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Sample records for lake tanganyika vertical

  1. Seismicity of southern Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Lavayssiere, A.; Gallacher, R. J.; Keir, D.; Ebinger, C. J.; Drooff, C.; Khalfan, M.; Bull, J. M.

    2015-12-01

    Global seismic networks document frequent and unusually deep earthquakes in East African rift sectors lacking central volcanoes. The deep seismicity means that we can use earthquakes to probe the geometry and kinematics of fault systems throughout the crust, and to understand the distribution of strain between large offset border fault systems and intrabasinal faults. The southern Tanganyika rift zone has the highest seismicity rate within East Africa during the period 1973-present, yet earlier temporary seismometer networks have been too sparse in space and time to relocate earthquakes with location and depth errors of < 5-10 km. We address this issue by recording seismicity of southern Lake Tanganyika since June 2014 using a network at 12 broadband seismic stations. The distribution of earthquakes shows that deformation primarily occurs on large offset border faults beneath the lake. Subsidiary earthquake activity occurs along the subparrallel Rukwa graben, and beneath the NE-SW striking Mweru rift. The distribution of earthquakes suggests the southern end of lake Tanganyika is characterized by a network of intersecting NNW and NE striking faults. The depths of earthquakes are distributed throughout the crust, consistent with the relatively strong lithosphere.

  2. Vertical stability and the Brunt-Väisäla frequency of deep natural waters by the example of Lake Baikal, Lake Tanganyika, and the World Ocean

    NASA Astrophysics Data System (ADS)

    Sherstyankin, P. P.; Kuimova, L. N.

    2009-12-01

    Theoretical analysis, calculations, and comparison with the results of observations in Lake Baikal, Lake Tanganyika, and the World Ocean are performed for the vertical stability E and the Brunt-Väisäla frequency N in the form of N 2 with regard to all components (at the constant temperature T and the salinity S, the common adiabatic form at T, S Const). The adiabatic stability E ad and the Väisäla frequency N in the form of N {/ad 2} are always positive; at a change from the inverse to the direct temperature stratification, they have deep minimums reaching 10-16 m-1 and 10-15 s-2 and less; the minimums have the form of a special point, a reversal point of the first kind called a “cusp.” The reality of these reversal points is confirmed by the analysis of the investigation procedure, comparison with the results of previous theoretical (Sherstyankin, et al., 2007), and experimental (observations in Baikal, Shimaraev et al., 1994) works. The features of vertical profiles of E ad , E and N {/ad 2}, N 2, as well as the layers where the Brunt-Väisäla frequency is less than the inertial frequency, are studied. The analysis with regard to all components of the stability E ad and the Brunt-Väisäla frequency N makes a great contribution to understanding of mixing processes in theoretical and experimental investigations; it is valid in all reservoirs of the Earth with inverse and direct temperature stratification, including Lake Baikal, Lake Tanganyika, and the World Ocean.

  3. Tempo and mode of diversification of lake Tanganyika cichlid fishes.

    PubMed

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

    2008-03-05

    Understanding the causes of disparities in species diversity across taxonomic groups and regions is a fundamental aim in evolutionary biology. Addressing these questions is difficult because of the need for densely sampled phylogenies and suitable empirical systems. Here we investigate the cichlid fish radiation of Lake Tanganyika and show that per lineage diversification rates have been more than six times slower than in the species flocks of Lakes Victoria and Malawi. The result holds even at peak periods of diversification in Lake Tanganyika, ruling out the age of the lake as an explanation for slow average rates, and is robust to uncertainties over the calibration of cichlid radiations in geological time. Moreover, Lake Tanganyika lineages, irrespective of different biological characteristics (e.g. sexually dichromatic versus sexually monochromatic clades), have diversified at similar rates, falling within typical estimates across a range of plant and animal clades. For example, the mostly sexually dichromatic haplochromines, which have speciated explosively in Lakes Victoria and Malawi, have displayed modest rates in Lake Tanganyika (where they are called Tropheini). Our results show that either the Lake Tanganyika environment is less conducive for cichlid speciation or the remarkable diversifying abilities of the haplochromines were inhibited by the prior occupancy of older radiations. Although the results indicate a dominant role for the environment in shaping cichlid diversification, differences in the timing of diversification among the Tanganyikan tribes indicate that biological differences were still important for the dynamics of species build-up in the lake. While we cannot resolve the timing of the radiation relative to the origin of the lake, because of the lack of robust geological date calibrations for cichlids, our results are consistent with a scenario that the different clades reflect independent adaptive radiations into different broad niches in

  4. Tempo and Mode of Diversification of Lake Tanganyika Cichlid Fishes

    PubMed Central

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

    2008-01-01

    Background Understanding the causes of disparities in species diversity across taxonomic groups and regions is a fundamental aim in evolutionary biology. Addressing these questions is difficult because of the need for densely sampled phylogenies and suitable empirical systems. Methodology/Principal Findings Here we investigate the cichlid fish radiation of Lake Tanganyika and show that per lineage diversification rates have been more than six times slower than in the species flocks of Lakes Victoria and Malawi. The result holds even at peak periods of diversification in Lake Tanganyika, ruling out the age of the lake as an explanation for slow average rates, and is robust to uncertainties over the calibration of cichlid radiations in geological time. Moreover, Lake Tanganyika lineages, irrespective of different biological characteristics (e.g. sexually dichromatic versus sexually monochromatic clades), have diversified at similar rates, falling within typical estimates across a range of plant and animal clades. For example, the mostly sexually dichromatic haplochromines, which have speciated explosively in Lakes Victoria and Malawi, have displayed modest rates in Lake Tanganyika (where they are called Tropheini). Conclusion/Significance Our results show that either the Lake Tanganyika environment is less conducive for cichlid speciation or the remarkable diversifying abilities of the haplochromines were inhibited by the prior occupancy of older radiations. Although the results indicate a dominant role for the environment in shaping cichlid diversification, differences in the timing of diversification among the Tanganyikan tribes indicate that biological differences were still important for the dynamics of species build-up in the lake. While we cannot resolve the timing of the radiation relative to the origin of the lake, because of the lack of robust geological date calibrations for cichlids, our results are consistent with a scenario that the different clades

  5. Mating and Parental Care in Lake Tanganyika's Cichlids

    PubMed Central

    Sefc, Kristina M.

    2011-01-01

    Cichlid fishes of Lake Tanganyika display a variety of mating and parental care behaviors, including polygamous and monogamous mouthbrooding and substrate breeding, cooperative breeding, as well as various alternative reproductive tactics such as sneaking and piracy. Moreover, reproductive behaviors sometimes vary within species both in space and in time. Here, I survey reports on mating and parenting behaviors of Lake Tanganyika cichlid species and address the evolution of mating and parental care patterns and sexual dimorphism. Notes on measures of sexual selection intensity and the difficulties of defining mating systems and estimating selection intensities at species level conclude the essay. PMID:21822482

  6. Mating and Parental Care in Lake Tanganyika's Cichlids.

    PubMed

    Sefc, Kristina M

    2011-01-01

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

  7. Multi-year wind dynamics around Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Docquier, D.; Thiery, W.; Lhermitte, S.; van Lipzig, N.

    2016-11-01

    Lake Tanganyika is the second largest freshwater lake in the world by volume and is of prime importance for the regional economy in East Africa. Although the lake is recognized as a key component of the regional climate system, little is known about atmospheric dynamics in its surroundings. To understand this role, we analyze winds around Lake Tanganyika as modeled by a high resolution (7 km) regional climate model (Consortium for Small-scale Modeling in Climate Mode) over the period 1999-2008. Modeled surface wind speed and direction are in very good agreement with high resolution (12.5 km) Quick Scatterometer (QuikSCAT) satellite wind observations during the dry season. Comparison of a control run with a model simulation where all lake pixels are replaced by representative land pixels indicates that mean surface wind speed over Lake Tanganyika almost doubles due to lake presence. Furthermore, a region of higher surface wind speed in the central part of the lake is identified and confirmed by QuikSCAT observations. A combination of wind channeling along valley mountains and wind confluence on the upwind side of the lake is responsible for this speed-up. The lower wind speeds in the rest of the lake result from blocked conditions due to more pronounced orography. Finally, the model captures a zone of higher wind speed at around 2 km height, associated with the low-level Somali jet. These results demonstrate that high resolution climate modeling allows a detailed understanding of wind dynamics in the vicinity of Lake Tanganyika.

  8. What prevents outgassing of methane to the atmosphere in Lake Tanganyika?

    NASA Astrophysics Data System (ADS)

    Durisch-Kaiser, Edith; Schmid, Martin; Peeters, Frank; Kipfer, Rolf; Dinkel, Christian; Diem, Torsten; Schubert, Carsten J.; Wehrli, Bernhard

    2011-06-01

    Tropical East African Lake Tanganyika hosts the Earth's largest anoxic freshwater body. The entire water column holds over 23 Tg of the potent greenhouse gas methane (CH4). Methane is formed under sulphate-poor conditions via carbon dioxide reduction or fermentation from detritus and relict sediment organic matter. Permanent density stratification supports an accumulation of CH4 below the permanent oxycline. Despite CH4 significance for global climate, anaerobic microbial consumption of CH4 in freshwater is poorly understood. Here we provide evidence for intense methanotrophic activity not only in the oxic but also in the anoxic part of the water column of Lake Tanganyika. We measured CH4, 13C of dissolved CH4, dissolved oxygen (O2), sulphate (SO42-), sulphide (HS-) and the transient tracers chlorofluorocarbon-12 (CFC-12) and tritium (3H). A basic one-dimensional model, which considers vertical transport and biogeochemical fluxes and transformations, was used to interpret the vertical distribution of these substances. The results suggest that the anaerobic oxidation of CH4 is an important mechanism limiting CH4 to the anoxic zone of Lake Tanganyika. The important role of the anaerobic oxidation for CH4 concentrations is further supported by high abundances (up to ˜33% of total DAPI-stained cells) of single living archaea, identified by fluorescence in situ hybridization.

  9. Fishing with bed nets on Lake Tanganyika: a randomized survey.

    PubMed

    McLean, Kate A; Byanaku, Aisha; Kubikonse, Augustine; Tshowe, Vincent; Katensi, Said; Lehman, Amy G

    2014-10-07

    Malaria is among the most common causes of death along Lake Tanganyika, a problem which many aid organizations have attempted to combat through the distribution of free mosquito bed nets to high-risk communities. The Lake Tanganyika Floating Health Clinic (LTFHC), a health-based non-governmental organization (NGO), has observed residents of the Lake Tanganyika basin using bed nets to fish small fry near the shoreline, despite a series of laws that prohibit bed net use and other fine-gauge nets for fishing, implemented to protect the near-shore fish ecology. The LTFHC sought to quantify the sources of bed nets and whether they were being used for fishing. The LTFHC conducted a survey of seven lakeside villages in Lagosa Ward, Tanzania. The government has divided each village into two to six pre-existing geographic sub-villages depending on population size. Seven households per sub-village were chosen at random for survey administration. The survey consisted of 23 questions regarding mosquito bed net practices, including the use of bed nets for fishing, as well as questions pertaining to any perceived changes to the fish supply. A total of 196 surveys were administered over a four-week period with a 100% response rate. Over 87% of households surveyed have used a mosquito bed net for fishing at some point. The majority of respondents reported receiving their bed net for free (96.4%), observing "many" residents of their village using bed nets for fishing (97.4%), and noticing a subjective decrease in the fish supply over time (64.9%). The findings of this study raise concerns that the use of free malaria bed nets for fishing is widespread along Lake Tanganyika, and that this dynamic will have an adverse effect on fish ecology. Further studies are indicated to fully define the scope of bed net misuse and the effects of alternative vector control strategies in water-based communities.

  10. Complete mitochondrial DNA replacement in a Lake Tanganyika cichlid fish.

    PubMed

    Nevado, B; Koblmüller, S; Sturmbauer, C; Snoeks, J; Usano-Alemany, J; Verheyen, E

    2009-10-01

    We used nuclear and mitochondrial DNA (mtDNA) sequences from specimens collected throughout Lake Tanganyika to clarify the evolutionary relationship between Lamprologus callipterus and Neolamprologus fasciatus. The nuclear data support the reciprocal monophyly of these two shell-breeding lamprologine cichlids. However, mtDNA sequences show that (i) L. callipterus includes two divergent and geographically disjunct (North-South) mtDNA lineages; and that (ii) N. fasciatus individuals cluster in a lineage sister group to the northern lineage of L. callipterus. The two mtDNA lineages of L. callipterus diverged c. 684 kya to 1.2 Ma, coinciding with a major water level low stand in Lake Tanganyika, which divided the lake into isolated sub-lakes. This suggests that the two mtDNA lineages originated as the result of the separation of L. callipterus populations in different sub-basins. The incongruent phylogenetic position of N. fasciatus can best be explained by an ancient unidirectional introgression from L. callipterus into N. fasciatus. Remarkably, our data indicate that this event resulted in the complete mtDNA replacement in N. fasciatus. Our data suggest that hybridization occurred soon after the divergence of the two L. callipterus mtDNA lineages, probably still during the water level low stand, and that subsequently the invading mtDNA lineage spread throughout the lake.

  11. Anaerobic ammonium oxidation in a tropical freshwater system (Lake Tanganyika).

    PubMed

    Schubert, Carsten J; Durisch-Kaiser, Edith; Wehrli, Bernhard; Thamdrup, Bo; Lam, Phyllis; Kuypers, Marcel M M

    2006-10-01

    Here we provide the first direct evidence for the anammox process (anaerobic ammonium oxidation) in a lacustrine system, Lake Tanganyika, the second largest lake in the world. Incubations with (15)N labelled nitrate showed that anammox occurred in the suboxic water layer at 100-110 m water depth. Anammox rates up to 10 nM N(2) h(-1) are comparable to those reported for the marine water column. Up to approximately 13% of produced N(2) could be attributed to the anammox process whereas the remainder was related to denitrification. Typical lipid biomarkers characteristic of anammox bacteria were found in filtered water from the depths where anammox occurred, thus supporting the presence of anammox bacteria. Further evidence is provided by fluorescence in situ hybridization (FISH), revealing up to 13 000 anammox bacteria cells per ml or 1.4% of all DAPI (4'-6-Diamidino-2-phenylindole)-stained cells. Phylogenetic analyses of partial 16S rRNA genes indicated the presence of sequences most closely related to the known anammox bacterium Candidatus "Scalindua brodae" (95.7% similarity). Using the incubation results, a total loss of 0.2 Tg N(2) per year linked to anammox was estimated for the Northern basin of Lake Tanganyika.

  12. Hydrothermal vents in Lake Tanganyika, East African, Rift system

    NASA Astrophysics Data System (ADS)

    Tiercelin, Jean-Jacques; Pflumio, Catherine; Castrec, Maryse; Boulégue, Jacques; Gente, Pascal; Rolet, Joël; Coussement, Christophe; Stetter, Karl O.; Huber, Robert; Buku, Sony; Mifundu, Wafula

    1993-06-01

    Sublacustrine hydrothermal vents with associated massive sulfides were discovered during April 1987 at Pemba and Cape Banza on the Zaire side of the northern basin of Lake Tanganyika, East African Rift system. New investigations by a team of ten scuba divers during the multinational (France, Zaire, Germany, and Burundi) TANGANYDRO expedition (August-October 1991) found hydrothermal vents down to a depth of 46 m along north-trending active faults bounding the Tanganyika rift on the western side. Temperatures from 53 to 103 °C were measured in hydrothermal fluids and sediments. Veins of massive sulfides 1-10 cm thick (pyrite and marcasite banding) were found associated with vents at the Pemba site. At Cape Banza,active vents are characterized by 1-70-cm-high aragonite chimneys, and there are microcrystalline pyrite coatings on the walls of hydrothermal pipes. Hydrothermal fluid end members show distinctive compositions at the two sites. The Pemba end member is a NaHCO3-enriched fluid similar to the NaHCO3 thermal fluids from lakes Magadi and Bogoria in the eastern branch off the rift. The Cape Banza end member is a solution enriched in NaCl. Such brines may have a deep-seated basement origin, as do the Uvinza NaCl brines on the eastern flank of the Tanganyika basin. Geothermometric calculations have yielded temperatures of fluid-rock interaction off 219 and 179 °C in the Pemba and Cape Banza systems, respectively. Abundant white or reddish-brown microbial colonies resembling Beggiatoa mats were found surrounding the active vents. Thermal fluid circulation is permitted by opening of cracks related to 130 °N normal-dextral faults that intersect the north- south major rift trend. The source of heat for such hydrothermal systems may relate to the existence of magmatic bodies under the rift, which is suggested by the isotopic composition of carbon dioxide released at Pemba and Cape Banza.

  13. The adaptive radiation of cichlid fish in lake tanganyika: a morphological perspective.

    PubMed

    Takahashi, Tetsumi; Koblmüller, Stephan

    2011-01-01

    Lake Tanganyika is the oldest of the Great Ancient Lakes in the East Africa. This lake harbours about 250 species of cichlid fish, which are highly diverse in terms of morphology, behaviour, and ecology. Lake Tanganyika's cichlid diversity has evolved through explosive speciation and is treated as a textbook example of adaptive radiation, the rapid differentiation of a single ancestor into an array of species that differ in traits used to exploit their environments and resources. To elucidate the processes and mechanisms underlying the rapid speciation and adaptive radiation of Lake Tanganyika's cichlid species assemblage it is important to integrate evidence from several lines of research. Great efforts have been, are, and certainly will be taken to solve the mystery of how so many cichlid species evolved in so little time. In the present review, we summarize morphological studies that relate to the adaptive radiation of Lake Tanganyika's cichlids and highlight their importance for understanding the process of adaptive radiation.

  14. The Adaptive Radiation of Cichlid Fish in Lake Tanganyika: A Morphological Perspective

    PubMed Central

    Takahashi, Tetsumi; Koblmüller, Stephan

    2011-01-01

    Lake Tanganyika is the oldest of the Great Ancient Lakes in the East Africa. This lake harbours about 250 species of cichlid fish, which are highly diverse in terms of morphology, behaviour, and ecology. Lake Tanganyika's cichlid diversity has evolved through explosive speciation and is treated as a textbook example of adaptive radiation, the rapid differentiation of a single ancestor into an array of species that differ in traits used to exploit their environments and resources. To elucidate the processes and mechanisms underlying the rapid speciation and adaptive radiation of Lake Tanganyika's cichlid species assemblage it is important to integrate evidence from several lines of research. Great efforts have been, are, and certainly will be taken to solve the mystery of how so many cichlid species evolved in so little time. In the present review, we summarize morphological studies that relate to the adaptive radiation of Lake Tanganyika's cichlids and highlight their importance for understanding the process of adaptive radiation. PMID:21716857

  15. Lake Tanganyika--a 'melting pot' of ancient and young cichlid lineages (Teleostei: Cichlidae)?

    PubMed

    Weiss, Juliane D; Cotterill, Fenton P D; Schliewen, Ulrich K

    2015-01-01

    A long history of research focused on the East Africa cichlid radiations (EAR) revealed discrepancies between mtDNA and nuclear phylogenies, suggesting that interspecific hybridisation may have been significant during the radiation of these fishes. The approximately 250 cichlid species of Lake Tanganyika have their roots in a monophyletic African cichlid assemblage, but controversies remain about the precise phylogenetic origin and placement of different lineages and consequently about L. Tanganyika colonization scenarios. 3312 AFLP loci and the mitochondrial ND2 gene were genotyped for 91 species representing almost all major lacustrine and riverine haplotilapiine east African cichlid lineages with a focus on L. Tanganyika endemics. Explicitly testing for the possibility of ancient hybridisation events, a comprehensive phylogenetic network hypothesis is proposed for the origin and diversification of L. Tanganyika cichlids. Inference of discordant phylogenetic signal strongly suggests that the genomes of two endemic L. Tanganyika tribes, Eretmodini and Tropheini, are composed of an ancient mixture of riverine and lacustrine lineages. For the first time a strong monophyly signal of all non-haplochromine mouthbrooding species endemic to L. Tanganyika ("ancient mouthbrooders") was detected. Further, in the genomes of early diverging L. Tanganyika endemics Trematocarini, Bathybatini, Hemibatini and Boulengerochromis genetic components of other lineages belonging to the East African Radiation appear to be present. In combination with recent palaeo-geological results showing that tectonic activity in the L. Tanganyika region resulted in highly dynamic and heterogeneous landscape evolution over the Neogene and Pleistocene, the novel phylogenetic data render a single lacustrine basin as the geographical cradle of the endemic L. Tanganyika cichlid lineages unlikely. Instead a scenario of a pre-rift origin of several independent L. Tanganyika precursor lineages which

  16. Evolution of brain-body allometry in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Kotrschal, Alexander; Hayward, Alexander; Buechel, Severine Denise; Zidar, Josefina; Løvlie, Hanne; Kolm, Niclas

    2016-07-01

    Brain size is strongly associated with body size in all vertebrates. This relationship has been hypothesized to be an important constraint on adaptive brain size evolution. The essential assumption behind this idea is that static (i.e., within species) brain-body allometry has low ability to evolve. However, recent studies have reported mixed support for this view. Here, we examine brain-body static allometry in Lake Tanganyika cichlids using a phylogenetic comparative framework. We found considerable variation in the static allometric intercept, which explained the majority of variation in absolute and relative brain size. In contrast, the slope of the brain-body static allometry had relatively low variation, which explained less variation in absolute and relative brain size compared to the intercept and body size. Further examination of the tempo and mode of evolution of static allometric parameters confirmed these observations. Moreover, the estimated evolutionary parameters indicate that the limited observed variation in the static allometric slope could be a result of strong stabilizing selection. Overall, our findings suggest that the brain-body static allometric slope may represent an evolutionary constraint in Lake Tanganyika cichlids. © 2016 The Author(s).

  17. A late Holocene paleoclimatic history of Lake Tanganyika, East Africa

    NASA Astrophysics Data System (ADS)

    Stager, J. Curt; Cocquyt, Christine; Bonnefille, Raymonde; Weyhenmeyer, Constanze; Bowerman, Nicole

    2009-07-01

    A nearshore core (LT03-05) from the north basin of Lake Tanganyika provides diatom, pollen, and sedimentary time series covering the last ca. 3800 yr at 15-36 yr resolution. A chronology supported by 21 AMS dates on terrestrial and lacustrine materials allows us to account for ancient carbon effects on 14C ages and to propose refinements of the region's climatic history. Conditions drier than those of today were followed after ca. 3.30 ka by an overall wetting trend. Several century-scale climate variations were superimposed upon that trend, with exceptionally rainy conditions occurring 1.70-1.40 ka, 1.15-0.90 ka, 0.70-0.55 ka, and 0.35-0.20 ka. Around 0.55-0.35 ka, during the Spörer sunspot minimum, drier conditions developed in the northern Tanganyika basin while more humid conditions were registered at Lakes Victoria and Naivasha. This indicates significant variability in the nature and distribution of near-equatorial rainfall anomalies during much of the Little Ice Age.

  18. Recent paleorecords document rising mercury contamination in Lake Tanganyika

    USGS Publications Warehouse

    Conaway, C.H.; Swarzenski, P.W.; Cohen, A.S.

    2012-01-01

    Recent Lake Tanganyika Hg deposition records were derived using 14C and excess 210Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake's shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23??0.2ng/g, increasing to 74ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2??g/m 2/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20??3ng/g, increasing to 46ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70??g/m 2/a at this site, representing a 2-3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition. ?? 2011.

  19. Manganese content records seasonal upwelling in Lake Tanganyika mussels

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Three shells present very similar Mn/Ca profiles dominated by a peak that matched the concomitant increase of Mn and chlorophyll a in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal changes in water composition. We postulate that Mn/Ca in shells record the conjunction of an increase of biological activity with supplied of dissolved Mn and nutriments in coastal waters, resulting in an enhanced assimilation of biogenic Mn-rich particles. By combining the most recent generation of laser ablation system and the powerful High Resolution ICP-MS, the spatial resolution could be improved down to 5 to 10 µm crater size and end up in a better constrain of the relative variations of the annual Mn peaks. Such an approach on P. spekii from Lake Tanganyika has definitively a great potential to provide recent and past records on primary productivity associated with the monsoon climate system.

  20. Hydrothermal vents is Lake Tanganyika, East African Rift system

    SciTech Connect

    Tiercelin, J.J.; Pflumio, C.; Castrec, M.

    1993-06-01

    Sublacustrine hydrothermal vents with associated massive sulfides were discovered during April 1987 at Pemba and Cape Banza on the Zaire side of the northern basin of Lake Tanganyika, East African Rift system. New investigations by a team of ten scuba divers during the multinational (France, Zaire, Germany, and Burundi) TANGANYDRO expedition (August-October 1991) found hydrothermal vents down to a depth of 46 m along north-trending active faults bounding the Tanganyika rift on the western side. Temperatures from 53 to 103 {degrees}C were measured in hydrothermal fluids and sediments. Veins of massive sulfides 1-10 cm thick (pyrite and marcasite banding) were found associated with vents at the Pemba site. At Cape Banza, active vents are characterized by 1-70-cm-high aragonite chimneys, and there are microcrystalline pyrite coatings on the walls of hydrothermal pipes. Hydrothermal fluid end members show distinctive compositions at the two sites. The Pemba end member is a NaHCO{sub 3}-enriched fluid similar to the NaHCO{sub 3} thermal fluids form lakes Magadi and Bogoria in the eastern branch of the rift. The Cape Banza end member is a solution enriched in NaCl. Such brines may have a deep-seated basement origin, as do the Uvinza NaCl brines on the eastern flank of the Tanganyika basin. Geothermometric calculations have yielded temperatures of fluid-rock interaction of 219 and 179 {degrees}C in the Pemba and Cape Banza systems, respectively. Abundant white or reddish-brown microbial colonies resembling Beggiatoa mats were found surrounding the active vents. Thermal fluid circulation is permitted by opening of cracks related to 130{degrees}N normal-dextral faults that intersect the north-south major rift trend. The sources of heat for such hydrothermal systems may relate to the existence of magmatic bodies under the rift, which is suggested by the isotopic composition of carbon dioxide released at Pemba and Cape Banza. 21 refs., 2 figs.

  1. Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa

    NASA Astrophysics Data System (ADS)

    O'Reilly, Catherine M.; Alin, Simone R.; Plisnier, Pierre-Denis; Cohen, Andrew S.; McKee, Brent A.

    2003-08-01

    Although the effects of climate warming on the chemical and physical properties of lakes have been documented, biotic and ecosystem-scale responses to climate change have been only estimated or predicted by manipulations and models. Here we present evidence that climate warming is diminishing productivity in Lake Tanganyika, East Africa. This lake has historically supported a highly productive pelagic fishery that currently provides 25-40% of the animal protein supply for the populations of the surrounding countries. In parallel with regional warming patterns since the beginning of the twentieth century, a rise in surface-water temperature has increased the stability of the water column. A regional decrease in wind velocity has contributed to reduced mixing, decreasing deep-water nutrient upwelling and entrainment into surface waters. Carbon isotope records in sediment cores suggest that primary productivity may have decreased by about 20%, implying a roughly 30% decrease in fish yields. Our study provides evidence that the impact of regional effects of global climate change on aquatic ecosystem functions and services can be larger than that of local anthropogenic activity or overfishing.

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

    PubMed

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

    2004-03-07

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

  3. Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500

    NASA Astrophysics Data System (ADS)

    Tierney, Jessica E.; Mayes, Marc T.; Meyer, Natacha; Johnson, Christopher; Swarzenski, Peter W.; Cohen, Andrew S.; Russell, James M.

    2010-06-01

    Instrumental observations suggest that Lake Tanganyika, the largest rift lake in East Africa, has become warmer, increasingly stratified and less productive over the past 90years (refs 1,2). These trends have been attributed to anthropogenic climate change. However, it remains unclear whether the decrease in productivity is linked to the temperature rise, and whether the twentieth-century trends are anomalous within the context of longer-term variability. Here, we use the TEX86 temperature proxy, the weight per cent of biogenic silica and charcoal abundance from Lake Tanganyika sediment cores to reconstruct lake-surface temperature, productivity and regional wildfire frequency, respectively, for the past 1,500years. We detect a negative correlation between lake-surface temperature and primary productivity, and our estimates of fire frequency, and hence humidity, preclude decreased nutrient input through runoff as a cause for observed periods of low productivity. We suggest that, throughout the past 1,500years, rising lake-surface temperatures increased the stratification of the lake water column, preventing nutrient recharge from below and limiting primary productivity. Our records indicate that changes in the temperature of Lake Tanganyika in the past few decades exceed previous natural variability. We conclude that these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery.

  4. Century-Long Warming Trends in the Upper Water Column of Lake Tanganyika.

    PubMed

    Kraemer, Benjamin M; Hook, Simon; Huttula, Timo; Kotilainen, Pekka; O'Reilly, Catherine M; Peltonen, Anu; Plisnier, Pierre-Denis; Sarvala, Jouko; Tamatamah, Rashid; Vadeboncoeur, Yvonne; Wehrli, Bernhard; McIntyre, Peter B

    2015-01-01

    Lake Tanganyika, the deepest and most voluminous lake in Africa, has warmed over the last century in response to climate change. Separate analyses of surface warming rates estimated from in situ instruments, satellites, and a paleolimnological temperature proxy (TEX86) disagree, leaving uncertainty about the thermal sensitivity of Lake Tanganyika to climate change. Here, we use a comprehensive database of in situ temperature data from the top 100 meters of the water column that span the lake's seasonal range and lateral extent to demonstrate that long-term temperature trends in Lake Tanganyika depend strongly on depth, season, and latitude. The observed spatiotemporal variation in surface warming rates accounts for small differences between warming rate estimates from in situ instruments and satellite data. However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements. Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously. Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.

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

    PubMed Central

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

    2008-01-01

    The spectacular marine-like diversity of the endemic fauna of Lake Tanganyika, the oldest of the African Great Lakes, led early researchers to suggest that the lake must have once been connected to the ocean. Recent geophysical reconstructions clearly indicate that Lake Tanganyika formed by rifting in the African subcontinent and was never directly linked to the sea. Although the Lake has a high proportion of specialized endemics, the absence of close relatives outside Tanganyika has complicated phylogeographic reconstructions of the timing of lake colonization and intralacustrine diversification. The freshwater herring of Lake Tanganyika are members of a large group of pellonuline herring found in western and southern Africa, offering one of the best opportunities to trace the evolutionary history of members of Tanganyika's biota. Molecular phylogenetic reconstructions indicate that herring colonized West Africa 25–50MYA, at the end of a major marine incursion in the region. Pellonuline herring subsequently experienced an evolutionary radiation in West Africa, spreading across the continent and reaching East Africa's Lake Tanganyika during its early formation. While Lake Tanganyika has never been directly connected with the sea, the endemic freshwater herring of the lake are the descendents of an ancient marine incursion, a scenario which may also explain the origin of other Tanganyikan endemics. PMID:18431469

  6. Marine incursion: the freshwater herring of Lake Tanganyika are the product of a marine invasion into west Africa.

    PubMed

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

    2008-04-23

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

  7. Estimating the age of formation of lakes: An example from Lake Tanganyika, East African Rift system

    SciTech Connect

    Cohen, A.; Soreghan, M.J.; Scholz, C.A.

    1993-06-01

    Age estimates for ancient lakes are important for determining their histories and their rates of biotic and tectonic evolution. In the absence of dated core material from the lake`s sedimentary basement, several techniques have been used to generate such age estimates. The most common of these, herein called the reflection seismic-radiocarbon method (RSRM), combines estimates of short-term sediment-accumulation rates derived from radiocarbon-dated cores and depth-to-basement estimates derived from reflection-seismic data at or near the same locality to estimate an age to basement. Age estimates form the RSRM suggest that the structural basins of central Lake Tanganyika began to form between 9 and 12 Ma. Estimates for the northern and southern basins are younger (7 to 8 Ma and 2 to 4 Ma, respectively). The diachroneity of estimates for different segments of the lake is equivocal, and may be due to erosional loss of record in the northern and southern structural basins or to progressive opening of the rift. The RSRM age estimates for Lake Tanganyika are considerably younger than most prior estimates and clarify the extensional history of the western branch of the East African Rift system. 31 refs., 3 figs., 1 tab.

  8. Similar morphologies of cichlid fish in Lakes Tanganyika and Malawi are due to convergence.

    PubMed

    Kocher, T D; Conroy, J A; McKaye, K R; Stauffer, J R

    1993-06-01

    The species flocks of cichlid fishes in the lakes of East Africa are the most spectacular example of adaptive radiation among living vertebrates. Similar highly derived morphologies are found among species in different lakes. These similarities have been variously interpreted either as evidence for migration of ancestral species between the lakes, or of striking convergence of morphology. To distinguish among these competing hypotheses we sequenced a portion of the mitochondrial DNA control region from six pairs of morphologically similar taxa from Lakes Malawi and Tanganyika. Our results clearly indicate a separate origin of these morphologies in the two lakes. They also suggest that the Tanganyikan radiation is relatively old, and that the species flocks in lakes Malawi and Victoria are derived from one of the ancient lineages found in Lake Tanganyika. These findings have important implications for understanding the pattern of morphological and behavioral evolution in these fish.

  9. Behavior of rare earth and trace elements in Lake Tanganyika and its three major tributaries

    NASA Astrophysics Data System (ADS)

    Sako, A.; Johnson, R.

    2004-12-01

    Water samples were collected, during the rainy and dry seasons 2003, from three major rivers and several locations of the Lake Tanganyika. They were directly filtered (0.45 im pore size) into pre-washed polyethylene bottles, and acidified at pH 2. Finnigan Element 2 high resolution (HR)-IC-MPS was used to measure trace and rare earth elements (REE) concentrations under clean laboratory conditions, and (115In) was used as an internal standard. Because of the close relationship between light rare earth element (LREE) and Fe, riverine REE of the three were used to study the process trace element scavenging by Fe oxyhydroxides in three different two sub-basins of the lake. This confirmed by the significant positive correlation between Nd and Fe. The vertical distribution of Fe and Mn oxides were also used to investigate removal and release of trace elements in the water column. The normalized lacustrine REE to their riverine counterpart showed a gradual removal of REE across the lake, which was in the order of LREE>MREE>HREE. Hence, the rivers are the sole source of the lacustrine REE abundance. Coincidence of Fe maxima with those of Ce anomalies and La indicates that trace element profiles are chiefly controlled by the coating of Fe oxyhydroxides through oxidation of Fe2+ to Fe3+ under high dissolved oxygen contents and pH and vice versa. Due to differences in hydrodynamics between the extreme ends of the lake (upwelling in the southern end during the dry season), high mixing between bottom water and surface was observed at the surface in the Southern Basin while the mixing occurred mainly between 40 m and 80 m depth in the Northern Basin. There was also a clear similarity between Ba and NO3- and PO43- profiles in the southern end of the lake, supporting the idea that deep anoxic water, rich in nutrients and trace elements, are bought the surface during this period of intensive upwelling. In conclusion, the surface water chemical compositions of Lake Tanganyika are

  10. Lake Tanganyika Hydroclimate in the Pleistocene: Insights from New Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    Scholz, Christopher; Wood, Douglas

    2016-04-01

    Lake Tanganyika, in the western branch of the East African Rift, is one of the world's largest and oldest extant lakes, and undoubtedly holds a tropical paleoclimate record of unparalleled antiquity and fidelity. In anticipation of future scientific drilling in Lake Tanganyika, we present new analyses of basin-scale seismic reflection data from the central-southeastern parts of the lake. These analyses incorporate both newly reprocessed legacy multichannel data, as well as recently acquired commercial data sets from the region near Karema, Tanzania. The new analyses confirm the presence of thick sedimentary sections, in excess of 5 km in some localities, though the section in the immediate vicinity of Karema is thinner. Data from the southern part of the lake reveal a series of marked seismic-facies transitions, including the presence of older sediment packages that underlie previously identified "pre-rift" basement (the "Nyanja Event"). These older sediment packages may substantially predate the modern lake. The high-amplitude Nyanja Event is interpreted as the onset of late-Cenozoic rifting, and the changing character of the overlying depositional sequences reflects increasing relief in the rift valley, the variability of fluvial inputs, and the intermittent connectivity of upstream lake catchments. Earlier Tanganyika sequences are dominated by shallow lake and fluvial-lacustrine facies, whereas later sequences are characterized by extensive gravity flow deposition in deep water, and pronounced erosion and incision in shallow water depths and on littoral platforms. Extensive, well-defined progradational clinoform packages are observed in the Karema area, and are interpreted as paleodeltas of the Ifume River. These deposits are interpreted as Pleistocene in age due to their shallow position in the sedimentary section, and burial depths of less than 600 m. These deposits were laid down when the level of Lake Tanganyika was 250 m or more lower than present. The

  11. Airborne gravity gradiometer surveying of petroleum systems under Lake Tanganyika, Tanzania

    NASA Astrophysics Data System (ADS)

    Roberts, Doug; Chowdhury, Priyanka Roy; Lowe, Sharon Jenny; Christensen, Asbjorn Norlund

    2016-02-01

    The Lake Tanganyika South petroleum exploration block covers the southern portion of the Tanzanian side of Lake Tanganyika and is located within the East African Rift System. The rifting process has formed rotated fault blocks which provide numerous play types in the resulting basins. Interpretation of 2D seismic data from 1984 indicated that sufficient sediment thickness is present for hydrocarbon generation. The prospectivity of the lake sediment sequence is enhanced by large oil discoveries further north along the rift system at Lake Albert in Uganda. Airborne gravity gradiometry (AGG) has been used in the Lake Albert region to delineate the structural framework of sedimentary basins. Based on this analogy, in 2010 Beach Energy commissioned CGG to fly a FALCON AGG and high-resolution airborne magnetic survey over the Lake Tanganyika South block to provide data for mapping the basin architecture and estimating the depth to magnetic basement. A total of nearly 28000 line kilometres of data were acquired. The subsequent interpretation incorporated the AGG and magnetic data with available 2D seismic data, elevation model data, bathymetry, Landsat and regional geology information. The integrated data interpretation revealed that the Lake Tanganyika rifting structures occur as half-grabens that were formed through reactivation of Precambrian fault structures. Two major depocentres were identified in the magnetic depth-to-basement map in the north and in the west-central part of the survey area with sediment thicknesses in excess of 4 km and 3 km, respectively. Smaller, shallower depocentres (with less than 3 km of sediment) occur in the south-western region. This information was used to plan a 2100 km 2D marine seismic survey that was recorded in 2012. An interpretation of the results from the seismic survey confirmed a rifting structure similar to that encountered further north at Lake Albert in Uganda. Several targets were identified from the seismic sections for

  12. Century-Long Warming Trends in the Upper Water Column of Lake Tanganyika

    PubMed Central

    Kraemer, Benjamin M.; Hook, Simon; Huttula, Timo; Kotilainen, Pekka; O’Reilly, Catherine M.; Peltonen, Anu; Plisnier, Pierre-Denis; Sarvala, Jouko; Tamatamah, Rashid; Vadeboncoeur, Yvonne; Wehrli, Bernhard; McIntyre, Peter B.

    2015-01-01

    Lake Tanganyika, the deepest and most voluminous lake in Africa, has warmed over the last century in response to climate change. Separate analyses of surface warming rates estimated from in situ instruments, satellites, and a paleolimnological temperature proxy (TEX86) disagree, leaving uncertainty about the thermal sensitivity of Lake Tanganyika to climate change. Here, we use a comprehensive database of in situ temperature data from the top 100 meters of the water column that span the lake’s seasonal range and lateral extent to demonstrate that long-term temperature trends in Lake Tanganyika depend strongly on depth, season, and latitude. The observed spatiotemporal variation in surface warming rates accounts for small differences between warming rate estimates from in situ instruments and satellite data. However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements. Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously. Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change. PMID:26147964

  13. Acute schistosomiasis in European students returning from fieldwork at Lake Tanganyika, Tanzania.

    PubMed

    Steiner, Florian; Ignatius, Ralf; Friedrich-Jaenicke, Barbara; Dieckmann, Sebastian; Harms, Gundel; Poppert, Sven; Mockenhaupt, Frank P

    2013-01-01

    Schistosomiasis is common in many African regions and poses a risk for travelers and the local population. So far, schistosomiasis in travelers or expatriates returning from the Tanzanian bank of Lake Tanganyika has not been reported. We report a group of students who sought treatment with signs of acute schistosomiasis after having returned from Lake Tanganyika, Tanzania. Information as to travel and exposure as well as clinical and laboratory data were collected. Schistosomiasis was diagnosed in 8 of 16 students from Berlin, Germany, who had returned from a 2- to 3-month stay of fieldwork in Kigoma District at Lake Tanganyika, Tanzania. All 16 students reported frequent freshwater exposure at the lake. Six patients showed signs of acute schistosomiasis and had fever, and some of them also had cough, weakness, headache, or abdominal pain. Eosinophilia was present in five of the six symptomatic individuals. Notably, two serologically enzyme-linked immunosorbent assay (ELISA)-positive individuals did not report or present with symptoms or abnormal laboratory parameters. Schistosoma mansoni eggs were found in one symptomatic and one asymptomatic individual each. Blood and stool samples from the other eight individuals who were equally exposed to freshwater yielded negative results. This is the first report of an outbreak of acute schistosomiasis imported from the Tanzanian shore of Lake Tanganyika and highlights the risk for travelers and the local population of acquiring the infection in that part of Tanzania. It provides arguments for routine serological screening for schistosomiasis in individuals who had prior freshwater contact in endemic areas, irrespective of symptoms or other laboratory findings. © 2013 International Society of Travel Medicine.

  14. Temporal Changes in Lead Depositions in East Africa: A Case Study of Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Odigie, K. O.; Flegal, A. R.

    2011-12-01

    Environmental changes (e.g., increasing rates of soil erosion) in East Africa have been attributed to local human activities and global climate change. However, reports on the impacts of these changes on the remobilization and transport of heavy metals, such as lead, in the environment are presently limited in literature. Therefore, this study was designed to chronicle the historic transport and deposition of lead in East Africa as recorded in the sediments of Lake Tanganyika. Sediment cores collected from regions with varying anthropogenic impacts of Lake Tanganyika were divided into sections, dated using excess lead-210, and analyzed for lead concentrations and isotopic composition. The results show that the amount of lead deposited in some regions of the lake increased recently (e.g., by more than 25% over the past two decades preceding 2000) which is consistent with regional changes in sediment accumulation rates in Lake Tanganyika. Temporal changes in the sources of that lead are being characterized by their isotopic compositions.

  15. Geologic hypotheses of Lake Tanganyika region, Zaire, drawn from ERTS imagery

    NASA Technical Reports Server (NTRS)

    Wolyce, U.; Ilunga, S.

    1974-01-01

    Based on initial work in the Lake Tanganyika area of eastern Zaire, it has been concluded that ERTS imagery is extremely useful for reconnaissance level geologic mapping and analysis in this region of the humid tropics. In particular, ERTS imagery has proven useful for recognizing and mapping regional structural units, for recognizing major structural features, and for arriving at some preliminary hypotheses about the mineral potential of the area. Results so far indicate that ERTS imagery can make a major contribution to the development of the mineral resources of the country. Research has concentrated on applications of ERTS imagery in the field of cartography, geology, forestry, hydrology and agriculture. For the work in geology, a test site was chosen in eastern Zaire on the shore of Lake Tanganyika in the vicinity of the Lukuga River. This area was selected because of its varied geology and the existence of two frames of cloud-free ERTS imagery.

  16. Alternative Reproductive Tactics in the Shell-Brooding Lake Tanganyika Cichlid Neolamprologus brevis

    PubMed Central

    Ota, Kazutaka; Aibara, Mitsuto; Morita, Masaya; Awata, Satoshi; Hori, Michio; Kohda, Masanori

    2012-01-01

    Alternative reproductive tactics (ARTs) are found in several Lake Tanganyika shell-brooding cichlids. Field studies were conducted in the Wonzye population to examine reproductive ecology and ARTs in the Lake Tanganyika shell-brooding cichlid Neolamprologus brevis. We discovered that this fish occurred in both rocky- and sandy-bottom habitats, but in rocky habitats, brood-caring females exclusively occurred in shell-patches that another cichlid species created. All N. brevis of both sexes in the patches were sexually mature, whereas immature males and females with unripe eggs were found frequently in sandy-bottom habitats. Males in sandy-bottom habitats were smaller, but fed more frequently and were in better somatic condition than males in the patches. Similar tendency was found in females. This indicates that N. brevis uses different habitats depending on the stage of its life history, with migration from sandy-bottom habitats to the shell-patches for reproduction. Males in the patches exhibited different behavior patterns: floating above the patches and lying in the patches. The former was larger, more aggressive, and invested less in gonads (relative to body size) than the latter. These results accord with those of other shell-brooding Lake Tanganyika cichlids with ARTs, and they therefore suggest the presence of ARTs in N. brevis. PMID:22888463

  17. Alternative Reproductive Tactics in the Shell-Brooding Lake Tanganyika Cichlid Neolamprologus brevis.

    PubMed

    Ota, Kazutaka; Aibara, Mitsuto; Morita, Masaya; Awata, Satoshi; Hori, Michio; Kohda, Masanori

    2012-01-01

    Alternative reproductive tactics (ARTs) are found in several Lake Tanganyika shell-brooding cichlids. Field studies were conducted in the Wonzye population to examine reproductive ecology and ARTs in the Lake Tanganyika shell-brooding cichlid Neolamprologus brevis. We discovered that this fish occurred in both rocky- and sandy-bottom habitats, but in rocky habitats, brood-caring females exclusively occurred in shell-patches that another cichlid species created. All N. brevis of both sexes in the patches were sexually mature, whereas immature males and females with unripe eggs were found frequently in sandy-bottom habitats. Males in sandy-bottom habitats were smaller, but fed more frequently and were in better somatic condition than males in the patches. Similar tendency was found in females. This indicates that N. brevis uses different habitats depending on the stage of its life history, with migration from sandy-bottom habitats to the shell-patches for reproduction. Males in the patches exhibited different behavior patterns: floating above the patches and lying in the patches. The former was larger, more aggressive, and invested less in gonads (relative to body size) than the latter. These results accord with those of other shell-brooding Lake Tanganyika cichlids with ARTs, and they therefore suggest the presence of ARTs in N. brevis.

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

    PubMed Central

    Rüber, Lukas; Verheyen, Erik; Meyer, Axel

    1999-01-01

    The current phylogenetic hypothesis for the endemic Lake Tanganyika cichlid fishes of the tribe Eretmodini is based solely on morphology and suggests that more complex trophic morphologies derived only once from a less specialized ancestral condition. A molecular phylogeny of eretmodine cichlids based on partial mitochondrial DNA cytochrome b and control-region sequences was used to reconstruct the evolutionary sequence of trophic adaptations and to test alternative models of morphological divergence. The six mitochondrial lineages found disagree with the current taxonomy and the morphology-based phylogeny. Mitochondrial lineages with similar trophic morphologies are not grouped monophyletically but are typically more closely related to lineages with different trophic phenotypes currently assigned to other genera. Our results indicate multiple independent origins of similar trophic specializations in these cichlids. A pattern of repeated divergent morphological evolution becomes apparent when the phylogeography of the mitochondrial haplotypes is analyzed in the context of the geological and paleoclimatological history of Lake Tanganyika. In more than one instance within Lake Tanganyika, similar morphological divergence of dentitional traits occurred in sympatric species pairs. Possibly, resource-based divergent selective regimes led to resource partitioning and brought about similar trophic morphologies independently and repeatedly. PMID:10468591

  19. Changes in Biological Production and Lake Chemistry in Lake Tanganyika over the Past 400 Years

    NASA Astrophysics Data System (ADS)

    Hartwell, A. M.; Montanye, B.; Cohen, A.; McKay, J. L.; Severmann, S.; McManus, J.

    2015-12-01

    We present biogenic silica (BSi) data as a proxy for primary productivity in three cores from the Luiche Platform region of Lake Tanganyika. We also present complementary sedimentary records of the nitrogen and organic carbon isotopes. Preliminary analysis of the BSi data suggests that in two cores located at approximately 100 meters, productivity began to decline at approximately 1700 CE with an initial plateau at roughly 1800 CE. Since approximately 1800 CE, the sedimentary biogenic silica contents vary, but are generally lower than in the earlier portions of the record. These observations are consistent with prior work; however, our results suggest that the decline in primary production may have occurred earlier at these shallower sites than previously inferred for a deeper core (Tierney et al., 2010). This different response between the shallower sites and deeper off shore sites may be driven by differences in nutrient supply, spatial variability, or some other factor. Sedimentary nitrogen isotope data generally show an inverse relationship to the BSi data in the shallower cores. One possible interpretation of this inverse relationship is that there is a shift in the source of the primary nitrogen being utilized within the photic zone, with a larger contribution of nitrogen fixation occurring during times of lower productivity and a larger contribution of upwelled nitrogen occurring during times of higher productivity. Tierney, J.E., M.M. Mayes, N. Meyer, C. Johnson, P. Swarzenski, A.S. Cohen, and J.M. Russell (2010) The Unprecedented Warming of Lake Tanganyika. Nature Geoscience, 3, 422-425, DOI: 10.1038/NGEO865

  20. Mercury biomagnification in the food web of Lake Tanganyika (Tanzania, East Africa).

    PubMed

    Campbell, L; Verburg, Piet; Dixon, D G; Hecky, R E

    2008-09-01

    Lake Tanganyika is a globally important lake with high endemic biodiversity. Millions of people in the lake basin depend on several fish species for consumption. Due to the importance of fish consumption as an exposure route of mercury to humans, we sampled Lake Tanganyika in 2000 to assess total mercury concentrations and biomagnification of total mercury through the food web. Stable nitrogen and carbon isotope analyses of food web structure indicate a complex food web with overlapping omnivory with some specialist fish species. Stable nitrogen isotope analyses further confirm that mercury is biomagnifying through the Tanganyika food web at rates similar to those seen in Lakes Malawi and Victoria, the other two African Great Lakes. Most collected fish species and all invertebrate species had mercury concentrations below 0.2 microg Hg/g wet weight. However, several fish species, Ctenochromis horei (average 0.15 microg/g ww), Neolamprologus boulengeri (0.2 microg/g ww) , Bathybates spp.spp. (0.21 microg/g ww), Mastacembelus cunningtoni (0.22 microg/g ww) and Clarias theodorae (0.22 microg/g ww) approached or slightly exceeded the World Health Organization (WHO)'s recommended guideline of 0.2 microg Hg/g for vulnerable populations with high rates of fish consumption. Two individuals of the piscivorous fish species Lates microlepis (0.54, 0.78 microg/g ww) and a Polypterus congicus (1.3 microg/g ww) exceeded the international marketing limit value of 0.5 microg/g ww. Because C. theodorae and L. microlepis are also important market fish species, there is a need to monitor mercury concentrations in internationally marketed fish from Lake Tanganikya to ensure that those fish do not present a risk to human consumers.

  1. Ancient divergence in bathypelagic lake tanganyika deepwater cichlids: mitochondrial phylogeny of the tribe bathybatini.

    PubMed

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

    2005-03-01

    The cichlid species flock of Lake Tanganyika represents a polyphyletic assemblage of eight ancestral lineages, which colonized the emerging lake independently. Our study is focused on one of these lineages, the Bathybatini, a tribe of specialized piscivorous cichlids of the deep pelagic zone. By analyzing three mtDNA gene segments of all eight species of the tribe and two species of the closely related Trematocarini, we propose on the basis of a linearized tree analysis that the Bathybatini comprise two distinct lineages, the genera Hemibates and Bathybates, that seeded the primary lacustrine Tanganyika radiation independently. The genus Hemibates is likely to represent a distinct lineage that emerged simultaneously with the tribe Trematocarini and the genus Bathybates and should be therefore treated as a distinct tribe. Within the genus Bathybates, B. minor clearly represents the most ancestral split and is likely to have diverged from the remaining species in the course of the "primary lacustrine Tanganyika radiation" during which also the radiations of the Lamprologini and the H-lineage took place. The remaining "large" Bathybates species also diversified almost simultaneously and in step with the diversification of other Tanganyikan lineages-the Limnochromini and Cyprichromini-with B. graueri occupying the most ancestral branch, suggesting that these were induced by the same environmental changes. The lack of geographic color morphs suggests that competition and resource partitioning, rather than allopatric speciation, promoted speciation within the genus Bathybates.

  2. Mitochondrial phylogeny of the endemic mouthbrooding lineages of cichlid fishes from Lake Tanganyika in eastern Africa.

    PubMed

    Sturmbauer, C; Meyer, A

    1993-07-01

    Of the three cichlid species flocks in eastern Africa, Lake Tanganyika harbors the oldest species assemblage, which is also the most diverse morphologically and behaviorally. For 12 species (20 individuals) of 12 genera of the tribe Ectodini, 852 bp from two segments (cytochrome b and control region) of the mitochondrial genome were sequenced. In addition, orthologous sequences were obtained from eight species (11 individuals) representing other mouthbrooding lineages from Lake Tanganyika. Comparisons of sequence divergences revealed that the single Tanganyikan tribe Ectodini appears to be approximately five times older than the whole Lake Malawi cichlid species flock, suggesting that the radiation of the Tanganyikan mouthbrooding lineages took place long before the species flocks of Lakes Malawi and Victoria evolved. Seven of nine surveyed tribes of Tanganyikan cichlids appear to be approximately equally divergent, and this seems to corroborate the hypothesis of a rapid simultaneous formation of lineages at an early stage in the history of the Lake Tanganyika species flock. The close genetic relationship between the endemic Tropheus lineage and a nonendemic "Haplochromine," Astatotilapia burtoni, indicates that members of the tribe Tropheini may be the sister group of the cichlid flocks of Lakes Malawi and Victoria. The phylogenetic analyses demonstrate the monophyly of the Ectodini and identify the Cyprichromini as their sister group among the Tanganyikan cichlids. Within the tribe Ectodini the molecular data suggest both a branching pattern different than that previously proposed and a subdivision of the Ectodini into four clades, instead of the two originally described. The previously postulated model of morphological transformations believed to be responsible for the drastically different types of ecological specialization found among the Ectodini might therefore be in need of reinterpretation. Characters immediately related to foraging and nutrition seem to

  3. Facies distributions within contrasting structural components of a rift lake: Lake Tanganyika, Africa

    SciTech Connect

    Soreghan, M.J.; Cohen, A.S. )

    1991-03-01

    Lake Tanganyika is the most widely cited modern analog for interpreting ancient rift lakes; thus, understanding controls on its facies distribution is critical for refining stratigraphic models for rifts. Four recurrent margin types occur along the alternating half-graben structure of the lake: rift axes, platforms, escarpments, and accommodation zones. Data from study sites in the northern part of the lake suggest that predictable facies differences exist between these structural margin types. The rift axis site comprises a low-gradient, clastic (wave/current)-dominated deltaic system, with strong facies asymmetry and minor carbonate accumulations on raised benches. The platform margin site comprises a series of structurally controlled benches over which long, continuous facies tracts occur. Carbonate sands, muds, and shell gravel dominate; clastics are limited to moderate-sized silty deltas and long, narrow shoreface sands. The escarpment margin site is a steep-gradient system along which small ({lt}1 km{sup 2}) fan deltas alternate with cemented talus. The accommodation zone margin sites are also dominated by rugged structural relief, generally small fan deltas, and semicontinuous shoreface sand belts ({gt}5 km) onshore and poorly sorted silts offshore. TOC from fine-grained samples reflects the contrast in margin types. TOC values for the platform and rift axis range from 0.4 - 2.1 wt. % (avg. 1.3%), whereas accommodation zone and escarpment margin values range from 0.5-5.5% (avg. 3.0%). Acid insoluble sulfur shows a similar trend. Although all data are significantly correlated with depth, the relative area of the lake margin above and below the oxicline is directly controlled by the structural style of the lake margin.

  4. Trematodes indicate animal biodiversity in the Chilean intertidal and Lake Tanganyika.

    PubMed

    Hechinger, Ryan F; Lafferty, Kevin D; Kuris, Armand M

    2008-08-01

    Trematode communities in populations of estuarine snails can reflect surrounding animal diversity, abundance, and trophic interactions. We know less about the potential for trematodes to serve as bioindicators in other habitats. Here, we reanalyze data from 2 published studies concerning trematodes, 1 in the Chilean rocky intertidal zone and the other from the East African rift lake, Lake Tanganyika. Our analyses indicate that trematodes are more common in protected areas and that in both habitats they are directly and positively related to surrounding host abundance. This further supports the notion that trematodes in first intermediate hosts can serve as bioindicators of the condition of free-living animal communities in diverse ecosystems.

  5. Paleolimnological investigations of anthropogenic environmental change in Lake Tanganyika: I. An introduction to the project

    USGS Publications Warehouse

    Cohen, A.S.; Palacios-Fest, M. R.; McGill, J.; Swarzenski, P.W.; Verschuren, D.; Sinyinza, R.; Songori, T.; Kakagozo, B.; Syampila, M.; O'Reilly, C. M.; Alin, S.R.

    2005-01-01

    We investigated paleolimnological records from a series of river deltas around the northeastern rim of Lake Tanganyika, East Africa (Tanzania and Burundi) in order to understand the history of anthropogenic activity in the lake's catchment over the last several centuries, and to determine the impact of these activities on the biodiversity of littoral and sublittoral lake communities. Sediment pollution caused by increased rates of soil erosion in deforested watersheds has caused significant changes in aquatic communities along much of the lake's shoreline. We analyzed the effects of sediment discharge on biodiversity around six deltas or delta complexes on the east coast of Lake Tanganyika: the Lubulungu River delta, Kabesi River delta, Nyasanga/Kahama River deltas, and Mwamgongo River delta in Tanzania; and the Nyamuseni River delta and Karonge/Kirasa River deltas in Burundi. Collectively, these deltas and their associated rivers were chosen to represent a spectrum of drainage-basin sizes and disturbance levels. By comparing deltas that are similar in watershed attributes (other than disturbance levels), our goal was to explore a series of historical "experiments" at the watershed scale, with which we could more clearly evaluate hypotheses of land use or other effects on nearshore ecosystems. Here we discuss these deltas, their geologic and physiographic characteristics, and the field procedures used for coring and sampling the deltas, and various indicators of anthropogenic impact. ?? Springer 2005.

  6. Mitochondrial phylogeography of rock-dwelling cichlid fishes reveals evolutionary influence of historical lake level fluctuations of Lake Tanganyika, Africa.

    PubMed

    Verheyen, E; Rüber, L; Snoeks, J; Meyer, A

    1996-06-29

    The East African Lakes Tanganyika, Malawi and Victoria each harbour hundreds of endemic invertebrate and vertebrate species. Inferences about the ecological and evolutionary processes responsible for the origin of these species flocks will only be possible when they are made within historical and comparative frameworks. Specifically, the relative importance of intrinsic characteristics and extrinsic factors may offer information about the processes that drive diversification and speciation in these species. We investigated the sequence variation of a segment of the mitochondrial DNA control region of 32 populations representing all four nominal species in the three genera of eretmodine cichlids from Lake Tanganyika. Based on a phylogenetic analysis of these data we attempted to evaluate the importance of major lake level fluctuations on patterns of intralacustrine speciation. The geography of genetic variation reveals a high degree of within-lake endemism among genetically well-separated lineages distributed along the inferred shore lines of three historically intermittent lake basins. Seismic data indicate that extreme lowering of water levels in the Pleistocene caused the single Lake Tanganyika basin to split into three isolated ones. The strong phylogeographic structure of the Eretmodini, and the observation that some closely related populations occur on opposite shores of the lake, agree with this geological scenario. The three-clade-three-basin phylogeographic pattern was repeated twice within this tribe of cichlids. The phylogeographic pattern of eretmodine cichlids suggests that major fluctuations in the level of the lake have been important in shaping their adaptive radiation and speciation. The mitochondrially defined clades are in conflict with the current taxonomy of the group and suggest that there has been convergent evolution in trophic morphology, particularly in the shapes of oral teeth, taxonomically the most diagnostic characters of the three

  7. Big fish, little divergence: phylogeography of Lake Tanganyika's giant cichlid, Boulengerochromis microlepis.

    PubMed

    Koblmüller, Stephan; Odhiambo, Elizabeth A; Sinyinza, Danny; Sturmbauer, Christian; Sefc, Kristina M

    2015-04-01

    The largely endemic cichlid species flocks of the East African Great Lakes are among the prime examples for explosive speciation and adaptive radiation. Speciation rates differ among cichlid lineages, and the propensity to radiate has been linked to intrinsic and extrinsic factors such as sexual selection and ecological opportunity. Remarkably, only one cichlid tribe-the Boulengerochromini-comprises just a single species, Boulengerochromis microlepis, a predominantly piscivorous endemic of Lake Tanganyika and the world's largest cichlid. While the lineage diverged from its closest relatives at the onset of the Lake Tanganyika radiation >8 MYA, mitochondrial control region sequences collected in this study dated the most recent common ancestor of B. microlepis to ~60-110 KYA. There was no evidence of phylogeographic structure in the lake-wide sample. Patterns of genetic diversity and demographic analyses were consistent with slow and steady population growth throughout the reconstructed timescale. Additionally, the shallow divergence within the species may be related to a possibly large variance in reproductive success in this highly fecund species. Trophic niche space restriction by sympatric piscivores, lack of geographic structure, low potential for sexual selection arising from the monogamous mating system and extinction may have contributed to keeping the lineage monotypic.

