9,271 research outputs found
Brown bullhead catfish (ameiurus nebulosus) in Lake Taupo
No full textBrown bullhead catfish (Ameiurus nebulosus) were first discovered in Lake Taupo during the early 1980s and are believed to have originated from an illegal liberation into the southern end of the lake. A native of the southern and eastern states of America, these catfish have been in New Zealand since 1878 and are now widespread throughout the Waikato region. In 1995 the population structure, abundance, age, growth rate and diet of catfish in the littoral zone (150 mm FL) and small fish. Low numbers of catfish across all size classes were caught from exposed sandy sites. The diet of catfish was size and habitat dependent. Small catfish (<150 mm FL) fed predominantly on chironomids, Cladocera, gastropods, caddisfly larvae, plant material and detritus. Larger catfish were found to prey to a greater extent on koura (Paranephrops planifrons), fish and terrestrial invertebrates
An illustrated historical atlas of Spencer County, Indiana : from actual surveys /
No full textReprint of the 1879 ed. published by D.J. Lake & Co., Philadelphia.Mode of access: Internet
Repeated Lake-Stream Divergence in Stickleback Life History within a Central European Lake Basin
Get PDFLife history divergence between populations inhabiting ecologically distinct habitats might be a potent source of reproductive isolation, but has received little attention in the context of speciation. We here test for life history divergence between threespine stickleback inhabiting Lake Constance (Central Europe) and multiple tributary streams. Otolith analysis shows that lake fish generally reproduce at two years of age, while their conspecifics in all streams have shifted to a primarily annual life cycle. This divergence is paralleled by a striking and consistent reduction in body size and fecundity in stream fish relative to lake fish. Stomach content analysis suggests that life history divergence might reflect a genetic or plastic response to pelagic versus benthic foraging modes in the lake and the streams. Microsatellite and mitochondrial markers further reveal that life history shifts in the different streams have occurred independently following the colonization by Lake Constance stickleback, and indicate the presence of strong barriers to gene flow across at least some of the lake-stream habitat transitions. Given that body size is known to strongly influence stickleback mating behavior, these barriers might well be related to life history divergence
A Later Summer Afternoon At Shongum Lake
No full textThere are three major parties at the lake each year. Memorial Day, The 4th of July, and Labor Day. These parties at the beach run from from 1:00 - 4:00pm. Games, a D.J., food and drinks are all available.Original file name SL 34 (1).jpe
Evaluating the influence of lake morphology, trophic status and diagenesis on geochemical profiles in lake sediments
No full textRecent geochemical studies provide evidence that changes in vertical distributions of nutrients in lake sediments are driven by anthropogenic activities, based primarily on trends of increasing concentrations in upper sediment layers. However, we show that vertical concentration profiles of carbon (C), nitrogen (N) and phosphorus (P) in lake sediments can be higher in the upper, most recently deposited sediment strata, driven largely by natural diagenetic processes and not eutrophication alone. We examined sediment cores from 14 different lakes in New Zealand and China ranging from oligotrophic to highly eutrophic and shallow to deep, and found that the shape of vertical profiles of total P, a key nutrient for lake productivity, can be similar in sediments across gradients of widely differing trophic status. We derived and applied empirical and mechanistic diagenesis steady state profile models to describe the vertical distribution of C, N and P in the sediments. These models, which focus on large scale temporal (decades) and spatial (up to 35 cm in the vertical) processes, revealed that density-differentiated burial and biodiffusive mixing, were strongly correlated with vertical concentration gradients of sediment C, N and P content, whereas lake trophic status was not. A sensitivity analysis of parameters included in the diagenetic model further showed that the processes including flux of organic matter to the sediment-water interface, burial (net sedimentation), breakdown of organic matter and biodiffusion all significantly can influence the vertical distribution of sediment P content. We conclude that geochemical studies attempting to evaluate drivers of the vertical distribution of sediment C, N, and P content in lake sediments should also account for the natural diagenetic drivers of vertical concentration gradients, assisted with application of similar models to those presented in this study. This would include quantification of key sediment diagenesis model parameters to separate out the influence of anthropogenic activities
Kentucky Bluegrass Seed Yield Response to Fertilizer, Rainfall, and Tempature in Roseau and Lake of the Woods Counties, Minnesota
No full text6 pages.Ruane, D.J.; Benson, F.J.. (1984). Kentucky Bluegrass Seed Yield Response to Fertilizer, Rainfall, and Tempature in Roseau and Lake of the Woods Counties, Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/112659
Physical environment, nutrient budget, and ecology of Lake Moana-nui, Tokoroa
No full textThis report is based on fortnightly monitoring data collected over a 14 month period from November 2000 to January 2002 and a survey of the lake bathymetry and vegetation distribution. The project also included a detailed investigation into the associations between macroinvertebrates and the native and exotic plants in the lake, and experiments evaluating the effects of the large populations of the water flea Simocephalus vetulus that the lake maintains on algal concentrations and therefore water clarity. The aim of this report is to present and discuss the results of the monitoring, surveys, and experiments in order to make recommendations for the future management and health of Lake Moana-nui
Restoration of Lake Hakanoa: Results of model simulations
