|Primary inflows||Kissimmee River, Fisheating Creek, Taylor Creek|
|Primary outflows||Everglades, Caloosahatchee River, St. Lucie River|
|Basin countries||United States|
|Max. length||36 mi (57.5 km)|
|Max. width||29 mi (46.6 km)|
|Surface area||734 sq mi (1,900 km2)|
|Average depth||8 ft 10 in (2.7 m)|
|Max. depth||12 ft (3.7 m)|
|Water volume||1 cu mi (5.2 km3) (estimated)|
|Residence time||3 years|
|Surface elevation||12 to 18 ft (3.74 to 5.49 m)|
|Islands||Kreamer, Torry, Ritta, Grass, Observation, Bird, Horse, Hog, Eagle Bay|
Lake Okeechobee ( US: // ), also known as Florida's Inland Sea, is the largest freshwater lake in the U.S. state of Florida. It is the tenth largest natural freshwater lake among the 50 states of the United States and the second-largest natural freshwater lake contained entirely within the contiguous 48 states, after Lake Michigan.
Okeechobee covers 730 square miles (1,900 km2) and is exceptionally shallow for a lake of its size, with an average depth of only 9 feet (2.7 metres). It is not only the largest lake in Florida or the largest lake in the southeast United States, but it is too large to see across, giving it the feel of an ocean. The Kissimmee River, located directly north of Lake Okeechobee, is the lake's primary source. The lake is divided between Glades, Okeechobee, Martin, Palm Beach and Hendry counties. All five counties meet at one point near the center of the lake.
The earliest recorded people to have lived around the lake were the Calusa. They called the lake Mayaimi, meaning "big water," as reported in the 16th century, by Hernando de Escalante Fontaneda.The name Okeechobee comes from the Hitchiti words oki (water) and chubi (big). Slightly later in the 16th century, René Goulaine de Laudonnière reported hearing about a large freshwater lake in southern Florida called Serrope. By the 18th century the largely mythical lake was known to British mapmakers and chroniclers by the Spanish name Laguna de Espiritu Santo. In the early 19th century it was known as Mayacco Lake or Lake Mayaca after the Mayaca people, originally from the upper reaches of the St. Johns River, who moved near the lake in the early 18th century. The modern Port Mayaca on the east side of the lake preserves that name.
On the southern rim of Lake Okeechobee, three islands—Kreamer, Ritta, and Torey—were once settled by early pioneers. These settlements had a general store, post office, school, and town elections. Farming was the main vocation. The fertile land was challenging to farm because of the muddy muck. Over the first half of the twentieth century, farmers used agricultural tools—including tractors—to farm in the muck. By the 1960s, all of these settlements were abandoned.
All of Lake Okeechobee was included in the boundaries of Palm Beach County when it was created in 1909. In 1963, the lake was divided among the five counties surrounding the lake.
In 1926, the Great Miami Hurricane hit the Lake Okeechobee area, killing approximately 300 people. Two years later in 1928, the Okeechobee Hurricane crossed over the lake, killing thousands. The Red Cross reported 1,836 deaths, a figure which the National Weather Service initially accepted, but in 2003, the number was revised to "at least 2,500". 6.6-foot (2-meter) mud dike that circled the lake at the time. After the two hurricanes, the Florida State Legislature created the "Okeechobee Flood Control District".[ citation needed ]In both cases the catastrophe was caused by flooding from a storm surge when strong winds drove water over the
The organization was authorized to cooperate with the U.S. Army Corps of Engineers in actions to prevent similar disasters. U.S. President Herbert Hoover visited the area personally, and afterward the Corps designed a plan incorporating the construction of channels, gates, and nearly 140 miles of levees to protect areas surrounding Lake Okeechobee from overflow.
