Locations In Lake Research Articles

Paleoindian Colonization of the Americas: Implications from an Examination of Physiography, Demography, and Artifact Distribution

AbstractGIS-based, least-cost analyses employing continental scale elevation data, coupled with information on the late glacial location of ice sheets and pluvial lakes, suggest possible movement corridors used by initial human populations in colonizing the New World. These routes, demographic evidence, and the location of Paleoindian archaeological assemblages, support the possibility of a rapid spread and diversification of founding populations. Initial dispersal, these analyses suggest, would have been most likely in coastal and riverine settings, and on plains. The analyses suggest areas where evidence for early human settlement may be found in North and South America. In some cases, these areas have received little prior archaeological survey. The method can be used to explore patterns of human migration and interaction at a variety of geographic scales.

The Effect of Storage on Runoff from a Headwater Subarctic Shield Basin

Canadian Shield runoff production processes have been investigated, but research is needed beyond the hillslope scale to determine the influences on the volume and timing of runoff from headwater basins to higher-order streams. Such research will permit an understanding of the magnitude of climate change impacts at the watershed scale, where changes in the hydrologic regime are felt most by water resource users. To this end, water budget terms were measured over different portions of a headwater lake basin north of Yellowknife, Northwest Territories, during the spring snowmelt of 1998 to determine the relative importance of each component as water moved through the basin. Evaporation made up 16% and runoff 70% of the snowmelt from upland areas. Upland ponding of water during the melt increased the evaporative loss. Headwater lake storage deficits are very important in the timing and volume of runoff that is transmitted downstream: 53% of basin meltwater went to meeting the storage deficit in the lake so that only 7% of the meltwater was routed out of the basin. These results imply that topology of shield headwater basins, notably the location of lakes and antecedent water levels in lakes, are important in determining the runoff response. As storage deficits in surface waters will cause changes over space in runoff response and timing, it may be inappropriate to consider the snowpack or rainfall volume in isolation when forecasting runoff volume. These results are important for water management and hydrological modeling applications of northern shield basins.

Spatially Restricted Surveys over Time for Aquatic Resources

Consideration of the natural characteristics of aquatic resources and available frame material has led to the development of new designs for surveying large-scale regions. This paper illustrates survey designs developed to meet the requirements for surveying various aquatic resources, including a finite, discrete population, such as lakes within one or more states; a continuous linear population within a bounded area, such as wadeable streams within one or more states; and a continuous two-dimensional population within a bounded area, such as coastal waters associated with one or more states. We present a unified approach that addresses the differences of the aquatic resources assuming the availability of frame material, such as Geographic Information System (GIS) coverages of the boundary for coastal waters, stream network, and lake locations from U.S. Environmental Protection Agency's River Reach File 3, derived from U.S. Geological Survey digital line graph data from 1:100,000 scale maps. The basic design methodology distributes the sample over the spatial extent of the resource domain, and a panel structure can be used to extend the sample through time. Key features for the approach are (1) utilizing survey theory for continuous populations within a bounded area, (2) explicit control of the spatial dispersion of the sample, (3) variable spatial density, (4) nested subsampling, and (5) incorporating panel structures for sampling over time.

Isostatic rebound, active faulting, and potential geomorphic effects in the Lake Lahontan basin, Nevada and California

The high shoreline of the late Pleistocene (Sehoo) lake in the Lahontan basin is used as a passive strain marker to delineate the magnitude and character of regional deformation since 13 ka. The elevations of 170 high shoreline sites document that the once horizontal (equipotential) shoreline, which traverses almost 4° of latitude and 3° of longitude, is now deflected vertically about 22 m. Most of the deformation is attributed to isostatic rebound, but a small down-to-the-north regional tilting also appears to contribute to the overall deformation pattern. Active faults locally offset the high shoreline, but cannot explain the regional upwarping attributed to isostatic rebound since 13 ka. Preliminary models of the rebound yield an upper mantle viscosity of 10 18 Pa s that implies a Maxwell relaxation time of about 300 yr. The rapid Earth response, coupled with the rapid fall in lake level at the end of Pleistocene time, may have acted to divert some of the major rivers flowing into the basin from one terminal subbasin to another. The regional deformation caused by the rebound may also have acted to control the present location of Honey Lake. These shoreline data, therefore, support the potential for a link be

Bacterioplankton Community Diversity in a Series of Thermally Stratified Lakes.