  8. Greenwoodochromini Takahashi from Lake Tanganyika is a junior synonym of Limnochromini poll (Perciformes: Cichlidae).

    PubMed

    Takahashi, T

    2014-04-01

    The infraorbitals (IOs) of four species endemic to Lake Tanganyika were examined and on the basis of this information and previous morphological and molecular studies, the tribe Greenwoodochromini is synonymized with the tribe Limnochromini and a new combination for Limnochromis abeelei and Limnochromis staneri is proposed: Greenwoodochromis abeelei and Greenwoodochromis staneri. The revised tribe Limnochromini, comprising 10 species belonging to seven genera, is characterized by IOs representing types G and I. The revised genus Greenwoodochromis, which consists of four species, is characterized by IOs representing type I. © 2014 The Fisheries Society of the British Isles.

  9. Stable Isotopes Reveal Nitrogen Loading to Lake Tanganyika from Remote Shoreline Villages

    NASA Astrophysics Data System (ADS)

    Kelly, Brianne; Mtiti, Emmanuel; McIntyre, Peter B.; Vadeboncoeur, Yvonne

    2017-02-01

    Access to safe water is an ongoing challenge in rural areas in Tanzania where communities often lack access to improved sanitation. Methods to detect contamination of surface water bodies, such as monitoring nutrient concentrations and bacterial counts, are time consuming and results can be highly variable in space and time. On the northeast shore of Lake Tanganyika, Tanzania, the low population density coupled with the high potential for dilution in the lake necessitates the development of a sensitive method for detecting contamination in order to avoid human health concerns. We investigated the potential use of nitrogen and carbon stable isotopes of snail tissues to detect anthropogenic nutrient loading along the northeast shore of Lake Tanganyika. δ15N of snails was positively related to human population size in the nearest village, but only for villages with >4000 inhabitants. The areal footprint of villages within their watershed was also significantly correlated with snail δ15N, while agricultural land use and natural vegetation were not. Dissolved nutrient concentrations were not significantly different between village and reference sites. Our results indicate that nitrogen isotopes provide a sensitive index of local nutrient loading that can be used to monitor contamination of oligotrophic aquatic environments with low surrounding population densities.

  10. Stable Isotopes Reveal Nitrogen Loading to Lake Tanganyika from Remote Shoreline Villages.

    PubMed

    Kelly, Brianne; Mtiti, Emmanuel; McIntyre, Peter B; Vadeboncoeur, Yvonne

    2017-02-01

    Access to safe water is an ongoing challenge in rural areas in Tanzania where communities often lack access to improved sanitation. Methods to detect contamination of surface water bodies, such as monitoring nutrient concentrations and bacterial counts, are time consuming and results can be highly variable in space and time. On the northeast shore of Lake Tanganyika, Tanzania, the low population density coupled with the high potential for dilution in the lake necessitates the development of a sensitive method for detecting contamination in order to avoid human health concerns. We investigated the potential use of nitrogen and carbon stable isotopes of snail tissues to detect anthropogenic nutrient loading along the northeast shore of Lake Tanganyika. δ(15)N of snails was positively related to human population size in the nearest village, but only for villages with >4000 inhabitants. The areal footprint of villages within their watershed was also significantly correlated with snail δ(15)N, while agricultural land use and natural vegetation were not. Dissolved nutrient concentrations were not significantly different between village and reference sites. Our results indicate that nitrogen isotopes provide a sensitive index of local nutrient loading that can be used to monitor contamination of oligotrophic aquatic environments with low surrounding population densities.

  11. Distribution of organic facies in recent sediments in northern part of Lake Tanganyika

    SciTech Connect

    Huc, A.Y.; Vandenbroucke, M.; Bessereau, G.; Le Fournier, J.

    1987-05-01

    A better understanding of the relation between the organic facies and the depositional environments is a basic prerequisite to allow predictions of the lateral variations of source rocks and then to achieve realistic quantitative evaluation of the petroleum potential of a sedimentary basin. Lake Tanganyika is a suitable example to address the problem of organic sedimentology in an environment related to a rifting situation. More than 400 dredged samples have been used to construct detailed maps of the organic facies in the surficial sediments of the northern part of Lake Tanganyika. These maps include Bujumbura and Rumonge basins. Beyond an apparent complex pattern, the distribution of the organic facies can be explained in terms of differential preservation and sedimentological processes including pelagic sedimentation on the top of structural blocks, winnowing processes which drive the low-density organic matter from the shallow agitated waters (above the thermocline) toward depocenters in the deepest parts of the basin, and gravity transport mechanisms which dispatch sediments together with their specific organic content along sedimentary transit pathways. In this lake the main biological precursors for the sedimentary organic matter are diatoms. Organic geochemical studies including kerogen analyses and pyrolysis-GC show that the preeminent factor controlling the quality of the organic material, principally its hydrogen richness (in other words, its petroleum potential), is the extent of its degradation which is closely related to the depositional environment (oxic environment above the thermocline versus anoxic environment below the thermocline).

  12. Paleolimnology of Lake Tanganyika, East Africa, over the past 100 k yr

    USGS Publications Warehouse

    Scholz, C.A.; King, J.W.; Ellis, G.S.; Swart, Peter K.; Stager, J.C.; Colman, Steven M.

    2003-01-01

    New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey over the Kavala Island Ridge (KIR), a sedimented basement high that separates the Kigoma and Kalemie Basins in Lake Tanganyika. Proxy analyses of paleoclimate response carried out on core T97-52V include paleomagnetic and index properties, TOC and isotopic analyses of organic carbon, and diatom and biogenic silica analyses. A robust age model based on 11 radiocarbon (AMS) dates indicates a linear, continuous sedimentation rate nearly an order of magnitude slower here compared to other core sites around the lake. This age model indicates continuous sedimentation over the past 79 k yr, and a basal age in excess of 100 k yr. The results of the proxy analyses for the past ??? 20 k yr are comparable to previous studies focused on that interval in Lake Tanganyika, and show that the lake was about 350 m lower than present at the Last Glacial Maximum (LGM). Repetitive peaks in TOC and corresponding drops in ??13C over the past 79 k yr indicate periods of high productivity and mixing above the T97-52V core site, probably due to cooler and perhaps windier conditions. From ??? 80 through ??? 58 k yr the ??13C values are relatively negative (-26 to -28???) suggesting predominance of algal contributions to bottom sediments at this site during this time. Following this interval there is a shift to higher values of ??13C, indicating a possible shift to C-4 pathway-dominated grassland-type vegetation in the catchment, and indicating cooler, dryer conditions from ??? 55 k yr through the LGM. Two seismic sequence boundaries are observed at shallow stratigraphic levels in the seismic reflection data, and the upper boundary correlates to a major discontinuity

  13. Toward a generic method for studying water renewal, with application to the epilimnion of Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Gourgue, Olivier; Deleersnijder, Eric; White, Laurent

    2007-09-01

    We present a method, based on the concept of age and residence time, to study the water renewal in a semi-enclosed domain. We split the water of this domain into different water types. The initial water is the water initially present in the semi-enclosed domain. The renewing water is defined as the water entering the domain of interest. Several renewing water types may be considered depending on their origin. We present the equations for computing the age and the residence time of a certain water type. These timescales are of use to understand the rate at which the water renewal takes place. Computing these timescales can be achieved at an acceptable extra computer cost. The above-mentioned method is applied to study the renewal of epilimnion (i.e. the surface layer) water in Lake Tanganyika. We have built a finite element reduced-gravity model modified to take into account the water exchange between the epilimnion and the hypolimnion (i.e. the bottom layer), the water supply from precipitation and incoming rivers, and the water loss from evaporation and the only outgoing river. With our water renewal diagnoses, we show that the only significant process in the renewal of epilimnion water in Lake Tanganyika is the water exchange between the epilimnion and the hypolimnion, other phenomena being negligible.

  14. Crustal Structure at a Young Continental Rift: A Receiver Function Study from Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Hodgson, I. D. S.; Illsley-Kemp, F.; Gallacher, R. J.; Keir, D.; Ebinger, C. J.; Drooff, C.; Khalfan, M.

    2015-12-01

    Lake Tanganyika, in western Tanzania, spans a large section of the Western rift yet there are very few constraints on bulk crustal and upper mantle structure. The Western rift system has no surface expression of magmatism, which is in stark contrast to the Eastern branch. This observation is difficult to reconcile with the approximately coeval initiation of rifting of the two branches. The variation in the nature of rifting provides a perfect setting to test current hypotheses for the initiation of continental breakup and early-stage development of continental rifts. The deployment of a seismic network of 13 broadband instruments on the south eastern shore of Lake Tanganyika, for 16 months, between 2014 and 2015 provides a unique opportunity to investigate extensional processes in thick continental lithosphere. We present here results from a P to S receiver function study that provides information on bulk crustal Vp/Vs ratio along the rift; a property that is sensitive to the presence of magmatic intrusions in the lower crust. Additionally this method allows us to map variations in crustal thickness both parallel and perpendicular to the rift axis. These results thus provide unprecedented insight into the large-scale mechanics of early-stage continental rifting along the non-volcanic Western rift.

  15. High-Resolution Reconstructions of Temperature and Precipitation During the Last Millennium from Lake Tanganyika, Africa

    NASA Astrophysics Data System (ADS)

    Mayes, M.; Tierney, J.; Huang, Y.; Russell, J.

    2008-12-01

    Though numerous syntheses of high-resolution paleoclimate data have documented temperature changes associated with the Medieval Period, the Little Ice Age, and the Industrial era in north temperate regions, few records of temperature variability exist for the Southern Hemisphere (Mann and Jones, 2003, GRL doi: 10.1029/2003GL017814). Here, we present a new, high-resolution record of terrestrial temperature and rainfall from southeast tropical Africa, based upon organic geochemical analyses of annually laminated sediment cores from Lake Tanganyika, East Africa, providing the first millennium-long, high-resolution record of temperature from the East African tropics. Extending to 700CE with decadal resolution, the record uses the TEX86 paleothermometer and hydrogen stable isotope ratios (dD) of leaf waxes, which have been shown to reflect temperature and hydrologic conditions in Tanganyika, respectively (Tierney 2008, Science). The TEX86-based temperature reconstruction shows that Tanganyika temperatures were relatively warm at 700CE, cooler from 800-1000CE, and then warmer again between approximately 1050-1300CE. The latter warm interval is coincident with periods of warmer temperatures documented in the Northern Hemisphere. Yet temperatures are highly variable within the Little Ice Age (~1450-1800CE) and do not cool substantially relative to older time periods, in contrast to north temperate regions. Pronounced warming from approximately 1850 to the present is unprecedented in comparison to patterns of temperature variability during the previous centuries. The temperature variability documented here does not seem to correspond strongly to lake level fluctuations in Tanganyika over the past millennium (Cohen et al., 2005, JoPL, doi 10.1007/s10933-005- 2422-4), suggesting that Southeast African climate variability is more complex than alternating cycles of warm/wet and cool/dry conditions. dD analyses document considerable hydrologic variability over the past

  16. Trematodes indicate animal biodiversity in the chilean intertidal and Lake Tanganyika

    USGS Publications Warehouse

    Hechinger, R.F.; Lafferty, K.D.; Kuris, A.M.

    2008-01-01

    Trematode communities in populations of estuarine snails can reflect surrounding animal diversity, abundance, and trophic interactions. We know less about the potential for trematodes to serve as bioindicators in other habitats. Here, we reanalyze data from 2 published studies concerning trematodes, 1 in the Chilean rocky intertidal zone and the other from the East African rift lake, Lake Tanganyika. Our analyses indicate that trematodes are more common in protected areas and that in both habitats they are directly and positively related to surrounding host abundance. This further supports the notion that trematodes in first intermediate hosts can serve as bioindicators of the condition of free-living animal communities in diverse ecosystems. ?? American Society of Parasitologists 2008.

  17. Protist herbivory: a key pathway in the pelagic food web of Lake Tanganyika.

    PubMed

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

    2011-08-01

    Herbivory and bacterivory by phagotrophic protists were estimated in the southern basin of the oligotrophic Lake Tanganyika at different seasons (in the rainy season in February-March 2007 and in the dry season in July-August 2006 and September 2007), using two independent methods: the selective inhibitor technique for assessing community grazing on picocyanobacteria (PCya) and fluorescently labelled bacteria (FLB) and Synechococcus (FLA) to estimate bacterivory and herbivory by phagotrophic nanoflagellates (NF) and ciliates. Protistan grazing impact on both heterotrophic bacteria and PCya was mainly due to NF, which contributed up to 96% of the microbial grazing. There was a clear selection of FLA by protists. PCya represented the main carbon source for both flagellates and ciliates in the mixolimnion, accounting for an average of 83% of the total carbon obtained from the ingestion of picoplanktonic organisms. Protists were the main consumers of particulate primary production (46-74% depending on season). Significant seasonal variation of grazing rates (0.011-0.041 h(-1)) was found, chiefly following variation of PCya production and biomass. Assuming a growth efficiency of 0.4, total protozoan production varied seasonally (189-313 g C m(-2) day(-1)) and was roughly half of particulate phytoplankton production. This study provides evidence that NF and PCya were tightly coupled in Lake Tanganyika and that herbivory by protists may be one of the reasons why this great lake has high productivity. Our results bring support to the idea that microbial herbivory is a major process in oligotrophic freshwater systems.

  18. Persistent unstable atmospheric boundary layer enhances sensible and latent heat loss in a tropical great lake: Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Verburg, Piet; Antenucci, Jason P.

    2010-06-01

    Energy fluxes across the surface of lakes regulate heat storage and affect the water balance. Sensible and latent heat fluxes are affected by atmospheric stability, especially for large lakes. We examined the effect of atmospheric stability on the heat fluxes on seasonal time scales at Lake Tanganyika, East Africa, by estimating hourly sensible and latent heat fluxes and net radiation using thermistor chains and meteorological stations. The atmosphere was almost always unstable, in contrast to the atmosphere above North American Great Lakes which is unstable in winter and stable in summer. Persistent atmospheric instability resulted in a 13% and 18% increase in the annual mean heat loss by latent and sensible heat fluxes, respectively, relative to conditions of neutral stability. The persistent unstable atmosphere is caused by a higher water surface temperature compared with air temperature, which we argue is the case in general in (sub)tropical lakes. Low humidity further enhanced the frequency of unstable conditions and enhanced the exchange of heat and vapor from the lake to the atmosphere. The estimated heat fluxes were sensitive to the temporal scale of data inputs and to the local values of parameters such as air density. To our knowledge this is the first paper that demonstrates and quantifies the effect of atmospheric stability on latent and sensible heat fluxes from a lake on an annual basis, using data collected from the lake surface.

  19. Hidden biodiversity in an ancient lake: phylogenetic congruence between Lake Tanganyika tropheine cichlids and their monogenean flatworm parasites

    PubMed Central

    Vanhove, Maarten P. M.; Pariselle, Antoine; Van Steenberge, Maarten; Raeymaekers, Joost A. M.; Hablützel, Pascal I.; Gillardin, Céline; Hellemans, Bart; Breman, Floris C.; Koblmüller, Stephan; Sturmbauer, Christian; Snoeks, Jos; Volckaert, Filip A. M.; Huyse, Tine

    2015-01-01

    The stunning diversity of cichlid fishes has greatly enhanced our understanding of speciation and radiation. Little is known about the evolution of cichlid parasites. Parasites are abundant components of biodiversity, whose diversity typically exceeds that of their hosts. In the first comprehensive phylogenetic parasitological analysis of a vertebrate radiation, we study monogenean parasites infecting tropheine cichlids from Lake Tanganyika. Monogeneans are flatworms usually infecting the body surface and gills of fishes. In contrast to many other parasites, they depend only on a single host species to complete their lifecycle. Our spatially comprehensive combined nuclear-mitochondrial DNA dataset of the parasites covering almost all tropheine host species (N = 18), reveals species-rich parasite assemblages and shows consistent host-specificity. Statistical comparisons of host and parasite phylogenies based on distance and topology-based tests demonstrate significant congruence and suggest that host-switching is rare. Molecular rate evaluation indicates that species of Cichlidogyrus probably diverged synchronically with the initial radiation of the tropheines. They further diversified through within-host speciation into an overlooked species radiation. The unique life history and specialisation of certain parasite groups has profound evolutionary consequences. Hence, evolutionary parasitology adds a new dimension to the study of biodiversity hotspots like Lake Tanganyika. PMID:26335652

  20. Hidden biodiversity in an ancient lake: phylogenetic congruence between Lake Tanganyika tropheine cichlids and their monogenean flatworm parasites.

    PubMed

    Vanhove, Maarten P M; Pariselle, Antoine; Van Steenberge, Maarten; Raeymaekers, Joost A M; Hablützel, Pascal I; Gillardin, Céline; Hellemans, Bart; Breman, Floris C; Koblmüller, Stephan; Sturmbauer, Christian; Snoeks, Jos; Volckaert, Filip A M; Huyse, Tine

    2015-09-03

    The stunning diversity of cichlid fishes has greatly enhanced our understanding of speciation and radiation. Little is known about the evolution of cichlid parasites. Parasites are abundant components of biodiversity, whose diversity typically exceeds that of their hosts. In the first comprehensive phylogenetic parasitological analysis of a vertebrate radiation, we study monogenean parasites infecting tropheine cichlids from Lake Tanganyika. Monogeneans are flatworms usually infecting the body surface and gills of fishes. In contrast to many other parasites, they depend only on a single host species to complete their lifecycle. Our spatially comprehensive combined nuclear-mitochondrial DNA dataset of the parasites covering almost all tropheine host species (N = 18), reveals species-rich parasite assemblages and shows consistent host-specificity. Statistical comparisons of host and parasite phylogenies based on distance and topology-based tests demonstrate significant congruence and suggest that host-switching is rare. Molecular rate evaluation indicates that species of Cichlidogyrus probably diverged synchronically with the initial radiation of the tropheines. They further diversified through within-host speciation into an overlooked species radiation. The unique life history and specialisation of certain parasite groups has profound evolutionary consequences. Hence, evolutionary parasitology adds a new dimension to the study of biodiversity hotspots like Lake Tanganyika.

  1. Testing the stages model in the adaptive radiation of cichlid fishes in East African Lake Tanganyika

    PubMed Central

    Muschick, Moritz; Nosil, Patrik; Roesti, Marius; Dittmann, Marie Theres; Harmon, Luke; Salzburger, Walter

    2014-01-01

    Adaptive radiation (AR) is a key process in the origin of organismal diversity. However, the evolution of trait disparity in connection with ecological specialization is still poorly understood. Available models for vertebrate ARs predict that diversification occurs in the form of temporal stages driven by different selective forces. Here, we investigate the AR of cichlid fishes in East African Lake Tanganyika and use macroevolutionary model fitting to evaluate whether diversification happened in temporal stages. Six trait complexes, for which we also provide evidence of their adaptiveness, are analysed with comparative methods: body shape, pharyngeal jaw shape, gill raker traits, gut length, brain weight and body coloration. Overall, we do not find strong evidence for the ‘stages model’ of AR. However, our results suggest that trophic traits diversify earlier than traits implicated in macrohabitat adaptation and that sexual communication traits (i.e. coloration) diversify late in the radiation. PMID:25274371

  2. Genetic basis of male colour dimorphism in a Lake Tanganyika cichlid fish.

    PubMed

    Takahashi, T; Sota, T; Hori, M

    2013-06-01

    Phenotypic polymorphisms can be applied to study the micro-evolutionary forces that maintain genetic variation and can mediate speciation, but it can be difficult to determine the genetic basis of polymorphisms. Recently, restriction-site-associated DNA (RAD) sequencing has become popular, which can easily produce multiple single nucleotide polymorphisms from whole genomes. Here, we combined RAD sequencing, allele-specific PCR and Sanger sequencing to determine the genetic basis underlying male colour dimorphism of a Lake Tanganyika cichlid fish, Cyprichromis leptosoma. Our analyses using both a cross-family (two parents and 12 F2 males) and 64 wild individuals do not contradict a hypothesis that two alleles of one-locus control male colour dimorphism. Also, the locus may be located on a genome region that experiences reduced levels of recombination. Although more analyses will be needed to conclude these findings, this study is the first to suggest the genetic basis of a colour polymorphism using RAD sequencing.

  3. Testing the stages model in the adaptive radiation of cichlid fishes in East African Lake Tanganyika.

    PubMed

    Muschick, Moritz; Nosil, Patrik; Roesti, Marius; Dittmann, Marie Theres; Harmon, Luke; Salzburger, Walter

    2014-11-22

    Adaptive radiation (AR) is a key process in the origin of organismal diversity. However, the evolution of trait disparity in connection with ecological specialization is still poorly understood. Available models for vertebrate ARs predict that diversification occurs in the form of temporal stages driven by different selective forces. Here, we investigate the AR of cichlid fishes in East African Lake Tanganyika and use macroevolutionary model fitting to evaluate whether diversification happened in temporal stages. Six trait complexes, for which we also provide evidence of their adaptiveness, are analysed with comparative methods: body shape, pharyngeal jaw shape, gill raker traits, gut length, brain weight and body coloration. Overall, we do not find strong evidence for the 'stages model' of AR. However, our results suggest that trophic traits diversify earlier than traits implicated in macrohabitat adaptation and that sexual communication traits (i.e. coloration) diversify late in the radiation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  4. Chalinochromis cyanophleps, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika.

    PubMed

    Kullander, Sven O; Karlsson, Mikael; Karlsson, Magnus; Norén, Michael

    2014-04-22

    Chalinochromis cyanophleps is described from nine specimens, the largest 129 mm SL, from Namansi. It differs from other species of Chalinochromis in plain trunk colouration, absence of black stripes on the head, relatively narrow lips, presence of tricuspid jaw teeth, and presence of five rather than four dentary lateralis foramina. The blue iridescent stripe below the eye is shared with other lamprologin cichlids, but is broader and more conspicuous in C. cyanophleps. Chalinochromis cyanophleps occurs at depths between 6 and 45 m in rocky habitats along the Tanzanian coast of Lake Tanganyika, from Mvuna Island south to Kalala Island, a stretch of about 90 km. Field observations were made of specimens up to 18 cm total length. The COI DNA barcode sequence differs by 1.8% from that of C. popelini.

  5. A tribal level phylogeny of Lake Tanganyika cichlid fishes based on a genomic multi-marker approach.

    PubMed

    Meyer, Britta S; Matschiner, Michael; Salzburger, Walter

    2015-02-01

    The species-flocks of cichlid fishes in the East African Great Lakes Victoria, Malawi and Tanganyika constitute the most diverse extant adaptive radiations in vertebrates. Lake Tanganyika, the oldest of the lakes, harbors the morphologically and genetically most diverse assemblage of cichlids and contains the highest number of endemic cichlid genera of all African lakes. Based on morphological grounds, the Tanganyikan cichlid species have been grouped into 12-16 distinct lineages, so-called tribes. While the monophyly of most of the tribes is well established, the phylogenetic relationships among the tribes remain largely elusive. Here, we present a new tribal level phylogenetic hypothesis for the cichlid fishes of Lake Tanganyika that is based on the so far largest set of nuclear markers and a total alignment length of close to 18kb. Using next-generation amplicon sequencing with the 454 pyrosequencing technology, we compiled a dataset consisting of 42 nuclear loci in 45 East African cichlid species, which we subjected to maximum likelihood and Bayesian inference phylogenetic analyses. We analyzed the entire concatenated dataset and each marker individually, and performed a Bayesian concordance analysis and gene tree discordance tests. Overall, we find strong support for a position of the Oreochromini, Boulengerochromini, Bathybatini and Trematocarini outside of a clade combining the substrate spawning Lamprologini and the mouthbrooding tribes of the 'H-lineage', which are both strongly supported to be monophyletic. The Eretmodini are firmly placed within the 'H-lineage', as sister-group to the most species-rich tribe of cichlids, the Haplochromini. The phylogenetic relationships at the base of the 'H-lineage' received less support, which is likely due to high speciation rates in the early phase of the radiation. Discordance among gene trees and marker sets further suggests the occurrence of past hybridization and/or incomplete lineage sorting in the cichlid

  6. A tribal level phylogeny of Lake Tanganyika cichlid fishes based on a genomic multi-marker approach

    PubMed Central

    Meyer, Britta S.; Matschiner, Michael; Salzburger, Walter

    2015-01-01

    The species-flocks of cichlid fishes in the East African Great Lakes Victoria, Malawi and Tanganyika constitute the most diverse extant adaptive radiations in vertebrates. Lake Tanganyika, the oldest of the lakes, harbors the morphologically and genetically most diverse assemblage of cichlids and contains the highest number of endemic cichlid genera of all African lakes. Based on morphological grounds, the Tanganyikan cichlid species have been grouped into 12–16 distinct lineages, so-called tribes. While the monophyly of most of the tribes is well established, the phylogenetic relationships among the tribes remain largely elusive. Here, we present a new tribal level phylogenetic hypothesis for the cichlid fishes of Lake Tanganyika that is based on the so far largest set of nuclear markers and a total alignment length of close to 18 kb. Using next-generation amplicon sequencing with the 454 pyrosequencing technology, we compiled a dataset consisting of 42 nuclear loci in 45 East African cichlid species, which we subjected to maximum likelihood and Bayesian inference phylogenetic analyses. We analyzed the entire concatenated dataset and each marker individually, and performed a Bayesian concordance analysis and gene tree discordance tests. Overall, we find strong support for a position of the Oreochromini, Boulengerochromini, Bathybatini and Trematocarini outside of a clade combining the substrate spawning Lamprologini and the mouthbrooding tribes of the ‘H-lineage’, which are both strongly supported to be monophyletic. The Eretmodini are firmly placed within the ‘H-lineage’, as sister-group to the most species-rich tribe of cichlids, the Haplochromini. The phylogenetic relationships at the base of the ‘H-lineage’ received less support, which is likely due to high speciation rates in the early phase of the radiation. Discordance among gene trees and marker sets further suggests the occurrence of past hybridization and/or incomplete lineage sorting in

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

    PubMed

    Duftner, Nina; Sefc, Kristina M; Koblmüller, Stephan; Nevado, Bruno; Verheyen, Erik; Phiri, Harris; Sturmbauer, Christian

    2006-08-01

    Several lineages of cichlid fishes in the East African Great Lakes display stunning levels of morphological diversification. The rapid evolution of rock-dwelling polygynous mouthbrooders in Lake Malawi, for example, was in part ascribed to their allopatric distribution on disjunct stretches of rocky coast, where even short habitat discontinuities reduce gene flow effectively. However, as seen in other cichlids, ecological barriers do not always prevent gene flow, whereas genetic structure can develop along continuous habitat, and morphological diversification does not necessarily accompany genetic differentiation. The present study investigates the population structure of Variabilichromis moorii, a monogamous substrate-brooding lamprologine of rocky coasts in Lake Tanganyika, which occurs over about 1000 km of shoreline almost without phenotypic variation. Phylogeographic analyses of mitochondrial DNA sequences indicated that dispersal is infrequent and generally occurs between adjacent locations only. Exceptions to this pattern are closely related haplotypes from certain locations on opposite lakeshores, a phenomenon which has been observed in other species and is thought to reflect lake crossing along an underwater ridge in times of low water level. Genetic population differentiation, estimated from mitochondrial DNA and microsatellite data in six adjacent populations, was equally high across localities separated by sandy shores and along uninterrupted stretches of rocky shore. Our results suggest that ecological barriers are not required to induce philopatric behavior in Variabilichromis, and that morphological stasis persists in the face of high levels of neutral genetic differentiation.

  8. Nocturnal claroteine catfishes reveal dual colonisation but a single radiation in Lake Tanganyika.

    PubMed

    Peart, Claire R; Bills, Roger; Wilkinson, Mark; Day, Julia J

    2014-04-01

    Lake Tanganyika (LT) is a biodiversity hotspot supporting many endemic radiations that provide comparative systems in which to investigate if there are common factors leading to the build-up of its considerable diversity. Despite LT containing the highest diversity of lacustrine catfishes on Earth, the evolutionary relationships of nocturnal catfishes within the sub-family Claroteinae have not been investigated and it is unknown if its constituent genera have diversified via single or independent colonisation events. We report the first molecular phylogeny of the LT claroteine catfishes based on a multigene dataset (three nuclear markers, two mitochondrial totalling 4227 bp), including 85 samples from LT and outside of the lake basin. These data support LT claroteine monophyly, with the exclusion of the LT endemic Chrysichthys brachynema that independently colonised the lake but has not radiated. Multiple sampling localities from LT and the use of Bayesian species delimitation methods reveal additional locally restricted diversity within the LT Claroteinae clade. Fossil calibrated molecular divergence dates suggest that diversification occurred within full lake conditions as demonstrated in other LT lineages. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems.

    PubMed

    Cohen, Andrew S; Gergurich, Elizabeth L; Kraemer, Benjamin M; McGlue, Michael M; McIntyre, Peter B; Russell, James M; Simmons, Jack D; Swarzenski, Peter W

    2016-08-23

    Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a ∼1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa's deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last ∼150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last ∼500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika's extraordinary biodiversity and ecosystem services.

  10. Genetic population structure as indirect measure of dispersal ability in a Lake Tanganyika cichlid.

    PubMed

    Koblmüller, Stephan; Sefc, Kristina Maria; Duftner, Nina; Warum, Marko; Sturmbauer, Christian

    2007-06-01

    Diversification and speciation processes are influenced by intrinsic (ecological specialization, dispersal) and extrinsic (habitat structure and instability) factors, but the effect of ecological characteristics on dispersal is difficult to assess. This study uses mitochondrial control region sequences to investigate the population structure and demographic history of the endemic Lake Tanganyika cichlid Neolamprologus caudopunctatus with a preference for the rock-sand interface along two stretches of continuous, rocky shoreline, and across a sandy bay representing a potential dispersal barrier. Populations along uninterrupted habitat were not differentiated; whereas, the sandy bay separated two reciprocally monophyletic clades. The split between the two clades between 170,000 and 260,000 years BP coincides with a period of rising water level following a major lowstand, and indicates that clades remained isolated throughout subsequent lake level fluctuations. Low long-term effective population sizes were inferred from modest genetic diversity estimates, and may be due to recent population expansions starting from small population sizes 45,000-60,000 years BP. Comparisons with available data from specialized rock-dwelling species of the same area suggest that habitat structure and lake level fluctuations determine phylogeographic patterns on large scales, while fine-scale population structure and demography are modulated by species-specific ecologies.

  11. On the origin of the Synodontis catfish species flock from Lake Tanganyika.

    PubMed

    Day, Julia J; Wilkinson, Mark

    2006-12-22

    Species flocks within Great Lakes provide unique insights into the factors affecting diversification. Lake Tanganyika (LT) is of particular interest because it contains many endemic groups for which general factors affecting diversification can be discerned. Here, we present the first phylogenetic study of the LT Synodontis (Siluriformes, Mochokidae) species flock using mtDNA sequence data. Our data reveal some previously unrecognized species diversity and indicate that the LT species flock is not monophyletic, and that two closely related clades of endemics may have independently colonized LT. Other comparable small species flocks are characterized by a single colonization event. Molecular date estimates of the timing of the initial within-lake diversification of the LT endemics, based on a fossil calibration, are comparable to those reported for other groups, suggesting that extrinsic factors maybe important common causes of clade diversification. The basal divergence in the sampled Synodontis reveals an East-West African faunal split seen in many terrestrial, but few aquatic groups, the timing of which coincides with East African rifting events.

  12. Insights into the evolution of freshwater sponges (Porifera: Demospongiae: Spongillina): Barcoding and phylogenetic data from Lake Tanganyika endemics indicate multiple invasions and unsettle existing taxonomy.

    PubMed

    Erpenbeck, Dirk; Weier, Tina; de Voogd, Nicole J; Wörheide, Gert; Sutcliffe, Patricia; Todd, Jonathan A; Michel, Ellinor

    2011-10-01

    Sponges are a conspicuous element in many benthic habitats including in Africa's oldest, deepest lake, Lake Tanganyika. Despite their prevalence and pivotal ecological role as filter feeders, knowledge of the evolutionary history of sponges is in its infancy. Here, we provide the first molecular analysis targeting the evolution of sponges from Lake Tanganyika. Independent markers indicate the occurrence of several colonisation events which have shaped the current Tanganyikan lacustrine sponge biodiversity. This is in contrast to a range of previously studied organisms that have diversified within the lake from single lineages. Our tree reconstructions indicate the presence of two genera, Oncosclera and Eunapius, which are globally distributed. Therefore, we reject the hypothesis of monophyly for the sponges from Lake Tanganyika and challenge existing higher taxonomic structure for freshwater sponges. Copyright © 2011 Elsevier Inc. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

  14. Mastacembelid eels support Lake Tanganyika as an evolutionary hotspot of diversification.

    PubMed

    Brown, Katherine J; Rüber, Lukas; Bills, Roger; Day, Julia J

    2010-06-19

    Lake Tanganyika (LT) is the oldest of the African Rift Lakes and is one of the richest freshwater ecosystems on Earth, with high levels of faunal diversity and endemism. The endemic species flocks that occur in this lake, such as cichlid fishes, gastropods, catfish and crabs, provide unique comparative systems for the study of patterns and processes of speciation. Mastacembelid eels (Teleostei: Mastacembelidae) are a predominately riverine family of freshwater fish, occurring across Africa and Asia, but which also form a small species flock in LT. Including 25 species across Africa, plus Asian representatives as outgroups, we present the first molecular phylogenetic analysis for the group, focusing particularly on the evolutionary history and biodiversity of LT mastacembelid eels. A combined matrix of nuclear and mitochondrial genes based on 3118 bp are analysed implementing different phylogenetic methods, including Bayesian inference and maximum likelihood. LT Mastacembelus are recovered as monophyletic, and analyses reveal the rapid diversification of five main LT lineages. Relaxed molecular clock dates provide age estimates for the LT flock at approximately 7-8 Myr, indicating intralacustrine diversification, with further speciation events coinciding with periods of lower lake level. Our analyses also reveal as yet undescribed diversity of lacustrine and riverine species. A Southern-Eastern African clade, that is younger than the LT flock, is also recovered, while West African taxa are basal members of the African mastacembelid clade. That the LT species flock of mastacembelid eels appears to have colonised and immediately diversified soon after the formation of the lake, supports the view of LT as an evolutionary hotspot of diversification. We find evidence for biogeographic clades mirroring a similar pattern to other ichthyological faunas. In addition, our analyses also highlight a split of African and Asian mastacembelid eels at approximately 19 Myr that is

  15. Mastacembelid eels support Lake Tanganyika as an evolutionary hotspot of diversification

    PubMed Central

    2010-01-01

    Background Lake Tanganyika (LT) is the oldest of the African Rift Lakes and is one of the richest freshwater ecosystems on Earth, with high levels of faunal diversity and endemism. The endemic species flocks that occur in this lake, such as cichlid fishes, gastropods, catfish and crabs, provide unique comparative systems for the study of patterns and processes of speciation. Mastacembelid eels (Teleostei: Mastacembelidae) are a predominately riverine family of freshwater fish, occurring across Africa and Asia, but which also form a small species flock in LT. Methods Including 25 species across Africa, plus Asian representatives as outgroups, we present the first molecular phylogenetic analysis for the group, focusing particularly on the evolutionary history and biodiversity of LT mastacembelid eels. A combined matrix of nuclear and mitochondrial genes based on 3118 bp are analysed implementing different phylogenetic methods, including Bayesian inference and maximum likelihood. Results LT Mastacembelus are recovered as monophyletic, and analyses reveal the rapid diversification of five main LT lineages. Relaxed molecular clock dates provide age estimates for the LT flock at ~7-8 Myr, indicating intralacustrine diversification, with further speciation events coinciding with periods of lower lake level. Our analyses also reveal as yet undescribed diversity of lacustrine and riverine species. A Southern-Eastern African clade, that is younger than the LT flock, is also recovered, while West African taxa are basal members of the African mastacembelid clade. Conclusions That the LT species flock of mastacembelid eels appears to have colonised and immediately diversified soon after the formation of the lake, supports the view of LT as an evolutionary hotspot of diversification. We find evidence for biogeographic clades mirroring a similar pattern to other ichthyological faunas. In addition, our analyses also highlight a split of African and Asian mastacembelid eels at ~19

  16. Depth and substratum differentiations among coexisting herbivorous cichlids in Lake Tanganyika.

    PubMed

    Hata, Hiroki; Ochi, Haruki

    2016-11-01

    Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations.

  17. Depth and substratum differentiations among coexisting herbivorous cichlids in Lake Tanganyika

    PubMed Central

    Ochi, Haruki

    2016-01-01

    Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations. PMID:28018609

  18. Disentangling Incomplete Lineage Sorting and Introgression to Refine Species-Tree Estimates for Lake Tanganyika Cichlid Fishes.

    PubMed

    Meyer, Britta S; Matschiner, Michael; Salzburger, Walter

    2017-07-01

    Adaptive radiation is thought to be responsible for the evolution of a great portion of the past and present diversity of life. Instances of adaptive radiation, characterized by the rapid emergence of an array of species as a consequence to their adaptation to distinct ecological niches, are important study systems in evolutionary biology. However, because of the rapid lineage formation in these groups, and occasional gene flow between the participating species, it is often difficult to reconstruct the phylogenetic history of species that underwent an adaptive radiation. In this study, we present a novel approach for species-tree estimation in rapidly diversifying lineages, where introgression is known to occur, and apply it to a multimarker data set containing up to 16 specimens per species for a set of 45 species of East African cichlid fishes (522 individuals in total), with a main focus on the cichlid species flock of Lake Tanganyika. We first identified, using age distributions of most recent common ancestors in individual gene trees, those lineages in our data set that show strong signatures of past introgression. This led us to formulate three hypotheses of introgression between different lineages of Tanganyika cichlids: the ancestor of Boulengerochromini (or of Boulengerochromini and Bathybatini) received genomic material from the derived H-lineage; the common ancestor of Cyprichromini and Perissodini experienced, in turn, introgression from Boulengerochromini and/or Bathybatini; and the Lake Tanganyika Haplochromini and closely related riverine lineages received genetic material from Cyphotilapiini. We then applied the multispecies coalescent model to estimate the species tree of Lake Tanganyika cichlids, but excluded the lineages involved in these introgression events, as the multispecies coalescent model does not incorporate introgression. This resulted in a robust species tree, in which the Lamprologini were placed as sister lineage to the H

  19. Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

    USGS Publications Warehouse

    Odigie, Kingsley; Cohen, A.D.; Swarzenski, Peter W.; Flegal, R

    2014-01-01

    Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p < 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r = 0.82–0.98, p < 0.01, n = 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF < 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite of the development of mining and smelting operations within the lake’s watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions

  20. Ostracode trace metal geochemistry from Lake Tanganyika, Africa: Towards the development of a lacustrine paleothermometer

    NASA Astrophysics Data System (ADS)

    Ash, J.; Cohen, A. S.; Reiners, P. W.; Dettman, D. L.

    2011-12-01

    The development of quantitative lacustrine paleotemperature records is critical to understanding how past climate changes influenced the ecology and hydrology of lakes. Whereas paleoecological transfer functions, TEX-86 and clumped isotopes are all widely applied methods, all have their limitations. We aim to further the development of an alternative method with wider applications: ostracode trace metal geochemistry. Trace element compositions of ostracode valves reflect discriminatory element uptake that in turn reflect ambient environmental conditions and have previously shown promise for quantitative paleotemperature determination. Understanding the specific environmental controls on element concentrations and ratios is an area of active research with much attention focusing on Mg/Ca and Sr/Ca ratios and their relationships with temperature and salinity. Here, HR-ICP-MS geochemical analyses of ostracode valves are compared to an existing TEX-86 temperature record as well as gastropod stable isotopes from Lake Tanganyika, Africa. Two ostracode species (M. opaca and R. ampla) were chosen for analyses from core LT-98-58 (1759 +/- 133 AD-modern). Molar Mg/Ca ratios for M. opaca range from .04 to .16, and a trend towards increased Mg/Ca begins around 1880 AD. Molar Mg/Ca ratios for R. ampla range from .05 to .2, and no trend is discernable. Sr/Ca ratios in both species range from .003-.006 and remain relatively stable, indicating that changes in Mg/Ca are the result of temperature rather than salinity. The M. opaca Mg/Ca record closely resembles the existing TEX-86 paleotemperature record of Tierney et al. (2010) for the past ~240 yr. We intend these preliminary results to facilitate the future research and use of ostracode trace metal geochemistry in a wide range of lakes for paleotemperature reconstruction.

  1. Mapping landslide processes in the North Tanganyika - Lake Kivu rift zones: towards a regional hazard assessment

    NASA Astrophysics Data System (ADS)

    Dewitte, Olivier; Monsieurs, Elise; Jacobs, Liesbet; Basimike, Joseph; Delvaux, Damien; Draida, Salah; Hamenyimana, Jean-Baptiste; Havenith, Hans-Balder; Kubwimana, Désiré; Maki Mateso, Jean-Claude; Michellier, Caroline; Nahimana, Louis; Ndayisenga, Aloys; Ngenzebuhoro, Pierre-Claver; Nkurunziza, Pascal; Nshokano, Jean-Robert; Sindayihebura, Bernard; Philippe, Trefois; Turimumahoro, Denis; Kervyn, François

    2015-04-01

    The mountainous environments of the North Tanganyika - Lake Kivu rift zones are part of the West branch of the East African Rift. In this area, natural triggering and environmental factors such as heavy rainfalls, earthquake occurrences and steep topographies favour the concentration of mass movement processes. In addition anthropogenic factors such as rapid land use changes and urban expansion increase the sensibility to slope instability. Until very recently few landslide data was available for the area. Now, through the initiation of several research projects and the setting-up of a methodology for data collection adapted to this data-poor environment, it becomes possible to draw a first regional picture of the landslide hazard. Landslides include a wide range of ground movements such as rock falls, deep failure of slopes and shallow debris flows. Landslides are possibly the most important geohazard in the region in terms of recurring impact on the populations, causing fatalities every year. Many landslides are observed each year in the whole region, and their occurrence is clearly linked to complex topographic, lithological and vegetation signatures coupled with heavy rainfall events, which is the main triggering factor. Here we present the current knowledge of the various slope processes present in these equatorial environments. A particular attention is given to urban areas such as Bukavu and Bujumbura where landslide threat is particularly acute. Results and research perspectives on landslide inventorying, monitoring, and susceptibility and hazard assessment are presented.

  2. A new diminutive genus and species of catfish from Lake Tanganyika (Siluriformes: Clariidae).

    PubMed

    Wright, J J

    2017-09-01

    The examination of material representing one of Lake Tanganyika's six previously recognized endemic catfish lineages, has revealed the presence of an additional genus of clariid, described here as Pseudotanganikallabes new genus. This genus is represented by a single species, Pseudotanganikallabes prognatha sp. nov., which is distinguished from all other clariids by its lack of an infraorbital series, the presence of multiple osseous connections between the swim bladder capsules and elements of the neurocranium, the absence of an ethmoid notch, the presence of a very large, egg-shaped occipital fontanelle and the extension of the lower lip beyond the margin of the upper jaw. A combination of additional external and molecular characters serves to further distinguish this taxon from all currently recognized clariid species. Phylogenetic analysis of mitochondrial (cytb) and nuclear (18S-ITS1-5.8S-ITS2-28S) sequence data supports the creation of a new genus for this species, as it appears to represent an independent, monophyletic lineage within the family Clariidae. © 2017 The Fisheries Society of the British Isles.

  3. Body size evolution of a shell-brooding cichlid fish from Lake Tanganyika.

    PubMed

    Takahashi, T; Ota, K

    2016-12-01

    The substrate-brooding cichlid fish Telmatochromis temporalis in Lake Tanganyika demonstrates a simple example of ecological speciation between normal and dwarf morphs through divergent natural selection on body size. The dwarf morph most likely evolved from the ancestral normal morph; therefore, elucidating the evolution of its small body size is a key to understanding this ecological speciation event. Previous studies suggest that the small body size of the dwarf morph is an adaptation to the use of empty snail shells as shelters (males) and spawning sites (females), but this idea has not been fully evaluated. Combining original and previously published information, this study compared likelihood values to determine the primary factor that would be responsible for regulating the body size of the dwarf morph. Male body size is most likely regulated by the ability to turn within shells, which may influence the predation avoidance of adult fish. Females are smaller than males, and their body size is most likely regulated by the ability to lay eggs in the small spaces within shells close to the shell apices where predation risk on eggs is lower. This study provides new evidence supporting the hypothesis that different natural selection factors affected body size of the different sexes of the dwarf morph, which has not been reported in other animal species. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

  4. Phenotypic integration of brain size and head morphology in Lake Tanganyika Cichlids.

    PubMed

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2014-03-04

    Phenotypic integration among different anatomical parts of the head is a common phenomenon across vertebrates. Interestingly, despite centuries of research into the factors that contribute to the existing variation in brain size among vertebrates, little is known about the role of phenotypic integration in brain size diversification. Here we used geometric morphometrics on the morphologically diverse Tanganyikan cichlids to investigate phenotypic integration across key morphological aspects of the head. Then, while taking the effect of shared ancestry into account, we tested if head shape was associated with brain size while controlling for the potentially confounding effect of feeding strategy. The shapes of the anterior and posterior parts of the head were strongly correlated, indicating that the head represents an integrated morphological unit in Lake Tanganyika cichlids. After controlling for phylogenetic non-independence, we also found evolutionary associations between head shape, brain size and feeding ecology. Geometric morphometrics and phylogenetic comparative analyses revealed that the anterior and posterior parts of the head are integrated, and that head morphology is associated with brain size and feeding ecology in Tanganyikan cichlid fishes. In light of previous results on mammals, our results suggest that the influence of phenotypic integration on brain diversification is a general process.

  5. Phenotypic integration of brain size and head morphology in Lake Tanganyika Cichlids

    PubMed Central

    2014-01-01

    Background Phenotypic integration among different anatomical parts of the head is a common phenomenon across vertebrates. Interestingly, despite centuries of research into the factors that contribute to the existing variation in brain size among vertebrates, little is known about the role of phenotypic integration in brain size diversification. Here we used geometric morphometrics on the morphologically diverse Tanganyikan cichlids to investigate phenotypic integration across key morphological aspects of the head. Then, while taking the effect of shared ancestry into account, we tested if head shape was associated with brain size while controlling for the potentially confounding effect of feeding strategy. Results The shapes of the anterior and posterior parts of the head were strongly correlated, indicating that the head represents an integrated morphological unit in Lake Tanganyika cichlids. After controlling for phylogenetic non-independence, we also found evolutionary associations between head shape, brain size and feeding ecology. Conclusions Geometric morphometrics and phylogenetic comparative analyses revealed that the anterior and posterior parts of the head are integrated, and that head morphology is associated with brain size and feeding ecology in Tanganyikan cichlid fishes. In light of previous results on mammals, our results suggest that the influence of phenotypic integration on brain diversification is a general process. PMID:24593160

  6. Reverse evolution in RH1 for adaptation of cichlids to water depth in Lake Tanganyika.

    PubMed

    Nagai, Haruka; Terai, Yohey; Sugawara, Tohru; Imai, Hiroo; Nishihara, Hidenori; Hori, Michio; Okada, Norihiro

    2011-06-01

    Reverse evolution is a widespread phenomenon in biology, but the genetic mechanism for the reversal of a genetic change for adaptation to the ancestral state is not known. Here, we report the first case of complete reverse evolution of two amino acids, serine and alanine, at a single position in RH1 opsin pigment for adaptation to water depth. We determined RH1 sequences of cichlid fishes from four tribes of Lake Tanganyika with different habitat depths. Most of the species were divided into two types: RH1 with 292A for species in shallow water or 292S for species in deep water. Both types were adapted to their ambient light environments as indicated by the absorption spectra of the RH1 pigments. Based on the RH1 locus tree and ecological data, we inferred the ancestral amino acids at position 292 and the distribution of the depth ranges (shallow or deep) of ancestral species of each tribe. According to these estimates, we identified two distinct parallel adaptive evolutions: The replacement A292S occurred at least four times for adaptation from shallow to deep water, and the opposite replacement S292A occurred three times for adaptation from deep to shallow water. The latter parallelism represents the complete reverse evolution from the derived to the ancestral state, following back adaptive mutation with reversal of the RH1 pigment function accompanied by reversal of the species habitat shift.

  7. Alternative male mating tactics of the substrate brooding cichlid Telmatochromis temporalis in Lake Tanganyika.

    PubMed

    Katoh, Rei; Munehara, Hiroyuki; Kohda, Masanori

    2005-05-01

    Telmatochromis temporalis is a bi-parental substrate brooding cichlid endemic to Lake Tanganyika. Paired males were always larger than their mates and had territories around nests against conspecific males. However, males smaller than the paired females were found in 18% of the nests. Here we report a reproductive tactic of these small males. The small males had as heavy gonads as paired males, and the gonad somatic index (GSI) of the small males was much higher than that of the latter. The examinations of the paternity and maternity using microsatellite-DNA as a genetic marker revealed that the small males were not genetically related to the pair members, and sired some young in 3 of 5 nests. These small males did not guard the broods, suggesting that they are likely to perform reproductive parasitism as sneakers. Paired males could not enter their spawning nests due to their large size, which made it difficult to chase out sneakers once they entered the nest. Some males as small as the sneakers were found outside the territories of paired males, and their gonads were quite small. Circumstantial evidence suggests that small males have two alternative investment patterns: investing in gonad to be sneakers, and investing in growth to probably be territorial males.

  8. Evolutionary associations between host traits and parasite load: insights from Lake Tanganyika cichlids.

    PubMed

    Hayward, A; Tsuboi, M; Owusu, C; Kotrschal, A; Buechel, S D; Zidar, J; Cornwallis, C K; Løvlie, H; Kolm, N

    2017-02-10

    Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host-parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.

  9. High-Resolution Geochemical and Paleoecological Records of Climate Change Since the Late Glacial at Lake Tanganyika, East Africa

    NASA Astrophysics Data System (ADS)

    Alin, S. R.; Cohen, A. S.

    2002-12-01

    We used high-resolution geochemical and paleoecological records from shallow-water sediment cores to refine previous descriptions of climatic conditions at Lake Tanganyika, East Africa, for the period from the Late Glacial to the present. Radiocarbon and 210Pb dating were used to establish chronologies for the cores. Sedimentological changes indicate that lake level has risen approximately 50-70 m since the Late Glacial. A depositional hiatus occurred between 6.4 and 11.4 ka BP (all dates in calendar years) in several of the shallow-water cores. Elemental abundance (%C, %N) and stable isotopic (δ15N, δ13C) data for one core suggest that substantial changes in primary productivity and nutrient recycling regimes have occurred since 6.4 ka BP. Carbonate and ostracode crustacean preservation were low and nil, respectively, prior to 2.4 ka BP. Generally, these data support previous interpretations of regional paleoclimate and lake conditions, with wet and warm conditions during the interval from 6.4 to 4.0 ka, and increasingly arid conditions since 2.4 ka. However, for the interval from 4.0 to 2.4 ka, paleoenvironmental indicators (δ15N, reduced carbonate and ostracode preservation) suggest that the central part of Lake Tanganyika was stably stratified at a shallower depth than present as a result of diminished southerly trade winds. After 2.4 ka BP, sedimentary carbonate concentrations increase, and δ13C values become enriched, suggesting that lacustrine productivity increased with the resumption of deeper wind-driven mixing, lasting until 1 ka BP. For post-2.4 ka samples, species abundance data for ostracodes were used to generate an ostracode water depth index (OWDI). OWDI indicated that severe drought conditions were persistent or recurred at Lake Tanganyika between 1550 and 1850 A.D. Droughts resulted in marked lowstands at Lake Tanganyika at 1580+/-15 A.D., 1730+/-35 A.D., and 1800+/-30 A.D. These data contribute new information on the timing of Little Ice Age

  10. A molecular perspective on Late Quaternary climate and vegetation change in the Lake Tanganyika basin, East Africa

    NASA Astrophysics Data System (ADS)

    Tierney, Jessica E.; Russell, James M.; Huang, Yongsong

    2010-03-01

    Characterizing the nature of past hydrological change and its interactions with vegetation is fundamental to acquiring a better understanding of continental tropical climate dynamics. Here, we outline major shifts in the climate and ecosystem of tropical East Africa for the past 60,000 years (60 ka) by examining molecular records of hydrology, vegetation, and temperature from a sediment sequence from Lake Tanganyika. We demonstrate, via comparison with pollen spectra, that stable carbon isotopes measured on higher plant leaf waxes ( δ13C wax) are a reliable proxy for vegetation change. In addition we argue that the D/H ratio of higher plant leaf waxes ( δD wax) is a robust and independent indicator of past changes in aridity, and is not affected by regional vegetation change directly. Our paired, compound-specific isotope data show that shifts in vegetation lead major changes in hydrology in the Tanganyika basin at several major climate transitions during the past 60,000 years, suggesting that vegetation in the Tanganyika basin is not as sensitive to aridity as previous studies have suggested and that variations in carbon dioxide, temperature, and internal ecosystem dynamics are equally, if not more, important. We hypothesize that regional vegetation change may exert a positive feedback on regional hydrology, thus partially accounting for the abrupt threshold behavior evident in our paleohydrological data. Furthermore, we find that past changes in Tanganyika basin climate and ecology are closely linked to concentrations of atmospheric trace gases, highlighting the paramount influence of global climatic shifts upon regional tropical climate over glacial/interglacial timescales.

  11. Rapid radiation, ancient incomplete lineage sorting and ancient hybridization in the endemic Lake Tanganyika cichlid tribe Tropheini.

    PubMed

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

    2010-04-01

    The evolutionary history of the endemic Lake Tanganyika cichlid tribe Tropheini, the sister group of the species flocks of Lake Malawi and the Lake Victoria region, was reconstructed from 2009 bp DNA sequence of two mitochondrial genes (ND2 and control region) and from 1293 AFLP markers. A period of rapid cladogenesis at the onset of the diversification of the Tropheini produced a multitude of specialized, predominantly rock-dwelling aufwuchs-feeders that now dominate in Lake Tanganyika's shallow habitat. Nested within the stenotopic rock-dwellers is a monophyletic group of species, which also utilize more sediment-rich habitat. Most of the extant species date back to at least 0.7 million years ago. Several instances of disagreement between AFLP and mtDNA tree topology are attributed to ancient incomplete lineage sorting, introgression and hybridization. A large degree of correspondence between AFLP clustering and trophic types indicated fewer cases of parallel evolution of trophic ecomorphology than previously inferred from mitochondrial data. (c) 2009 Elsevier Inc. All rights reserved.

  12. A 60,000-yr record of climate in Southeast Tropical Africa: Preliminary results from Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Tierney, J.; Russell, J.

    2006-12-01

    Few paleoclimate records exist that record high-frequency climate variability within tropical Africa, particularly during Marine Isotope Stage 3 (30-60,000 years BP). Thus very little is known about the potential role or response the region may have with regards to high-latitude abrupt climate change. However, climate variability in tropical East Africa is linked to large-scale changes in the convective intensity and location of the inter- tropical convergence zone (ITCZ) and the strength of the seasonal monsoonal winds from both the Atlantic and Indian Oceans. Understanding tropical African climate history may illuminate the causes and amplifying mechanisms of global climate change. We present here a multiproxy record of 60,000 years of climate variability from the sediments of Lake Tanganyika, southeast tropical Africa, which addresses outstanding questions regarding the role of East Africa in the context of abrupt climate change. Continuously accumulating hemipelagic sediments recovered from 650 m water depth from the southern half of Lake Tanganyika record hydrologic variability, terrestrial paleoenvironments, and changes in wind-driven upwelling intensity. Major element variations in Tanganyika sediments measured at 1 mm resolution by scanning XRF resolve changes in sediment geochemistry over decadal to centennial timescales, shedding light on the amplitude and frequency of short-term climate variability in this region. Additionally, records of bulk stable isotopes (δ13C, δ15N), compound- specific δD, and biogenic silica indicate rapid, dramatic changes in lake productivity, vegetation, and rainfall over millennial time-scales from Marine Isotope Stage 3 to present, including the Younger Dryas. In the case of the latter, the Younger Dryas is manifest in Lake Tanganyika as a sedimentary sequence of low diatom content, indicating reductions in southerly monsoonal windspeed and lake upwelling, and hydrogen isotope data over this interval indicate significant

  13. Colour-assortative mating among populations of Tropheus moorii, a cichlid fish from Lake Tanganyika, East Africa.

    PubMed

    Salzburger, Walter; Niederstätter, Harald; Brandstätter, Anita; Berger, Burkhard; Parson, Walther; Snoeks, Jos; Sturmbauer, Christian

    2006-02-07

    The species flocks of cichlid fishes in the East African Lakes Tanganyika, Malawi and Victoria are prime examples of adaptive radiation and explosive speciation. Several hundreds of endemic species have evolved in each of the lakes over the past several thousands to a few millions years. Sexual selection via colour-assortative mating has often been proposed as a probable causal factor for initiating and maintaining reproductive isolation. Here, we report the consequences of human-mediated admixis among differentially coloured populations of the endemic cichlid fish Tropheus moorii from several localities that have accidentally been put in sympatry in a small harbour bay in the very south of Lake Tanganyika. We analysed the phenotypes (coloration) and genotypes (mitochondrial control region and five microsatellite loci) of almost 500 individuals, sampled over 3 consecutive years. Maximum-likelihood-based parenthood analyses and Bayesian inference of population structure revealed that significantly more juveniles are the product of within-colour-morph matings than could be expected under the assumption of random mating. Our results clearly indicate a marked degree of assortative mating with respect to the different colour morphs. Therefore, we postulate that sexual selection based on social interactions and female mate choice has played an important role in the formation and maintenance of the different colour morphs in Tropheus, and is probably common in other maternally mouthbrooding cichlids as well.

  14. Phylogenetic relationships of the Lake Tanganyika cichlid tribe Lamprologini: the story from mitochondrial DNA.

    PubMed

    Day, Julia J; Santini, Simona; Garcia-Moreno, Jaime

    2007-11-01

    The Lamprologini are the most species-rich and diverse tribe of Lake Tanganyika cichlids, comprising around 90 described species. We reconstruct the most complete ( approximately 70 species) mtDNA phylogeny to date for this tribe, based on NADH dehydrogenase subunit 2 (ND2 approximately 1047 bp) and the non-coding control region ( approximately 874 bp) and examine the degree to which mtDNA trees are good proxies for species trees. Phylogenetic relationships are assessed using Bayesian inference, maximum likelihood and maximum parsimony to determine the robustness of relationships. The resulting topologies are largely congruent and only the tree produced by an unpartitioned BI analysis is rejected using the non-parametric likelihood-based AU test. The trees are remarkably balanced, with two major clades consistently recovered in all analyses and with reasonable support. A smaller clade of deep-water species is also recovered. Overall support is good, when compared to some groups that have undergone adaptive radiation and rapid lineage formation. The much-expanded phylogeny of the group helps resolve the placement of some previously problematic taxa, such as Neolamprologus moori, highlighting the importance of greater taxonomic sampling. The results include a number of divergent placements of closely related species, and the following genera Neolamprologus, Lamprologus, Julidiochromis, Telmatochromis are not monophyletic, with alternative hypotheses consistent with traditional taxonomy providing a significantly worse fit to the data. We find several examples of divergent mtDNA taxa sequences of presumed closely related species. This could be due to incorrect taxonomy or to the failure of the mtDNA to reflect species relationships and may support the hypothesis that speciation within this group has been facilitated by introgressive hybridisation.

  15. Genomics of speciation and introgression in Princess cichlid fishes from Lake Tanganyika.

    PubMed

    Gante, Hugo F; Matschiner, Michael; Malmstrøm, Martin; Jakobsen, Kjetill S; Jentoft, Sissel; Salzburger, Walter

    2016-12-01

    How variation in the genome translates into biological diversity and new species originate has endured as the mystery of mysteries in evolutionary biology. African cichlid fishes are prime model systems to address speciation-related questions for their remarkable taxonomic and phenotypic diversity, and the possible role of gene flow in this process. Here, we capitalize on genome sequencing and phylogenomic analyses to address the relative impacts of incomplete lineage sorting, introgression and hybrid speciation in the Neolamprologus savoryi-complex (the 'Princess cichlids') from Lake Tanganyika. We present a time-calibrated species tree based on whole-genome sequences and provide strong evidence for incomplete lineage sorting in the early phases of diversification and multiple introgression events affecting different stages. Importantly, we find that the Neolamprologus chromosomes show centre-to-periphery biases in nucleotide diversity, sequence divergence, GC content, incomplete lineage sorting and rates of introgression, which are likely modulated by recombination density and linked selection. The detection of heterogeneous genomic landscapes has strong implications on the genomic mechanisms involved in speciation. Collinear chromosomal regions can be protected from gene flow and harbour incompatibility genes if they reside in lowly recombining regions, and coupling can evolve between nonphysically linked genomic regions (chromosome centres in particular). Simultaneously, higher recombination towards chromosome peripheries makes these more dynamic, evolvable regions where adaptation polymorphisms have a fertile ground. Hence, differences in genome architecture could explain the levels of taxonomic and phenotypic diversity seen in taxa with collinear genomes and might have contributed to the spectacular cichlid diversity observed today. © 2016 John Wiley & Sons Ltd.

