained by gas chemistry (818Bracciano lake is the most thermally anomalous zone of the area. Geothermometers and the GIS model indicated a temperature range between

  7. An 11 000-year-long record of fire and vegetation history at Beaver Lake, Oregon, central Willamette Valley

    Treesearch

    Megan K. Walsh; Christopher A. Pearl; Cathy Whitlock; Patrick J. Bartlein; Marc A. Worona

    2010-01-01

    High-resolution macroscopic charcoal and pollen analysis were used to reconstruct an 11 000-year-long record of fire and vegetation history from Beaver Lake, Oregon, the first complete Holocene paleoecological record from the floor of the Willamette Valley. In the early Holocene (ca 11 000-7500 calendar years before present [cal yr BP]), warmer, drier summers than at...

  8. Holocene record of precipitation seasonality from lake calcite δ18O in the central Rocky Mountains, United States

    USGS Publications Warehouse

    Anderson, Lesleigh

    2011-01-01

    A context for recent hydroclimatic extremes and variability is provided by a ~10 k.y. sediment carbonate oxygen isotope (??18O) record at 5-100 yr resolution from Bison Lake, 3255 m above sea level, in northwestern Colorado (United States). Winter precipitation is the primary water source for the alpine headwater lake in the Upper Colorado River Basin and lake water ??18O measurements reflect seasonal variations in precipitation ??18O. Holocene lake water ??18O variations are inferred from endogenic sedimentary calcite ??18O based on comparisons with historic watershed discharge records and tree-ring reconstructions. Drought periods (i.e., drier winters and/or a more rain-dominated seasonal precipitation balance) generally correspond with higher calcite ??18O values, and vice-versa. Early to middle Holocene ??18O values are higher, implying a rain-dominated seasonal precipitation balance. Lower, more variable ??18O values after ca. 3500 yr ago indicate a snow-dominated but more seasonally variable precipitation balance. The middle to late Holocene ??18O record corresponds with records of El Ni??o Southern Oscillation intensification that supports a teleconnection between Rocky Mountain climate and North Pacific sea-surface temperatures at decade to century time scales. ?? 2011 Geological Society of America.

  9. Reconstructing hydroclimatic variations using compound-specific hydrogen isotope analysis of biomarkers from a maar lake in the Central Highlands, Vietnam

    NASA Astrophysics Data System (ADS)

    Doiron, Kelsey; Stevens, Lora; Sauer, Peter

    2017-04-01

    Monsoonal variation in Southeast Asia affects a significant portion of the global population, but knowledge regarding response of the monsoon system to changing boundary conditions is limited. The paleoclimatic tool of compound-specific isotope analysis(CSIA) provides the ability to reconstruct past precipitation using a diverse set of biomarkers preserved in the sedimentary record. Limited proxies in tropical southeast Asia and difficult site access have led to a deficit in paleoclimate records. Ia M'He (14˚ 10'45" N, 107˚ 52' E) is a shallow volcanic crater (maar) lake, approximately 57 ha, located in the Central Highlands of Vietnam. Precipitation in the Central Highlands is sensitive to reorganizations of major climatic features, such as the migration of the ITCZ and the coupled Indo-Asian monsoon, ENSO and related shifts in the Pacific Walker Circulation and typhoon frequency. To examine this complex behavior, this pilot study aims to provide a 500-year record of effective moisture inferred from CSIA of hydrogen isotopes on biomarkers. Carbon/nitrogen ratios and carbon isotope ratios indicate that bulk organic matter is a combination of algae and C3 vegetation, offering the potential to use compound-specific hydrogen isotopes of aquatic and terrestrial organic matter in tandem. Preliminary analysis of the core shows dominant alkane chain lengths of C27 and C29, associated with terrestrial plant leaf waxes. The hydrogen isotope ratios of the plant wax components provide a proxy for paleo precipitation in a region where rainfall and droughts heavily influence population dynamics and create social discord. The CSIA record is expected to correlate with records from northern Vietnam, the South China Sea and Indonesia, with greater precipitation during the Little Ice Age. The degree to which evaporative modification of lake water (i.e., seasonal drying) occurs will be estimated by comparing the terrestrial CSIA values indicative of meteoric water with aquatic CSIA

  10. Increasing heavy metals in the background atmosphere of central North China since the 1980s: Evidence from a 200-year lake sediment record

    NASA Astrophysics Data System (ADS)

    Wan, Dejun; Song, Lei; Yang, Jinsong; Jin, Zhangdong; Zhan, Changlin; Mao, Xin; Liu, Dongwei; Shao, Yue

    2016-08-01

    Long-term trends of atmospheric compositions are significant for assessing the influence of human activities on the atmosphere and protecting the atmospheric environment. In this study, based on heavy metal concentrations and Pb isotope ratios in a well-dated sediment core from a remote alpine lake in central North China, anthropogenic fluxes of As, Cd, Sb, and Pb were reconstructed and heavy metal evolutions in the atmosphere were revealed in the last 200 years. The heavy metals in the atmosphere were generally natural origins before 1980 A.D. Since the 1980s they began to increase gradually, but they increased the most in the 1990s resulting from rapid developments of rough and high energy-consuming industries in North China. After entering the 21st century the industries still developed rapidly, but the atmospheric Pb ceased increase and the As and Sb even decreased in the 2000s due to (1) phasing out of leaded gasoline and (2) implementing stricter industrial emission standards in 2000 A.D. in China. However, in the 2000s the atmospheric heavy metals still kept at a relatively high level and even likely began to increase again in the 2010s. Considering the lake relatively remote and seldom affected by local human activities, the results likely reflect heavy metal evolutions in the regional background atmosphere of central North China at the annual/decadal timescale in the last 200 years.

  11. Oxygen isotope composition of diatoms as Late Holocene climate proxy at Two-Yurts Lake, Central Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Meyer, Hanno; Chapligin, Bernhard; Hoff, Ulrike; Nazarova, Larisa; Diekmann, Bernhard

    2015-11-01

    Especially in combination with other proxies, the oxygen isotope composition of diatom silica (δ18Odiatom) from lake sediments is useful for interpreting past climate conditions. This paper presents the first oxygen isotope data of fossil diatoms from Kamchatka, Russia, derived from sediment cores from Two-Yurts Lake (TYL). For reconstructing Late Holocene climate change, palaeolimnological investigations also included diatom, pollen and chironomid analysis. The most recent diatom sample (δ18Odiatom = + 23.3‰) corresponds well with the present day isotopic composition of the TYL water (mean δ18O = - 14.8‰) displaying a reasonable isotope fractionation in the system silica-water. Nonetheless, the TYL δ18Odiatom record is mainly controlled by changes in the isotopic composition of the lake water. TYL is considered as a dynamic system triggered by differential environmental changes closely linked with lake-internal hydrological factors. The diatom silica isotope record displays large variations in δ18Odiatom from + 27.3‰ to + 23.3‰ from about ~ 4.5 kyr BP until today. A continuous depletion in δ18Odiatom of 4.0‰ is observed in the past 4.5 kyr, which is in good accordance with other hemispheric environmental changes (i.e. a summer insolation-driven Mid- to Late Holocene cooling). The overall cooling trend is superimposed by regional hydrological and atmospheric-oceanic changes. These are related to the interplay between Siberian High and Aleutian Low as well as to the ice dynamics in the Sea of Okhotsk. Additionally, combined δ18Odiatom and chironomid interpretations provide new information on changes related to meltwater input to lakes. Hence, this diatom isotope study provides further insight into hydrology and climate dynamics of this remote, rarely investigated area.

  12. The 1.1-Ga Midcontinent Rift System, central North America: sedimentology of two deep boreholes, Lake Superior region

    NASA Astrophysics Data System (ADS)

    Ojakangas, Richard W.; Dickas, Albert B.

    2002-03-01

    The Midcontinent Rift System (MRS) of central North America is a 1.1-Ga, 2500-km long structural feature that has been interpreted as a triple-junction rift developed over a mantle plume. As much as 20 km of subaerial lava flows, mainly flood basalts, are overlain by as much as 10 km of sedimentary rocks that are mostly continental fluvial red beds. This rock sequence, known as the Keweenawan Supergroup, has been penetrated by a few deep boreholes in the search for petroleum. In this paper, two deep boreholes in the Upper Peninsula of Michigan are described in detail for the first time. Both the Amoco Production #1-29R test, herein referred to as the St. Amour well, and the nearby Hickey Creek well drilled by Cleveland Cliffs Mining Services, were 100% cored. The former is 7238 ft (2410 m) deep and the latter is 5345 ft (1780 m) deep. The entirety of the stratigraphic succession of the Hickey Creek core correlates very well with the upper portion of the St. Amour core, as determined by core description and point-counting of 43 thin sections selected out of 100 studied thin sections. Two Lower Paleozoic units and two Keweenawan red bed units—the Jacobsville Sandstone and the underlying Freda Sandstone—are described. The Jacobsville is largely a feldspatholithic sandstone and the Freda is largely a lithofeldspathic sandstone. Below the Freda, the remaining footage of the St. Amour core consists of a thick quartzose sandstone unit that overlies a heterogenous unit of intercalated red bed units of conglomerate, sandstone, siltstone, and shale; black shale; individual basalt flows; and a basal ignimbritic rhyolite. This lower portion of the St. Amour core presents an enigma, as it correlates very poorly with other key boreholes located to the west and southwest. While a black shale sequence is similar to the petroleum-bearing Nonesuch Formation farther west, there is no conglomerate unit to correlate with the Copper Harbor Conglomerate. Other key boreholes are

  13. Numerical simulation of the alluvium and terrace aquifer along the North Canadian River from Canton Lake to Lake Overholser, central Oklahoma

    USGS Publications Warehouse

    Christenson, S.C.

    1983-01-01

    Alluvium and terrace deposits of Quaternary age, which cover an area of about 400 square miles along the North Canadian River between Canton Lake and Lake Overholser, locally yield as much as 500 gallons per minute to wells. The deposits are as much as 100 feet thick and consist of clay, silt, sand, and gravel, with sand-sized material dominating. The underlying bedrock is Permian sandstone and shale. The amount of water stored in the aquifer during 1980 was estimated to be 4.00 x 1010 cubic feet. A digital model was used to estimate the ability of the aquifer to continue to supply water for irrigation, industry, and domestic use. A block-centered, finite-difference model with 1 mile node spacing was used to project the amount and distribution of water in the aquifer in the future. The model was calibrated using the aquifer discharge to the North Canadian River and the difference between computed and measured heads. The model was calibrated using recharge rate of 1 inch per year, a horizontal hydraulic conductivity of 4.5 x 10 -4 feet per second and a specific yield of 0.16. Model simulations using the 1979 pumping rate, a projected pumping rate (based on expected increases in water use), and double the projected increase in pumping rate were made to 1993. With the 1979 pumping rate, the volume of water in storage in 1993 is 3.88 x 10 10 cubic feet and ground-water discharge to the North Canadian River is 10.9 cubic feet per second. With the projected pumping increase, the volume of water in storage is 3.81 x 1010 cubic feet and ground-water discharge to the stream is 6.91 cubic feet per second. At double the projected increase in pumping rate, the volume of water in storage is 3.74 x 1010 cubic feet and the ground-water discharge is 2.93 cubic feet per second.

  14. Late Holocene Central Asia environmental change as evidenced in high-resolution continental archives - mountain lakes and tree-rings

    NASA Astrophysics Data System (ADS)

    Darin, A.; Kalugin, I.; Maksimova, N.; Ovchinikov, D.

    2009-04-01

    Cores of bottom sediments from Teletskoe Lake (Mountain Altai) and Telmen Lake (North Mongolia) were investigated by method of scanning X-ray fluorescent analysis with synchrotron radiation with the spatial resolution of 0.1 mm [1, 2]. It corresponds to the time resolution ~ 0.2-0.3 year (sedimentation rates are equal 0.51 mm/year for Teletskoe Lake and 0.64 mm/year for Telmen Lake [3, 4]). Geochemical proxy of terrigenous, organogenous and aerosol components of sediments well correlated with regional meteodata. Quantitative reconstruction of climatic parameters were constructed using the transfer functions such as: sediment composition=function (temperature, precipitation). Functions have been calibrated at the historic interval of the cores over the last 80-120 years. Dendro samples were collected in adjacent lakes areas. The joint processing of the results helped us to clarify the time-series of geochemical proxies, adjustments based on dendro climate signals. Annual temperature and precipitation change for the Altai region (0 - 3000 years ago) and Northern Mongolia region (0 - 2000 years ago) have been reconstructed. A Fourier analysis showed the same frequency of climate change for both regions. Have been identified as the main periods (frequency): 2000, 1000, 660, 500, 400, 330, 270, 200, 155, 125, 105, 80, 45, 30 and 10 years. Based on the discovered periodicities forecast the environment change for the period 2010-2050 was calculated. According to our estimates at this time is expected sharp fall of annual regional temperature. The study was funded by grant 07-05-92103 from the Russian Foundation for Basic Research. [1] K. Zolotarev et all. Scanning SR-XRF beamline for analysis of bottom sediments. // Nucl. Instrum. and Meth. in Physics Research, A470 (2001), 1-2 , P.376-379. [2] A. Daryin et all. Use of a scanning XRF analysis on SR beams from VEPP-3 storage ...// Nucl. Instrum. and Methods in Physics Research A 543 (2005) 255-258. [3] I. Kalugin et all

  15. Physical, chemical, and biological data for detailed study of the Sun River Irrigation Project, Freezout Lake Wildlife Management Area, and Benton Lake National Wildlife Refuge, west-central Montana, 1990-92, with selected data for 1987-89

    USGS Publications Warehouse

    Lambing, J.H.; Nimick, D.A.; Knapton, J.R.; Palawski, D.U.

    1994-01-01

    Physical chemical, and biological data were collected in the lower Sun River area of west-central Montana during 1990-92 as part of a U.S. Department of the Interior detailed study of the extent, magnitude, sources, and potential biological impacts of contaminants associated with irrigation drainage. Physical and chemical data were collected from areas within and near the Sun River Irrigation Project and from wetland areas receiving irrigation drainage. Biological data were collected from areas in and near Freezout Lake Wildlife Management Area and Benton Lake National Wildlife Refuge. Additional biological data were collected previously during 1987-89 as part of a U.S. Fish and Wildlife Service program. This report presents data for selenium and other potentially toxic constituents in solid-phase, water, and biological media. Data consist of concentrations of major and trace elements in soil and drill cores; concen- trations of major ions, nutrients, and trace elements in ground water and surface water; and trace-element concentrations in bottom sediment and biological tissue. Hydrogeologic data for domestic and test wells and daily streamflow data for selected sites also are included.

