Lubbock Lake: Late Quaternary cultural and environmental change on the Southern High Plains,USA     

Eileen Johnson  Vance T. Holliday 《第四纪科学杂志》1989,4(2):145-165

Lubbock Lake (Southern High Plains of Texas) contains a cultural, faunal, and floral record within a virtually complete geological record spanning the past 11 100+ years. More than 88 archaeological occurrences have been excavated from five major stratigraphic units. The Paleoindian record (11 500–6500yr BP) begins with Clovis-age occupation (ca. 11 100yr BP) found within fluvial deposits (stratum 1). Subsequent Paleoindian occupations are found in lake and marsh sediments (stratum 2). Archaic occupations (8500-2000yr BP) are contained within aeolian and marsh deposits (strata 3 and 4). Ceramic occupations (2000-500yr BP) are found on a soil developed in stratum 4, in marsh sediments (strata 4 and 5), and in slopewash and aeolian sediments (stratum 5). The Protohistoric (500-300yr BP) and Historic (300-100yr BP) remains are in slopewash, aeolian, and marsh sediments (stratum 5) and associated soils. The Southern High Plains remained a grasslands throughout the last 11 500 years and neither man nor bison abandoned the region. The successive local faunas reflect changing ecosystems under pluvial to arid to more mesic to semiarid conditions. The occupation of Lubbock Lake through time appears to have been by small groups of people for both economic and short-term residential uses. These hunter-gatherer peoples underwent adaptive change brought about by climatic stress and alterations to food resources.  相似文献   

Seasonal variation in the biogeochemical cycling of seston in Grand Traverse Bay, Lake Michigan     

Eileen M. McCusker  Peggy H. Ostrom  Nathaniel E. Ostrom  Jeffery D. Jeremiason  Joel E. Baker 《Organic Geochemistry》1999,30(12):687

This study describes the biogeochemical cycling of seston in Grand Traverse Bay, Lake Michigan. Seston was characterized by carbon and nitrogen elemental and isotopic abundances. Fluorescence, temperature, light transmittance, and concentrations of dissolved inorganic nitrogen were also determined. PCBs were analyzed from surface (10 m) seston and ΣPCB was calculated by summing all of the congeners quantified in each sample. The vertical and seasonal trends in the δ¹³C values of seston exhibited a broad range from −30.7 to −23.9‰. Low δ¹³C values that occur concurrently with a peak in fluorescence below the thermocline reflect uptake of ¹³C depleted respiratory CO₂ and/or the accumulation of ¹³C depleted lipids by phytoplankton. High δ¹³C values late in the season likely result from a reduction in photosynthetic fractionation associated with a decrease in the CO₂ pool. Seasonal δ¹⁵N values of seston were high in the spring and declined through August. The δ¹⁵N values of seston reflect a balance between fractionation during assimilation of NH₄⁺ or NO₃⁻ and degradative processes. The seston ΣPCB and fluorescence were both high in the spring and subsequently declined, suggesting that the concentrations of PCBs in seston were associated with labile material derived from primary productivity. The strong seasonal trends in the organic geochemical characteristics of seston and concentrations of PCBs emphasize the complex nature of particle cycling in aquatic environments.  相似文献   

Investigating hydraulic connections and the origin of water in a mine tunnel using stable isotopes and hydrographs   总被引：1，自引：0，他引：1  

