|
Hypolimnion
The hypolimnion or under lake is the dense, bottom layer of water in a thermally- stratified lake. The word " hypolimnion" is derived from . It is the layer that lies below the thermocline. Typically the hypolimnion is the coldest layer of a lake in summer, and the warmest layer during winter. In deep, temperate lakes, the bottom-most waters of the hypolimnion are typically close to 4 °C throughout the year. The hypolimnion may be much warmer in lakes at warmer latitudes. Being at depth, it is isolated from surface wind-mixing during summer, and usually receives insufficient irradiance (light) for photosynthesis to occur. Oxygen dynamics The deepest portions of the hypolimnion often have lower oxygen concentrations than the surface waters (i.e., epilimnion). While oxygen can typically exchange between surface waters and the atmosphere (i.e., in the absence of ice cover), bottom waters are comparatively isolated from atmospheric replenishment of oxygen. In particular, d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epilimnion
The epilimnion or surface layer is the top-most layer in a thermally stratified lake. The epilimnion is the layer that is most affected by sunlight, its thermal energy heating the surface, thereby making it warmer and less dense. As a result, the epilimnion sits above the deeper metalimnion and hypolimnion, which are colder and denser. Additionally, the epilimnion is typically has a higher pH and higher dissolved oxygen concentration than the hypolimnion. Physical Structure Properties In the water column, the epilimnion sits above all other layers. The epilimnion is only present in stratified lakes. On the topside of the epilimnion it is in contact with air, which leaves it open to wind action, which allows the water to experience turbulence. Turbulence and convection work together to make waves which increases aeration. On the bottom side of the epilimnion is the metalimnion, which contains the thermocline. The thermocline is created because of the difference in te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Stratification
Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers: the epilimnion, comprising the top warm layer; the thermocline (or metalimnion), the middle layer, whose depth may change throughout the day; and the colder hypolimnion, extending to the floor of the lake. Every lake has a set mixing regime that is influenced by lake morphometry and environmental conditions. However, changes to human influences in the form of land use change, increases in temperature, and changes to weather patterns have been shown to alter the timing and intensity of stratification in lakes around the globe. Rising air temperatures have the same effect on lake bodies as a physical shift in geographic location, with tropical zones being particularly sensitive. These changes can further alter the fish, zooplankton, and phytoplankton community composition, in addition to creating gradients that alter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypolimnetic Aeration
Deep-water aeration, also known as Hypolimnion, hypolimnetic aeration, describes the provision of oxygen from the atmosphere to meet oxygen demand in deep water without disrupting the natural Lake stratification, stratification of the water above. This process promotes the development of aerobic conditions in deep water, leading to a significant reduction in phosphate dissolution and an improvement in sediment Mineralization (soil science), mineralization. Scientific studies support the effectiveness of implementing technical ventilation measures to maintain year-round aerobic conditions in the deep water, thereby restoring the natural balance of lakes.Steinberg, C., Bernhardt, H.: Handbuch Angewandte Limnologie – 14. Erg.Lfg. 4/0 Verlag: Hüthig Jehle Rehm, 2002, . Eutrophication During summer stagnation in stratified, Trophic state index, eutrophic lakes, an oxygen deficit develops in the deep water. Increases in nutrient inputs raise the trophic level of these lakes. The nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Stratification (11)
A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although they may be connected with the ocean by rivers. Lakes, as with other bodies of water, are part of the water cycle, the processes by which water moves around the Earth. Most lakes are fresh water and account for almost all the world's surface freshwater, but some are salt lakes with salinities even higher than that of seawater. Lakes vary significantly in surface area and volume of water. Lakes are typically larger and deeper than ponds, which are also water-filled basins on land, although there are no official definitions or scientific criteria distinguishing the two. Lakes are also distinct from lagoons, which are generally shallow tidal pools dammed by sandbars or other material at coastal regions of oceans or lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Turnover
A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems (''lentic'' refers to stationary or relatively still freshwater, from the Latin ''lentus'', which means "sluggish"), which include ponds, lakes and wetlands, and much of this article applies to lentic ecosystems in general. Lentic ecosystems can be compared with lotic ecosystems, which involve flowing terrestrial waters such as rivers and streams. Together, these two ecosystems are examples of freshwater ecosystems. Lentic systems are diverse, ranging from a small, temporary rainwater pool a few inches deep to Lake Baikal, which has a maximum depth of 1642 m. The general distinction between pools/ponds and lakes is vague, but Brown states that ponds and pools have their entire bottom surfaces exposed to light, while lakes do not. In addition, some lakes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermocline
A thermocline (also known as the thermal layer or the metalimnion in lakes) is a distinct layer based on temperature within a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) with a high gradient of distinct temperature differences associated with depth. In the ocean, the thermocline divides the upper mixed layer from the calm deep water below. Depending largely on season, latitude, and turbulent mixing by wind, thermoclines may be a semi-permanent feature of the body of water in which they occur, or they may form temporarily in response to phenomena such as the radiative heating/cooling of surface water during the day/night. Factors that affect the depth and thickness of a thermocline include seasonal weather variations, latitude, and local environmental conditions, such as tides and currents. Oceans Most of the heat energy of the sunlight that strikes the Earth is absorbed in the first few centimeters at the ocean's surface, which hea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimictic Lake
A dimictic lake is a body of freshwater whose difference in temperature between surface and bottom layers becomes negligible twice per year, allowing all strata of the lake's water to circulate vertically. All dimictic lakes are also considered holomictic, a category which includes all lakes which mix one or more times per year. During winter, dimictic lakes are covered by a layer of ice, creating a cold layer at the surface, a slightly warmer layer beneath the ice, and a still-warmer unfrozen bottom layer, while during summer, the same temperature-derived density differences separate the warm surface waters (the epilimnion), from the colder bottom waters (the hypolimnion). In the spring and fall, these temperature differences briefly disappear, and the body of water overturns and circulates from top to bottom. Such lakes are common in mid-latitude regions with temperate climates. Examples of dimictic lakes * Lake Mendota * Lake Superior * Lake Simcoe * Lake Opeongo * Loch L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limnology
Limnology ( ; ) is the study of inland aquatic ecosystems. It includes aspects of the biological, chemical, physical, and geological characteristics of fresh and saline, natural and man-made bodies of water. This includes the study of lakes, reservoirs, ponds, rivers, springs, streams, wetlands, and groundwater.) Water systems are often categorized as either running ( lotic) or standing ( lentic). Limnology includes the study of the drainage basin, movement of water through the basin and biogeochemical changes that occur en route. A more recent sub-discipline of limnology, termed landscape limnology, studies, manages, and seeks to conserve these ecosystems using a landscape perspective, by explicitly examining connections between an aquatic ecosystem and its drainage basin. Recently, the need to understand global inland waters as part of the Earth system created a sub-discipline called global limnology. This approach considers processes in inland waters on a global scale, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anoxic Waters
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. Anoxic waters can be contrasted with hypoxic waters, which are low (but not lacking) in dissolved oxygen. Often, hypoxia is defined as waters that have less than 2 milligrams per litre of dissolved oxygen. This condition is generally found in areas that have restricted water exchange. In most cases, oxygen is prevented from reaching the deeper levels by a physical barrier, as well as by a pronounced density stratification, in which, for instance, denser, colder or hypersaline waters rest at the bottom of a basin. Anoxic conditions will occur if the rate of oxidation of organic matter by bacteria is greater than the supply of dissolved oxygen. Anoxic waters are a natural phenomenon, and have occurred throughout geological history. The Permia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