  16. Possible Evidence for Enhanced Seasonality During the Little Ice Age Indicated by Multiple Isotopes from Kepler Lake, South-Central Alaska

    NASA Astrophysics Data System (ADS)

    Gonyo, A.; Yu, Z.; Bebout, G.

    2008-12-01

    We present multiple-proxy data from two short cores (85 cm and 101 cm) from Kepler Lake, an evaporation- insensitive, groundwater-fed marl lake in South-Central Alaska to reconstruct climate and environmental changes in the recent centuries. The proxies used include calcite C and O isotopes, organic matter (OM) C and N isotopes, and loss on ignition (LOI) analysis. Two cores can be visually correlated based upon LOI results. A 600 year chronology was established based on 3 calibrated AMS 14C dates of terrestrial macrofossils and 210Pb analysis. δ18OVPDB values of inorganic calcite range from - 17.0‰ to -15.7‰, with the highest values between 1470 and 1840 AD during the Little Ice Age (LIA). The relatively high δ18O values during the cold LIA contrast with the conventional temperature interpretation of O isotopes. Therefore, the isotopic shifts around the LIA were likely caused by a shift in atmospheric circulation. A weakening of the wintertime Aleutian Low pressure system residing over the Gulf of Alaska would result in enriched 18O in precipitation as well as a colder winter climate in SC Alaska. During the LIA period CaCO3 contents were elevated by ~15% to >80%. Calcite precipitation in freshwater lakes is primarily a function of summer temperature; we propose that the LIA in SC Alaska represents a period of colder winters and warmer summers. This interpretation is also supported by C isotopes, reflecting aquatic productivity. Both δ13C OM and δ13Ccalcite (relative to VPDB) exhibit relatively high values at 1600 to 1840 AD, after which δ13COM remains constant throughout the rest of the record and δ13Ccalcite declines after the LIA. The delayed increase in δ13C of OM and calcites at 1600 AD may reflect the differential responses of calcite precipitation and aquatic productivity. The negative shift of ~1‰ in δ18O in the 1840s has also been documented in ice cores from Mt. Logan and in marl lake sediments from the southern Yukon, suggesting a broad

  17. InSAR detection of aquifer recovery: Case studies of Koehn Lake (central California) and Lone Tree Gold Mine (Basin and Range)

    NASA Astrophysics Data System (ADS)

    Wdowinski, S.; Greene, F.; Amelung, F.

    2013-12-01

    Anthropogenic intervention in groundwater flow and aquifer storage often results in vertical movements of Earth's surface, which are well detected by InSAR observations. Most anthropogenic intervention occurs due to groundwater extraction for both agriculture and human consumption and results in land subsidence. However in some cases, ending anthropogenic intervention can lead to aquifer recovery and, consequently, surface uplift. In this study we present two such cases of aquifer recovery. The first case is the aquifer beneath Koehn Lake in Central California, which was overused to meet agricultural demands until the 1990's. The second case is the Lone Tree Gold Mine in Nevada that during active mining in the 1991-2006 groundwater pumping disrupted the aquifer and cause subsidence. But after mining ceased, groundwater flow was recovered and resulted in uplift. In both cases we studied the surface uplift using InSAR time series observations. We conduct an ERS and Envisat InSAR survey over Koehn Lake in California and Lone Tree Gold Mine in Nevada between 1992 and 2010. We followed the SBAS algorithm to generate a time-series of ground displacements and average velocities of pixels, which remain coherent through time in the SAR dataset. A total of 100 and 80 combined ERS and Envisat SAR dates are inverted for Koehn Lake and Lone Tree Gold Mine respectively. Results for the Koehn Lake area indicate a rapid uplift of about 3.5 mm/yr between 1992-2000 and a slower uplift rate of 1.6 mm/yr between 2000-2004, suggesting a decrease in the recovery process. The observed uplift correlates well with groundwater level increase in the Koehn Lake area. Results for the Lone Tree Gold Mine show a constant subsidence (~ 1 cm/yr) due to groundwater extraction between 1992-2006, but uplift of ~1 cm/yr since the beginning of 2007. In both case studies, InSAR observations reveal that the aquifer recovery is accompanied by surface uplift. We plan to use the InSAR observations and the

  18. Glacialmorphological reconstruction of glacier advances and glacial lake outburst floods at the Cachapoal glacier in the Dry Central Andes of Chile (34°S)

    NASA Astrophysics Data System (ADS)

    Iturrizaga, Lasafam; Charrier, Reynaldo

    2013-04-01

    Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina

  19. Holocene vegetation variation in the Daihai Lake region of north-central China: a direct indication of the Asian monsoon climatic history

    NASA Astrophysics Data System (ADS)

    Xiao, Jule; Xu, Qinghai; Nakamura, Toshio; Yang, Xiaolan; Liang, Wendong; Inouchi, Yoshio

    2004-07-01

    DH99a sediment core recovered at the center of Daihai Lake in north-central China was analyzed at 4-cm intervals for pollen assemblage and concentration. The pollen record spanning the last ca 10,000 yr revealed a detailed history of vegetation and climate changes over the Daihai Lake region during the Holocene. From ca 10,250 to 7900 cal yr BP, arid herbs and shrubs dominated the lake basin in company with patches of mixed pine and broadleaved forests, indicating a mild and dry climatic condition. Over this period, the woody plants displayed an increasing trend, which may suggest a gradual increase in warmth and humidity. The period between ca 7900 and 4450 cal yr BP exhibits large-scale covers of mixed coniferous and broadleaved forests, marking a warm and humid climate. Changes in the composition of the forests indicate that both temperature and precipitation displayed obvious fluctuations during this period, i.e., cool and humid ca 7900- 7250 cal yr BP, warm and slightly humid ca 7250- 6050 cal yr BP, warm and humid between ca 6050 and 5100 cal yr BP, mild and slightly humid ca 5100- 4800 cal yr BP, and mild and humid ca 4800- 4450 cal yr BP. The period can be viewed as the Holocene optimum (characterized by a warm and moist climate) of north-central China, with the maximum (dominated both by warmest temperatures and by richest precipitations) occurring from ca 6050 to 5100 cal yr BP. During the period of ca 4450- 2900 cal yr BP, the woody plants declined, and the climate generally became cooler and drier than the preceding period. This period is characterized by a cold, dry episode from ca 4450 to 3950 cal yr BP, a warm, slightly humid interval between ca 3950 and 3500 cal yr BP and a mild, slightly dry episode from ca 3500 to 2900 cal yr BP, and appears to be a transition from warm and humid to cold and dry climatic conditions. Since ca 2900 cal yr ago, the forests disappeared and the vegetation density decreased, reflecting a cool and dry climate. However, a

  20. A New, Continuous 5400 Yr-long Paleotsunami Record from Lake Huelde, Chiloe Island, South Central Chile.

    NASA Astrophysics Data System (ADS)

    Kempf, P.; Moernaut, J.; Vandoorne, W.; Van Daele, M. E.; Pino, M.; Urrutia, R.; De Batist, M. A. O.

    2014-12-01

    After the last decade of extreme tsunami events with catastrophic damage to infrastructure and a horrendous amount of casualties, it is clear that more and better paleotsunami records are needed to improve our understanding of the recurrence intervals and intensities of large-scale tsunamis. Coastal lakes (e.g. Bradley Lake, Cascadia; Kelsey et al., 2005) have the potential to contain long and continuous sedimentary records, which is an important asset in view of the centennial- to millennial-scale recurrence times of great tsunami-triggering earthquakes. Lake Huelde on Chiloé Island (42.5°S), Chile, is a coastal lake located in the middle of the Valdivia segment, which is known for having produced the strongest ever instrumentally recorded earthquake in 1960 AD (MW: 9.5), and other large earthquakes prior to that: i.e. 1837 AD, 1737 AD (no report of a tsunami) and 1575 AD (Lomnitz, 1970, 2004, Cisternas et al., 2005). We present a new 5400 yr-long paleotsunami record with a Bayesian age-depth model based on 23 radiocarbon dates that exceeds all previous paleotsunami records from the Valdivia segment, both in terms of length and of continuity. 18 events are described and a semi-quantitative measure of the event intensity at the study area is given, revealing at least two predecessors of the 1960 AD event in the mid to late Holocene that are equal in intensity. The resulting implications from the age-depth model and from the semi-quantitative intensity reconstruction are discussed in this contribution.

  1. Accumulation of clinically relevant antibiotic-resistance genes, bacterial load, and metals in freshwater lake sediments in Central Europe.

    PubMed

    Devarajan, Naresh; Laffite, Amandine; Graham, Neil D; Meijer, Maria; Prabakar, Kandasamy; Mubedi, Josué I; Elongo, Vicky; Mpiana, Pius T; Ibelings, Bastiaan Willem; Wildi, Walter; Poté, John

    2015-06-02

    Wastewater treatment plants (WWTP) receive the effluents from various sources (communities, industrial, and hospital effluents) and are recognized as reservoir for antibiotic-resistance genes (ARGs) that are associated with clinical pathogens. The aquatic environment is considered a hot-spot for horizontal gene transfer, and lake sediments offer the opportunity for reconstructing the pollution history and evaluating the impacts. In this context, variation with depth and time of the total bacterial load, the abundance of faecal indicator bacteria (FIB; E. coli and Enterococcus spp. (ENT)), Pseudomonas spp., and ARGs (blaTEM, blaSHV, blaCTX-M, blaNDM, and aadA) were quantified in sediment profiles of different parts of Lake Geneva using quantitative PCR. The abundance of bacterial marker genes was identified in sediments contaminated by WWTP following eutrophication of the lake. Additionally, ARGs, including the extended-spectrum ß-lactam- and aminoglycoside-resistance genes, were identified in the surface sediments. The ARG and FIB abundance strongly correlated (r ≥ 0.403, p < 0.05, n = 34) with organic matter and metal concentrations in the sediments, indicating a common and contemporary source of contamination. The contamination of sediments by untreated or partially treated effluent water can affect the quality of ecosystem. Therefore, the reduction of contaminants from the source is recommended for further improvement of water quality.

  2. Diatom, Pollen, and Chemical Evidence of Postglacial Climatic Change at Big Lake, South-Central British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Bennett, Joseph R.; Cumming, Brian F.; Leavitt, Peter R.; Chiu, Marian; Smol, John P.; Szeicz, Julian

    2001-05-01

    Postglacial climatic conditions were inferred from cores taken from Big Lake in southern British Columbia. Low concentrations of nonarboreal pollen and pigments near the base of the core suggest that initial conditions were cool. Increases in both aquatic and terrestrial production suggest warmer and moister conditions until ∼8500 cal yr B.P. Hyposaline diatom assemblages, increases in nonarboreal pollen, and increased concentrations of pigments suggest the onset of arid conditions from ∼8500 to ∼7500 cal yr B.P. Slightly less arid conditions are inferred from ∼7500 until ∼6660 cal yr B.P. based on the diatoms, small increases and greater variability in biogenic silica and pigments, and higher percentages of arboreal pollen. At ∼6600 cal yr B.P., changes in diatoms, pigments, biogenic silica, and organic matter suggest that Big Lake became fresh, deep, and eutrophic until ∼3600 cal yr B.P., when water levels and nutrients decreased slightly. Our paleoclimatic inferences are similar to pollen-based studies until ∼6600 cal yr B.P. However, unlike these studies, our multiple lines of evidence from Big Lake imply large changes in effective moisture since 6000 cal yr B.P.

  3. [Effects of Three Gorges Reservoir impoundment on the wetland ecosystem service value of Dongting Lake, South-central China].

    PubMed

    Li, Jing-Bao; Dai, Yong; Yin, Ri-Xin; Yang, Yan; Li, Yu-dan; Wang, Ke-ying

    2013-03-01

    Based on the field investigation and measurement, and by using the monetary method, this paper estimated the wetland ecosystem service value of Dongting Lake before and after the impoundment of Three Gorges Reservoir (in 1996 and 2010, respectively). After the impoundment, the total ecosystem service value increased from 156.69x10(8) yuan in 1996 to 177.11x10(8) yuan in 2010. The main services value in 1996 was in the order of flood storage and regulation > water storage and supply > air regulation > scientific research and education, while that in 2010 was leisure tourism > shipping transportation > air regulation > water storage and supply. In the total service value of the wetland ecosystem, the direct value associated with water decreased from 110. 85x10(8) in 1996 to 27.47x10(8) in 2010, with a decrement of 75.2%. Though the proportion of the direct value in the production and supply of material products had somewhat increase, the indirect value in ecological environment regulation and maintenance and in culture and society still maintained at about 80% of the total value. In addition to climate factors, the impoundment of Three Gorges Reservoir and the reduction of water and sediment from Yangtze River to the Lake were the crucial reasons leading to the changes of the wetland ecosystem service value of Dongting Lake.

  4. Southeastern extension of the Lake Basin fault zone in south- central Montana: implications for coal and hydrocarbon exploration ( USA).

    USGS Publications Warehouse

    Robinson, L.N.; Barnum, B.E.

    1986-01-01

    The Lake Basin fault zone consists mainly of en echelon NE-striking normal faults that have been interpreted to be surface expressions of left-lateral movement along a basement wrench fault. Information gathered from recent field mapping of coal beds and from shallow, closely-spaced drill holes resulted in detailed coal bed correlations, which revealed another linear zone of en echelon faulting directly on the extended trend of the Lake Basin fault zone. This faulted area, referred to as the Sarpy Creek area, is located 48 km E of Hardin, Montana. It is about 16 km long, 13 km wide, and contains 21 en echelon normal faults that have an average strike of N 63oE. We therefore extend the Lake Basin fault zone 32 km farther SE than previously mapped to include the Sarpy Creek area. The Ash Creek oil field, Wyoming, 97 km due S of the Sarpy Creek area, produces from faulted anticlinal structues that have been interpreted to be genetically related to the primary wrench-fault system known as the Nye-Bowler fault zone. The structural similarities between the Sarpy Creek area and the Ash Creek area indicate that the Sarpy Creek area is a possible site for hydrocarbon accumulation.-from Authors

  5. Warmed winters and weakened precipitation on Mt. Everest (central southern Himalaya) impacts glaciers, lakes, permafrost, and river discharges

    NASA Astrophysics Data System (ADS)

    Salerno, F.; Guyennon, N.; Thakuri, S.; Freppaz, M.; Balestrini, R.; Vuillermoz, E.; Tartari, G.