Katherine Walton-Day  Eileen Poeter 《Applied Geochemistry》2009

Turquoise Lake is a water-supply reservoir located north of the historic Sugarloaf Mining district near Leadville, Colorado, USA. Elevated water levels in the reservoir may increase flow of low-quality water from abandoned mine tunnels in the Sugarloaf District and degrade water quality downstream. The objective of this study was to understand the sources of water to Dinero mine drainage tunnel and evaluate whether or not there was a direct hydrologic connection between Dinero mine tunnel and Turquoise Lake from late 2002 to early 2008. This study utilized hydrograph data from nearby draining mine tunnels and the lake, and stable isotope (δ¹⁸O and δ²H) data from the lake, nearby draining mine tunnels, imported water, and springs to characterize water sources in the study area. Hydrograph results indicate that flow from the Dinero mine tunnel decreased 26% (2006) and 10% (2007) when lake elevation (above mean sea level) decreased below approximately 3004 m (approximately 9855 feet). Results of isotope analysis delineated two meteoric water lines in the study area. One line characterizes surface water and water imported to the study area from the western side of the Continental Divide. The other line characterizes groundwater including draining mine tunnels, springs, and seeps. Isotope mixing calculations indicate that water from Turquoise Lake or seasonal groundwater recharge from snowmelt represents approximately 10% or less of the water in Dinero mine tunnel. However, most of the water in Dinero mine tunnel is from deep groundwater having minimal isotopic variation. The asymmetric shape of the Dinero mine tunnel hydrograph may indicate that a limited mine pool exists behind a collapse in the tunnel and attenutates seasonal recharge. Alternatively, a conceptual model is presented (and supported with MODFLOW simulations) that is consistent with current and previous data collected in the study area, and illustrates how fluctuating lake levels change the local water-table elevation which can affect discharge from the Dinero mine tunnel without physical transfer of water between the two locations.  相似文献   

Differential modulation of eastern oyster (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) disease parasites by the El-Niño-Southern Oscillation and the North Atlantic Oscillation     

Thomas M. Soniat  Eileen E. Hofmann  John M. Klinck  Eric N. Powell 《International Journal of Earth Sciences》2009,98(1):99-114

The eastern oyster (Crassostrea virginica) is affected by two protozoan parasites, Perkinsus marinus which causes Dermo disease and Haplosporidium nelsoni which causes MSX (Multinucleated Sphere Unknown) disease. Both diseases are largely controlled by water temperature and salinity and thus are potentially sensitive to climate variations resulting from the El Niño-Southern Oscillation (ENSO), which influences climate along the Gulf of Mexico coast, and the North Atlantic Oscillation (NAO), which influences climate along the Atlantic coast of the United States. In this study, a 10-year time series of temperature and salinity and P. marinus infection intensity for a site in Louisiana on the Gulf of Mexico coast and a 52-year time series of air temperature and freshwater inflow and oyster mortality from Delaware Bay on the Atlantic coast of the United States were analyzed to determine patterns in disease and disease-induced mortality in C. virginica populations that resulted from ENSO and NAO climate variations. Wavelet analysis was used to decompose the environmental, disease infection intensity and oyster mortality time series into a time–frequency space to determine the dominant modes of variability and the time variability of the modes. For the Louisiana site, salinity and Dermo disease infection intensity are correlated at a periodicity of 4 years, which corresponds to ENSO. The influence of ENSO on Dermo disease along the Gulf of Mexico is through its effect on salinity, with high salinity, which occurs during the La Niña phase of ENSO at this location, favoring parasite proliferation. For the Delaware Bay site, the primary correlation was between temperature and oyster mortality, with a periodicity of 8 years, which corresponds to the NAO. Warmer temperatures, which occur during the positive phase of the NAO, favor the parasites causing increased oyster mortality. Thus, disease prevalence and intensity in C. virginica populations along the Gulf of Mexico coast is primarily regulated by salinity, whereas temperature regulates the disease process along the United States east coast. These results show that the response of an organism to climate variability in a region is not indicative of the response that will occur over the entire range of a particular species. This has important implications for management of marine resources, especially those that are commercially harvested.  相似文献   

Quantifying the effects of environmental change on an oyster population: A modeling study     

Margaret M. Dekshenieks  Eileen E. Hofmann  John M. Klinck  Eric N. Powell 《Estuaries and Coasts》2000,23(5):593-610

Three models are combined to investigate the effects of changes in environmental conditions on the population structure of the Eastern oyster,Crassostrea virginica. The first model, a time-dependent model of the oyster population as described in Powell et al. (1992, 1994, 1995a,b, 1996, 1997) and Hofmann et al. (1992, 1994, 1995), tracks the distribution, development, spawning, and mortality of sessile oyster populations. The second model, a time-dependent larval growth model as described in Dekshenieks et al. (1993), simulates larval growth and mortality. The final model, a finite element hydrodynamic model, simulates the circulation in Galveston Bay, Texas. The coupled post-settlement-larval model (the oyster model) runs within the finite element grid at locations that include known oyster reef habitats. The oyster model was first forced with 5 yr of mean environmental conditions to provide a reference simulation for Galveston Bay. Additional simulations considered the effects of long-term increases and decreases in freshwater inflow and temperature, as well as decreases in food concentration and total seston on Galveston Bay oyster populations. In general, the simulations show that salinity is the primary environmental factor controling the spatial extent of oyster distribution within the estuary. Results also indicate a need to consider all environmental factors when attempting to predict the response of oyster populations; it is the superposition of a combination of these factors that determines the state of the population. The results from this study allow predictions to be made concerning the effects of environmental change on the status of oyster populations, both within Galveston Bay and within other estuarine systems supporting oyster populations.  相似文献   