> Abstract The dominant members of the bacterioplankton community in a set of 10 small, thermally stratified lakes in northeastern Indiana were determined by denaturing gradient gel electrophoresis (DGGE) of a polymerase chain reaction amplified fragment of 16S rDNA. The variability in community composition was analyzed as function of vertical stratification (epilimnion vs metalimnion), time (July vs August samples), and geographical location. In 58 discrete samples, a range of 8-23 bands were detected (mean = 14, s.d. = 4). For all variables, sample pairs shared about 40-70% of bands. In comparisons between depth strata, pairs of oxic samples shared more bands than an oxic-anoxic pair. There was no obvious relationship between the geographical location of lakes (or their physical connection) and band sharing.http://link.springer-ny.com/link/service/journals/00248/bibs/38n2p126.html

Lithological and biochemical properties in sediments of Lama Lake as indicators for the late Pleistocene and Holocene ecosystem development of the southern Taymyr Peninsula, Central Siberia

In order to evaluate the sensitivity of aquatic and terrestrial ecosystems to climatic changes, lithological (sediment structure and color, grain size, physical properties) and biochemical (TOC, TOC/TN, δ13C of TOC and carbonates) investigations were carried out on an 11.12 m‐long sediment core from Lama Lake (Central Siberia, Putorana Plateau). According to the pollen data, the sequence represents the termination of the Pleistocene, and the entire Holocene. It is composed of highly terrigenous and stratified clays and silts. Sediment structure, grain‐size distribution, carbonate contents and physical properties of the sediment indicate that glaciers were present in the catchment area of Lama Lake during the period Oldest Dryas to AllerØd. For the same time period, δ13C values of TOC give indications of a perennial ice cover. Since the AllerØd, organic matter accumulation has increased, caused by an increasing input of land vegetation and aquatic primary production as revealed by relations TOC contents, TOC/TN ratios and δ13C values of TOC. During the Holocene climatic optimum, in late Preboreal and Boreal times, biogenic primary production in Lama Lake reached its maximum and the vegetation in the catchment area changed from grassy tundra to a dense forest. From the Atlantic period to the present, small variations in δ13C values of TOC and TOC contents are probably related to the location of Lama Lake on the border between grass and wooded steppe, leading to responses of environmental conditions to even small changes in climate.

The carbon cycle and biogeochemical dynamics in lake sediments

The concentrations of organic carbon (OC) and CaCO 3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO 3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO 3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO 2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO 3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO 3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO 2 and accompanying increase in pH also may increase the production of CaCO 3 . However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO 3 and therefore a decrease in the rain rate of CaCO 3 to the sediment-water interface.

Comparative analysis of Lake Periphyton communities using high performance liquid chromatography (HPLC) and light microscope counts

High performance liquid chromatography (HPLC) and light microscope counts were used to characterize the taxonomic composition of epiphyton and epipelon at seven locations in a subtropical lake. Both methods indicated that algae were dominated by diatoms and cyanobacteria. However, the methods often gave dramatically different estimates of relative biomass among algal divisions, and there was no consistent pattern of co-variation. Large differences in underwater irradiance may have caused variation in accessory pigment to chlorophyll a ratios, invalidating application of the generic HPLC-based model. In large heterogeneous lakes, it may be necessary to use a suite of models, tailored to site-specific environmental conditions, if HPLC is to be used for evaluation of algal community structure.

Limitations of sediment quality surveys: a case study of an urban watershed in British Columbia, Canada

This case study of a 7200 ha. urban watershed illustrates the challenges involved in using sediment quality surveys to determine pollutant sources and trends. Trace metal and chlorinated hydrocarbon analyses were performed on sediment samples obtained from 33 stream, 24 street, and 1 lake (sediment core) locations. The stream and street sediment survey was initially conducted in 1973 and repeated in 1993. Consistent results across all sediment media indicate significant reductions in Pb, PCB, and DDT levels have occurred since the 1970's as a result of source controls. While streambed results indicate Hg and Mn levels have increased significantly since 1973, neither a spatial analysis of streambed results or a comparison to street concentrations indicate a source for the increase. A more detailed geo-chemical analysis and/or atmospheric contaminant survey may provide more conclusive source information.