    2014-12-01

    This contribution aims linking temperature and precipitation patterns detected at high elevation of south slopes of Mt. Everest with a) glacier and lake surfaces, b) altitude limit of permafrost, c) frequency of daily river discharges. The study is carried out though: a) the daily temperature and precipitation reconstruction of the last twenty years (1994-2013) at 5050 m a.s.l. and 25 AWSs located at lower elevation and on Tibetan Plateau b) glacier surfaces (about 400 km2) and lake areas (more than 100 lakes) since 60s using all available satellite imagery c) permafrost distribution carried out with soil temperature measurements (2010-2012) compared with previous studies (70s) d) the results of a stochastic frequency model (wavelet analysis) for detecting river discharge changes in frequency of the Dud Koshi River basin (3000 km2) since 60s. We observed an increasing temperature trend occurred mainly in winter months, but during the summer ones we observed a slight decreasing of maximum temperature. We confirm for these high elevations the generalized weakening of the monsoon already observed in literature accounting here over 50% of reduction in the last 20 years! In the previous period (70s to 90s) gridded an reanalysis data revealed for our reference site a slighter increase of mean temperature and weak increase of precipitation. Main climate change driven implications: - The accelerated shrinkage of glaciers observed in the last twenty years, usually inferred to the temperature increase during the summer months, is ascribed here mainly to the regional monsoon weakening. - Supraglacial lakes confirm the acceleration of the negative mass balance of glaciers due to reduced ice velocities caused by decreased precipitation. - Unconnected lakes confirms precisely the observed precipitation trend. - The altitudinal limit of the permanent permafrost seems to be unchanged since the beginning '90s (probably due to stationary summer temperature). - Rivers discharges

  6. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 96LCA04 in Lakes Mabel and Starr, Central Florida, August 1996

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Swancar, Amy; Tihansky, Ann B.; Flocks, James G.; Wiese, Dana S.

    2008-01-01

    In August of 1996, the U.S. Geological Survey conducted geophysical surveys of Lakes Mabel and Starr, central Florida, as part of the Central Highlands Lakes project, which is part of a larger USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, observer's logbook; and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. For detailed information about the hydrologic setting of Lake Starr and the interpretation of some of these seismic reflection data, see Swancar and others (2000) at http://fl.water.usgs.gov/publications/Abstracts/wri00_4030_swancar.html. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 96LCA04 tells us the data were collected in 1996 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the fourth field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when

  7. Concentrations and loads of nutrients in the tributaries of the Lake Okeechobee watershed, south-central Florida, water years 2004-2008

    USGS Publications Warehouse

    Byrne, Michael J.; Wood, Molly S.

    2011-01-01

    Lake Okeechobee in south-central Florida is the second largest freshwater lake in the contiguous United States. Excessive phosphorus loading, harmful high and low water levels, and rapid expansion of non-native vegetation have threatened the health of the lake in recent decades. A study was conducted to monitor discharge and nutrient concentrations from selected tributaries into Lake Okeechobee and to evaluate nutrient loads. The data analysis was performed at 16 monitoring stations from December 2003 to September 2008. Annual and seasonal discharge measured at monitoring stations is affected by rainfall. Hurricanes affected three wet years (2004, 2005, and the latter part of 2008) and resulted in substantially greater discharge than the drought years of 2006, 2007, and the early part of 2008. Rainfall supplies about 50 percent of the water to Lake Okeechobee, discharge from the Kissimmee River supplies about 25 percent, and discharge from tributaries and groundwater seepage along the lake perimeter collectively provide the remaining 25 percent. Annually, tributary discharge from basins located on the west side of the Kissimmee River is about 5 to 6 times greater than that from basins located on the east side. For the purposes of this study, the basins on the east side of the Kissimmee River are called "priority basins" because of elevated phosphorus concentrations, while those on the west side are called "nonpriority" basins. Total annual discharge in the non-priority basins ranged from 245,000 acre-feet (acre-ft) in 2007 to 1,322,000 acre-ft in 2005, while annual discharge from the priority basins ranged from 41,000 acre-ft in 2007 to 219,000 acre-ft in 2005. Mean total phosphorus concentrations ranged from 0.10 to 0.54 milligrams per liter (mg/L) at the 16 tributaries during 2004–2008. Mean concentrations were significantly higher at priority basin sites than at non-priority basin sites, particularly at Arbuckle Creek and C 41A Canal. Concentrations of organic

  8. Nitrate and pesticides in surficial aquifers and trophic state and phosphorus sources for selected lakes, eastern Otter Tail County, west-central Minnesota, 1993-96

    USGS Publications Warehouse

    Ruhl, J.F.

    1997-01-01

    Phosphorus at depth in Little Pine and Big Pine Lakes was mostly orthophosphate. During the fall turnover of the lakes, this orthophosphate may have circulated to near the lake surface and became an available nutrient for phytoplankton during the following growing season. The internal phosphorus load to Little Pine Lake may have been important because about three-fourths of the lake probably became stratified and anoxic in the hypolimnion. The internal phosphorus load to Big Pine Lake may not have been important because only a small portion of the lake became stratified and anoxic at depth.

  9. Diagenesis of Paleozoic playa-lake and ephemeral-stream deposits from the Pimenta Bueno Formation, Siluro-Devonian (?) of the Parecis Basin, central Brazil

    NASA Astrophysics Data System (ADS)

    Goldberg, K.; Morad, S.; Al-Aasm, I. S.; De Ros, L. F.

    2011-07-01

    The Parecis Basin is a large intracratonic rift located in central Brazil and filled with Paleozoic carbonate, evaporite and siliciclastic sediments. The occurrence of gas seeps has recently attracted significant exploration interest by the Brazilian petroleum agency and by Petrobras. The continuously cored PB-01-RO well provided the first opportunity to study the depositional environments, diagenetic evolution and hydrocarbon potential of the largely unknown sedimentary successions of the Parecis Basin. The cored lithologies, belonging to the Siluro-Devonian (?) Pimenta Bueno Formation, are interpreted as deposited in playa-lake and ephemeral-stream environments. The deposits display a strong facies control on the diagenetic mineral assemblages and evolution. Diagenetic minerals in the ephemeral-stream deposits include eogenetic hematite and smectitic clay coats and quartz cement, and the mesogenetic process includes precipitation of sulfates (anhydrite and barite) and carbonates (calcite, dolomite and kutnahorite-ankerite-huntite), followed by partial dissolution of these carbonates and sulfates, and of feldspar grains. Telogenetic processes include the precipitation of hematite and kaolinite within secondary pores, and the replacement of anhydrite by gypsum. A second burial phase and mesodiagenesis is indicated by the precipitation of discrete K-feldspar crystals within moldic pores after dissolved feldspars, and by the illitization of etched, telogenetic kaolinite. The playa-lake deposits show early diagenetic dolomitization of lime mud, precipitation of anhydrite nodules and extensive silicification. The anhydrite nodules were replaced by gypsum and chalcedony during telodiagenesis. Potential source rocks are locally represented by organic shales. The fluvial sandstones show fair reservoir quality and limited compaction, as indicated by their intergranular volume, suggesting that the succession has undergone moderate burial. Potential seals for hydrocarbon

  10. Lake-sediment record of PAH, mercury, and fly-ash particle deposition near coal-fired power plants in Central Alberta, Canada.

    PubMed

    Barst, Benjamin D; Ahad, Jason M E; Rose, Neil L; Jautzy, Josué J; Drevnick, Paul E; Gammon, Paul R; Sanei, Hamed; Savard, Martine M

    2017-08-25

    We report a historical record of atmospheric deposition in dated sediment cores from Hasse Lake, ideally located near both currently and previously operational coal-fired power plants in Central Alberta, Canada. Accumulation rates of spheroidal carbonaceous particles (SCPs), an unambiguous marker of high-temperature fossil-fuel combustion, in the early part of the sediment record (pre-1955) compared well with historical emissions from one of North America's earliest coal-fired power plants (Rossdale) located ∼43 km to the east in the city of Edmonton. Accumulation rates in the latter part of the record (post-1955) suggested inputs from the Wabamun region's plants situated ∼17-25 km to the west. Increasing accumulation rates of SCPs, polycyclic aromatic hydrocarbons (PAHs) and Hg coincided with the previously documented period of peak pollution in the Wabamun region during the late 1960s to early 1970s, although Hg deposition trends were also similar to those found in western North American lakes not directly affected by point sources. A noticeable reduction in contaminant inputs during the 1970s is attributed in part to technological improvements and stricter emission controls. The over one hundred-year historical record of coal-fired power plant emissions documented in Hasse Lake sediments has provided insight into the impact that both environmental regulations and changes in electricity output have had over time. This information is crucial to assessing the current and future role of coal in the world's energy supply. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  11. Investigating molecular changes in organic matter composition in two Holocene lake-sediment records from central Sweden using pyrolysis-GC/MS

    NASA Astrophysics Data System (ADS)

    Ninnes, Sofia; Tolu, Julie; Meyer-Jacob, Carsten; Mighall, Tim M.; Bindler, Richard

    2017-06-01

    Organic matter (OM) is a key component of lake sediments, affecting carbon, nutrient, and trace metal cycling at local and global scales. Yet little is known about long-term (millennial) changes in OM composition due to the inherent chemical complexity arising from multiple OM sources and from secondary transformations. In this study we explore how the molecular composition of OM changes throughout the Holocene in two adjacent boreal lakes in central Sweden and compare molecular-level information with conventional OM variables, including total carbon, total nitrogen, C:N ratios, δ13C, and δ15N. To characterize the molecular OM composition, we employed a new method based on pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), which yields semiquantitative data on >100 organic compounds of different origin and degradation status. We identify large changes in OM composition after deglaciation (circa 8500 ± 500 B.C.), associated with early landscape development, and during the most recent 40-50 years, driven by degradation processes. With molecular-level information we can also distinguish between natural landscape development and human catchment disturbance during the last 1700 years. Our study demonstrates that characterization of the molecular OM composition by the high-throughput Py-GC/MS method is an efficient complement to conventional OM variables for identification and understanding of past OM dynamics in lake-sediment records. Holocene changes observed for pyrolytic compounds and compound classes known for having different reactivity indicate the need for further paleo-reconstruction of the molecular OM composition to better understand both past and future OM dynamics and associated environmental changes.

  12. Late Holocene evolution of playa lakes in the central Ebro depression based on geophysical surveys and morpho-stratigraphic analysis of lacustrine terraces

    NASA Astrophysics Data System (ADS)

    Gutiérrez, F.; Valero-Garcés, B.; Desir, G.; González-Sampériz, P.; Gutiérrez, M.; Linares, R.; Zarroca, M.; Moreno, A.; Guerrero, J.; Roqué, C.; Arnold, L. J.; Demuro, M.

    2013-08-01

    The origin and morpho-stratigraphic evolution of the largest playa-lake system (La Playa-El Pueyo) in the Bujaraloz-Sástago endorheic area, located in the semiarid central sector of the Ebro Depression, are analysed. The enclosed depressions are developed on gypsiferous Tertiary bedrock and show a prevalent WNW-ESE orientation parallel to the direction of the prevalent strong local wind (Cierzo). Yardangs have been carved in bedrock and unconsolidated terrace deposits in the leeward sector of the largest lake basins. A sequence of three lacustrine terrace levels has been identified by detailed geomorphological mapping. The treads of the upper, middle and lower terrace levels are situated at + 9 m, + 6 m and + 0.5 m above the playa-lake floors, respectively. Seismic refraction and electrical resistivity profiles acquired in La Playa reveal a thin basin fill (~ 2 m) with a planar base. These data allow ruling out the genetic hypothesis for the depressions involving the collapse of large bedrock cavities and support a mixed genesis of combined widespread dissolution and subsidence by groundwater discharge and eolian deflation during dry periods. The 5 m thick deposit of the middle terrace was investigated in hand-dug and backhoe trenches. Six AMS radiocarbon ages from this terrace indicate an aggradation phase between 3.9 ka and ca. 2 ka. These numerical ages yield a maximum average aggradation rate of 2.6 mm/yr and a minimum excavation rate by wind deflation of 3 mm/yr subsequent to the accumulation of the middle terrace. The latter figure compares well with those calculated in several arid regions of the world using yardangs carved in palaeolake deposits. The aggradation phase between 4 and 2 ka is coherent with other Iberian and Mediterranean records showing relatively more humid conditions after 4 ka, including the Iron Ages and the Iberian-Roman Period.

  13. Chloride cycling in two forested lake watersheds in the west-central Adirondack Mountains, New York, U.S.A.

    USGS Publications Warehouse

    Peters, N.E.

    1991-01-01

    The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling C1- cycling. Results indicate that C1- cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived C1- through the ecosystem. The annual throughfall Cl- flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha-1), whereas the Na+ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl- sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na+ concentrations and averaged 31 ??eq L-1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 ??eq L-1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl- concentrations with increasing flow. Major sources of Cl- in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till( > 3 m), hornblende weathering results in a net Cl- flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl- in the biomass of the two watersheds was comparable to the precipitation Cl- flux.The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling Cl- cycling. Results indicate that Cl- cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived Cl- through the excosystem. The annual throughfall Cl- flux for individual species in the northern hardwood forest was 2 to 5 times that of

  14. Temporal Changes in Gametogenesis of the Invasive Chinese Pond Mussel Sinanodonta woodiana (Lea, 1834) (Bivalvia: Unionidae) from the Konin Lakes System (Central Poland).

    PubMed

    Hliwa, Piotr; Zdanowski, Bogusław; Dietrich, Grzegorz J; Andronowska, Aneta; Król, Jarosław; Ciereszko, Andrzej

    2015-01-01

    Gametogenesis and the temporal changes occurring in the ovaries and testes throughout the reproductive cycle in the invasive alien bivalve, Chinese pond mussel Sinanodonta woodiana (Lea), from the heated Konin lakes system (central Poland) were studied using histological techniques. S. woodiana was confirmed to be a gonochoristic species with overall sex ratio of 1:1. The examined morphological parameters of Chinese pond mussel spermatozoa, i.e. 42 μm mean total length; 4.3 μm mean head length and the maximum size of previtellogenic (34-43 μm) and vitellogenic oocytes (75-83 μm) are consistent with values established for closely related members of the Unionidae family. Our results suggest that S. woodiana in the Konin lakes system are able to spawn throughout March to October, with a season of higher reproductive activity in females extending from March to April. This type of reproductive biology may contribute to the Chinese pond mussel's success in thriving in freshwater ecosystems.