The Okeechobee Waterway was officially opened on March 23, 1937, by a procession of boats which left Fort Myers, Florida on March 22 and arrived at Stuart, Florida the following day. The dike was then named the "Herbert Hoover Dike" in honor of the president.[ citation needed ]
The 1947 Fort Lauderdale Hurricane sent an even larger storm surge to the crest of the new dike, which was expanded again in the 1960s.[ citation needed ]
Four recent hurricanes – Frances, Jeanne, Wilma, and Irma – had no major adverse effects on communities surrounding Lake Okeechobee, even though the lake rose 18 inches (46 cm) after Hurricane Wilma in 2005. Tropical Storm Ernesto increased water levels by 1 foot (30 cm) in 2006, the last time it exceeded 13 feet (4.0 m). However, the lake's level began dropping soon after and by July 2007, it had dropped more than 4 feet (1.2 m) to its all-time low of 8.82 feet (2.69 m). In August 2008, Tropical Storm Fay increased water levels to 2 feet (0.65 m) above sea level, the first time it exceeded 12 feet (3.66 m) since January 2007. Over a seven-day period (including some storms that preceded Fay), about 8 inches (20 cm) of rain fell directly onto the lake.
During construction of the dike, earth was excavated along the inside perimeter, resulting in a deep channel which runs along the perimeter of the lake. [ citation needed ]This channel is known as the rim canal. In most places the canal is part of the lake, but in others it is separated from the open lake by low grassy islands such as Kreamer Island. During the drought of 2007–2008, this canal remained navigable while much of surrounding areas were too shallow or even above the water line. Even when the waters are higher, navigating the open lake can be difficult, whereas the rim canal is easier, so to reach a specific location in the lake it is often easiest to use the rim canal to get close then take one of the many channels into the lake.
In 2007, during a drought, state water and wildlife managers removed thousands of truckloads of toxic mud from the lake's floor, in an effort to restore the lake's natural sandy base and create clearer water and better habitat for wildlife. The mud contained elevated levels of arsenic and other pesticides. According to tests from the South Florida Water Management District, arsenic levels on the northern part of the lake bed were as much as four times the limit for residential land. Independent tests found the mud too polluted for use on agricultural or commercial lands, and therefore difficult to dispose of on land.
Through early 2008, the lake remained well below normal levels, with large portions of the lake bed exposed above the water line. During this time, portions of the lake bed, covered in organic matter, dried out and caught fire. 4 feet (1.2 m) increase in water level, including local run-off from the tributaries.In late August 2008, Tropical Storm Fay inundated Florida with record amounts of rain. Lake Okeechobee received almost a
In 2013, heavy rains in central Florida resulted in high runoff into the lake; rising lake levels forced the CoE (Army Corps of Engineers) to release large volumes of polluted water from the lake through the St. Lucie River estuary to the east and the Caloosahatchee River estuary to the west. Thus the normal mix of fresh and salt water in those estuaries was replaced by a flood of polluted fresh water resulting in ecological damage.
Since 2013, the CoE has been forced to pump billions of gallons of water out of the lake to avoid jeopardizing the integrity of the Hoover dike holding back the water from inundating the surrounding populated area. Some claim that sugar plantations have been pumping polluted water from their flooded fields into the lake, but U.S. Sugar claims back pumping is only to avoid flooding of communities, never to protect farmland. In March 2015, the rate was 1 billion US gallons (3,800,000 m3) daily. This results in pollution problems for the Treasure Coast, St. Lucie estuary, and the Indian River Lagoon.
In May 2016, 33 square miles (85 km2) of the southern portion of the lake were affected by an algal bloom. The outbreak was possibly due in part to nutrient-laden waters reaching the lake from farms and other sources. Microcystin was found among the other species involved in the outbreak.
In July 2016, the Federal Government denied Governor Rick Scott's request for Federal Disaster Aid to the Treasure Coast as a result of the toxic algal bloom in the St. Lucie Estuary which was responsible for millions of dollars of lost income for local businesses: this reaffirmed the Federal Emergency Management Agency (FEMA) finding that the lake's water quality was a State issue. The Florida Department of Environmental Protection and Martin County had carried out toxicity testing on the algae, but had not funded any work to clean up the water, and a FEMA spokesman said that "The state has robust capability to respond to emergencies and disasters."