  16. Evolution of body shape in sympatric versus non-sympatric Tropheus populations of Lake Tanganyika.

    PubMed

    Kerschbaumer, M; Mitteroecker, P; Sturmbauer, C

    2014-02-01

    Allopatric speciation often yields ecologically equivalent sister species, so that their secondary admixis enforces competition. The shores of Lake Tanganyika harbor about 120 distinct populations of the cichlid genus Tropheus, but only some are sympatric. When alone, Tropheus occupies a relatively broad depth zone, but in sympatry, fish segregate by depth. To assess the effects of competition, we studied the partial co-occurrence of Tropheus moorii 'Kaiser' and 'Kirschfleck' with Tropheus polli. A previous study demonstrated via standardized breeding experiments that some observed differences between Tropheus 'Kaiser' living alone and in sympatry with T. polli have a genetic basis despite large-scale phenotypic plasticity. Using geometric morphometrics and neutral genetic markers, we now investigated whether sympatric populations differ consistently in body shape from populations living alone and if the differences are adaptive. We found significant differences in mean shape between non-sympatric and sympatric populations, whereas all sympatric populations of both color morphs clustered together in shape space. Sympatric populations had a relatively smaller head, smaller eyes and a more anterior insertion of the pectoral fin than non-sympatric populations. Genetically, however, non-sympatric and sympatric 'Kaiser' populations clustered together to the exclusion of 'Kirschfleck'. Genetic distances, but not morphological distances, were correlated with geographic distances. Within- and between-population covariance matrices for T. moorii populations deviated from proportionality. It is thus likely that natural selection acts on both phenotypic plasticity and heritable traits and that both factors contribute to the observed shape differences. The consistency of the pattern in five populations suggests ecological character displacement.

  17. Evolution of body shape in sympatric versus non-sympatric Tropheus populations of Lake Tanganyika

    PubMed Central

    Kerschbaumer, M; Mitteroecker, P; Sturmbauer, C

    2014-01-01

    Allopatric speciation often yields ecologically equivalent sister species, so that their secondary admixis enforces competition. The shores of Lake Tanganyika harbor about 120 distinct populations of the cichlid genus Tropheus, but only some are sympatric. When alone, Tropheus occupies a relatively broad depth zone, but in sympatry, fish segregate by depth. To assess the effects of competition, we studied the partial co-occurrence of Tropheus moorii ‘Kaiser' and ‘Kirschfleck' with Tropheus polli. A previous study demonstrated via standardized breeding experiments that some observed differences between Tropheus ‘Kaiser' living alone and in sympatry with T. polli have a genetic basis despite large-scale phenotypic plasticity. Using geometric morphometrics and neutral genetic markers, we now investigated whether sympatric populations differ consistently in body shape from populations living alone and if the differences are adaptive. We found significant differences in mean shape between non-sympatric and sympatric populations, whereas all sympatric populations of both color morphs clustered together in shape space. Sympatric populations had a relatively smaller head, smaller eyes and a more anterior insertion of the pectoral fin than non-sympatric populations. Genetically, however, non-sympatric and sympatric ‘Kaiser' populations clustered together to the exclusion of ‘Kirschfleck'. Genetic distances, but not morphological distances, were correlated with geographic distances. Within- and between-population covariance matrices for T. moorii populations deviated from proportionality. It is thus likely that natural selection acts on both phenotypic plasticity and heritable traits and that both factors contribute to the observed shape differences. The consistency of the pattern in five populations suggests ecological character displacement. PMID:24065182

  18. Contrasting parasite communities among allopatric colour morphs of the Lake Tanganyika cichlid Tropheus

    PubMed Central

    2013-01-01

    Background Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs. Results Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic

  19. Contrasting parasite communities among allopatric colour morphs of the Lake Tanganyika cichlid Tropheus.

    PubMed

    Raeymaekers, Joost A M; Hablützel, Pascal I; Grégoir, Arnout F; Bamps, Jolien; Roose, Anna K; Vanhove, Maarten P M; Van Steenberge, Maarten; Pariselle, Antoine; Huyse, Tine; Snoeks, Jos; Volckaert, Filip A M

    2013-02-14

    Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs. Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic differentiation were

  20. Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems

    PubMed Central

    Gergurich, Elizabeth L.; Kraemer, Benjamin M.; McGlue, Michael M.; McIntyre, Peter B.; Russell, James M.; Simmons, Jack D.; Swarzenski, Peter W.

    2016-01-01

    Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a ∼1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa’s deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last ∼150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last ∼500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika’s extraordinary biodiversity and ecosystem services. PMID:27503877

  1. Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems

    USGS Publications Warehouse

    Cohen, Andrew S.; Gergurich, Elizabeth L.; Kraemer, Benjamin M.; McGlue, Michael M.; McIntyre, Peter B.; Russell, James M.; Simmons, Jack D.; Swarzenski, Peter W.

    2016-01-01

    Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a ∼1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa’s deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last ∼150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last ∼500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika’s extraordinary biodiversity and ecosystem services.

  2. Early-stage rifting in the southwest East African Rift: Insights from new reflection seismic data from Lakes Tanganyika and Malawi (Nyasa)

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.; Wood, D. A.; Shillington, D. J.; McCartney, T.; Accardo, N. J.

    2015-12-01

    The western branch of the East African Rift is characterized by modest amounts of mainly amagmatic extension; deeply-subsided, fault-controlled basins; and large-magnitude, deep seismicity. Lakes Tanganyika and Malawi are two of the world's largest lakes, with maximum water depths of 1450 and 700 m respectively. Newly acquired seismic reflection data, along with newly reprocessed legacy data reveal thick sedimentary sections, in excess of 5 km in some localities. The 1980's vintage legacy data from Project PROBE have been reprocessed through pre-stack depth migration in Lake Tanganyika, and similar reprocessing of legacy data from Lake Malawi is forthcoming. New high-fold and large-source commercial and academic data have recently been collected in southern Lake Tanganyika, and in the northern and central basins of Lake Malawi as part of the 2015 SEGMeNT project. In the case of Lake Tanganyika, new data indicate the presence of older sediment packages that underlie previously identified "pre-rift" basement (the "Nyanja Event"). These episodes of sedimentation and extension may substantially predate the modern lake. These deep stratal reflections are absent in many localites, possibly on account of attenuation of the acoustic signal. However in one area of southern Lake Tanganyika, the newly-observed deep strata extend axially for ~70 km, likely representing deposits from a discrete paleolake. The high-amplitude Nyanja Event is interpreted as the onset of late-Cenozoic rifting, and the changing character of the overlying depositional sequences reflects increasing relief in the rift valley, as well as the variability of fluvial inputs, and the intermittent connectivity of upstream lake catchments. Earlier Tanganyika sequences are dominated by shallow lake and fluvial-lacustrine facies, whereas later sequences are characterized by extensive gravity flow deposition in deep water, and pronounced erosion and incision in shallow water depths and on littoral platforms. The

  3. Evolutionary history of the Lake Tanganyika cichlid tribe Lamprologini (Teleostei: Perciformes) derived from mitochondrial and nuclear DNA data.

    PubMed

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

    2010-10-01

    Lake Tanganyika comprises a cichlid species flock with substrate-breeding and mouthbrooding lineages. While sexual selection via mate choice on male mating color is thought to boost speciation rates in mouthbrooding cichlids, this is not the case in substrate-breeding lamprologines, which mostly form stable pairs and lack sexual dichromatism. We present a comprehensive reconstruction of the evolution of the cichlid tribe Lamprologini, based upon mtDNA sequences and multilocus nuclear DNA (AFLP) markers. Twelve mtDNA clades were identified, seven of which were corroborated by the AFLP tree. The radiation is likely to have started about 5.3 MYA, contemporarily with that of the mouthbrooding C-lineage, and probably triggered by the onset of deep-water conditions in Lake Tanganyika. Neither the Congo- nor the Malagarazi River species form the most ancestral branch. Several conflicts in the mtDNA phylogeny with taxonomic assignments based upon color, eco-morphology and behavior could be resolved and complemented by the AFLP analysis. Introgressive hybridization upon secondary contact seems to be the most likely cause for paraphyly of taxa due to mtDNA capture in species involving brood-care helpers, while accidental hybridization best explains the para- or polyphyly of several gastropod shell breeders. Taxonomic error or paraphyly due to the survival of ancestral lineages appear responsible for inconsistencies in the genera Lamprologus and Neolamprologus. Copyright 2010 Elsevier Inc. All rights reserved.

  4. Evolutionary history of the Lake Tanganyika cichlid tribe Lamprologini (Teleostei: Perciformes) derived from mitochondrial and nuclear DNA data

    PubMed Central

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

    2010-01-01

    Lake Tanganyika comprises a cichlid species flock with substrate-breeding and mouthbrooding lineages. While sexual selection via mate choice on male mating color is thought to boost speciation rates in mouthbrooding cichlids, this is not the case in substrate-breeding lamprologines, which mostly form stable pairs and lack sexual dichromatism. We present a comprehensive reconstruction of the evolution of the cichlid tribe Lamprologini, based upon mtDNA sequences and multilocus nuclear DNA (AFLP) markers. Twelve mtDNA clades were identified, seven of which were corroborated by the AFLP tree. The radiation is likely to have started about 5.3 MYA, contemporarily with that of the mouthbrooding C-lineage, and probably triggered by the onset of deep-water conditions in Lake Tanganyika. Neither the Congo- nor the Malagarazi River species form the most ancestral branch. Several conflicts in the mtDNA phylogeny with taxonomic assignments based upon color, eco-morphology and behavior could be resolved and complemented by the AFLP analysis. Introgressive hybridization upon secondary contact seems to be the most likely cause for paraphyly of taxa due to mtDNA capture in species involving brood-care helpers, while accidental hybridization best explains the para- or polyphyly of several gastropod shell breeders. Taxonomic error or paraphyly due to the survival of ancestral lineages appear responsible for inconsistencies in the genera Lamprologus and Neolamprologus. PMID:20601006

  5. Ancyrocephalidae (Monogenea) of Lake Tanganyika: III: Cichlidogyrus infecting the world's biggest cichlid and the non-endemic tribes Haplochromini, Oreochromini and Tylochromini (Teleostei, Cichlidae).

    PubMed

    Muterezi Bukinga, Fidel; Vanhove, Maarten P M; Van Steenberge, Maarten; Pariselle, Antoine

    2012-11-01

    Lake Tanganyika is the deepest and oldest African Great Lake and of economic importance. While the diversity of its endemic cichlid radiations yielded scientific interest, a number of cichlid tribes have few representatives in the lake. Some of those, namely Oreochromini (ex-Tilapiini), Haplochromini and Tylochromini, reach higher species numbers in riverine systems. Conversely, the phylogenetic position of the monospecific and endemic Boulengerochromini is unclear. The oreochromines Oreochromis tanganicae and Oreochromis niloticus, the haplochromine Astatotilapia burtoni, the tylochromine Tylochromis polylepis and the boulengerochromine Boulengerochromis microlepis, the largest cichlid species worldwide, were surveyed for ancyrocephalid monogenean gill parasites. Five new species are proposed. Cichlidogyrus gillardinae sp. n. is described from A. burtoni, Cichlidogyrus mbirizei sp. n. from O. tanganicae and Cichlidogyrus nshomboi sp. n. from B. microlepis. T. polylepis harbours Cichlidogyrus mulimbwai sp. n., Cichlidogyrus muzumanii sp. n. and a third, presently undescribed species. Four species known from outside the Tanganyika Basin were retrieved on the oreochromines. The host species are scientific models or important in the sectors of fisheries or ornamental fish trade. Moreover, their phylogenetic positions render them well-suited to help elucidate the historic relationships between riverine and lacustrine African cichlids. In this framework, their Cichlidogyrus fauna is compared to congeners known from African rivers and to the few Tanganyika representatives described. While the parasites of Oreochromis, A. burtoni and T. polylepis are reminiscent of those infecting related hosts throughout Africa, B. microlepis hosts a Cichlidogyrus morphotype typical of Lake Tanganyika. This supports its placement within an endemic cichlid radiation.

  6. [Distribution and Potential Ecological Risk Assessment of Heavy Metals in Surface Sediments of Inflow Rivers to Northeastern Lake Tanganyika].

    PubMed

    Yu, Cheng; Chen, Shuang; Zhang, Lu

    2016-02-15

    As the second deepest lake in Africa, Lake Tanganyika plays an important role in supplying fish protein for citizens in the catchment. However, the lake is increasingly threatened by environmental pollution with the development of social economy and expanding of population. In order to reveal the external source of heavy metals in Lake Tanganyika, 16 surface sediment samples from the rivers which flow into the northeast of the lake were collected and analyzed. Besides the contents, the potential ecological risk indices (RI) of each heavy metal were also analyzed. Furthermore, the relationship, between land use and the spatial distribution of heavy metals was also discussed. The average contents of Cu, Zn, Cd, Pb and Hg were 18. 4, 21.2, 0.05, 6.6 mg x kg(-1) and 8.4 ng x g(-1), respectively, with the maximum values of Zn, Pb and Cd located in Bujumbura urban rivers. The data indicated that all the inflow rivers were at low potential ecological risk. RI of heavy metals ranked as the following order: Cd > Hg > Cu > Pb > Zn, as Cd being the key element contributing to the risk. The relationship between land use and heavy metals showed that the contents of heavy metals were highest in urban areas, followed by estuarine wetlands, and woodlands were least polluted by heavy metals. This distribution type implied that human activities could cause the heavy metal accumulation in the surface sediments of nearby rivers. The urban areas and estuarine wetlands need to be concerned in the further study.

  7. 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

  8. Depth segregation and diet disparity revealed by stable isotope analyses in sympatric herbivorous cichlids in Lake Tanganyika.

    PubMed

    Hata, Hiroki; Shibata, Jyunya; Omori, Koji; Kohda, Masanori; Hori, Michio

    2015-01-01

    Lake Tanganyika in the African Great Rift Valley is known as a site of adaptive radiation in cichlid fishes. Diverse herbivorous fishes coexist on a rocky littoral of the lake. Herbivorous cichlids have acquired multiple feeding ecomorphs, including grazer, browser, scraper, and scooper, and are segregated by dietary niche. Within each ecomorph, however, multiple species apparently coexist sympatrically on a rocky slope. Previous observations of their behavior show that these cichlid species inhabit discrete depths separated by only a few meters. In this paper, using carbon (C) and nitrogen (N) stable isotope ratios as markers, we followed the nutritional uptake of cichlid fishes from periphyton in their feeding territories at various depths. δ(15)N of fish muscles varied among cichlid ecomorphs; this was significantly lower in grazers than in browsers and scoopers, although δ(15)N levels in periphyton within territories did not differ among territorial species. This suggests that grazers depend more directly on primary production of periphyton, while others ingest animal matter from higher trophic levels. With respect to δ(13)C, only plankton eaters exhibited lower values, suggesting that these fishes depend on production of phytoplankton, while the others depend on production of periphyton. Irrespective of cichlid ecomorph, δ(13)C of periphyton correlated significantly with habitat depth, and decreased as habitat depth became deeper. δ(13)C in territorial fish muscles was significantly related to that of periphyton within their territories, regardless of cichlid ecomorph, which suggests that these herbivorous cichlids depend on primary production of periphyton within their territories. Carbon and nitrogen stable isotope ratios varied among ecomorphs and among cichlid species in the same ecomorphs sympatrically inhabiting a littoral area of Lake Tanganyika, suggesting that these cichlids are segregated by nutrient source due to varying dependency on

  9. Ionospheric plasma turbulence over region of 2006 Iran, 2005 Lake Tanganyika and 2010 New Britain Region earthquakes.

    NASA Astrophysics Data System (ADS)

    Kosciesza, Malgorzata; Blecki, Jan; Wronowski, Roman; Parrot, Michel

    2013-04-01

    We report the results of the observation of ELF plasma turbulence registered by DEMETER satellite in the ionosphere over epicenter region of three earthquakes. First one took place on 2nd of February 2005 in Lake Tanganyika Region with magnitude 6.9. Second was earthquake with magnitude 6.1 in Iran on 31st March 2006. The last one took place on 4th of August 2010 in New Britain Region with magnitude 7.0. Obtained results we compare with data gathered during corresponding time and region with quiet seismic conditions. To study this turbulent processes we apply Fourier, wavelet, bispectral analysis and statistical description with use of kurtosis and skewness of the electric field fluctuations. These registrations are correlated with the plasma parameters measured onboard DEMETER satellite and with geomagnetic indices.

  10. Deep-water parasite diversity in Lake Tanganyika: description of two new monogenean species from benthopelagic cichlid fishes.

    PubMed

    Kmentová, Nikol; Gelnar, Milan; Koblmüller, Stephan; Vanhove, Maarten P M

    2016-08-03

    Lake Tanganyika is the world's second deepest lake. Its diverse cichlid assemblage offers a unique opportunity for studying a deep-water host-parasite model in freshwater. Low host specificity and a broad host range including representatives of the Bathybatini tribe in the only monogenean parasite described from this habitat, Cichlidogyrus casuarinus Pariselle, Muterezi Bukinga & Vanhove, 2015 suggest a link between lower specificity and lower host density. Conversely, high host specificity and species richness are reported for monogeneans of the lake's littoral cichlids. We further investigated whether the deep-water environment in Lake Tanganyika is really monogenean species-depauperate by investigating the monogenean fauna of Trematocara unimaculatum (a representative of the tribe Trematocarini, the sister lineage of the Bathybatini) and Benthochromis horii, a member of the tribe Benthochromini, found in the same deep-water habitat as the already known hosts of C. casuarinus. Sclerotised structures of the collected monogenean individuals were characterised morphologically using light microscopy and morphometrics. Both examined cichlid species are infected by a single monogenean species each, which are new to science. They are described as Cichlidogyrus brunnensis n. sp., infecting T. unimaculatum, and Cichlidogyrus attenboroughi n. sp., parasitising on B. horii. Diagnostic characteristics include the distal bifurcation of the accessory piece in C. brunnensis n. sp. and the combination of long auricles and no heel in C. attenboroughi n. sp. In addition C. brunnensis n. sp. does not resemble C. casuarinus, the only species of Cichlidogyrus thus far reported from the Bathybatini. Also Cichlidogyrus attenboroughi n. sp. does not resemble any of the monogenean species documented from the pelagic zone of the lake and is among the few described species of Cichlidogyrus without heel. As two new and non-resembling Cichlidogyrus species are described from T. unimaculatum

  11. Additive genetic variance of quantitative traits in natural and pond-bred populations of the Lake Tanganyika cichlid Tropheus moorii.

    PubMed

    Koch, Martin; Wilson, Alastair J; Kerschbaumer, Michaela; Wiedl, Thomas; Sturmbauer, Christian

    Quantitative genetic studies in natural populations are of growing interest to speciation research since divergence is often believed to arise through micro-evolutionary change, caused by natural selection on functional morphological traits. The species flock of cichlid fishes in Africa's oldest lake, Lake Tanganyika, offers a rare opportunity to study this process. Using the cichlid species Tropheus moorii, we assessed the potential for microevolution in a set of morphological traits by estimating their quantitative genetic basis of variation. Two approaches were employed: (1) estimation of trait heritabilities (h(2)) in situ from a sample of wild caught fish, and (2) estimation of h(2) from first generation offspring produced in a semi-natural breeding experiment. In both cases, microsatellite data were used to infer pedigree structure among the sampled individuals and estimates of h(2) were made using an animal model approach. Although power was limited by the pedigree structures estimated (particularly in the wild caught sample), we nonetheless demonstrate the presence of significant additive genetic variance for aspects of morphology that, in the cichlid species Tropheus moorii, are expected to be functionally and ecologically important, and therefore likely targets of natural selection. We hypothesize that traits showing significant additive genetic variance, such as the mouth position have most likely played a key role in the adaptive evolution of the cichlid fish Tropheus moorii.

  12. Scientific Drilling at Lake Tanganyika, Africa: A Transformative Record for Understanding Evolution in Isolation and the Biological History of the African Continent, University of Basel, 6-8 June 2016

    NASA Astrophysics Data System (ADS)

    Cohen, Andrew S.; Salzburger, Walter

    2017-05-01

    We report on the outcomes of a workshop held to discuss evolutionary biology, paleobiology and paleoecology questions that could be addressed by a scientific drilling project at Lake Tanganyika, the largest, deepest and oldest of the African Rift Valley lakes. Lake Tanganyika is of special significance to evolutionary biologists as it harbors one of the most spectacular endemic faunas of any lake on earth, with hundreds of unique species of fish, molluscs, crustaceans and other organisms that have evolved over the lake's long history. Most of these groups of organisms are known from fossils in short cores from the lake, raising the possibility that both body fossil and ancient DNA records might be recovered from long drill cores. The lake's sedimentary record could also provide a record of African terrestrial ecosystem history since the late Miocene. This 3-day workshop brought together biological and geological specialists on the lake and its surroundings to prioritize paleobiological, ecological and microbiological objectives that could ultimately be incorporated into an overall drilling plan for Lake Tanganyika and to consider how biological objectives can effectively be integrated into the paleoclimate and tectonics objectives of a Lake Tanganyika drilling project already considered in prior workshops.

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

    PubMed

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

    2007-01-25

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

  14. Ancyrocephalidae (Monogenea) of Lake Tanganyika: II: description of the first Cichlidogyrus spp. parasites from Tropheini fish hosts (Teleostei, Cichlidae).

    PubMed

    Gillardin, Céline; Vanhove, Maarten P M; Pariselle, Antoine; Huyse, Tine; Volckaert, Filip A M

    2012-01-01

    Although Lake Tanganyika hosts the most diverse endemic cichlid fish assemblage, its monogenean parasite fauna has hardly been documented. The cichlid tribe Tropheini has generated great interest because of its systematic position within the Haplochromini s.l. and its diversity in trophic morphology, reproductive behaviour and population structure. It has the potential to host a diverse Monogenea fauna. Here, we describe the first Cichlidogyrus spp.: Cichlidogyrus steenbergei sp. n., Cichlidogyrus irenae sp. n. and Cichlidogyrus gistelincki sp. n. The three host species, Limnotilapia dardennii, Ctenochromis horei and Gnathochromis pfefferi, are all infected by a single unique Cichlidogyrus sp. The genital and haptoral structure of the new species suggests a close relationship, which might mirror the close affinities between the hosts within the Tropheini. Based on haptoral configuration, the new species belong to a morphological group within the genus containing parasites both of West African cichlids and of Haplochromini, and hence, do not represent a new organisation of the attachment organ (as has recently been described of congeners infecting the ectodine cichlid Ophthalmotilapia).

  15. Repeated parallel evolution of parental care strategies within Xenotilapia, a genus of cichlid fishes from Lake Tanganyika.

    PubMed

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

    2012-01-01

    The factors promoting the evolution of parental care strategies have been extensively studied in experiment and theory. However, most attempts to examine parental care in an evolutionary context have evaluated broad taxonomic categories. The explosive and recent diversifications of East African cichlid fishes offer exceptional opportunities to study the evolution of various life history traits based on species-level phylogenies. The Xenotilapia lineage within the endemic Lake Tanganyika cichlid tribe Ectodini comprises species that display either biparental or maternal only brood care and hence offers a unique opportunity to study the evolution of distinct parental care strategies in a phylogenetic framework. In order to reconstruct the evolutionary relationships among 16 species of this lineage we scored 2,478 Amplified Fragment Length Polymorphisms (AFLPs) across the genome. We find that the Ectodini genus Enantiopus is embedded within the genus Xenotilapia and that during 2.5 to 3 million years of evolution within the Xenotilapia clade there have been 3-5 transitions from maternal only to biparental care. While most previous models suggest that uniparental care (maternal or paternal) arose from biparental care, we conclude from our species-level analysis that the evolution of parental care strategies is not only remarkably fast, but much more labile than previously expected.

  16. Social status-dependent nest choice of territorial males under reproductive parasitism in a Lake Tanganyika cichlid Telmatochromis vittatus.

    PubMed

    Ota, K; Kohda, M

    2011-03-01

    Field and laboratory studies were conducted to examine how territorial males of a Lake Tanganyika cichlid Telmatochromis vittatus balance the conflicting demands on nest choice between occupying large nests with more females and avoiding reproductive parasitism (nest piracy, which is adopted by the largest males in the population). Pirates less frequently intruded the nests farther from neighbours, perhaps due to the costs associated with travelling between nests. The field experiment showed that territorial male T. vittatus sacrificed the fitness benefits that large nests offer and instead prioritized occupying the nests farther from neighbours on which fewer pirates intruded. The field observations suggested that they adopt different strategies for nest choice according to their relative competitive ability to pirates; the large territorial males, who are size-matched to pirates and can defend their nests against them, compete for larger nests among the more-isolated nests, whereas subordinate territorial males, which are smaller than pirates and thus inferior to them, compete for the more-isolated nests among the less-isolated nests. These findings suggest that the territorial male T. vittatus chooses the more-isolated nests to avoid pirate males at the expense of occupying large nests.

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

    PubMed Central

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

    2012-01-01

    The factors promoting the evolution of parental care strategies have been extensively studied in experiment and theory. However, most attempts to examine parental care in an evolutionary context have evaluated broad taxonomic categories. The explosive and recent diversifications of East African cichlid fishes offer exceptional opportunities to study the evolution of various life history traits based on species-level phylogenies. The Xenotilapia lineage within the endemic Lake Tanganyika cichlid tribe Ectodini comprises species that display either biparental or maternal only brood care and hence offers a unique opportunity to study the evolution of distinct parental care strategies in a phylogenetic framework. In order to reconstruct the evolutionary relationships among 16 species of this lineage we scored 2,478 Amplified Fragment Length Polymorphisms (AFLPs) across the genome. We find that the Ectodini genus Enantiopus is embedded within the genus Xenotilapia and that during 2.5 to 3 million years of evolution within the Xenotilapia clade there have been 3–5 transitions from maternal only to biparental care. While most previous models suggest that uniparental care (maternal or paternal) arose from biparental care, we conclude from our species-level analysis that the evolution of parental care strategies is not only remarkably fast, but much more labile than previously expected. PMID:22347454

  18. Acquisition of Lateralized Predation Behavior Associated with Development of Mouth Asymmetry in a Lake Tanganyika Scale-Eating Cichlid Fish.

    PubMed

    Takeuchi, Yuichi; Hori, Michio; Tada, Shinya; Oda, Yoichi

    2016-01-01

    The scale-eating cichlid Perissodus microlepis with asymmetric mouth is an attractive model of behavioral laterality: each adult tears off scales from prey fishes' left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioral laterality and mouth asymmetry, we analyzed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22 ≤ SL<115 mm) sampled in Lake Tanganyika. The shapes of the pored scales found in each specimen's stomach indicated its attack side preference. Early-juvenile specimens (SL<45 mm) feeding mainly on zooplankton exhibited slight but significant mouth asymmetry. As the fish acquired scale-eating (45 mm ≤ SL), attack side preference was gradually strengthened, as was mouth asymmetry. Among size-matched individuals, those with more skewed mouths ate more scales. These findings show that behavioral laterality in scale-eating P. microlepis is established in association with development of mouth asymmetry which precedes the behavioral acquisition, and that this synergistic interaction between physical and behavioral literalities may contribute to efficient scale-eating.

  19. Acquisition of Lateralized Predation Behavior Associated with Development of Mouth Asymmetry in a Lake Tanganyika Scale-Eating Cichlid Fish

    PubMed Central

    Takeuchi, Yuichi; Hori, Michio; Tada, Shinya; Oda, Yoichi

    2016-01-01

    The scale-eating cichlid Perissodus microlepis with asymmetric mouth is an attractive model of behavioral laterality: each adult tears off scales from prey fishes’ left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioral laterality and mouth asymmetry, we analyzed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22≤SL<115mm) sampled in Lake Tanganyika. The shapes of the pored scales found in each specimen’s stomach indicated its attack side preference. Early-juvenile specimens (SL<45mm) feeding mainly on zooplankton exhibited slight but significant mouth asymmetry. As the fish acquired scale-eating (45mm≤SL), attack side preference was gradually strengthened, as was mouth asymmetry. Among size-matched individuals, those with more skewed mouths ate more scales. These findings show that behavioral laterality in scale-eating P. microlepis is established in association with development of mouth asymmetry which precedes the behavioral acquisition, and that this synergistic interaction between physical and behavioral literalities may contribute to efficient scale-eating. PMID:26808293

  20. Comparative phylogenetic analyses of the adaptive radiation of Lake Tanganyika cichlid fish: nuclear sequences are less homoplasious but also less informative than mitochondrial DNA.

    PubMed

    Clabaut, Céline; Salzburger, Walter; Meyer, Axel

    2005-11-01

    Over 200 described endemic species make up the adaptive radiation of cichlids in Lake Tanganyika. This species assemblage has been viewed as both an evolutionary reservoir of old cichlid lineages and an evolutionary hotspot from which the modern cichlid lineages arose, seeding the adaptive radiations in Lakes Victoria and Malawi. Here we report on a phylogenetic analysis of Lake Tanganyika cichlids combining the previously determined sequences of the mitochondrial ND2 gene (1047 bp) with newly derived sequences of the nuclear RAG1 gene (approximately 700 bp of intron 2 and approximately 1100 bp of exon 3). The nuclear data-in agreement with mitochondrial DNA-suggest that Lake Tanganyika harbors several ancient lineages that did not undergo rampant speciation (e.g., Bathybatini, Trematocarini). We find strong support for the monophyly of the most species-rich Tanganyikan group, the Lamprologini, and we propose a new taxonomic group that we term the C-lineage. The Haplochromini and Tropheini both have an 11-bp deletion in the intron of RAG1, strongly supporting the monophyly of this clade and its derived position. Mapping the phylogenetically informative positions revealed that, for certain branches, there are six times fewer apomorphies in RAG1. However, the consistency index of these positions is higher compared to the mitochondrial ND2 gene. Nuclear data therefore provide, on a per-base pair basis, less but more reliable phylogenetic information. Even if in our case RAG1 has not provided as much phylogenetic information as we expected, we suggest that this marker might be useful in the resolution of the phylogeny of older groups.

  1. Evolutionary relationships of the limnochromini, a tribe of benthic deepwater cichlid fish endemic to Lake Tanganyika, East Africa.

    PubMed

    Duftner, Nina; Koblmüller, Stephan; Sturmbauer, Christian

    2005-03-01

    Lake Tanganyika harbors an enormous diversity of cichlid fish that stem from eight distinct ancestral lineages, which colonized the lake after its formation 9 to 12 million years ago. Six of twelve currently described tribes are assigned to the "H-lineage," an assemblage of exclusively mouthbrood-ing cichlids, all of which evolved during a short period of time during the course of the primary radiation of lacustrine species. Our study focuses on the deepwater tribe Limnochromini, comprising bi-parental mouthbrooders, and is based on phylogenetic analysis of two mitochondrial gene segments. We confirm the polyphyletic origin of the Limnochromini as they are defined to date, in that Gnathochromis pfefferi is placed among the Tropheini, whereas the genus Benthochromis is presented as an independent lineage. The remaining nine species were unambiguously resolved as monophyletic and should be redefined as the tribe Limnochromini. Concerning generic assignments, the genus Greenwoodochromis appeared as monophyletic, Limnochromis as paraphyletic, and the genera Reganochromis and Baileychromis as monophyletic sister genera. The linearized tree analysis and the comparison of average sequence divergences to that of the remaining tribes of the H-lineage revealed a relatively recent but simultaneous proliferation of the Limnochromini, suggesting that the same environmental changes triggered the radiation of particular deepwater, benthic, pelagic, and littoral lineages. By using a preliminary calibration of a molecular clock based on gamma-corrected amino acid distances of the NADH2 gene, the diversification of the Limnochromini could tentatively be dated to 2.9-3.5 MYA, coinciding with a period of aridification in East Africa between 2.5 and 3 MYA. The lack of geographic color morphs and the structural uniformity and resource scarcity of deepwater habitats suggest that competition and resource partitioning leading to differential trophic specialization promoted speciation

  2. Diet disparity among sympatric herbivorous cichlids in the same ecomorphs in Lake Tanganyika: amplicon pyrosequences on algal farms and stomach contents.

    PubMed

    Hata, Hiroki; Tanabe, Akifumi S; Yamamoto, Satoshi; Toju, Hirokazu; Kohda, Masanori; Hori, Michio

    2014-10-29

    Lake Tanganyika, an ancient lake in the Great Rift Valley, is famous for the adaptive radiation of cichlids. Five tribes of the Cichlidae family have acquired herbivory, with five ecomorphs: grazers, browsers, scrapers, biters and scoopers. Sixteen species of the herbivorous cichlids coexist on a rocky littoral slope in the lake. Seven of them individually defend feeding territories against intruding herbivores to establish algal farms. We collected epiphyton from these territories at various depths and also gathered fish specimens. Algal and cyanobacteria community structures were analysed using the amplicon-metagenomic method. Based on 454-pyrosequencing of SSU rRNA gene sequences, we identified 300 phototrophic taxa, including 197 cyanobacteria, 57 bacillariophytes, and 31 chlorophytes. Algal farms differed significantly in their composition among cichlid species, even in the same ecomorph, due in part to their habitat-depth segregation. The algal species composition of the stomach contents and algal farms of each species differed, suggesting that cichlids selectively harvest their farms. The stomach contents were highly diverse, even between species in the same tribe, in the same feeding ecomorph. In this study, the amplicon-metagenomic approach revealed food niche separation based on habitat-depth segregation among coexisting herbivorous cichlids in the same ecomorphs in Lake Tanganyika.

  3. Textural and compositional variability across littoral segments of Lake Tanganyika: The effect of asymmetric basin structure on sedimentation in large rift lakes

    SciTech Connect

    Soreghan, M.J.; Cohen, A.S.

    1996-03-01

    Lake Tanganyika, part of the East African rift system, represents one of the most widely cited modern analogs for interpreting ancient rift lakes. To date, few published detailed sedimentologic studies of the modern sediments allow for comparisons to outcrop- and well-bore-scale observations within ancient strata. Four recurrent structural margin types exist along the alternating half-graben structure of the lake: hinged margins, axial margins, accommodation zone margins, and escarpment margins. The hinged margin consists of a series of structurally controlled benches over which long, continuous tracts of bioclastic lag deposits predominate; clastic sands are limited to moderate-size silty deltas and long, narrow shoreface sands. The axial margin is dominated by a wave-dominated, silt-rich delta system. Accommodation zone margins consist of bioclastic lag deposits atop structural highs, whereas carbonate and clastic mud accumulates farther offshore. Escarpment margins contain small fan-delta deposits alternating along shore with talus deposits; offshore carbonate and clastic mud is present away from active gravity-flow deposition. Total organic carbon (TOC) and pyrolysis data from fine-grained samples subtly reflect the contrasts in margin types, but these values are controlled more directly by water depth. Although facies are similar among all margin types, their spatial distribution, in particular the degree to which facies tracts trend parallel to shore, best discriminates among the different margin types. These data suggest that unique but predictable associations of reservoir, seal, and source facies exist along each of the different margin types.

  4. Genetic and morphological population differentiation in the rock-dwelling and specialized shrimp-feeding cichlid fish species Altolamprologus compressiceps from Lake Tanganyika, East Africa.

    PubMed

    Spreitzer, Maria Luise; Mautner, Selma; Makasa, Lawrence; Sturmbauer, Christian

    With about 250 endemic species, Lake Tanganyika contains an extraordinarily diverse cichlid fish fauna, and thus represents an ideal model system for the study of pathways and processes of speciation. The Lamprologini form the most species-rich tribe in Lake Tanganyika comprising about 100 species in seven genera, most of which are endemic to the lake. They are territorial substrate-breeders and represent a monophyletic tribe. By combined analysis of population genetics and geometric morphometric markers, we assessed gene flow among three populations of the highly specialized shrimp-feeding rock-dweller Altolamprologus compressiceps, separated by geographic distance and ecological barriers. Five highly polymorphic microsatellite markers were analyzed in conjunction with 17 landmarks in order to compare genetic differences to body shape differences among populations. Both genetic and morphological analyses revealed significant differentiation among the three studied populations. A significant, but overall relatively low degree of genetic differentiation supports a very recent divergence. Phenotypic differentiation was primarily found in the head region of A. compressiceps. In agreement with findings in other cichlid species, similar adaptations to specialized feeding mechanisms can consequently lead to marginal shape changes in the trophic apparatus.

  5. Community assembly in Lake Tanganyika cichlid fish: quantifying the contributions of both niche-based and neutral processes.

    PubMed

    Janzen, Thijs; Alzate, Adriana; Muschick, Moritz; Maan, Martine E; van der Plas, Fons; Etienne, Rampal S

    2017-02-01

    The cichlid family features some of the most spectacular examples of adaptive radiation. Evolutionary studies have highlighted the importance of both trophic adaptation and sexual selection in cichlid speciation. However, it is poorly understood what processes drive the composition and diversity of local cichlid species assemblages on relatively short, ecological timescales. Here, we investigate the relative importance of niche-based and neutral processes in determining the composition and diversity of cichlid communities inhabiting various environmental conditions in the littoral zone of Lake Tanganyika, Zambia. We collected data on cichlid abundance, morphometrics, and local environments. We analyzed relationships between mean trait values, community composition, and environmental variation, and used a recently developed modeling technique (STEPCAM) to estimate the contributions of niche-based and neutral processes to community assembly. Contrary to our expectations, our results show that stochastic processes, and not niche-based processes, were responsible for the majority of cichlid community assembly. We also found that the relative importance of niche-based and neutral processes was constant across environments. However, we found significant relationships between environmental variation, community trait means, and community composition. These relationships were caused by niche-based processes, as they disappeared in simulated, purely neutrally assembled communities. Importantly, these results can potentially reconcile seemingly contrasting findings in the literature about the importance of either niche-based or neutral-based processes in community assembly, as we show that significant trait relationships can already be found in nearly (but not completely) neutrally assembled communities; that is, even a small deviation from neutrality can have major effects on community patterns.

  6. Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa

    SciTech Connect

    Barrat, J.A.; Boulegue, J.; Tiercelin, J.J.; Lesourd, M.

    2000-01-01

    At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The {sup 87}Sr/{sup 86}Sr ratios of the chimneys indicate that they have precipitated from a mixture of lake water (more than 95%) and hydrothermal fluids. No zoning in the chimneys was detected with the Sr data. For the rare-earth elements, the situation is more complex. The external walls of the chimneys are rare-earth-element-poor (La {approx} 500 ppb, Yb {approx} 200 ppb, La/Yb = 2 to 3.4). Their shale normalized rare-earth element patterns suggest that they are in equilibrium with the inferred carbonate-depositing fluids. The rare-earth element concentrations of the internal walls of the chimneys are significantly light rare earth elements (LREE)-enriched with La contents sometimes up to 5 ppm. The authors suggest that they contain more vent-fluid rare-earth elements than the external wall samples, possibly adsorbed on the surface of growing crystals or simply hosted by impurities. It was not possible to constrain the nature of these phases, but the variations of the compositions of the internal wall materials of the active chimneys with time, as well as data obtained on an inactive chimney indicate that this rare-earth element excess is mobile. Partition coefficients were calculated between the external wall aragonite and carbonate-depositing fluid. The results are strikingly similar to the values obtained by Sholkovitz and Shen (1995) on coral aragonite, and suggest that there is no significant biologic effect on the incorporation of rare-earth elements into coral aragonite and that the various carbonate complexes involved Me(CO{sub 3}{sup +}) complexes are the main LREE carriers in seawater instead of Me(CO{sub 3}){sub 2}{sup {minus}} in Banza fluids

  7. The Lake Tanganyika Accommodation Zone Structural Highs: Probable Archive of Continuous Miocene to Recent Paleoenvironmental and Paleoclimatic Information for East Africa

    NASA Astrophysics Data System (ADS)

    Cohen, A. S.; Lezzar, K. E.; Russell, J.; Scholz, C. A.; Tiercelin, J.; Gans, C. R.; Helfrich, L. C.

    2004-12-01

    Continental drilling of lake deposits has proven an important source of high-resolution paleoclimatic and paleoenvironmental information. The large rift lakes of East Africa react dramatically to climatic perturbations, recording responses in sedimentary records of lake level, chemistry, and biota. No continuous continental paleoclimate records covering the full period of hominid evolution, especially the critical transitions of the late Miocene through the Plio-Pleistocene, are currently available or forthcoming. However, approximately 1000 km of sparker and air gun reflection seismic profiles collected during a number of field campaigns on Lake Tanganyika demonstrate the existence of three major mid-lake isolated structural highs: from N-S the Ubwari, Kavala Island, and Kalya horsts, whose sedimentary cover may provide records of this critical interval. Several coring campaigns demonstrated sedimentation rates over the last 100 ka much slower than adjacent basinal settings, in some cases as low as 0.1 mm/year. Sequence stratigraphic analyses of sediments on the shallower (300-500 m) of these horsts (Ubwari and Kavala Island), and on other structural platforms have shown the presence of numerous unconformities related to lake level fluctuations and paleoclimatic variability. During the Last Glacial Maximum, for example, features such as prograding delta lobes and paleochannels indicate water levels may have fallen by as much as 360 meters. Erosional unconformities at depths of as much as 600 m have been noted at basinal sites adjacent to these relatively shallow horsts. The northeastern edge of the Kalya horst, however, lies at sufficient water depths (> 600 m) to have escaped these major erosional truncations. Furthermore, this site is located in a depositional environment of relative tectonic quiescence, apparently undisturbed by faulting, unlike the northern structural highs. Preliminary seismic stratigraphic analysis of the Kalya horst shows the presence of at

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

    PubMed Central

    2010-01-01

    Background While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid fishes have evolved dental and craniofacial asymmetries in order to more effectively remove scales from the left or right flanks of prey. Here we examine the evolution and development of craniofacial morphology and laterality among Lake Tanganyika scale-eating cichlids. Results Using both geometric and traditional morphometric methods we found that the craniofacial evolution in the Perissodini involved discrete shifts in skeletal anatomy that reflect differences in habitat preference and predation strategies. Further, we show that the evolutionary history of the Perissodini is characterized by an accentuation of craniofacial laterality such that certain taxa show elaborate sided differences in craniofacial shape consistent with the sub-partitioning of function between sides of the head during attacks. Craniofacial laterality in the scale-eating specialist Perissodus microlepis was found to be evident early in development and exhibited a unimodal distribution, which is contrary to the adult condition where jaw laterality has been described as a discrete, bimodal antisymmetry. Finally, using linkage and association analyses we identified a conserved locus for jaw handedness that segregates among East African cichlids. Conclusions We suggest that, during the evolution of the Perissodini, selection has accentuated a latent, genetically determined handedness of the craniofacial skeleton, enabling the evolution of jaw asymmetries in order to increase predation success. Continued work on the developmental genetic basis of laterality in the Perissodini will

  9. Reduced host-specificity in a parasite infecting non-littoral Lake Tanganyika cichlids evidenced by intraspecific morphological and genetic diversity.

    PubMed

    Kmentová, Nikol; Gelnar, Milan; Mendlová, Monika; Van Steenberge, Maarten; Koblmüller, Stephan; Vanhove, Maarten P M

    2016-12-22

    Lake Tanganyika is well-known for its high species-richness and rapid radiation processes. Its assemblage of cichlid fishes recently gained momentum as a framework to study parasite ecology and evolution. It offers a rare chance to investigate the influence of a deepwater lifestyle in a freshwater fish-parasite system. Our study represents the first investigation of parasite intraspecific genetic structure related to host specificity in the lake. It focused on the monogenean flatworm Cichlidogyrus casuarinus infecting deepwater cichlids belonging to Bathybates and Hemibates. Morphological examination of C. casuarinus had previously suggested a broad host range, while the lake's other Cichlidogyrus species are usually host specific. However, ongoing speciation or cryptic diversity could not be excluded. To distinguish between these hypotheses, we analysed intraspecific diversity of C. casuarinus. Monogeneans from nearly all representatives of the host genera were examined using morphometrics, geomorphometrics and genetics. We confirmed the low host-specificity of C. casuarinus based on morphology and nuclear DNA. Yet, intraspecific variation of sclerotized structures was observed. Nevertheless, the highly variable mitochondrial DNA indicated recent population expansion, but no ongoing parasite speciation, confirming, for the first time in freshwater, reduced parasite host specificity in the deepwater realm, probably an adaptation to low host availability.

  10. Separated by sand, fused by dropping water: habitat barriers and fluctuating water levels steer the evolution of rock-dwelling cichlid populations in Lake Tanganyika.

    PubMed

    Koblmüller, Stephan; Salzburger, Walter; Obermüller, Beate; Eigner, Eva; Sturmbauer, Christian; Sefc, Kristina M

    2011-06-01

    The conditions of phenotypic and genetic population differentiation allow inferences about the evolution, preservation and loss of biological diversity. In Lake Tanganyika, water level fluctuations are assumed to have had a major impact on the evolution of stenotopic littoral species, though this hypothesis has not been specifically examined so far. The present study investigates whether subtly differentiated colour patterns of adjacent Tropheus moorii populations are maintained in isolation or in the face of continuous gene flow, and whether the presumed influence of water level fluctuations on lacustrine cichlids can be demonstrated in the small-scale population structure of the strictly stenotopic, littoral Tropheus. Distinct population differentiation was found even across short geographic distances and minor habitat barriers. Population splitting chronology and demographic histories comply with our expectation of old and rather stable populations on steeper sloping shore, and more recently established populations in a shallower region. Moreover, population expansions seem to coincide with lake level rises in the wake of Late Pleistocene megadroughts ~100 KYA. The imprint of hydrologic events on current population structure in the absence of ongoing gene flow suggests that phenotypic differentiation among proximate Tropheus populations evolves and persists in genetic isolation. Sporadic gene flow is effected by lake level fluctuations following climate changes and controlled by the persistence of habitat barriers during lake level changes. Since similar demographic patterns were previously reported for Lake Malawi cichlids, our data furthermore strengthen the hypothesis that major climatic events synchronized facets of cichlid evolution across the East African Great Lakes. © 2011 Blackwell Publishing Ltd.

  11. First description of monogenean parasites in Lake Tanganyika: the cichlid Simochromis diagramma (Teleostei, Cichlidae) harbours a high diversity of Gyrodactylus species (Platyhelminthes, Monogenea).

    PubMed

    Vanhove, Maarten P M; Snoeks, Jos; Volckaert, Filip A M; Huyse, Tine

    2011-03-01

    Lake Tanganyika harbours the most diverse endemic cichlid fish assemblage of Africa, but its monogenean fish parasites have not been investigated. Here we report, for the first time, on the Gyrodactylus parasites in this hotspot of fish biodiversity. Haptor morphometrics and nuclear ribosomal DNA sequences revealed 3 new species on Zambian Simochromis diagramma: Gyrodactylus sturmbaueri n. sp., G. thysi n. sp. and G. zimbae n. sp. Their distinct morphology and strong genetic differentiation suggest that they belong to distant lineages within the genus Gyrodactylus, and phylogenetic reconstructions suggest affinities with other genera of gyrodactylids. Additional U-shaped haptoral plates in G. thysi n. sp. and a second large spine-like structure in the male copulatory organ of G. zimbae seem to represent new features for the genus. Such large diversity on a single host species can probably be explained by host-switching events during the course of evolution, in agreement with the generally accepted concept that ecological transfer is an important aspect of gyrodactylid speciation. Additional parasitological surveys on other host species, covering a broader phylogenetic and geographical range, should clarify the evolutionary history of Gyrodactylidae on cichlids in the African Great Lake and other parts of Africa.

  12. Reduced host-specificity in a parasite infecting non-littoral Lake Tanganyika cichlids evidenced by intraspecific morphological and genetic diversity

    PubMed Central

    Kmentová, Nikol; Gelnar, Milan; Mendlová, Monika; Van Steenberge, Maarten; Koblmüller, Stephan; Vanhove, Maarten P. M.

    2016-01-01

    Lake Tanganyika is well-known for its high species-richness and rapid radiation processes. Its assemblage of cichlid fishes recently gained momentum as a framework to study parasite ecology and evolution. It offers a rare chance to investigate the influence of a deepwater lifestyle in a freshwater fish-parasite system. Our study represents the first investigation of parasite intraspecific genetic structure related to host specificity in the lake. It focused on the monogenean flatworm Cichlidogyrus casuarinus infecting deepwater cichlids belonging to Bathybates and Hemibates. Morphological examination of C. casuarinus had previously suggested a broad host range, while the lake’s other Cichlidogyrus species are usually host specific. However, ongoing speciation or cryptic diversity could not be excluded. To distinguish between these hypotheses, we analysed intraspecific diversity of C. casuarinus. Monogeneans from nearly all representatives of the host genera were examined using morphometrics, geomorphometrics and genetics. We confirmed the low host-specificity of C. casuarinus based on morphology and nuclear DNA. Yet, intraspecific variation of sclerotized structures was observed. Nevertheless, the highly variable mitochondrial DNA indicated recent population expansion, but no ongoing parasite speciation, confirming, for the first time in freshwater, reduced parasite host specificity in the deepwater realm, probably an adaptation to low host availability. PMID:28004766

  13. Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Husby, Arild; Kotrschal, Alexander; Hayward, Alexander; Buechel, Séverine D; Zidar, Josefina; Løvlie, Hanne; Kolm, Niclas

    2015-01-01

    The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  14. Testing the potential of DNA barcoding in vertebrate radiations: the case of the littoral cichlids (Pisces, Perciformes, Cichlidae) from Lake Tanganyika.

    PubMed

    Breman, Floris C; Loix, Sara; Jordaens, Kurt; Snoeks, Jos; Van Steenberge, Maarten

    2016-11-01

    We obtained 398 cytochrome c oxidase subunit I barcodes of 96 morphospecies of Lake Tanganyika (LT) cichlids from the littoral zone. The potential of DNA barcoding in these fishes was tested using both species identification and species delineation methods. The best match (BM) and best close match (BCM) methods were used to evaluate the overall identification success. For this, three libraries were analysed in which the specimens were categorized into Operational Taxonomic Units (OTU) in three alternative ways: (A) morphologically distinct, including undescribed, species, (B) valid species and (C) complexes of morphologically similar or closely related species. For libraries A, B and C, 73, 73 and 96% (BM) and 72, 70 and 94% (BCM) of the specimens were correctly identified. Additionally, the potential of two species delineation methods was tested. The General Mixed Yule Coalescent (GMYC) analysis suggested 70 hypothetical species, while the Automatic Barcode Gap Discovery (ABGD) method revealed 115 putative species. Although the ABGD method had a tendency to oversplit, it outperformed the GMYC analysis in retrieving the species. In most cases where ABGD suggested oversplitting, this was due to intraspecific geographical variation. The failure of the GMYC method to retrieve many species could be attributed to discrepancies between mitochondrial gene trees and the evolutionary histories of LT cichlid species. Littoral LT cichlids have complex evolutionary histories that include instances of hybridization, introgression and rapid speciation. Nevertheless, although the utility of DNA barcoding in identification is restricted to the level of complexes, it has potential for species discovery in cichlid radiations. © 2016 John Wiley & Sons Ltd.

  15. Genetic evidence for prevalence of alloparental care in a socially monogamous biparental cichlid fish, Perissodus microlepis, from Lake Tanganyika supports the "selfish shepherd effect" hypothesis.

    PubMed

    Lee, Hyuk Je; Heim, Valentin; Meyer, Axel

    2016-05-01

    Alloparental care - care for unrelated young - is rare in animals, and its ecological or evolutionary advantages or, alternative maladaptive nature, remain unclear. We investigate alloparental care in the socially monogamous cichlid fish Perissodus microlepis from Lake Tanganyika that exhibits bi-parental care. In a genetic parentage analysis, we discovered a surprisingly high percentage of alloparental care represented by brood mixing, extra-pair paternity and extra-pair maternity in all broods that we investigated. The percentage of nondescendant juveniles of other parents, i.e., brood mixing, ranged from 5% to 57% (mean = 28%). The distribution of genetic parentage also suggests that this socially monogamous species has, in fact, polygamous mating system. The prevalence of genetically mixed broods can be best explained by two, not mutually exclusive hypotheses on farming-out and fostering behaviors. In the majority of broods, the sizes of the parents' own (descendant) offspring were significantly larger than those of the adopted (nondescendant) juveniles, supporting the 'selfish shepherd effect' hypothesis, i.e., that foster parents preferentially accept unrelated "smaller or not larger" young since this would tend to lower the predation risks for their own larger offspring. There was also a tendency for larger parents particularly mothers, more so than smaller parents, to care predominantly for their own offspring. Larger parents might be better at defending against cuckoldry and having foreign young dumped into their broods through farming-out behavior. This result might argue for maladaptive effects of allopatric care for the foster parents that only larger and possibly more experienced pairs can guard against. It needs to be determined why, apparently, the ability to recognize one's own young has not evolved in this species.

  16. Spectral P-wave magnitudes, magnitude spectra and other source parameters for the 1990 southern Sudan and the 2005 Lake Tanganyika earthquakes

    NASA Astrophysics Data System (ADS)

    Moussa, Hesham Hussein Mohamed

    2008-10-01

    Teleseismic Broadband seismograms of P-waves from the May 1990 southern Sudan and the December, 2005 Lake Tanganyika earthquakes; the western branch of the East African Rift System at different azimuths have been investigated on the basis of magnitude spectra. The two earthquakes are the largest shocks in the East African Rift System and its extension in southern Sudan. Focal mechanism solutions along with geological evidences suggest that the first event represents a complex style of the deformation at the intersection of the northern branch of the western branch of the East African Rift and Aswa Shear Zone while the second one represents the current tensional stress on the East African Rift. The maximum average spectral magnitude for the first event is determined to be 6.79 at 4 s period compared to 6.33 at 4 s period for the second event. The other source parameters for the two earthquakes were also estimated. The first event had a seismic moment over fourth that of the second one. The two events are radiated from patches of faults having radii of 13.05 and 7.85 km, respectively. The average displacement and stress drop are estimated to be 0.56 m and 1.65 MPa for the first event and 0.43 m and 2.20 MPa for the second one. The source parameters that describe inhomogeneity of the fault are also determined from the magnitude spectra. These additional parameters are complexity, asperity radius, displacements across the asperity and ambient stress drop. Both events produce moderate rupture complexity. Compared to the second event, the first event is characterized by relatively higher complexity, a low average stress drop and a high ambient stress. A reasonable explanation for the variations in these parameters may suggest variation in the strength of the seismogenic fault which provides the relations between the different source parameters. The values of stress drops and the ambient stresses estimated for both events indicate that these earthquakes are of interplate

  17. Infestation and pathological alterations by Ergasilus sarsi (Copepoda) on the Tanganyika Killifish from Africa.

    PubMed

    Kilian, Esmari; Avenant-Oldewage, Annemariè

    2013-12-01

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

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

    PubMed Central

    Kilian, Esmari; Avenant-Oldewage, Annemariè

    2013-01-01

    A total of 204 Ergasilus sarsi, a copepod, were collected from Tanganyika Killifish Lamprichthys tanganicanus in Lake Tanganyika during March 2010. The prevalence was 86.40%, the mean intensity was 7.56, and the mean abundance was 6.38. Only 27 of the fish were infested, and the highest infestation on one fish was 29. Proliferation of mucus cells and lamellar fusion occurred. Haemorrhage due to blood vessel compression was noted. This is the first record of E. sarsi from Tanganyika Killifish. This study is also the first to provide a description of the pathological alterations caused by E. sarsi. PMID:24341764

  19. Modelling the oscillations of the thermocline in a lake by means of a fully consistent and conservative 3D finite-element model with a vertically adaptive mesh

    NASA Astrophysics Data System (ADS)

    Delandmeter, Philippe; Lambrechts, Jonathan; Vallaeys, Valentin; Naithani, Jaya; Remacle, Jean-François; Legat, Vincent; Deleersnijder, Eric

    2017-04-01

    Vertical discretisation is crucial in the modelling of lake thermocline oscillations. For finite element methods, a simple way to increase the resolution close to the oscillating thermocline is to use vertical adaptive coordinates. With an Arbitrary Lagrangian-Eulerian (ALE) formulation, the mesh can be adapted to increase the resolution in regions with strong shear or stratification. In such an application, consistency and conservativity must be strictly enforced. SLIM 3D, a discontinuous-Galerkin finite element model for shallow-water flows (www.climate.be/slim, e.g. Kärnä et al., 2013, Delandmeter et al., 2015), was designed to be strictly consistent and conservative in its discrete formulation. In this context, special care must be paid to the coupling of the external and internal modes of the model and the moving mesh algorithm. In this framework, the mesh can be adapted arbitrarily in the vertical direction. Two moving mesh algorithms were implemented: the first one computes an a-priori optimal mesh; the second one diffuses vertically the mesh (Burchard et al., 2004, Hofmeister et al., 2010). The criteria used to define the optimal mesh and the diffusion function are related to a suitable measure of shear and stratification. We will present in detail the design of the model and how the consistency and conservativity is obtained. Then we will apply it to both idealised benchmarks and the wind-forced thermocline oscillations in Lake Tanganyika (Naithani et al. 2002). References Tuomas Kärnä, Vincent Legat and Eric Deleersnijder. A baroclinic discontinuous Galerkin finite element model for coastal flows, Ocean Modelling, 61:1-20, 2013. Philippe Delandmeter, Stephen E Lewis, Jonathan Lambrechts, Eric Deleersnijder, Vincent Legat and Eric Wolanski. The transport and fate of riverine fine sediment exported to a semi-open system. Estuarine, Coastal and Shelf Science, 167:336-346, 2015. Hans Burchard and Jean-Marie Beckers. Non-uniform adaptive vertical grids in

  20. Back to Tanganyika: a case of recent trans-species-flock dispersal in East African haplochromine cichlid fishes.

    PubMed

    Meyer, Britta S; Indermaur, Adrian; Ehrensperger, Xenia; Egger, Bernd; Banyankimbona, Gaspard; Snoeks, Jos; Salzburger, Walter

    2015-03-01

    The species flocks of cichlid fishes in the East African Great Lakes are the largest vertebrate adaptive radiations in the world and illustrious textbook examples of convergent evolution between independent species assemblages. Although recent studies suggest some degrees of genetic exchange between riverine taxa and the lake faunas, not a single cichlid species is known from Lakes Tanganyika, Malawi and Victoria that is derived from the radiation associated with another of these lakes. Here, we report the discovery of a haplochromine cichlid species in Lake Tanganyika, which belongs genetically to the species flock of haplochromines of the Lake Victoria region. The new species colonized Lake Tanganyika only recently, suggesting that faunal exchange across watersheds and, hence, between isolated ichthyofaunas, is more common than previously thought.

  1. 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.

  2. Out of Tanganyika: Genesis, explosive speciation, key-innovations and phylogeography of the haplochromine cichlid fishes

    PubMed Central

    Salzburger, Walter; Mack, Tanja; Verheyen, Erik; Meyer, Axel

    2005-01-01

    Background The adaptive radiations of cichlid fishes in East Africa are well known for their spectacular diversity and their astonishingly fast rates of speciation. About 80% of all 2,500 cichlid species in East Africa, and virtually all cichlid species from Lakes Victoria (~500 species) and Malawi (~1,000 species) are haplochromines. Here, we present the most extensive phylogenetic and phylogeographic analysis so far that includes about 100 species and is based on about 2,000 bp of the mitochondrial DNA. Results Our analyses revealed that all haplochromine lineages are ultimately derived from Lake Tanganyika endemics. We find that the three most ancestral lineages of the haplochromines sensu lato are relatively species poor, albeit widely distributed in Africa, whereas a fourth newly defined lineage – the 'modern haplochromines' – contains an unparalleled diversity that makes up more than 7% of the worlds' ~25,000 teleost species. The modern haplochromines' ancestor, most likely a riverine generalist, repeatedly gave rise to similar ecomorphs now found in several of the species flocks. Also, the Tanganyikan Tropheini are derived from that riverine ancestor suggesting that they successfully re-colonized Lake Tanganyika and speciated in parallel to an already established cichlid adaptive radiation. In contrast to most other known examples of adaptive radiations, these generalist ancestors were derived from highly diverse and specialized endemics from Lake Tanganyika. A reconstruction of life-history traits revealed that in an ancestral lineage leading to the modern haplochromines the characteristic egg-spots on anal fins of male individuals evolved. Conclusion We conclude that Lake Tanganyika is the geographic and genetic cradle of all haplochromine lineages. In the ancestors of the replicate adaptive radiations of the 'modern haplochromines', behavioral (maternal mouthbrooding), morphological (egg-spots) and sexually selected (color polymorphism) key

  3. Characterizing seasonal and diel vertical movement and habitat use of lake whitefish (Coregonus clupeaformis) in Clear Lake, Maine

    USGS Publications Warehouse

    Zydlewski, Joseph; Gorsky, Dimitry; Balsey, David

    2016-01-01

    Seasonal and daily vertical activity of lake whitefish Coregonus clupeaformis was studied in Clear Lake, Maine (253 ha), using acoustic telemetry from November 2004 to June 2009. Twenty adult lake whitefish were tagged with acoustic tags that had either a depth sensor or both depth and temperature sensors to assess vertical habitat use at a seasonal and daily resolution. Vertical habitat selection varied seasonally and was strongly influenced by temperature. Between December and April, when the lake was covered with ice, surface temperature was below 2°C and tagged individuals occupied deep areas of the lake (∼15 m). After ice-out, fish ascended into shallow waters (∼5 m), responding to increased water temperature and possibly to greater foraging opportunity. When surface water temperatures exceeded 20°C, fish descended below the developing thermocline (∼9 m), where they remained until surface temperatures fell below 20°C; fish then ascended into shallower depths, presumably for feeding and spawning. Through the winter, fish remained in thermal habitats that were warmer than the surface temperatures; in the summer, they selected depths with thermal habitats below 15°C. Though the amplitude varied greatly across seasons, lake whitefish displayed a strong diurnal pattern of activity as measured by vertical velocities. Fish were twofold more active during spring, summer, and fall than during winter. Lake whitefish exhibited diel vertical migrations, rising in the water column during nighttime and occupying deeper waters during the day. This pattern was more pronounced in the spring and fall and far less prominent during winter and summer. The strong linkage between temperature and habitat use may limit the current range of lake whitefish and may be directly impacted by climatic change.

