53 articles
Lake acidification
Lake acidification is the process by which a lake's water becomes more acidic, caused mainly by acid rain and acid mine drainage. It killed fish in Scandinavian and North American lakes in the 1970s and 1980s.
Lake stratification
Lake stratification, or thermal stratification, is the layering of a lake's water by density, typically into a warm epilimnion, a cold hypolimnion, and a thermocline between.
Maximum density of water
The maximum density of water occurs near 3.98 °C at standard atmospheric pressure, so water expands as it cools further, letting lakes freeze from the top down.
Meromixis
Meromixis is the condition of a lake in which the water column never fully mixes, leaving dense bottom water permanently unmixed; the term was coined in 1935 by limnologist Ingo Findenegg.
Mixing regime
A mixing regime is the annual pattern of vertical mixing and thermal stratification in a lake, classified by how often and how completely its water circulates each year.
Net ecosystem production
Net ecosystem production (NEP) is the difference between gross primary production and ecosystem respiration in an ecosystem, commonly measured in lakes with the diel oxygen technique.
Nitrogen limitation
Nitrogen limitation is the restriction of phytoplankton growth in a lake by available nitrogen rather than phosphorus; the Lake 227 experiment showed nitrogen-fixing cyanobacteria compensate when nitrogen inputs cease.
Oligotrophication
Oligotrophication, also called re-oligotrophication, is the decline of nutrient concentrations and productivity in an aquatic ecosystem, most often a deliberate result of cutting nitrogen and phosphorus inputs to a formerly eutrophic lake.
Penetrative convection
Penetrative convection is a form of turbulent convection in which surface cooling drives plumes that overshoot into stratified water below, entraining it and deepening a lake's mixed layer.
Phosphorus limitation
Phosphorus limitation is the control of biological production by phosphorus supply, the principle that phosphorus, not nitrogen or carbon, governs algal blooms and eutrophication in lakes.
Phosphorus loading
Phosphorus loading is the quantity of phosphorus delivered to a water body per unit time, either from the watershed and atmosphere or released from lake sediments.
Redoxcline
A redoxcline is the layer in a lake or basin where redox conditions change sharply with depth, separating oxygenated water above from anoxic water or sediment below.
Rock flour
Rock flour, also called glacial flour or glacier milk (French farine glaciaire), is fine silt-size sediment produced by glaciers grinding bedrock, which turns meltwater streams milky white.
Salt lake
A salt lake, also called a saline or brine lake, is a closed-basin lake whose water exceeds about 3 g/L dissolved salt, typically forming in arid basins where evaporation concentrates minerals.
Sediment resuspension
Sediment resuspension is the mobilization of settled bed sediment back into the water column when bottom shear stress exceeds a critical value, driven mainly by wind, waves, and currents.
Shrinkage of Lake Chad
The shrinkage of Lake Chad is the loss of about 90 percent of the lake's surface area from the 1960s to the 1990s, with recent refilling since 2000.
Soluble reactive phosphorus
Soluble reactive phosphorus (SRP), also called molybdate reactive phosphorus or dissolved reactive phosphorus, is a filtered phosphorus measurement used in limnology as an estimate of phosphate available to algae.
Top-down control
Top-down control is the regulation of a food web by predators and grazers, notably zooplankton grazing on phytoplankton in lakes, contrasted with bottom-up nutrient control.
Total nitrogen
Total nitrogen (TN) is the sum of all forms of nitrogen in a water sample, including nitrate, nitrite, ammonia, and organic nitrogen, and a core indicator in lake monitoring.
Total phosphorus
Total phosphorus (TP) is a water-quality measurement of all phosphorus in a water sample regardless of chemical form, obtained by converting every phosphorus compound to orthophosphate before analysis.
Trophic state index
The trophic state index, also known as Carlson's Trophic State Index, is a 0 to 100 scale classifying lake productivity, developed by Robert E. Carlson in 1977.
Wind-driven circulation
Wind-driven circulation is the water motion generated when wind stress acts on a lake or sea surface, organizing currents, gyres, and waves, and usually the main flow-generating mechanism in lakes.
Zooplankton grazing
Zooplankton grazing is the consumption of phytoplankton and bacteria by planktonic animals, one of two principal controls on algal biomass, shaping water clarity and bloom dynamics.