  15. Agricultural nitrate monitoring in a lake basin in Central Italy: a further step ahead towards an integrated nutrient management aimed at controlling water pollution.

    PubMed

    Garnier, Monica; Recanatesi, Fabio; Ripa, Maria Nicoletta; Leone, Antonio

    2010-11-01

    Water pollution from point sources has been considerably reduced over the last few decades. Nevertheless, some water quality problems remain, which can be attributed to non-point pollution sources, and in particular to agriculture. In this paper the results of a study intended to assess the consequences, in terms of NO3 water pollution, of growing a crop, whose impact in terms of P pollution is already well known, are presented. The potential consequences, in terms of water pollution from nitrates of a BMP expressly applied to reduce P pollution are also discussed. The study site is the Lake Vico basin, Central Italy, which has suffered a shift in trophic state since the mid 1990s, caused by P compounds used for intensive cultivation of hazelnut trees. The results of the monitoring campaign described in this paper allow to assert that hazelnut tree cropping has probably caused a considerable increase in nitrate concentration in the groundwater, although not in the lake water, because of the specific hydrogeological characteristics of the basin. The main conclusion is that monitoring is essential to single out environmental characteristics peculiar of a specific area, which even the most sophisticated model would not have been able to highlight. This is why monitoring and model simulations should be integrated.

  16. An 11 000-year-long record of fire and vegetation history at Beaver Lake, Oregon, central Willamette Valley

    NASA Astrophysics Data System (ADS)

    Walsh, Megan K.; Pearl, Christopher A.; Whitlock, Cathy; Bartlein, Patrick J.; Worona, Marc A.

    2010-05-01

    High-resolution macroscopic charcoal and pollen analysis were used to reconstruct an 11 000-year-long record of fire and vegetation history from Beaver Lake, Oregon, the first complete Holocene paleoecological record from the floor of the Willamette Valley. In the early Holocene (ca 11 000-7500 calendar years before present [cal yr BP]), warmer, drier summers than at present led to the establishment of xeric woodland of Quercus, Corylus, and Pseudotsuga near the site. Disturbances (i.e., floods, fires) were common at this time and as a result Alnus rubra grew nearby. High fire frequency occurred in the early Holocene from ca 11 200-9300 cal yr BP. Riparian forest and wet prairie developed in the middle Holocene (ca 7500 cal yr BP), likely the result of a decrease in the frequency of flooding and a shift to effectively cooler, wetter conditions than before. The vegetation at Beaver Lake remained generally unchanged into the late Holocene (from 4000 cal yr BP to present), with the exception of land clearance associated with Euro-American settlement of the valley (ca 160 cal yr BP). Middle-to-late Holocene increases in fire frequency, coupled with abrupt shifts in fire-episode magnitude and charcoal composition, likely indicate the influence anthropogenic burning near the site. The paleoecological record from Beaver Lake, and in particular the general increase in fire frequency over the last 8500 years, differs significantly from other low-elevation sites in the Pacific Northwest, which suggests that local controls (e.g., shifts in vegetation structure, intensification of human land-use), rather than regional climatic controls, more strongly influenced its environmental history.

  17. An 11 000-year-long record of fire and vegetation history at Beaver Lake, Oregon, central Willamette Valley

    USGS Publications Warehouse

    Walsh, Megan K.; Pearl, Christopher A.; Whitlock, Cathy; Bartlein, Patrick J.; Worona, Marc A.

    2010-01-01

    High-resolution macroscopic charcoal and pollen analysis were used to reconstruct an 11??000-year-long record of fire and vegetation history from Beaver Lake, Oregon, the first complete Holocene paleoecological record from the floor of the Willamette Valley. In the early Holocene (ca 11??000-7500 calendar years before present [cal??yr??BP]), warmer, drier summers than at present led to the establishment of xeric woodland of Quercus, Corylus, and Pseudotsuga near the site. Disturbances (i.e., floods, fires) were common at this time and as a result Alnus rubra grew nearby. High fire frequency occurred in the early Holocene from ca 11??200-9300??cal??yr??BP. Riparian forest and wet prairie developed in the middle Holocene (ca 7500??cal??yr??BP), likely the result of a decrease in the frequency of flooding and a shift to effectively cooler, wetter conditions than before. The vegetation at Beaver Lake remained generally unchanged into the late Holocene (from 4000??cal??yr??BP to present), with the exception of land clearance associated with Euro-American settlement of the valley (ca 160??cal??yr BP). Middle-to-late Holocene increases in fire frequency, coupled with abrupt shifts in fire-episode magnitude and charcoal composition, likely indicate the influence anthropogenic burning near the site. The paleoecological record from Beaver Lake, and in particular the general increase in fire frequency over the last 8500??years, differs significantly from other low-elevation sites in the Pacific Northwest, which suggests that local controls (e.g., shifts in vegetation structure, intensification of human land-use), rather than regional climatic controls, more strongly influenced its environmental history. ?? 2010 Elsevier Ltd.

  18. Evidence for sub-lacustrine volcanic activity in Lake Bolsena (central Italy) revealed by high resolution seismic data sets

    NASA Astrophysics Data System (ADS)

    Lindhorst, Katja; Krastel, Sebastian; Wagner, Bernd; Schuerer, Anke

    2017-06-01

    The Bolsena caldera that formed between 0.6 and 0.2 Ma has a well preserved structural rim, which makes it an ideal site to study the tectonic and volcanic evolution of calderas. However, the main area is covered by a 150 m deep lake which makes it rather difficult to investigate the subsurface structure directly. To overcome this problem new high resolution hydro-acoustic surveys using a multichannel reflection seismic system and a sediment echo-sounder system were conducted in September 2012. As space was limited we used a rowing boat towed by a rubber boat to handle a 36 m long and 24 channel streamer to receive seismic reflections produced using a Mini GI-Gun (0.25 l). The subsurface structure of Lake Bolsena was imaged up to a sediment depth of 190 m, which is estimated to have filled over a period of 333 kyrs. However, massive pyroclastic flow deposits found in the deeper parts of the basin indicate an initial infill of volcanic deposits from two adjacent younger calderas, the Latera (W) and Montefiascone (SE) calderas. Our data suggest that the caldera has a long history of active volcanism, because the lacustrine sediments show post-sedimentary influences of geothermal fluids. We mapped several mound structures at various stratigraphic depths. Two volcanic structures outcrop at the modern lake surface implying recent activity. One of these structures is hardly covered by sediments and has a crater-like feature in its summit. The other structure shows a pockmark-like depression on top. Another observable feature is a partially sediment filled crater located in the western part of the lake which further implies the existence of a magma chamber located beneath the Bolsena caldera. Since the late Pleistocene and Holocene, the sedimentation was mainly hemipelagic evidenced by a sediment drape of up to 10 m thick sediment drape on the uppermost sediments. Beneath the drape we found evidence for a distal tephra layer likely related to an explosive eruption from

  19. Parasite communities of European perch, Perca fluviatilis L. (Actinopterygii: Perciformes: Percidae) from Lake Łebsko (Central Coast, Poland).

    PubMed

    Morozińska-Gogol, Jolanta

    2013-01-01

    Communities of parasites of European perch from lake Łebsko were studied and compared with similar communities from the Polish coastal zone. Parasites comprised 18 autogenic and 5 allogenic species. Most individual parasites belonged to allogenic species and were in larval stages. The majority of specimens were eye parasites with Tylodelphys clavata as the eudominant species. The dominant species, Acanthocephalus lucii, belongs to the intestine parasite community. Three marine species were found: Bothriocephalus scorpii, Hysterothylacium aduncum and Echinorchynhus gadi. The results indicate that the parasite fauna consists mostly of freshwater species, common in various types of European waters, while marine species were rarely observed.

  20. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 08LCA04 in Lakes Cherry, Helen, Hiawassee, Louisa, and Prevatt, Central Florida, September 2008

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Davis, Jeffrey B.; Flocks, James G.; Wiese, Dana S.

    2009-01-01

    From September 2 through 4, 2008, the U.S. Geological Survey and St. Johns River Water Management District (SJRWMD) conducted geophysical surveys in Lakes Cherry, Helen, Hiawassee, Louisa, and Prevatt, central Florida. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, GIS information, FACS logs, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

  1. Comparative Results of Using Different Methods for Discovery of Microorganisms in very Ancient Layers of the Central Antarctic Glacier above the Lake Vostok

    NASA Technical Reports Server (NTRS)

    Abyzov, S. S.; Hoover, R. B.; Imura, S.; Mitskevich, I. N.; Naganuma, T.; Poglazova, M. N.; Ivanov, M. V.

    2002-01-01

    The ice sheet of the Central Antarctic is considered by the scientific community worldwide, as a model to elaborate on different methods to search for life outside Earth. This became especially significant in connection with the discovery of the underglacial lake in the vicinity of the Russian Antarctic Station Vostok. Lake Vostok is considered by many scientists as an analog of the ice covered seas of Jupiter's satellite Europa. According to the opinion of many researchers there is the possibility that relict forms of microorganisms, well preserved since the Ice Age, may be present in this lake. Investigations throughout the thickness of the ice sheet above Lake Vostok show the presence of microorganisms belonging to different well-known taxonomic groups, even in the very ancient horizons near close to floor of the glacier. Different methods were used to search for microorganisms that are rarely found in the deep ancient layers of an ice sheet. The method of aseptic sampling from the ice cores and the results of controlled sterile conditions in all stages when conducting these investigations, are described in detail in previous reports. Primary investigations tried the usual methods of sowing samples onto different nutrient media, and the result was that only a few microorganisms grew on the media used. The possibility of isolating the organisms obtained for further investigations, by using modern methods including DNA-analysis, appears to be the preferred method. Further investigations of the very ancient layers of the ice sheet by radioisotopic, luminescence, and scanning electron microscopy methods at different modifications, revealed the quantity and morphological diversity of the cells of microorganisms that were distributed on the different horizons. Investigations over many years have shown that the microflora in the very ancient strata of the Antarctic ice cover, nearest to the bedrock, support the effectiveness of using a combination of different methods

  2. Comparative Results of Using Different Methods for Discovery of Microorganisms in very Ancient Layers of the Central Antarctic Glacier above the Lake Vostok

    NASA Technical Reports Server (NTRS)

    Abyzov, S. S.; Hoover, R. B.; Imura, S.; Mitskevich, I. N.; Naganuma, T.; Poglazova, M. N.; Ivanov, M. V.

    2002-01-01

    The ice sheet of the Central Antarctic is considered by the scientific community worldwide, as a model to elaborate on different methods to search for life outside Earth. This became especially significant in connection with the discovery of the underglacial lake in the vicinity of the Russian Antarctic Station Vostok. Lake Vostok is considered by many scientists as an analog of the ice covered seas of Jupiter's satellite Europa. According to the opinion of many researchers there is the possibility that relict forms of microorganisms, well preserved since the Ice Age, may be present in this lake. Investigations throughout the thickness of the ice sheet above Lake Vostok show the presence of microorganisms belonging to different well-known taxonomic groups, even in the very ancient horizons near close to floor of the glacier. Different methods were used to search for microorganisms that are rarely found in the deep ancient layers of an ice sheet. The method of aseptic sampling from the ice cores and the results of controlled sterile conditions in all stages when conducting these investigations, are described in detail in previous reports. Primary investigations tried the usual methods of sowing samples onto different nutrient media, and the result was that only a few microorganisms grew on the media used. The possibility of isolating the organisms obtained for further investigations, by using modern methods including DNA-analysis, appears to be the preferred method. Further investigations of the very ancient layers of the ice sheet by radioisotopic, luminescence, and scanning electron microscopy methods at different modifications, revealed the quantity and morphological diversity of the cells of microorganisms that were distributed on the different horizons. Investigations over many years have shown that the microflora in the very ancient strata of the Antarctic ice cover, nearest to the bedrock, support the effectiveness of using a combination of different methods

  3. Environmental flow requirements in arid zone rivers--a case study from the Lake Eyre Basin, central Australia.

    PubMed

    Costelloe, J F; Puckridge, J T; Reid, J R W; Pritchard, J; Hudson, P; Bailey, V; Good, M

    2003-01-01

    The ARIDFLO project takes a multi-disciplinary approach to the collection and analysis of data required to formulate appropriate environmental flow requirements for rivers in the Lake Eyre Basin. The key drivers of the ecological processes underpinning the health of these rivers are identified by modelling whole-of-ecosystem biological responses to hydrological events over a range of spatial and temporal scales. First, the hydrology of these poorly gauged (often ungauged) rivers needs to be modelled and validated to mimic real flow and inundation patterns at the catchment, reach and waterbody scale. Modelled and actual discharge data are then used to provide a suite of hydrological predictor variables which, in conjunction with other environmental variables, are used to model observed biotic responses. The key hydrologic and environmental drivers identified by the statistical models need to be taken into account when determining environmental flow requirements for these river systems. Further work is required to assess the predictive power of the models in the highly variable, complex systems of the Lake Eyre Basin rivers.

  4. Holocene climate change and human impact, central Mexico: a record based on maar lake pollen and sediment chemistry

    NASA Astrophysics Data System (ADS)

    Park, Jungjae; Byrne, Roger; Böhnel, Harald; Garza, Roberto Molina; Conserva, Mariaelena

    2010-03-01

    This paper presents multiproxy (pollen, magnetic susceptibility, sediment chemistry) records from two maar crater lakes in the Valle de Santiago of Guanajuato, Mexico: Hoya San Nicolás and Hoya Rincon de Parangueo. Sediment cores from the two sites have basal dates of ca 11,600 and 9600 cal yr BP, respectively. The San Nicolás results show that the lake desiccated several times during the Holocene, and this resulted in the selective destruction of the less resistant pollen types. A comparative analysis of data from both sites indicates that during the earliest Holocene (ca 11,600-9000 cal yr BP) there were short term oscillations of wetter and drier climate; during the early Holocene (ca 9000-5700 cal yr BP) it was on average wetter; during the middle Holocene (ca 5700-3800 cal yr BP) drier; and during the middle to late Holocene (ca 3800-2200 cal yr BP) wetter. Increasing human disturbance during the late Holocene of environment obscures the climatic record. Agricultural activities in the area began as early as ca 5700 cal yr BP and intensified around 2400 cal yr BP.