On June 23, 2017, the South Florida Water Management District was granted emergency permission to back pump clean water into Lake Okeechobee to save animals and plants in bloated water conservation areas."
Lake Okeechobee sits in a shallow geological trough that also underlies the Kissimmee River Valley and the Everglades. The trough is underlain by clay deposits that compacted more than the limestone and sand deposits did along both coasts of peninsular Florida. Until about 6,000 years ago, the trough was dry land. As the sea level rose, the water table in Florida also rose and rainfall increased. From 6,000 to 4,000 years ago, wetlands formed building up peat deposits. Eventually the water flow into the area created a lake, drowning the wetlands. Along what is now the southern edge of the lake, the wetlands built up the layers of peat rapidly enough (reaching 13-to-14-foot or 4-to-4.3-metre thick) to form a dam, until the lake overflowed into the Everglades. At its capacity, the lake holds 1 trillion US gallons (3.8×109 m3) of water and is the headwaters of the Everglades.
The floor of the lake is a limestone basin, with a maximum depth of 13 feet (4 m). Its water is somewhat murky from runoff from surrounding farmlands. The Army Corps of Engineers targets keeping the surface of the lake between 12.5 and 15.5 feet (4 and 5 m) above sea level. The lake is enclosed by a 40 feet (12 m) high Herbert Hoover Dike built by the U.S. Army Corps of Engineers after a hurricane in 1928 breached the old dike, flooding surrounding communities and claiming at least 2,500 lives. Water flows into Lake Okeechobee from several sources, including the Kissimmee River, Fisheating Creek, Lake Istokpoga, Taylor Creek, and smaller sources such as Nubbin Slough and Nicodemus Slough. The Kissimmee River is the largest source, providing more than 60% of the water flowing into Lake Okeechobee. Fisheating Creek is the second largest source for the lake, with about 9% of the total inflow. Prior to the 20th century, Lake Istokpoga was connected to the Kissimmee River by Istokpoga Creek, but during the rainy season Lake Istokpoga overflowed, with the water flowing in a 40 km wide sheet across the Indian Prairie into Lake Okeechobee. Today Lake Istokpoga drains into Lake Okeechobee through several canals that drain the Indian Prairie, and into the Kissimmee River through a canal that has replaced Istokpoga Creek. Historically, outflow from the lake was by sheet flow over the Everglades, but most of the outflow has been diverted to dredged canals connecting to coastal rivers, such as the Miami Canal to the Miami River, the New River on the east, and the Caloosahatchee River (via the Caloosahatchee Canal and Lake Hicpochee) on the southwest.
According to the U.S. Army Corps of Engineers,the congressionally authorized uses for Lake Okeechobee include the following:
The 30-metre (100 ft) wide dike surrounding Lake Okeechobee is the basis for the Lake Okeechobee Scenic Trail (LOST), a part of the Florida National Scenic Trail, a 1,300-mile-long (2,100 km) trail. There is a well-maintained paved pathway along the majority of the perimeter, although with significant breaks. It is used by hikers and bicyclists, and is wide enough to accommodate vehicles.
The most common fish in this lake are largemouth bass, crappie, and bluegill. Pickerel have been less commonly caught.
This shallow lake has been previously studied for its algal blooms. Lake Okeechobee is known for its algal blooms in consequence of increased eutrophication. Algal blooms like this can be harmful to the environment, including the lake's flora and fauna, because of released toxins. The vegetation at Lake Okeechobee is important in maintaining the oxygen in the lake, of which many aquatic biota are reliant on. There are various species of biota in Lake Okeechobee that are interdependent on each other for food, habitat, and other resources. Multiple limnological studies and related research has been conducted at Lake Okeechobee.