WINTER SEVERITY AFFECTS MIGRATION AND CONTAMINANT ACCUMULATION IN NORTHERN GREAT LAKES HERRING GULLS

Herring Gull band returns were analyzed from 1962 to 1995. Winter severity was found to affect the winter distribution of Herring Gulls banded as flightless chicks on colonies in northern Lake Huron and northern Lake Michigan. The effects of winter severity were most pronounced in adults, followed by immatures. Little response was observed in juveniles. In adults, the proportion of band returns from southerly locations increased in response to increased winter severity. In general, concentrations of organochlorine contaminants in Herring Gull eggs collected annually from northern Great Lakes colonies increased with winter severity. However, the significance of the relationship between winter severity and organochlorine concentration was compound and colony specific. This probably reflected intercolony differences in winter migration patterns with concomitant differences in contaminant exposure during the overwintering period. With increased winter severity, gulls migrated to more contaminated southerly Great Lakes locations. After spending the winter in these areas the birds returned to their breeding colonies, transferring contaminants to their eggs. The degree to which Herring Gull eggs laid on colonies located in the northern Great Lakes reflect local contaminant bioavailability will be affected by winter severity and overwinter migration patterns.

Alternative strategies for reducing nitrogen loading

Two alternative strategies for reduction in nitrogen loading are analysed: (1) changes in agricultural production structure and (2) lake creation/restoration. The former includes spatial redistribution of the agricultural production, setting aside areas and changes in agricultural practice. The latter includes five scenarios with different lake location and size. A 342 km 2 agricultural watershed is used as study area. Two GIS-based models are applied: (1) a distributed riverine nitrogen loading model for analysis of agricultural changes and (2) a linked-lumped model for lake creation analysis. The analysis shows that each of the agricultural measures would result in a 11–13% reduction. In combination they would amount to 30% reduction. The five lake scenarios were giving area specific reductions varying from 46 to 2375 kg N ha −1 year −1. The best lake creation strategy seems to be a high number of smaller lakes distributed in all parts of the watershed. Results indicate that comprehensive lake creation would result in a 20–30% reduction. The results emphasise the need for integrated watershed management.

Determining basal ice-sheet conditions in the Dome C region of East Antarctica using satellite radar altimetry and airborne radio-echo sounding

AbstractLarge subglacial lakes manifest themselves as flat regions on the ice surface. ERS-1 satellite radar altimetry of the Dome C region of East Antarctica was analyzed to correlate unusually flat areas on the ice surface with known locations of subglacial lakes identified from airborne radio-echo sounding (RES) data. The mean length of subglacial lakes which have an expression in the ice-sheet surface was ~8.3 km, whilst those that did not exhibit a surface morphological manifestation had a mean length of ~3.3 km. Thus, lakes up to about 4 km in length arc unlikely to be detected from satellite radar altimetry of the ice surface. Given that the spacing of radio-echo flight tracks within the SPRI-NSF-TUD Antarctic database is 50-100 km in many areas, a number of subglacial lakes probably lie undetected beneath the ice sheet. RES information from two large, flat surface regions within Dome C, and a further flat area located at 80° S, 127° E, indicates the absence of subglacial lakes beneath the ice-surface features. However, these areas are characterised by relatively strong radio-echo returns which may indicate the presence of water-saturated basal sediments. We suggest that (1) blankets of water-saturated basal sediments may cause similar surface morphological features to those produced by subglacial lakes; and (2) misidentification of subglacial lakes from satellite altimeter observations of the ice-sheet surface is possible without the support of RES information relating to the ice-sheet base. Furthermore, our study indicates a lack of subglacial lake signals from RES data over relatively thick regions of East Antarctica such as the Adventure Subglacial Trough. We conclude that subglacial water produced in such regions may be transported by a basal hydrological system, driven by overburden pressure, to less thick regions of the ice sheet where subglacial lakes have been identified.

Determining basal ice-sheet conditions in the Dome C region of East Antarctica using satellite radar altimetry and airborne radio-echo sounding

AbstractLarge subglacial lakes manifest themselves as flat regions on the ice surface. ERS-1 satellite radar altimetry of the Dome C region of East Antarctica was analyzed to correlate unusually flat areas on the ice surface with known locations of subglacial lakes identified from airborne radio-echo sounding (RES) data. The mean length of subglacial lakes which have an expression in the ice-sheet surface was ~8.3 km, whilst those that did not exhibit a surface morphological manifestation had a mean length of ~3.3 km. Thus, lakes up to about 4 km in length arc unlikely to be detected from satellite radar altimetry of the ice surface. Given that the spacing of radio-echo flight tracks within the SPRI-NSF-TUD Antarctic database is 50-100 km in many areas, a number of subglacial lakes probably lie undetected beneath the ice sheet. RES information from two large, flat surface regions within Dome C, and a further flat area located at 80° S, 127° E, indicates the absence of subglacial lakes beneath the ice-surface features. However, these areas are characterised by relatively strong radio-echo returns which may indicate the presence of water-saturated basal sediments. We suggest that (1) blankets of water-saturated basal sediments may cause similar surface morphological features to those produced by subglacial lakes; and (2) misidentification of subglacial lakes from satellite altimeter observations of the ice-sheet surface is possible without the support of RES information relating to the ice-sheet base. Furthermore, our study indicates a lack of subglacial lake signals from RES data over relatively thick regions of East Antarctica such as the Adventure Subglacial Trough. We conclude that subglacial water produced in such regions may be transported by a basal hydrological system, driven by overburden pressure, to less thick regions of the ice sheet where subglacial lakes have been identified.