  5. Geohydrology of the alluvial and terrace deposits of the North Canadian River from Oklahoma City to Eufaula Lake, central Oklahoma

    USGS Publications Warehouse

    Havens, J.S.

    1989-01-01

    This investigation was undertaken to describe the geohydrology of the alluvial and terrace deposits along the North Canadian River between Lake Overholser and Eufaula Lake, an area of about 1,835 square miles, and to determine the maximum annual yield of ground water. A 1982 water-level map of the alluvial and terrace aquifer was prepared using field data and published records. Data from test holes and other data from the files of the U.S. Geological Survey and the Oklahoma Water Resources Board were used to establish the approximate thickness of the alluvial and terrace deposits. The North Canadian River from Lake Overholser, near Oklahoma City, to Eufaula Lake is paralleled by a 2- to 3-mile wide band of alluvium. Scattered terrace deposits on either side of the alluvium reach an extreme width of 8 miles. Rocks of Permian age bound the alluvial and terrace deposits from the west to the midpoint of the study area; Pennsylvanian rocks bound the alluvial and terrace deposits from that point eastward. Three major aquifers are present in the study area: the alluvial and terrace aquifer, consisting of alluvium and terrace deposits of Quaternary age in a narrow band on either side of the North Canadian River; the Garber-Wellington aquifer of Permian age, consisting of an upper unconfined zone and a lower confined zone separated by relatively impermeable shales; and the Ada-Vamoosa aquifer of Pennsylvanian age. At locations were the alluvial and terrace aquifer overlies either of the other aquifers, there is hydraulic continuity between the alluvial and terrace aquifer and the other aquifers, and water levels are the same. Most large-scale municipal and industrial pumping from the Garber-Wellington aquifer is from the lower zone and has little discernible effect upon the alluvial and terrace aquifer. The total estimated base flow of the North Canadian River for the studied reach is 264 cubic feet per second. Evapotranspiration from the basin in August is about 60 cubic

  6. [Detection of methane in the water column at gas and oil seep sites in central and southern Lake Baikal].

    PubMed

    Zakharenko, A S; Pimenov, N V; Ivanov, V G; Zemskaia, T I

    2015-01-01

    Microbiological and biogeochemical investigation of the water column of oligotrophic Lake Baikal at the sites of the K2 and Bolshoy mud volcanoes and the Gorevoy Utes oil seep was carried out in July 2013. Total microbial numbers (TMN), cell numbers of type I and type II methanotrophs, and methane concentrations were measured; the rate of methane oxidation was determined. Methane concentrations in Lake Baikal water column varied from 0.09 to 1 μL/L, while methane oxidation rates varied from 0.007 to 0.9 nL/(L day). The highest rates of methane oxidation were revealed in the near-bottom water horizons at the sites of the Bolshoy mud volcano and the Gorevoy Utes oil seep. These were the sites where the most pronounced anomalies in methane concentration were also detected. TMN varied from 0.123 x 10(6) to 1.64 x 10(6) cells/mL. Methanotrophic bacteria were revealed in the water column at all sites, their abundance did not always correlate with methane concentrationsand the rates of methane oxidation. Methanotrophs constituted not more than 1.63% of the total microbial number, with their highest abundance in the upper 200 m of the water column.

  7. Lake Sharpe, South Dakota

    NASA Image and Video Library

    2014-03-26

    NASA Terra spacecraft views central South Dakota, where the Missouri River forms a meander bend, creating Lake Sharpe. Eventually, the Missouri River will cut through the skinny peninsula, creating a shorter path.

  8. Palaeoclimate reconstructions from lacustrine terraces and lake-balance modeling in the southern central Andes: New insights from Salar de Pocitos (Salta Province, Argentina)

    NASA Astrophysics Data System (ADS)

    Bekeschus, Benjamin; Bookhagen, Bodo; Strecker, Manfred R.; Freymark, Jessica; Eckelmann, Felix; Alonso, Ricardo

    2013-04-01

    The arid Puna Plateau in the southern central Andes of NW-Argentina constitutes the southern part of Earth's second largest orogenic plateau. Numerous internally drained basins are restricted by ranges that peak 5-6 km above sea level, creating a compressional basin and range morphology. The conspiring effects of this structurally controlled topography and the high degree of aridity have resulted in low stream power of the fluvial network and internally drained basins. A steep rainfall gradient exists across this area ranging from a humid Andean foreland (>1m/yr annual rainfall) to progressively drier areas westwards. At the present-day, the interior of the plateau is widely characterized by < 0.1m/yr annual rainfall and high evaporation rates. Thus continuous lacustrine archives are limited and sediments are dominated by evaporites. Several closed basins contain vestiges of moister conditions from past pluvial periods. For example, the staircase morphology of lacustrine shorelines and abrasion platforms in the distal sectors of alluvial fans and pediments at Salar de Pocitos (24.5°S, 67°W, 3650 m asl) records repeated former lake highstands. This intermontane basin has existed since the late Tertiary, constituting a 435 km² salt flat in the region of Salta, NW Argentina. Comparison with palaeoclimate records from the neighboring Salar de Atacama suggests that the terrace systems at Salar de Pocitos were formed during the Late Pleistocene and early Holocene. Here we report on our preliminary results of the extent of several terrace generations in this region. We mapped terraces in the field and on satellite images and determined their elevations during a high-resolution DGPS field survey. Our analysis reveals 3-4 distinct terrace levels associated with individual lake-level highstands. However, basin-wide correlation is difficult due to ongoing tectonism and differential tilting of the basin. The highest lake terrace, ca. 25 m above modern base level, locally

  9. Earth Observation

    NASA Image and Video Library

    2013-09-03

    ISS036-E-039778 (3 Sept. 2013) --- Caldera lakes to the northwest of Rome, Italy are featured in this image photographed by an Expedition 36 crew member on the International Space Station. The Lazio region of central Italy has many landforms of volcanic origin, including several large lakes that mark the locations of ancient volcanoes. This photograph highlights two such lakes, Lago di Vico and Lago Bracciano, located to the northwest of the capital city of Rome. Both lakes are located within calderas, large depressions that form after violent explosive eruptions empty a volcano’s underlying magma chamber. Any remnants of the volcanic edifice can then collapse into the newly-formed void space, leading to the creation of large depressions. These depressions can then fill partially or completely with water, forming permanent lakes. Lago Bracciano (left) is the larger of the two lakes highlighted in the image; it is approximately eight kilometers wide at its widest point, and is located 32 kilometers northwest of Rome. According to scientists, the volcanic activity that led to the formation of Lago Bracciano began approximately 600,000 years ago and continued to approximately 40,000 years ago as part of the formation of the Sabatini volcanic complex. While part of the lake formation was due to caldera collapse of part of a large magma chamber, the current depression was also formed by movement along numerous faults in the area – a process known as volcano-tectonic collapse. Located approximately 24 kilometers to the north-northwest of Lago Bracciano, Lago di Vico (right) occupies part of a caldera associated with eruptive activity that began approximately 800,000 years ago and continued until approximately 90,000 years ago. The caldera formed largely by the catastrophic eruption of the ancestral Vico volcano approximately 200,000-150,000 years ago. The final phase of volcanic activity in the caldera led to the formation of a small lava cone in the northeast

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

    USGS Publications Warehouse

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

    1991-01-01

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

  11. Continuation of the San Andreas fault system into the upper mantle: Evidence from spinel peridotite xenoliths in the Coyote Lake basalt, central California

    NASA Astrophysics Data System (ADS)

    Titus, Sarah J.; Medaris, L. Gordon; Wang, Herbert F.; Tikoff, Basil

    2007-01-01

    The Coyote Lake basalt, located near the intersection of the Hayward and Calaveras faults in central California, contains spinel peridotite xenoliths from the mantle beneath the San Andreas fault system. Six upper mantle xenoliths were studied in detail by a combination of petrologic techniques. Temperature estimates, obtained from three two-pyroxene geothermometers and the Al-in-orthopyroxene geothermometer, indicate that the xenoliths equilibrated at 970-1100 °C. A thermal model was used to estimate the corresponding depth of equilibration for these xenoliths, resulting in depths between 38 and 43 km. The lattice preferred orientation of olivine measured in five of the xenolith samples show strong point distributions of olivine crystallographic axes suggesting that fabrics formed under high-temperature conditions. Calculated seismic anisotropy values indicate an average shear wave anisotropy of 6%, higher than the anisotropy calculated from xenoliths from other tectonic environments. Using this value, the anisotropic layer responsible for fault-parallel shear wave splitting in central California is less than 100 km thick. The strong fabric preserved in the xenoliths suggests that a mantle shear zone exists below the Calaveras fault to a depth of at least 40 km, and combining xenolith petrofabrics with shear wave splitting studies helps distinguish between different models for deformation at depth beneath the San Andrea fault system.

  12. The record of Aplodontidae (Rodentia, Mammalia) in the Oligocene and Miocene of the Valley of Lakes (Central Mongolia) with some comments on the morphologic variability.

    PubMed

    Maridet, Olivier; Daxner-Höck, Gudrun; López-Guerrero, Paloma; Göhlich, Ursula B

    2017-01-01

    The present publication reports new discoveries of Oligocene and early Miocene aplodontid rodents from the Taatsiin Gol area (Valley of Lakes) in Mongolia. The fossil aplodontids recovered in this area are mainly composed of dental remains, some fragmentary jaws plus one partially preserved skull. Aplodontid rodents have been found from the early Oligocene (local biozone A) to the early middle Miocene (local biozone D). Altogether, eight taxa belonging to five genera have been identified in the investigated deposits: Ninamys arboraptus, Ninamys kazimierzi, Promeniscomys cf. sinensis, Prosciurus? mongoliensis and Prosciurus? sp. nov. in the early Oligocene; N. arboraptus, Proansomys badamae sp. nov. and Ansomyinae indet. in the late Oligocene; and Ansomys sp.1 in the early Miocene. In addition, although outside of the topic of the present special issue, one additional taxon, Ansomys sp.2, is reported from the ?middle Miocene. The material of aplodontids is usually relatively scarce in Asian localities. For the first time, with a sample size of 81 specimens, the material from Central Mongolia (mainly from the Oligocene) now allows a more accurate description of the morphological and size variability and resolves some systematic problems. The study of these aplodontids reveals that they are more abundant and diverse in the early Oligocene and that the diversity decreases during the late Oligocene and Miocene. One hypothesis, to explain the opposite diversity trend observed previously for sciurids in the same region, is that both Sciuromorpha families might have competed for the same resources from the early Oligocene to the middle Miocene in Central Mongolia.

  13. High environmental variability in the monsoon-westerlies transition area of Asia during the last 1200 years: lake sediment analyses from central Mongolia and supra-regional synthesis

    NASA Astrophysics Data System (ADS)

    Tian, Fang; Herzschuh, Ulrike; Dallmeyer, Anne; Xu, Qinghai; Mischke, Steffen; Biskaborn, Boris K.

    2013-04-01

    A high resolution multi-proxy (pollen, grain size distribution, total organic carbon) record from a small mountain lake (Lake Khuisiin; 46.6°N, 101.8°E; 2270 m a.s.l.) in the south-eastern Khangai Mountains of central Mongolia has been used to explore changes in vegetation and climate over the last 1200 years. The pollen data indicates that the vegetation changed from dry steppe dominated by Poaceae and Artemisia (ca. AD 760-950), to Larix forest steppe (ca. AD 950-1170), Larix-Betula forest steppe (ca. AD 1170-1380), meadow dominated by Cyperaceae and Poaceae (ca. AD 1380-1830), and Larix-Betula forest steppe (after ~AD 1830). There was no consistent evidence of warming during the Medieval Warm Period, but the cold wet period between AD 1380 and 1830 may relate to the Little Ice Age. Environmental changes were generally subtle and climate change seems to have been the major driver of variations in vegetation until at least the early part of the 20th century, suggesting that either the level of human activity was generally low, or the relationship between human activity and vegetation did not alter substantially between AD 760 and 1830. A review of centennial-scale moisture records from China and Mongolia revealed that most areas experienced major changes at ca. AD 1500 and AD 1900. However, the moisture availability since AD 1500 varied between sites, with no clear regional pattern or relationship to present-day conditions. Both the reconstructions and the moisture levels simulation on the millennium scale preformed in the MPI Earth System Model indicate that the monsoon-westerlies transition area shows a higher climate variability than the areas purely influenced by the westerlies or the summer monsoon.

  14. Environmental variability in the monsoon-westerlies transition zone during the last 1200 years: lake sediment analyses from central Mongolia and supra-regional synthesis

    NASA Astrophysics Data System (ADS)

    Tian, Fang; Herzschuh, Ulrike; Dallmeyer, Anne; Xu, Qinghai; Mischke, Steffen; Biskaborn, Boris K.

    2013-08-01

    A high resolution multi-proxy (pollen, grain size, total organic carbon) record from a small mountain lake (Lake Khuisiin; 46.6°N, 101.8°E; 2270 m a.s.l.) in the south-eastern Khangai Mountains of central Mongolia has been used to explore changes in vegetation and climate over the last 1200 years. The pollen data indicates that the vegetation changed from dry steppe dominated by Poaceae and Artemisia (ca AD 760-950), to Larix forest steppe (ca AD 950-1170), Larix-Betula forest steppe (ca AD 1170-1380), meadow dominated by Cyperaceae and Poaceae (ca AD 1380-1830), and Larix-Betula forest steppe (after ˜ AD 1830). The cold-wet period between AD 1380 and 1830 may relate to the Little Ice Age. Environmental changes were generally subtle and climate change seems to have been the major driver of variations in vegetation until at least the early part of the 20th century, suggesting that either the level of human activity was generally low, or the relationship between human activity and vegetation did not alter substantially between AD 760 and 1830. A review of centennial-scale moisture records from China and Mongolia revealed that most areas experienced major changes at ca AD 1500 and AD 1900. However, the moisture availability since AD 1500 varied between sites, with no clear regional pattern or relationship to present-day conditions. Both the reconstructions and the moisture levels simulation on a millennium scale performed in the MPI Earth System Model indicate that the monsoon-westerlies transition area shows a greater climate variability than those areas influenced by the westerlies, or by the summer monsoon only.