  4. [Vertical distribution of water quality and its influence on underwater light field in Lake Chaohu].

    PubMed

    Ma, Meng-Xiao; Zhang, Yu-Chao; Qian, Xin; Ma, Rong-Hua; Duan, Hong-Tao

    2014-05-01

    There are few reports on the vertical distribution of water quality and its influence on underwater light field. In our study, we analyzed the vertical distribution of water quality based on the in situ data in Lake Chaohu, and studied their influence on diffuse attenuation coefficients of downwelling irradiance Kd via Hydrolight simulation. It was indicated that the suspended matter and colored dissolved organic matter (CDOM) were relatively vertical-uniform in Lake Chaohu; excluding algae scums at the surface, the vertical profiles of chlorophyll-a conformed to Gaussian distribution; the complex Kd in vertical was affected by chlorophyll-a and inorganic suspended matter. The analysis on vertical distributions of water quality and its influence on Kd could be the basis for further studying the influence of algae vertical heterogeneity on underwater light field in Case II waters.

  5. Shifts of radiocesium vertical profiles in sediments and their modelling in Japanese lakes.

    PubMed

    Fukushima, Takehiko; Komatsu, Eiji; Arai, Hiroyuki; Kamiya, Koichi; Onda, Yuichi

    2017-10-07

    Vertical profiles of radiocesium concentrations were measured in sediment cores collected at various times after the 2011 Fukushima nuclear accident in five Japanese lakes (Hinuma, Kasumigaura, Kitaura, Onogawa and Sohara) with different morphological and trophic characteristics in order to investigate the sedimentation-diffusion processes. In lakes where sediments had high porosities and experienced considerable wave action due to shallowness, we observed rapid penetration of radiocesium to a certain depth just after the accident, followed by downward movement of the peak depths. In contrast, gradual downward transfers of distinct peaks were found in other types of lakes. A one-dimensional differential sediment model with water-sediments interaction processes was constructed to describe the vertical shift of radiocesium profiles. Our proposed submodels relating to the length scales of the mixing using wind-induced stress and porosity of sediments were constructed based on one measurement of the vertical distribution of radiocesium in three lakes (Hinuma, Kasumigaura and Sohara). This model was then validated using samples from those lakes in different years, as well as from two other lakes. Good agreement was obtained. We discuss our findings, the limits of model application, and future research targets. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Vertical transport of mercury in a Wisconsin seepage lake

    SciTech Connect

    Hurley, J.P. ); Watras, C.J. )

    1990-01-09

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

  7. Vertical profiles of sediment methanogenic potential and communities in two plateau freshwater lakes

    NASA Astrophysics Data System (ADS)

    Yang, Yuyin; Li, Ningning; Wang, Wei; Li, Bingxin; Xie, Shuguang; Liu, Yong

    2017-01-01

    Microbial methanogenesis in sediment plays a crucial role in CH4 emission from freshwater lake ecosystems. However, knowledge of the layer-depth-related changes of methanogen community structure and activities in freshwater lake sediment is still limited. The present study was conducted to characterize the methanogenesis potential in different sediment-layer depths and the vertical distribution of microbial communities in two freshwater lakes of different trophic status on the Yunnan Plateau (China). Incubation experiments and inhibitor studies were carried out to determine the methanogenesis potential and pathways. 16S rRNA and mcrA genes were used to investigate the abundance and structure of methanogen and archaeal communities, respectively. Hydrogenotrophic methanogenesis was mainly responsible for methane production in sediments of both freshwater lakes. The layer-depth-related changes of methanogenesis potential and the abundance and community structure of methanogens were observed in both Dianchi Lake and Erhai Lake. Archaeal 16S rRNA and mcrA genes displayed a similar abundance change pattern in both lakes, and the relative abundance of methanogens decreased with increasing sediment-layer depth. Archaeal communities differed considerably in Dianchi Lake and Erhai Lake, but methanogen communities showed a slight difference between these two lakes. However, methanogen communities illustrated a remarkable layer-depth-related change. Order Methanomicrobiales was the dominant methanogen group in all sediments, while Methanobacteriales showed a high proportion only in upper layer sediments. The trophic status of the lake might have a notable influence on the depth-related change pattern of methanogenesis activity, while the methanogen community structure was mainly influenced by sediment depth.

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

    USGS Publications Warehouse

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

    1994-01-01

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

  9. Metabolism estimates in small boreal lakes: the importance of accounting for vertical fluxes of oxygen

    NASA Astrophysics Data System (ADS)

    Klaus, M.; MacIntyre, S.; Hotchkiss, E. R.; Bergström, A. K.; Karlsson, J.

    2015-12-01

    Lake metabolism models based on the diel oxygen technique often assume that oxygen dynamics are mainly controlled by metabolic processes, only accounting for wind-driven atmospheric gas exchange. However, oxygen dynamics can also be affected by abiotic mass fluxes across oxygen gradients within lakes and atmospheric gas exchange driven by convection. Here, we quantify how much vertical fluxes of oxygen modify epilimnetic metabolism estimates for three pairs of small Swedish boreal lakes, one of each fertilized with nitrate, with dissolved organic carbon (DOC) concentrations of 7 to 22 mg l-1. Oxygen concentrations were measured every 10 min at 50 cm depth and biweekly across depths profiles during one full open water period. Based on additional two weeks of ten-minute oxygen profiling we calculated vertical fluxes of oxygen using equations for atmospheric gas exchange caused by wind shear (F1) and convection (F2), and lake-internal gas exchange caused by diffusion and mixed layer deepening (F3). We ran three inverse Bayesian models to estimate daily metabolism: (M1) accounting for F1, (M2) accounting for F1 and F2, and (M3) accounting for F1 and F3. Initial results suggest that gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) ranged from 0.1 to 0.2, -0.3 to -0.5 and -0.2 to -0.4 g C m-2 d-1, respectively. GPP and R were higher in fertilized lakes and at the lower end of previous worldwide estimates. Accounting for convection-driven gas exchange increased ER estimates by 10-40% (M2 vs. M1). This bias increased with DOC concentration but was not affected by fertilization. Including lake-internal vertical oxygen fluxes changed GPP and ER estimates by up to ±40% (M3 vs. M1), with inconsistent trends along the DOC-gradient. We conclude that vertical fluxes of oxygen can significantly affect diel oxygen dynamics in oligotrophic humic systems and should therefore be included in metabolism models applied to small boreal lakes.

  10. Satellite monitoring of the vertical temperature profile of Lake Nyos, Cameroon

    NASA Astrophysics Data System (ADS)

    Sabroux, J. C.; Villevieille, A.; Dubois, E.; Doyotte, C.; Halbwachs, M.; Vandemeulebrouck, J.

    1990-08-01

    The present contribution to Lake Nyos studies, which have been carried out since 1987 by a team of French geophysicists working in close cooperation with the "Institut de Recherches Géologiques et Minières" (IRGM) of Cameroon, involves a continuous long-duration remote monitoring of the temperature distribution in the depth of the lake. The system which was developed for that purpose, essentially includes: (1) a vertical chain of temperature probes, lifted by an anchored buoy (called Nyossonde); and (2) an associated telemetry, relayed by the Argos transponder on board the NOAA meteorological satellites. The telemetered data are collected, processed and archived, both in France (Lannion, Toulouse, Garchy) and Cameroun (Yaoundé). Even though the upper part of the chain was damaged, the lower part is still in operation. Analysis of the telemetered data and comparison with other measurements confirm that the presently described monitoring system is well suited for installation in crater lakes.

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2012-09-01

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

  13. Sediment infill within rift basins: Facies distribution and effects of deformation: Examples from the Kenya and Tanganyika Rifts, East Africa

    SciTech Connect

    Tiercelin, J.J.; Lezzar, K.E. ); Richert, J.P. )

    1994-07-01

    Oil is known from lacustrine basins of the east African rift. The geology of such basins is complex and different depending on location in the eastern and western branches. The western branch has little volcanism, leading to long-lived basins, such as Lake Tanganyika, whereas a large quantity of volcanics results in the eastern branch characterized by ephemeral basins, as the Baringo-Bogoria basin in Kenya. The Baringo-Bogoria basin is a north-south half graben formed in the middle Pleistocene and presently occupied by the hypersaline Lake Bogoria and the freshwater Lake Baringo. Lake Bogoria is fed by hot springs and ephemeral streams controlled by grid faults bounding the basin to the west. The sedimentary fill is formed by cycles of organic oozes having a good petroleum potential and evaporites. On the other hand, and as a consequence of the grid faults, Lake Baringo is fed by permanent streams bringing into the basin large quantities of terrigenous sediments. Lake Tanganyika is a meromictic lake 1470 m deep and 700 km long, of middle Miocene age. It is subdivided into seven asymmetric half grabens separated by transverse ridges. The sedimentary fill is thick and formed by organic oozes having a very good petroleum potential. In contrast to Bogoria, the lateral distribution of organic matter is characterized by considerable heterogeneity due to the existence of structural blocks or to redepositional processes.

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

    PubMed Central

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

    2012-01-01

    Meromictic lakes are useful biogeochemical models because of their stratified chemical gradients and separation of redox reactions down the water column. Perennially ice-covered meromictic lakes are particularly stable, with long term constancy in their density profiles. Here we sampled Lake A, a deep meromictic lake at latitude 83°N in High Arctic Canada. Sampling was before (May) and after (August) an unusual ice-out event during the warm 2008 summer. We determined the bacterial and archaeal community composition by high-throughput 16S rRNA gene tag-pyrosequencing. Both prokaryote communities were stratified by depth and the Bacteria differed between dates, indicating locally driven selection processes. We matched taxa to known taxon-specific biogeochemical functions and found a close correspondence between the depth of functional specialists and chemical gradients. These results indicate a rich microbial diversity despite the extreme location, with pronounced vertical structure in taxonomic and potential functional composition, and with community shifts during ice-out. PMID:22930670

  15. Vertical distribution of major sulfate-reducing bacteria in a shallow eutrophic meromictic lake.

    PubMed

    Kubo, Kyoko; Kojima, Hisaya; Fukui, Manabu

    2014-10-01

    The vertical distribution of sulfate-reducing bacteria was investigated in a shallow, eutrophic, meromictic lake, Lake Harutori, located in a residential area of Kushiro, Japan. A steep chemocline, characterized by gradients of oxygen, sulfide and salinity, was found at a depth of 3.5-4.0 m. The sulfide concentration at the bottom of the lake was high (up to a concentration of 10.7 mM). Clone libraries were constructed using the aprA gene, which encodes adenosine-5'-phosphosulfate reductase subunit A, in order to monitor sulfate-reducing bacteria. In the aprA clone libraries, the most abundant sequences were those from the Desulfosarcina-Desulfococcus (DSS) group. A primer set for a DSS group-specific 16S rRNA gene was used to construct another clone library, analysis of which revealed that the uncultured group of sulfate-reducing bacteria, SEEP SRB-1, accounted for nearly half of the obtained sequences. Quantification of the major bacterial groups by catalyzed reporter deposition-fluorescence in situ hybridization demonstrated that the DSS group accounted for 3.2-4.8% of the total bacterial community below the chemocline. The results suggested that the DSS group was one of the major groups of sulfate-reducing bacteria and that these presumably metabolically versatile bacteria might play an important role in sulfur cycling in Lake Harutori. Copyright © 2014 Elsevier GmbH. All rights reserved.

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

    PubMed

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

    2012-01-01

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

  17. Lake Tanganyika—A 'Melting Pot' of Ancient and Young Cichlid Lineages (Teleostei: Cichlidae)?

    PubMed Central

    Weiss, Juliane D.; Cotterill, Fenton P. D.; Schliewen, Ulrich K.

    2015-01-01

    A long history of research focused on the East Africa cichlid radiations (EAR) revealed discrepancies between mtDNA and nuclear phylogenies, suggesting that interspecific hybridisation may have been significant during the radiation of these fishes. The approximately 250 cichlid species of Lake Tanganyika have their roots in a monophyletic African cichlid assemblage, but controversies remain about the precise phylogenetic origin and placement of different lineages and consequently about L. Tanganyika colonization scenarios. 3312 AFLP loci and the mitochondrial ND2 gene were genotyped for 91 species representing almost all major lacustrine and riverine haplotilapiine east African cichlid lineages with a focus on L. Tanganyika endemics. Explicitly testing for the possibility of ancient hybridisation events, a comprehensive phylogenetic network hypothesis is proposed for the origin and diversification of L. Tanganyika cichlids. Inference of discordant phylogenetic signal strongly suggests that the genomes of two endemic L. Tanganyika tribes, Eretmodini and Tropheini, are composed of an ancient mixture of riverine and lacustrine lineages. For the first time a strong monophyly signal of all non-haplochromine mouthbrooding species endemic to L. Tanganyika (“ancient mouthbrooders”) was detected. Further, in the genomes of early diverging L. Tanganyika endemics Trematocarini, Bathybatini, Hemibatini and Boulengerochromis genetic components of other lineages belonging to the East African Radiation appear to be present. In combination with recent palaeo-geological results showing that tectonic activity in the L. Tanganyika region resulted in highly dynamic and heterogeneous landscape evolution over the Neogene and Pleistocene, the novel phylogenetic data render a single lacustrine basin as the geographical cradle of the endemic L. Tanganyika cichlid lineages unlikely. Instead a scenario of a pre-rift origin of several independent L. Tanganyika precursor lineages which

  18. Biotic and abiotic factors influencing zooplankton vertical distribution in Lake Huron

    USGS Publications Warehouse

    Nowicki, Carly J.; Bunnell, David B.; Armenio, Patricia M.; Warner, David M.; Vanderploeg, Henry A.; Cavaletto, Joann F.; Mayer, Christine M.; Adams, Jean V.

    2017-01-01

    The vertical distribution of zooplankton can have substantial influence on trophic structure in freshwater systems, particularly by determining spatial overlap for predator/prey dynamics and influencing energy transfer. The zooplankton community in some of the Laurentian Great Lakes has undergone changes in composition and declines in total biomass, especially after 2003. Mechanisms underlying these zooplankton changes remain poorly understood, in part, because few studies have described their vertical distributions during daytime and nighttime conditions or evaluated the extent to which predation, resources, or environmental conditions could explain their distribution patterns. Within multiple 24-h periods during July through October 2012 in Lake Huron, we conducted daytime and nighttime sampling of zooplankton, and measured food (chlorophyll-a), temperature, light (Secchi disk depth), and planktivory (biomass of Bythotrephes longimanus and Mysis diluviana). We used linear mixed models to determine whether the densities for 22 zooplankton taxa varied between day and night in the epi-, meta-, and hypolimnion. For eight taxa, higher epilimnetic densities were observed at night than during the day; general linear models revealed these patterns were best explained by Mysis diluviana (four taxa), Secchi disk depth (three taxa), epilimnetic water temperature (three taxa), chlorophyll (one taxon), and biomass of Bythotrephes longimanus (one taxon). By investigating the potential effects of both biotic and abiotic variables on the vertical distribution of crustacean zooplankton and rotifers, we provide descriptions of the Lake Huron zooplankton community and discuss how future changes in food web dynamics or climate change may alter zooplankton distribution in freshwater environments.

  19. Bio-mixing due to Diel Vertical Migration of Daphnia spp. in a Small Lake

    NASA Astrophysics Data System (ADS)

    Simoncelli, Stefano; Wain, Danielle; Thackeray, Stephen

    2016-04-01

    Bio-turbulence or bio-mixing refers to the contribution of living organisms towards the mixing of waters in oceans and lakes. Experimental measurements in an unstratified tank by Wilhelmus & Dabiri (2014) show that zooplankton can trigger fluid instabilities through collective motions and that energy is imparted to scales bigger than organism's size of few mm. Length scales analysis, for low-Reynolds-number organisms in stratified water by Leshansky & Pismen (2010) and Kunze (2011), estimate eddy diffusivity up two orders of magnitude larger than the molecular thermal diffusivity. Very recently, Wand & Ardekani (2015) showed a maximum diffusivity of 10-5 m2/s for millimetre-sized organisms from numerical simulations in the intermediate Reynolds number regime. Here we focus our attention on turbulence generated by the vertical migration of zooplankton in a small lake, mostly populated by Daphnia spp. This very common species, belonging to Cladocera order, is engaged in a vertical migration (DVM) at sunset, with many organisms crossing the thermocline despite the density stratification. During the ascension they may create hydrodynamic disturbances in the lake interior where the stratification usually suppresses the vertical diffusion. We have conducted five turbulence experiments in Vobster Quay, a small (area ˜ 59,000 m2), deep (40m) man-made basin with small wind fetch and steep sides, located in the South West UK. Turbulence was measured with a temperature microstructure profiler. To asses the zooplankton vertical concentration we used a 100 μm mesh net, by collecting and analyzing samples in 8 layers of the lake. A bottom-mounted acoustic Doppler current profiler was also employed to track their concentration and migration with the measured backscatter strength. Measured dissipation rates ɛ during the day showed low turbulence level (<= 10-8 W/Kg) in the thermocline and in the zooplankton layer. Turbulence, during the DVM in two different days, is highest on

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

    PubMed

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

    2004-01-01

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

  1. Vertical migration and nighttime distribution of adult bloaters in Lake Michigan

    USGS Publications Warehouse

    TeWinkel, Leslie M.; Fleischer, Guy W.

    1999-01-01

    The vertical migration and nighttime vertical distribution of adult bloaters Coregonus hoyi were investigated during late summer in Lake Michigan using acoustics simultaneously with either midwater or bottom trawling. Bloaters remained on or near bottom during the day. At night, bloaters were distributed throughout 30-65 m of water, depending on bottom depth. Shallowest depths of migration were not related to water temperature or incident light. Maximum distances of migration increased with increasing bottom depth. Nighttime midwater densities ranged from 0.00 to 6.61 fish/1,000 mA? and decreased with increasing bottom depth. Comparisons of length distributions showed that migrating and nonmigrating bloaters did not differ in size. However, at most sites, daytime bottom catches collected a greater proportion of larger individuals compared with nighttime midwater or bottom catches. Mean target strengths by 5-m strata indicated that migrating bloaters did not stratify by size in the water column at night. Overall, patterns in frequency of empty stomachs and mean digestive state of prey indicated that a portion of the bloater population fed in the water column at night. Bloater diet composition indicated both midwater feeding and bottom feeding. In sum, although a portion of the bloater population fed in the water column at night, bloaters were not limited to feeding at this time. This research confirmed that bloaters are opportunistic feeders and did not fully support the previously proposed hypothesis that bloater vertical migration is driven by the vertically migrating macroinvertebrate the opossom shrimp Mysis relicta.

  2. Vertical structure of archaeal communities and the distribution of ammonia monooxygenase A gene variants in two meromictic High Arctic lakes.

    PubMed

    Pouliot, Jérémie; Galand, Pierre E; Lovejoy, Connie; Vincent, Warwick F

    2009-03-01

    The distribution of archaeal amoA and 16S rRNA genes was evaluated in two marine-derived, meromictic lakes in the Canadian High Arctic: Lake A and Lake C1 on the northern coast of Ellesmere Island. The amoA gene was recorded in both lakes, with highest copy numbers in the oxycline. Sequence analysis showed that amoA from the two lakes shared 94% similarity, indicating at least two phylogenetically distinct clusters. Clone libraries of archaeal 16S rRNA genes from Lake A revealed strong vertical differences in archaeal community diversity and composition down the water column. The oxic layer was dominated by one group of Euryarchaeota affiliated to the Lake Dagow Sediment (LDS) cluster. This group was absent from the oxycline, which had an extremely low archaeal diversity of two phylotypes. Both belonged to the Crenarchaeota Marine Group I (MGI), the marine group that has been linked to archaeal amoA; however, there was a low ratio of amoA to MGI copy numbers, suggesting that many MGI Archaea did not carry the amoA gene. The anoxic zone contained representatives of the RC-V (Rice Cluster-V) and LDS clusters of Euryarchaeota. These results show the strong vertical differentiation of archaeal communities in polar meromictic lakes, and they suggest archaeal nitrification within the oxycline of these highly stratified waters.

  3. Evaluation of the performance of the WRF 1-Dimensional Lake model over the East Africa Great Lakes

    NASA Astrophysics Data System (ADS)

    Gudoshava, M.; Semazzi, F. H. M.

    2015-12-01

    This study seeks to investigate the performance of the 1-Dimensional lake model coupled to WRF over East Africa. The Africa Great lakes exert a great influence on the climate of the region and a number of studies have shown how the lake influences the circulation and the total precipitation over the region. The lakes have highly variable depths, with Lake Victoria having an average depth of 40m and Lake Tanganyika a depth of 450m. The Lake model for WRF was tested and calibrated for the Great lakes, however it was not tested for tropical lakes. We hypothesize that the inclusion of a 1-dimensional lake will reduce the precipitation bias as compared to the WRF model without the lake model. In addition initializing the lake temperature using a vertical temperature profile that closes resembles the one over these lakes will greatly reduce the spin up time. The simulations utilized three nested domains at 36, 12 and 4km. The 4km domain is centered over Lake Victoria Basin, while the 12 km domain includes all the lakes in East Africa. The Tropical Rainfall Measuring Mission (TRMM) datasets are used in evaluating the precipitation, and the following statistics were calculated: root mean square error, standard deviation of the model and observations and mean bias. The results show that the use of the 1-dimensional lake model improves the precipitation over the region considerably compared to an uncoupled model. The asymmetrical rainfall pattern is evident in the simulations. However using the default vertical temperature profile with a three-month spin up is not adequate to transfer heat to the bottom of the lake. Hence the temperatures are still very cold at the bottom. A nine-month spin up improves the lake surface temperatures and lake temperatures at the bottom. A two year spin up greatly improves the lake surface temperatures and hence the total precipitation over the lake. Thus longer spin up time allows for adequate heat transfer in the lake. Initializing the

  4. Vertical stability of mercury in historic and prehistoric sediments from Clear Lake, California.

    PubMed

    Suchanek, Thomas H; Richerson, Peter J; Zierenberg, Robert A; Slotton, Darell G; Mullen, Lauri H

    2008-12-01

    Clear Lake, California, USA, is the site of the Sulphur Bank Mercury Mine, now a U.S. Environmental Protection Agency Superfund Site. Intermittent mining from 1873 to 1957 resulted in approximately 100 Mg of mercury (Hg) being deposited into the lake's ecosystem. Sediment cores to approximately 2.5 m depth (dated using 210Pb and 14C) represent approximately 3000 years of sedimentation. Clear Lake sediments have experienced Hg deposition from anthropogenic sources (mining) during historic times (to the mid-1900s) and geologic sources during prehistoric times (prior to the mid-1800s). This provides a unique opportunity to evaluate hypotheses relating to (1) the influence of the mine on Hg loading to the lake and (2) the potential upward mobilization of Hg by diagenetic processes proposed by some as an alternative explanation for increased Hg concentrations at the surface of the sediment column believed to be caused by increased global atmospheric deposition. Although Hg mining began in 1873, no significant evidence of anthropogenic Hg loading was detected in cores prior to open-pit mining ca. 1927, which also involved bulldozing mine waste rock and tailings into the lake. Exponential increases in total Hg (TotHg) and methylmercury (MeHg) were observed above the 1927 horizon, where estimated sedimentation rates were 2.2-20.4 mm/yr and peaks of both forms of Hg maintained vertical stability within the sediment column. Below the 1927 horizon, a slow increase in both TotHg and MeHg with depth was observed from approximately 1000 to 3000 years before present, where sedimentation rates ranged from approximately 0.6 to 2.0 mm/yr and elevated Hg profiles appear stable. Vertical stability of Hg in the shallow and deep sediment column suggests that both TotHg and MeHg do not undergo diagenetic upward mobilization within the sediment column under rapid or slow sedimentation rates. Because (1) these data were collected at a site with known anthropogenic and geologic sources and

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    Waters and dissolved gases collected along vertical profiles in the five basins (Main, Kabuno Bay, Kalehe, Ishungu, and Bukavu) forming the 485 m deep Lake Kivu (Democratic Republic of the Congo) were analyzed to provide a geochemical conceptual model of the several processes controlling lake chemistry. The measured horizontal and vertical variations of water and gas compositions suggest that each basin has distinct chemical features produced by (1) different contribution from long circulating fluid system containing magmatic CO2, responsible of the huge CO2(CH4)-rich reservoir hosted within the deep lake water; (2) spatial variations of the biomass distribution and/or speciation; and (3) solutes from water-rock interactions. The Kabuno Bay basin is characterized by the highest rate of magmatic fluid input. Accordingly, this basin must be considered the most hazardous site for possible gas outburst that could be triggered by the activity of the Nyiragongo and Nyamulagira volcanoes, located a few kilometers north of the lake.

  6. Big Soda Lake (Nevada). 4. Vertical fluxes of particulate matter: Seasonality and variations across the chemocline

    USGS Publications Warehouse

    Cloern, James E.; Cole, Brian E.; Wienke, Sally M.

    1987-01-01

    Vertical fluxes of particulate organic matter were measured with sediment traps above and below the chemocline of Big Soda Lake to define the seasonality of sinking losses from the mixolimnion and determine the effectiveness of the chemocline (pycnocline) as a barrier to the sinking of biogenic particles. Seasonality of sedimentation rates reflected seasonal changes in the community of autotrophs. During summer-autumn, when production is dominated by autotrophic bacteria, vertical fluxes were small: 100 mg C m−2 d−1 and ≅0.5 mg Chl a m−2 d−1. Following the winter diatom bloom, vertical fluxes increased markedly: ≅570 mg C m−2 d−1 and 23 mg Chl a m−2 d−1. The bulk of the seston (> 80%) and particulate carbon (≅ 65%) sinking to the chemocline passed through it, showing that this very sharp density discontinuity does not effectively retard the sinking of particulate matter. However sinking losses of particulate carbon were generally small (≅10%) relative to previous measures of primary productivity, indicating that the mixolimnion is a zone of efficient carbon cycling. Exceptions occurred following the winter bloom when sinking losses were a larger fraction (≅40%) of productivity.

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

    SciTech Connect

    Lampert, W.; Taylor, B.E.

    1985-02-01

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

  8. Understanding heavy lake-effect snowfall: The vertical structure of radar reflectivity in a deep snowband over and downwind of Lake Ontario

    NASA Astrophysics Data System (ADS)

    Welsh, Daniel James

    The distribution of radar-estimated precipitation from lake-effect snow bands over and downwind of Lake Ontario shows more snowfall in downwind areas than over the lake itself. Here we examine two non-exclusive processes contributing to this: the collapse of convection that lofts hydrometeors over the lake and allows then to settle them downwind, and stratiform ascent over land, due to surface cooling, frictional convergence, and terrain, leading to more uniformly distributed precipitation there. The main data sources for this study are vertical profiles of radar reflectivity and hydrometeor vertical velocity in a well-defined, deep long-lake-axis-parallel band, observed on 11 December, 2013 during the Ontario Winter Lake-effect Systems (OWLeS) project. The profiles are derived from an airborne W-band Doppler radar, as well as an array of four Ka-band radars, a X-band profiling radar, a scanning X-band radar, and a scanning S-band radar. The presence of convection offshore is evident from deep, strong (up to 10 m s-1) updrafts producing bounded weak-echo regions and locally heavily rimed snow particles. The decrease of the standard deviation, skewness, and peak values of Doppler vertical velocity during the downwind shore crossing is consistent with the convection collapse hypothesis. Consistent with the stratiform ascent hypothesis are (a) an increase in mean vertical velocity over land; and (b) an increasing abundance of large snowflakes at low levels and over land, due to depositional growth and aggregation, evident from flight-level and surface particle size distribution data, and from differences in reflectivity profiles from S, X, Ka, and W-band radars at nearly the same time and location.

  9. Algorithmic identification of limnological features in vertical profiles from the Great Lakes

    NASA Astrophysics Data System (ADS)

    Wietsma, T.; Collingsworth, P.; Minsker, B. S.

    2013-12-01

    High volume collection of environmental data in digital format presents a range of challenges for the researcher, from quality control and data management to efficient interpretation of the signal and the development of requisite information technology skills. These challenges have been termed the "data deluge". To aid in efficient data interpretation, we describe several algorithmic approaches for feature identification in signal streams, including gradient estimation, spectral analysis, and the hidden Markov model. These approaches are calibrated and evaluated over vertical temperature profiles from the Great Lakes obtained through the U.S. Environmental Protection Agency. To demonstrate the value of this data science approach, we describe how the algorithms can be integrated with the historical sampling record to yield an expert system that assists field technicians with adaptive sampling.

  10. Empirical evaluation of predator-driven diel vertical migration in Lake Superior

    USGS Publications Warehouse

    Stockwell, J.D.; Hrabik, T.R.; Jensen, O.P.; Yule, D.L.; Balge, M.

    2010-01-01

    Recent studies on Lake Superior suggest that diel vertical migration (DVM) of prey (generalized Coregonus spp.) may be influenced by the density of predatory siscowet (Salvelinus namaycush). We empirically evaluated this hypothesis using data from acoustic, midwater trawl, and bottom trawl sampling at eight Lake Superior sites during three seasons in 2005 and a subset of sites in 2006. We expected the larger-bodied cisco (Coregonus artedi) to exhibit a shallower DVM compared with the smaller-bodied kiyi (Coregonus kiyi). Although DVM of kiyi and cisco were consistent with expectations of DVM as a size-dependent, predator-mediated process, we found no relationship between siscowet density and the magnitude of DVM of either coregonid. Cisco appear to have a size refuge from siscowet predation. Kiyi and siscowet co-occur in demersal habitat > 150 m during the day, where visual predation is unlikely, suggesting predator avoidance is not a factor in the daytime distribution of kiyi. Seasonal patterns of kiyi DVM were consistent with reported DVM of their primary prey Mysis relicta. Our results suggest that consideration of nonvisual foraging, rather than lightbased foraging theory (i.e., the antipredation window), is necessary to understand the processes driving DVM in deepwater systems.

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

    USGS Publications Warehouse

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

    2012-01-01

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

  12. Vertical stratification of bacteria and archaea in sediments of a boreal stratified humic lake

    NASA Astrophysics Data System (ADS)

    Rissanen, Antti J.; Mpamah, Promise; Peura, Sari; Taipale, Sami; Biasi, Christina; Nykänen, Hannu

    2015-04-01

    Boreal stratified humic lakes, with steep redox gradients in the water column and in the sediment, are important sources of methane (CH4) to the atmosphere. CH4 flux from these lakes is largely controlled by the balance between CH4-production (methanogenesis), which takes place in the organic rich sediment and in the deepest water layers, and CH4-consumption (methanotrophy), which takes place mainly in the water column. While there is already some published information on the activity, diversity and community structure of bacteria in the water columns of these lakes, such information on sediment microbial communities is very scarce. This study aims to characterize the vertical variation patterns in the diversity and the structure of microbial communities in sediment of a boreal stratified lake. Particular focus is on microbes with the potential to contribute to methanogenesis (fermentative bacteria and methanogenic archaea) and to methanotrophy (methanotrophic bacteria and archaea). Two sediment cores (26 cm deep), collected from the deepest point (~6 m) of a small boreal stratified lake during winter-stratification, were divided into depth sections of 1 to 2 cm for analyses. Communities were studied from DNA extracted from sediment samples by next-generation sequencing (Ion Torrent) of polymerase chain reaction (PCR) - amplified bacterial and archaeal 16S rRNA gene amplicons. The abundance of methanogenic archaea was also specifically studied by quantitative-PCR of methyl coenzyme-M reductase gene (mcrA) amplicons. Furthermore, the community structure and the abundance of bacteria were studied by phospholipid fatty acid (PLFA) analysis. Dominant potential fermentative bacteria belonged to families Syntrophaceae, Clostridiaceae and Peptostreptococcaceae. There were considerable differences in the vertical distribution among these groups. The relative abundance of Syntrophaceae started to increase from the sediment surface, peaked at depth layer from 5 to 10 cm (up

  13. Diel Variations in the Vertical Distribution of Crustacean Zooplankton and Food Selection by Planktivorous Fish in a Shallow Turbid Lake

    NASA Astrophysics Data System (ADS)

    Alajärvi, Erika; Horppila, Jukka

    2004-07-01

    The variations in the vertical migrations by zooplankton and food composition of fish in the shallow, clay-turbid Mustionselkä basin of Lake Hiidenvesi were studied (water depth 3 m). Daphnids showed signs of reverse migration, their density in the surface layer being highest during the day. The reverse migration was probably due to predation threat by the predatory cladoceran Leptodora kindtii. Chydorus sphaericus, which was consumed especially by the day active bleak (Alburnus alburnus), showed normal vertical migration. Copepods showed no clear vertical movements. Leptodora kindtii, as well as the large herbivore Limnosida frontosa, showed no vertical migrations, but their overall abundance increased considerably during the night, indicating horizontal movement towards the open water at night. Due to the shallowness of the water, vertical migrations may not be a good predator-avoidance strategy for the largest cladocerans, which may be able to perform horizontal migrations. (

  14. Vertical distribution of fish biomass in Lake Superior: Implications for day bottom trawl surveys

    USGS Publications Warehouse

    Stockwell, J.D.; Yule, D.L.; Hrabik, T.R.; Adams, J.V.; Gorman, O.T.; Holbrook, B.V.

    2007-01-01

    Evaluation of the biases in sampling methodology is essential for understanding the limitations of abundance and biomass estimates of fish populations. Estimates from surveys that rely solely on bottom trawls may be particularly vulnerable to bias if pelagic fish are numerous. We evaluated the variability in the vertical distribution of fish biomass during the U.S. Geological Survey's annual spring bottom trawl survey of Lake Superior using concurrent hydroacoustic observations to (1) test the assumption that fish are generally demersal during the day and (2) evaluate the potential for predictive models to improve bottom trawl–determined biomass estimates. Our results indicate that the assumption that fish exhibit demersal behavior during the annual spring bottom trawl survey in Lake Superior is unfounded. Bottom trawl biomass (BBT) estimates (mean ± SE) for species known to exhibit pelagic behavior (cisco Coregonus artedi, bloater C. hoyi, kiyi C. kiyi, and rainbow smelt Osmerus mordax; 3.01 ± 0.73 kg/ha) were not significantly greater than mean acoustic pelagic zone biomass (BAPZ) estimates (6.39 ± 2.03 kg/ha). Mean BAPZ estimates were 1.6- to 4.8-fold greater than mean BBT estimates over 4 years of sampling. The relationship between concurrent BAPZ and BBT estimates was marginally significant and highly variable. Predicted BAPZ estimates using cross-validation models were sensitive to adjustments for back-transforming from the logarithmic to the linear scale and poorly corresponded to observed BAPZ estimates. We conclude that statistical models to predict BAPZ from day BBT cannot be developed. We propose that night sampling with multiple gears will be necessary to generate better biomass estimates for management needs.

  15. Can small zooplankton enhance turbulence in a lake during vertical migration?

    NASA Astrophysics Data System (ADS)

    Wain, D.; Simoncelli, S.; Thackeray, S.

    2016-02-01

    Recent research in both oceanic and freshwater systems suggests that the Diel Vertical Migration (DVM), a predator-avoidance mechanism adopted by many zooplankton, may be an underrepresented source of turbulence and mixing. In particular, the migration can play a crucial role when organisms cross the thermocline; this could be particularly important in enhancing the mixing in lakes, where the pelagic zone is often quiescent, with a consequent impact on lake ecosystem functioning. A field experiment was performed to directly measure the temperature fluctuations and kinetic energy dissipation rate generated by DVM of Daphnia spp., a 1 mm crustacean zooplankton genus. Profiles of turbulence were acquired with a temperature microstructure profiler in Vobster Quay (UK), a small quarry with small wind fetch, steep sides, and with a maximum depth of approximately 25 m. Sixteen profiles were measured over the course of two hours during sunset on 16 July 2015, during which there was no wind. Backscatter strength from bottom-mounted ADCP was used as a proxy to assess DVM. Zooplankton vertical distribution was also quantified by sampling with a 100 μm mesh net before and after the turbulence profiling in 8 layers to verify the distribution of Daphnia spp. before and after the migration. Zooplankton tows show higher abundance (450 ind./L) of Daphnia at 9m and near the bottom before sunset (8PM). Samples after dusk (11.20PM) showed an increase in the surface layer, from 0 up to 250 ind./L. However, migration also appears to happen horizontally. Ensemble-averaged profiles show a great variation of the dissipation rates over the course of the time series with a peak of 10-7 W/kg between 6m and 12m where the DVM is happening and with respect to profiles before sunset. Given the uncertainty in measuring the length scales of turbulence associated with small zooplankton, further analysis is required to determine if the observed turbulence during the time of migration was due the

  16. Removal of nutrients from combined sewer overflows and lake water in a vertical-flow constructed wetland system.

    PubMed

    Gervin, L; Brix, H

    2001-01-01

    Lake Utterslev is situated in a densely built-up area of Copenhagen, and is heavily eutrophicated from combined sewer overflows. At the same time the lake suffers from lack of water. Therefore, a 5,000 m2 vertical flow wetland system was constructed in 1998 to reduce the phosphorus discharge from combined sewer overflows without reducing the water supply to the lake. During dry periods the constructed wetland is used to remove phosphorus from the lake water. The system is designed as a 90 m diameter circular bed with a bed depth of c. 2 m. The system is isolated from the surroundings by a polyethylene membrane. The bed medium consists of a mixture of gravel and crushed marble, which has a high binding capacity for phosphorus. The bed is located within the natural littoral zone of the lake and is planted with common reed (Phragmites australis). The constructed wetland is intermittently loaded with combined sewer overflow water or lake water and, after percolation through the bed medium, the water is collected in a network of drainage pipes at the bottom of the bed and pumped to the lake. The fully automated loading cycle results in alternating wet and dry periods. During the initial two years of operation, the phosphorus removal for combined sewer overflows has been consistently high (94-99% of inflow concentrations). When loaded with lake water, the phosphorus removal has been high during summer (71-97%) and lower during winter (53-75%) partly because of lower inlet concentrations. Effluent phosphorus concentrations are consistently low (0.03-0.04 mg/L). Ammonium nitrogen is nitrified in the constructed wetland, and total suspended solids and COD are generally reduced to concentrations below 5 mg/L and 25 mg/L, respectively. The study documents that a subsurface flow constructed wetland system can be designed and operated to effectively remove phosphorus and other pollutants from combined sewer overflows and eutrophicated lake water.

  17. Vertical profiles of water and sediment denitrifiers in two plateau freshwater lakes.

    PubMed

    Mao, Guozhu; Chen, Ling; Yang, Yuyin; Wu, Zhen; Tong, Tianli; Liu, Yong; Xie, Shuguang

    2017-04-01

    The present study investigated the abundance, richness, diversity, and community composition of denitrifiers (based on nirS and nosZ genes) in the stratified water columns and sediments in eutrophic Dianchi Lake and mesotrophic Erhai Lake using quantitative PCR assay and high-throughput sequencing analysis. Both nirS- and nosZ denitrifiers were detected in waters of these two lakes. Surface water showed higher nosZ gene density than bottom water, and Dianchi Lake waters had larger nirS gene abundance than Erhai Lake waters. The abundance of sediment nirS- and nosZ denitrifiers in Dianchi Lake was larger than that in Erhai Lake. nirS richness and diversity and nosZ richness tended to increase with increasing sediment layer depth in both lakes. The distinct structure difference of sediment nirS- and nosZ denitrifier communities was found between in Dianchi Lake and Erhai Lake. These two lakes also differed greatly in water denitrifier community structure. Moreover, phylogenetic analysis indicated the presence of several different groups of nirS- or nosZ denitrifiers in both lakes. The novel nirS denitrifiers were abundant in both Dianchi Lake and Erhai Lake, while most of the obtained nosZ sequences could be affiliated with known genera.

  18. Vertical distribution of sediment phosphorus in Lake Hachirogata related to the effect of land reclamation on phosphorus accumulation.

    PubMed

    Jin, G; Onodera, S; Saito, M; Maruyama, Y; Hayakawa, A; Sato, T; Ota, Y; Aritomi, D

    2016-01-13

    The focus of this work is the change in sediment properties and chemical characteristics that occur after land reclamation projects. The results indicate a higher sedimentation rate in Lake Hachirogata after reclamation, with the rate increasing with proximity to the agricultural zone. In the west-side water samples, higher levels of dissolved total nitrogen and dissolved total phosphorus (DTP) were found in both surface and bottom waters. The increase in P (39-80%) was generally greater than that for N (12-16%), regarding the nutrient supply from reclaimed farmland in the western part of the lake. In the eastern part of the lake, the pore-water Cl(-) profile showed a decreasing vertical gradient in the sediment core. This indicates desalination of the lake water after construction of a sluice gate in 1961. In the western sediment-core sample, a uniform Cl(-) profile indicates the mixing of lake water and pore water after reclamation. Considering the sedimentation of P in the last 100 years, there is a trend of increasing accumulation of P and P-activities after the reclamation project. This appears to be an impact from change in the lake environment as a result of increased agricultural nutrients, desalination, and residence. A large amount of mobile phosphorus (42-72% of TP in the western core sample) trapped in sediment increases the risk of phosphorus release and intensification of algal blooms. High sediment phosphorus and phosphorus mobility should be considered a source of pollution in the coastal environment.

  19. The vertical migration of Mysis relicta in Lakes Huron and Michigan

    USGS Publications Warehouse

    Beeton, Alfred M.

    1960-01-01

    During the day Mysis relicta could be taken only near the bottom of Lakes Huron and Michigan. In the evening they migrated into the overlying strata as the surface light intensity decreased from 15 to 1 foot-candles. Frequently the mysids migrated through the metalimnion when first ascending, but later in the night the majority occurred in or immediately below this layer. As the length of day decreased following the summer solstice, the mysids ascended progressively earlier each evening and descended later each morning (they descended when the surface light intensity was increasing from 10−3 to 10−2 foot-candle). Moonlight and fog influenced the extent and time of vertical migration.The optimum light intensity for mysids is so low that they are concentrated near the bottom during the day. As the light decreases at sunset, they move upward rapidly; possibly because of a positive reaction to decreasing light. Their night-time distribution is determined by their response to the existing light and thermal conditions. Their dawn descent may be due to a photo-negative condition which originated during the night.

  20. Holocene Full-Vector Secular Variation from African Lakes

    NASA Astrophysics Data System (ADS)

    Lund, S.; Platzman, E. S.; Johnson, T. C.; Scholz, C. A.; Cohen, A. S.; Russell, J. M.

    2014-12-01

    We are developing a regional pattern of Holocene paleomagnetic secular variation (PSV) from four lakes in East Africa - Lake Turkana (3°N), Lake Victoria (1°S), Lake Tanganyika (5°S), and Lake Malawi (10°S). Detailed paleomagnetic and rock magnetic measurements have been made on two cores from Lake Malawi (9m meters in depth, last ~10,000 years), two cores from Lake Victoria (8 m, last ~8,000 years), 11 cores from Lake Turkana (2-9 m, last ~10,000 years), and one core from Lake Tanganyika (5 m, last ~5,000 years). Our rock magnetic studies identify significant intervals of magnetic mineral dissolution in Lakes Victoria and Tanganyika making parts of these cores unsuitable for relative paleointensity studies. On the other hand, rock magnetic variability in the Lake Malawi and Lake Turkana cores are stable and correlatable among cores. We have recovered directional secular variation records from Lakes Malawi, Victoria, and Turkana. Millennial-scale inclination and declination features can be correlated among cores at each lake and between lakes. We have also recovered relative paleointensity records from Lakes Malawi and Turkana. More than 20 radiocarbon dates and detailed seismic stratigraphy (Turkana) provide critical added information for correlating and dating the paleomagnetic records.

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

    NASA Astrophysics Data System (ADS)

    Makino, Wataru; Ban, Syuhei

    1998-06-01

    The vertical distribution of Cyclops strenuus and its prey, and the gut contents of C. strenuus were investigated at 3 h intervals over 24 h periods in the pelagic area of oligotrophic Lake Toya in May, August and October 1992. C. strenuus showed slight diel vertical migration (DVM) in May, but did not migrate and was always distributed below 15 m in August and October, the thermally stratified period. This suggests that the DVM is strongly influenced by the development of the thermocline, which the copepod may not be able to cross. Gut content analyses revealed that in Lake Toya it is omnivorous, and that the dominant prey are cladocerans and Filinia longiseta. The number of prey remains in the gut varied with time, and the diel changes did not follow changes in prey density that take the vertical overlap between predator and prey into account. We argue that very low prey density associated with the oligotrophic nature of the lake would mask the relationship between prey density and the number of prey in the gut of the predator.

  2. Seasonally dynamic diel vertical migrations of Mysis diluviana, coregonine fishes, and siscowet lake trout in the pelagia of western Lake Superior

    USGS Publications Warehouse

    Ahrenstorff, Tyler D.; Hrabik, Thomas R.; Stockwell, Jason D.; Yule, Daniel L.; Sass, Greg G.

    2011-01-01

    Diel vertical migrations are common among many aquatic species and are often associated with changing light levels. The underlying mechanisms are generally attributed to optimizing foraging efficiency or growth rates and avoiding predation risk (μ). The objectives of this study were to (1) assess seasonal and interannual changes in vertical migration patterns of three trophic levels in the Lake Superior pelagic food web and (2) examine the mechanisms underlying the observed variability by using models of foraging, growth, and μ. Our results suggest that the opossum shrimp Mysis diluviana, kiyi Coregonus kiyi, and siscowet lake trout Salvelinus namaycush migrate concurrently during each season, but spring migrations are less extensive than summer and fall migrations. In comparison with M. diluviana, kiyis, and siscowets, the migrations by ciscoes C. artedi were not as deep in the water column during the day, regardless of season. Foraging potential and μ probably drive the movement patterns of M. diluviana, while our modeling results indicate that movements by kiyis and ciscoes are related to foraging opportunity and growth potential and receive a lesser influence from μ. The siscowet is an abundant apex predator in the pelagia of Lake Superior and probably undertakes vertical migrations in the water column to optimize foraging efficiency and growth. The concurrent vertical movement patterns of most species are likely to facilitate nutrient transport in this exceedingly oligotrophic ecosystem, and they demonstrate strong linkages between predators and prey. Fishery management strategies should use an ecosystem approach and should consider how altering the densities of long-lived top predators produces cascading effects on the nutrient cycling and energy flow in lower trophic levels.

  3. Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment.

    PubMed

    Wurzbacher, Christian; Fuchs, Andrea; Attermeyer, Katrin; Frindte, Katharina; Grossart, Hans-Peter; Hupfer, Michael; Casper, Peter; Monaghan, Michael T

    2017-04-08

    Lake sediments harbor diverse microbial communities that cycle carbon and nutrients while being constantly colonized and potentially buried by organic matter sinking from the water column. The interaction of activity and burial remained largely unexplored in aquatic sediments. We aimed to relate taxonomic composition to sediment biogeochemical parameters, test whether community turnover with depth resulted from taxonomic replacement or from richness effects, and to provide a basic model for the vertical community structure in sediments. We analyzed four replicate sediment cores taken from 30-m depth in oligo-mesotrophic Lake Stechlin in northern Germany. Each 30-cm core spanned ca. 170 years of sediment accumulation according to (137)Cs dating and was sectioned into layers 1-4 cm thick. We examined a full suite of biogeochemical parameters and used DNA metabarcoding to examine community composition of microbial Archaea, Bacteria, and Eukaryota. Community β-diversity indicated nearly complete turnover within the uppermost 30 cm. We observed a pronounced shift from Eukaryota- and Bacteria-dominated upper layers (<5 cm) to Bacteria-dominated intermediate layers (5-14 cm) and to deep layers (>14 cm) dominated by enigmatic Archaea that typically occur in deep-sea sediments. Taxonomic replacement was the prevalent mechanism in structuring the community composition and was linked to parameters indicative of microbial activity (e.g., CO2 and CH4 concentration, bacterial protein production). Richness loss played a lesser role but was linked to conservative parameters (e.g., C, N, P) indicative of past conditions. By including all three domains, we were able to directly link the exponential decay of eukaryotes with the active sediment microbial community. The dominance of Archaea in deeper layers confirms earlier findings from marine systems and establishes freshwater sediments as a potential low-energy environment, similar to deep sea sediments. We propose a general model

  4. Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids

    PubMed Central

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2015-01-01

    Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution. PMID:25948565

  5. Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids.

    PubMed

    Tsuboi, Masahito; Gonzalez-Voyer, Alejandro; Kolm, Niclas

    2015-05-01

    Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution.

  6. Preliminary Vertical Slip Rate for the West Tahoe Fault from six new Cosmogenic 10Be Exposure Ages of Late Pleistocene Glacial Moraines at Cascade Lake, Lake Tahoe, California

    NASA Astrophysics Data System (ADS)

    Pierce, I. K. D.; Wesnousky, S. G.; Kent, G. M.; Owen, L. A.

    2015-12-01

    The West Tahoe Fault is the primary range bounding fault of the Sierra Nevada at the latitude of Lake Tahoe. It is a N-NW striking, east dipping normal fault that has a pronounced onshore quaternary scarp extending from highway 50 southwest of Meyers, CA to Emerald Bay. At Cascade Lake, the fault cuts and progressively offsets late Pleistocene right lateral moraines. The fault vertically offsets the previously mapped Tahoe moraine ~83 m and the Tioga moraine ~23 m, measured from lidar data. Seventeen samples were collected for 10Be cosmogenic age analysis from boulders on both the hanging and footwalls of the fault along the crests of these moraines.We report here the initial analysis of 6 of these boulders and currently await processing of the remainder. The 10Be exposure ages of 3 boulders each on the younger Tioga and older Tahoe moraines range from 12.7 +/- 1.6 to 20.7 +/- 3.3 ka and 13.3 +/- 2.1 to 72.5 +/- 8.8 ka, respectively. Using the oldest ages as minima, these preliminary results suggest that the slip rate has averaged ~1 mm/yr since the penultimate glaciation, in accord with estimates of previous workers, and place additional bounds on the age of glaciation in the Lake Tahoe basin. The Last Glacial Maxima and penultimate glaciation near Lake Tahoe thus appear to coincide with the Tioga and Tahoe II glaciations of the Eastern Sierra.

  7. Vertical structure and horizontal variations in the cycling of methane in the sediment of Lake Onego, Russia

    NASA Astrophysics Data System (ADS)

    Thomas, Camille; Perga, Marie-Elodie; Frossard, Victor; Pasche, Natacha; Hofmann, Hilmar; Ariztegui, Daniel; Dubois, Nathalie; Belkina, Natalya; Lyautey, Emilie

    2017-04-01

    Lake Onego, the second largest lake in Europe, is a dystrophic, seasonally ice-covered lake in Karelia, Russia. Like most winter-covered lakes, its study has largely been limited to the summer period. However, it is well known that methane production is still ongoing in lake sediments during winter, potentially resulting in accumulation and major release upon thawing. Within the "Life Under The Ice" research project, our objectives were to assess winter contribution to the annual methane flux in Lake Onego, and to understand conditions and factors influencing methane cycling. During two on-ice field campaigns in March 2015 and 2016, sediment cores were retrieved at different sites of Petrozavodsk Bay, located in the north-western part of the lake. DNA and RNA were extracted from these cores to investigate the functional structure of microbial communities. Genes involved in methanogenesis, anaerobic and aerobic methane oxidations were quantified along with the concentrations and isotopic ratio of methane in the sediment pore water. Incubations, fingerprinting and sequencing of mcrA genes were also realized. Vertically, the sediment is structured in a deep anoxic zone (below 10 cm) where mcrA gene and transcript copies increased implying methanogenesis, a transitional zone (5-8 cm) hosting methanotrophic organisms (Cand. Methanoperedens) able to oxidize the diffusing methane anaerobically by coupling nitrate reduction (Haroon et al., 2013), and a shallower oxic zone where methanotrophs were detected (pmoA gene and transcripts) and where methane concentrations drop below detection limit. Sediment cores were also collected at three sites along a transect from the mouth of the river Shuya (the major inflow to the bay) to the open lake. Functional assemblage close to the river mouth had higher diversity and higher potential production rates and consumption of methane than further in the lake. However, the methane produced was almost completely consumed regardless of the

  8. Nocturnal Temporal and Vertical Variations of The Concentrations of Pollutants Induced By Thermally Driven Circulation Within The Salt Lake Valley

    NASA Astrophysics Data System (ADS)

    Alexandrova, O.; Anderson, J. R.; Boyer, D. L.; Fernando, H. J. S.

    The study of the temporal and vertical distribution of aerosol concentrations in the Salt Lake Valley was carried out as a part of the Vertical Transport and Mixing (VTMX) Experiment conducted in Salt Lake City, Utah. The PM10 (particulate matter 0.1-10 mkm in aerodynamic diameter) measurements were made using DustTrak during the period of October 1-18, 2000. Temporal variation of the PM10 concentration at the ground level exhibited a diurnal pattern. Nocturnal period was characterized by 2-3 times lower aerosol concentrations than those found during the daytime. A katabatic flow advects cleaner air along the surface from mountain slopes toward the metropoli- tan area of Salt Lake City. One of the aspects of this katabatic flow is that intermittent peaks of the PM10 concentration are observed. Hypothesis is advanced that this may owe to eddies generated by a northwesterly flow past the basin scale topography. Bal- loon measurements of aerosol concentration up to 500 m showed a strong influence of multi-layer structure of the airflow on the vertical distribution of PM10. Along the sur- face the flow is an easterly drainage current with a return flow above. Westerly return flows were associated with enhanced PM10 concentrations while easterly currents led to reduced concentrations. Since aerosols are advected by return flow during the night and eventually are introduced into down-slope flow, this circulation leads to increase PM10 concentration in the downtown area in the early morning. Owing to the kata- batic winds originating at different levels at slopes of varying orientation a vertically skewed stratified shear flow cause the circulation of pollutants during the nighttime.

  9. Densities and Diel Vertical Migration of Mysis relicta in Lake Superior: A Comparison of Optical Plankton Encounter and Net-based Approaches

    EPA Science Inventory

    In this study, we used data from an OPC, and LOPC, and vertical net tows to estimate densities and describe the day/night vertical distribution of Mysis at a series of stations distributed throughout Lake Superior, and to evaluate the efficacy of using (L)OPC for examining DVM of...

  10. Densities and Diel Vertical Migration of Mysis relicta in Lake Superior: A Comparison of Optical Plankton Encounter and Net-based Approaches

    EPA Science Inventory

    In this study, we used data from an OPC, and LOPC, and vertical net tows to estimate densities and describe the day/night vertical distribution of Mysis at a series of stations distributed throughout Lake Superior, and to evaluate the efficacy of using (L)OPC for examining DVM of...

  11. Vertical distribution of Fe and Fe(III)-reducing bacteria in the sediments of Lake Donghu, China.

    PubMed

    Tian, Cuicui; Wang, Chunbo; Tian, Yingying; Wu, Xingqiang; Xiao, Bangding

    2015-08-01

    In lake sediments, iron (Fe) is the most versatile element, and the redox cycling of Fe has a wide influence on the biogeochemical cycling of organic and inorganic substances. The aim of the present study was to analyze the vertical distribution of Fe and Fe(III)-reducing bacteria (FeRB) in the surface sediment (30 cm) of Lake Donghu, China. At the 3 sites we surveyed, FeRB and Fe(II)-oxidizing bacteria (FeOB) coexisted in anoxic sediments. Geobacter-related FeRB accounted for 5%-31% of the total Bacteria, while Gallionella-related FeOB accounted for only 0.1%-1.3%. A significant correlation between the relative abundance of poorly crystalline Fe and Geobacter spp. suggested that poorly crystalline Fe favored microbial Fe(III) reduction. Poorly crystalline Fe and Geobacter spp. were significantly associated with solid-phase Fe(II) and total inorganic phosphorus levels. Pore water Fe(II) concentrations negatively correlated with NO3(-) at all sites. We concluded that Geobacter spp. were abundant in the sediments of Lake Donghu, and the redox of Fe might participate in the cycling of nitrogen and phosphorus in sediments. These observations provided insight into the roles of microbial Fe cycling in lake sediments.

  12. Vertical distribution of buoyant Microcystis blooms in a Lagrangian particle tracking model for short-term forecasts in Lake Erie

    NASA Astrophysics Data System (ADS)

    Rowe, M. D.; Anderson, E. J.; Wynne, T. T.; Stumpf, R. P.; Fanslow, D. L.; Kijanka, K.; Vanderploeg, H. A.; Strickler, J. R.; Davis, T. W.

    2016-07-01

    Cyanobacterial harmful algal blooms (CHABs) are a problem in western Lake Erie, and in eutrophic fresh waters worldwide. Western Lake Erie is a large (3000 km2), shallow (8 m mean depth), freshwater system. CHABs occur from July to October, when stratification is intermittent in response to wind and surface heating or cooling (polymictic). Existing forecast models give the present location and extent of CHABs from satellite imagery, then predict two-dimensional (surface) CHAB movement in response to meteorology. In this study, we simulated vertical distribution of buoyant Microcystis colonies, and 3-D advection, using a Lagrangian particle model forced by currents and turbulent diffusivity from the Finite Volume Community Ocean Model (FVCOM). We estimated the frequency distribution of Microcystis colony buoyant velocity from measured size distributions and buoyant velocities. We evaluated several random-walk numerical schemes to efficiently minimize particle accumulation artifacts. We selected the Milstein scheme, with linear interpolation of the diffusivity profile in place of cubic splines, and varied the time step at each particle and step based on the curvature of the local diffusivity profile to ensure that the Visser time step criterion was satisfied. Inclusion of vertical mixing with buoyancy significantly improved model skill statistics compared to an advection-only model, and showed greater skill than a persistence forecast through simulation day 6, in a series of 26 hindcast simulations from 2011. The simulations and in situ observations show the importance of subtle thermal structure, typical of a polymictic lake, along with buoyancy in determining vertical and horizontal distribution of Microcystis.

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

    PubMed

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

    2012-01-01

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

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

    PubMed Central

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

    2012-01-01

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

  15. Speciation in ancient lakes.

    PubMed

    Martens, K

    1997-05-01

    About a dozen lakes in the world are up to three orders of magnitude older than most others. Lakes Tanganyika (East Africa) and Baikal (Siberia) have probably existed in some form for 12-20 million years, maybe more. Such lakes can have different origins, sizes, shapes, depths and limnologies, but, in contrast to short-lived (mostly post-glacial) lakes, they have exceptionally high faunal diversity and levels of endemicity. A multitude of and processes accounting for these explosive radiations have recently been documented, most of them based on particular groups in certain lakes, but comparative research can detect repeated patterns. No special speciafion mechanism, exclusive to ancient lakes has been demonstrated, although cases of ultra-rapid speciation have been documented. Extant diversity results not by simple accumulation, but by a complex process of immigration, speciation and extinction.

  16. Vertical redistribution of zooplankton in an oligotrophic lake associated with reduction in ultraviolet radiation by wildfire smoke

    NASA Astrophysics Data System (ADS)

    Urmy, Samuel S.; Williamson, Craig E.; Leach, Taylor H.; Schladow, S. Geoffrey; Overholt, Erin P.; Warren, Joseph D.

    2016-04-01

    We used a natural experiment to test whether wildfire smoke induced changes in the vertical distribution of zooplankton in Lake Tahoe by decreasing incident ultraviolet radiation (UV). Fires have a variety of effects on aquatic ecosystems, but these impacts are poorly understood and have rarely been observed directly. UV is an important driver of zooplankton vertical migration, and wildfires may alter it over large spatial scales. We measured UV irradiance and the distribution of zooplankton on two successive days. On one day, smoke haze from a nearby wildfire reduced incident UV radiation by up to 9%, but not irradiance in the visible spectrum. Zooplankton responded by positioning themselves, on average, 4.1 m shallower in the lake. While a limited data set such as this requires cautious interpretation, our results suggest that smoke from wildfires can change the UV environment and distribution of zooplankton. This process may be important in drought-prone regions with increasingly frequent wildfires, and globally due to widespread biomass burning.

  17. Age-specific light preferences and vertical migration patterns of a Great Lakes invasive invertebrate, Hemimysis anomala

    USGS Publications Warehouse

    Boscarino, Brent T.; Halpin, Kathleen E.; Rudstam, Lars G.; Walsh, Maureen G.; Lantry, Brian F.

    2012-01-01

    We use a combination of spectral sensitivity analyses, laboratory behavioral observations and field distributions of a vertically migrating invertebrate, Hemimysis anomala (a recent invasive species to the Laurentian Great Lakes of North America), to determine if light preference and timing of emergence has an ontogenetic component. Juvenile Hemimysis (−3.4 and 10−2.4 mylux— a Hemimysis-specific unit of brightness derived from visual pigment analyses (wavelength of maximum absorbance = 500 nm; 1 mylux ~ 159 lx). These preferred light levels are equivalent to those present during nautical twilight on the Earth's surface and were several orders of magnitude brighter than those most preferred by adults (> 4.5 mm) in the laboratory (10−6.4 to 10−7.4 mylux). Both size classes completely avoided light levels of 10−0.4 mylux and greater, which are representative of daytime light levels at the Earth's surface. Net hauls taken at ~ 20-min intervals from sunset to the end of nautical twilight on two sampling occasions on Seneca Lake, New York (sampling depth = 2 m) revealed that juveniles emerged into the water column during civil twilight. Adult Hemimysis emerged later during nautical twilight when juveniles had already reached their maximum abundance in the water column. Laboratory-derived light preferences successfully predicted the timing of emergence and time of maximal abundance of both size classes on both sampling occasions. This study is one of the first to demonstrate that Hemimysis diel vertical migration has an ontogenetic component and to report the specific light levels likely to initiate and limit vertical movements.