Lake Okeechobee is shallow lake, with an average depth of only 3 meters, km. In total, the lake has a surface area of 1730 km². The lake is normally mixed, but on days with direct sunlight and limited wind, the lake can exhibit diurnal thermal stratification. Although daily thermal stratification is brief, a hypolimnion can form during this time resulting in decreased amounts of dissolved oxygen at the lake bottom. Lake transparency, measured as secchi depth, is found to be inversely correlated with the amount of suspended solids in the lake. Suspended solids varied with season with higher amounts of suspended solids in the winter, and thus less transparency on average, and lower amounts of suspended solids in the summer, leading to more transparency on average. Secchi depths not only varied across seasons, but also by location in the lake. Secchi depths ranges average from about 0.2 – 0.5 meters in the winter, depending on location in the lake, and 0.3 – 0.9 meters in the summer. Secchi depths of 1.7 meters have been recorded, indicating higher transparencies than average for the lake.and has a fetch of 54
Lake Okeechobee is home to more than 40 species of native fish,along with introduced species, such as the Mayan cichlid, Cichlasoma urophthalmus. Fish species displaying varying distributions throughout the lake depending on seasonality, site depth, sediments, and turbidity. Yearly fish recruitment was found to be positively correlated with increased water levels, providing more substrate and protection. These fish populations support different wading birds, including various species of egrets, ibises, wood storks, and herons, along with alligator populations. Fish diets in Lake Okeechobee depend on macro-invertebrates and zooplankton, such as calanoids, cyclopoids, and cladoceran. Lake Okeechobee supports over 3,800 different arthropods, including insects and arachnids, along with around 400 species of nematodes.
Vascular macrophytes are important in the nutrient dynamics of lakes, along with creating micro-habitats for fish and invertebrates, and providing substrate for epiphytes. Macrophytes provide the lake with oxygen through photosynthesis, along with acting as a buffer for eutrophication by uptake of phosphorus. However, with increased eutrophication of lakes along with climate change, trends are showing decreased richness of macrophytes. Because the fauna are so reliant on the macrophytes for habitat, food, and protection from predation, a decrease in macrophyte diversity and abundance has negative consequences on fauna richness.Macrophyte abundance is dependent on many abiotic factors such as water depth, water transparency and light availability, and nutrients, along with influence of biotic factors. Increasing phytoplankton and algal blooms from eutrophication and nutrient abundance can decrease water transparency and light availability to submerged macrophytes, providing one explanation how macrophytes are sensitive to eutrophication. Some submerged macrophytes that have been recorded at Lake Okeechobee include southern naiad (Najas guadelupensis), Illinois pondweed (Potamogeton illlinoensis), vallisneria (Vallisneria americana), and hydrilla (Hydrilla verticillata). Lake Okeechobee is afflicted with the invasive terrestrial plant, torpedograss (Panicum repens).
The concerning levels of total phosphorus (TP) began to be noticed in 1970s, and since then inputs of TP have averaged 516 tons per year.These yearly inputs can vary based on the volume of runoff entering the lake. The years 2005 and 2018 had particularly large volumes of water and TP inputs in relation to hurricanes increasing runoff. Despite limiting TP inputs by decreasing phosphorus use in agriculture, Lake Okeechobee has yet to be reach the aimed target set by the South Florida Water Management District's in the 1980s of reducing the lake's TP by 40 μg/L. Although proposed by the South Florida Water Management District, this initiative of limiting the lake's TP to 40 μg/L was adopted by The Lake Okeechobee Technical Advisory Committee (LOTAC), the United States Environmental Protection Agency (USEPA), and the Florida Department of Environmental Protection (FDEP), but phosphorus inputs have yet to be controlled enough to reach this goal. Concerning estimates of phosphorus assimilation capacity indicates that even if phosphorus inputs were to be stopped, or severely limited, the extensive saturation of the lake would result in it taking years before improved water quality can be observed.