Fate of individual sewage disposal system wastewater within regolith in mountainous terrain     

Kathleen Dano  Eileen Poeter  Geoff Thyne 《Hydrogeology Journal》2008,16(4):691-699

In order to improve understanding of the fate of septic tank or individual sewage disposal system (ISDS) effluent in regolith overlying fractured-rock aquifers, effluent from an ISDS in such a setting was tracked via geophysical, hydrological, and geochemical methods. Under typical precipitation conditions, the effluent entered the fractured bedrock within 5 m of the boundary of the constructed infiltration area. During a period of unusually high spring recharge, the plume migrated between 50 and 100 m within the regolith before infiltrating the fractured bedrock. The chemical signature of the effluent is similar to that required to account for the decline in water quality, suggesting a causative relationship (as estimated from mass-balance models of the surface-water chemistry near the mouth of the basin). The elevated salt content of the effluent during periods of high natural recharge to the infiltration area correlates with elevated salt concentrations in surface and groundwater at the basin scale, suggesting that some of the effluent salt load may be stored in the unsaturated zone during dry periods and flushed during periods of elevated natural recharge.  相似文献   

Copepod colonization of natural and artificial substrates in a salt marsh pool     

Eileen Cummings  Ernest Ruber 《Estuarine, Coastal and Shelf Science》1987,25(6)

Pre-weighed packets of Spartina alterniflora and of plastic (polypropylene) twine were placed in a salt marsh pool and recovered on 40 dates spanning 14 months. New packets were placed out regularly to provide a contrast with ageing material. Twelve species of copepods were extracted, counted, and identified. Dry weight and Kjeldahl-nitrogen were determined for Spartina packets.Eight species of copepods, Amphiascus pallidus, Onychocamptus mohammed, Cletocamptus deitersei, Halicyclops sp., Harpacticus chelifer, Mesochra lilljeborgii, Metis jousseaumei and Nitocra sp. were found in higher densities on old grass or plastic packets than on new. The quantity of material was important in that the relative attractiveness of old grass was much lower early in the second year when 7–15% dw and 0·7% nitrogen remained than early in the first year when over 60% dw and 2·0% nitrogen remained. Old plastic polypropylene was equally or more attractive than old grass to 7 of 8 species, therefore, nitrogen decline in old grass was not the factor making it less attractive. Once aged, the quantity of substrate was more important than its quality. Apparently, this is due to colonization by microflora or settlement of detritus but these were not studied. The four clear exceptions to these trends were Darcythompsonia fairliensis and Eurytemora affinis which showed highest densities 72% and 50% of the time in new grass, Apocyclops spartinus with 70% in grass and equal numbers between old and new packets and Acartia tonsa a bay calanoid with 82% of highest densities in the water column and only two occurrences out of 40 dates in the packets.  相似文献   

Biogeochemical climatologies in the Ross Sea, Antarctica: seasonal patterns of nutrients and biomass     

Walker O. Smith  Jr.  Michael S. Dinniman  John M. Klinck  Eileen Hofmann 《Deep Sea Research Part II: Topical Studies in Oceanography》2003,50(22-26):3083