  15. Lake Store Finnsjøen - a key for understanding Lateglacial/early Holocene vegetation and ice sheet dynamics in the central Scandes Mountains

    NASA Astrophysics Data System (ADS)

    Paus, Aage; Boessenkool, Sanne; Brochmann, Christian; Epp, Laura Saskia; Fabel, Derek; Haflidason, Haflidi; Linge, Henriette

    2015-08-01

    The Lateglacial (LG) deglaciation and vegetation development in the Scandes Mountains has been debated for a century. Here we present new evidence from microfossils, radiocarbon dated plant macrofossils and sedimentary ancient DNA from laminated sediments in Lake Store Finnsjøen (1260 m a.s.l.) at Dovre, Central Norway. Combined with previous results from three other Dovre lakes, this allows for new interpretations of events during and immediately after the LG deglaciation. The Finnsjøen sediments present the first uninterrupted record of local vegetation development in the Scandes Mountains from the late Younger Dryas (YD), ca 12,000 cal years BP, to the early Holocene around 9700 cal years BP. The local vegetation in late YD/early Holocene was extremely sparse with pioneer herbs (e.g. Artemisia norvegica, Beckwithia, Campanula cf. uniflora, Koenigia, Oxyria, Papaver, Saxifraga spp.) and dwarf-shrubs (Betula nana, Salix including Salix polaris). From 11,300 cal years BP, local vegetation rapidly closed with dominant Dryas, Saxifraga spp., and Silene acaulis. From ca 10,700 cal years BP, open birch-forests with juniper, Empetrum nigrum and other dwarf-shrubs developed. Pine forests established within the area from 10,300 cal years BP. We identified the cold Preboreal Oscillation (PBO), not earlier described from pollen data in South Norway, around 11,400 cal years BP by a regional pollen signal. Distinct local vegetation changes were not detected until the post-PBO warming around 11,300 cal years BP. Apparently, the earlier warming at the YD/Holocene transition at 11,650 cal years BP was too weak and short-lived for vegetation closure at high altitudes at Dovre. For the first time, we demonstrate a regional glacier readvance and local ice cap formations during the YD in the Scandes Mountains. In two of the deep lakes with small catchments, YD glaciation blocked sedimentation without removing old sediments and caused a hiatus separating sediments of the ice

  16. Simulation of the effects of rainfall and groundwater use on historical lake water levels, groundwater levels, and spring flows in central Florida

    USGS Publications Warehouse

    O'Reilly, Andrew M.; Roehl, Edwin A.; Conrads, Paul A.; Daamen, Ruby C.; Petkewich, Matthew D.

    2014-01-01

    The urbanization of central Florida has progressed substantially in recent decades, and the total population in Lake, Orange, Osceola, Polk, and Seminole Counties more than quadrupled from 1960 to 2010. The Floridan aquifer system is the primary source of water for potable, industrial, and agricultural purposes in central Florida. Despite increases in groundwater withdrawals to meet the demand of population growth, recharge derived by infiltration of rainfall in the well-drained karst terrain of central Florida is the largest component of the long-term water balance of the Floridan aquifer system. To complement existing physics-based groundwater flow models, artificial neural networks and other data-mining techniques were used to simulate historical lake water level, groundwater level, and spring flow at sites throughout the area. Historical data were examined using descriptive statistics, cluster analysis, and other exploratory analysis techniques to assess their suitability for more intensive data-mining analysis. Linear trend analyses of meteorological data collected by the National Oceanic and Atmospheric Administration at 21 sites indicate 67 percent of sites exhibited upward trends in air temperature over at least a 45-year period of record, whereas 76 percent exhibited downward trends in rainfall over at least a 95-year period of record. Likewise, linear trend analyses of hydrologic response data, which have varied periods of record ranging in length from 10 to 79 years, indicate that water levels in lakes (307 sites) were about evenly split between upward and downward trends, whereas water levels in 69 percent of wells (out of 455 sites) and flows in 68 percent of springs (out of 19 sites) exhibited downward trends. Total groundwater use in the study area increased from about 250 million gallons per day (Mgal/d) in 1958 to about 590 Mgal/d in 1980 and remained relatively stable from 1981 to 2008, with a minimum of 559 Mgal/d in 1994 and a maximum of 773

  17. Improved age modelling approaches as exemplified by the revised chronology for the Central European varved lake Soppensee

    NASA Astrophysics Data System (ADS)

    Blockley, S. P. E.; Ramsey, C. Bronk; Lane, C. S.; Lotter, A. F.

    2008-01-01

    One of the key factors in understanding past climate change is the development of robust age models that have sufficient chronological precision for comparing different palaeoclimate archives, while retaining accuracy. Recent developments in Bayesian age modelling are applied here to the Swiss varve lake, Soppensee. We develop revised age models for this sequence using the available stratigraphic information to constrain the calibrated radiocarbon ages. We begin by using stratigraphical order as the only constraint and then sequentially increase the information incorporated into the model, using relative varve age, sample depth, and varying depositional models. Within this Bayesian framework, we develop internally robust models that significantly improve the dating precision and are applicable to both varved and non-varved sequences. We then compare the model output to wider chronological information, such as the age of the Laacher See Tephra in order to test the model accuracy. The results of this exercise suggest that these methods can be used to build very reliable improved age models in a variety of records.

  18. Establishment patterns of water-elm at Catahoula Lake, Louisiana

    Treesearch

    Karen S. Doerr; Sanjeev Joshi; Richard F. Keim

    2015-01-01

    At Catahoula Lake in central Louisiana, an internationally important lake for water fowl, hydrologic alterations to the surrounding rivers and the lake itself have led to an expansion of water-elm (Planera aquatic J.F. Gmel.) into the lake bed. In this study, we used dendrochronology and aerial photography to quantify the expansion of water-elm in the lake and identify...

  19. Mid- to Late Holocene climate development in Central Asia as revealed from multi-proxy analyses of sediments from Lake Son Kol (Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Lauterbach, Stefan; Dulski, Peter; Gleixner, Gerd; Hettler-Riedel, Sabine; Mingram, Jens; Plessen, Birgit; Prasad, Sushma; Schwalb, Antje; Schwarz, Anja; Stebich, Martina; Witt, Roman

    2013-04-01

    A mid-Holocene shift from predominantly wet to significantly drier climate conditions, attributed to the weakening of the Asian summer monsoon (ASM), is documented in numerous palaeoclimate records from the monsoon-influenced parts of Asia, e.g. the Tibetan Plateau and north- and southeastern China. In contrast, Holocene climate development in the arid regions of mid-latitude Central Asia, located north and northwest of the Tibetan Plateau, is less well-constrained but supposed to have been influenced by a complex interaction between the mid-latitude Westerlies and the ASM. Hence, well-dated and highly resolved palaeoclimate records from Central Asia might provide important information about spatio-temporal changes in the regional interplay between Westerlies and ASM and thus aid the understanding of global climate teleconnections. As a part of the project CADY (Central Asian Climate Dynamics), aiming at reconstructing past climatic and hydrological variability in Central Asia, several sediment cores were recovered from alpine Lake Son Kol (41° 48'N, 75° 12'E, 3016 m a. s. l.) in the Central Tian Shan of Kyrgyzstan. A radiocarbon-dated sediment sequence of 154.5 cm length, covering approximately the last 6000 years, was investigated by using a multi-proxy approach, including sedimentological, (bio)geochemical, isotopic and micropalaeontological analyses. Preliminary proxy data indicate hydrologically variable but predominantly wet conditions until ca. 5100 cal. a BP, characterized by the deposition of finely laminated organic-carbonatic sediments. In contrast to monsoonal Asia, where a distinct trend towards drier conditions is observed since the mid-Holocene, the hydrologically variable interval at Lake Son Kol was apparently followed by an only short-term dry episode between ca. 5100 and 4200 cal. a BP. This is characterized by a higher δD of the C29 n-alkanes, probably reflecting increased evapotranspiration. Also pollen, diatom and ostracod data point

  20. A comprehensive assessment of agricultural intensification scenarios for the Dongting Lake basin in south-central China in 2030.

    PubMed

    Yin, Guanyi; Liu, Liming; Chang, Xiao; Sun, Jin

    2016-07-01

    To explore the future of the material demand, pollutant emission, production, and arable land area surrounding the Dongting Lake basin, and to find a potential solution for agricultural development, this study assumes the following four agriculture intensification scenarios: the natural development scenario (ND), the production development scenario (PD), the moderate intensification scenario (MI), and the local resilience scenario (LR). The scenarios focus on different developmental patterns (natural development, short-term production growth, long-term sustainability, or self-sufficiency).The result shows to satisfy the food demand in 2030, and the production of crop and meat will be 26.96, 30.25, 28.05, and 16.27 × 10(6) t in ND, PD, MI, and LR, respectively; more than 1.78 × 10(6) ha of arable land is needed. Compared with the year 2012, the material input and pollutant output will increase by a maximum of 18.32 and 122.31 %, respectively. By classifying the environmental risk into four categories-greenhouse gas emission, air pollution, eutrophication, and ecotoxicity-the composite environmental risk index (CER) is calculated. The CER in PD was the highest, followed by that in ND, LR, and MI. Due to the production allocation within the 35 cities and counties, the spatial distribution of CER is more homogenous in PD and MI than in ND. The analysis of the scenarios reveals that through technological improvement and spatial allocation of agricultural production, scenario MI could be a potential direction for the government to design a sustainable agricultural-environmental system.

  1. Planning applications in east central Florida. [resources management and planning, land use, and lake algal blooms in Brevard County from Skylab imagery

    NASA Technical Reports Server (NTRS)

    Hannah, J. W.; Thomas, G. L.; Esparza, F. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Lake Apopka and three lakes downstream of it (Dora, Eustis, and Griffin) are in an advanced state of eutrophication with high algal concentrations. This feature has shown up consistently on ERTS-1 images in the form of a characteristic water color for those lakes. As expected, EREP photographs also show a characteristic color for those lakes. What was not expected is that Lake Griffin shows a clear pattern of this coloration. Personnel familiar with the lake believe that the photograph does, indeed, show an algal bloom. It is reported that the algal concentration is often significantly higher in the southern portion of the lake. What the photograph shows that was not otherwise known is the pattern of the algal bloom. A similar, but less pronounced, effect is seen in Lake Tohopekaliga. Personnel stationed at Kissimmee reported that there was an algal bloom on that lake at the time of the EREP pass and that its extent corresponded approximately to that shown on the photograph. Again, the EREP photograph gives information about the extent of the bloom that could not be obtained practically by sampling. ERTS-1 images give some indication of this algal distribution on Lake Griffin in some cases, but are inconclusive.

  2. A 3000-year record of ground-rupturing earthquakes along the central North Anatolian fault near Lake Ladik, Turkey

    USGS Publications Warehouse

    Fraser, J.; Pigati, J.S.; Hubert-Ferrari, A.; Vanneste, K.; Avsar, U.; Altinok, S.

    2009-01-01

    The North Anatolian fault (NAF) is a ???1500 km long, arcuate, dextral strike-slip fault zone in northern Turkey that extends from the Karliova triple junction to the Aegean Sea. East of Bolu, the fault zone exhibits evidence of a sequence of large (Mw >7) earthquakes that occurred during the twentieth century that displayed a migrating earthquake sequence from east to west. Prolonged human occupation in this region provides an extensive, but not exhaustive, historical record of large earthquakes prior to the twentieth century that covers much of the last 2000 yr. In this study, we extend our knowledge of rupture events in the region by evaluating the stratigraphy and chronology of sediments exposed in a paleoseismic trench across a splay of the NAF at Destek, ???6:5 km east of Lake Ladik (40.868?? N, 36.121?? E). The trenched fault strand forms an uphill-facing scarp and associated sediment trap below a small catchment area. The trench exposed a narrow fault zone that has juxtaposed a sequence of weakly defined paleosols interbedded with colluvium against highly fractured bedrock. We mapped magnetic susceptibility variations on the trench walls and found evidence for multiple visually unrecognized colluvial wedges. This technique was also used to constrain a predominantly dip-slip style of displacement on this fault splay. Sediments exposed in the trench were dated using both charcoal and terrestrial gastropod shells to constrain the timing of the earthquake events. While the gastropod shells consistently yielded 14 C ages that were too old (by ???900 yr), we obtained highly reliable 14 C ages from the charcoal by dating multiple components of the sample material. Our radiocarbon chronology constrains the timing of seven large earthquakes over the past 3000 yr prior to the 1943 Tosya earthquake, including event ages of (2?? error): A.D. 1437-1788, A.D. 1034-1321, A.D. 549-719, A.D. 17-585 (1-3 events), 35 B.C.-A.D. 28, 700-392 B.C., 912-596 B.C. Our results

  3. Transit losses and traveltimes for water-supply releases Marion Lake during drought conditions, Cottonwood River, east-central Kansas

    USGS Publications Warehouse

    Jordan, P.R.; Hart, R.J.

    1985-01-01

    A streamflow routing model was used to calculate the transit losses and traveltimes. Channel and aquifer characteristics, and the model control parameters, were estimated from available data and then verified to the extent possible by comparing model simulated streamflow to observed streamflow at streamflow gaging stations. Transit losses and traveltimes for varying reservoir release rates and durations then were simulated for two different antecedent streamflow (drought) conditions. For the severe-drought antecedent-streamflow condition, it was assumed that only the downstream water use requirement would be released from the reservoir. For a less severe drought (LSD) antecedent streamflow condition, it was assumed than any releases from Marion Lake for water supply use downstream, would be in addition to a nominal dry weather release of 5 cu ft/sec. Water supply release rates of 10 and 25 cu ft/sec for the severe drought condition and 5, 10, and 25 cu ft/sec for the less severe drought condition were simulated for periods of 28 and 183 days commencing on July 1. Transit losses for the severe drought condition for all reservoir release rates and durations ranged from 12% to 78% of the maximum downstream flow rate and from 27% to 91% of the total volume of reservoir storage released. For the LSD condition, transit losses ranged from 7% to 29% of the maximum downstream flow rate and from 10% to 48% of the total volume of release. The 183-day releases had larger total transit losses, but losses on a percentage basis were less than the losses for the 28-day release period for both antecedent streamflow conditions. Traveltimes to full response (80% of the maximum downstream flow rate), however, showed considerable variation. For the release of 5 cu ft/sec during LSD conditions, base flow exceeded 80% of the maximum flow rate near the confluence; the traveltime to full response was undefined for those simulations. For the releases of 10 and 25 cu ft/sec during the same

  4. Evaluation of the Steel Lake chronology and the uncertainty in timing of major pollen transitions in the north-central US

    NASA Astrophysics Data System (ADS)

    Myrbo, A.; Blaauw, M.; Christen, J. A.; Stefanova, I.; Wright, H. E.