Limitations of sediment quality surveys: A case study of an urban watershed in British Columbia, Canada

This case study of a 7200 ha. urban watershed illustrates the challenges involved in using sediment quality surveys to determine pollutant sources and trends. Trace metal and chlorinated hydrocarbon analyses were performed on sediment samples obtained from 33 stream, 24 street, and 1 lake (sediment core) locations. The stream and street sediment survey was initially conducted in 1973 and repeated in 1993. Consistent results across all sediment media indicate significant reductions in Pb, PCB, and DDT levels have occurred since the 1970's as a result of source controls. While streambed results indicate Hg and Mn levels have increased significantly since 1973, neither a spatial analysis of streambed results or a comparison to street concentrations indicate a source for the increase. A more detailed geo-chemical analysis and/or atmospheric contaminant survey may provide more conclusive source information.

Analyses of Fish Species Richness with Spatial Covariate

Legislation passed in 1990 reducing the allowable sulfur dioxide emission levels in the United States is expected to reduce acidity in the Adirondack region of New York State. The number of fish species in a lake (species richness) depends on a number of physical and chemical factors, including the area, elevation, and acidity of the lake. Data on these and other factors are available for 1,166 Adirondack lakes. The data are analyzed with the goal of quantifying the effects of acid deposition on species richness after controlling for other important factors. A plot of the residuals from a standard multiple regression model against spatial location reveals a strong nonlinear relationship between species richness and lake location. With only one realization of the data, it is difficult, if not impossible, to tell whether this dependence should be modeled as deterministic spatial trend or as a spatial covariance structure. Two models are thus considered. The first is a multiple linear regression model with spatially correlated errors. As is common in geostatistics, it is assumed that the correlation between two errors is a function only of the vector separating the corresponding lakes. This is accomplished by modeling the correlation among the errors with a parametric variogram model. The parameters of the variogram are estimated via restricted maximum likelihood, after which the regression parameters are estimated using generalized least squares. The second model considered is a partial linear (or semiparametric) model containing a nonlinear term in spatial location. Locally weighted quadratic regression is used in conjunction with an estimation technique described by Speckman to estimate simultaneously the regression parameters and the “smooth” function of longitude and latitude. Finally, the ultimate goal of the 1990 legislation is a 50% reduction in sulfate deposition. Both models are used to form prediction intervals for species richness under that scenario. Extrapolation is avoided by using the criteria of Weisberg. The results suggest that a 50% reduction in sulfate deposition may result in a substantial increase in the fish species richness of many Adirondack lakes, particularly those with pH values between 4.5 and 6.5.

Convergent flow of ice within the Astrolabe subglacial basin, Trre Ad�lie, East Antarctica: an hypothesis derived from nummerical modelling experiments

The existence of a large subglacial lake beneath the antarctic Ice Sheet at Terre Adelie indicates the presence of basal ice at its pressure-melting temperature. A numerical model of the ice-sheet thermal regime is employed using the balance velocity of the ice sheet as an initial model input in order to calculate ice-sheet basal temperatures. However, the results from this model show the Terre Adelie area to be characterised by basal freezing. Heat in addition to that accounted for in the model is thus required at the ice-sheet base in order for pressure melting temperatures to be attained. The sources for such heat are (1) an enhanced geothermal heat flux and (2) an increase in frictional heating caused by the flow of ice. In this paper the latter possibility is expanded by hypothesising that subglacial topography induces convergent ice flow around Terre Adelie, causing enhanced basal ice velocities. Model experiments indicate that an increase in ice velocity (from 7 to at least 42 m yr?1) is required to raise the temperature of the basal ice to the pressure melting value. Increased ice velocity, and consequent frictional heat production due to convergent ice flow, may therefore be important in explaining the location of the subglacial lake in this region. These results allow the process of convergent ice flow within a contemporary ice sheet to be quantified. A verification (or otherwise) of the model results may be possible if ice surface velocity measurements from modem GPS methods are made.