  18. Development of a passive sensor for measuring vertical cumulative water and solute mass fluxes in lake sediments and streambeds

    NASA Astrophysics Data System (ADS)

    Layton, Leif; Klammler, Harald; Hatfield, Kirk; Cho, Jaehyun; Newman, Mark A.; Annable, Michael D.

    2017-07-01

    This paper introduces the sediment bed passive flux meter (SBPFM) as a new tool for in situ measurements of vertical volumetric water and contaminant mass fluxes across hyporheic and hypolentic zones (i.e., stream or lake bed sediments that function as the contiguous zone between the overlying surface water body and the underlying aquifer). The device is a direct-push probe which contains a permeable internal sorbent located between two screened intervals. In the presence of a vertical hydraulic gradient the screens allow water flow through the SBPFM's internal sorbent matrix that is impregnated with resident tracers. These tracers are displaced from the sorbent at rates proportional to the water flux through the sorbent. At the same time, dissolved contaminants present in the intercepted sediment water are retained on the SBPFM sorbent at rates proportional to the ambient contaminant mass flux in the hyporheic zone. Potential flow theory is applied to convert observations of water and contaminant fluxes through the SBPFM into estimates of undisturbed ambient vertical water and contaminant fluxes in the sediment. To validate the theory and demonstrate the SBPFM as a potential site characterization tool, multiple bench-scale sediment bed experiments are performed. Results demonstrate that water and contaminant mass fluxes are accurately measured in the laboratory and that future field tests are warranted.

  19. Ecophysiology of phototrophic sulfur bacteria in lakes: Vertical distribution of planktonic populations

    NASA Technical Reports Server (NTRS)

    Guerrero, R.

    1985-01-01

    The study of purple and green sulfur bacterial populations in nature is of interest for the following reasons: (1) high quantities of biomass, with low species diversity can be collected; (2) study of planktonic life permits one to understand the mechanisms, structural as well as physiological, used to maintain their vertical position without sinking; and (3) they are capable of sulfur oxidations and reductions that act as important intermediates in the global sulfur cycle. Purple and green photosynthetic bacteria, moreover, may be responsible for certain geological deposits. Planktonic phototrophic sulfur bacteria were analyzed in relation to their vertical distribution in the water column. Factors, including competition for light, that determine their sedimentation rates and the numerical changes in species and populations were assessed.

  20. Lake Ontario zooplankton in 2003 and 2008: Community changes and vertical redistribution

    USGS Publications Warehouse

    Rudstam, Lars G.; Holeck, Kristen T.; Bowen, Kelly L.; Watkins, James M.; Weidel, Brian C.; Luckey, Frederick J.

    2014-01-01

    Lake-wide zooplankton surveys are critical for documenting and understanding food web responses to ecosystem change. Surveys in 2003 and 2008 during the binational intensive field year in Lake Ontario found that offshore epilimnetic crustacean zooplankton declined by a factor of 12 (density) and factor of 5 (biomass) in the summer with smaller declines in the fall. These declines coincided with an increase in abundance of Bythotrephes and are likely the result of direct predation by, or behavioral responses to this invasive invertebrate predator. Whole water column zooplankton density also declined from 2003 to 2008 in the summer and fall (factor of 4), but biomass only declined in the fall (factor of 2). The decline in biomass was less than the decline in density because the average size of individual zooplankton increased. This was due to changes in the zooplankton community composition from a cyclopoid/bosminid dominated community in 2003 to a calanoid dominated community in 2008. The increase in calanoid copepods was primarily due to the larger species Limnocalanus macrurus and Leptodiaptomus sicilis. These cold water species were found in and below the thermocline associated with a deep chlorophyll layer. In 2008, most of the zooplankton biomass resided in or below the thermocline during the day. Increased importance of copepods in deeper, colder water may favor Cisco and Rainbow Smelt over Alewife because these species are better adapted to cold temperatures than Alewife.

  1. [Vertical distribution characteristics of organochlorine pesticides and polychlorinated biphenyls in sediment core from Lake Nansihu].

    PubMed

    Li, Hong-li; Li, Guo-gang; Yang, Fan; Gao, Hong; Gong, Zheng-yu; Zhu, Chen; Lian, Jun

    2007-07-01

    The organochlorinne pesticides (OCPs) and the polychlorinated biphenyls (PCBs) in sediment core collected from Lake Nansihu were quantificationally analyzed by GC-ECD. The pollution history of OCPs and PCBs in this area was reconstructed by analysis of the concentrations of OCPs and PCBs connected with the deposition time by 210Pb isotope dating method. The results indicated that the concentration ranges of OCPs, HCHs, DDTs and PCBs were 1.64 - 17.9, 0.66 - 12.5, 0.24 - 2.99 and 7.84 - 42.8 ng g(-1) respectively. The sediment rate and the average mass sedimentation were calculated to be 0.330 cm a(-1) and 0.237 g (cm2 a)(-1), and the sediment time of this core sample ranged from 1899 to 2000. OCPs and PCBs had the peak value at 1960s and 1970s. The source analysis showed HCH came from HCH products and lindane, and HCH and DDT came from historic using. The source of PCBs had been deduced to be the blench process of paper making and incinerator emission. Except the concentration of beta-HCH, gamma-HCH and aldrin at 14 - 16 cm depth, the other concentrations of OCPs and PCBs were all less than the low ecologic risk value. The whole sediment core of Lake Nansihu belonged to the low ecologic risk level.

  2. The vertical dynamics of larval chironomids on artificial substrates in lake lido (bogor, indonesia).

    PubMed

    Wardiatno, Yusli; Krisanti, Majariana

    2013-12-01

    The composition and abundance of chironomid larval communities was studied on artificial substrates in Lido Lake, located in Bogor, West Java, Indonesia. The lake is organically enriched as a result of fish farming activity. Seventy two artificial substrates were deployed at three depths (2.0, 3.5 and 5.0 m) at two sites: a cage culture site and a non-cage culture site (control). Larval chironomid larvae were collected 7, 14, 28 and 56 days after the artificial substrates were deployed. In addition, selected physical and chemical parameters of the water were simultaneously measured. Three chironomid subfamilies, the Chironominae, Tanypodinae and Orthocladiinae, were found at both sites. At the cage culture site, both diversity and total abundance were significantly higher at the 2.0 and 3.5 m depths than at the 5.0 m depth, but this was not the case at the non-cage culture site. Based on pooling of the data from all depths, a Mann-Whitney U test showed that the non-cage culture site had a significantly higher diversity and total abundance than the cage culture site. Dissolved oxygen (DO) and turbidity showed significant differences between the 2.0 m depth and the 2 greater depths at the cage culture site, whereas none of the environmental parameters showed significant differences among the three depths at the non-cage culture site. A comparison of the environmental parameters at the same depth at the two sites showed significant differences in turbidity, pH and DO. A Spearman rank correlation analysis at the cage culture site showed that abundance and DO were positively correlated, whereas abundance and turbidity were negatively correlated. However, only pH was negatively correlated with abundance at the non-cage culture site.

  3. Seasonal distribution, source investigation and vertical profile of phenolic endocrine disrupting compounds in Dianchi Lake, China.

    PubMed

    Wang, Bin; Huang, Bin; Jin, Wei; Wang, Yu; Zhao, Shimin; Li, Farong; Hu, Ping; Pan, Xuejun

    2012-04-01

    Phenolic endocrine disrupting compounds, including nonylphenol-di-ethoxylate (NP2EO), nonylphenol-mono-ethoxylate (NP1EO), 4-nonylphenol (4-NP), bisphenol A (BPA), 4-cumylphenol (4-CP) and 4-tert-octylphenol (4-t-OP), were investigated in water, surface sediment and sediment cores in Dianchi Lake to track their seasonal distributions, pollution sources and historical trends. The concentrations of NP2EO, NP1EO, 4-NP, BPA, 4-CP and 4-t-OP were up to 295.14, 448.48, 45.28, 530.33, 8.96 and 21.37 ng L(-1) in water, and up to 297.11, 809.63, 4.58, 166.87, 3.62 and 40.69 ng g(-1) dry weight in surface sediment, respectively. Except BPA in water, concentrations of all the other phenolic compounds in both of the matrices were higher in January than in July, 2011. The concentrations decreased significantly with an increase in distance from the sampling locations which were adjacent to the urban areas (Kunming City, Chenggong City and Jinning City). The pollution of phenolic EDCs came mainly from industry, agriculture and daily life. The relationships between the concentrations of target compounds and the six water quality parameters were evaluated. There were significant positive correlations between concentrations of phenolic compounds in water and in surface sediment. For sediment cores, three clearly separated maxima occurred in segments 0-5 cm (the late 2000s), 5-10 cm (the early and mid of 2000s) and 20-25 cm (the mid of 1980s), respectively. NP2EO, NP1EO and BPA were the three dominant compounds in the lake.

  4. The Vertical Dynamics of Larval Chironomids on Artificial Substrates in Lake Lido (Bogor, Indonesia)

    PubMed Central

    Wardiatno, Yusli; Krisanti, Majariana

    2013-01-01

    The composition and abundance of chironomid larval communities was studied on artificial substrates in Lido Lake, located in Bogor, West Java, Indonesia. The lake is organically enriched as a result of fish farming activity. Seventy two artificial substrates were deployed at three depths (2.0, 3.5 and 5.0 m) at two sites: a cage culture site and a non-cage culture site (control). Larval chironomid larvae were collected 7, 14, 28 and 56 days after the artificial substrates were deployed. In addition, selected physical and chemical parameters of the water were simultaneously measured. Three chironomid subfamilies, the Chironominae, Tanypodinae and Orthocladiinae, were found at both sites. At the cage culture site, both diversity and total abundance were significantly higher at the 2.0 and 3.5 m depths than at the 5.0 m depth, but this was not the case at the non-cage culture site. Based on pooling of the data from all depths, a Mann-Whitney U test showed that the non-cage culture site had a significantly higher diversity and total abundance than the cage culture site. Dissolved oxygen (DO) and turbidity showed significant differences between the 2.0 m depth and the 2 greater depths at the cage culture site, whereas none of the environmental parameters showed significant differences among the three depths at the non-cage culture site. A comparison of the environmental parameters at the same depth at the two sites showed significant differences in turbidity, pH and DO. A Spearman rank correlation analysis at the cage culture site showed that abundance and DO were positively correlated, whereas abundance and turbidity were negatively correlated. However, only pH was negatively correlated with abundance at the non-cage culture site. PMID:24575246

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

    NASA Astrophysics Data System (ADS)

    Bissinger, Vera

    2003-04-01

    In this thesis, I investigated the factors influencing the growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2-3). In the focal study site, Lake 111 (pH 2.7; Lusatia, Germany), the chrysophyte, Ochromonas sp., dominates in the upper water strata and the chlorophyte, Chlamydomonas sp., in the deeper strata, forming a pronounced deep chlorophyll maximum (DCM). Inorganic carbon (IC) limitation influenced the phototrophic growth of Chlamydomonas sp. in the upper water strata. Conversely, in deeper strata, light limited its phototrophic growth. When compared with published data for algae from neutral lakes, Chlamydomonas sp. from Lake 111 exhibited a lower maximum growth rate, an enhanced compensation point and higher dark respiration rates, suggesting higher metabolic costs due to the extreme physico-chemical conditions. The photosynthetic performance of Chlamydomonas sp. decreased in high-light-adapted cells when IC limited. In addition, the minimal phosphorus (P) cell quota was suggestive of a higher P requirement under IC limitation. Subsequently, it was shown that Chlamydomonas sp. was a mixotroph, able to enhance its growth rate by taking up dissolved organic carbon (DOC) via osmotrophy. Therefore, it could survive in deeper water strata where DOC concentrations were higher and light limited. However, neither IC limitation, P availability nor in situ DOC concentrations (bottom-up control) could fully explain the vertical distribution of Chlamydomonas sp. in Lake 111. Conversely, when a novel approach was adopted, the grazing influence of the phagotrophic phototroph, Ochromonas sp., was found to exert top-down control on its prey (Chlamydomonas sp.) reducing prey abundance in the upper water strata. This, coupled with the fact that Chlamydomonas sp. uses DOC for growth, leads to a pronounced accumulation of Chlamydomonas sp. cells at depth; an apparent DCM. Therefore, grazing appears to be the main factor influencing the

  6. 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…

  7. Direct and indirect effects of vertical mixing, nutrients and ultraviolet radiation on the bacterioplankton metabolism in high-mountain lakes from southern Europe

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    As a consequence of global change, modifications in the interaction among abiotic stressors on aquatic ecosystems have been predicted. Among other factors, UVR transparency, nutrient inputs and shallower epilimnetic layers could alter the trophic links in the microbial food web. Currently, there are some evidences of higher sensitiveness of aquatic microbial organisms to UVR in opaque lakes. Our aim was to assess the interactive direct and indirect effects of UVR (through the excretion of organic carbon - EOC - by algae), mixing regime and nutrient input on bacterial metabolism. We performed in situ short-term experiments under the following treatments: full sunlight (UVR + PAR, >280 nm) vs. UVR exclusion (PAR only, >400 nm); ambient vs. nutrient addition (phosphorus (P; 30 μg PL-1) and nitrogen (N; up to final N : P molar ratio of 31)); and static vs. mixed regime. The experiments were conducted in three high-mountain lakes of Spain: Enol [LE], Las Yeguas [LY] and La Caldera [LC] which had contrasting UVR transparency characteristics (opaque (LE) vs. clear lakes (LY and LC)). Under ambient nutrient conditions and static regimes, UVR exerted a stimulatory effect on heterotrophic bacterial production (HBP) in the opaque lake but not in the clear ones. Under UVR, vertical mixing and nutrient addition HBP values were lower than under the static and ambient nutrient conditions, and the stimulatory effect that UVR exerted on HBP in the opaque lake disappeared. By contrast, vertical mixing and nutrient addition increased HBP values in the clear lakes, highlighting for a photoinhibitory effect of UVR on HBP. Mixed regime and nutrient addition resulted in negative effects of UVR on HBP more in the opaque than in the clear lakes. Moreover, in the opaque lake, bacterial respiration (BR) increased and EOC did not support the bacterial carbon demand (BCD). In contrast, bacterial metabolic costs did not increase in the clear lakes and the increased nutrient availability even

  8. Vertical Distribution of Functional Potential and Active Microbial Communities in Meromictic Lake Kivu.

    PubMed

    İnceoğlu, Özgul; Llirós, Marc; Crowe, Sean A; García-Armisen, Tamara; Morana, Cedric; Darchambeau, François; Borges, Alberto V; Descy, Jean-Pierre; Servais, Pierre

    2015-10-01

    The microbial community composition in meromictic Lake Kivu, with one of the largest CH4 reservoirs, was studied using 16S rDNA and ribosomal RNA (rRNA) pyrosequencing during the dry and rainy seasons. Highly abundant taxa were shared in a high percentage between bulk (DNA-based) and active (RNA-based) bacterial communities, whereas a high proportion of rare species was detected only in either an active or bulk community, indicating the existence of a potentially active rare biosphere and the possible underestimation of diversity detected when using only one nucleic acid pool. Most taxa identified as generalists were abundant, and those identified as specialists were more likely to be rare in the bulk community. The overall number of environmental parameters that could explain the variation was higher for abundant taxa in comparison to rare taxa. Clustering analysis based on operational taxonomic units (OTUs at 0.03 cutoff) level revealed significant and systematic microbial community composition shifts with depth. In the oxic zone, Actinobacteria were found highly dominant in the bulk community but not in the metabolically active community. In the oxic-anoxic transition zone, highly abundant potentially active Nitrospira and Methylococcales were observed. The co-occurrence of potentially active sulfur-oxidizing and sulfate-reducing bacteria in the anoxic zone may suggest the presence of an active yet cryptic sulfur cycle.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    Global change, together with human activities, has resulted in increasing amounts of organic material (including nutrients) that water bodies receive. This input further attenuates the penetration of solar radiation, leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, for which the effects have, in general, been neglected. Furthermore, the combined impacts of mixing, together with those of UVR and nutrient inputs are virtually unknown. In this study, we carried out complex in situ experiments in three high mountain lakes of Spain (Lake Enol in the National Park Picos de Europa, Asturias, and lakes Las Yeguas and La Caldera in the National Park Sierra Nevada, Granada), used as model ecosystems to evaluate the joint impact of these climate change variables. The main goal of this study was to address the question of how short-term pulses of nutrient inputs, together with vertical mixing and increased UVR fluxes modify the photosynthetic responses of phytoplankton. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR + PAR (280-700 nm) versus PAR (photosynthetically active radiation) alone (400-700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 μg P L-1, and N to reach N:P molar ratio of 31); and (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m 4 min-1, total of 10 cycles)) versus static. Our findings suggest that under ambient nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and excretion of organic carbon (EOC) from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where

  10. The Vertical Distribution of Sediment Archaeal Community in the “Black Bloom” Disturbing Zhushan Bay of Lake Taihu

    PubMed Central

    Fan, Xianfang; Xing, Peng

    2016-01-01

    Using the Illumina sequencing technology, we investigated the vertical distribution of archaeal community in the sediment of Zhushan Bay of Lake Taihu, where the black bloom frequently occurred in summer. Overall, the Miscellaneous Crenarchaeotal Group (MCG), Deep Sea Hydrothermal Vent Group 6 (DHVEG-6), and Methanobacterium dominated the archaeal community. However, we observed significant difference in composition of archaeal community among different depths of the sediment. DHVEG-6 dominated in the surface layer (0–3 cm) sediment. Methanobacterium was the dominating archaeal taxa in the L2 (3–6 cm) and L3 (6–10) sediment. MCG was most abundant in the L4 (10–15 cm) and L5 (15–20 cm) sediment. Besides, DHVEG-6 was significantly affected by the concentration of total phosphorus (TP). And loss on ignition (LOI) was an important environmental factor for Methanobacterium. As the typical archaeal taxa in the surface layer sediment, DHVEG-6 and Methanobacterium might be more adapted to abundant substrate supply from cyanobacterial blooms and take active part in the biomass transformation. We propose that DHVEG-6 and Methanobacterium could be the key archaeal taxa correlated with the “black bloom” formation in Zhushan Bay. PMID:26884723

  11. Vertical Profiles of Abundance and Potential Activity of Methane-Oxidizing Bacteria in Sediment of Lake Biwa, Japan

    PubMed Central

    Tsutsumi, Masazumi; Kojima, Hisaya; Fukui, Manabu

    2012-01-01

    Vertical profiles of the abundance, community composition, and potential activity of methane-oxidizing bacteria (MOB) were investigated in the sediment of Lake Biwa. Sediment samples were obtained from two sites at different water depths. The abundance of MOB was assessed as the copy number of the pmoA gene (encoding the alpha subunit of particulate methane monooxygenase), measured with quantitative real-time PCR. Abundance of the pmoA gene peaked in the 5–8 cm layer of the sediment from both sites. MOB community composition was investigated by denaturing gradient gel electrophoresis (DGGE) analysis of pmoA and 16S rRNA genes. The band patterns observed in DGGE did not significantly differ with sediment depths or sampling sites. Sequence analysis of the DGGE bands indicated the dominance of the genus Methylobacter. Potential activity, which was measured in the presence of sufficient amounts of methane and oxygen, decreased linearly from the sediment surface to deeper layers. These results suggest that the pmoA gene copy number cannot be regarded as an indicator of aerobic MOB that retain potential activity in sediments. PMID:22200642

  12. [FeFe]-hydrogenase abundance and diversity along a vertical redox gradient in Great Salt Lake, USA.

    PubMed

    Boyd, Eric S; Hamilton, Trinity L; Swanson, Kevin D; Howells, Alta E; Baxter, Bonnie K; Meuser, Jonathan E; Posewitz, Matthew C; Peters, John W

    2014-11-28

    The use of [FeFe]-hydrogenase enzymes for the biotechnological production of H2 or other reduced products has been limited by their sensitivity to oxygen (O2). Here, we apply a PCR-directed approach to determine the distribution, abundance, and diversity of hydA gene fragments along co-varying salinity and O2 gradients in a vertical water column of Great Salt Lake (GSL), UT. The distribution of hydA was constrained to water column transects that had high salt and relatively low O2 concentrations. Recovered HydA deduced amino acid sequences were enriched in hydrophilic amino acids relative to HydA from less saline environments. In addition, they harbored interesting variations in the amino acid environment of the complex H-cluster metalloenzyme active site and putative gas transfer channels that may be important for both H2 transfer and O2 susceptibility. A phylogenetic framework was created to infer the accessory cluster composition and quaternary structure of recovered HydA protein sequences based on phylogenetic relationships and the gene contexts of known complete HydA sequences. Numerous recovered HydA are predicted to harbor multiple N- and C-terminal accessory iron-sulfur cluster binding domains and are likely to exist as multisubunit complexes. This study indicates an important role for [FeFe]-hydrogenases in the functioning of the GSL ecosystem and provides new target genes and variants for use in identifying O2 tolerant enzymes for biotechnological applications.

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    Global change, together with human activities had resulted in increasing amounts of organic material (including nutrients) received by water bodies. This input further attenuates the penetration of solar radiation leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, which effects have in general been neglected. Even more, the combined impacts of mixing, together with those of UVR and nutrients input are virtually unknown. In this study, we carried out in situ experiments in three high mountain lakes of Spain (Lake Enol in Asturias, and lakes Las Yeguas and La Caldera in Granada) to determine the combined effects of these three variables associated to global change on photosynthetic responses of natural phytoplankton communities. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR + PAR (280-700 nm) versus PAR alone (400-700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 μg P l-1, and N to reach a N : P molar ratio of 31) and, (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m every 4 min, total of 10 cycles) versus static. Our findings suggest that under in situ nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and EOC from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where antagonistic effects were determined, with mixing partially counteracting the negative effects of UVR. Nutrients input mimicking atmospheric pulses from Saharan dust, reversed this effect and clear lakes became more inhibited during mixing, while opaque lakes benefited from the fluctuating irradiance

  14. The potential of high-frequency profiling to assess vertical and seasonal patterns of phytoplankton dynamics in lakes: An extension of the Plankton Ecology Group (PEG) model

    USGS Publications Warehouse

    Brentrup, Jennifer A.; Williamson, Craig E.; Colom-Montero, William; Eckert, Werner; de Eyto, Elvira; Grossart, Hans-Peter; Huot, Yannick; Isles, Peter D. F.; Knoll, Lesley B.; Leach, Taylor H.; McBride, Christopher G.; Pierson, Don; Pomati, Francesco; Read, Jordan S.; Rose, Kevin C.; Samal, Nihar R.; Staehr, Peter A.; Winslow, Luke A.

    2016-01-01

    The use of high-frequency sensors on profiling buoys to investigate physical, chemical, and biological processes in lakes is increasing rapidly. Profiling buoys with automated winches and sensors that collect high-frequency chlorophyll fluorescence (ChlF) profiles in 11 lakes in the Global Lake Ecological Observatory Network (GLEON) allowed the study of the vertical and temporal distribution of ChlF, including the formation of subsurface chlorophyll maxima (SSCM). The effectiveness of 3 methods for sampling phytoplankton distributions in lakes, including (1) manual profiles, (2) single-depth buoys, and (3) profiling buoys were assessed. High-frequency ChlF surface data and profiles were compared to predictions from the Plankton Ecology Group (PEG) model. The depth-integrated ChlF dynamics measured by the profiling buoy data revealed a greater complexity that neither conventional sampling nor the generalized PEG model captured. Conventional sampling techniques would have missed SSCM in 7 of 11 study lakes. Although surface-only ChlF data underestimated average water column ChlF, at times by nearly 2-fold in 4 of the lakes, overall there was a remarkable similarity between surface and mean water column data. Contrary to the PEG model’s proposed negligible role for physical control of phytoplankton during the growing season, thermal structure and light availability were closely associated with ChlF seasonal depth distribution. Thus, an extension of the PEG model is proposed, with a new conceptual framework that explicitly includes physical metrics to better predict SSCM formation in lakes and highlight when profiling buoys are especially informative.

  15. [FeFe]-Hydrogenase Abundance and Diversity along a Vertical Redox Gradient in Great Salt Lake, USA

    PubMed Central

    Boyd, Eric S.; Hamilton, Trinity L.; Swanson, Kevin D.; Howells, Alta E.; Baxter, Bonnie K.; Meuser, Jonathan E.; Posewitz, Matthew C.; Peters, John W.

    2014-01-01

    The use of [FeFe]-hydrogenase enzymes for the biotechnological production of H2 or other reduced products has been limited by their sensitivity to oxygen (O2). Here, we apply a PCR-directed approach to determine the distribution, abundance, and diversity of hydA gene fragments along co-varying salinity and O2 gradients in a vertical water column of Great Salt Lake (GSL), UT. The distribution of hydA was constrained to water column transects that had high salt and relatively low O2 concentrations. Recovered HydA deduced amino acid sequences were enriched in hydrophilic amino acids relative to HydA from less saline environments. In addition, they harbored interesting variations in the amino acid environment of the complex H-cluster metalloenzyme active site and putative gas transfer channels that may be important for both H2 transfer and O2 susceptibility. A phylogenetic framework was created to infer the accessory cluster composition and quaternary structure of recovered HydA protein sequences based on phylogenetic relationships and the gene contexts of known complete HydA sequences. Numerous recovered HydA are predicted to harbor multiple N- and C-terminal accessory iron-sulfur cluster binding domains and are likely to exist as multisubunit complexes. This study indicates an important role for [FeFe]-hydrogenases in the functioning of the GSL ecosystem and provides new target genes and variants for use in identifying O2 tolerant enzymes for biotechnological applications. PMID:25464382

  16. The Rise and Fall of Plankton: Long-Term Changes in the Vertical Distribution of Algae and Grazers in Lake Baikal, Siberia

    PubMed Central

    Hampton, Stephanie E.; Gray, Derek K.; Izmest'eva, Lyubov R.; Moore, Marianne V.; Ozersky, Tedy

    2014-01-01

    Both surface water temperatures and the intensity of thermal stratification have increased recently in large lakes throughout the world. Such physical changes can be accompanied by shifts in plankton community structure, including changes in relative abundances and depth distributions. Here we analyzed 45 years of data from Lake Baikal, the world's oldest, deepest, and most voluminous lake, to assess long-term trends in the depth distribution of pelagic phytoplankton and zooplankton. Surface water temperatures in Lake Baikal increased steadily between 1955 and 2000, resulting in a stronger thermal gradient within the top 50 m of the water column. In conjunction with these physical changes our analyses reveal significant shifts in the daytime depth distribution of important phytoplankton and zooplankton groups. The relatively heavy diatoms, which often rely on mixing to remain suspended in the photic zone, shifted downward in the water column by 1.90 m y-1, while the depths of other phytoplankton groups did not change significantly. Over the same time span the density-weighted average depth of most major zooplankton groups, including cladocerans, rotifers, and immature copepods, exhibited rapid shifts toward shallower positions (0.57–0.75 m y−1). As a result of these depth changes the vertical overlap between herbivorous copepods (Epischura baikalensis) and their algal food appears to have increased through time while that for cladocerans decreased. We hypothesize that warming surface waters and reduced mixing caused these ecological changes. Future studies should examine how changes in the vertical distribution of plankton might impact energy flow in this lake and others. PMID:24586441

  17. The rise and fall of plankton: long-term changes in the vertical distribution of algae and grazers in Lake Baikal, Siberia.

    PubMed

    Hampton, Stephanie E; Gray, Derek K; Izmest'eva, Lyubov R; Moore, Marianne V; Ozersky, Tedy

    2014-01-01

    Both surface water temperatures and the intensity of thermal stratification have increased recently in large lakes throughout the world. Such physical changes can be accompanied by shifts in plankton community structure, including changes in relative abundances and depth distributions. Here we analyzed 45 years of data from Lake Baikal, the world's oldest, deepest, and most voluminous lake, to assess long-term trends in the depth distribution of pelagic phytoplankton and zooplankton. Surface water temperatures in Lake Baikal increased steadily between 1955 and 2000, resulting in a stronger thermal gradient within the top 50 m of the water column. In conjunction with these physical changes our analyses reveal significant shifts in the daytime depth distribution of important phytoplankton and zooplankton groups. The relatively heavy diatoms, which often rely on mixing to remain suspended in the photic zone, shifted downward in the water column by 1.90 m y(-1), while the depths of other phytoplankton groups did not change significantly. Over the same time span the density-weighted average depth of most major zooplankton groups, including cladocerans, rotifers, and immature copepods, exhibited rapid shifts toward shallower positions (0.57-0.75 m y(-1)). As a result of these depth changes the vertical overlap between herbivorous copepods (Epischura baikalensis) and their algal food appears to have increased through time while that for cladocerans decreased. We hypothesize that warming surface waters and reduced mixing caused these ecological changes. Future studies should examine how changes in the vertical distribution of plankton might impact energy flow in this lake and others.

  18. Vertical distribution of radiation dose rates in the water of a brackish lake in Aomori Prefecture, Japan.

    PubMed

    Ohtsuka, Yoshihito; Iyogi, Takashi; Ueda, Shinji; Hisamatsu, Shun'ichi

    2015-11-01

    Seasonal radiation dose rates were measured with glass dosemeters housed in watertight cases at various depths in the water of Lake Obuchi, a brackish lake in Aomori Prefecture, Japan, during fiscal years 2011-2013 to assess the background external radiation dose to aquatic biota in the lake. The mean radiation dose in the surface water of the lake was found to be 27 nGy h(-1), which is almost the same as the absorption dose rate due to cosmic ray reported in the literature. Radiation dose rates decreased exponentially with water depth down to a depth of 1 m above the bottom sediment. In the water near the sediment, the dose rate increased with depth owing to the emission of γ-rays from natural radionuclides in the sediment.

  19. Simulation of advection and vertical distribution of buoyant cyanobacterial colonies in Lake Erie with a Lagrangian particle model for short-term forecasts of harmful algal blooms

    NASA Astrophysics Data System (ADS)

    Rowe, M. D.; Anderson, E. J.; Wynne, T.; Stumpf, R. P.; Fanslow, D. L.; Vanderploeg, H. A.

    2016-02-01

    Cyanobacterial harmful algal blooms (CHABs), primarily Microcystis, are a recurring problem in western Lake Erie. Short-term forecasts of CHABs are important to water treatment plant operators, anglers, recreational boaters, and beach users. NOAA NCCOS and NOAA GLERL have developed experimental forecast products that indicate the present location and extent of CHABs from satellite imagery, then predict the movement of the CHAB five days into the future using forecast meteorology. These products use Lagrangian particle tracking models to forecast CHAB transport, forced by currents from a hydrodynamic model. Western Lake Erie is a shallow (< 11 m) freshwater system. CHABs occur during the months of July to October, a time when the water column is intermittently stratified or mixed to the bottom in response to wind and surface heating or cooling. Microcystis colonies may be mixed through the water column or concentrated in surface scums, depending on the balance between buoyancy and turbulent mixing. Present forecast models do not simulate the vertical distribution of buoyant cyanobacterial colonies, which detracts from model skill when mixing events cause large changes in surface concentration. We evaluated model skill in a 2011 hindcast using a Lagrangian particle model that included vertical mixing and buoyancy by comparison to satellite imagery and in-situ observations. Turbulent diffusivity and 3D currents were provided by the Finite Volume Coastal Ocean Model (FVCOM). Random-walk vertical mixing schemes may produce artifacts in simulated concentration profiles in the presence of diffusivity gradients. We evaluated several random-walk numerical schemes and time step criteria to determine conditions under which artifact formation could be avoided. Inclusion of vertical mixing with buoyancy enabled the model to simulate observed changes in surface chlorophyll concentration in response to variable mixing conditions, which improved model skill statistics.

  20. Distribution of lacustrine Crenarchaeota in Lake Superior: implications for the application of the TEX86 temperature proxy

    NASA Astrophysics Data System (ADS)

    Woltering, M. L.; Werne, J. P.; Hicks, R.; Kish, J.; Oster, R.; Schouten, S.; Sinninghe Damsté, J. S.

    2009-12-01

    The TEX86 is a proxy that can be applied on continental lake sediments to reconstruct past water temperatures. It is based on the lipids derived from aquatic Crenarchaeota, and although first applied in marine systems has already been successfully used in sediments from some of the continental lake drilling projects in Lake Malawi and Tanganyika. Recent studies have shown that the application of this proxy in lacustrine systems appears to be limited to mainly large to intermediate size lakes that are only marginally terrestrially influenced. Here TEX86 values from surface sediments appear to correlate strongly with both annual mean as mean winter surface water temperatures. Besides this observed empirical relationship between TEX86 values and lake surface temperatures, very little is known about the distribution and ecology of the organisms that produce the lipids that make up the TEX86 in lacustrine systems. Here we will present the results of our multiyear water column and sediment trap study in Lake Superior where we investigated where vertically and at what time of year the lipids are produced that make up the TEX86 proxy, which end up in the sediment record. We have combined both biogeochemical and molecular techniques to both water filter samples as sediment trap material, combined thermistor observations in the water column to create vertical profiles of Crenarchaeotal and lipid abundance to investigate the spatial distribution of the lacustrine Crenarchaeota in order to determine if or what kind of temperature is actually represented by the TEX86 proxy in Lake Superior. Our results show that the TEX86 measured in particulate organic matter does a good job reconstructing the actual thermal structure of the water column. However, the lipids that make up the TEX86 in Lake Superior are produced throughout the lake during isothermal conditions, but mainly below the thermocline when the lake is stratified suggesting that in Lake Superior the TEX86 largely

  1. Assembly processes of gastropod community change with horizontal and vertical zonation in ancient Lake Ohrid: a metacommunity speciation perspective

    NASA Astrophysics Data System (ADS)

    Hauffe, Torsten; Albrecht, Christian; Wilke, Thomas

    2016-05-01

    The Balkan Lake Ohrid is the oldest and most diverse freshwater lacustrine system in Europe. However, it remains unclear whether species community composition, as well as the diversification of its endemic taxa, is mainly driven by dispersal limitation, environmental filtering, or species interaction. This calls for a holistic perspective involving both evolutionary processes and ecological dynamics, as provided by the unifying framework of the "metacommunity speciation model".The current study used the species-rich model taxon Gastropoda to assess how extant communities in Lake Ohrid are structured by performing process-based metacommunity analyses. Specifically, the study aimed (1) to identifying the relative importance of the three community assembly processes and (2) to test whether the importance of these individual processes changes gradually with lake depth or discontinuously with eco-zone shifts.Based on automated eco-zone detection and process-specific simulation steps, we demonstrated that dispersal limitation had the strongest influence on gastropod community composition. However, it was not the exclusive assembly process, but acted together with the other two processes - environmental filtering and species interaction. The relative importance of the community assembly processes varied both with lake depth and eco-zones, though the processes were better predicted by the latter.This suggests that environmental characteristics have a pronounced effect on shaping gastropod communities via assembly processes. Moreover, the study corroborated the high importance of dispersal limitation for both maintaining species richness in Lake Ohrid (through its impact on community composition) and generating endemic biodiversity (via its influence on diversification processes). However, according to the metacommunity speciation model, the inferred importance of environmental filtering and biotic interaction also suggests a small but significant influence of ecological

  2. Analysis of the La:P ratio in lake sediments - Vertical and spatial distribution assessed by a multiple-core survey.

    PubMed

    Yasseri, Said; Epe, Tim S

    2016-06-15

    In recent years, lanthanum modified bentonite has been increasingly applied to eutrophic lakes with the aim of converting potentially bio-available forms of phosphorus in sediments into biologically unavailable forms. In many of these applications, however, no attempts have been made to assess the efficiency and efficacy of the measure in terms of its effect on the sediment. In this study, we collected sediment cores from a heavily eutrophied lake that has previously been treated with lanthanum modified clay. This restoration method is based on the strong ionic bond formed between lanthanum and phosphate which results in the formation of LaPO4 (Rhabdophane) in the sediment. In order to determine the changes that had occurred in the sediments as a result of the addition of the clay, we measured the vertical distribution of lanthanum in the collected cores, calculated La:P ratios of the different sediment layers and used the ratios to determine whether or not the applied dosage was sufficient. By means of the geostatistical method of kriging these values were transferred into maps of different depth intervals to visualize the results. The results indicate that the La:P ratio may be a useful tool which allows lake managers to measure the vertical distribution of lanthanum in sediments following treatments and determine whether or not dosages are sufficient to permanently render sediment phosphorus biologically unavailable. The method may also provide a basis on which to decide whether or not smaller reapplications are needed and can be used to control the dispersion of the material.

  3. Vertical distributions of radionuclides ((239+240)Pu, (240)Pu/(239)Pu, and (137)Cs) in sediment cores of Lake Bosten in Northwestern China.

    PubMed

    Liao, Haiqing; Bu, Wenting; Zheng, Jian; Wu, Fengchang; Yamada, Masatoshi

    2014-04-01

    Artificial radionuclides ((137)Cs, (239+240)Pu, (241)Pu, (241)Am) deposited in lacustrine sediments have been used for dating as well as radionuclide source identification. In the present work, we investigated the vertical distributions of (239+240)Pu and (137)Cs activities, (240)Pu/(239)Pu atom ratios, and (239+240)Pu/(137)Cs activity ratios in sediment cores collected from Lake Bosten, which is the lake closest to the Lop Nor Chinese Nuclear Weapon Test site in northwestern China. Uniformly high concentrations of (239+240)Pu and (137)Cs were found in the upper layers deposited since 1964 in the sediment cores, and these were controlled by the resuspension of soil containing radionuclides from the nearby land surface. As the Chinese nuclear tests varied remarkably in yield, the mixing of the tropospheric deposition from these tests and the stratospheric deposition of global fallout has led to a (240)Pu/(239)Pu atom ratio that is similar to that of global fallout and to a (239+240)Pu/(137)Cs activity ratio that is slightly higher than that of global fallout. However, a low (240)Pu/(239)Pu atom ratio of 0.080 and high (239+240)Pu/(137)Cs activity ratio of 0.087, significantly different from the global fallout values, were observed in one sediment core (07BS10-2), indicating the inhomogenous tropospheric deposition from the Chinese nuclear tests in Lake Bosten during 1967-1973. These results are important to understand the influence of the CNTs on the radionuclide contamination in Lake Bosten.

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

    NASA Astrophysics Data System (ADS)

    Van Damme, D.; Gautier, A.

    2013-09-01

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

  5. Time-dependent models of vertical deformation for the Yellowstone-Hebgen Lake Region, 1923-1987

    NASA Astrophysics Data System (ADS)

    Holdahl, Sandford R.; Dzurisin, Daniel

    1991-02-01

    Results of repeated levelings have been used to determine the patterns of elevation change associated with the Yellowstone caldera, and apparent viscoelastic rebound following the magnitude 7.3 earthquake near Hebgen Lake in 1959. Models with alternative treatments for nonuniform height change were utilized. Area-wide levelings in 1923, 1975-1977, and 1987 in Yellowstone National Park allowed derivation of uplift velocities for the periods before and after 1976. Maximum uplift velocity for the earlier period was 14 mm/yr, causing 90 cm of height change from 1923 to 1984. Recent annual levelings on the east side of the caldera show a cessation of uplift in 1984-85, and the beginning of rapid subsidence; -19 mm/yr from 1985 to 1989. The long-term uplift correlates closely with the caldera rim. After structuring the leveling observations to be insensitive to the 1959 coseismic deformation (-6 m) at Hebgen Lake, the broader spatial pattern of postseismic rebound was resolved, showing uplift of at least 32 cm. As a group, the relevelings converging at nearby West Yellowstone were accomplished at various times, which allowed selection of a best model to fit the temporal character of postseismic motion. The preferred model has a 2-year decay period indicating that uplift stopped by 1970. Supplementary indications of the uplift near Hebgen Lake were obtained by comparing Global Positioning System data to earlier levelings, facilitated by a new precise geoid by D. G. Milbert and W. T. Dewhurst (submitted manuscript, 1990).

  6. Analysis of the effects of vertical grid resolution on the performance of the UAM-IV vs. UAM-V in the Lake Michigan region

    SciTech Connect

    Fernau, M.E.; Moore, G.E.

    1996-12-31

    As part of the Cooperative Regional Model Evaluation (CReME) study, it was found that there was little difference in the abilities of the UAM-IV and UAM-V photochemical models to simulate the observed ozone concentrations during two 1991 ozone episodes in the Lake Michigan region. However, it was noted that UAM-V underpredicts the ozone precursors such as volatile organic compounds and nitrogen oxides (VOC and NO{sub x}) by less than does UAM-IV when compared to the extensive three-dimensional observations made during the Lake Michigan Ozone Study. UAM-IV was implemented using five vertical layers that can vary in thickness with space and time, depending on the local mixing depth. UAM-V was run using eight fixed layers with high resolution near the ground. It was hypothesized that UAM-IV`s relative inability to capture detailed spatial variability in the precursor fields could be due in large part to the diminished resolution of the model compared to UAM-V. In this paper, results from a ten-layer version of UAM-IV are compared to both UAM-V and the five-layer version of UAM-IV, using detailed ozone and ozone precursor measurements from both the surface and aircraft.

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

    PubMed

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

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Locke, William W.; Meyer, Grant A.

    1994-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Locke, William W.; Meyer, Grant A.

    1994-01-01

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

  10. Lateral and vertical channel movement and potential for bed-material movement on the Madison River downstream from Earthquake Lake, Montana

    USGS Publications Warehouse

    Chase, Katherine J.; McCarthy, Peter M.

    2012-01-01

    and to investigate the potential for bed material movement along the same reach. The purpose of this report is to present information about the lateral and vertical movement of the Madison River from 1970 to 2006 for a 1-mile reach downstream from Earthquake Lake and for Raynolds Pass Bridge, and to provide an analysis of the potential for bed-material movement so that MADTAC can evaluate the applicability of the previously determined threshold streamflow for initiation of damaging erosion. As part of this study channel cross sections originally surveyed by the USGS in 1971 were resurveyed in 2006. Incremental channel-movement distances were determined by comparing the stream centerlines from 14 aerial photographs taken between 1970 and 2006. Depths of channel incision and aggregation were determined by comparing the 2006 and 1971 cross-section and water-surface data. Particle sizes of bed and bank materials were measured in 2006 and 2008 using the pebble-count method and sieve analyses. A one-dimensional hydraulic-flow model (HEC-RAS) was used to calculate mean boundary-shear stresses for various streamflows; these calculated boundary-shear stresses were compared to calculated critical-shear stresses for the bed materials to determine the potential for bed-material movement. A comparison of lateral channel movement distances with annual peak streamflows shows that streamflows higher than the 3,500-ft3/s threshold were followed by lateral channel movement except from 1991 to 1992 and possibly from 1996 to 1997. However, it was not possible to discern whether the channel moved gradually or suddenly, or in response to one peak flow, to several peak flows, or to sustained flows. The channel moved between 2002 and 2005 even when streamflows were less than the threshold streamflow of 3,500 ft3/s. Comparisons of cross sections and aerial photographs show that the channel has moved laterally and incised and aggraded to varying degrees. The channel has developed meander bends

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

    SciTech Connect

    Tiercelin, J.J.; Mondeguer, A. ); Thouin, C. ); Kalala, T. )

    1989-11-01

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

  12. Metamorphic and structural evidence for significant vertical displacement along the Ross Lake fault zone, a major orogen-parallel shear zone in the Cordillera of western North America

    USGS Publications Warehouse

    Baldwin, J.A.; Whitney, D.L.; Hurlow, H.A.

    1997-01-01

    Results of an investigation of the petrology and structure of the Skymo complex and adjacent terranes constrain the amount, timing, and sense of motion on a segment of the > 600-km-long Late Cretaceous - early Tertiary Ross Lake fault zone (RLFZ), a major orogen-parallel shear zone in the Cordillera of western North America. In the study area in the North Cascades, Washington state, the RLFZ accommodated significant pre-middle Eocene vertical displacement, and it juxtaposes the Skymo complex with upper amphibolite facies (650??-690??C and 6-7 kbar) Skagit Gneiss of the North Cascades crystalline core to the SW and andalusite-bearing phyllite of the Little Jack terrane (Intermontane superterrane) to the NE. The two main lithologic units of the Skymo complex, a primitive mafic intrusion and a fault-bounded block of granulite facies metasedimentary rocks, are unique in the North Cascades. Granulite facies conditions were attained during high-temperature (> 800??C), low pressure (??? 4 kbar) contact metamorphism associated with intrusion of the mafic magma. P-T estimates and reaction textures in garnet-orthopyroxene gneiss suggest that contact metamorphism followed earlier, higher pressure regional metamorphism. There is no evidence that the Skagit Gneiss experienced high-T - low-P contact metamorphism. In the Little Jack terrane, however, texturally late cordierite ?? spinel and partial replacement of andalusite by sillimanite near the terrane's fault contact with Skymo gabbro suggest that the Little Jack terrane experienced high-T (??? 600??C) - low-P (??? 4 kbar) contact metamorphism following earlier low-grade regional metamorphism. Similarities in the protoliths of metasedimentary rocks in the Skymo and Little Jack indicate that they may be part of the same terrane. Differences in pressure estimates for the Little Jack versus Skymo for regional metamorphism that preceded contact metamorphism indicate vertical displacement of ??? 10 km (west side up) on the strand

  13. Vertical distribution of ammonia-oxidizing crenarchaeota and methanogens in the epipelagic waters of Lake Kivu (Rwanda-Democratic Republic of the Congo).

    PubMed

    Llirós, Marc; Gich, Frederic; Plasencia, Anna; Auguet, Jean-Christophe; Darchambeau, François; Casamayor, Emilio O; Descy, Jean-Pierre; Borrego, Carles

    2010-10-01

    Four stratified basins in Lake Kivu (Rwanda-Democratic Republic of the Congo) were sampled in March 2007 to investigate the abundance, distribution, and potential biogeochemical role of planktonic archaea. We used fluorescence in situ hybridization with catalyzed-reported deposition microscopic counts (CARD-FISH), denaturing gradient gel electrophoresis (DGGE) fingerprinting, and quantitative PCR (qPCR) of signature genes for ammonia-oxidizing archaea (16S rRNA for marine Crenarchaeota group 1.1a [MCG1] and ammonia monooxygenase subunit A [amoA]). Abundance of archaea ranged from 1 to 4.5% of total DAPI (4',6-diamidino-2-phenylindole) counts with maximal concentrations at the oxic-anoxic transition zone (∼50-m depth). Phylogenetic analysis of the archaeal planktonic community revealed a higher level of richness of crenarchaeal 16S rRNA gene sequences (21 of the 28 operational taxonomic units [OTUs] identified [75%]) over euryarchaeotal ones (7 OTUs). Sequences affiliated with the kingdom Euryarchaeota were mainly recovered from the anoxic water compartment and mostly grouped into methanogenic lineages (Methanosarcinales and Methanocellales). In turn, crenarchaeal phylotypes were recovered throughout the sampled epipelagic waters (0- to 100-m depth), with clear phylogenetic segregation along the transition from oxic to anoxic water masses. Thus, whereas in the anoxic hypolimnion crenarchaeotal OTUs were mainly assigned to the miscellaneous crenarchaeotic group, the OTUs from the oxic-anoxic transition and above belonged to Crenarchaeota groups 1.1a and 1.1b, two lineages containing most of the ammonia-oxidizing representatives known so far. The concomitant vertical distribution of both nitrite and nitrate maxima and the copy numbers of both MCG1 16S rRNA and amoA genes suggest the potential implication of Crenarchaeota in nitrification processes occurring in the epilimnetic waters of the lake.

  14. Vertical Distribution of Ammonia-Oxidizing Crenarchaeota and Methanogens in the Epipelagic Waters of Lake Kivu (Rwanda-Democratic Republic of the Congo)▿ †

    PubMed Central

    Llirós, Marc; Gich, Frederic; Plasencia, Anna; Auguet, Jean-Christophe; Darchambeau, François; Casamayor, Emilio O.; Descy, Jean-Pierre; Borrego, Carles

    2010-01-01

    Four stratified basins in Lake Kivu (Rwanda-Democratic Republic of the Congo) were sampled in March 2007 to investigate the abundance, distribution, and potential biogeochemical role of planktonic archaea. We used fluorescence in situ hybridization with catalyzed-reported deposition microscopic counts (CARD-FISH), denaturing gradient gel electrophoresis (DGGE) fingerprinting, and quantitative PCR (qPCR) of signature genes for ammonia-oxidizing archaea (16S rRNA for marine Crenarchaeota group 1.1a [MCG1] and ammonia monooxygenase subunit A [amoA]). Abundance of archaea ranged from 1 to 4.5% of total DAPI (4′,6-diamidino-2-phenylindole) counts with maximal concentrations at the oxic-anoxic transition zone (∼50-m depth). Phylogenetic analysis of the archaeal planktonic community revealed a higher level of richness of crenarchaeal 16S rRNA gene sequences (21 of the 28 operational taxonomic units [OTUs] identified [75%]) over euryarchaeotal ones (7 OTUs). Sequences affiliated with the kingdom Euryarchaeota were mainly recovered from the anoxic water compartment and mostly grouped into methanogenic lineages (Methanosarcinales and Methanocellales). In turn, crenarchaeal phylotypes were recovered throughout the sampled epipelagic waters (0- to 100-m depth), with clear phylogenetic segregation along the transition from oxic to anoxic water masses. Thus, whereas in the anoxic hypolimnion crenarchaeotal OTUs were mainly assigned to the miscellaneous crenarchaeotic group, the OTUs from the oxic-anoxic transition and above belonged to Crenarchaeota groups 1.1a and 1.1b, two lineages containing most of the ammonia-oxidizing representatives known so far. The concomitant vertical distribution of both nitrite and nitrate maxima and the copy numbers of both MCG1 16S rRNA and amoA genes suggest the potential implication of Crenarchaeota in nitrification processes occurring in the epilimnetic waters of the lake. PMID:20802065

  15. Mid-term variation of vertical distribution of acid volatile sulphide and simultaneously extracted metals in sediment cores from Lake Albufera (Valencia, Spain).

    PubMed

    Hernández-Crespo, Carmen; Martín, Miguel

    2013-11-01

    Lake Albufera is one of the most eutrophic bodies of water in Spain due to point and diffuse pollution over past decades, and its sediments are likely to be anoxic because of high organic matter flux. Hence, sulphides can play an important role in limiting the mobility of heavy metals. This study aimed to study the vertical variation of acid volatile sulphide (AVS) and simultaneously extracted metals (SEM) in sediment cores collected from Lake Albufera; other sediment characteristics, such as organic matter, biochemical oxygen, demand or total metals, were also studied. Three sites were selected, and four sampling campaigns were performed to study spatial and temporal variation as well as to obtain information regarding historical variation in the composition of sediments. AVS and SEM were analysed by the purge-and-trap method. The vertical distribution of AVS and SEM varied depending on the sampling site-concentrations of AVS and SEM were higher at sites close to mouths of inflowing channels. A decreasing trend of AVS has been found at these sites over time: In the two first samplings, AVS increased with depth reaching maximum concentrations of 40 and 21 μmol g(-1), but from then on AVS were lower and decreased with depth. SEM decreased with depth from 3 μmol g(-1) in surface layers to approximately 1 μmol g(-1) at deeper segments at these sites. However, the central site was more uniform with respect to depth as well as with time; it presented lower values of SEM and AVS (mean 0.9 and 2.0 μmol g(-1) respectively), and the maximum value of AVS (7 μmol g(-1)) was found at the top layer (0-3 cm). According to the (SEM-AVS)/fOC approach, every site, and throughout the cores, can be classified as containing nontoxic metals because the values were <130 μmol g(-1).

  16. Lateralized kinematics of predation behavior in a Lake Tanganyika scale-eating cichlid fish.

    PubMed

    Takeuchi, Yuichi; Hori, Michio; Oda, Yoichi

    2012-01-01

    Behavioral lateralization has been documented in many vertebrates. The scale-eating cichlid fish Perissodus microlepis is well known for exhibiting lateral dimorphism in its mouth morphology and lateralized behavior in robbing scales from prey fish. A previous field study indicated that this mouth asymmetry closely correlates with the side on which prey is attacked, but details of this species' predation behavior have not been previously analyzed because of the rapidity of the movements. Here, we studied scale-eating behavior in cichlids in a tank through high-speed video monitoring and quantitative assessment of behavioral laterality and kinematics. The fish observed showed a clear bias toward striking on one side, which closely correlated with their asymmetric mouth morphologies. Furthermore, the maximum angular velocity and amplitude of body flexion were significantly larger during attacks on the preferred side compared to those on the nonpreferred side, permitting increased predation success. In contrast, no such lateral difference in movement elements was observed in acoustically evoked flexion during the escape response, which is similar to flexion during scale eating and suggests that they share a common motor control pathway. Thus the neuronal circuits controlling body flexion during scale eating may be functionally lateralized upstream of this common motor pathway.

  17. When a rash has two names: pese sorcery and kisigo spirits at Lake Tanganyika.

    PubMed

    Bleyenberg, Eva; Stroeken, Koen

    2017-09-06

    This explorative and qualitative study, based on 27 interviews during two months of fieldwork, describes pese, an affliction of the skin that has conspicuously stayed under the radar of medico-anthropological research in Kigoma, a rural city in the northwest Tanzania. The condition reminds of a locally better known condition labeled kisigo, raising the question why two concepts of the same affliction exist side by side. It seems indicative that the two illness concepts stem from different cultures and that each specializes in an explanatory model: the former witchcraft (sorcery) and the latter spirit possession. Moreover, a symbiotic relation seems to exist between the healing traditions of the Bembe and the Ha. Government policies prohibiting witchcraft and targeting traditional healers seem to have created a situation where witchcraft practices and beliefs have come to represent the periphery and survive there, clandestinely.

  18. Lateralized Kinematics of Predation Behavior in a Lake Tanganyika Scale-Eating Cichlid Fish

    PubMed Central

    Takeuchi, Yuichi; Hori, Michio; Oda, Yoichi

    2012-01-01

    Behavioral lateralization has been documented in many vertebrates. The scale-eating cichlid fish Perissodus microlepis is well known for exhibiting lateral dimorphism in its mouth morphology and lateralized behavior in robbing scales from prey fish. A previous field study indicated that this mouth asymmetry closely correlates with the side on which prey is attacked, but details of this species' predation behavior have not been previously analyzed because of the rapidity of the movements. Here, we studied scale-eating behavior in cichlids in a tank through high-speed video monitoring and quantitative assessment of behavioral laterality and kinematics. The fish observed showed a clear bias toward striking on one side, which closely correlated with their asymmetric mouth morphologies. Furthermore, the maximum angular velocity and amplitude of body flexion were significantly larger during attacks on the preferred side compared to those on the nonpreferred side, permitting increased predation success. In contrast, no such lateral difference in movement elements was observed in acoustically evoked flexion during the escape response, which is similar to flexion during scale eating and suggests that they share a common motor control pathway. Thus the neuronal circuits controlling body flexion during scale eating may be functionally lateralized upstream of this common motor pathway. PMID:22238598

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

    USGS Publications Warehouse

    Wood, Tamara M.; Gartner, Jeffrey W.

    2010-01-01

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

  20. An in lake comparison of the branched GDGT lacustrine paleothermometer with other temperature proxies

    NASA Astrophysics Data System (ADS)

    Loomis, S. E.; Russell, J. M.; Sinninghe Damste, J. S.

    2011-12-01

    Quantitative paleoclimate reconstructions are essential for testing the efficacy of climate models, yet there are very few proxies that can reconstruct temperature over much of the terrestrial landscape. A novel group of bacterial membrane lipids known as branched glycerol dialkyl glycerol tetraethers (GDGTs) have strong potential to be used as a paleotemperature proxy given their ubiquity in peats, soils, lacustrine sediments, and near shore ocean sediments. There are nine known branched GDGTs, and the degree of methylation and cyclisation of these compounds has been shown to relate to the mean annual air temperature (MAAT) of their environment. Several different calibrations have been put forth relating branched GDGT distribution to MAAT, but up to now, there has been limited success applying these calibrations lake cores to reconstruct paleotemperatures. We have now developed a branched GDGT temperature calibration based upon 109 lake surface sediments in tropical Africa. Here we test the applicability of branched GDGT lacustrine paleothermometer on three different tropical lakes, including Lake Tanganyika, Lake Malawi, and Lake Peten Itza. These lakes were chosen because they have paleotemperature reconstructions derived from proxies independent of branched GDGTs, including TEX86, fossil pollen (Tanganyika and Malawi) and biogenic carbonate isotopes (Peten Itza) to reconstruct past lake water temperatures, allowing us to directly compare our reconstructions to those derived from other proxies. We apply both published and unpublished calibrations to our lake core data in an attempt to deduce the most accurate calibrations to reconstruct temperatures from lacustrine sediments.

  1. Quantifying Wintertime Aerosol Nitrate Formation Pathways and Their Vertical Profiles in the Great Lakes Region of North America by CMAQ Process Analysis and Hourly Observations

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Spak, S.; Carmichael, G. R.; Riemer, N. S.; Baek, J.; Fontaine, A.; Janssen, M.; Kenski, D. M.

    2012-12-01

    In order to better understand wintertime episodes of elevated fine particle (PM2.5) in the Great Lakes region, a modeling analysis using the CMAQ air quality model was conducted for January-March 2009, a period where special surface based observations were conducted at a pair of urban and rural sites in Wisconsin. The episodes are found to be regional and are characterized by low wind speeds, near-freezing temperatures, and elevated levels of ammonium nitrate. Integrated process rate (IPR) analysis and integrated reaction rate analysis (IRR) in 12 km regional simulations with the Community Multiscale Air Quality model (CMAQ) are employed to quantify contributions to nitrate formation from all simulated processes, most importantly local chemical production and transport. Substantial vertical profiles are found for nitric acid, nitrate, and N2O5. The maximum concentrations of aerosol nitrate occur at the surface and decrease with altitude. Nitric acid is produced most efficiently 50-200m above the surface at night. Surface concentrations of aerosol nitrate are maintained by downward transport via vertical diffusion. Aerosol nitrate is predominantly removed by dry deposition. The aerosol production rate is significantly higher during episodes, and both daytime and nighttime (N2O5) chemical pathways are important contributors to elevated concentrations. Near the surface at Milwaukee, the daytime formation pathway for nitric acid is larger than the nighttime pathways, while in rural areas, the relative magnitudes are reversed. Across the region, the importance of the nighttime pathway increases with altitude. A spatial analysis highlights regional variability at the surface layer and ~90m above surface for the period February 4 thru February 10, which includes two PM2.5 episodes. The net aerosol chemistry process rates and concentrations show the evolution of regional PM build-up of aerosol nitrate and nitric acid.

  2. Global Lakes Sentinel Services: Evaluation of Chl-a Trends in Deep Clear Lakes

    NASA Astrophysics Data System (ADS)

    Cazzaniga, Ilaria; Giardino, Claudia; Bresciani, Mariano; Poser, Kathrin; Peters, Steef; Hommersom, Annelies; Schenk, Karin; Heege, Thomas; Philipson, Petra; Ruescas, Ana; Bottcher, Martin; Stelzer, Kerstin

    2016-08-01

    The aim of this study is the analysis of trend in the trophic level evolution in clear deep lakes which, being characterised by good quality state, are important socio- economic resources for their regions. The selected lakes are situated in Europe (Garda, Maggiore, Constance and Vättern), North America (Michigan) and Africa (Malawi and Tanganyika) and cover a range of eco- regions (continental, perialpine, boreal, rift valley) distributed globally.To evaluate trophic level tendency we mainly focused on chlorophyll-a concentrations (chl-a) which is a direct proxy of trophic status. The chl-a concentrations were obtained from 5216 cloud-free MERIS imagery from 2002 to 2012.The 'GLaSS RoIStats tool' available within the GLaSS project was used to extract chl-a in a number of region of interests (ROI) located in pelagic waters as well as some few other stations depending on lakes morphology. For producing the time-series trend, these extracted data were analysed with the Seasonal Kendall test.The results overall show almost stable conditions with a slight increase in concentration for lakes Maggiore, Constance, and the Green Bay of Lake Michigan; a slight decrease for lakes Garda and Tanganyika and absolutely stable conditions for lakes Vättern and Malawi.The results presented in this work show the great capability of MERIS to perform trend tests analysis on trophic status with focus on chl-a concentration. Being chl-a also a key parameter in water quality monitoring plans, this study also supports the managing practices implemented worldwide for using the water of the lakes.

  3. Levels and patterns of persistent organic pollutants (POPs) in tilapia (Oreochromis sp.) from four different lakes in Tanzania: geographical differences and implications for human health.

    PubMed

    Polder, A; Müller, M B; Lyche, J L; Mdegela, R H; Nonga, H E; Mabiki, F P; Mbise, T J; Skaare, J U; Sandvik, M; Skjerve, E; Lie, E

    2014-08-01

    In Tanzania fish is one of the most important protein sources for the rapidly increasing population. Wild fish is threatened by overfishing and pollution from agriculture, industries, mining, household effluents and vector control. To monitor possible implications for public health, the geographical differences of the occurrence and levels of persistent organic pollutants (POPs) in tilapia fish (Oreochromis sp.) from four different Tanzanian lakes were investigated in 2011. Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyls (PBDEs) and hexabromocyclododecane (HBCDD) were determined in pooled samples of tilapia muscle from Lake (L) Victoria, L. Tanganyika, L. Nyasa (also called L. Malawi) and L. Babati in Tanzania in 2011. Levels of Σ-DDTs (274 ng/g lipid weight (lw)) and sum of 7 indicator PCBs (Σ-7PCBs) (17 ng/g lw) were significantly higher in tilapia from L. Tanganyika compared to the other lakes. The highest levels of Σ-endosulfan (94 ng/g lw) were detected in tilapia from L. Victoria. Toxaphenes were detected in low levels in fish from L. Tanganyika and L. Babati. Results revealed a geographic difference in the use of DDT and endosulfan between L. Victoria and L. Tanganyika. Low ratios of DDE/DDT in tilapia from L. Tanganyika indicated an on-going use of DDT in the area. Median levels of ΣBDEs, including BDE-209, were highest in L. Victoria (19.4 ng/g lw) and BDE-209 was present in 68% of the samples from this lake. The presence of BDE-209 indicates increasing influence of imported products from heavy industrialized countries. The measured POP levels in the studied tilapia were all below MRLs of EU or were lower than recommended levels, and thus the fish is considered as safe for human consumption. They may, however, pose a risk to the fish species and threaten biodiversity. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Effect of vertical heterogeneities in a petrophysical evaluation of low resistivity pay zones, B sands, upper Eocene, Block III, Lake Maracaibo

    SciTech Connect

    Coll, C.; Cortiula, B.; Gonzalez, G.; Meza, E.; Rondon, L.