    2010-12-01

    Steel Lake, Minnesota, USA (Wright et al., 2004), has a robust radiocarbon chronology and one of the best existing pollen diagrams for the much-studied prairie-forest boundary region of the north-central US. We evaluate the uncertainties of this chronology, which is based on 26 AMS radiocarbon dates over ~11,000 calendar years, using Bayesian age-depth modeling (Bacon; Blaauw and Christen, submitted). Although much of the chronology is well-constrained, gaps between successive dated horizons and relatively large laboratory errors in dates >9000 14C years provide substantial uncertainty across some thresholds of major vegetational change. Comparison of the Bacon and published LOWESS age-depth models for this sedimentary sequence demonstrates the drawbacks of “classical” age-depth modeling, wherein a single curve is drawn through, e.g., midpoints of calibrated ages. Bacon transparently provides a visual and numerical statement of uncertainty in both the chronology and the timing associated with proxy records by constructing a flexible age-depth model and including a priori information on accumulation rates. To reduce uncertainty in the age-depth model, a sampling-design analysis that evaluates the optimal depth horizons for additional dates provides a “batch” of ten recommended dating targets. In addition, we statistically evaluate the time-transgressive nature of the early-Holocene Picea (spruce) decline and of the initiation of the mid-Holocene “prairie period” across an east-west transect of the north-central US. Blaauw M, Christen JA. Flexible paleoclimate age-depth models using an autoregressive gamma process. Submitted to Bayesian Analysis

  5. The chemistry of playa-lake-sediments as a tool for the reconstruction of Holocene environmental conditions - a case study from the central Ebro basin

    NASA Astrophysics Data System (ADS)

    Schütt, Brigitta

    The focus of the presented study is the reconstruction of the Holocene limnic and drainage basin conditions of the Laguna de Jabonera, a today playa-lake-system in the Desierto de Calanda, central Ebro Basin, using the inorganic characters of the lacustrine sediments. Mineralogical fabric helped to reconstruct the overall geomorphic processes and gives clues to the synsedimentary limnic environment (paleosalinity). The chemical composition of the lacustrine sediments largely reflects the mineralogical composition, but the higher resolution of the geochemical data compared to the mineralogical data enables to stratigraphically split the extracted core profile into three stratigraphic units. Supplementally, it is demonstrated that Statistics between chemical compounds point to the synsedimentary intensity of weathering and soil forming processes. As for the lacustrine sediments investigated there are no data yet available a preliminary chronological framework is derived by comparison with results from neighbouring areas. Based on this the hypothesis is put forward that during the socalled Little Ice Age subhumid to dry-subhumid environmental conditions occurred. Also possibly during the late Subboreal distinct wetter environmental conditions than today prevailed. Additionally, it is demonstrated that in the most recent past human impact is causing increased erosion rates and, thus, increased deposition of detritals in the most recent lacustrine sediments.

  6. Inference of the viscosity structure and mantle conditions beneath the Central Nevada Seismic Belt from combined postseismic and lake unloading studies

    NASA Astrophysics Data System (ADS)

    Dickinson, Haylee; Freed, Andrew M.; Andronicos, Christopher

    2016-05-01

    We test whether a single depth-dependent Newtonian viscosity structure can be found to explain measured surface deformation in Western Nevada from two separate loading events: tectonic loading from a series of seven historic earthquakes in the Central Nevada Seismic Belt and nontectonic loading from the formation and evaporation of co-located Pleistocene-aged Lake Lahontan. Rheologic studies are generally plagued with nonuniqueness issues due to the limitations of observational constraints. Here, we reduce nonuniqueness by solving for a single rheologic structure that can simultaneously satisfy all observational constraints associated with all events. Model results suggest that Western Nevada is underlain by a strong lower crust (order 1020 Pa s), a relatively weak mantle (order 5 × 1018 Pa s) from 40 to 80 km, and a much weaker mantle (order 1018 Pa s) below 80 km. We would thus place the mechanical lithosphere/asthenosphere boundary (LAB) at 40 km depth. Thermal modeling of conductive geothermal gradients, combined with melting curves calculated for enriched and depleted mantle compositions suggest that the viscosity decrease at 40 km depth (the LAB) is associated with the onset of wet melting of mantle lithosphere hydrated by past subduction and is about 10 km shallower than the inferred transition from conduction to convection.

  7. Temperate and semi-arid tufas in the Pleistocene to Recent fluvial barrage system in the Mediterranean area: The Ruidera Lakes Natural Park (Central Spain)

    NASA Astrophysics Data System (ADS)

    Ordóñez, S.; González Martín, J. A.; García del Cura, M. A.; Pedley, H. M.

    2005-07-01

    The Ruidera Lakes Natural Park, in Central Spain, contains a well-exposed Pleistocene to Recent freshwater carbonate (tufa) succession dominated by fluvial barrages and lacustrine deposits. The majority of exposed tufas are Holocene to Recent in age. Today, carbonate accumulation is currently manifested as active phytoherm barrage constructions, marginal lacustrine stromatolitic terraces, lacustrine lime muds (all produced mainly by precipitation) and sand-size detrital tufa. The depositional history of the Ruidera Park sites has been interpreted from natural outcrops, rotary drill and percussion auger cores. These reveal a long Quaternary record of microbially dominated barrage framework developments and associated lacustrine carbonates. These alternate with frost weathering deposits and detrital tufa episodes, especially during cooler conditions. U-series dating of several earlier tufa deposits within the park indicates four distinct episodes of tufa development at 190-250 ka B.P., 90-130 ka B.P., 30-40 ka B.P. and 16 ka B.P.-Present. The three oldest episodes appear to be related to cyclic tufa-building events associated with warm periods of Oxygen Isotope Stages (OIS): 7, 5 and 3. Growth under present conditions is slow and several barrages have been damaged by human activity and drought events.

  8. Inferring local to regional changes in forest composition from Holocene macrofossils and pollen of a small lake in central Upper Michigan

    NASA Astrophysics Data System (ADS)

    Jackson, Stephen T.; Booth, Robert K.; Reeves, Kelly; Andersen, Jennifer Jewell; Minckley, Thomas A.; Jones, Rachel A.

    2014-08-01

    Vegetational response to climatic change involves processes of population and community dynamics within local stands, which scale up to landscape-level changes in vegetation composition and broad-scale changes in species distributions. Understanding these dynamics poses a critical challenge to paleoecological explanation, because of the broad range of scales at which these dynamics take place and interact. We present an 8600-year paleoecological record of local and regional changes in forest composition from a small (2.6 ha) lake in central Upper Michigan. Plant macrofossils provide a spatially precise record of local forest composition, while pollen data provide a spatially integrated record of regional vegetational changes. Temporal patterns among different macrofossil types within species show overall coherence, indicating that changes in macrofossil abundance generally record changes in local tree abundance. Temporal patterns in macrofossil sequences correspond to patterns in pollen sequences, indicating that local changes contributed to the large-scale changes in the surrounding region. The pollen and macrofossil records show nearly continuous turnover in vegetation composition throughout the past 8600 years; the longest period without major compositional change was ca 1600 years, and dynamics at multidecadal to multicentennial scales are observed during many periods. Coordinated application of temporally precise sequences of pollen and macrofossil data at multiple sites can support inferences concerning vegetation dynamics at multiple spatial and temporal scales, and test mechanistic hypotheses.

  9. Glacial lake inventory and lake outburst potential in Uzbekistan.

    PubMed

    Petrov, Maxim A; Sabitov, Timur Y; Tomashevskaya, Irina G; Glazirin, Gleb E; Chernomorets, Sergey S; Savernyuk, Elena A; Tutubalina, Olga V; Petrakov, Dmitriy A; Sokolov, Leonid S; Dokukin, Mikhail D; Mountrakis, Giorgos; Ruiz-Villanueva, Virginia; Stoffel, Markus

    2017-03-16

    Climate change has been shown to increase the number of mountain lakes across various mountain ranges in the World. In Central Asia, and in particular on the territory of Uzbekistan, a detailed assessment of glacier lakes and their evolution over time is, however lacking. For this reason we created the first detailed inventory of mountain lakes of Uzbekistan based on recent (2002-2014) satellite observations using WorldView-2, SPOT5, and IKONOS imagery with a spatial resolution from 2 to 10m. This record was complemented with data from field studies of the last 50years. The previous data were mostly in the form of inventories of lakes, available in Soviet archives, and primarily included localized in-situ data. The inventory of mountain lakes presented here, by contrast, includes an overview of all lakes of the territory of Uzbekistan. Lakes were considered if they were located at altitudes above 1500m and if lakes had an area exceeding 100m(2). As in other mountain regions of the World, the ongoing increase of air temperatures has led to an increase in lake number and area. Moreover, the frequency and overall number of lake outburst events have been on the rise as well. Therefore, we also present the first outburst assessment with an updated version of well-known approaches considering local climate features and event histories. As a result, out of the 242 lakes identified on the territory of Uzbekistan, 15% are considered prone to outburst, 10% of these lakes have been assigned low outburst potential and the remainder of the lakes have an average level of outburst potential. We conclude that the distribution of lakes by elevation shows a significant influence on lake area and hazard potential. No significant differences, by contrast, exist between the distribution of lake area, outburst potential, and lake location with respect to glaciers by regions.

  10. Piping Plover Habitat Loss at the Nature Conservancy's John E. Williams Preserve, Central North Dakota: an Interdisciplinary Study of Alkaline Prairie Pothole Glacial Lakes, Groundwater, Gravel Beaches and Vegetation Encroachment

    NASA Astrophysics Data System (ADS)

    Sciamanda, M.; Kellner, J. R.; Lamb, M. A.; Clotts, R.; Pastika, D. W.; Welter, D. J.; Brown, J. M.; Schuweiler, T. K.; Mohanty, R. B.; Vang, K. M.; Nichols, K. S.; Lorah, P. A.; Robinson, D. O.

    2016-12-01

    The Piping Plover (Charadrius melodus) is a threatened migratory bird that nests along shores of alkaline lakes, the Great Lakes, and the Atlantic Ocean. John Williams Preserve, in central North Dakota, houses one of the largest breeding populations in the world. Over the past eighty years, vegetation has encroached and caused variable habitat loss from lake to lake (Root and Ryan, 2004). Processes operating on different time scales affect lake, beach and vegetation changes: long-term global climate changes, decadal drought cycles, and seasonal and local weather. To determine how these processes interact to affect vegetation growth, soil salinity and habitat loss, we began a multidisciplinary field study. Sampled lake cores provide a chemical record of historical events and possible habitat changes. Water chemistry samples taken in different months inform groundwater flow patterns and core interpretation. Spatial analyses of local and regional groundwater systems informed placement of piezometers to determine groundwater flow. Aerial drone imagery builds on previous ground studies and allows for a quantitative spatial analysis of vegetation encroachment and geomorphic analyses. The three main lakes in our study show a general increase in concentration of major ions from east to west —from Pelican to Peterson to Williams—that mirrors westerly groundwater flow. Geochemical data from sediment cores, including LOI, XRD and XRF data, show that Williams is the most variable chemically, Pelican the least. Williams contains the most evaporate minerals, including thernardite and burkeite. Land use changes in the last 120 years may have changed lake chemistry: at 60 cm depth in cores, there are changes in the organic matter concentration and major ion chemistry, suggesting an increase in runoff and sediment input. Historical research points to changing agricultural practices as a possible cause of these changes. Initial ArcGIS analyses of detailed drone topographic data

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

    USGS Publications Warehouse

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

    2001-01-01

    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.

  12. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 02LCA02 in Lakes Ada, Crystal, Jennie, Mary, Rice, and Sylvan, Central Florida, July 2002

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Davis, Jeffrey B.; Wiese, Dana S.

    2008-01-01

    In July of 2002, the U.S. Geological Survey and St. Johns River Water Management District (SJRWMD) conducted geophysical surveys in Lakes Ada, Crystal, Jennie, Mary, Rice, and Sylvan, central Florida, as part of the USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 02LCA02 tells us the data were collected in 2002 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the second field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when discharged emits a short acoustic pulse, or shot, which propagates through the water, sediment column, or rock beneath. The acoustic energy is reflected at density boundaries (such as the seafloor, sediment, or rock layers beneath the

  13. Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activity 08LCA01 in 10 Central Florida Lakes, March 2008

    USGS Publications Warehouse

    Harrison, Arnell S.; Dadisman, Shawn V.; Davis, Jeffrey B.; Flocks, James G.; Wiese, Dana S.

    2009-01-01

    In March of 2008, the U.S. Geological Survey and St. Johns River Water Management District (SJRWMD) conducted geophysical surveys in Lakes Avalon, Big, Colby, Helen, Johns, Prevatt, Searcy, Saunders, Three Island, and Trout, located in central Florida, as part of the USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Field Activity Collection System (FACS) logs, Geographic Information System (GIS) files, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2005). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 08LCA01 tells us the data were collected in 2008 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the first field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The naming convention used for each seismic line is as follows: yye##a, where yy is the last two digits of the year in which the data were collected, e is a 1-letter abbreviation for the equipment type (for example, b for boomer), ## is a 2-digit number representing a specific track, and a is a letter representing the section of a line

  14. Water budget and water quality of Ward Lake, flow and water-quality characteristics of the Braden River estuary, and the effects of Ward Lake on the hydrologic system, west-central Florida

    USGS Publications Warehouse

    Trommer, J.T.; DelCharco, M.J.; Lewelling, B.R.

    1999-01-01

    The Braden River is the largest tributary to the Manatee River. The river was dammed in 1936 to provide the city of Bradenton a source of freshwater supply. The resulting impoundment was called Ward Lake and had a storage capacity of about 585 million gallons. Reconstruction in 1985 increased the size of the reservoir to about 1,400 million gallons. The lake has been renamed the Bill Evers Reservoir and drains about 59 square miles. The Braden River watershed can be subdivided into three hydrologic reaches. The upper reach consists of a naturally incised free-flowing channel. The middle reach consists of a meandering channel affected by backwater as a result of the dam. The lower reach is a tidal estuary. Water budgets were calculated for the 1993 through 1997 water years. Mean surface-water inflow to Ward Lake for the 5-year period was 1,645 inches per year (equivalent depth over the surface of the lake), or about 81.8 percent of total inflow. Mean ground-water inflow was 311 inches per year, or about 15.5 percent. A mean of 55 inches of rain fell directly on the lake and accounted for only 2.7 percent. Mean surface-water outflow was 1,736 inches, or about 86.4 percent of total water leaving the lake. There was no net ground-water outflow from the lake. Mean surface-water withdrawal for public supply was 229 inches per year, or about 11.4 percent. Mean evaporation was 45 inches and accounted for only 2.2 percent of the mean outflow. Change in lake storage on the budget was negligible. Most chemical constituents contained in water flowing to Ward Lake meet the standards specified by the Florida Department of Environmental Protection and the U.S. Environmental Protection Agency. Phosphorus is the exception, exceeding the U.S. Environmental Protection Agency limits of 0.10 milligram per liter in most samples. However, the source of the phosphorus is naturally occurring phosphate deposits underlying the watershed. Organic nitrogen and orthophosphate are the dominant

  15. Arsenic and lead distribution and mobility in lake sediments in the south-central Puget Sound watershed: the long-term impact of a metal smelter in Ruston, Washington, USA.