Convergent flow of ice within the Astrolabe subglacial basin, Terre Adélie, East Antarctica: an hypothesis derived from numerical modelling experiments

The existence of a large subglacial lake beneath the antarctic Ice Sheet at Terre Adélie indicates the presence of basal ice at its pressure-melting temperature. A numerical model of the ice-sheet thermal regime is employed using the balance velocity of the ice sheet as an initial model input in order to calculate ice-sheet basal temperatures. However, the results from this model show the Terre Adélie area to be characterised by basal freezing. Heat in addition to that accounted for in the model is thus required at the ice-sheet base in order for pressure melting temperatures to be attained. The sources for such heat are (1) an enhanced geothermal heat flux and (2) an increase in frictional heating caused by the flow of ice. In this paper the latter possibility is expanded by hypothesising that subglacial topography induces convergent ice flow around Terre Adélie, causing enhanced basal ice velocities. Model experiments indicate that an increase in ice velocity (from 7 to at least 42 m yr?1) is required to raise the temperature of the basal ice to the pressure melting value. Increased ice velocity, and consequent frictional heat production due to convergent ice flow, may therefore be important in explaining the location of the subglacial lake in this region. These results allow the process of convergent ice flow within a contemporary ice sheet to be quantified. A verification (or otherwise) of the model results may be possible if ice surface velocity measurements from modem GPS methods are made.

An inventory of Antarctic sub-glacial lakes

An extensive analogue database of 60 MHz radio-echo sounding records of Antarctica (covering 50% of the ice sheet) is held at the Scott Polar Research Institute, University of Cambridge. This database was analysed in order to determine the presence and location of Antarctic sub-glacial lakes. In total, 77 sub-glacial lake-type records were identified, 13 more than detected in previous studies. An inventory of these sub-glacial lakes includes geographical coordinates, minimum length and overlying ice thickness for each lake. Information concerning the location of these lakes indicates that the majority (~70%) are found in the proximity of ice divides at Dome C and Ridge B within East Antarctica.

Development of population structure in Daphnia clones in a stratified lake

The frequencies of single locus genotypes (clones) in a natural population of Daphnia pulicaria in a Minnesota lake were estimated during five months when the lake was thermally stratified in 1991. Further samples were collected in early August 1990 and 1992. Daphnia pulicaria were aggregated during daytime in two layers detected with high-frequency sonar. One layer was in the metalimnion and upper hypolimnion (depth 10–15 m), the other deeper in the hypolimnion (18–22 m). The layers were sampled at two locations in Long Lake on eight dates in 1991. Cellulose acetate electrophoresis revealed four alleles at the phosphoglucose isomerase (PGI) locus. Three clones occurred with sufficient frequency in 3077 individuals for statistical analysis. The proportion of homozygous slow (SS) individuals increased with time in the deep layer at both locations, coincident with decreasing concentrations of dissolved oxygen, but was nearly constant in the shallower layer, where oxygen was near saturation. Analysis with log-linear statistics indicated that depth, date and the depth-date interaction were most important in explaining the variations in clone proportions during summer. Location and the date-location interaction, although significant, were less important. Data from early August 1990 and 1992 indicated that this pattern may be an annual phenomenon.

Development of population structure in Daphnia clones in a stratified lake

The frequencies of single locus genotypes (clones) in a natural population of Daphnia pulicaria in a Minnesota lake were estimated during five months when the lake was thermally stratified in 1991. Further samples were collected in early August 1990 and 1992. Daphnia pulicaria were aggregated during daytime in two layers detected with high-frequency sonar. One layer was in the metalimnion and upper hypolimnion (depth 10–15 m), the other deeper in the hypolimnion (18–22 m). The layers were sampled at two locations in Long Lake on eight dates in 1991. Cellulose acetate electrophoresis revealed four alleles at the phosphoglucose isomerase (PGI) locus. Three clones occurred with sufficient frequency in 3077 individuals for statistical analysis. The proportion of homozygous slow (SS) individuals increased with time in the deep layer at both locations, coincident with decreasing concentrations of dissolved oxygen, but was nearly constant in the shallower layer, where oxygen was near saturation. Analysis with log-linear statistics indicated that depth, date and the depth-date interaction were most important in explaining the variations in clone proportions during summer. Location and the date-location interaction, although significant, were less important. Data from early August 1990 and 1992 indicated that this pattern may be an annual phenomenon.