    1996-08-01

    Thin-bed reservoirs can exist as intercalations of thin porous beds and shales. For a proper petrophysical evaluation and geological characterization of this type of reservoir it is necessary to implement an integrated analysis, which includes knowledge of the depositional environment to avoid missing oil zones by applying standard petrophysical evaluations. The normal resistivity logs used on this area do not have enough vertical resolution for detecting thin low resistivity pay zones. Consequently, the common water saturation models indicate high water saturation when they are evaluated. The Middle Eocene Upper B sands are part of the Misoa Formation in Block III of Lake Maracaibo. They have been exploited since 1965 when the first production test was made. The cumulative oil production to date stands at 11.49 MMSTB. In order to supplement the existing geological information in this area, a continuous core was taken which showed the high degree of shales and thin sands intercalations in the pay zone. A careful core-log calibration was made and a new set of petrophysical parameters were established for this reservoir based on the core measurements. This allowed the establishment of a new petrophysical evaluation procedure that helps the calculation of permeability, hydrocarbon volume in place and productivity of this reservoir.

  5. Vertical distribution of trace-element concentrations and occurrence of metallurgical slag particles in accumulated bed sediments of Lake Roosevelt, Washington, September 2002

    USGS Publications Warehouse

    Cox, S.E.; Bell, P.R.; Lowther, J.S.; Van Metre, P.C.

    2005-01-01

    Sediment cores were collected from six locations in Lake Roosevelt to determine the vertical distributions of trace-element concentrations in the accumulated sediments of Lake Roosevelt. Elevated concentrations of arsenic, cadmium, copper, lead, mercury, and zinc occurred throughout much of the accumulated sediments. Concentrations varied greatly within the sediment core profiles, often covering a range of 5 to 10 fold. Trace-element concentrations typically were largest below the surficial sediments in the lower one-half of each profile, with generally decreasing concentrations from the 1964 horizon to the surface of the core. The trace-element profiles reflect changes in historical discharges of trace elements to the Columbia River by an upstream smelter. All samples analyzed exceeded clean-up guidelines adopted by the Confederated Tribes of the Colville Reservation for cadmium, lead, and zinc and more than 70 percent of the samples exceeded cleanup guidelines for mercury, arsenic, and copper. Although 100 percent of the samples exceeded sediment guidelines for cadmium, lead, and zinc, surficial concentrations of arsenic, copper, and mercury in some cores were less than the sediment-quality guidelines. With the exception of copper, the trace-element profiles of the five cores collected along the pre-reservoir Columbia River channel typically showed trends of decreasing concentrations in sediments deposited after the 1964 time horizon. The decreasing concentrations of trace elements in the upper half of cores from along the pre-reservoir Columbia River showed a pattern of decreasing concentrations similar to reductions in trace-element loading in liquid effluent from an upstream smelter. Except for arsenic, trace-element concentrations typically were smaller at downstream reservoir locations along the pre-reservoir Columbia River. Trace-element concentration in sediments from the Spokane Arm of the reservoir showed distinct differences compared to the similarities

  6. High prevalence of non-synonymous substitutions in mtDNA of cichlid fishes from Lake Victoria.

    PubMed

    Shirai, Kazumasa; Inomata, Nobuyuki; Mizoiri, Shinji; Aibara, Mitsuto; Terai, Yohey; Okada, Norihiro; Tachida, Hidenori

    2014-12-01

    When a population size is reduced, genetic drift may fix slightly deleterious mutations, and an increase in nonsynonymous substitution is expected. It has been suggested that past aridity has seriously affected and decreased the populations of cichlid fishes in Lake Victoria, while geographical studies have shown that the water levels in Lake Tanganyika and Lake Malawi have remained fairly constant. The comparably stable environments in the latter two lakes might have kept the populations of cichlid fishes large enough to remove slightly deleterious mutations. The difference in the stability of cichlid fish population sizes between Lake Victoria and the Lakes Tanganyika and Malawi is expected to have caused differences in the nonsynonymous/synonymous ratio, ω (=dN/dS), of the evolutionary rate. Here, we estimated ω and compared it between the cichlids of the three lakes for 13 mitochondrial protein-coding genes using maximum likelihood methods. We found that the lineages of the cichlids in Lake Victoria had a significantly higher ω for several mitochondrial loci. Moreover, positive selection was indicated for several codons in the mtDNA of the Lake Victoria cichlid lineage. Our results indicate that both adaptive and slightly deleterious molecular evolution has taken place in the Lake Victoria cichlids' mtDNA genes, whose nonsynonymous sites are generally conserved. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Stable isotope composition of Earth's large lakes

    NASA Astrophysics Data System (ADS)

    Jasechko, S.; Gibson, J. J.; YI, Y.; Birks, S. J.; Sharp, Z. D.

    2011-12-01

    Lakes cover about three percent of Earth's continental area. Large lakes can significantly influence lake shore and regional climates by increasing specific humidity during evaporation and by moderating air temperatures. Stable isotopes of oxygen and hydrogen can be used to quantify lake evaporation, providing a supplementary and often cost-advantageous alternative to conventional hydrologic approaches that require over lake monitoring. Further, stable isotopes in lake sediments are an established tool in paleolimnology; however, interpreting changes to a lake's past isotope composition requires a comprehensive understanding of contemporary controls. Here, δ18O and δ2H values of water in modern lakes exceeding roughly five hundred square kilometres are compiled (n > 35). Voluminous and seasonally mixed lakes - such as the North American Great Lakes - have the most homogenous stable isotope compositions, while perennially-stratified and shallow lakes show greater variability. A rudimentary stable isotope mass balance is used to assess evaporation fluxes from large lakes on Earth. The approach taken simultaneously constrains evaporation outputs for both oxygen and hydrogen stable isotopes by accounting for lake effects on the overlying atmosphere. Model development highlights important considerations such as isotopic stratification (Tanganyika), disequilibrium isotopic mass balances (Baikal), and non-steady hydrologic balances. Further, the isotope composition of Earth's continental surface water reservoir is calculated. This value - weighted to volume - is δ18O = -7.5±1.7 per mille relative to standard mean ocean water. The compiled data may be a useful tracer of continental evaporate in global atmospheric water cycle studies and could be coupled to climate models capable of incorporating oxygen-18 and deuterium tracers to improve or validate calculations of lake effects on regional water cycling.

  8. Diel vertical movements, and effects of infection by the cestode Schistocephalus solidus on daytime proximity of three-spined sticklebacks Gasterosteus aculeatus to the surface of a large Alaskan lake.

    PubMed

    Quinn, T P; Kendall, N W; Rich, H B; Chasco, B E

    2012-01-01

    We conducted a field study in Iliamna Lake, Alaska, to test the hypothesis that proximity of three-spined sticklebacks Gasterosteus aculeatus to the lake's surface during the daytime varies with macroparasitic cestode parasite Schistocephalus solidus infection in a manner consistent with enhanced vulnerability to avian predators. Extensive sampling in the lake and likelihood-based modeling revealed that sticklebacks displayed a diel vertical migration, being closer to the surface at night than during the evening and early morning. Additional sampling, also coupled with a likelihood-based modeling approach, showed that fish caught at the surface of the lake during the day were more often parasitized (76 vs. 65%), more heavily parasitized (26.8 vs. 22.7% of their body mass), and had larger individual parasites (0.24 vs. 0.20 g) than those caught at night. Parasite infection was related, non-linearly, to fish size, which also differed between day and night sampling at the surface. We performed statistical competitions among nested hierarchies of models that accounted for this effect of length. The most likely models indicated that fish captured during the day had greater parasite prevalence, higher parasite burdens, and larger parasites than did fish captured at night. Proximity to the surface during the day in this very clear lake would likely increase the vulnerability of sticklebacks to predation from birds, enabling completion of the parasite's lifecycle.

  9. Dominant microbial composition and its vertical distribution in saline meromictic Lake Kaiike (Japan) as revealed by quantitative oligonucleotide probe membrane hybridization.

    PubMed

    Koizumi, Yoshikazu; Kojima, Hisaya; Fukui, Manabu

    2004-08-01

    Vertical distributions of dominant bacterial populations in saline meromictic Lake Kaiike were investigated throughout the water column and sediment by quantitative oligonucleotide probe membrane hybridization. Three oligonucleotide probes specific for the small-subunit (SSU) rRNA of three groups of Chlorobiaceae were newly designed. In addition, three general domain (Bacteria, Archaea, and Eukarya)-specific probes, two delta-Proteobacteria-specific probes, a Chlorobiaceae-specific probe, and a Chloroflexi-specific probe were used after optimization of their washing conditions. The abundance of the sum of SSU rRNAs hybridizing with probes specific for three groups of Chlorobiaceae relative to total SSU rRNA peaked in the chemocline, accounting for up to 68%. The abundance of the delta-proteobacterial SSU rRNA relative to total SSU rRNA rapidly increased just below the chemocline up to 29% in anoxic water and peaked at the 2- to 3-cm sediment depth at ca. 34%. The abundance of SSU rRNAs hybridizing with the probe specific for the phylum Chloroflexi relative to total SSU rRNA was highest (31 to 54%) in the top of the sediment but then steeply declined with depth and became stable at 11 to 19%, indicating the robust coexistence of sulfate-reducing bacteria and Chloroflexi in the top of the sediment. Any SSU rRNA of Chloroflexi in the water column was under the detection limit. The summation of the signals of group-specific probes used in this study accounted for up to 89% of total SSU rRNA, suggesting that the DGGE-oligonucleotide probe hybridization approach, in contrast to conventional culture-dependent approaches, was very effective in covering dominant populations.

  10. Tectonic inheritance in the development of the Kivu - north Tanganyika rift segment of the East African Rift System: role of pre-existing structures of Precambrian to early Palaeozoic origin.

    NASA Astrophysics Data System (ADS)

    Delvaux, Damien; Fiama Bondo, Silvanos; Ganza Bamulezi, Gloire

    2017-04-01

    The present architecture of the junction between the Kivu rift basin and the north Tanganyika rift basin is that of a typical accommodation zone trough the Ruzizi depression. However, this structure appeared only late in the development of the Western branch of the East African Rift System and is the result of a strong control by pre-existing structures of Precambrian to early Palaeozoic origin. In the frame of a seismic hazard assessment of the Kivu rift region, we (Delvaux et al., 2016) constructed homogeneous geological, structural and neotectonic maps cross the five countries of this region, mapped the pre-rift, early rift and Late Quaternary faults and compiled the existing knowledge on thermal springs (assumed to be diagnostic of current tectonic activity along faults). We also produced also a new catalogue of historical and instrumental seismicity and defined the seismotectonic characteristics (stress field, depth of faulting) using published focal mechanism data. Rifting in this region started at about 11 Ma by initial doming and extensive fissural basaltic volcanism along normal faults sub-parallel to the axis of the future rift valley, as a consequence of the divergence between the Nubia and the Victoria plate. In a later stage, starting around 8-7 Ma, extension localized along a series of major border faults individualizing the subsiding tectonic basins from the uplifting rift shoulders, while lava evolved towards alkali basaltic composition until 2.6 Ma. During this stage, initial Kivu rift valley was extending linearly in a SSW direction, much further than its the actual termination at Bukavu, into the Mwenga-Kamituga graben, up to Namoya. The SW extremity of this graben was linked via a long oblique transfer zone to the central part of Lake Tanganyika, itself reactivating an older ductile-brittle shear zone. In the late Quaternary-early Holocene, volcanism migrated towards the center of the basin, with the development of the Virunga volcanic massif

  11. The development of irrigation and its influence on the transmission of bilharziasis in Tanganyika*

    PubMed Central

    Sturrock, R. F.

    1965-01-01

    Schistosoma mansoni and Schistosoma haematobium are widely distributed throughout East Africa, each being transmitted by several intermediate hosts. It is feared that the increased use of irrigation, which is proposed in Tanganyika to expand agricultural productivity, will also increase the incidence and intensity of schistosomal infection. Nine newly developed irrigation schemes have been examined to provide base-line data against which any future observations on the build-up of bilharziasis can be compared. A description is given in tabular form of each scheme together with the results of snail and parasite surveys conducted on and around it. These results are discussed in relation to the type of scheme and in the light of existing knowledge of bilharziasis in East Africa. The necessity and suitability of certain control measures are discussed. PMID:14310910

  12. Monophyletic origin of Lake Victoria cichlid fishes suggested by mitochondrial DNA sequences.

    PubMed

    Meyer, A; Kocher, T D; Basasibwaki, P; Wilson, A C

    1990-10-11

    Lake Victoria, together with its satellite lakes, harbours roughly 200 endemic forms of cichlid fishes that are classified as 'haplochromines' and yet the lake system is less than a million years old. This 'flock' has attracted attention because of the possibility that it evolved within the lake from one ancestral species and that biologists are thus presented with a case of explosive evolution. Within the past decade, however, morphology has increasingly emphasized the view that the flock may be polyphyletic. We sequenced up to 803 base pairs of mitochondrial DNA from 14 representative Victorian species and 23 additional African species. The flock seems to be monophyletic, and is more akin to that from Lake Malawi than to species from Lake Tanganyika; in addition, it contains less genetic variation than does the human species, and there is virtually no sharing of mitochondrial DNA types among species. These results confirm that the founding event was recent.

  13. Winter Lake Breezes near the Great Salt Lake

    NASA Astrophysics Data System (ADS)

    Crosman, Erik T.; Horel, John D.

    2016-05-01

    Case studies of lake breezes during wintertime cold air pools in Utah's Salt Lake Valley are examined. While summer breezes originating from the Great Salt Lake are typically deeper, of longer duration, and have higher wind speeds than winter breezes, the rate of inland penetration and cross-frontal temperature differences can be higher during the winter. The characteristics of winter breezes and the forcing mechanisms controlling them (e.g., snow cover, background flow, vertical stability profile, clouds, lake temperature, lake sheltering, and drainage pooling) are more complex and variable than those evident in summer. During the afternoon in the Salt Lake Valley, these lake breezes can lead to elevated pollution levels due to the transport of fine particle pollutants from over the Great Salt Lake, decreased vertical mixing depth, and increased vertical stability.

  14. 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.

  15. Pleistocene desiccation in East Africa bottlenecked but did not extirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes.

    PubMed

    Elmer, Kathryn R; Reggio, Chiara; Wirth, Thierry; Verheyen, Erik; Salzburger, Walter; Meyer, Axel

    2009-08-11

    The Great Lakes region of East Africa, including Lake Victoria, is the center of diversity of the mega-diverse cichlid fishes (Perciformes: Teleostei). Paleolimnological evidence indicates dramatic desiccation of this lake ca. 18,000-15,000 years ago. Consequently, the hundreds of extant endemic haplochromine species in the lake must have either evolved since then or refugia must have existed, within that lake basin or elsewhere, from which Lake Victoria was recolonized. We studied the population history of the Lake Victoria region superflock (LVRS) of haplochromine cichlids based on nuclear genetic analysis (12 microsatellite loci from 400 haplochomines) of populations from Lake Kivu, Lake Victoria, and the connected and surrounding rivers and lakes. Population genetic analyses confirmed that Lake Kivu haplochromines colonized Lake Victoria. Coalescent analyses show a 30- to 50-fold decline in the haplochromine populations of Lake Victoria, Lake Kivu, and the region ca. 18,000-15,000 years ago. We suggest that this coincides with drastic climatic and geological changes in the late Pleistocene. The most recent common ancestor of the Lake Victoria region haplochromines was estimated to have existed about 4.5 million years ago, which corresponds to the first radiation of cichlids in Lake Tanganyika and the origin of the tribe Haplochrominii. This relatively old evolutionary origin may explain the high levels of polymorphism still found in modern haplochromines. This degree of polymorphism might have acted as a "genetic reservoir" that permitted the explosive radiation of hundreds of haplochromines and their array of contemporary adaptive morphologies.

  16. Parallel life history evolution in mouthbrooding cichlids from the African Great Lakes

    PubMed Central

    Duponchelle, Fabrice; Paradis, Emmanuel; Ribbink, Anthony J.; Turner, George F.

    2008-01-01

    The existence of ancient deep-water lakes provides an opportunity to study the independent adaptation of aquatic organisms to pelagic, benthic, and rocky shore habitats. With improving resolution of their phylogenetic relationships, the many cichlid fish species endemic to the African Great Lakes Malawi, Tanganyika, and Victoria provide a significant resource for the comparative study of such evolutionary processes. Here, we show that cichlid lineages colonizing rocky shores and pelagic habitats in the different lakes have independently evolved larger eggs and lower fecundities than benthic lineages, suggesting parallel adaptive life-history evolution. By contrast, other pelagic teleost fishes in both marine and freshwater habitats, including African lakes, typically produce large numbers of very small eggs. Our results also suggest that decreased fecundity and increased egg size not only occurred independently in each lake but occurred independently in the colonization of rocky and pelagic habitats. PMID:18824688

  17. Parallel life history evolution in mouthbrooding cichlids from the African Great Lakes.

    PubMed

    Duponchelle, Fabrice; Paradis, Emmanuel; Ribbink, Anthony J; Turner, George F

    2008-10-07

    The existence of ancient deep-water lakes provides an opportunity to study the independent adaptation of aquatic organisms to pelagic, benthic, and rocky shore habitats. With improving resolution of their phylogenetic relationships, the many cichlid fish species endemic to the African Great Lakes Malawi, Tanganyika, and Victoria provide a significant resource for the comparative study of such evolutionary processes. Here, we show that cichlid lineages colonizing rocky shores and pelagic habitats in the different lakes have independently evolved larger eggs and lower fecundities than benthic lineages, suggesting parallel adaptive life-history evolution. By contrast, other pelagic teleost fishes in both marine and freshwater habitats, including African lakes, typically produce large numbers of very small eggs. Our results also suggest that decreased fecundity and increased egg size not only occurred independently in each lake but occurred independently in the colonization of rocky and pelagic habitats.

  18. The impact of the African Great Lakes on the regional climate in a dynamically downscaled CORDEX simulation (COSMO-CLM)

    NASA Astrophysics Data System (ADS)

    Thiery, W.; Panitz, H.; van Lipzig, N.

    2013-12-01

    Owing to the strong contrast in albedo, roughness and heat capacity between land and water, lakes significantly influence the exchange of moisture, heat and momentum between the surface and the boundary layer. To investigate this two-way interaction, a correct representation of lakes within regional climate models is essential. To this end, the one-dimensional lake parameterisation scheme FLake was recently coupled to the regional climate model COSMO-CLM (CCLM). One region where lakes constitute a key component of the climate system is the African Great Lakes region. In this study, the CCLM CORDEX-Africa evaluation simulation is dynamically downscaled from 0.44° (50 km) to 0.0625° (7 km) over East-Africa. The performance of two lake modules within CCLM are compared for the period 1999-2008: the default FLake scheme and the alternative Community Land Model. Model results are evaluated in a three-step procedure. First, the atmospheric state variables near-surface temperature, precipitation, surface energy fluxes, fractional cloud cover and column precipitable water are evaluated using in-situ based and satellite-derived products. Second, a comprehensive set of in-situ water temperature profile observations serves to evaluate the temporal evolution of water temperatures at three sites: Lake Kivu (Ishungu), Lake Tanganyika's northern basin (Kigoma) and southern basin (Mpulungu). Finally, spatial variability of surface temperatures in Lake Kivu and Lake Tanganyika are evaluated on the basis of satellite-derived lake surface temperatures. Subsequently, the preferred model configuration is used to quantify and understand effects by lakes reported for other regions in the world, such as a dampened diurnal temperature range, enhanced evaporation, modified surface layer stability, increased downwind precipitation, stronger winds, and the formation of local circulation patterns. This is achieved through comparison to a model integration excluding lake effects.

  19. Understanding the performance of the FLake model over the East-African Great Lakes

    NASA Astrophysics Data System (ADS)

    Thiery, Wim; Martynov, Andrey; Darchambeau, François; Plisnier, Pierre-Denis; Descy, Jean-Pierre; van Lipzig, Nicole

    2013-04-01

    As a one-dimensional lake parameterisation scheme, FLake has already been coupled to a large number of numerical weather prediction systems, regional climate models and general circulation models. However, even though FLake has therewith become a vital tool to investigate and predict climate change impacts on lacustrine ecosystems, it has never been thoroughly tested for tropical conditions. In this study, the ability of FLake to represent tropical mixolimnion temperatures is investigated for three locations in East-Africa: Lake Kivu, Lake Tanganyika's northern and southern basins. Meteorological observations from surrounding automatic weather stations are corrected and subsequently used to drive FLake, whereas a comprehensive set of water temperature profiles serves to evaluate the model at each site. Careful input data correction and model configuration allows to reproduce the observed mixed layer seasonality at Lake Kivu and Lake Tanganyika (northern and southern basins), with correct representation of both the mixed layer depth and temperature structure. In contrast, when FLake is forced with uncorrected meteorological observations or with ERA-Interim reanalysis data, a correct mixing cycle is predicted only for Lake Tanganyika's southern basin: this is mainly due to an underestimation of wind velocities. At Lake Kivu, an extensive sensitivity study reveals that FLake's water column temperatures are sensitive both to minimal variations in the external parameters (lake depth and water transparency) and to small changes in the meteorological driving data, in particular wind velocity. In each case, small modifications may already lead to a regime switch from the correctly represented seasonal mixolimnion deepening to either completely mixed or permanently stratified conditions. Near-surface water temperatures are however more robust, with acceptable predictions even when the seasonal mixing regime is not reproduced. Furthermore, a study of different initial

  20. Understanding the performance of the FLake model over two African Great Lakes

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    The ability of the one-dimensional lake model FLake to represent the mixolimnion temperatures for tropical conditions was tested for three locations in East Africa: Lake Kivu and Lake Tanganyika's northern and southern basins. Meteorological observations from surrounding automatic weather stations were corrected and used to drive FLake, whereas a comprehensive set of water temperature profiles served to evaluate the model at each site. Careful forcing data correction and model configuration made it possible to reproduce the observed mixed layer seasonality at Lake Kivu and Lake Tanganyika (northern and southern basins), with correct representation of both the mixed layer depth and water temperatures. At Lake Kivu, mixolimnion temperatures predicted by FLake were found to be sensitive both to minimal variations in the external parameters and to small changes in the meteorological driving data, in particular wind velocity. In each case, small modifications may lead to a regime switch, from the correctly represented seasonal mixed layer deepening to either completely mixed or permanently stratified conditions from ∼ 10 m downwards. In contrast, model temperatures were found to be robust close to the surface, with acceptable predictions of near-surface water temperatures even when the seasonal mixing regime is not reproduced. FLake can thus be a suitable tool to parameterise tropical lake water surface temperatures within atmospheric prediction models. Finally , FLake was used to attribute the seasonal mixing cycle at Lake Kivu to variations in the near-surface meteorological conditions. It was found that the annual mixing down to 60 m during the main dry season is primarily due to enhanced lake evaporation and secondarily to the decreased incoming long wave radiation, both causing a significant heat loss from the lake surface and associated mixolimnion cooling.

  1. Hydrogeology of the Lake Miona area, northeast Sumter County, Florida

    USGS Publications Warehouse

    Bradner, L.A.

    1986-01-01

    The Lake Miona area, in northeast Sumter County, is characterized by karstic depressions that contain lakes, ponds, and marshes that drain vertically to the upper Floridan aquifer. Lake Miona, Black Lake, and Cherry Lake are the prominent water features of the area. When the lake levels are lowest, the lakes are not connected, but at higher levels, they become connected and water flows eastward from Lake Miona through Black Lake to Cherry Lake. The chemical and biological conditions in the lakes are such that, although they support a large population of submerged aquatic plants, no problem with algae blooms was observed. (USGS)

  2. Stratigraphic framework and lake level history of Lake Kivu, East African Rift

    NASA Astrophysics Data System (ADS)

    Wood, Douglas A.; Scholz, Christopher A.

    2017-10-01

    Sediment cores and seismic reflection data acquired from the eastern basin of Lake Kivu, Rwanda reveal extensive limnologic variations due to changes in regional climate and basin structure. The eastern basin of the lake contains a sedimentary wedge which is > 1.5 km in thickness on its western side, and basal sediments are estimated to be at least 1.5 million years old. Sediments are likely to be thicker and older than this in the northern, Congolese basin of the lake. Above the ∼300 m iosbath only a thin layer of Holocene sediments are observed indication that this may have been the lake's high stand prior to that time. There are at least three erosional unconformities interpreted as desiccation or near-desiccation events which are estimated to have occurred at ∼475 ka, ∼100 ka, and ∼20 ka; the two most recent of these low stages likely developed during the African Megadrought and Last Glacial Maximum (LGM) periods. Following the LGM, the water levels rose to form a ∼100 m deep lake with its surface ∼370 m below the current lake level. The lake remained near that level for several thousand years and during this time the Virunga Volcanic Province expanded. At ∼12.2 ka a change to wetter climate conditions rapidly filled the lake to spill out of the Bukavu Bay basin southward toward Lake Tanganyika. Tephra sampled from the cores show that there have been at least 24 large local volcanic events since the early Holocene lake transgression.

  3. Big fish, little divergence: phylogeography of Lake Tanganyika’s giant cichlid, Boulengerochromis microlepis

    PubMed Central

    Koblmüller, Stephan; Odhiambo, Elizabeth A.; Sinyinza, Danny; Sturmbauer, Christian; Sefc, Kristina M.

    2014-01-01

    The largely endemic cichlid species flocks of the East African Great Lakes are among the prime examples for explosive speciation and adaptive radiation. Speciation rates differ among cichlid lineages, and the propensity to radiate has been linked to intrinsic and extrinsic factors such as sexual selection and ecological opportunity. Remarkably, only one cichlid tribe—the Boulengerochromini—comprises just a single species, Boulengerochromis microlepis, a predominantly piscivorous endemic of Lake Tanganyika and the world’s largest cichlid. While the lineage diverged from its closest relatives at the onset of the Lake Tanganyika radiation >8 MYA, mitochondrial control region sequences collected in this study dated the most recent common ancestor of B. microlepis to ~60–110 KYA. There was no evidence of phylogeographic structure in the lake-wide sample. Patterns of genetic diversity and demographic analyses were consistent with slow and steady population growth throughout the reconstructed timescale. Additionally, the shallow divergence within the species may be related to a possibly large variance in reproductive success in this highly fecund species. Trophic niche space restriction by sympatric piscivores, lack of geographic structure, low potential for sexual selection arising from the monogamous mating system and extinction may have contributed to keeping the lineage monotypic. PMID:25983338

  4. Measurements of slope distances and vertical angles at Mount Baker and Mount Rainier, Washington, Mount Hood and Crater Lake, Oregon, and Mount Shasta and Lassen Peak, California, 1980-1984

    USGS Publications Warehouse

    Chadwick, W.W.

    1985-01-01

    Personnel of the U.S.Geological Survey's Cascades Volcano Observatory established trilateration networks at Mount Baker, Mount Rainier, Mount Hood, Crater Lake, Mount Shasta, and Lassen Peak in 1980-1984. These networks are capable of detecting changes in slope distance of several centimeters or more. The networks were established to provide baseline information on potentially active volcanoes and were designed along guidelines found useful at Mount St. Helens. Periodic reoccupation of the networks is planned as part of the overall monitoring program of Cascades volcanoes. Methodology, slope distance and vertical angle data, maps of the networks, and benchmark descriptions are presented in this report. Written benchmark descriptions are augmented by photographs, which we have found by experience to very useful in relocating the marks. All repeat measurements at the six volcanoes are probably within measurement error.

  5. Vertical and temporal shifts in microbial communities in the water column and sediment of saline meromictic Lake Kaiike (Japan), as determined by a 16S rDNA-based analysis, and related to physicochemical gradients.

    PubMed

    Koizumi, Yoshikazu; Kojima, Hisaya; Oguri, Kazumasa; Kitazato, Hiroshi; Fukui, Manabu

    2004-06-01

    The vertical and temporal changes in microbial communities were investigated throughout the water column and sediment of the saline meromictic Lake Kaiike by PCR-denaturing gradient gel electrophoresis (DGGE) of 16S rDNA. Marked depth-related changes in microbial communities were observed at the chemocline and the sediment-water interface. However, no major temporal changes in the microbial community below the chemocline were observed during the sampling period, suggesting that the ecosystem in the anoxic zone of Lake Kaiike was nearly stable. Although the sequence of the most conspicuous DGGE band throughout the anoxic water and in the top of the microbial mat was most similar to that of an anoxic, photosynthetic, green sulphur bacterium, Pelodyction luteolum DSM273 (97% similarity), it represented a new phylotype. A comparison of DGGE banding patterns of the water column and sediment samples demonstrated that specific bacteria accumulated on the bottom from the anoxic water layers, and that indigenous microbial populations were present in the sediment. The measurements of bicarbonate assimilation rates showed significant phototrophic assimilation in the chemocline and lithoautotrophic assimilation throughout the anoxic water, but were not clearly linked with net sulphide turnover rates, indicating that sulphur and carbon metabolisms were not directly correlated.

  6. Persistence of neutral polymorphisms in Lake Victoria cichlid fish

    PubMed Central

    Nagl, Sandra; Tichy, Herbert; Mayer, Werner E.; Takahata, Naoyuki; Klein, Jan

    1998-01-01

    Phylogenetic trees for groups of closely related species often have different topologies, depending on the genes used. One explanation for the discordant topologies is the persistence of polymorphisms through the speciation phase, followed by differential fixation of alleles in the resulting species. The existence of transspecies polymorphisms has been documented for alleles maintained by balancing selection but not for neutral alleles. In the present study, transspecific persistence of neutral polymorphisms was tested in the endemic haplochromine species flock of Lake Victoria cichlid fish. Putative noncoding region polymorphisms were identified at four randomly selected nuclear loci and tested on a collection of 12 Lake Victoria species and their putative riverine ancestors. At all loci, the same polymorphism was found to be present in nearly all the tested species, both lacustrine and riverine. Different polymorphisms at these loci were found in cichlids of other East African lakes (Malawi and Tanganyika). The Lake Victoria polymorphisms must have therefore arisen after the flocks now inhabiting the three great lakes diverged from one another, but before the riverine ancestors of the Lake Victoria flock colonized the Lake. Calculations based on the mtDNA clock suggest that the polymorphisms have persisted for about 1.4 million years. To maintain neutral polymorphisms for such a long time, the population size must have remained large throughout the entire period. PMID:9826684

  7. Persistence of neutral polymorphisms in Lake Victoria cichlid fish.

    PubMed

    Nagl, S; Tichy, H; Mayer, W E; Takahata, N; Klein, J

    1998-11-24

    Phylogenetic trees for groups of closely related species often have different topologies, depending on the genes used. One explanation for the discordant topologies is the persistence of polymorphisms through the speciation phase, followed by differential fixation of alleles in the resulting species. The existence of transspecies polymorphisms has been documented for alleles maintained by balancing selection but not for neutral alleles. In the present study, transspecific persistence of neutral polymorphisms was tested in the endemic haplochromine species flock of Lake Victoria cichlid fish. Putative noncoding region polymorphisms were identified at four randomly selected nuclear loci and tested on a collection of 12 Lake Victoria species and their putative riverine ancestors. At all loci, the same polymorphism was found to be present in nearly all the tested species, both lacustrine and riverine. Different polymorphisms at these loci were found in cichlids of other East African lakes (Malawi and Tanganyika). The Lake Victoria polymorphisms must have therefore arisen after the flocks now inhabiting the three great lakes diverged from one another, but before the riverine ancestors of the Lake Victoria flock colonized the Lake. Calculations based on the mtDNA clock suggest that the polymorphisms have persisted for about 1.4 million years. To maintain neutral polymorphisms for such a long time, the population size must have remained large throughout the entire period.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  9. Vertical distributions of bound saturated fatty acids and compound-specific stable carbon isotope compositions in sediments of two lakes in China: implication for the influence of eutrophication.

    PubMed

    Wang, Lifang; Xiong, Yongqiang; Wu, Fengchang; Li, Qiuhua; Lin, Tian; Giesy, John P

    2014-11-01

    Lakes Dianchi (DC) and Bosten (BST) were determined to be at different stages of eutrophication, by use of total organic carbon content, bulk carbon isotopic composition, bulk nitrogen isotopic composition, and bound saturated fatty acid (BSFA) concentrations in sediment cores. A rapid increase in the supply of organic matter (OM) to DC began after the 1950s, while the environment and trophic status of BST remained constant as indicated by characteristics of OM input to sediments. The BSFA ratios of nC14 + nC16 + nC18/nC24 + nC26 + nC28 increase upward from 7 to 13 in the DC core, which are significantly greater than those from BST (2 to 3). This result is consistent with algae or bacteria being the dominant contribution of the OM increase induced by eutrophication in DC. The positive shift of nC16 compound-specific δ (13)C in the upper section might be an indicator of excess algal productivity, which was observed in the two lakes. The positive shifts of compound-specific δ (13)C of other BSFAs were also observed in the upper section of the core only from DC. The observed trends of compound-specific δ(13)C of BSFA originated from different sources became more consistent, which reflected the intensified eutrophication had profoundly affected production and preservation of OM in DC. The results observed for BST indicated that accumulation of algae did not affect the entire aquatic ecosystem until now.

  10. Evolution of opercle shape in cichlid fishes from Lake Tanganyika - adaptive trait interactions in extant and extinct species flocks

    PubMed Central

    Wilson, Laura A. B.; Colombo, Marco; Sánchez-Villagra, Marcelo R.; Salzburger, Walter

    2015-01-01

    Phenotype-environment correlations and the evolution of trait interactions in adaptive radiations have been widely studied to gain insight into the dynamics underpinning rapid species diversification. In this study we explore the phenotype-environment correlation and evolution of operculum shape in cichlid fishes using an outline-based geometric morphometric approach combined with stable isotope indicators of macrohabitat and trophic niche. We then apply our method to a sample of extinct saurichthyid fishes, a highly diverse and near globally distributed group of actinopterygians occurring throughout the Triassic, to assess the utility of extant data to inform our understanding of ecomorphological evolution in extinct species flocks. A series of comparative methods were used to analyze shape data for 54 extant species of cichlids (N = 416), and 6 extinct species of saurichthyids (N = 44). Results provide evidence for a relationship between operculum shape and feeding ecology, a concentration in shape evolution towards present along with evidence for convergence in form, and significant correlation between the major axes of shape change and measures of gut length and body elongation. The operculum is one of few features that can be compared in extant and extinct groups, enabling reconstruction of phenotype-environment interactions and modes of evolutionary diversification in deep time. PMID:26584885

  11. Evolution of opercle shape in cichlid fishes from Lake Tanganyika - adaptive trait interactions in extant and extinct species flocks.

    PubMed

    Wilson, Laura A B; Colombo, Marco; Sánchez-Villagra, Marcelo R; Salzburger, Walter

    2015-11-20

    Phenotype-environment correlations and the evolution of trait interactions in adaptive radiations have been widely studied to gain insight into the dynamics underpinning rapid species diversification. In this study we explore the phenotype-environment correlation and evolution of operculum shape in cichlid fishes using an outline-based geometric morphometric approach combined with stable isotope indicators of macrohabitat and trophic niche. We then apply our method to a sample of extinct saurichthyid fishes, a highly diverse and near globally distributed group of actinopterygians occurring throughout the Triassic, to assess the utility of extant data to inform our understanding of ecomorphological evolution in extinct species flocks. A series of comparative methods were used to analyze shape data for 54 extant species of cichlids (N = 416), and 6 extinct species of saurichthyids (N = 44). Results provide evidence for a relationship between operculum shape and feeding ecology, a concentration in shape evolution towards present along with evidence for convergence in form, and significant correlation between the major axes of shape change and measures of gut length and body elongation. The operculum is one of few features that can be compared in extant and extinct groups, enabling reconstruction of phenotype-environment interactions and modes of evolutionary diversification in deep time.

  12. Modeling the Sedimentary Infill of Lakes in the East African Rift: A Case Study of Multiple versus Single Rift Basin Segments

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Scholz, C. A.

    2016-12-01

    The sedimentary basins in the East African Rift are considered excellent modern examples for investigating sedimentary infilling and evolution of extensional systems. Some lakes in the western branch of the rift have formed within single-segment systems, and include Lake Albert and Lake Edward. The largest and oldest lakes developed within multi-segment systems, and these include Lake Tanganyika and Lake Malawi. This research aims to explore processes of erosion and sedimentary infilling of the catchment area in single-segment rift (SSR) and multi-segment rift (MSR) systems. We consider different conditions of regional precipitation and evaporation, and assess the resulting facies architecture through forward modeling, using state-of-the-art commercial basin modeling software. Dionisos is a three-dimensional numerical stratigraphic forward modeling software program, which simulates basin-scale sediment transport based on empirical water- and gravity-driven diffusion equations. It was classically used to quantify the sedimentary architecture and basin infilling of both marine siliciclastic and carbonate environments. However, we apply this approach to continental rift basin environments. In this research, two scenarios are developed, one for a MSR and the other for a SSR. The modeled systems simulate the ratio of drainage area and lake surface area observed in modern Lake Tanganyika and Lake Albert, which are examples of MSRs and SSRs, respectively. The main parameters, such as maximum subsidence rate, water- and gravity-driven diffusion coefficients, rainfall, and evaporation, are approximated using these real-world examples. The results of 5 million year model runs with 50,000 year time steps show that MSRs are characterized by a deep water lake with relatively modest sediment accumulation, while the SSRs are characterized by a nearly overfilled lake with shallow water depths and thick sediment accumulation. The preliminary modeling results conform to the features

  13. ARE LAKES GETTING WARMER? REMOTE SENSING OF LARGE LAKE TEMPERATURES

    EPA Science Inventory

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

  14. ARE LAKES GETTING WARMER? REMOTE SENSING OF LARGE LAKE TEMPERATURES

    EPA Science Inventory

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  16. Molecular phylogenetic investigations of the Viviparidae (Gastropoda: Caenogastropoda) in the lakes of the Rift Valley area of Africa.

    PubMed

    Sengupta, Mita E; Kristensen, Thomas K; Madsen, Henry; Jørgensen, Aslak

    2009-09-01

    The freshwater gastropod family Viviparidae is nearly cosmopolitan, but absent from South America. On the African continent, two genera are recognized; the widespread Bellamya and the monotypic Neothauma, which is confined to Lake Tanganyika. Most of the African Bellamya species are confined to the major lakes of the Rift Valley area in Africa, i.e. Lake Albert, Lake Malawi, Lake Mweru, and Lake Victoria. The phylogenetic analyses of mitochondrial (COI and 16S) and nuclear (H3, 18S and 28S) DNA inferred three major lake-clades; i.e. Lake Victoria/Kyoga/Albert, Lake Malawi and Lake Mweru/Bangweulu. The endemic B. rubicunda from Lake Albert and B. unicolor from Lake Kyoga were inferred to be part of the Lake Victoria clade. Bellamya capillata as identified by shell characters was polyphyletic in gene trees. The monophyletic Bellamya species radiation in Lake Malawi was most nearly related to the Lake Victoria/Kyoga/Albert-clade. Taxa from the Zambian lakes, Mweru and Bangweulu, were inferred together and placed ancestral to the other lakes. Neothauma tanganyicense was inferred as the sister-group to the Zambian Bellamya. Within the lake-clades the endemic radiations show very low genetic diversities (0-4.1% in COI), suggesting much faster morphological divergence than molecular divergence. Alternatively, Bellamya in Africa constitutes only a few species with several sub-species or eco-phenotypic morphs. The African viviparids were inferred to be the sister-group to a clade comprising Asian species, and the relatively low genetic diversity between the clades (12.6-15.5% in COI) makes a recent Miocene dispersal event from Asia to Africa much more likely than an ancient Gondwana vicarience distribution.

  17. Lake level fluctuations synchronize genetic divergences of cichlid fishes in African lakes.

    PubMed

    Sturmbauer, C; Baric, S; Salzburger, W; Rüber, L; Verheyen, E

    2001-02-01

    Water level fluctuations are important modulators of speciation processes in tropical lakes, in that they temporarily form or break down barriers to gene flow among adjacent populations and/or incipient species. Time estimates of the most recent major lowstands of the three African Great Lakes are thus crucial to infer the relative timescales of explosive speciation events in cichlid species flocks. Our approach combines geological evidence with genetic divergence data of cichlid fishes from the three Great East African Lakes derived from the fastest-evolving mtDNA segment. Thereby, we show for each of the three lakes that individuals sampled from several populations which are currently isolated by long geographic distances and/or deep water form clusters of equally closely related haplotypes. The distribution of identical or equally closely related haplotypes in a lake basin allows delineation of the extent of lake level fluctuations. Our data suggest that the same climatic phenomenon synchronized the onset of genetic divergence of lineages in all three species flocks, such that their most recent evolutionary history seems to be linked to the same external modulators of adaptive radiation. A calibration of the molecular clock of the control region was elaborated by gauging the age of the Lake Malawi species flock through the divergence among the utaka-cichlid and the mbuna-cichlid lineages to minimally 570,000 years and maximally 1 Myr. This suggests that the low-lake-level period which established the observed patterns of genetic relatedness dates back less than 57,000 years, probably even to 17,000-12,400 years ago, when Lake Victoria dried up and Lakes Malawi and Tanganyika were also low. A rapid rise of all three lakes about 11,000 years ago established the large-scale population subdivisions observed today. Over that period of time, a multitude of species originated in Lakes Malawi and Victoria with an impressive degree of morphological and ecological

  18. The impact of the African Great Lakes on the regional climate in a dynamically downscaled CORDEX simulation

    NASA Astrophysics Data System (ADS)

    Thiery, Wim; Panitz, Hans-Jürgen; Davin, Edouard; van Lipzig, Nicole

    2014-05-01

    Owing to the strong contrast in albedo, roughness and heat capacity between land and water, lakes significantly influence the exchange of moisture, heat and momentum between the surface and the boundary layer. To investigate this two-way interaction, a correct representation of lakes within regional climate models is essential. To this end, the one-dimensional lake parameterisation scheme FLake was recently coupled to the regional climate model COSMO-CLM (CCLM). One region where lakes constitute a key component of the climate system is the African Great Lakes region. In this study, the CCLM CORDEX-Africa evaluation simulation is dynamically downscaled from 0.44° (50 km) to 0.0625° (7 km) over East-Africa, an unprecedented resolution for this region. The performance of different CCLM configurations are compared for the period 1999-2008: in particular, CCLM is tested for its sensitivity to the choice of the lake surface temperature description (SST, FLake, an improved version of FLake and Hostetler) and the land surface model (Terra and Community Land Model). Model results are evaluated in a three-step procedure. First, the atmospheric state variables near-surface temperature, precipitation, surface energy fluxes, fractional cloud cover and column precipitable water are evaluated using in-situ based and satellite-derived products. Second, a comprehensive set of in-situ water temperature profile observations serves to evaluate the temporal evolution of water temperatures at three sites: Lake Kivu (Ishungu), Lake Tanganyika's northern basin (Kigoma) and southern basin (Mpulungu). Finally, spatial variability of surface temperatures in Lake Kivu and Lake Tanganyika are evaluated on the basis of satellite-derived lake surface temperatures. Subsequently, the preferred model configuration is used to quantify and understand effects by lakes reported for other regions in the world, such as a dampened diurnal temperature range, enhanced evaporation, modified surface layer

  19. 13C/Palynological evidence of differential residence times of organic carbon prior to its sedimentation in East African Rift Lakes and peat bogs

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, Claude; Aucour, Anne-Marie; Bonnefille, Raymonde; Riollet, Guy; Vincens, Annie; Williamson, David

    Most terrestrial plants producing large amounts of organic matter in the East African Rift follow the Calvin (C3) photosynthetic pathway. Their end products have δ13C values of ca. -27 ± 2‰ (vs. PDB). On the contrary, most Cyperaceae (notably Cyperus papyrus and C. latifolius) are characterized by higher 13C contents ° 13C = -10.5 ± 1‰ ) in relation to their Hatch and Slack (C4) photosynthetic cycle. In consequence, δ13C values in total organic matter (TOM) from peat bog or lake cores essentially responded to the proportion of detritus from C4-Cyperaceae. Immediate evidence of the development or disappearance of Cyperaceae around lake margins or in peat bogs can be found in pollen assemblages. Lag times between pollen signals and correlative ° 13C shifts in TOM from cores are therefore indicative of the residence time of organic matter prior to its sedimentation. Delayed sedimentation of TOM will result in 14C anomalies which depend on several parameters, most of them being site specific as shown by examples from a peat bog in Burundi and from southern Lake Tanganyika. An independent assessment of the chronology by high resolution paleomagnetic correlations indicates a ca. 1.5 ka apparent 14C age of TOM in Lake Tanganyika at the Pleistocene-Holocene transition.

  20. Pleistocene desiccation in East Africa bottlenecked but did not extirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes

    PubMed Central

    Elmer, Kathryn R.; Reggio, Chiara; Wirth, Thierry; Verheyen, Erik; Salzburger, Walter; Meyer, Axel

    2009-01-01

    The Great Lakes region of East Africa, including Lake Victoria, is the center of diversity of the mega-diverse cichlid fishes (Perciformes: Teleostei). Paleolimnological evidence indicates dramatic desiccation of this lake ca. 18,000–15,000 years ago. Consequently, the hundreds of extant endemic haplochromine species in the lake must have either evolved since then or refugia must have existed, within that lake basin or elsewhere, from which Lake Victoria was recolonized. We studied the population history of the Lake Victoria region superflock (LVRS) of haplochromine cichlids based on nuclear genetic analysis (12 microsatellite loci from 400 haplochomines) of populations from Lake Kivu, Lake Victoria, and the connected and surrounding rivers and lakes. Population genetic analyses confirmed that Lake Kivu haplochromines colonized Lake Victoria. Coalescent analyses show a 30- to 50-fold decline in the haplochromine populations of Lake Victoria, Lake Kivu, and the region ca. 18,000–15,000 years ago. We suggest that this coincides with drastic climatic and geological changes in the late Pleistocene. The most recent common ancestor of the Lake Victoria region haplochromines was estimated to have existed about 4.5 million years ago, which corresponds to the first radiation of cichlids in Lake Tanganyika and the origin of the tribe Haplochrominii. This relatively old evolutionary origin may explain the high levels of polymorphism still found in modern haplochromines. This degree of polymorphism might have acted as a “genetic reservoir” that permitted the explosive radiation of hundreds of haplochromines and their array of contemporary adaptive morphologies. PMID:19651614

  1. THE VERTICAL

    NASA Technical Reports Server (NTRS)

    Albert, Stephen L.; Spencer, Jeffrey B.

    1994-01-01

    'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.

  2. The Thermal History of the East African Rift Lakes Region Since the Last Glacial Maximum Using TEX86 Paleothermometry

    NASA Astrophysics Data System (ADS)

    Berke, M. A.; Johnson, T. C.; Werne, J. P.; Schouten, S.; Sinninghe Damsté, J. S.

    2008-12-01

    We present preliminary results from a study using the TEX86 temperature proxy from sediments of East African Rift Lakes (including Lakes Turkana, Albert, and Malawi) to reconstruct the thermal history of tropical Africa for the last ~ 20,000 years at a subcentennial to multicentennial resolution. The TEX86 proxy, based on tetraether membrane lipids produced by lacustrine Crenarchaeota, has been shown to be successful at recording lake surface temperatures of some large lakes, including Lakes Malawi and Tanganyika, while providing unreasonable surface temperatures for lakes that receive a large input of soil material. The East African Rift Lakes are climatically sensitive, with the majority of water loss due to evaporation rather than outflow. Thus, they are useful for paleoclimate studies, being sensitive to even small changes in aridity. Temperature records from the northern and central basins of Lake Malawi agree well and fall within modern surface lake temperatures. A 2.5°C cooling is evident during the Younger Dryas in the northern basin record, with no response seen in the central basin. We are currently investigating mechanisms to explain why both records show a gradual cooling of 3°C during the late Holocene. Lake Albert shows an intriguing two-step cooling during the Younger Dryas, reaching temperatures 2.5°C lower than temperatures preceding or following this interval. The temperature record of Lake Turkana shows an interesting ~ 500 year cyclicity of low temperatures punctuated by abrupt warming events. Lakes Turkana and Albert show TEX86 paleotemperatures considerably lower (8°C cooler in Lake Albert and ~ 4°C cooler in Lake Turkana) than modern surface water temperatures. Although these records appear to fall in the range of temporal variability, these temperature discrepancies may indicate varying Crenarcheotal populations between lakes or other influencing factors.

  3. A pharyngeal jaw evolutionary innovation facilitated extinction in Lake Victoria cichlids.

    PubMed

    McGee, Matthew D; Borstein, Samuel R; Neches, Russell Y; Buescher, Heinz H; Seehausen, Ole; Wainwright, Peter C

    2015-11-27

    Evolutionary innovations, traits that give species access to previously unoccupied niches, may promote speciation and adaptive radiation. Here, we show that such innovations can also result in competitive inferiority and extinction. We present evidence that the modified pharyngeal jaws of cichlid fishes and several marine fish lineages, a classic example of evolutionary innovation, are not universally beneficial. A large-scale analysis of dietary evolution across marine fish lineages reveals that the innovation compromises access to energy-rich predator niches. We show that this competitive inferiority shaped the adaptive radiation of cichlids in Lake Tanganyika and played a pivotal and previously unrecognized role in the mass extinction of cichlid fishes in Lake Victoria after Nile perch invasion. Copyright © 2015, American Association for the Advancement of Science.

  4. Lead cycling in an acidic Adirondack Lake

    SciTech Connect

    White, J.R.; Driscoll, C.T.

    1985-12-01

    Temporal and spatial variations in the concentration and transport of Pb were observed in acidic Darts Lake (Adirondack State Park, NY). Vertical deposition of Pb through the water column was most pronounced during stratification periods (winter and summer), while during high flow (spring and autumn) Pb was more conservative within the lake. Deposition of particulate Pb was strongly correlated with Al and organic carbon deposition. Increases in metal (Pb and Al) deposition occurred during periods of increasing pH. It appears that in-lake formation of particulate Al enhances the vertical transport of Pb in Darts Lake.

  5. A Revised Holocene History of Lake Kivu, East Africa

    NASA Astrophysics Data System (ADS)

    Votava, J. E.; Johnson, T. C.; Hecky, R. E.

    2013-12-01

    The great lakes of the East African Rift valley are a vast chain of lakes formed in a region of active tectonics. These large, deep lakes are relatively old and many (e.g. Tanganyika, Malawi, and Turkana) have greatly influenced our understanding of terrestrial, tropical East African paleoclimate. Lake Kivu (max depth, 485m) sits at the heart of these rift lakes, north of Lake Tanganyika between the Democratic Republic of the Congo and Rwanda (roughly 250 km west of Lake Victoria). At over 1,400 meters in elevation, this 2,060 km2 mesotrophic lake has a complex stratification regime imposed by hydrothermal springs and deep waters supersaturated at STP in CO2 and CH4 gasses. The active Virunga Volcanoes to the north of the lake supply heated, high-salinity waters below 280 meters water depth maintaining the modern crenogenic meromixis. Based on detailed studies of diatom assemblages and bulk sedimentology, previous workers have suggested this hydrothermal activity began roughly 5,000 years BP. Unfortunately, dating and stratigraphic correlations of these original cores from the 1970 Woods Hole Oceanographic Institution's expedition have been problematic. Here we offer an improved chronology and new carbonate analyses from cores recovered in 2012 and 2013. Our AMS radiocarbon ages come from six terrigeneous macrofossils spanning the last 9,100 years (cal BP). These ages suggest a rather high sedimentation rate on the order of 70cm/kyr, and hence, our 8 m-long core provides us with a high-resolution lake history for the past 10,000 years. Most notable over the past 5,000 years in the lake history is the repeated onset and cessation of carbonate deposition, punctuated by organic-rich intervals. Earlier studies of the Woods Hole cores placed the onset of carbonate deposition at ca. 11,000 years BP suggesting changes in lake hydrology (i.e. closed to open), while the abrupt cessation of carbonate was dated at ca. 5,000 years BP and attributed to the beginning of

  6. 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)…

  7. Evolution of predator-prey interactions in ancient lakes: implications for coevolution in marine environments

    SciTech Connect

    Cohen, A.

    1985-01-01

    Highly generalized predator-prey interrelationships are a hallmark of most lacustrine ecosystems where accommodation to the physical environment plays the major role in determining organismal distributions. Since the vast majority of lakes are ephemeral on a geological and evolutionary times scale, dispersal, rather than organism interaction, appears to be the dominant selective theme in lacustrine species evolution. In a few, very long lasting lakes, notably modern Lakes Tanganyika (Africa) and Baikal (USSR) and ancient lakes of the Brazilian Rift (Cretaceous) and Snake River Plain (Tertiary), invertebrates and fish occur which demonstrate the development of intense biological accommodation in coevolving predator-prey interactions. Shell crushing experiments on 2 endemic Tanganyikan gastropods, Lavigeria nassa and Spekia zonata show them to be comparable to warm temperature marine species in terms of grow load strength: 1-2 orders of magnitude stronger than confamilial cosmopolitan species from more ephemeral lakes in the same region of Africa. Shell repair is commonly observed in these and other Tanganyikan endemic snails although it is exceedingly rare inmost other lakes. The study of these early stages of evolutionary processes and rates in coevolving predator-prey systems in isolated lacustrine microcosms has important implications for those paleontologists concerned with marine invertebrates. It may shed considerable light on the interpretation of such events as the marine Mesozoic Revolution.

  8. Water-quality and lake-stage data for Wisconsin lakes, water year 1996

    USGS Publications Warehouse

    ,

    1997-01-01

    The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected includes measurements of lake stage and in-lake water quality. Graphs of Secchi depths, surface totalphosphorus and chlorophyll-a concentrations versus time are included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, drainage area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data-Wisconsin, 1996."

  9. Porewater salinity reveals past lake-level changes in Lake Van, the Earth's largest soda lake.

    PubMed

    Tomonaga, Yama; Brennwald, Matthias S; Livingstone, David M; Kwiecien, Olga; Randlett, Marie-Ève; Stockhecke, Mona; Unwin, Katie; Anselmetti, Flavio S; Beer, Jürg; Haug, Gerald H; Schubert, Carsten J; Sturm, Mike; Kipfer, Rolf

    2017-03-22

    In closed-basin lakes, sediment porewater salinity can potentially be used as a conservative tracer to reconstruct past fluctuations in lake level. However, until now, porewater salinity profiles did not allow quantitative estimates of past lake-level changes because, in contrast to the oceans, significant salinity changes (e.g., local concentration minima and maxima) had never been observed in lacustrine sediments. Here we show that the salinity measured in the sediment pore water of Lake Van (Turkey) allows straightforward reconstruction of two major transgressions and a major regression that occurred during the last 250 ka. We observed strong changes in the vertical salinity profiles of the pore water of the uppermost 100 m of the sediments in Lake Van. As the salinity balance of Lake Van is almost at steady-state, these salinity changes indicate major lake-level changes in the past. In line with previous studies on lake terraces and with seismic and sedimentological surveys, we identify two major transgressions of up to +105 m with respect to the current lake level at about 135 ka BP and 248 ka BP starting at the onset of the two previous interglacials (MIS5e and MIS7), and a major regression of about -200 m at about 30 ka BP during the last ice age.

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

    EPA Science Inventory

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

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

    EPA Science Inventory

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

  12. Lake Tahoe

    EPA Pesticide Factsheets

    Information on the Lake Tahoe watershed, EPA's protection efforts, water quality issues, effects of climate change, Lake Tahoe Total Maximum Daily Load (TMDL), EPA-sponsored projects, list of partner agencies.

  13. Indian Ocean Climate event brings floods to East Africa's lakes and the Sudd Marsh

    NASA Astrophysics Data System (ADS)

    Birkett, Charon; Murtugudde, Ragu; Allan, Tony

    During an El Niño, the expected rainfall increase over most of the Lake Victoria catchment area is ˜15-25%. However, due to anomalous warming of the western equatorial Indian Ocean during 1997, strong convection developed over parts of the Horn and eastern Africa. This resulted in a much larger 20-160% precipitation excess during the “short rainy” season. Satellite radar altimetry data reveals that not only did Lake Victoria rise by ˜1.7 m, but that the rainfall event similarly affected lakes Tanganyika, Malawi and Turkana. In addition, the seasonal level minima of the Sudd marshes and Lakes T'ana and Nasser continue to increase. Such a rainfall event will have severe, long-term consequences for the natural surface flows and storages along the White Nile. Based on the hydrological impacts of the historic 1961 East Africa event, we can expect the current high levels of Lake Victoria to be maintained for the remainder of this decade. In addition, we anticipate a major expansion of the permanent swamp regions of the Sudd marshes over the forthcoming seasons. Blue Nile flows, further enhanced by the above-average 1998 rainfall season, can also be expected to remain high, at least until early 1999.

  14. Lake Powell

    Atmospheric Science Data Center

    2014-05-15

    article title:  Lake Powell     View Larger Image ... format (14.42 mb)   This true-color image over Lake Powell was acquired by Multi-angle Imaging SpectroRadiometer (MISR) in late March 2000. Lake Powell was formed with the construction of the Glen Canyon Dam in 1963, on ...

  15. Lake Superior Ventilation and Dissolved Oxygen Cycle

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Tokos, K.; Gregory, C.

    2016-02-01

    Lake Superior is one of the largest lakes in world yet its circulation, especially in the interior, is not well understood. Ventilation rate of the lake interior is key to determining the vertical distribution and fate of natural and anthropogenic tracers. In this study, we utilize "age" and "dye" tracers in a realistically configured numerical model of Lake Superior to characterize its ventilation. We find that Lake Superior is preferentially ventilated over rough bathymetry and that spring overturn following a very cold winter does not completely ventilate the interior. Also, dissolved oxygen in Lake Superior is not a good proxy of ventilation age, as expected from oceanography, because the lake is so strongly physically dominated.

  16. Transient Tsunamis in Lakes

    NASA Astrophysics Data System (ADS)

    Couston, L.; Mei, C.; Alam, M.

    2013-12-01

    A large number of lakes are surrounded by steep and unstable mountains with slopes prone to failure. As a result, landslides are likely to occur and impact water sitting in closed reservoirs. These rare geological phenomena pose serious threats to dam reservoirs and nearshore facilities because they can generate unexpectedly large tsunami waves. In fact, the tallest wave experienced by contemporary humans occurred because of a landslide in the narrow bay of Lituya in 1958, and five years later, a deadly landslide tsunami overtopped Lake Vajont's dam, flooding and damaging villages along the lakefront and in the Piave valley. If unstable slopes and potential slides are detected ahead of time, inundation maps can be drawn to help people know the risks, and mitigate the destructive power of the ensuing waves. These maps give the maximum wave runup height along the lake's vertical and sloping boundaries, and can be obtained by numerical simulations. Keeping track of the moving shorelines along beaches is challenging in classical Eulerian formulations because the horizontal extent of the fluid domain can change over time. As a result, assuming a solid slide and nonbreaking waves, here we develop a nonlinear shallow-water model equation in the Lagrangian framework to address the problem of transient landslide-tsunamis. In this manner, the shorelines' three-dimensional motion is part of the solution. The model equation is hyperbolic and can be solved numerically by finite differences. Here, a 4th order Runge-Kutta method and a compact finite-difference scheme are implemented to integrate in time and spatially discretize the forced shallow-water equation in Lagrangian coordinates. The formulation is applied to different lake and slide geometries to better understand the effects of the lake's finite lengths and slide's forcing mechanism on the generated wavefield. Specifically, for a slide moving down a plane beach, we show that edge-waves trapped by the shoreline and free

  17. Lake level change and total water discharge in East Africa Rift Valley from satellite-based observations

    NASA Astrophysics Data System (ADS)

    Hassan, Ayman A.; Jin, Shuanggen

    2014-06-01

    The measurement of total basin water discharge is important for understanding the hydrological and climatologic issues related to the water and energy cycles. Climatic extreme events are normal climatic occurrences in Africa. For example, extensive droughts are regular features in the last few decades in parts of East Africa, which suffers from a lack of in situ observations as well as a lack of regional hydrological models. In this study, multi-disciplinary different types of space-borne observations and global hydrological models are used to study total water discharge in the Great Rift Valley of East Africa (i.e. Lakes Victoria, Tanganyika, and Malawi) from January 2003 to December 2012. The data include the following: (1) total water storage (TWS) variations from Gravity Recovery and Climate Experiment (GRACE), (2) the lake level variations from Satellite Alimetric data, (3) rainfall from Tropical Rainfall Measurement Mission (TRMM) products, (4) soil moisture from WaterGAP Global Hydrology Model (WGHM), and (5) water fluxes from Global Land Data Assimilation System (GLDAS). Results show that a significant decline in the average lake level is found for all of the three lakes between 2003 and 2006. GRACE TWS variations of the whole basin area show the same pattern of variation as the average lake level variations estimated from Altimetric data. The TWS in the basin area of Lakes Victoria and Malawi is governed by the surface water stored in each lake itself, while for Lake Tanganyika, it is governed by both surface water and the soil moisture content in the basin area. Furthermore, the effect of rainfall on TWS is also studied. A phase lag of ~ 2 months is found between TRMM rainfall and GRACE TWS (generally, rainfall precedes the GRACE TWS) for the three lakes. In addition, the regional evapotranspiration ET is estimated from the water balance equation using GRACE land-water solutions, rainfall data from TRMM and runoff values obtained as a fraction of rainfall

  18. Tropical Lake Levels and Their Relationship to Rainfall

    NASA Astrophysics Data System (ADS)

    Ricko, M.; Carton, J.; Birkett, C. M.