These inputs of phosphorus provide optimal conditions for harmful algal blooms (HABs). Cyanobacteria (CyanoHABs), which need nitrogen and phosphorus for growth, have the ability to fix atmospheric nitrogen. With this ability along with the high inputs of phosphorus, the shallow nature of the lake providing plenty of sunlight, and cyanobacteria's preference for warm waters, Lake Okeechobee is an optimal environment for a cyanobacteria algal bloom. The presence of various species of cyanobacteria in Lake Okeechobee have been recorded since the 1980s. Cyanobacteria produce various toxins, including microcystin, which is not only harmful to the environment, but humans.In 2016, Lake Okeechobee experienced an extensive cyanobacteria algal bloom that lasted from May to mid-July. During the previous 2015–16 winter, there were relatively high recorded temperatures, and higher than average rates of precipitation and storms in relation to the El Niño event. As mentioned, higher rates of precipitation can lead to greater influxes of runoff which unload more phosphorus into the lake, enabling harmful algal bloom. Along with this algal bloom in 2016, other algal blooms have been found to occur in relation to hurricanes and other climate events leading to increased water flow into the lake.
Research done by James et al. (2009) aimed to evaluate and compare shallow lakes, including Lake Okeechobee and Lake Taihu in P.R. China, including their light, temperature, and nutrient dynamics. This research provides important knowledge on conditions that influence algal blooms. They found that for both lakes, wind, nutrients, water depth, and water transparency varied seasonally, and this had implications on phytoplankton abundance. Different locations in the lake may have had different limiting factors based on the light and nutrient availability in those locations. At Lake Okeechobee specifically, algal blooms were found to have strong effects during the winter on the western side of the lake.
In the limnological study conducted by Beaver et al. (2013) at Lake Okeechobee, lake phytoplankton composition was examined in response to conditions of anthropogenic inputs, including nutrient inputs, along with natural events, like extreme weather conditions. Lake Okeechobee was a great location for this study because of its long history of agricultural runoff causing algal blooms, along with its location in the Gulf of Mexico making it susceptible to weather events like tropical storms and hurricanes. From 2000–2008, phytoplankton samples were collected using an integrated tube sampler, and weather conditions, including temperature and wind conditions, were recorded. They found that phytoplankton composition transitioned from non-nitrogen fixing cyanobacteria dominating the lake before 2000, to nitrogen fixing cyanobacteria dominating the lake after 2000 and up until 2004 as phosphorus inputs were high and nitrogen was limiting. This time was referred to as the "pre-hurricane" time period, and the period after the 2004–2005 hurricane season was referred to as the "post-hurricane" period. During the post-hurricane period, light became limiting and influenced phytoplankton composition.
Kramer et al. (2018) studied Lake Okeechobee during and after its major 2016 algal bloom that was related to the El Niño event. They collected information on nutrient availability, phytoplankton communities, and the presence of toxins, along with the genetic makeup of the phytoplankton communities and their genetic abilities to produce toxins. Additionally, they conducted nutrient experiments to couple with their findings. They found that cyanobacteria with the ability to do nitrogen fixation were in high abundance during this 2016 algal bloom. During this time, nitrogen was a limiting factor due to the extreme amounts of phosphorus in the freshwater ecosystem. The field experiments conducted with this study found that microcystin, the toxin produced by cyanobacteria, was produced in higher quantities when there was more nitrogen present.
A study conducted by Pei, Zhang, and Mitsch (2020) examined nitrate concentrations, and their respective isotope compositions, in hopes of determining origins of major inflows and outflows of nitrogen into the lake and what their respective contributions are. They found that ammonium based fertilizers and soil nitrogen were the largest contributors to nitrate found in the lake. Manure and precipitation were two other sources of nitrate. These results can aid in monitoring and regulation of nitrogen uses around Okeechobee, and subsequently aid in restoring the lake.
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic multicellular organisms like seaweed and microscopic unicellular organisms like cyanobacteria. Algal bloom commonly refers to the rapid growth of microscopic unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.
Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytoplankton productivity". Water bodies with very low nutrient levels are termed oligotrophic and those with moderate nutrient levels are termed mesotrophic. Advanced eutrophication may also be referred to as dystrophic and hypertrophic conditions. Eutrophication can affect freshwater or salt water systems. In freshwater ecosystems it is almost always caused by excess phosphorus. In coastal waters on the other hand, the main contributing nutrient is more likely to be nitrogen, or nitrogen and phosphorus together. This depends on the location and other factors.
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.
Florida Bay is the bay located between the southern end of the Florida mainland and the Florida Keys in the United States. It is a large, shallow estuary that while connected to the Gulf of Mexico, has limited exchange of water due to various shallow mudbanks covered with seagrass. The banks separate the bay into basins, each with its own unique physical characteristics.
Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes. Hypoxia occurs when dissolved oxygen (DO) concentration falls to or below 2 mg of O2/liter. When a body of water experiences hypoxic conditions, aquatic flora and fauna begin to change behavior in order to reach sections of water with higher oxygen levels. Once DO declines below 0.5 ml O2/liter in a body of water, mass mortality occurs. With such a low concentration of DO, these bodies of water fail to support the aquatic life living there. Historically, many of these sites were naturally occurring. However, in the 1970s, oceanographers began noting increased instances and expanses of dead zones. These occur near inhabited coastlines, where aquatic life is most concentrated.
The Kissimmee River is a river in south-central Florida, United States that forms the north part of the Everglades wetlands area. The river begins at East Lake Tohopekaliga south of Orlando, flowing south through Lake Kissimmee into the large, shallow Lake Okeechobee. Hurricane-related floods in 1947 prompted channelization of the meandering lower stretch, completed by 1970. The straightened course reduced wetland habitat and worsened pollution. In response, ongoing efforts since the 1990s have partially restored the river's original state and revitalized the ecosystem.
Lagoa das Sete Cidades is a twin lake situated in the crater of a dormant volcano on the Portuguese archipelago of the Azores. It consists of two small, ecologically different lakes connected by a narrow strait, which is crossed by a bridge. The volcano is located on the western third of the island of São Miguel. The Lagoa das Sete Cidades part of a natural landscape of communitarian interest: it is the largest body of water in the region and one of the most important freshwater resources in the archipelago.
The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth. The production of phosphine gas occurs in only specialized, local conditions. Therefore, the phosphorus cycle should be viewed from whole Earth system and then specifically focused on the cycle in terrestrial and aquatic systems.
The St. Lucie River is a 35-mile-long (56 km) estuary linked to a coastal river system in St. Lucie and Martin counties in the Florida, United States. The St. Lucie River and St. Lucie Estuary are an "ecological jewel" of the Treasure Coast, central to the health and well-being of the surrounding communities. The river is part of the larger Indian River Lagoon system, the most diverse estuarine environment in North America with more than 4,000 plant and animal species, including manatees, oysters, dolphins, sea turtles and seahorses.
Monomictic lakes are holomictic lakes that mix from top to bottom during one mixing period each year. Monomictic lakes may be subdivided into cold and warm types.
A harmful algal bloom (HAB) is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are sometimes defined as only those algal blooms that produce toxins, and sometimes as any algal bloom that can result in severely lower oxygen levels in natural waters, killing organisms in marine or fresh waters. Blooms can last from a few days to many months. After the bloom dies, the microbes that decompose the dead algae use up more of the oxygen, generating a "dead zone" which can cause fish die-offs. When these zones cover a large area for an extended period of time, neither fish nor plants are able to survive. Harmful algal blooms in marine environments are often called "red tides".
Bacterioplankton refers to the bacterial component of the plankton that drifts in the water column. The name comes from the Ancient Greek word πλανκτος, meaning "wanderer" or "drifter", and bacterium, a Latin term coined in the 19th century by Christian Gottfried Ehrenberg. They are found in both seawater and freshwater.