    PubMed

    Gawel, James E; Asplund, Jessica A; Burdick, Sarah; Miller, Michelle; Peterson, Shawna M; Tollefson, Amanda; Ziegler, Kara

    2014-02-15

    The American Smelting and Refining Company (ASARCO) smelter in Ruston, Washington, contaminated the south-central Puget Sound region with heavy metals, including arsenic and lead. Arsenic and lead distribution in surface sediments of 26 lakes is significantly correlated with atmospheric model predictions of contaminant deposition spatially, with concentrations reaching 208 mg/kg As and 1,375 mg/kg Pb. The temporal distribution of these metals in sediment cores is consistent with the years of operation of the ASARCO smelter. In several lakes arsenic and lead levels are highest at the surface, suggesting ongoing inputs or redistribution of contaminants. Moreover, this study finds that arsenic is highly mobile in these urban lakes, with maximum dissolved arsenic concentrations proportional to surface sediment levels and reaching almost 90 μg/L As. With 83% of the lakes in the deposition zone having surface sediments exceeding published "probable effects concentrations" for arsenic and lead, this study provides evidence for possible ongoing environmental health concerns. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Lake Life.

    ERIC Educational Resources Information Center

    Ohrn, Deborah Gore, Ed.

    1993-01-01

    This quarterly publication of the State Historical Society of Iowa features articles and activities for elementary school students. This summer issue focuses on the topic of lake life. The issue includes the following features: (1) "Where the Lakes Are Map"; (2) "Letter from the Lake"; (3) "Lake People"; (4)…

  17. Water, Energy, and Biogeochemical Budgets (WEBB) program: Data availability and research at the Northern Temperate Lakes site in north-central Wisconsin

    USGS Publications Warehouse

    Elder, John F.; Krabbenhoft, David P.; Walker, John F.

    1992-01-01

    The NTL-WEBB study area includes seven lakes that are also the site of a Long-Term Ecological Research (LTER) project, sponsored by the National Science Foundation. This project incorporates diverse research investigations conducted by faculty and research associates of the University of Wisconsin-Madison. The research orientation of NTL-LTER is principally toward aquatic ecology and geochemistry of the lakes. The WEBB research plan, with its emphasis on hydrologic processes in the lake watersheds, is designed to complement and enhance the LTER work.

  18. Paleoecological studies at Lake Patzcuaro on the west-central Mexican Plateau and at Chalco in the basin of Mexico*1

    NASA Astrophysics Data System (ADS)

    Watts, W. A.; Bradbury, J. Platt

    1982-01-01

    A 1520-cm sediment core from Lake Patzcuaro, Michoacan, Mexico, is 44,000 yr old at the base. All parts of the core have abundant pollen of Pinus (pine), Alnus (alder), and Quercus (oak) with frequent Abies (fir). The interval dated from 44,000 to 11,000 yr ago has a homogeneous flora characterized by abundant Juniperus (juniper) pollen and frequent Artemisia (sagebrush). It is believed to represent an appreciably drier and colder climate than at present. The Holocene at Lake Patzcuaro is characterized by a moderate increase in Pinus pollen and the loss of Juniperus pollen, as the modern type of climate succeeded. Alnus was abundant until about 5000 yr ago; its abrupt decrease with the first appearance of herbaceous weed pollen may reflect the cutting of lake-shore and stream-course alder communities for agricultural purposes, or it may simply reflect a drying tendency in the climate. Pollen of Zea (corn) appears at Lake Patzcuaro along with low peaks of chenopod and grass pollen at 3500 yr B.P. apparently recording a human population large enough to modify the natural environment, as well as the beginning of agriculture. A rich aquatic flora in this phase suggests eutrophication of the lake by slope erosion. In the most recent period corn is absent from the sediments, perhaps reflecting a change in agricultural practices. The environment changes at Lake Patzcuaro are similar to and correlate with those in the Cuenca de Mexico, where diatom stratigraphy from the Chalco basin indicates fluctuations in lake levels and lake chemistry in response to variations in available moisture. Before 10,000 yr ago climates there were cool and dry, and the Chalco basin was occupied by a shallow freshwater marsh that drained north to Lake Texcoco, where saline water accumulated by evaporation. Increases in effective moisture and possible melting of glaciers during the Holocene caused lake levels to rise throughout the Cuenca de Mexico, and Lake Texcoco flooded the Chalco basin with

  19. Sanctuaries for lake trout in the Great Lakes

    USGS Publications Warehouse

    Stanley, Jon G.; Eshenroder, Randy L.; Hartman, Wilbur L.

    1987-01-01

    Populations of lake trout, severely depleted in Lake Superior and virtually extirpated from the other Great Lakes because of sea lamprey predation and intense fishing, are now maintained by annual plantings of hatchery-reared fish in Lakes Michigan, Huron, and Ontario and parts of Lake Superior. The extensive coastal areas of the Great Lakes and proximity to large populations resulted in fishing pressure on planted lake trout heavy enough to push annual mortality associated with sport and commercial fisheries well above the critical level needed to reestablish self-sustaining stocks. The interagency, international program for rehabilitating lake trout includes controlling sea lamprey abundance, stocking hatchery-reared lake trout, managing the catch, and establishing sanctuaries where harvest is prohibited. Three lake trout sanctuaries have been established in Lake Michigan: the Fox Island Sanctuary of 121, 500 ha, in the Chippewa-Ottawa Treaty fishing zone in the northern region of the lake; the Milwaukee Reef Sanctuary of 160, 000 ha in midlake, in boundary waters of Michigan and Wisconsin; and Julian's Reef Sanctuary of 6, 500 ha, in Illinois waters. In northern Lake Huron, Drummond Island Sanctuary of 55, 000 ha is two thirds in Indian treaty-ceded waters in Michigan and one third in Ontario waters of Canada. A second sanctuary, Six Fathom Bank-Yankee Reef Sanctuary, in central Lake Huron contains 168, 000 ha. Sanctuary status for the Canadian areas remains to be approved by the Provincial government. In Lake Superior, sanctuaries protect the spawning grounds of Gull Island Shoal (70, 000 ha) and Devils Island Shoal (44, 000 ha) in Wisconsin's Apostle Island area. These seven sanctuaries, established by the several States and agreed upon by the States, Indian tribes, the U.S. Department of the Interior, and the Province of Ontario, contribute toward solving an interjurisdictional fishery problem.

  20. Water budgets, water quality, and analysis of nutrient loading of the Winter Park chain of lakes, central Florida, 1989-92

    USGS Publications Warehouse

    Phelps, G.G.; German, E.R.

    1995-01-01

    The Winter Park chain of lakes (Lakes Maitland, Virginia, Osceola, and Mizell) has a combined area of about 900 acres, an immediate drainage area of about 3,100 acres, and mean depths ranging from 11 to 15 feet. The lakes are an important recreational resource for the surrounding communities, but there is concern about the possible effects of stormwater runoff and seepage of nutrient-enriched ground water on the quality of water in the lakes. The lakes receive water from several sources: rainfall on lake surfaces, inflow from other surface-water bodies, stormflow that enters the lakes through storm drains or by direct runoff from land adjacent to the lakes and ground-water seepage. Water leaves the lakes by evaporation, surface outflow, and ground-water outflow. Of the three, only surface outflow can be measured directly. Rainfall, surface inflow and outflow, and lake-stage data were collected from October 1, 1989, to September 30, 1992. Stormflow, evaporation and ground-water inflow and outflow were estimated for the 3 years of the study. Ground-water outflow was calculated by evaluating the rate of lake-stage decline during dry periods. Estimated ground-water outflow was compared to downward leakage rates estimated by ground-water flow models. Lateral ground-water inflow from surficial sediments was calculated as the residual of the flow budget. Flow budgets were calculated for the 3 years of the study. In water year 1992 (a year with about average rainfall), inflow consisted of rainfall, 48 inches; stormflow, 15 inches; surface inflow, 67 inches; and ground water, 40 inches. The calculated outflows were evaporation, 47 inches; surface outflow, 90 inches; and ground water, 33 inches. Water-quality data also were used to calculate nutrient budgets for the lakes. Bimonthly water samples were collected from the lakes and at surface inflow and outflow sites, and were analyzed for physical characteristics, dissolved oxygen, pH, specific conductance, major ions, the

  1. Effects of Surficial Geology, Lakes and Swamps, and Annual Water Availability on Low Flows of Streams in Central New England, and Their Use of Low-Flow Estimation

    USGS Publications Warehouse

    Wandle, S. William; Randall, Allan D.

    1994-01-01

    Equations developed by multiple-regression analysis of data from 49 drainage basins in Massachusetts, New Hampshire, Rhode Island, Vermont, and southwestern Maine indicate that low flow of streams in this region is largely a function of the amount of water available to the basin and the extent of surficial sand and gravel relative to the extent of till and fine-grained stratified drift. Low flow per square mile from areas of surficial sand and gravel is consistently much greater than that from areas of till and bedrock, but flood plains and alluvial fans seem to contribute less low flow per square mile than do other types of surficial sand and gravel. The areal extent of lakes and swamps also correlates negatively with low flow in multiple-regression equations, presumably because intense evapotranspiration from these localities consumes water that would otherwise become streamflow. The annual minimum 7-day mean low flows that occur during summer and fall at 2-year and 10-year recurrence intervals (7Q2 and 7QIO) were selected as indices of low flow and were adjusted to a common base period, 1942-71. Central New England was divided into a region of high relief that com- prises much of New Hampshire, Vermont, and western Massachusetts, and a region of low relief that generally lies to the east and south but also includes the Lake Champlain lowland of Vermont. In the high-relief region, mean basin elevation proved to be the most significant index of the amount of water available. In the low-relief region, mean annual runoff per square mile was more significant than elevation, particularly when multiplied by the areal extent of sand and gravel and that of till. Dividing the areal extent of sand and gravel by stream length improved the fit of regression equations for the low-relief region. Regression equations were developed that explained at least 95 percent of the variation in 7QIO within both the high-relief and the low-relief data sets. Equations proposed for

  2. Evolution of Late Miocene to Contemporary Displacement Transfer Between the Northern Furnace Creek and Southern Fish Lake Valley Fault Zones and the Central Walker Lane, Western Great Basin, Nevada

    NASA Astrophysics Data System (ADS)

    Oldow, J. S.; Geissman, J. W.

    2013-12-01

    Late Miocene to contemporary displacement transfer from the north Furnace Creek (FCF) and southern Fish Lake Valley (FLVF) faults to structures in the central Walker Lane was and continues to be accommodated by a belt of WNW-striking left-oblique fault zones in the northern part of the southern Walker Lane. The WNW fault zones are 2-9 km wide belts of anastomosing fault strands that intersect the NNW-striking FCF and southern FLVF in northern Death Valley and southern Fish Lake Valley, respectively. The WNW fault zones extend east for over 60 km where they merge with a 5-10 km wide belt of N10W striking faults that marks the eastern boundary of the southern Walker Lane. Left-oblique displacement on WNW faults progressively decreases to the east, as motion is successively transferred northeast on NNE-striking faults. NNE faults localize and internally deform extensional basins that each record cumulative net vertical displacements of between 3.0 and 5.2 km. The transcurrent faults and associated basins decrease in age from south to north. In the south, the WNW Sylvania Mountain fault system initiated left-oblique motion after 7 Ma but does not have evidence of contemporary displacement. Farther north, the left-oblique motion on the Palmetto Mountain fault system initiated after 6.0 to 4.0 Ma and has well-developed scarps in Quaternary deposits. Cumulative left-lateral displacement for the Sylvania Mountain fault system is 10-15 km, and is 8-12 km for the Palmetto fault system. The NNE-striking faults that emanate from the left-oblique faults merge with NNW transcurrent faults farther north in the eastern part of the Mina deflection, which links the Owens Valley fault of eastern California to the central Walker Lane. Left-oblique displacement on the Sylvania Mountain and Palmetto Mountain fault zones deformed the Furnace Creek and Fish Lake Valley faults. Left-oblique motion on Sylvania Mountain fault deflected the FCF into the 15 km wide Cucomungo Canyon restraining

  3. Lake Ilopango, El Salvador

    NASA Image and Video Library

    2015-03-10

    Lake Ilopango is a crater lake which fills a volcanic caldera in central El Salvador, immediately east of the capital city San Salvador. The caldera collapsed most recently in about 500 AD, producing 20 times as much ash as the Mount St. Helens eruption, and blanketing an area of at least 10,000 square kilometers waist-deep in ash. The only historical eruption occurred in 1879, forming lava domes, now islets in the lake. Quetzaltepec is the stratovolcano just west of the city. Its last eruption in 1917 produced lavas flowing down the northwest flank, and evaporated the crater lake. The image was acquired March 5, 2006, covers an area of 27 by 42 km, and is located at 13.7 degrees north, 89.1 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA19237

  4. Survival of lake trout eggs and fry reared in water from the upper Great Lakes

    USGS Publications Warehouse

    Mac, Michael J.; Edsall, Carol Cotant; Seelye, James G.

    1985-01-01

    As part of continuing studies of the reproductive failure of lake trout (Salvelinus namaycush) in Lake Michigan, we measured the survival of lake trout eggs and fry of different origins and reared in different environments. Eggs and milt were stripped from spawning lake trout collected in the fall of 1980 from southeastern Lake Michigan, northwestern Lake Huron, south central Lake Superior, and from hatchery brood stock. Eggs from all sources were incubated, and the newly hatched fry were reared for 139 days in lake water from each of the three upper Great Lakes and in well water. Survival of eggs to hatching at all sites was lowest for those from Lake Michigan (70% of fertilized eggs) and highest for eggs from Lake Superior (96%). Comparisons of incubation water from the different lakes indicated that hatching success of eggs from all sources was