    2009-12-01

    , except Lake Turkana, have pronounced seasonal cycles, with the largest seasonal cycles occurring for the lakes in high rainfall regions: Kainji in Africa, Balbina in South America, and Lake Tonle Sap in Southeast Asia. With the seasonal cycle removed, the east African rift valley lakes (Turkana, Tanganyika, Mweru) show pronounced rises in 1997-8 in response to the combined effects of El Niño and the Indian Ocean dipole. In contrast, the Central and South American lakes (Nicaragua and Balbina) show significant level decrease for the same time period. There is also evidence of rapid increases in lake level in response to tropical cyclones (Nicaragua and Malawi). At short intraseasonal periods, Lake Tonle Sap shows evidence of a 30-60 day fluctuation driven by rainfall fluctuations partly associated with the Madden-Julian Oscillation. These results show noticeable climate impacts on tropical lake levels.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  20. Holocene TEX86 temperature reconstructions from Lake Turkana, East Africa

    NASA Astrophysics Data System (ADS)

    Berke, M. A.; Johnson, T. C.; Werne, J. P.; Schouten, S.; Sinninghe Damsté, J. S.

    2009-12-01

    We present new high resolution Holocene lake surface temperature records from Lake Turkana, East Africa. These two TEX86 reconstructions, from the northern and southern basins of the lake, capture ~90 year resolution of climate patterns seen in this closed-basin system, as well as the thermal water dynamics between the two basins. The modern lake experiences surface temperatures in the northern basin ~1-3 °C warmer than the southern basin, due to upwelling in the southern basin induced by the predominant southerly winds. The paleotemperature records show parallel trends to this modern basinal temperature gradient, averaging ~1.5 °C warmer in the northern basin than the southern during the ~2000 years of record overlap (~450-2500 ybp). Some temperature intervals with coverage in both basins show strong agreement (i.e. ~2600-2000 Cal ybp), whereas increased wind-generated upwelling events may be responsible for periods that appear strongly antiphased (i.e. 2000-1600 Cal ybp) between basins. There does not appear to be any evidence of warming into the Medieval Warm Period (MWP, ~800-1200AD) or cooling at the start of the Little Ice Age (LIA, ~600 ybp). The southern basin temperature record indicates a substantial ~5 °C warming culminating in a thermal maximum ~5ka, immediately followed by ~3 °C cooling. This supports previous observations of an anomalously warm interval ~5ka documented in lake surface temperature records from Lakes Malawi and Tanganyika. A similar Holocene thermal maximum ~5ka has also been described from the Indian Ocean off the coast of Somalia (3°11’N, 50°26’E) (Bard et al., 1997). The abundance of these records now point to this being the warmest or one of the warmest intervals in the Holocene in tropical East Africa and indicates this may be a widespread regional climate response. Although these temperature trends appear reasonable, overall TEX86 temperatures for Lake Turkana are considerably lower than modern surface water temperatures

  1. Water quality of selected lakes in Mount Rainier National Park, Washington, with respect to lake acidification

    SciTech Connect

    Turney, G.L.; Dion, N.P.; Sumioka, S.S.

    1986-01-01

    Thirteen lakes in Mount Rainier National park were evaluated for general chemical characteristics, sensitivity to acidification by acidic precipitation, and degree of existing acidification. The lakes studies were Allen, one of the Chenuis group, Crescent, Crystal, Eleanor, Fan, one of the Golfen group, Marsh, Mowich, Mystic, Shriner, and two unnamed lakes. The lakes were sampled in August 1983. The major cations were calcium and sodium, and the major anion was bicarbonate. Alkalinity concentrations ranged from 2.1 to 9.0 mg/L in 12 of the lakes. Allen Lake was the exception, having an alkalinity concentration of 27 mg/L. The pH values for all of the lakes ranged from 5.8 to 6.5. In most of the lakes, vertical profiles of temperature, dissolved oxygen, pH, and specific conductance were relatively uniform. Exceptions to general water quality patterns were observed in three lakes. Allen Lake had a specific conductance value of 58 Microsiemens/cm. The lake of the Golfen group was anaerobic at the bottom and had relatively high concentrations of dissolved organic carbon and dissolved metals, and a lower light transmission than the other lakes studied. One of the unnamed lakes had relatively high concentrations of phytoplankton and dissolved organic carbon and relatively low levels of light transmission. Comparisons of lake data to acid-sensitivity thresholds for specific conductance and alkalinity indicated that all of the lakes except Allen would be sensitive to acidic precipitation. The small sizes of the lakes, and their locations in basins of high precipitation and weathering-resistant rock types, enhance their sensitivity. None of the lakes in this study appeared to be presently acidified.

  2. Comparison of the hydrogeology and water quality of a ground-water augmented lake with two non-augmented lakes in northwest Hillsborough County, Florida

    USGS Publications Warehouse

    Metz, Patricia A.; Sacks, Laura A.

    2002-01-01

    The hydrologic effects associated with augmenting a lake with ground water from the Upper Floridan aquifer were examined in northwest Hillsborough County, Florida, from June 1996 through May 1999. The hydrogeology, ground-water flow patterns, water budgets, and water-quality characteristics were compared between a lake that has been augmented for more than 30 years (Round Lake) and two nearby non-augmented lakes (Dosson Lake and Halfmoon Lake). Compared to the other study lakes, Round Lake is in a more leakage-dominated hydrogeologic setting. The intermediate confining unit is thin or highly breached, which increases the potential for vertical ground-water flow. Round Lake has the least amount of soft, organic lake-bottom sediments and the lake bottom has been dredged deeper and more extensively than the other study lakes, which could allow more leakage from the lake bottom. The area around Round Lake has experienced more sinkhole activity than the other study lakes. During this study, three sinkholes developed around the perimeter of the lake, which may have further disrupted the intermediate confining unit. Ground-water flow patterns around Round Lake were considerably different than the non-augmented lakes. For most of the study, ground-water augmentation artificially raised the level of Round Lake to about 2 to 3 feet higher than the adjacent water table. As a result, lake water recharged the surficial aquifer around the entire lake perimeter, except during very wet periods when ground-water inflow occurred around part of the lake perimeter. The non-augmented lakes typically had areas of ground-water inflow and areas of lake leakage around their perimeter, and during wet periods, ground-water inflow occurred around the entire lake perimeter. Therefore, the area potentially contributing ground water to the non-augmented lakes is much larger than for augmented Round Lake. Vertical head loss within the surficial aquifer was greater at Round Lake than the other

  3. Primary and Bacterial Production in Two Dimictic Indiana Lakes

    PubMed Central

    Lovell, Charles R.; Konopka, Allan

    1985-01-01

    The relationship between primary and bacterial production in two dimictic Indiana lakes with different primary productivities was examined during the summer stratification period in 1982. Primary production rates were calculated from rates of H14CO3− incorporation by natural samples, and bacterial production was calculated from rates of [3H-methyl]thymidine incorporation by natural samples. Both vertical and seasonal distributions of bacterial production in the more productive lake (Little Crooked Lake) were strongly influenced by primary production. A lag of about 2 weeks between a burst in primary production and the subsequent response in bacterial production was observed. The vertical distribution of bacterial production in the water column of the less productive lake (Crooked Lake) was determined by the vertical distribution of primary production, but no clear relationship between seasonal maxima of primary and bacterial production in this lake was observed. High rates of bacterial production in Crooked Lake during May indicate the importance of allochthonous carbon washed in by spring rains. Bacterial production accounted for 30.6 and 31.8% of total (primary plus bacterial) production in Crooked Lake and Little Crooked Lake, respectively, from April through October. High rates of bacterial production during late September and October were observed in both lakes. Calculation of the fraction of bacterial production supported by phytoplankton excretion implies an important role for other mechanisms of supplying carbon, such as phytoplankton autolysis. Several factors affecting the calculation of bacterial production from the thymidine incorporation rates in these lakes were examined. PMID:16346742

  4. Lake Constance

    Atmospheric Science Data Center

    2013-04-17

    ... Swiss shores of Lake Constance at the town of Rorschach. Eutrophication, or the process of nutrient enrichment, is rapidly accelerated ... of the value of Lake Constance, efforts to mitigate eutrophication were initiated in the 1970's. MISR was built and is managed ...

  5. Primary production in a tropical large lake: the role of phytoplankton composition.

    PubMed

    Darchambeau, F; Sarmento, H; Descy, J-P

    2014-03-01

    Phytoplankton biomass and primary production in tropical large lakes vary at different time scales, from seasons to centuries. We provide a dataset made of 7 consecutive years of phytoplankton biomass and production in Lake Kivu (Eastern Africa). From 2002 to 2008, bi-weekly samplings were performed in a pelagic site in order to quantify phytoplankton composition and biomass, using marker pigments determined by HPLC. Primary production rates were estimated by 96 in situ (14)C incubations. A principal component analysis showed that the main environmental gradient was linked to a seasonal variation of the phytoplankton assemblage, with a clear separation between diatoms during the dry season and cyanobacteria during the rainy season. A rather wide range of the maximum specific photosynthetic rate (PBm) was found, ranging between 1.15 and 7.21 g carbong(-1)chlorophyll ah(-1), and was best predicted by a regression model using phytoplankton composition as an explanatory variable. The irradiance at the onset of light saturation (Ik) ranged between 91 and 752 μE m(-2)s(-1) and was linearly correlated with the mean irradiance in the mixed layer. The inter-annual variability of phytoplankton biomass and production was high, ranging from 53 to 100 mg chlorophyll am(-2) (annual mean) and from 143 to 278 g carbon m(-2)y(-1), respectively. The degree of seasonal mixing determined annual production, demonstrating the sensitivity of tropical lakes to climate variability. A review of primary production of other African great lakes allows situating Lake Kivu productivity in the same range as that of lakes Tanganyika and Malawi, even if mean phytoplankton biomass was higher in Lake Kivu.

  6. Adaptive divergence between lake and stream populations of an East African cichlid fish.

    PubMed

    Theis, Anya; Ronco, Fabrizia; Indermaur, Adrian; Salzburger, Walter; Egger, Bernd

    2014-11-01

    Divergent natural selection acting in different habitats may build up barriers to gene flow and initiate speciation. This speciation continuum can range from weak or no divergence to strong genetic differentiation between populations. Here, we focus on the early phases of adaptive divergence in the East African cichlid fish Astatotilapia burtoni, which occurs in both Lake Tanganyika (LT) and inflowing rivers. We first assessed the population structure and morphological differences in A. burtoni from southern LT. We then focused on four lake-stream systems and quantified body shape, ecologically relevant traits (gill raker and lower pharyngeal jaw) as well as stomach contents. Our study revealed the presence of several divergent lake-stream populations that rest at different stages of the speciation continuum, but show the same morphological and ecological trajectories along the lake-stream gradient. Lake fish have higher bodies, a more superior mouth position, longer gill rakers and more slender pharyngeal jaws, and they show a plant/algae and zooplankton-biased diet, whereas stream fish feed more on snails, insects and plant seeds. A test for reproductive isolation between closely related lake and stream populations did not detect population-assortative mating. Analyses of F1 offspring reared under common garden conditions indicate that the detected differences in body shape and gill raker length do not constitute pure plastic responses to different environmental conditions, but also have a genetic basis. Taken together, the A. burtoni lake-stream system constitutes a new model to study the factors that enhance and constrain progress towards speciation in cichlid fishes. © 2014 John Wiley & Sons Ltd.

  7. Lake Powell

    NASA Image and Video Library

    2007-09-20

    The white ring around Lake Powell tells the story. The surface is down 98 feet. This is critical, because Powell, Lake Mead, and other lakes along the Colorado River provide water for millions of people in five states. We are in the eighth year of a drought on the Colorado River. This year was the driest year ever reported in Southern California, and there is a severe drought in Northern California, down to less than 30-percent of snow pack. This ASTER image of part of Lake Powell was acquired in 2001. The gray area depicts the shrunken, reduced 2007 lake extent compared to the extended, larger black area in 2001. The image covers an area of 24 x 30 km, and is centered near 37.1 degrees north latitude, 111.3 degrees west longitude. This image from NASA Terra satellite. http://photojournal.jpl.nasa.gov/catalog/PIA10614

  8. Orbital- versus glacial-mode forcing of tropical African climate: Results of scientific drilling in Lake Malawi, East Africa

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.; Cohen, A. S.; Johnson, T. C.; King, J. W.; Brown, E. T.; Lyons, R. P.; Stone, J. R.; Beuning, K. R.

    2007-12-01

    Lake Malawi extends from 9-14 degrees S within the East African Rift Valley, and at 700 m deep, contains more than 20 percent of the surface water on the African continent. In 2005 the Lake Malawi Scientific Drilling Project drilled 7 holes at two sites in the lake, recovering a continuous sediment record that samples much of the Quaternary. Detailed studies completed to date on sediments deposited during the past 145 ka indicate periods of severe aridity at precessional frequency between 135 and 75 ka, when the lake's water volume was periodically reduced by at least 95 percent. These dramatic drops in lake level (more than 550 m), signifying markedly arid conditions in the catchment, are documented in sediment lithology (decreased organic carbon content and increased authigenic carbonate content during severe lowstands), aquatic microfossils (appearance of a littoral ostracode fauna, and saline/alkaline lake diatom flora during extreme low lake stages), as well as in dramatic reductions in catchment pollen production. These intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum, and are consistent with sediment records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa). In all three lakes a major rise in water levels and a shift to more humid conditions is observed after ~70 ka. The transition to wetter, more stable conditions coincides with the relaxation of orbital eccentricity and a reduction in the amplitude of precession. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but these new drill cores provide evidence for dramatically drier conditions prior to 70 ka that have not as yet been detected in marine sediment records. Such climate change may have stimulated the expansion and migrations of early modern human populations.

  9. Integrated perspectives on geological and biological dynamics in ancient Lake Ohrid

    NASA Astrophysics Data System (ADS)

    Wagner, B.; Wilke, T.; Francke, A.; Leicher, N.; Krastel, S.; Zanchetta, G.; Sulpizio, R.; Sadori, L.; Just, J.; Levkov, Z.; Wonik, T.; Vogel, H.; Wagner-Cremer, F.

    2015-12-01

    Lake Ohrid on the Balkan Peninsula is, along with lakes Baikal and Elgygytgyn in Russia and Lake Bosumtwi in Ghana, one of the very few lakes in the world that provides a continuous and high resolution record of environmental change of >1 Ma. With >300 endemic taxa, Lake Ohrid has the fourth highest degree of endemism in the world, being exceeded only by lakes Baikal, Tanganyika and Malawi. The combination of its long existence and high endemism makes Lake Ohrid a unique target to study the drivers of speciation and endemism. For this purpose, a 569 m long sediment sequence was recovered from the central part of the lake in spring 2013 within the scope of the International Continental Scientific Drilling Program (ICDP) and the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. Here, we present the results to date of analysis of the upper 248 m of this sequence, which covers the last ca. 640 ka according to an age model based on tephrostratigraphy as well as tuning of in situ physical and biogeochemical proxy data to orbital parameters and to the global benthic isotope stack. The sedimentological, physical, and geochemical data from the sediment sequence indicate changes in primary productivity, water column stratification, and water depth of the lake, and in weathering and erosion processes in the catchment. These changes can be clearly correlated with the intensity of glacial and interglacial periods as well as stadials and interstadials. However, paleontological and molecular clock analyses indicate that these changes and also the tephra deposition from eruptions of Italian volcanoes apparently did not lead to significant extinction events in the endemic species community. The lack of such catastrophic extinction events is probably due to the buffering capacity of the deep lake, possibly enhanced by the continuous existence of subaquatic karst springs with relatively stable habitats in the surroundings. This would enable the

  10. Characterization of Lake Michigan coastal lakes using zooplankton assemblages

    USGS Publications Warehouse

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

    2004-01-01

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

  11. Great Lakes

    NASA Image and Video Library

    2017-09-28

    Bands of lake effect snow drift eastward from the western Great Lakes in this true-color image captured by the NOAA/NASA Suomi NPP satellite's Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on January 5, 2017. National Weather Service forecasters expect light to moderate lake effect snow showers to continue throughout the day today and into Saturday (1/7). Lake-effect snow forms when cold air passes over the warmer waters of a lake. This causes some lake water to evaporate into the air and warm it. This warmer, wetter air rises and cools as it moves away from the lake. When it cools, it releases that moisture and, if it’s cold enough, that moisture turns into snow. Although true-color images like this may appear to be photographs of Earth, they aren't. They are created by combining data from the three color channels on the VIIRS instrument sensitive to the red, green and blue (or RGB) wavelengths of light into one composite image. In addition, data from several other channels are often also included to cancel out or correct atmospheric interference that may blur parts of the image. Credit: NOAA/NASA/Suomi NPP via NOAA's Environmental Visualization Laboratory

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

    PubMed

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

    2005-04-12

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

  13. Lake morphometry and wind exposure may shape the plankton community structure in acidic mining lakes.

    PubMed

    Weithoff, Guntram; Moser, Michael; Kamjunke, Norbert; Gaedke, Ursula; Weisse, Thomas

    2010-05-01

    Acidic mining lakes (pH <3) are specific habitats exhibiting particular chemical and biological characteristics. The species richness is low and mixotrophy and omnivory are common features of the plankton food web in such lakes. The plankton community structure of mining lakes of different morphometry and mixing type but similar chemical characteristics (Lake 130, Germany and Lake Langau, Austria) was investigated. The focus was laid on the species composition, the trophic relationship between the phago-mixotrophic flagellate Ochromonas sp. and bacteria and the formation of a deep chlorophyll maximum along a vertical pH-gradient. The shallow wind-exposed Lake 130 exhibited a higher species richness than Lake Langau. This increase in species richness was made up mainly by mero-planktic species, suggesting a strong benthic/littoral - pelagic coupling. Based on the field data from both lakes, a nonlinear, negative relation between bacteria and Ochromonas biomass was found, suggesting that at an Ochromonas biomass below 50 μg C L(-1), the grazing pressure on bacteria is low and with increasing Ochromonas biomass bacteria decline. Furthermore, in Lake Langau, a prominent deep chlorophyll maximum was found with chlorophyll concentrations ca. 50 times higher than in the epilimnion which was build up by the euglenophyte Lepocinclis sp. We conclude that lake morphometry, and specific abiotic characteristics such as mixing behaviour influence the community structure in these mining lakes.

  14. Lake morphometry and wind exposure may shape the plankton community structure in acidic mining lakes

    PubMed Central

    Weithoff, Guntram; Moser, Michael; Kamjunke, Norbert; Gaedke, Ursula; Weisse, Thomas

    2011-01-01

    Acidic mining lakes (pH <3) are specific habitats exhibiting particular chemical and biological characteristics. The species richness is low and mixotrophy and omnivory are common features of the plankton food web in such lakes. The plankton community structure of mining lakes of different morphometry and mixing type but similar chemical characteristics (Lake 130, Germany and Lake Langau, Austria) was investigated. The focus was laid on the species composition, the trophic relationship between the phago-mixotrophic flagellate Ochromonas sp. and bacteria and the formation of a deep chlorophyll maximum along a vertical pH-gradient. The shallow wind-exposed Lake 130 exhibited a higher species richness than Lake Langau. This increase in species richness was made up mainly by mero-planktic species, suggesting a strong benthic/littoral – pelagic coupling. Based on the field data from both lakes, a nonlinear, negative relation between bacteria and Ochromonas biomass was found, suggesting that at an Ochromonas biomass below 50 μg C L−1, the grazing pressure on bacteria is low and with increasing Ochromonas biomass bacteria decline. Furthermore, in Lake Langau, a prominent deep chlorophyll maximum was found with chlorophyll concentrations ca. 50 times higher than in the epilimnion which was build up by the euglenophyte Lepocinclis sp. We conclude that lake morphometry, and specific abiotic characteristics such as mixing behaviour influence the community structure in these mining lakes. PMID:23225914

  15. Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

    USGS Publications Warehouse

    Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

    2015-01-01

    inorganic sediment from less dense OM and allows terrestrial OM to preferentially be transported farther offshore. The conclusion is that for the organic carbon content in these regions to be elevated a mixed terrestrial-lacustrine origin is required. The hydrodynamic separation of mineral and organic constituents is most pronounced in regions with shallow bathymetric gradients, consistent with previous findings from Lake Tanganyika.

  16. Hydrogeochemical features of Lake Ngozi (SW Tanzania)

    NASA Astrophysics Data System (ADS)

    Delalande-Le Mouëllic, Manuëlla; Gherardi, Fabrizio; Williamson, David; Kajula, Stephen; Kraml, Michael; Noret, Aurélie; Abdallah, Issah; Mwandapile, Ezekiel; Massault, Marc; Majule, Amos; Bergonzini, Laurent

    2015-03-01

    Located on the triple rift junction hosting the Karonga-Usungu depression in Tanzania, Lake Ngozi is the second largest crater lake of the East African Rift. The lake has a number of peculiar features: it has a near constant water level, no permanent surface inlets and outlets, it is vertically well-mixed, with homogeneous distribution of temperature and chemical composition, and it is characterised by near neutral to slightly acid Na-Cl waters of comparatively high salinity and high P-CO2. Based on the different chemical signature of surface and ground waters (low-Cl type) from lake waters, mass balance methods have been applied to investigate lake dynamics. Water enters the lake mainly by precipitation and groundwater inflow, and leaves by groundwater outflow and evaporation. A large groundwater outflow of 2.4 m yr-1 has been estimated. The high salinity, Na-Cl signature of Lake Ngozi waters, together with 3He/4He ratios measured on dissolved gases (between 7 and 8.3 Ra) and high-PCO2 values estimated all along the water vertical column indicate the inflow of deep-seated fluids, likely magmatic in origin, into the lake. The existence of a hydrothermal system possibly at 250 °C in the root of the volcanic edifice is also hypothesised on the basis of solute geothermometry. Despite the current lack of vertical stratification, the lake is suspected to act as condenser for CO2 and other gases of deep magmatic origin, and should be then further monitored for the risk of limnic eruptions as well as for environmental and climatic concerns.

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

    NASA Astrophysics Data System (ADS)

    Martens, K.

    2009-04-01

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

  18. White Lake AOC

    EPA Pesticide Factsheets

    White Lake is in Muskegon County along the eastern shore of Lake Michigan. It was named an Area of Concern on the Great Lakes under the Great Lakes Water Quality Agreement of 1987 and delisted in 2014.

  19. Construction of chromosome markers from the Lake Victoria cichlid Paralabidochromis chilotes and their application to comparative mapping.

    PubMed

    Kuroiwa, A; Terai, Y; Kobayashi, N; Yoshida, K; Suzuki, M; Nakanishi, A; Matsuda, Y; Watanabe, M; Okada, N

    2014-01-01

    Cichlid fishes in the African Great Lakes are known as a spectacular example of adaptive radiation in vertebrates. Four linkage maps have been constructed to identify the genes responsible for adaptation and speciation, and the genetic linkages of those genes are assumed to play an important role during adaptive evolution. However, it is difficult to analyze such linkages because the linkage groups of one species do not match well with those of the other species. Chromosome markers are a powerful tool for the direct identification of linkage homology between different species. We used information about the linkage map of the Lake Malawi cichlid (Labeotropheus fuelleborni/Metriaclima zebra) to isolate bacterial artificial chromosome (BAC) clones from the BAC library of Paralabidochromis chilotes, Lake Victoria. We identified 18 of 22 P. chilotes chromosomes by single- and multi-color BAC fluorescence in situ hybridization using 19 BAC clones. Comparative mapping with the chromosome markers of P. chilotes in Astatotilapia burtoni (2n = 40) from Lake Tanganyika revealed the chromosome rearrangements that have occurred in this lineage. These chromosome markers will be useful for delineating the process of genome and chromosome evolution in African species. © 2013 S. Karger AG, Basel.

  20. Principles of lake sedimentology

    SciTech Connect

    Janasson, L.

    1983-01-01

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

  1. The morphometry of Lake Palmas, a deep natural lake in Brazil.

    PubMed

    Barroso, Gilberto F; Gonçalves, Monica A; Garcia, Fábio da C

    2014-01-01

    Lake Palmas (A = 10.3km2) is located in the Lower Doce River Valley (LDRV), on the southeastern coast of Brazil. The Lake District of the LDRV includes 90 lakes, whose basic geomorphology is associated with the alluvial valleys of the Barreiras Formation (Cenozoic, Neogene) and with the Holocene coastal plain. This study aimed to investigate the relationship of morphometry and thermal pattern of a LDRV deep lake, Lake Palmas. A bathymetric survey carried out in 2011 and the analysis of hydrographic and wind data with a geographic information system allowed the calculation of several metrics of lake morphometry. The vertical profiling of physical and chemical variables in the water column during the wet/warm and dry/mild cold seasons of 2011 to 2013 has furnished a better understanding of the influence of the lake morphometry on its structure and function. The overdeepened basin has a subrectangular elongated shape and is aligned in a NW-SE direction in an alluvial valley with a maximum depth (Zmax) of 50.7 m, a volume of 2.2×10(8) m3 (0.22 km3) and a mean depth (Zmv) of 21.4m. These metrics suggest Lake Palmas as the deepest natural lake in Brazil. Water column profiling has indicated strong physical and chemical stratification during the wet/warm season, with a hypoxic/anoxic layer occupying one-half of the lake volume. The warm monomictic pattern of Lake Palmas, which is in an accordance to deep tropical lakes, is determined by water column mixing during the dry and mild cold season, especially under the influence of a high effective fetch associated with the incidence of cold fronts. Lake Palmas has a very long theoretical retention time, with a mean of 19.4 years. The changes observed in the hydrological flows of the tributary rivers may disturb the ecological resilience of Lake Palmas.

  2. The Morphometry of Lake Palmas, a Deep Natural Lake in Brazil

    PubMed Central

    Barroso, Gilberto F.; Gonçalves, Monica A.; Garcia, Fábio da C.

    2014-01-01

    Lake Palmas (A = 10.3km2) is located in the Lower Doce River Valley (LDRV), on the southeastern coast of Brazil. The Lake District of the LDRV includes 90 lakes, whose basic geomorphology is associated with the alluvial valleys of the Barreiras Formation (Cenozoic, Neogene) and with the Holocene coastal plain. This study aimed to investigate the relationship of morphometry and thermal pattern of a LDRV deep lake, Lake Palmas. A bathymetric survey carried out in 2011 and the analysis of hydrographic and wind data with a geographic information system allowed the calculation of several metrics of lake morphometry. The vertical profiling of physical and chemical variables in the water column during the wet/warm and dry/mild cold seasons of 2011 to 2013 has furnished a better understanding of the influence of the lake morphometry on its structure and function. The overdeepened basin has a subrectangular elongated shape and is aligned in a NW-SE direction in an alluvial valley with a maximum depth (Zmax) of 50.7m, a volume of 2.2×108 m3 (0.22km3) and a mean depth (Zmv) of 21.4m. These metrics suggest Lake Palmas as the deepest natural lake in Brazil. Water column profiling has indicated strong physical and chemical stratification during the wet/warm season, with a hypoxic/anoxic layer occupying one-half of the lake volume. The warm monomictic pattern of Lake Palmas, which is in an accordance to deep tropical lakes, is determined by water column mixing during the dry and mild cold season, especially under the influence of a high effective fetch associated with the incidence of cold fronts. Lake Palmas has a very long theoretical retention time, with a mean of 19.4 years. The changes observed in the hydrological flows of the tributary rivers may disturb the ecological resilience of Lake Palmas. PMID:25406062

  3. Functional convergence among pelagic sculpins of Lake Baikal and deepwater ciscoes of the Great Lakes

    USGS Publications Warehouse

    Eshenroder, Randy L.; Sideleva, Valentina G.; Todd, Thomas N.

    1999-01-01

    The vast, well-oxygenated hypolimnia of Lake Baikal and the Great Lakes were both dominated by endemic planktivorous fishes. These dominants, two species of sculpins (Comephorus, Comephoridae) in Lake Baikal and six species of deepwater ciscoes (Coregonus, Salmonidae) in the Great Lakes, although distant taxonomically, have morphologies suggesting a surprising degree of functional convergence. Here it is proposed that the same two buoyancy-regulation strategies observed in Baikal sculpins also arose in the deepwater ciscoes of the Great Lakes. One strategy favors hydrostatic lift (generated by low specific gravity) and is characterized by fatter, larger-bodied fish with smaller paired fins; the second strategy favors hydrodynamic lift (generated by swimming) and is characterized by leaner, smaller-bodied fish with larger paired fins. Both types likely evolved to feed on a single species of ecologically analogous, vertically migrating macrozooplankter: Macrohectopus branickii in Lake Baikal and Mysis relicta in the Great Lakes. It is suggested that Coregonus did not diversify and proliferate in Lake Baikal as they did in the Great Lakes because by the time Coregonus colonized Lake Baikal, pelagic sculpins were already dominant.

  4. Thermal, Chemical and Physical Investigations into Lake Deepening Processes on Spillway Lake, Ngozumpa Glacier, Nepal

    NASA Astrophysics Data System (ADS)

    Horodyskyj, U. N.

    2014-12-01

    The Ngozumpa glacier is one of Nepal's largest and longest glaciers, fed by catchments on the slopes of Cho Oyu, the 6th highest peak in the world. Supraglacial lakes abound along its ~18-km-long ablation zone, but these are dwarfed in area and volume by Spillway lake, a terminal supraglacial lake that is currently expanding and deepening in the lowest kilometer of the glacier. This lake poses a potential future downstream flooding threat, hence there is a perceived need for continuous monitoring and for quantifying factors that lead to growth, deepening and potential instability. Point-interpolated depth surveys (2010/2012) by Thompson and others have revealed deepening hotspots in multiple locations within the lake. The current study reports University of Colorado surveys in 2013 and 2014 that quantify a) vertical water temperature variations in areas of deepening and shallowing; b) physical and chemical characteristics of dredged sediment samples from the lake floor; c) lake water chemistry; d) lake floor bathymetry imaged using high-resolution side-scan sonar and e) lake bottom hardness and roughness. These parameters are analyzed with a view to assessing their role in controlling lake floor deepening and growth.

  5. Water-quality and lake-stage data for Wisconsin lakes, water year 2005

    USGS Publications Warehouse

    Rose, W.J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, D.M.

    2006-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. The purpose of this report is to provide information about the chemical and physical charac-teristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measure-ments of in-lake water quality and lake stage. Time series graphs of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive infor-mation for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks.

  6. Influence of wind and lake morphometry on the interaction between two rivers entering a stratified lake

    USGS Publications Warehouse

    Morillo, S.; Imberger, J.; Antenucci, J.P.; Woods, P.F.

    2008-01-01

    The interaction of two rivers flowing into Coeur d'Alene Lake (United States) was investigated with a field experiment and three-dimensional numerical simulations. The focus was on the influence of basin morphology, wind speed, and wind direction on the fate and transport of the inflowing water. Data from the field campaign showed that intrusions from the two rivers propagated into the lake at different depths, with the trace element polluted Coeur d'Alene River flowing into the lake above the trace element poor and nutrient rich St. Joe River inflow. The inflows initially intruded horizontally into the lake at their level of neutral buoyancy and later mixed vertically. Model results revealed that, as the intrusions entered the main lake basin, a forced horizontal mode-two basin-scale internal wave interacted with the intrusions to frequently siphon them into the lake proper and where rapid vertical mixing followed. The results serve to show how detailed transport and mixing patterns in a lake can have important consequences for the plankton ecology in the lake. ?? 2008 ASCE.

  7. Lake Powell

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The white ring around Lake Powell tells the story. The surface is down 98 feet. This is critical, because Powell, Lake Mead, and other lakes along the Colorado River provide water for millions of people in five states. We are in the eighth year of a drought on the Colorado River. This year was the driest year ever reported in Southern California, and there is a severe drought in Northern California, down to less than 30-percent of snow pack. This ASTER image of part of Lake Powell was acquired in 2001. The gray area depicts the shrunken, reduced 2007 lake extent compared to the extended, larger black area in 2001.

    The image covers an area of 24 x 30 km, and is centered near 37.1 degrees north latitude, 111.3 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  8. Large-scale variability of wind erosion mass flux rates at Owens Lake 1. Vertical profiles of horizontal mass fluxes of wind-eroded particles with diameter greater than 50 μm

    USGS Publications Warehouse

    Gillette, Dale A.; Fryrear, D.W.; Xiao, Jing Bing; Stockton, Paul; Ono, Duane; Helm, Paula J.; Gill, Thomas E; Ley, Trevor

    1997-01-01

    A field experiment at Owens (dry) Lake, California, tested whether and how the relative profiles of airborne horizontal mass fluxes for >50-μm wind-eroded particles changed with friction velocity. The horizontal mass flux at almost all measured heights increased proportionally to the cube of friction velocity above an apparent threshold friction velocity for all sediment tested and increased with height except at one coarse-sand site where the relative horizontal mass flux profile did not change with friction velocity. Size distributions for long-time-averaged horizontal mass flux samples showed a saltation layer from the surface to a height between 30 and 50 cm, above which suspended particles dominate. Measurements from a large dust source area on a line parallel to the wind showed that even though the saltation flux reached equilibrium ∼650 m downwind of the starting point of erosion, weakly suspended particles were still input into the atmosphere 1567 m downwind of the starting point; thus the saltating fraction of the total mass flux decreased after 650 m. The scale length difference and ratio of 70/30 suspended mass flux to saltation mass flux at the farthest down wind sampling site confirm that suspended particles are very important for mass budgets in large source areas and that saltation mass flux can be a variable fraction of total horizontal mass flux for soils with a substantial fraction of <100-μm particles.

  9. Recent warming of lake Kivu.

    PubMed

    Katsev, Sergei; Aaberg, Arthur A; Crowe, Sean A; Hecky, Robert E

    2014-01-01

    Lake Kivu in East Africa has gained notoriety for its prodigious amounts of dissolved methane and dangers of limnic eruption. Being meromictic, it is also expected to accumulate heat due to rising regional air temperatures. To investigate the warming trend and distinguish between atmospheric and geothermal heating sources, we compiled historical temperature data, performed measurements with logging instruments, and simulated heat propagation. We also performed isotopic analyses of water from the lake's main basin and isolated Kabuno Bay. The results reveal that the lake surface is warming at the rate of 0.12°C per decade, which matches the warming rates in other East African lakes. Temperatures increase throughout the entire water column. Though warming is strongest near the surface, warming rates in the deep waters cannot be accounted for solely by propagation of atmospheric heat at presently assumed rates of vertical mixing. Unless the transport rates are significantly higher than presently believed, this indicates significant contributions from subterranean heat sources. Temperature time series in the deep monimolimnion suggest evidence of convection. The progressive deepening of the depth of temperature minimum in the water column is expected to accelerate the warming in deeper waters. The warming trend, however, is unlikely to strongly affect the physical stability of the lake, which depends primarily on salinity gradient.

  10. Recent Warming of Lake Kivu

    PubMed Central

    Katsev, Sergei; Aaberg, Arthur A.; Crowe, Sean A.; Hecky, Robert E.

    2014-01-01

    Lake Kivu in East Africa has gained notoriety for its prodigious amounts of dissolved methane and dangers of limnic eruption. Being meromictic, it is also expected to accumulate heat due to rising regional air temperatures. To investigate the warming trend and distinguish between atmospheric and geothermal heating sources, we compiled historical temperature data, performed measurements with logging instruments, and simulated heat propagation. We also performed isotopic analyses of water from the lake's main basin and isolated Kabuno Bay. The results reveal that the lake surface is warming at the rate of 0.12°C per decade, which matches the warming rates in other East African lakes. Temperatures increase throughout the entire water column. Though warming is strongest near the surface, warming rates in the deep waters cannot be accounted for solely by propagation of atmospheric heat at presently assumed rates of vertical mixing. Unless the transport rates are significantly higher than presently believed, this indicates significant contributions from subterranean heat sources. Temperature time series in the deep monimolimnion suggest evidence of convection. The progressive deepening of the depth of temperature minimum in the water column is expected to accelerate the warming in deeper waters. The warming trend, however, is unlikely to strongly affect the physical stability of the lake, which depends primarily on salinity gradient. PMID:25295730

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

    PubMed Central

    Crossland, N. O.

    1963-01-01

    The author describes a large-scale experiment in which the molluscicide Bayer 73 (Bayluscide) was used in an attempt to eliminate Biomphalaria pfeifferi, the snail host of Schistosoma mansoni, from an irrigation system in Tanganyika. Applied at a concentration of 1 p.p.m., the molluscicide gave a very high kill of snails and much of the treated area remained completely free of vector snails for seven months after treatment. However, there were a few survivors in small pockets associated with a drainage area that became flooded during heavy rains coincident with the application of molluscicide. From these survivors a dramatic resurgence of snails occurred in some of the treated canals. This resurgence may be analogous to similar phenomena observed in some insecticide work. The suggestion is made that removal of parasites and predators, in particular trematode parasites, by a molluscicide might increase the snail's capacity for repopulation. Studies of the seasonal fluctuations of snail population density in an adjacent, but separate, irrigation system suggest that molluscicide applications would be more effective if timed to coincide with the end of the rainy seasons. ImagesFIG. 2 PMID:14103411

  12. Limnological investigation of six lakes in southeast Alaska

    USGS Publications Warehouse

    McCoy, George A.; Wiggins, William W.; Schmidt, Artwin E.

    1976-01-01

    Limnological data were collected from six lakes in southeast Alaska in 1974. The data include concentrations of major inorganic constituents, nutrients, selected trace metals, total organic carbon, and chlorophyll. Vertical profiles of specific conductance, temperature, dissolved-oxygen saturation, and pH were drawn. With the exception of Redoubt Lake, all of the lakes are very similar chemically. The small differences in chemical composition probably reflect variations in geology of the drainage basins, altitudes, and morphometric characteristics of the lakes. Productivity is so low in all the lakes that it was not possible to rank the lakes by relative productivity from the reconnaissance sampling. Redoubt Lake is meromictic, but the others are probably holomictic and dimictic. (Woodard-USGS)

  13. Reconstructing paleo lake levels from relict shorelines along the Upper Great Lakes

    USGS Publications Warehouse

    Baedke, Steve J.; Thompson, Todd A.; Johnston, John W.; Wilcox, Douglas A.

    2004-01-01

    Shorelines of the upper Great Lakes include many embayments that contain strandplains of beach ridges. These former shoreline positions of the lakes can be used to determine changes in the elevation of the lakes through time, and they also provide information on the warping of the ground surface that is occurring in the Great Lakes after the weight of glacial ice was removed. Relative lake-level hydrographs can be created by coring the beach ridges to determine the elevation of basal foreshore (swash zone) deposits in each ridge and by obtaining radiocarbon dates of basal wetland sediments between ridges to generate an age model for the ridges. Because the relative-level hydrographs are the combination of lake-level change and vertical ground movement (isostatic rebound), the rebound must be removed to produce a graph that shows only the physical limits and timing of past lake-level fluctuations referenced to a common outlet. More than 500 vibracores of beach-ridge sediments were collected at five sites along Lake Michigan and four sites along Lake Superior. The cores showed a sequence of dune deposits overlying foreshore deposits that, in turn, overlie upper shoreface deposits. The base of the foreshore deposits is coarser and more poorly sorted than an overlying and underlying sediment and represents the plunge-point sediments at the base of the swash zone. The plunge-point deposits are a close approximation of the elevation of the lake when the beach ridge formed. More than 150 radiocarbon ages of basal wetland sediments were collected to produce age models for the sites. Currently, age models exist for all Lake Michigan sites and one Lake Superior site. By combining the elevation data with the age models, six relative lake-level hydrographs were created for the upper Great Lakes. An iterative approach was used to remove rebound from the five Lake Michigan relative hydrographs and merge the graphs into a single hydrograph. The resultant hydrograph shows long

  14. Vertical bounce of two vertically aligned balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2007-11-01

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

  15. Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 2007

    USGS Publications Warehouse

    Wisconsin Water Science Center Lake-Studies Team: Rose, W. J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, Dale M.

    2008-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2007 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 2005 through September 30, 2007 is called 'water year 2007.' The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake?s watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: 'Water Resources Data-Wisconsin, 2007.'

  16. OMS Pods and Vertical Stabilizer on Space Shuttle Atlantis during STS-132

    NASA Image and Video Library

    2010-05-25

    S132-E-011670 (25 May 2010) --- Backdropped over parts of Michigan and the Canadian province of Ontario, space shuttle Atlantis? vertical stabilizer, orbital maneuvering system (OMS) pods and aft payload bay are featured in this image photographed by an STS-132 on the shuttle during flight day 12 activities. Recognizable features in the photo include Lake St. Clair and parts of Lake Huron and Lake Erie.

  17. Great Lakes

    USGS Publications Warehouse

    Edsall, Thomas A.; Mac, Michael J.; Opler, Paul A.; Puckett Haecker, Catherine E.; Doran, Peter D.

    1998-01-01

    The Great Lakes region, as defined here, includes the Great Lakes and their drainage basins in Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, and New York. The region also includes the portions of Minnesota, Wisconsin, and the 21 northernmost counties of Illinois that lie in the Mississippi River drainage basin, outside the floodplain of the river. The region spans about 9º of latitude and 20º of longitude and lies roughly halfway between the equator and the North Pole in a lowland corridor that extends from the Gulf of Mexico to the Arctic Ocean.The Great Lakes are the most prominent natural feature of the region (Fig. 1). They have a combined surface area of about 245,000 square kilometers and are among the largest, deepest lakes in the world. They are the largest single aggregation of fresh water on the planet (excluding the polar ice caps) and are the only glacial feature on Earth visible from the surface of the moon (The Nature Conservancy 1994a).The Great Lakes moderate the region’s climate, which presently ranges from subarctic in the north to humid continental warm in the south (Fig. 2), reflecting the movement of major weather masses from the north and south (U.S. Department of the Interior 1970; Eichenlaub 1979). The lakes act as heat sinks in summer and heat sources in winter and are major reservoirs that help humidify much of the region. They also create local precipitation belts in areas where air masses are pushed across the lakes by prevailing winds, pick up moisture from the lake surface, and then drop that moisture over land on the other side of the lake. The mean annual frost-free period—a general measure of the growing-season length for plants and some cold-blooded animals—varies from 60 days at higher elevations in the north to 160 days in lakeshore areas in the south. The climate influences the general distribution of wild plants and animals in the region and also influences the activities and distribution of the human

  18. Comparison of the hydrogeology and water quality of a ground-water augmented lake with two non-augmented lakes in northwest Hillsborough County, Florida

    USGS Publications Warehouse

    Metz, Patricia A.; Sacks, Laura A.

    2002-01-01

    The hydrologic effects associated with augmenting a lake with ground water from the Upper Floridan aquifer were examined in northwest Hillsborough County, Florida, from June 1996 through May 1999. The hydrogeology, ground-water flow patterns, water budgets, and water-quality characteristics were compared between a lake that has been augmented for more than 30 years (Round Lake) and two nearby nonaugmented lakes (Dosson Lake and Halfmoon Lake). Compared to the other study lakes, Round Lake is in a more leakage-dominated hydrogeologic setting. The intermediate confining unit is thin or highly breached, which increases the potential for vertical ground-water flow. Round Lake has the least amount of soft, organic lake-bottom sediments and the lake bottom has been dredged deeper and more extensively than the other study lakes, which could allow more leakage from the lake bottom. The area around Round Lake has experienced more sinkhole activity than the other study lakes. During this study, three sinkholes developed around the perimeter of the lake, which may have further disrupted the intermediate confining unit.Ground-water flow patterns around Round Lake were considerably different than the nonaugmented lakes. For most of the study, groundwater augmentation artificially raised the level of Round Lake to about 2 to 3 feet higher than the adjacent water table. As a result, lake water recharged the surficial aquifer around the entire lake perimeter, except during very wet periods when ground-water inflow occurred around part of the lake perimeter. The non-augmented lakes typically had areas of ground-water inflow and areas of lake leakage around their perimeter, and during wet periods, ground-water inflow occurred around the entire lake perimeter. Therefore, the area potentially contributing ground water to the non-augmented lakes is much larger than for augmented Round Lake. Vertical head loss within the surficial aquifer was greater at Round Lake than the other study

  19. Vertical axis wind turbines

    DOEpatents

    Krivcov, Vladimir [Miass, RU; Krivospitski, Vladimir [Miass, RU; Maksimov, Vasili [Miass, RU; Halstead, Richard [Rohnert Park, CA; Grahov, Jurij [Miass, RU

    2011-03-08

    A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

  20. LONG-TERM RECOVERY OF PCB-CONTAMINATED SEDIMENTS AT THE LAKE HARTWELL SUPERFUND SITE: PCB DECHLORINATION. 2. RATES AND EXTENT

    EPA Science Inventory

    This paper reports on extensive polychlorinated biphenyl (PCB) dechlorination measured in Lake Hartwell (Pickens County, SC) sediments. Vertical sediment cores were collected from 18 locations in Lake Hartwell (Pickens County, SC) and analyzed in 5-cm increments for PCB congeners...

  1. LONG-TERM RECOVERY OF PCB-CONTAMINATED SEDIMENTS AT THE LAKE HARTWELL SUPERFUND SITE: PCB DECHLORINATION. 2. RATES AND EXTENT

    EPA Science Inventory

    This paper reports on extensive polychlorinated biphenyl (PCB) dechlorination measured in Lake Hartwell (Pickens County, SC) sediments. Vertical sediment cores were collected from 18 locations in Lake Hartwell (Pickens County, SC) and analyzed in 5-cm increments for PCB congeners...

  2. Evaluation of water quality and management of Hongze Lake and Gaoyou Lake along the Grand Canal in Eastern China.

    PubMed

    Li, Shuheng; Guo, Wei; Mitchell, Bruce

    2011-05-01

    Hongze Lake and Gaoyou Lake are the source of water for the Grand Canal and the eastern route of the South-to-North Water Transfer (SNWT) project. With the accelerating pace of construction of the SNWT and the initiative to achieve "World Heritage " status for the canal, the water quality and management of the lakes have gained attention in China. Based on analysis of water samples, monitoring data, and the content of heavy metal elements in surface sediments, the water quality of Gaoyou Lake and Hongze Lake have been examined. According to the analysis of the water samples taken in 2003, the content of the heavy metals met the water demands for Hongze Lake and Gaoyou Lake. However, monitoring data of 2004 indicate that the water quality of Hongze Lake and Gaoyou Lake both were worse than grade III which cannot meet the required standard. The heavy metal elements of sediment samples also were above the acceptable environmental standard values. Some projects were launched to promote the lake environment by controlling wastewater emissions, standardizing the types of boats and introducing regulations to protect the lakes. However, problems of vertical and horizontal fragmentation and insufficient public participation in the current management system still exist in the area. Considering the problems confronting the lakes, Integrated Water Resource Management is discussed as an effective approach to overcome the problems.

  3. Lake Bonneville

    USGS Publications Warehouse

    Gilbert, Grove Karl

    1890-01-01

    This volume is a contribution to the later physical history of the Great Basin. As a geographic province the Great Basin is characterized by a dry climate, changes of drainage, volcanic eruption, and crustal displacement. Lake Bonneville, the special theme of the volume, was a phenomenon of climate and drainage, but its complete history includes an account of contemporaneous eruption and displacement.

  4. Water-quality and lake-stage data for Wisconsin lakes, water year 1998

    USGS Publications Warehouse

    Robertson, Dale M.; Elder, J.F.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Rose, W.J.

    1999-01-01

    The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are usually included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data- Wisconsin, 1998."

  5. 11. Detail of portion of west wall and vertical and ...

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

    11. Detail of portion of west wall and vertical and horizontal supports inside machine shop section of roundhouse. View to northwest. - Duluth & Iron Range Rail Road Company Shops, Roundhouse, Southwest of downtown Two Harbors, northwest of Agate Bay, Two Harbors, Lake County, MN

  6. Water quality of selected lakes in Mount Rainier National Park, Washington with respect to lake acidification

    USGS Publications Warehouse

    Turney, G.L.; Dion, N.P.; Sumioka, S.S.

    1986-01-01

    Thirteen lakes in Mount Rainier National Park were evaluated for general chemical characteristics, sensitivity to acidification by acidic precipitation, and degree of existing acidification. The lakes studies were Allen, one of the Chenuis group, Crescent , Crystal, Eleanor, Fan, one of the Golden group, Marsh, Mowich, Mystic, Shriner, and two unnamed lakes. The lakes were sampled in August 1983. Specific conductance values were generally 21 microsiemens/cm at 25 C or less, and dissolved solids concentrations were generally 20 mg/L or less. The major cations were calcium and sodium, and the major anion was bicarbonate. Alkalinity concentrations ranged from 2.1 to 9.0 mg/L in 12 of the lakes. Allen Lake was the exception, having an alkalinity concentration of 27 mg/L. The pH values for all of the lakes ranged from 5.8 to 6.5. In most of the lakes, vertical profiles of temperature, dissolved oxygen, pH, and specific conductance were relatively uniform. In the deeper lakes, temperature decreased with depth and dissolved-oxygen concentrations increased to about 20 feet, remained constant to 80 ft, then decreased with increasing depth. Exceptions to general water quality patterns were observed in three lakes. Allen Lake had a specific conductance value of 58 Microsiemens/cm. The lake of the Golden group was anaerobic at the bottom and had relatively high concentrations of dissolved organic carbon and dissolved metals, and a lower light transmission than the other lakes studied. One of the unnamed lakes had relatively high concentrations of phytoplankton and dissolved organic carbon and relatively low levels of light transmission. Comparisons of lake data to acid-sensitivity thresholds for specific conductance and alkalinity indicated that all of the lakes except Allen would be sensitive to acidic precipitation. The small sizes of the lakes, and their locations in basins of high precipitation and weathering-resistant rock types, enhance their sensitivity. None of the

  7. Water-quality and lake-stage data for Wisconsin lakes, water year 1997

    USGS Publications Warehouse

    Robertson, D.M.; Elder, J.F.; Garn, H.S.; Goodard, G.L.; Marsh, S.B.; Olson, D.L.; Rose, W.J.

    1998-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The location of water-quality and lake-stage stations in Wisconsin for water year 1997 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 1996 through September 30, 1997 is called 'water year 1997'. The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of lake stage and in-lake water quality. Graphs of Secchi depths, surface total-phosphorus and chlorophyll-a concentrations versus time are usually included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: 'Water Resources Data-Wisconsin, 1997'.

  8. Vertical Axis Wind Turbine

    SciTech Connect

    Homicz, Greg

    2002-04-01

    Blade fatigue life is an important element in determining the economic viability of the Vertical-Axis Wind Turbine (VAWT). VAWT-SAL Vertical Axis Wind Turbine- Stochastic Aerodynamic Loads Ver 3.2 numerically simulates the stochastic (random0 aerodynamic loads of the Vertical-Axis Wind Turbine (VAWT) created by the atomspheric turbulence. The program takes into account the rotor geometry, operating conditions, and assumed turbulence properties.

  9. Offset vertical radar profiling

    USGS Publications Warehouse

    Witten, A.; Lane, J.

    2003-01-01

    Diffraction tomography imaging was applied to VRP data acquired by vertically moving a receiving antenna in a number of wells. This procedure simulated a vertical downhole receiver array. Similarly, a transmitting antenna was sequentially moved along a series of radial lines extending outward from the receiver wells. This provided a sequence of multistatic data sets and, from each data set, a two-dimensional vertical cross-sectional image of spatial variations in wave speed was reconstructed.

  10. Generalized scaling of seasonal thermal stratification in lakes

    NASA Astrophysics Data System (ADS)

    Shatwell, T.; Kirillin, G.

    2016-12-01

    The mixing regime is fundamental to the biogeochemisty and ecology of lakes because it determines the vertical transport of matter such as gases, nutrients, and organic material. Whereas shallow lakes are usually polymictic and regularly mix to the bottom, deep lakes tend to stratify seasonally, separating surface water from deep sediments and deep water from the atmosphere. Although empirical relationships exist to predict the mixing regime, a physically based, quantitative criterion is lacking. Here we review our recent research on thermal stratification in lakes at the transition between polymictic and stratified regimes. Using the mechanistic balance between potential and kinetic energy in terms of the Richardson number, we derive a generalized physical scaling for seasonal stratification in a closed lake basin. The scaling parameter is the critical mean basin depth that delineates polymictic and seasonally stratified lakes based on lake water transparency (Secchi depth), lake length, and an annual mean estimate for the Monin-Obukhov length. We validated the scaling on available data of 374 global lakes using logistic regression and found it to perform better than other criteria including a conventional open basin scaling or a simple depth threshold. The scaling has potential applications in estimating large scale greenhouse gas fluxes from lakes because the required inputs, like water transparency and basin morphology, can be acquired using the latest remote sensing technologies. The generalized scaling is universal for freshwater lakes and allows the seasonal mixing regime to be estimated without numerically solving the heat transport equations.

  11. Lake on life support: Evaluating urban lake management measures by using a coupled 1D-modelling approach

    NASA Astrophysics Data System (ADS)

    Ladwig, Robert; Kirillin, Georgiy; Hinkelmann, Reinhard; Hupfer, Michael

    2017-04-01

    Urban surface water systems and especially lakes are heavily stressed and modified systems to comply with water management goals and expectations. In this study we focus on Lake Tegel in Berlin, Germany, as a representative of heavily modified urban lakes. In the 20th century, Lake Tegel received increased loadings of nutrients and leached heavy metals from an upstream sewage farm resulting in severe eutrophication problems. The construction of two upstream treatment plants caused a lowering of nutrient concentrations and a re-oligotrophication of the lake. Additionally, artificial aerators, to keep the hypolimnion oxic, and a lake pipeline, to bypass water for maintaining a minimum discharge, went into operation. Lake Tegel is still heavily used for drinking water extraction by bank filtration. These interacting management measures make the system vulnerable to changing climate conditions and pollutant loads. Past modelling studies have shown the complex hydrodynamics of the lake. Here, we are following a simplified approach by using a less computational time consuming vertical 1D-model to simulate the hydrodynamics and the ecological interactions of the system by coupling the General Lake Model to the Aquatic Ecodynamics Model Library 2. For calibration of the multidimensional parameter space we applied the Covariance Matrix Adaption-Evolution Strategy algorithm. The model is able to sufficiently replicate the vertical field temperature profiles of Lake Tegel as well as to simulate similar concentration ranges of phosphate, dissolved oxygen and nitrate. The calibrated model is used to run an uncertainty analysis by sampling the simulated data within the meaning of the Metropolis-Hastings algorithm. Finally, we are evaluating different scenarios: (1) changing air temperatures, precipitation and wind speed due to effects of climate change, (2) decreased discharges into the lake due to bypassing treated effluents into a near stream instead of Lake Tegel, and (3

  12. Lake Mackay, Australia

    NASA Image and Video Library

    2014-10-27

    This image from NASA Terra spacecraft shows Lake Mackay, the largest of hundreds of ephemeral lakes scattered throughout Western Australia and the Northern Territory, and is the second largest lake in Australia.

  13. Tides In The Subglacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Dietrich, R.; Shibuya, K.; Pötzsch, A.; Ozawa, T.

    Subglacial lakes belong to the most interesting glaciological features in Antarctica, where the 240-km-long Lake Vostok is the most prominent one. For the understanding of the dynamics of the Lake Vostok system different compo- nents such as ice thickness and ice motion, lake bathymetry, geothermal heat flow, water circulation and melting-refreezing have to be investigated and modelled in a complex way. An aspect, which has not been considered yet, are lake tides. We present evidence based on observations which indicate the existence of tides in the lake. Earlier gravimetric tidal observations at Vostok Station show a significant deviation from theoretical solid earth tides which may be explained as the tidal effect of the water underneath the station. Interferometric SAR analysis yields a specific sur- face deformation pattern which is interpreted as a tidal signal too. According to our estimation the resulting magnitude of the vertical surface deformation is in the order of a few centimetres. The role of a `tidal pump' concerning the water circulation in the lake will be empha- sized.

  14. Bathymetry of Bonnie Doone Lake, Kornbow Lake, Mintz Pond, and Glenville Lake, Cumberland County, North Carolina, 1996-98

    USGS Publications Warehouse

    Giorgino, M.J.; Strain, R.E.

    1999-01-01

    Bathymetric surveys were conducted at four water-supply impoundments of Little Cross Creek in Cumberland County, North Carolina. The surveys were conducted in April 1996 at Mintz Pond and Glenville Lake, and in January 1998 at Bonnie Doone Lake and Kornbow Lake. The resulting bathymetric maps are the first to cover the entire range in depth for these reservoirs and provide a framework for future evaluations of bathymetry and storage capacity. Bathymetric maps were constructed from depth and position data collected at each reservoir. A boat-mounted, research-grade fathometer was used to record water depths with a vertical accuracy of 0.1 foot. At Mintz Pond and Glenville Lake, position was measured by using a wide-band laser tracking system interfaced with a total station survey instrument. This positioning method required multiple land-based control points to be established and was hampered by line-of-sight restrictions between the control points and the boat. At Bonnie Doone Lake and Kornbow Lake, a global positioning system was used to collect differentially corrected location data. This positioning method enabled more rapid data collection, eliminated the need for land-based control points, and provided improved data coverage. Spillway elevations range from 172.8 feet above mean sea level at Bonnie Doone Lake to 113.1 feet at Glenville Lake. Surface area and storage volume were computed for each reservoir and were related to water-surface elevations at 1-foot intervals. The combined surface acreage of the four Little Cross Creek reservoirs at their full-pool elevations is 120.97 acres, consisting of 21.20 acres at Bonnie Doone Lake, 47.09 acres at Kornbow Lake, 15.56 acres at Mintz Pond, and 37.12 acres at Glenville Lake. The four reservoirs have a combined usable storage capacity of 674.91 acre-feet, which is the sum of 127.93 acre-feet in Bonnie Doone Lake, 320.62 acre-feet in Kornbow Lake, 53.25 acre-feet in Mintz Pond, and 173.11 acre-feet in Glenville Lake.

  15. Traumatic vertical atlantoaxial dislocation.

    PubMed

    Payer, M; Wetzel, S; Kelekis, A; Jenny, B

    2005-08-01

    We present a case of traumatic vertical atlantoaxial dislocation of 16 millimetres with a fatal outcome. We hypothesize that this extremely rare traumatic vertical atlantoaxial dislocation results from insufficiency of the C1/C2 facet capsules after rupture of the tectorial membrane and the alar ligaments.

  16. Vertical axis windmill

    SciTech Connect

    Campbell, J.S.

    1980-04-08

    A vertical axis windmill is described which involves a rotatable central vertical shaft having horizontal arms pivotally supporting three sails that are free to function in the wind like the main sail on a sail boat, and means for disabling the sails to allow the windmill to be stopped in a blowing wind.

  17. Circulation and Respiration in Ice-covered Alaskan Arctic Lakes

    NASA Astrophysics Data System (ADS)

    MacIntyre, S.; Cortés, A.

    2016-12-01

    Arctic lakes are ice-covered 9 months of the year. For some of this time, the sediments heat the overlying water, and respiration in the sediments increases specific conductivity, depletes oxygen, and produces greenhouse gases (GHG). Whether anoxia forms and whether the greenhouse gases are sequestered at depth depends on processes inducing circulation and upward fluxes. Similarly, whether the GHG are released at ice off depends on the extent of vertical mixing at that time. Using time series meteorological data and biogeochemical arrays with temperature, specific conductivity, and optical oxygen sensors in 5 lakes ranging from 1 to 150 ha, we illustrate the connections between meteorological forcing and within lake processes including gravity currents resulting from increased density just above the sediment water interface and internal waves including those induced by winds acting on the surface of the ice and at ice off. CO2 production was well predicted by the initial rate of oxygen drawdown near the bottom at ice on and that the upward density flux depended on lake size, with values initially high in all lakes but near molecular in lakes of a few hectares in size by mid-winter. Both CO2 production and within lake vertical fluxes were independent of the rate of cooling in fall and subsequent within lake temperatures under the ice. Anoxia formed near the sediments in all 5 lakes with the concentration of CH4 dependent, in part, on lake size and depth. Twenty to fifty percent of the greenhouse gases produced under the ice remained in the lakes by the time thermal stratification was established in summer despite considerable internal wave induced mixing at the time of ice off. These observations and analysis lay a framework for understanding the links between within lake hydrodynamics, within year variability, and the fraction of greenhouse gases produced over the winter which evade at ice off.