The seasonal patterns of nutrient (nitrate and silicic acid) and chlorophyll distributions in the Ross Sea are formulated by two independent methods. The first procedure compiles all available data from cruises from 1970 to the present and generates a three-dimensional grid for the months from November through February using an iterative difference-correction scheme. The second method uses a three-dimensional circulation model and the phytoplankton standing stock climatology to investigate the effects of currents and phytoplankton uptake on nutrient distributions. The two approaches produced similar results, although the circulation model produced distributions that were more variable in space due to its finer resolution. The nutrient distributions were characterized by elevated concentrations in early spring and gradual reductions to ca. 15 and 40 μM (nitrate and silicic acid, respectively) in summer. Nutrient depletion did not occur despite the favorable growth conditions (elevated macronutrient concentrations, strong vertical stratification) in summer, suggesting that an alternative limitation (such as by dissolved iron concentrations) occurs. Chlorophyll concentrations reached ca. 6 μg l⁻¹ in December and declined thereafter. Seasonal primary production calculated from the nitrate deficits and the circulation model suggested that production was ca. 73 g C m⁻², slightly lower but similar to other estimates using independent methods. Using the nutrient climatology, losses (vertical flux plus respiration) through Feb. 15 from the upper 100 m were ca. 50% of the seasonal production, and the rest of the organic production was removed after that date. Results also suggest that carbon export from the surface layer may vary significantly in space and time.  相似文献   

A circumpolar modeling study of habitat control of Antarctic krill (Euphausia superba) reproductive success     

Eileen E. Hofmann  Yusuf Sinan Hüsrevo lu 《Deep Sea Research Part II: Topical Studies in Oceanography》2003,50(22-26):3121

A one-dimensional, temperature-dependent model is implemented to simulate the descent–ascent cycle of Antarctic krill (Euphausia superba) embryos and larvae. Inputs to the model are monthly mean climatologies of ambient temperature and density fields obtained from the World Ocean Atlas Database for Southern Ocean waters. Simulations are done with a 1° resolution at a circumpolar scale, south of 60°S, and the results are interpolated to a 5′ grid to match the resolution of the bottom bathymetry data. Simulations of the descent–ascent cycle using environmental conditions corresponding to the Antarctic krill spawning season (December–March) resulted in unconstrained success in completion of the cycle in water deeper than 1000 m. Continental shelf regions favorable to successful hatching of Antarctic krill embryos are limited to areas along the west Antarctic Peninsula, large areas in the Bellingshausen and Amundsen Seas, offshore of Wilkes Land, and to the east and west of Prydz Bay. These are regions where the Southern Antarctic Circumpolar Current Front is along the shelf slope, the Antarctic Slope Front is absent, and Circumpolar Deep Water is present. The effect of seasonal variability in temperature on the descent–ascent cycle tends to enhance the probability of success in regions offshore of Wilkes Land, Queen Maud Land, and the eastern shelf of the Antarctic Peninsula later in the spawning season. The simulations show that success of the descent–ascent cycle is sensitive to initial embryo diameter and larval ascent rate. Initial embryo diameter may provide an additional constraint on success of the descent–ascent cycle, especially in continental shelf waters, where small embryos tend to encounter the bottom before hatching. The circumpolar distributions of simulated embryo hatching depth and larval success show that all regions of the Antarctic are not equal in the ability to support successful completion of the Antarctic krill descent–ascent cycle, which has implications for the overall circum-Antarctic krill distribution and for the development of nutrient and material budgets, especially for Antarctic continental shelf areas.  相似文献   

Spatial distribution of putative water related features in Southern Acidalia/Cydonia Mensae, Mars     

Eileen McGowan 《Icarus》2009,202(1):78-89

Many putative water-related features exist in the northern lowlands of Mars. These features may provide clues to the abundance and timing of water or ice that existed there in the past. The Cydonia Mensae and Southern Acidalia area was chosen as the study area owing to the abundance of two of these features: giant polygons and pitted cones. In addition a section of the Deuteronilus shoreline is located there. The abundance and close proximity of the features makes this area an excellent place to study the spatial relationships between these landforms, as well as the morphological characteristics of pitted cones. The features were mapped into a GIS for spatial analyses. The highest densities of pitted cones and giant polygons are adjacent but distinctly separated by a knobby ridge that is surrounded by the Deuteronilus putative shoreline. Pitted cones were measured and examined to determine if a classification by morphology is possible, but the results were inconclusive. Statistical tests on pit-to-cone diameter ratios and tests of surface temperatures of cone material suggest, but do not verify, a single cone origin. The various shapes, sizes, and putative ages of pitted cones may be attributed to temporal variation in emplacement and spatial variation in material properties. Among the possible scenarios put forth for pitted cone genesis on Mars two are likely candidates in Cydonia Mensae: (1) the sublimation of a cold-based glacier, and (2) a buried lens of methane and/or CO₂ clathrates.  相似文献