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion. Raw sewage is a large contributor to cultural eutrophication since sewage is high in nutrients. Releasing raw sewage into a large water body is referred to as sewage dumping, and still occurs all over the world. Excess reactive nitrogen compounds in the environment are associated with many large-scale environmental concerns. These include eutrophication of surface waters, harmful algal blooms, hypoxia, acid rain, nitrogen saturation in forests, and climate change.
Hypoxia refers to low oxygen conditions. Normally, 20.9% of the gas in the atmosphere is oxygen. The partial pressure of oxygen in the atmosphere is 20.9% of the total barometric pressure. In water, oxygen levels are much lower, approximately 7 ppm or 0.0007% in good quality water, and fluctuate locally depending on the presence of photosynthetic organisms and relative distance to the surface.
PCLake is a dynamic, mathematical model used to study eutrophication effects in shallow lakes and ponds. PCLake models explicitly the most important biotic groups and their interrelations, within the general framework of nutrient cycles. PCLake is used both by scientist and water managers. PCLake is in 2019 extended to PCLake+, which can be applied to stratifying lakes.
Gloeotrichia is a large (~2 mm) colonial genus of Cyanobacteria, belonging to the order Nostocales. The name Gloeotrichia is derived from its appearance of filamentous body with mucilage matrix. Found in lakes across the globe, gloeotrichia are notable for the important roles that they play in the nitrogen and phosphorus cycles. Gloeotrichia are also a species of concern for lake managers, as they have been shown to push lakes towards eutrophication and produce deadly toxins.
Aureoumbra lagunensis is a unicellular planktonic marine microalga that belongs in the genus Aureoumbra under the class Pelagophyceae. It is similar in morphology and pigments to Aureococcus anophagefferens and Pelagococcus subviridis. The cell shape is spherical to subspherical and is 2.5 to 5.0 μm in diameter. It is golden-coloured and is encapsulated with extracellular polysaccharide layers and has a single chloroplast structure with pigments.
Lake 226 is one lake in Canada's Experimental Lakes Area (ELA) in Ontario. The ELA is a freshwater and fisheries research facility that operated these experiments alongside Fisheries and Oceans Canada and Environment Canada. In 1968 this area in northwest Ontario was set aside for limnological research, aiming to study the watershed of the 58 small lakes in this area. The ELA projects began as a response to the claim that carbon was the limiting agent causing eutrophication of lakes rather than phosphorus, and that monitoring phosphorus in the water would be a waste of money. This claim was made by soap and detergent companies, as these products do not biodegrade and can cause buildup of phosphates in water supplies that lead to eutrophication. The theory that carbon was the limiting agent was quickly debunked by the ELA Lake 227 experiment that began in 1969, which found that carbon could be drawn from the atmosphere to remain proportional to the input of phosphorus in the water. Experimental Lake 226 was then created to test phosphorus' impact on eutrophication by itself.
Lake 227 is one of 58 lakes located in the Experimental Lakes Area (ELA) in the Kenora District of Ontario, Canada. Lake 227 is one of only 5 lakes in the Experimental Lakes Area currently involved in long-term research projects, and is of particular note for its importance in long term lake eutrophication studies. The relative absence human activity and pollution makes Lake 227 ideal for limnological research, and the nature of the ELA makes it one of the only places in the world accessible for full lake experiments. At its deepest, Lake 227 is 10 meters deep, and the area of the lake is approximately 5 hectares. Funding and governmental permissions for access to Lake 227 have been unstable in recent years, as control of the ELA was handed off by the Canadian government to the International Institute for Sustainable Development (IISD).
Patricia Marguerite Glibert is marine scientist known for her research on nutrient use by phytoplankton and harmful algal blooms in Chesapeake Bay. She is an elected fellow of the American Association for the Advancement of Science.
Media related to Lake Okeechobee at Wikimedia Commons