  18. Lake Metabolism: Comparison of Lake Metabolic Rates Estimated from a Diel CO2- and the Common Diel O2-Technique

    PubMed Central

    Peeters, Frank; Atamanchuk, Dariia; Tengberg, Anders; Encinas-Fernández, Jorge; Hofmann, Hilmar

    2016-01-01

    Lake metabolism is a key factor for the understanding of turnover of energy and of organic and inorganic matter in lake ecosystems. Long-term time series on metabolic rates are commonly estimated from diel changes in dissolved oxygen. Here we present long-term data on metabolic rates based on diel changes in total dissolved inorganic carbon (DIC) utilizing an open-water diel CO2-technique. Metabolic rates estimated with this technique and the traditional diel O2-technique agree well in alkaline Lake Illmensee (pH of ~8.5), although the diel changes in molar CO2 concentrations are much smaller than those of the molar O2 concentrations. The open-water diel CO2- and diel O2-techniques provide independent measures of lake metabolic rates that differ in their sensitivity to transport processes. Hence, the combination of both techniques can help to constrain uncertainties arising from assumptions on vertical fluxes due to gas exchange and turbulent diffusion. This is particularly important for estimates of lake respiration rates because these are much more sensitive to assumptions on gradients in vertical fluxes of O2 or DIC than estimates of lake gross primary production. Our data suggest that it can be advantageous to estimate respiration rates assuming negligible gradients in vertical fluxes rather than including gas exchange with the atmosphere but neglecting vertical mixing in the water column. During two months in summer the average lake net production was close to zero suggesting at most slightly autotrophic conditions. However, the lake emitted O2 and CO2 during the entire time period suggesting that O2 and CO2 emissions from lakes can be decoupled from the metabolism in the near surface layer. PMID:28002477

  19. Lake Metabolism: Comparison of Lake Metabolic Rates Estimated from a Diel CO2- and the Common Diel O2-Technique.

    PubMed

    Peeters, Frank; Atamanchuk, Dariia; Tengberg, Anders; Encinas-Fernández, Jorge; Hofmann, Hilmar

    2016-01-01

    Lake metabolism is a key factor for the understanding of turnover of energy and of organic and inorganic matter in lake ecosystems. Long-term time series on metabolic rates are commonly estimated from diel changes in dissolved oxygen. Here we present long-term data on metabolic rates based on diel changes in total dissolved inorganic carbon (DIC) utilizing an open-water diel CO2-technique. Metabolic rates estimated with this technique and the traditional diel O2-technique agree well in alkaline Lake Illmensee (pH of ~8.5), although the diel changes in molar CO2 concentrations are much smaller than those of the molar O2 concentrations. The open-water diel CO2- and diel O2-techniques provide independent measures of lake metabolic rates that differ in their sensitivity to transport processes. Hence, the combination of both techniques can help to constrain uncertainties arising from assumptions on vertical fluxes due to gas exchange and turbulent diffusion. This is particularly important for estimates of lake respiration rates because these are much more sensitive to assumptions on gradients in vertical fluxes of O2 or DIC than estimates of lake gross primary production. Our data suggest that it can be advantageous to estimate respiration rates assuming negligible gradients in vertical fluxes rather than including gas exchange with the atmosphere but neglecting vertical mixing in the water column. During two months in summer the average lake net production was close to zero suggesting at most slightly autotrophic conditions. However, the lake emitted O2 and CO2 during the entire time period suggesting that O2 and CO2 emissions from lakes can be decoupled from the metabolism in the near surface layer.

  20. Simulating ground water-lake interactions: approaches and insights.

    PubMed

    Hunt, Randall J; Haitjema, Henk M; Krohelski, James T; Feinstein, Daniel T

    2003-01-01

    Approaches for modeling lake-ground water interactions have evolved significantly from early simulations that used fixed lake stages specified as constant head to sophisticated LAK packages for MODFLOW. Although model input can be complex, the LAK package capabilities and output are superior to methods that rely on a fixed lake stage and compare well to other simple methods where lake stage can be calculated. Regardless of the approach, guidelines presented here for model grid size, location of three-dimensional flow, and extent of vertical capture can facilitate the construction of appropriately detailed models that simulate important lake-ground water interactions without adding unnecessary complexity. In addition to MODFLOW approaches, lake simulation has been formulated in terms of analytic elements. The analytic element lake package had acceptable agreement with a published LAKI problem, even though there were differences in the total lake conductance and number of layers used in the two models. The grid size used in the original LAKI problem, however, violated a grid size guideline presented in this paper. Grid sensitivity analyses demonstrated that an appreciable discrepancy in the distribution of stream and lake flux was related to the large grid size used in the original LAKI problem. This artifact is expected regardless of MODFLOW LAK package used. When the grid size was reduced, a finite-difference formulation approached the analytic element results. These insights and guidelines can help ensure that the proper lake simulation tool is being selected and applied.

  1. Simulating ground water-lake interactions: Approaches and insights

    USGS Publications Warehouse

    Hunt, R.J.; Haitjema, H.M.; Krohelski, J.T.; Feinstein, D.T.

    2003-01-01

    Approaches for modeling lake-ground water interactions have evolved significantly from early simulations that used fixed lake stages specified as constant head to sophisticated LAK packages for MODFLOW. Although model input can be complex, the LAK package capabilities and output are superior to methods that rely on a fixed lake stage and compare well to other simple methods where lake stage can be calculated. Regardless of the approach, guidelines presented here for model grid size, location of three-dimensional flow, and extent of vertical capture can facilitate the construction of appropriately detailed models that simulate important lake-ground water interactions without adding unnecessary complexity. In addition to MODFLOW approaches, lake simulation has been formulated in terms of analytic elements. The analytic element lake package had acceptable agreement with a published LAK1 problem, even though there were differences in the total lake conductance and number of layers used in the two models. The grid size used in the original LAK1 problem, however, violated a grid size guideline presented in this paper. Grid sensitivity analyses demonstrated that an appreciable discrepancy in the distribution of stream and lake flux was related to the large grid size used in the original LAK1 problem. This artifact is expected regardless of MODFLOW LAK package used. When the grid size was reduced, a finite-difference formulation approached the analytic element results. These insights and guidelines can help ensure that the proper lake simulation tool is being selected and applied.

  2. Okanagan Lake, British Columbia

    NASA Image and Video Library

    1994-10-01

    STS068-155-011 (30 September-11 October 1994) --- (Okanagan Lake, British Columbia) View southward down the lake; Vernon is in the foreground, Kelowna just before the bend in the lake, and Penticton at the far end of the lake. Green crops are still vigorous despite the season (early October); clear-cuts dot the forested hillsides.

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

    NASA Astrophysics Data System (ADS)

    Ito, Yuji; Momii, Kazuro

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

  4. Rediscovery of lake balls in Lake Michigan

    USGS Publications Warehouse

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

    1983-01-01

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

  5. Hydrogeologic setting of the Glacial Lake Agassiz Peatlands, northern Minnesota

    USGS Publications Warehouse

    Siegel, Donald I.

    1981-01-01

    Seven test holes drilled in the Glacial Lake Agassiz Peatlands indicate that the thickness of surficial materials along a north-south traverse parallel to Minnesota Highway 72 ranges from 163 feet near Blackduck, Minnesota to 57 feet about 3 miles south of Upper Red Lake. Lenses of sand and gravel occur immediately above bedrock on the Itasca moraine and are interbedded with lake clay and till under the peatlands. Vertical head gradients measured in a piezometer nest near Blackduck on the moraine are downward, indicative of recharge to the regional ground-water-flow system. Vertical head gradients are upward in a piezometer nest on a sand beach ridge in the peatlands 12 miles north of Upper Red Lake. Numerical sectional models indicate that this discharge probably comes from local flow systems recharged from ground-water mounds located under large raised bogs.

  6. Micromachined electrostatic vertical actuator

    SciTech Connect

    Lee, A.P.; Sommargren, G.E.; McConaghy, C.F.; Krulevitch, P.A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion, micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  7. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P.; Sommargren, Gary E.; McConaghy, Charles F.; Krulevitch, Peter A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  8. A theoretical analysis of vertical flow equilibrium

    SciTech Connect

    Yortsos, Y.C.

    1992-01-01

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

  9. A theoretical analysis of vertical flow equilibrium

    SciTech Connect

    Yortsos, Y.C.

    1992-01-01

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

  10. Assessing Human Impacts on the Water Balance of Lake Victoria Using GRACE and Altimeters.

    NASA Astrophysics Data System (ADS)

    Swenson, S. C.; Wahr, J. M.

    2008-12-01

    GRACE has provided global estimates of vertically integrated water storage anomalies at monthly intervals with a useful spatial resolution of 300-500 km. Water levels of large lakes are now routinely monitored by satellite altimeters. By combining these datasets, it may be possible to separate the effects of climate and human management on lake levels. During the period 2002-2006, the levels of Lake Victoria dropped about two meters. Water storage changes of Lake Victoria and other large lakes in the East African Rift Valley are compared, and the relative impacts of climate and human management are shown to be of similar magnitude.

  11. Water-quality data for Sauk Lake and tributaries near Sauk Centre, Minnesota, 1988-89

    USGS Publications Warehouse

    Mitton, Gregory B.

    1991-01-01

    Water-quality data were collected at 11 sites on Sauk Lake, at sites on 3 major tributaries to the lake, and at the outflow from the lake from September 1988 through August 1989. Data collected from five selected lake sites comprise alkalinity, dissolved-solids concentration, concentrations of nutrients, plankton counts, and chlorophyll a and b. Vertical profiles of specific conductance, pH, temperature, and dissolved oxygen, as well as transparency depths were measured at all lake sites. Discharge, specific conductance, pH, temperature, and dissolved oxygen were measured at the stream sites. Water samples were collected to determine alkalinity and concentrations of suspended solids and nutrients.

  12. Impact of Taihu Lake on city ozone in the Yangtze River Delta

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Zhu, Bin; Gao, Jinhui; Kang, Hanqing

    2017-02-01

    The lake-breeze at Taihu Lake generates a different specific heat capacity between the water body and the surrounding land. Taihu Lake has a significant impact on the atmospheric conditions and the air quality in the Yangtze River Delta. This phenomenon is referred to as the Taihu Lake effect. In this study, two simulations were conducted to determine the impact of the Taihu Lake effect in the reference experiment (R-E) and sensitivity experiments (NO_TH). The control simulations demonstrated that the meteorological field and the spatial distribution of ozone (O3) concentrations over Taihu lake obviously changed once the land-use type of water body was substituted by cropland. The surface temperature of Taihu Lake was reduced under the impact of Taihu Lake, and a huge temperature difference caused a strong lake-breeze effect. The results also showed that the difference in the average concentrations of O3 between the R-E and NO TH experiments reached 12 ppbv in most areas of Taihu Lake, all day, on 20 May 2014. During daytime (0800-1600 LST, LST=UTC+8), the influence of the Taihu Lake effect on O3 in the Suzhou region was not significant. However, the influence of the Taihu Lake effect on O3 in the Suzhou region was obvious during nighttime (1800-2400 LST). The larger changes in the physical and chemical processes were horizontal and vertical advections under the influence of the Taihu Lake effect in Taihu Lake.

  13. Lake Volta, Ghana

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image of Lake Volta in Ghana was acquired March 31, 2002 by the Moderate Resolution Imaging Spectroradiometer (MODIS). Lake Volta is one of the world's largest artificially created lakes. Lake Volta is actually a reservoir formed from the damming of the Volta River, and extends 250 miles north of the Akosombo Dam. The lake covers an area of 8,482 square km. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  14. Lake Chad, Chad, Africa

    NASA Image and Video Library

    1990-04-29

    Africa's Lake Chad where the borders of Chad, Niger, Nigeria and Cameroon merge (13.0N, 14.0E) has been undergoing change for the past 25 to 30 years when it was first noticed that the lake is drying up. Since then, astronauts have been photographing it on a regular basis to record the diminishing lake bed. This lake was once the aproximate size of Lake Erie but is now only about half that size and is still receeding.

  15. Water-quality and lake-stage data for Wisconsin lakes, water years 2008−2011

    USGS Publications Warehouse

    Manteufel, S. Bridgett; Olson, Daniel L.; Robertson, Dale M.; Goddard, Gerald L.

    2016-09-30

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series.The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes during water years 2008–2011. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 2007 through September 30, 2008 is called "water year 2008." Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are presented in this report for water years from 2008–2011. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake’s watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are available via the "USGS Annual Water Data Report" Web site: http://wdr.water.usgs.gov/.

  16. Early observations on an emerging Great Lakes invader Hemimysis anomala in Lake Ontario

    USGS Publications Warehouse

    Walsh, Maureen G.; Lantry, Brian F.; Boscarino, Brent; Bowen, Kelly; Gerlofsma, Jocelyn; Schaner, Ted; Back, Richard; Questel, Jennifer; Smythe, A. Garry; Cap, Roberta; Goehle, Michael; Young, Bryan; Chalupnicki, Marc A.; Johnson, James H.; McKenna, James E.

    2010-01-01

    Hemimysis anomala, a Ponto-Caspian littoral mysid, is an emerging Great Lakes invader that was discovered in Lakes Michigan and Ontario in 2006. Similar to the native mysid Mysis diluviana, Hemimysis exhibits a diel vertical migration pattern but generally inhabits shallower and warmer waters than M. diluviana. Because basic information on the distribution, habitat use, and biology of Hemimysis in the Great Lakes is scarce, the potential for food web disruption by Hemimysis cannot easily be predicted. Preliminary observations indicate widespread invasion of Hemimysis in Lake Ontario. In this study, we confirm the presence of Hemimysis at sites spanning the northern and southern shores of Lake Ontario and the presence of the individuals during winter months. In one horizontal tow in November 2007, over 26,000 individuals were collected with a length range of 4.4 to 9.0. mm and an average caloric density of 611. cal/g wet weight. The most effective methods for sampling Hemimysis were horizontal tows with either a zooplankton net in the water column or a benthic sled near the lake bottom. Although more quantitative data on the life history and distribution of this species is necessary, our preliminary observations support the prediction that the potential for Hemimysis to impact the nearshore food web in Lake Ontario appears high.

  17. Models for extracting vertical crustal movements from leveling data

    NASA Technical Reports Server (NTRS)

    Holdahl, S. H.

    1978-01-01

    Various adjustment strategies are being used in North America to obtain vertical crustal movements from repeated leveling. The more successful models utilize polynomials or multiquadric analysis to describe elevation change with a velocity surface. Other features permit determination of nonlinear motions, motions associated with earthquakes or episodes, and vertical motions of blocks where boundaries are prespecified. The preferred models for estimating crustal motions permit the use of detached segments of releveling to govern the shape of a velocity surface and allow for input from nonleveling sources such as tide gages and paired lake gages. Some models for extracting vertical crustal movements from releveling data are also excellent for adjusting leveling networks, and permit mixing old and new data in areas exhibiting vertical motion. The new adjustment techniques are more general than older static models and will undoubtedly be used routinely in the future as the constitution of level networks becomes mainly relevelings.

  18. Sensitivity of Great Lakes Ice Cover to Air Temperature

    NASA Astrophysics Data System (ADS)

    Austin, J. A.; Titze, D.

    2016-12-01

    Ice cover is shown to exhibit a strong linear sensitivity to air temperature. Upwards of 70% of ice cover variability on all of the Great Lakes can be explained in terms of air temperature, alone, and nearly 90% of ice cover variability can be explained in some lakes. Ice cover sensitivity to air temperature is high, and a difference in seasonally-averaged (Dec-May) air temperature on the order of 1°C to 2°C can be the difference between a low-ice year and a moderate- to high- ice year. The total amount of seasonal ice cover is most influenced by air temperatures during the meteorological winter, contemporaneous with the time of ice formation. Air temperature conditions during the pre-winter conditioning period and during the spring melting period were found to have less of an impact on seasonal ice cover. This is likely due to the fact that there is a negative feedback mechanism when heat loss goes toward cooling the lake, but a positive feedback mechanism when heat loss goes toward ice formation. Ice cover sensitivity relationships were compared between shallow coastal regions of the Great Lakes and similarly shallow smaller, inland lakes. It was found that the sensitivity to air temperature is similar between these coastal regions and smaller lakes, but that the absolute amount of ice that forms varies significantly between small lakes and the Great Lakes, and amongst the Great Lakes themselves. The Lake Superior application of the ROMS three-dimensional hydrodynamic numerical model verifies a deterministic linear relationship between air temperature and ice cover, which is also strongest around the period of ice formation. When the Lake Superior bathymetry is experimentally adjusted by a constant vertical multiplier, average lake depth is shown to have a nonlinear relationship with seasonal ice cover, and this nonlinearity may be associated with a nonlinear increase in the lake-wide volume of the surface mixed layer.

  19. How many species of cichlid fishes are there in African lakes?

    PubMed

    Turner, G F; Seehausen, O; Knight, M E; Allender, C J; Robinson, R L

    2001-03-01

    The endemic cichlid fishes of Lakes Malawi, Tanganyika and Victoria are textbook examples of explosive speciation and adaptive radiation, and their study promises to yield important insights into these processes. Accurate estimates of species richness of lineages in these lakes, and elsewhere, will be a necessary prerequisite for a thorough comparative analysis of the intrinsic and extrinsic factors influencing rates of diversification. This review presents recent findings on the discoveries of new species and species flocks and critically appraises the relevant evidence on species richness from recent studies of polymorphism and assortative mating, generally using behavioural and molecular methods. Within the haplochromines, the most species-rich lineage, there are few reported cases of postzygotic isolation, and these are generally among allopatric taxa that are likely to have diverged a relatively long time in the past. However, many taxa, including many which occur sympatrically and do not interbreed in nature, produce viable, fertile hybrids. Prezygotic barriers are more important, and persist in laboratory conditions in which environmental factors have been controlled, indicating the primary importance of direct mate preferences. Studies to date indicate that estimates of alpha (within-site) diversity appear to be robust. Although within-species colour polymorphisms are common, these have been taken into account in previous estimates of species richness. However, overall estimates of species richness in Lakes Malawi and Victoria are heavily dependent on the assignation of species status to allopatric populations differing in male colour. Appropriate methods for testing the specific status of allopatric cichlid taxa are reviewed and preliminary results presented.

  20. Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 2006

    USGS Publications Warehouse

    Rose, W.J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, D.M.

    2007-01-01

    The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2006 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 2005 through September 30, 2006 is called 'water year 2006.' The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: 'Water Resources Data-Wisconsin, 2006.' Water-resources data, including stage and discharge data at most streamflow-gaging stations, are available through the World Wide Web on the Internet. The Wisconsin Water Science Center's home page is at http://wi.water.usgs.gov/. Information on the

  1. Vertical axis wind turbine

    SciTech Connect

    Cubbers, J.

    1993-07-13

    A vertical axis wind turbine is described comprising: a vertically extending axle supported for rotation about a vertical axis; a series of wind vanes arranged around said axle; support means supporting each of said wind vanes on said axle, each of said wind vanes comprising a substantially flat main panel section of flexible material draped vertically by said support means to extend in a circumferential direction; each of said wind vanes including at least one pocket comprised of a substantially flat overlayer panel of flexible material overlying the outside of said wind vane flexible material panel section and attached thereto along a vertical side by a seam and also attached thereto along the top and bottom, but unattached along the other side to form a normally closed pocket which is able to flare open when wind is blowing from the unattached side thereof and thereby catch said wind, said pocket collapsing when wind blows from the attached side of said overlayer by said overlayer panel again overlying said main panel section.

  2. Hydrologic setting of Williams Lake, Hubbard County, Minnesota

    USGS Publications Warehouse

    Siegel, Donald I.; Winter, Thomas C.

    1980-01-01

    The configuration of the water table and vertical-head gradients measured from July to December 1978 indicate that ground water moves into the lake from the south and east and moves from the lake into the ground-water reservoir to the west. Preliminary numerical models indicate that the sand lens within the till is effectively isolated from the flow system interacting with the lake and that both inseepage and outseepage were about 1.4 inches from mid-July to mid-October 1978. When estimated as a residual in a water balance, ground water showed a net outseepage only of 1.47 inches.

  3. Physiological modifications by seston in response to physicochemical gradients within Lake Superior

    EPA Science Inventory

    Lake Superior is a non-steady state and phosphorus (P) depleted ecosystem. In September 2011, the vertical distribution and composition of dissolved and particulate P-pools throughout the Lake were examined. Differences in seston P content were evident with depth, as average sest...

  4. Physiological modifications by seston in response to physicochemical gradients within Lake Superior

    EPA Science Inventory

    Lake Superior is a non-steady state and phosphorus (P) depleted ecosystem. In September 2011, the vertical distribution and composition of dissolved and particulate P-pools throughout the Lake were examined. Differences in seston P content were evident with depth, as average sest...

  5. GEOCHEMICAL FEATURES OF WATER-ROCK INTERACTIONS AT THE SULPHUR BANK MERCURY MINE, LAKE COUNTY, CALIFORNIA

    EPA Science Inventory

    The Sulphur Bank Mercury Mine on the eastern shore of Clear Lake is the source of poor quality acid mine drainage seeping into Clear Lake. Lateral and vertical geochemical trends in ground water composition point to a number of redox reactions taking place as a function of subsu...

  6. GEOCHEMICAL FEATURES OF WATER-ROCK INTERACTIONS AT THE SULPHUR BANK MERCURY MINE, LAKE COUNTY, CALIFORNIA

    EPA Science Inventory

    The Sulphur Bank Mercury Mine on the eastern shore of Clear Lake is the source of poor quality acid mine drainage seeping into Clear Lake. Lateral and vertical geochemical trends in ground water composition point to a number of redox reactions taking place as a function of subsu...

  7. Aerosol Production from the Great Lakes Surface

    NASA Astrophysics Data System (ADS)

    Slade, J. H.; Mwaniki, G.; Bertman, S. B.; Vanreken, T. M.; Shepson, P. B.

    2009-12-01

    It is well understood that oceans generate airborne particulate matter from mechanical processes such as sea spray and bubble bursting. These particles are primarily composed of salts and other nonvolatile inorganic material; however, the organic mass fraction can vary by location and the extent of biological activity. The size distributions of aerosols in these environments depend greatly on relative humidity with diameters ranging from typically several hundred nanometers to several micrometers. There has been much less discussion of particle formation from fresh water ecosystems, a hub for organic activity, and thus a more likely medium for organic aerosol production. We investigated particle formation over the Great Lakes during the summer of 2009 as a part of the Community Atmosphere-Biosphere Interactions Experiments (CABINEX) at the University of Michigan Biological Station (UMBS) in Pellston, MI. With a scanning mobility particle sizer (SMPS) aboard Purdue University’s Airborne Laboratory for Atmospheric Research (ALAR) for size-distribution analysis of accumulation-mode aerosol, we conducted vertical profiles above Lake Michigan and the UMBS deciduous forest, and transects across the peninsula between Lakes Michigan and Huron to study particle formation, transport, and deposition. Preliminary results reveal a well-mixed troposphere above the forest with a mode ~0.1 μm, while in several cases, the total particle concentration over Lake Michigan is an order of magnitude greater than over the forest. There is a consistent bimodal distribution of particle sizes over Lake Michigan the lowest of which is centered at ~0.025 μm, suggesting the possibility of new particle formation. This mode is consistent with the presence of breaking waves on the lake’s surface, and this mode and the vertical structure depend greatly on wind speed. We present here evidence for new particle production from breaking waves on fresh water lakes, and discuss the results

  8. Life history of lake herring of Green Bay, Lake Michigan

    USGS Publications Warehouse

    Smith, Stanford H.

    1956-01-01

    Although the lake herring has been an important contributor to the commercial fish production of Green Bay, little has been known about it. This study is based on field observations and data from about 6,500 lake herring collected over the period 1948 to 1952. Relatively nonselective commercial pound nets were a primary source of material for the study of age and growth. Commercial and experimental gill nets were used to obtain data on gear selectivity and vertical distribution. Scales were employed to investigate age and growth. Age group IV normally dominated commercial catches during the first half of the calendar year and age group III the last half. At these ages the fish averaged about 10.5 inches in length. The season's growth started in May, was most rapid in July, and terminated near the end of October. The sexes grew at the same rate. Selectivity of fishing gear was found to influence the estimation of growth. Geographical and annual differences in growth are shown. Factors that might contribute to discrepancies in calculated growth are evaluated. Possible real and apparent causes of growth compensation are given. The relation between length and weight is shown to vary with sex, season, year, and method of capture. Females were relatively more plentiful in commercial catches in February than in May through December. The percentage of females decreased with increase in age in pound-net catches but increased with age in gill-net samples. Within a year class the percentage of females decreased with increase in age. Most Green Bay lake herring mature during their second or third year of life. They are pelagic spawners with most intensive spawning over shallow areas. Spawning takes place between mid-November and mid-December, and eggs hatch in April and May. Lake herring ovaries contained from 3,500 to 11,200 eggs (averaged 6,375). Progress of spawning by age, sex, and length is given. Lake herring were distributed at all depths in Green Bay in early May, were

  9. Using multiple environmental methods to estimate groundwater discharge into an arid lake (Dakebo Lake, Inner Mongolia, China)

    NASA Astrophysics Data System (ADS)

    Su, Xiaosi; Cui, Geng; Du, Shanghai; Yuan, Wenzhen; Wang, Huang

    2016-11-01

    It is important to have both a qualitative and quantitative understanding of the hydraulic exchange between groundwater and surface water to support the development of effective management plans for sustainable use of water resources. Groundwater is a major source of surface-water recharge and plays an important role in maintaining the integrity of ecosystems, especially within wetlands in semi-arid regions. The Ordos Desert Plateau of Inner Mongolia (China) is a vulnerable ecosystem that suffers from an extreme lack of water. The hydraulic exchange between groundwater and lake water in Dakebo Lake (the largest of hundreds of lakes on the Ordos Desert Plateau) was evaluated using multiple environmental methods. Continuous monitoring of the groundwater and lake-water levels indicated that the lake was recharged vertically by groundwater. Application of hydrodynamic and temperature tracing methods to the western side of the lake indicated that the rate of groundwater discharge to the lake was about 2 × 10-6 to 3 × 10-6 m/s in spring, summer, and autumn, but that there was no recharge in winter because the hypolentic zone (HZ) was frozen. Mixing ratios of groundwater and lake water in the HZ, estimated from the 18O and 2H ratios, showed that there were spatial variations in the hydrodynamic exchange between groundwater and lake water within the HZ.

  10. [Duane vertical surgical treatment].

    PubMed

    Merino, M L; Gómez de Liaño, P; Merino, P; Franco, G

    2014-04-01

    We report 3 cases with a vertical incomitance in upgaze, narrowing of palpebral fissure, and pseudo-overaction of both inferior oblique muscles. Surgery consisted of an elevation of both lateral rectus muscles with an asymmetrical weakening. A satisfactory result was achieved in 2 cases, whereas a Lambda syndrome appeared in the other case. The surgical technique of upper-insertion with a recession of both lateral rectus muscles improved vertical incomitance in 2 of the 3 patients; however, a residual deviation remains in the majority of cases. Copyright © 2011 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.

  11. A vertical cephalometric analysis.

    PubMed

    Alió Sanz, Juan J; Iglesias Conde, Carmen

    2007-01-01

    Correctly assessing open-bite malocclusions has remained problematic because clinicians have not had entirely reliable methods of determining the exact amount of skeletal and dental contributions to the problem. A new cephalometric technique, the vertical cephalometric analysis, offers orthodontists a system that precisely identifies the percentage of skeletal and dentoalveolar components that open-bite patients have. The vertical cephalometric analysis offers a discriminating diagnostic method for evaluating, diagnosing, and treatment planning for patients with open bite. This technique will allow clinicians to classify patients with accuracy, as well as to establish prognoses and select therapies.

  12. Using Fiber Optic Distributed Temperature Sensing (DTS) to Assess Groundwater-Lake Exchange in an Acid Mine Lake in Eastern Germany

    NASA Astrophysics Data System (ADS)

    Hausner, M. B.; Fleckenstein, J.; Neumann, C.; Tyler, S. W.

    2008-12-01

    Groundwater flows through contaminated mine sites are a major concern in many parts of the world. In this study, a variety of instrumentation was used to locate and quantify groundwater inflows into an acid lake on an abandoned mine site in Brandenburg, Germany. While previously-installed piezometers and seepage meters had identified several points of groundwater influx into the lake, such techniques are spatially limited to the point of installation. To address this limitation, a fiber-optic distributed temperature sensor (DTS) was deployed across the lake bottom and in vertical profilers to confirm and expand the previously generated data sets. Fiber-optic DTS, a relatively new technology, provides the opportunity to measure temperature on very high spatial and temporal scales using Raman spectra scattering of pulsed light within a glass fiber. A 1000 meter cable was deployed spatially along the sediment-water interface to identify spatially scattered areas of groundwater inflow, while two high-resolution probes (which return temperature readings every 2.4 vertical cm) were installed vertically near existing seepage meters. Preliminary analysis of the vertical deployments showed substantial groundwater upwelling, confirming the results of previous seepage meter measurements which showed significant vertical flux into the lake. Ongoing analysis of the lateral deployment is expected to identify areas in which there are anomalies in the diurnal temperature cycle at the lake bottom; such anomalies may indicate groundwater influx into the lake. These areas will be used to locate future seepage meter and piezometer installations.

  13. Lake Nasser and Toshka Lakes, Egypt

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Lake Nasser (center) and the Toshka Lakes (center left) glow emerald green and black in this MODIS true-color image acquired March 8, 2002. Located on and near the border of Egypt and Norther Sudan, these lakes are an oasis of water in between the Nubian (lower right) and Libyan Deserts (upper left). Also visible are the Red Sea (in the upper right) and the Nile River (running north from Lake Nasser). Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  14. A microsatellite-based genetic linkage map and putative sex-determining genomic regions in Lake Victoria cichlids.

    PubMed

    Kudo, Yu; Nikaido, Masato; Kondo, Azusa; Suzuki, Hikoyu; Yoshida, Kohta; Kikuchi, Kiyoshi; Okada, Norihiro

    2015-04-15

    Cichlid fishes in East Africa have undergone extensive adaptive radiation, which has led to spectacular diversity in their morphology and ecology. To date, genetic linkage maps have been constructed for several tilapias (riverine), Astatotilapia burtoni (Lake Tanganyika), and hybrid lines of Lake Malawi cichlids to facilitate genome-wide comparative analyses. In the present study, we constructed a genetic linkage map of the hybrid line of Lake Victoria cichlids, so that maps of cichlids from all the major areas of East Africa will be available. The genetic linkage map shown here is derived from the F2 progeny of an interspecific cross between Haplochromis chilotes and Haplochromis sauvagei and is based on 184 microsatellite and two single-nucleotide polymorphism (SNP) markers. Most of the microsatellite markers used in the present study were originally designed for other genetic linkage maps, allowing us to directly compare each linkage group (LG) among different cichlid groups. We found 25 LGs, the total length of which was 1133.2cM with an average marker spacing of about 6.09cM. Our subsequent linkage mapping analysis identified two putative sex-determining loci in cichlids. Interestingly, one of these two loci is located on cichlid LG5, on which the female heterogametic ZW locus and several quantitative trait loci (QTLs) related to adaptive evolution have been reported in Lake Malawi cichlids. We also found that V1R1 and V1R2, candidate genes for the fish pheromone receptor, are located very close to the recently detected sex-determining locus on cichlid LG5. The genetic linkage map study presented here may provide a valuable foundation for studying the chromosomal evolution of East African cichlids and the possible role of sex chromosomes in generating their genomic diversity. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Modern lacustrine stromatolites, Walker Lake, Nevada

    NASA Astrophysics Data System (ADS)

    Osborne, Robert H.; Licari, Gerald R.; Link, Martin H.

    1982-05-01

    The Walker River drainage basin occupies about 10,000 km 2 in western Nevada and parts of California and is essentially a closed hydrologic system which drains from the crest of the Sierra Nevada in California and terminates in Walker Lake, Nevada. Walker Lake trends north and is about 27.4 km long and 8 km wide with water depths exceeding 30.5 m. The lake is situated in an asymmetric basin with steep alluvial fans flanking the western shoreline (Wassuk Range) and more gentle but areally more extensive alluvial fans flanking the eastern shoreline (Gillis Range). Exposed lake terraces and the present shoreline of Walker Lake record a sequence of Pleistocene and Holocene stromatolitic and tufaceous carbonate deposits. Small generalized and columnar stromatolites, frequently encrusted on exposed coarse-grained clasts or bedrock, are present along parts of the nearshore margin of Walker Lake and at elevated lake stands. Columnar stromatolites as much as 4 cm high are subcylindrical to club shaped discrete, and laterally linked at the base with local branching. These digitate stromatolites start as wavy, generalized stromatolites which are vertically transitional to small, laterally linked cabbage heads with laminae which thicken over the crests. Although algal structures are not well preserved in the older stromatolites, recent precipitation of low magnesium calcite occurs as smooth encrustations and as tiny mounds which are consistently associated with a diverse, seasonally variable, green and blue-green algal community including Cladophora glomerata, Ulothrix (cf. aequalis), Gongrosira, Schizothrix, Amphithrix janthina, Calothrix, Homeothrix, Spirulina, Anabaena, Lyngbya, and Entophysalis. Cladophora glomerata and a species of Ulothrix, which are the two most abundant algae within the Walker Lake stromatolite community, are known to condition semi-alkaline lake water by the removal of CO 2 from bicarbonate during photosynthesis. Such conditioning results in the

  16. Water-quality and lake-stage data for Wisconsin lakes, water years 2012–2013

    USGS Publications Warehouse

    Manteufel, S. Bridgett; Robertson, Dale M.

    2017-05-25

    IntroductionThe U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2012 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 2011 through September 30, 2012, is called “water year 2012.”The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake’s watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published online at http://nwis.waterdata.usgs.gov/wi/nwis.Water-resources data, including stage and discharge data at most streamflow-gaging stations, are available online. The Wisconsin Water Science Center’s home page is at https://www.usgs.gov/centers/wisconsin-water-science-center. Information on

  17. Water-quality and lake-stage data for Wisconsin lakes, water year 2014

    USGS Publications Warehouse

    Manteufel, S. Bridgett; Robertson, Dale M.

    2017-05-25

    IntroductionThe U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a database for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The locations of water-quality and lake-stage stations in Wisconsin for water year 2014 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the periodOctober 1, 2013, through September 30, 2014, is called “water year 2014.”The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus, and chlorophyll a concentrations collected during nonfrozen periods are included for many lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes the location of the lake, area of the lake’s watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published online at http://nwis.waterdata.usgs.gov/wi/nwis.Water-resources data, including stage and discharge data at most streamflow-gaging stations, are available online. The Wisconsin Water Science Center’s home page is at https://www.usgs.gov/centers/wisconsin-water-science-center. Information

  18. Features of lava lake filling and draining and their implications for eruption dynamics

    USGS Publications Warehouse

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

    2009-01-01

    Lava lakes experience filling, circulation, and often drainage depending upon the style of activity and location of the vent. Features formed by these processes have proved difficult to document due to dangerous conditions during the eruption, inaccessibility, and destruction of features during lake drainage. Kilauea Iki lava lake, Kilauea, Hawai'i, preserves many such features, because lava ponded in a pre-existing crater adjacent to the vent and eventually filled to the level of, and interacted with, the vent and lava fountains. During repeated episodes, a cyclic pattern of lake filling to above vent level, followed by draining back to vent level, preserved features associated with both filling and draining. Field investigations permit us to describe the characteristic features associated with lava lakes on length scales ranging from centimeters to hundreds of meters in a fashion analogous to descriptions of lava flows. Multiple vertical rinds of lava coating the lake walls formed during filling as the lake deepened and lava solidified against vertical faces. Drainage of the lake resulted in uneven formation of roughly horizontal lava shelves on the lakeward edge of the vertical rinds; the shelves correlate with stable, staggered lake stands. Shelves either formed as broken relict slabs of lake crust that solidified in contact with the wall or by accumulation, accretion, and widening at the lake surface in a dynamic lateral flow regime. Thin, upper lava shelves reflect an initially dynamic environment, in which rapid lake lowering was replaced by slower and more staggered drainage with the formation of thicker, more laterally continuous shelves. At all lava lakes experiencing stages of filling and draining these processes may occur and result in the formation of similar sets of features. ?? Springer-Verlag 2009.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  20. Aiding Vertical Guidance Understanding

    NASA Technical Reports Server (NTRS)

    Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen

    1998-01-01

    A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.

  1. Vertical shaft windmill

    NASA Technical Reports Server (NTRS)

    Grana, D. C.; Inge, S. V., Jr. (Inventor)

    1983-01-01

    A vertical shaft has several equally spaced blades mounted. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.

  2. Lake Huron LAMPs

    EPA Pesticide Factsheets

    The approach in Lake Huron differs from the Lakewide Management Plans of the other Great Lakes: no formal binational designation of lakewide beneficial use impairments, nor extensive lakewide modeling of chemical loadings

  3. Lake Tahoe Projects

    EPA Pesticide Factsheets

    Information on the Lake Tahoe watershed, EPA's protection efforts, water quality issues, effects of climate, change, Lake Tahoe Total Maximum Daily Load TMDL), EPA-sponsored projects, list of partner agencies.

  4. The Great Lakes

    EPA Pesticide Factsheets

    The Great Lakes form the largest surface freshwater system on Earth. The U.S. and Canada work together to restore and protect the environment in the Great Lakes Basin. Top issues include contaminated sediments, water quality and invasive species.

  5. Lakes on Titan

    NASA Image and Video Library

    2006-07-24

    The Cassini spacecraft, using its radar system, has discovered very strong evidence for hydrocarbon lakes on Titan. Dark patches, which resemble terrestrial lakes, seem to be sprinkled all over the high latitudes surrounding Titan north pole

  6. Looking Down on Lakes

    NASA Image and Video Library

    2014-04-07

    NASA Cassini spacecraft peers down though layers of haze to glimpse the lakes of Titan northern regions. Titan has a hydrological cycle similar to Earth, but instead of water, Titan lakes and seas are filled with liquid methane and ethane.

  7. Lakes Ecosystem Services Online

    EPA Science Inventory

    Northeastern lakes provide valuable ecosystem services that benefit residents and visitors and are increasingly important for provisioning of recreational opportunities and amenities. Concurrently, however, population growth threatens lakes by, for instance, increasing nutrient ...

  8. National Lakes Assessment

    EPA Pesticide Factsheets

    The National Lakes Assessment is a collaborative, statistical survey of the nation's lakes. It is one of four national surveys that EPA and its partners conduct to assess the condition and health of the nation's water resources.

  9. About Lake Tahoe

    EPA Pesticide Factsheets

    Information on the Lake Tahoe watershed, EPA's protection efforts, water quality issues, effects of climate, change, Lake Tahoe Total Maximum Daily Load TMDL), EPA-sponsored projects, list of partner agencies.

  10. Lakes Ecosystem Services Online

    EPA Science Inventory

    Northeastern lakes provide valuable ecosystem services that benefit residents and visitors and are increasingly important for provisioning of recreational opportunities and amenities. Concurrently, however, population growth threatens lakes by, for instance, increasing nutrient ...

  11. Lake trout rehabilitation in Lake Ontario

    USGS Publications Warehouse

    Elrod, Joseph H.; O'Gorman, Robert; Schneider, Clifford P.; Eckert, Thomas H.; Schaner, Ted; Bowlby, James N.; Schleen, Larry P.

    1995-01-01

    Attempts to maintain the native lake trout (Salvelinus namaycush) population in Lake Ontario by stocking fry failed and the species was extirpated by the 1950s. Hatchery fish stocked in the 1960s did not live to maturity because of sea lamprey (Petromyzon marinus) predation and incidental commercial harvest. Suppression of sea lampreys began with larvicide treatments of Lake Ontario tributaries in 1971 and was enhanced when the tributaries of Oneida Lake and Lake Erie were treated in the 1980s. Annual stocking of hatchery fish was resumed with the 1972 year class and peaked at about 1.8 million yearlings and 0.3 million fingerlings from the 1985–1990 year classes. Survival of stocked yearlings declined over 50% in the 1980 s and was negatively correlated with the abundance of lake trout > 550 mm long (r = −0.91, P < 0.01, n = 12). A slot length limit imposed by the State of New York for the 1988 fishing season reduced angler harvest. Angler harvest in Canadian waters was 3 times higher in eastern Lake Ontario than in western Lake Ontario. For the 1977–1984 year classes, mean annual survival rate of lake trout age 6 and older was 0.45 (range: 0.35–0.56). In U.S. waters during 1985–1992, the total number of lake trout harvested by anglers was about 2.4 times greater than that killed by sea lampreys. The number of unmarked lake trout < 250 mm long in trawl catches in 1978–1992 was not different from that expected due to loss of marks and failure to apply marks at the hatchery, and suggested that recruitment of naturally-produced fish was nil. However, many of the obstacles which may have impeded lake trout rehabilitation in Lake Ontario during the 1980s are slowly being removed, and there are signs of a general ecosystem recovery. Significant recruitment of naturally produced lake trout by the year 2000, one interim objective of the rehabilitation plan for the Lake, may be achieved.

  12. A Killer Lake

    ERIC Educational Resources Information Center

    Horvath, Thomas

    2005-01-01

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

  13. Lake Layers: Stratification.

    ERIC Educational Resources Information Center

    Brothers, Chris; And Others

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

  14. Great Minds? Great Lakes!

    ERIC Educational Resources Information Center

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

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

  15. Great Lakes: Chemical Monitoring

    ERIC Educational Resources Information Center

    Delfino, Joseph J.

    1976-01-01

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

  16. A Killer Lake

    ERIC Educational Resources Information Center

    Horvath, Thomas

    2005-01-01

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

  17. Great Lakes in January

    NASA Image and Video Library

    2017-09-28

    This image taken on January 13, 2015 from the Suomi NPP satellite's VIIRS instrument shows the Great Lakes and surrounding areas. The latest Great Lakes Surface Environmental Analysis (GLSEA) from the NOAA Great Lakes Environmental Research Laboratory shows total ice cover of 29.3% as of January 13th. Credit: NOAA/NASA/NPP Via NOAA Environmental Visualization Laboratory

  18. Great Lakes: Chemical Monitoring

    ERIC Educational Resources Information Center

    Delfino, Joseph J.

    1976-01-01

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

  19. Lake Effects: The Lake Superior Curriculum Guide.

    ERIC Educational Resources Information Center

    Beery, Tom; And Others

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

  20. Lake Effects: The Lake Superior Curriculum Guide.

    ERIC Educational Resources Information Center

    Beery, Tom; And Others

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

  1. The Nyanza Project: Interdisciplinary Research Training In Tropical Lakes

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    The Nyanza Project is a research training program for American and African students, run annually at Lake Tanganyika (LT), Tanzania. The Project`s objective is to provide undergraduates, graduate students and secondary school teachers with the skills to plan and conduct interdisciplinary research on various aspects of tropical lake studiees. At a time of rapid global change there is a pressing need for young scientists trained to investigate environmental processes in an interdisciplinary framework. Training students to understand long-term changes in water availability, water quality and the relationship of aquatic ecosystems to rapid climate change represents a critical element of this societal need. Waterbodies in the tropics are particularly useful proving grounds for training future researchers on the impacts of global change on natural waters, as they are very sensitive to environmental and climatic change. Moreover, they are likely to provide instructive bellwethers of changes to come in U.S. inland waters. Each year 17-22 undergraduates, 3-4 graduate students and one secondary school teacher are selected for the program from the US and Africa. To date (1998-2005), 89 undergraduate students, 24 graduate students, and 8 secondary school teachers from the US have participated through the Project`s NSF support and 58 African students (from Tanzania, Burundi, Zambia, Congo, Kenya, and Burkina Faso) have been funded to participate in the Nyanza Project through supporting grants from our non-NSF funding sources. The 7-week program comprises an initial two week intensive short course on all aspects of the LT system and project preparation period, followed by 5 weeks of directed research, written report preparation, and scientific meeting-styled presentations. Focal topics for Nyanza Project research include: 1) investigating East African paleoclimates using sediment cores and reflection seismic profiling, 2) mapping & interpreting the geologic structure and

  2. Vertical orbital dystopia.

    PubMed

    Tan, S T; Ashworth, G; Czypionka, S; Poole, M D; Briggs, M

    1996-06-01

    Many pathologic processes may lead to vertical orbital dystopia. We reviewed 47 consecutive cases seen over a 13-year period. Twenty-nine patients underwent eye leveling procedures to improve cosmesis, 2 of these by camouflage procedures and 27 by orbital translocation. Ten patients had 16 secondary operations. There was one death, serious complications occurred in 3 patients, and nuisance complications occurred in 20 others. Seven patients developed diplopia postoperatively, and in 6 patients it was troublesome. In these, it resolved fully in 2 patients, improved to be of no consequence in 2, and in the remaining 2 troublesome symptoms persisted requiring inferior oblique muscle recession in 1. Binocular vision was never restored when not present preoperatively, and in 3 patients temporary loss occurred. There was an overall modest but significant improvement in appearance after surgery. It is concluded that vertical orbital translocation is rewarding and worthwhile.

  3. Geochemical and biochemical evidence of lake overturn and fish kill at Lake Averno, Italy

    NASA Astrophysics Data System (ADS)

    Caliro, S.; Chiodini, G.; Izzo, G.; Minopoli, C.; Signorini, A.; Avino, R.; Granieri, D.

    2008-12-01

    Lake Averno is situated in the homonymous crater in the northwestern sector of the Campi Flegrei active volcanic system in Campania region, Italy. In February 2005 a fish kill event was observed in the lake, prompting a geochemical survey to ascertain the possible cause. In February 2005 a geochemical survey revealed that the lake water was unstratified chemically and isotopically, presumably, as a result of lake overturn. This fish kill phenomenon was recorded at least two other times in the past. In contrast to the February 2005 results, data collected in October 2005, shows the Lake Averno to be stratified, with an oxic epilimnion (surface to 6 m) and an anoxic hypolimnion (6 m to lake bottom at about 33 m). Chemical and isotopic compositions of Lake Averno waters suggest an origin by mixing of shallow waters with a Na-Cl hydrothermal component coupled with an active evaporation process. The isotopic composition of Dissolved Inorganic Carbon, as well as the composition of the non-reactive dissolved gas species again supports the occurrence of this mixing process. Decreasing levels of SO 4 and increasing levels of H 2S and CH 4 contents in lake water with depth, strongly suggests anaerobic bacterial processes are occurring through decomposition of organic matter under anoxic conditions in the sediment and in the water column. Sulfate reduction and methanogenesis processes coexist and play a pivotal role in the anaerobic environment of the Lake Averno. The sulfate reducing bacterial activity has been estimated in the range of 14-22 μmol m - 2 day - 1 . Total gas pressure of dissolved gases ranges between 800 and 1400 mbar, well below the hydrostatic pressure throughout the water column, excluding the possibility, at least at the survey time, of a limnic eruption. Vertical changes in the density of lake waters indicate that overturn may be triggered by cooling of epilimnetic waters below 7 °C. This is a possible phenomenon in winter periods if atmospheric

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

    NASA Astrophysics Data System (ADS)

    Dawidek, J.; Ferencz, B.

    2013-08-01

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

  5. Limnology and fish ecology of sockeye salmon nursery lakes of the world

    USGS Publications Warehouse

    Hartman, Wilbur L.; Burgner, R.L.

    1972-01-01

    Many important, recently glaciated oligotrophic lakes that lie in coastal regions around the northern rim of the Pacific Ocean produce anadromous populations of sockeye salmon, Oncorhynchus nerka. This paper describes the limnology and fish ecology of two such lakes in British Columbia, five in Alaska, and one in Kamchatka. Then we discuss the following general topics: the biogenic eutrophication of nursery lakes from the nutrients released from salmon carcasses wherein during years of highest numbers of spawners, lake phosphate balances in Lakes Babine, Iliamna, and Dalnee are significantly affected; the use of nursery lakes by young sockeye that reveals five patterns related to size and configuration of lake basins and the distribution of spawning areas; the interactions between various life history stages of sockeye salmon and such resident predators, competitors, and prey as Arctic char, lake trout, Dolly Varden, cutthroat trout, lake whitefish, pygmy whitefish, pond smelt, sticklebacks, and sculpins; the self-regulation of sockeye salmon abundance in these nursery lakes as controlled by density-dependent processes; the interrelations between young sockeye salmon biomass and growth rates, and zooplankton abundance in Babine Lake; and finally, the diel, vertical, pelagial migratory behavior of young sockeye in Babine Lake and the new hypothesis dealing with bioenergetic conservation.

  6. 'Endurance' All Around Vertical)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 360-degree view of the terrain surrounding NASA's Mars Exploration Rover Opportunity was taken on the rover's 171st sol on Mars (July 17, 2004). It was assembled from images taken by the rover's navigation camera at a position referred to as 'site 33.' Opportunity had driven 11 meters (36 feet) into 'Endurance Crater.' The view is a vertical projection with geometrical seam correction.

  7. Hilly Surroundings (vertical)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 360-degree view of the terrain surrounding NASA's Mars Exploration Rover Spirit was taken on the rover's 189th sol on Mars (July 15, 2004). It was assembled from images taken by the rover's navigation camera at a position referred to as Site 72, which is at the base of the 'West Spur' portion of the 'Columbia Hills.'' The view is presented in a vertical projection with geometrical seam correction.

  8. Protective Vertical Shelters.

    DTIC Science & Technology

    1983-06-29

    on Generic MX Structures" by John Betz. 5. (AFCMD/82-013) "Finite Element Dynamic Analysis of th, DCT-2 Models" by Barry Bingham . 61 (AFCMD/82-017) "MX...facility to define the HEST structure for the GOVS tests. A SAMSON dynamic finite-element computer code provided pretest predictions of strdsses and...as piecewise linear, elastic- plastic materials. TEST DESCRIPTION Shel ter Models The generic MX vertical shelter is basically a large, reinforced

  9. Vertical bloch line memory

    NASA Technical Reports Server (NTRS)

    Katti, Romney R. (Inventor); Stadler, Henry L. (Inventor); Wu, Jiin-chuan (Inventor)

    1995-01-01

    A new read gate design for the vertical Bloch line (VBL) memory is disclosed which offers larger operating margin than the existing read gate designs. In the existing read gate designs, a current is applied to all the stripes. The stripes that contain a VBL pair are chopped, while the stripes that do not contain a VBL pair are not chopped. The information is then detected by inspecting the presence or absence of the bubble. The margin of the chopping current amplitude is very small, and sometimes non-existent. A new method of reading Vertical Bloch Line memory is also disclosed. Instead of using the wall chirality to separate the two binary states, the spatial deflection of the stripe head is used. Also disclosed herein is a compact memory which uses vertical Bloch line (VBL) memory technology for providing data storage. A three-dimensional arrangement in the form of stacks of VBL memory layers is used to achieve high volumetric storage density. High data transfer rate is achieved by operating all the layers in parallel. Using Hall effect sensing, and optical sensing via the Faraday effect to access the data from within the three-dimensional packages, an even higher data transfer rate can be achieved due to parallel operation within each layer.

  10. Stream, Lake, and Reservoir Management.

    PubMed

    Dai, Jingjing; Mei, Ying; Chang, Chein-Chi

    2017-10-01

    This review on stream, lake, and reservoir management covers selected 2016 publications on the focus of the following sections: Stream, lake, and reservoir management • Water quality of stream, lake, and reservoir • Reservoir operations • Models of stream, lake, and reservoir • Remediation and restoration of stream, lake, and reservoir • Biota of stream, lake, and reservoir • Climate effect of stream, lake, and reservoir.

  11. Depth-related gradients of viral activity in Lake Pavin.

    PubMed

    Colombet, J; Sime-Ngando, T; Cauchie, H M; Fonty, G; Hoffmann, L; Demeure, G

    2006-06-01

    High-resolution vertical sampling and determination of viral and prokaryotic parameters in a deep volcanic lake shows that in the absence of thermal stratification but within light, oxygen, and chlorophyll gradients, host availability empirically is prevalent over the physical and chemical environments and favors lytic over lysogenic "viral life cycles."

  12. Unusual bacterioplankton community structure in ultra-oligotrophic Crater Lake

    USGS Publications Warehouse

    Urbach, Ena; Vergin, Kevin L.; Morse, Ariel

    2001-01-01

    The bacterioplankton assemblage in Crater Lake, Oregon (U.S.A.), is different from communities found in other oxygenated lakes, as demonstrated by four small subunit ribosomal ribonucleic acid (SSU rRNA) gene clone libraries and oligonucleotide probe hybridization to RNA from lake water. Populations in the euphotic zone of this deep (589 m), oligotrophic caldera lake are dominated by two phylogenetic clusters of currently uncultivated bacteria: CL120-10, a newly identified cluster in the verrucomicrobiales, and ACK4 actinomycetes, known as a minor constituent of bacterioplankton in other lakes. Deep-water populations at 300 and 500 m are dominated by a different pair of uncultivated taxa: CL500-11, a novel cluster in the green nonsulfur bacteria, and group I marine crenarchaeota. b-Proteobacteria, dominant in most other freshwater environments, are relatively rare in Crater Lake (<=16% of nonchloroplast bacterial rRNA at all depths). Other taxa identified in Crater Lake libraries include a newly identified candidate bacterial division, ABY1, and a newly identified subcluster, CL0-1, within candidate division OP10. Probe analyses confirmed vertical stratification of several microbial groups, similar to patterns observed in open-ocean systems. Additional similarities between Crater Lake and ocean microbial populations include aphotic zone dominance of group I marine crenarchaeota and green nonsulfur bacteria. Comparison of Crater Lake to other lakes studied by rRNA methods suggests that selective factors structuring Crater Lake bacterioplankton populations may include low concentrations of available trace metals and dissolved organic matter, chemistry of infiltrating hydrothermal waters, and irradiation by high levels of ultraviolet light.

  13. Responses of subepilimnetic primary producers to experimental lake acidification

    SciTech Connect

    Moffett, M.F.

    1991-01-01

    Subepilimnetic phytoplankton communities were found to increase in abundance during experimental acidification with sulfuric acid of two Canadian Shield lakes, Lake 223 and Lake 302S, at the Experimental Lakes Area (ELA) in northwestern Ontario. As epilimnetic pH declined in Lake 223, small, edible species of phytoplankton increased more than larger, less edible taxa. Species diversity ultimately decreased when epilimnetic acidity reached the target pH 5.0. In Lake 302S algal populations, Chrysochromulina spp. and Chlamydomonas sp., reached [open quotes]bloom[close quotes] conditions below the epilimnion in the third and fourth summers, respectively, of sulfuric acid additions as pH declined from above pH 6 to pH 5.6 and 5.4. Meta- and hypolimnetic waters of these lakes did not experience similar declines in pH. All responses in Lake 223 and Lake 302S were in contrast to communities in 5-10 ELA lakes not undergoing acidification. Vertical depth profiles of chlorophyll fluorescence were used to follow trends in subepilimnetic communities during the first four years of sulfuric acid additions to Lake 302S. Fluorescence was found to reliably predict chlorophyll a concentrations (r[sup 2] = 0.80-0.94). Characteristics of subepilimnetic communities and the habitats in which they were located were studied at the ELA. Many were mixed with photosynthetic bacteria. Fluorometric techniques with DCMU (3-(3,4-dichlorophenyl-1,1-dimethyl urea)) were used to determine which fluorescence maxima contained viable algal populations. In situ inorganic carbon uptake rates for the algal-dominated communities below the epilimnion were similar to rates by epilimnetic communities. Enclosure experiments demonstrated that growth and inorganic carbon uptake rates of subepilimnetic algal populations were light-limited.

  14. Hazardous crater lakes studied

    NASA Astrophysics Data System (ADS)

    Kusakabe, Minoru

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

  15. Lake trout rehabilitation in Lake Huron

    USGS Publications Warehouse

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

    1995-01-01

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

  16. An event-driven phytoplankton bloom in southern Lake Michigan observed by satellite.

    SciTech Connect

    Lesht, B. M.; Stroud, J. R.; McCormick, M. J.; Fahnenstiel, G. L.; Stein, M. L.; Welty, L. J.; Leshkevich, G. A.; Environmental Research; Univ. of Chicago; Great Lakes Research Lab.

    2002-04-15

    Sea-viewing Wide Field-of-View Sensor (SeaWiFS) images from June 1998 show a surprising early summer phytoplankton bloom in southern Lake Michigan that accounted for approximately 25% of the lake's annual gross offshore algal primary production. By combining the satellite imagery with in situ measurements of water temperature and wind velocity we show that the bloom was triggered by a brief wind event that was sufficient to cause substantial vertical mixing even though the lake was already stratified. We conclude that episodic events can have significant effects on the biological state of large lakes and should be included in biogeochemical process models.

  17. Summer depth distribution profiles of dissolved CO2 and O2 in shallow temperate lakes reveal trophic state and lake type specific differences.

    PubMed

    Laas, Alo; Cremona, Fabien; Meinson, Pille; Rõõm, Eva-Ingrid; Nõges, Tiina; Nõges, Peeter

    2016-10-01

    Knowledge about dissolved oxygen (DO) and carbon dioxide (CO2) distribution in lakes has increased considerably over the last decades. However, studies about high resolution dynamics of dissolved CO2 in different types of lakes over daily or weekly time scales are still very scarce. We measured summertime vertical DO and CO2 profiles at sub-hourly intervals during one week in eight Estonian lakes representing different lake types according to European Water Framework Directive. The lakes showed considerable differences in thermal stratification and vertical distribution of dissolved oxygen and CO2 as well as different diurnal dynamics over the measurement period. We observed a continuous CO2 supersaturation in the upper mixed layer of the alkalitrophic (calcareous groundwater-fed) lake and the dark soft-water lake showing them as CO2 emitting "chimneys" although with different underlying mechanisms. In three lake types strong undersaturation with CO2 occurred in the surface layer characterising them as CO2 sinks for the measurement period while in another three types the surface layer CO2 was mostly in equilibrium with the atmosphere. Factor analysis showed that DO% in the surface layer and the strength of its relationship with CO2% were positively related to alkalinity and negatively to trophic state and DOC gradients, whereas deeper lakes were characterised by higher surface concentration but smaller spatial and temporal variability of CO2. Multiple regression analysis revealed lake area, maximum depth and the light attenuation coefficient as variables affecting the largest number of gas regime indicators. We conclude that the trophic status of lakes in combination with type specific features such as morphometry, alkalinity and colour (DOC) determines the distribution and dynamics of dissolved CO2 and DO, which therefore may indicate functional differences in carbon cycling among lakes. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Stage fluctuations of Wisconsin lakes

    USGS Publications Warehouse

    House, Leo B.

    1985-01-01

    This report describes lake-stage fluctuations of 83 gaged lakes in Wisconsin and presents techniques for estimating stage fluctuation at ungaged lakes. Included are stage information at 83 lakes and stage-frequency data for 32 of these lakes that had sufficient record for analysis. Lakes are classified by a hydrologic-topographic lake classification scheme as ground-water flowthrough (GWF) lakes, surface-water drainage (SWD) lakes, and surface-water flow-through (SWF) lakes. Lakes within the same class were found to have similar water-level fluctuations. The lake-stage records indicate that most annual maximums occur during the months of May and June for all three classes. Annual minimum lake levels generally occur in September for surface-water drainage lakes, in March for surface-water flowthrough lakes, and in November for ground-water flow-through lakes. Data for each lake include location, period of water-level record, hydrologic classification, drainage area, surface area, lake volume, maximum depth, long-term mean stage and its standard deviation, maximum and minimum observed lake stage, and the average annual lake-stage fluctuation.

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

    USGS Publications Warehouse

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

    2007-01-01

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

  20. Salting our freshwater lakes.

    PubMed

    Dugan, Hilary A; Bartlett, Sarah L; Burke, Samantha M; Doubek, Jonathan P; Krivak-Tetley, Flora E; Skaff, Nicholas K; Summers, Jamie C; Farrell, Kaitlin J; McCullough, Ian M; Morales-Williams, Ana M; Roberts, Derek C; Ouyang, Zutao; Scordo, Facundo; Hanson, Paul C; Weathers, Kathleen C

    2017-04-10

    The highest densities of lakes on Earth are in north temperate ecosystems, where increasing urbanization and associated chloride runoff can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at broad spatial scales remains unknown, leading us to first identify spatial patterns and then investigate the drivers of these patterns. Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from 371 North American lakes. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization. Considering that 27% of large lakes in the United States have >1% impervious land cover around their perimeters, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L(-1)), stipulated by the US Environmental Protection Agency (EPA), in the next 50 y if current trends continue.

  1. Lake Balkhash, Kazakhstan

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This image of crescent-shaped Lake Balkhash was taken by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) on April 27, 2000. Lake Balkhash is located in eastern Kazakhstan, north of the Tian-Shan mountains. The Ili River flows into the western end of the lake, filling it with bright sediment. This sediment highlights the difference between the freshwater western side of the lake and the saline eastern side. A sandbar prevents mixing between the lake's two sections.Other features in this image include Lake Sayram in the lower right (southeast) corner, which is surrounded by the Borohoro Shan mountain range. At center right, just north of the Borohoro Shan, are lakes Sasykkol (left) and Alakol (right). The Karatal River flows northward through an arid and sandy landscape into the center of Lake Balkhash. The full-size image compares the region on April 27th image with one from the 18th. In that time sediments in lakes Balkhash and Sasykol increased noticeably, probably due to snowmelt-note the decrease in snowcover on the region's mountains. Also, the ice on Lake Sayram melted. These images were retrieved by the SeaWiFS high-resolution ground station in Mongolia, which recently began sending data to Goddard Space Flight Center. Image provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  2. Salting our freshwater lakes

    PubMed Central

    Bartlett, Sarah L.; Burke, Samantha M.; Doubek, Jonathan P.; Krivak-Tetley, Flora E.; Skaff, Nicholas K.; Summers, Jamie C.; Farrell, Kaitlin J.; McCullough, Ian M.; Morales-Williams, Ana M.; Roberts, Derek C.; Ouyang, Zutao; Scordo, Facundo; Hanson, Paul C.; Weathers, Kathleen C.

    201