No full textThis report was requested by Waikato District Council. It covers the lake water quality of, and possible restoration scenarios for, Lake Hakanoa a riverine lake situated in Huntly. The lake is used as a recreational resource by the community. In the past it has been reported to have had very poor water quality and is known to be eutrophic. It is currently in an algal-dominated, devegetated state and has low water clarity. The shallowness of this lake makes it potentially susceptible to resuspension of sediments through wind action. A community group, Friends of Hakanoa, has been responsible for the formation of a path around the perimeter of the lake, retiring about 3.6% of the catchment from pastoral farming and creating a riparian margin. Results from more recent reports and this report indicate a trend of improving water quality which may be related to recent restoration actions such as re-establishment of a riparian margin
Lake Diatoms as a Proxy for Holocene Environmental Change, West Greenland
Get PDFThere is great interest over the Greenland Ice Sheet in terms of future climate change, though there is a lack of understanding of climate change during the Holocene. Lakes can provide continuous and detailed records of paleoclimate; the distinct taxonomy and preservation potential of diatoms makes them a particularly useful proxy within paleoenvironmental reconstructions. Contemporary diatom assemblages and the environmental conditions of 25 lakes from a localized area in the Godthåbsfjord region, southwest Greenland, as well as a fossil core from one of the lakes, are studied. Multivariate analysis is undertaken to establish the relationships between the contemporary diatoms and environmental conditions, and the addition of another dataset from Søndre Strømfjord, west Greenland, provided an insight into lake and diatom variability. Transfer functions are then developed for several environmental variables, including pH, temperature and lake depth, and applied to the fossil diatom assemblages from the lake core. The fossil diatom assemblages and quantitative reconstructions indicate an acidification of the lake through the Holocene, and the quantitative reconstructions, along with additional proxy data of pollen, provide a record of several warming and cooling phases through the Holocene, including the Little Ice Age. There are however several issues, including multiple forcing variables acting on the contemporary diatoms, the provision of modern analogues for the fossil assemblages, as well as preservation problems, that raise several questions over the reliability of lake diatoms as a proxy for Holocene environmental change in southwest Greenland
Numerical modeling of hydrodynamic circulation in Lake Taihu
No full textThis study is aiming to improve the understanding of hydrodynamic circulation in large shallow lakes. The Lake Taihu, the third largest lake in east China, is picked up as the study area for three reasons. The basin of Lake Taihu is considered as the most populated and developed area as a backyard of Shanghai. Lake Taihu is a typical shallow lake with average water depth of 1.9m. The lake is suffering from severe ecological problems during the past 20 years caused by the growing industrial, agricultural and urban waste water. Literature review showed that in the previous researches over the Lake Taihu, more emphasize was put on resulting concentration of contaminants and nutrients in the water while the hydrodynamic circulation are less quantitatively focused. In this study, hydrodynamic circulation indices are applied to quantify hydrodynamic circulation in Lake Taihu. This study has been carried out through various empirical modeling, schematized modeling and complete 3d modeling approach. To quantify the water circulation and water exchange in the lake, hydrodynamic circulation indices, such as water age and residence time, are introduced. To evaluate the hydrodynamic circulation indices, a simple schematized model is first set up and analyzed to demonstrate the functions and characteristics of different circulation indices. Model input data such as water level, inflow/outflow discharge (mass balance), and land reclamation are analyzed. Since the wind is generally regarded as the driving force for shallow lakes, wind input data is emphasized and corrected for land-measured data. The contribution of different conditions, including various wind conditions, to the water exchange between the lake water and water body discharged from the canals, is evaluated. Then a three-dimensional hydrodynamic model for Lake Taihu is set up and has been calibrated with water level data of year 2008. The three-dimensional hydrodynamic model is used to demonstrate the hydrodynamic circulation pattern in Lake Taihu. Sensitivity tests on the input data and physical parameters shows that the discharge is the most important factor if the wind is not driven force under normal wind conditions. Innovative engineering measurements and design scenarios are proposed to enhance the water circulation, which will potentially promote the water quality in certain subzones of the lake. These design scenarios, including recovery of land reclamation, global dredging, local barrier, local trenches and submerged reef, are investigated. It is found that, although the anthropogenic changes on bed don’t provide global improvement in circulation indices, local improvement is generally observed in subzones of the lake. Furthermore, wave effects are assessed via an empirical nomogram model, a schematized model and a wave model for the Lake Taihu. Results and analysis show that wave effects are not significant for Lake Taihu under normal wind conditions. This study applies hydrodynamic circulation indices to quantify the circulation in Lake Taihu, thus to improve the understanding the hydrodynamic circulation pattern in the lake. This approach could be extended to the hydrodynamic studies in similar large, shallow lakes. The modeling tools are essential for further environmental, biological and ecological study. They are also quantitative tools to assess anthropogenic effects on large shallow lakes for researchers, managers and stakeholders.Coastal EngineeringHydraulic EngineeringCivil Engineering and Geoscience
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