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56-415: Since 2003, Brabrand Lake has been steadily extended 3–4 km further west, with the new lake of Årslev Engsø (lit.: Årslev meadow-lake). In 2001–2, it was politically decided to abandon the artificial draining of the meadows and as of 2013, Årslev meadow lake has a surface area of around 100 hectares (250 acres). The total area including adjoining meadows and reed beds totals 240 hectares (590 acres). It

112-447: A distinct type of wetland, shares many biogeochemical characteristics with other wetlands. Like all wetlands, they play an important role in nutrient cycling because they are located at the interface of aerobic (oxic) and anaerobic (anoxic) environments. Most wetlands have a thin top layer of oxygenated soil in contact with the atmosphere or oxygenated surface waters. Nutrients and minerals may cycle between this oxidized top layer and

168-458: A fen directly is particularly damaging because it lowers the water table. A lower water table can increase aeration and dry out peat, allowing for aerobic decomposition or burning of the organic matter in peat. Draining a fen indirectly by decreasing its water supply can be just as damaging. Disrupting groundwater flow into the fen with nearby human activities such as quarrying or residential development changes how much water and nutrients enter

224-592: A fen, especially its pH, are directly influenced by the type of rocks its groundwater supply contacts. pH is a major factor in determining fen species composition and richness, with more basic fens called "rich" and more acidic fens called "poor." Rich fens tend to be highly biodiverse and harbor a number of rare or endangered species, and biodiversity tends to decrease as the richness of fen decreases. Fens tend to be found above rocks that are rich in calcium, such as limestone . When groundwater flows past calcareous (calcium-rich) rocks like limestone ( calcium carbonate ),

280-464: A fuel. Pollutants can alter the chemistry of fens and facilitate invasion by invasive species . Common pollutants of fens include road salts, nutrients from septic tanks , and runoff of agricultural fertilizers and pesticides. Shakespeare used the term "fen-sucked" to describe the fog (literally: rising from marshes) in King Lear , when Lear says, "Infect her beauty, You fen-sucked fogs drawn by

336-671: A gradient from poor to rich, with bogs at the poor end, extremely rich fens at the rich end, and poor fens in between. In this context, "rich" and "poor" refer to the species richness, or how biodiverse a fen or bog is. The richness of these species is strongly influenced by pH and concentrations of calcium and bicarbonate. These factors assist in identifying where along the gradient a particular fen falls. In general, rich fens are minerotrophic , or dependent on mineral-rich groundwater, while bogs are ombrotrophic , or dependent on precipitation for water and nutrients. Poor fens fall between these two. Rich fens are strongly minerotrophic; that is,

392-412: A large proportion of their water comes from mineral-rich ground or surface water. Fens that are more distant from surface waters such as rivers and lakes, however, are more rich than fens that are connected. This water is dominated by calcium and bicarbonate, resulting in a slightly acidic to slightly basic pH characteristic of rich fens. These conditions promote high biodiversity. Within rich fens, there

448-536: A major determinant of fen biota and biogeochemistry . Fen soils are constantly inundated because the water table is at or near the surface. The result is anaerobic (oxygen-free) soils due to the slow rate at which oxygen diffuses into waterlogged soil. Anaerobic soils are ecologically unique because Earth's atmosphere is oxygenated, while most terrestrial ecosystems and surface waters are aerobic. The anaerobic conditions found in wetland soils result in reduced , rather than oxidized , soil chemistry. A hallmark of fens

504-418: A pH of approximately 5.5 to 4. Peat in poor fens tends to be thicker than that of rich fens, which cuts off vegetation access to the mineral-rich soil underneath. In addition, the thicker peat reduces the influence of mineral-rich groundwater that buffers the pH. This makes the fen more ombrotrophic, or dependent on nutrient-poor precipitation for its water and nutrients. Poor fens may also form in areas where

560-601: A small amount dissolves and is carried to the fen supplied by the groundwater. When calcium carbonate dissolves, it produces bicarbonate and a calcium cation according to the following equilibrium: CaCO 3 + H 2 CO 3 ↽ − − ⇀ Ca 2 + + 2 HCO 3 − {\displaystyle {\ce {CaCO3 + H2CO3 <=> Ca^2+ + 2HCO3^-}}} where carbonic acid (H 2 CO 3 )

616-696: A type of wetland, but its use is generally limited to the southern United States. Third, different languages use different terms to describe types of wetlands. For instance, in Russian, there is no equivalent word for the term swamp as it is typically used in North America. The result is a large number of wetland classification systems that each define wetlands and wetland types in their own way. However, many classification systems include four broad categories that most wetlands fall into: marsh , swamp, bog , and fen. While classification systems differ on

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672-402: A valuable resource on its own and the water treatment plant is among only a few in the world to engage with this. It is hoped that the rich fen ecology which formerly characterized the lake, and is a threatened nature-type in general, can be restored in the future. The groundwater beneath and adjoining Brabrand Lake is very important, as it provides drinking water to more than 100,000 people in

728-551: A wetland is. Almost all of the phosphorus that arrives in a wetland does so through sediments or plant litter from other ecosystems. Along with nitrogen, phosphorus limits wetland fertility. Under basic conditions like those found in extremely rich fens, calcium will bind to phosphate anions to make calcium phosphates , which are unavailable for uptake by plants. Mosses also play a considerable role in aiding plants in phosphorus uptake by decreasing soil phosphorus stress and stimulating phosphatase activity in organisms found below

784-512: Is a 2,000 m racing track on Brabrand Lake and it is generally perceived as very good for outrigger racing, but other types of boats are also rowed here, including kayaks . Aarhus Roklub (Aarhus Rowing Club), based here, have scored several prestigious medals. In 2005, Maria Pertl won silver in the World Rowing Championships in collaboration with Juliane Elander Rasmussen . In 2011, Andrej Lawaetz Bendtsen won gold at

840-519: Is a large amount of variability. The richest fens are the extreme rich (marl) fens, where marl deposits are often build up. These are often pH 7 or greater. Rich and intermediate rich fens are generally neutral to slightly acidic, with a pH of approximately 7 to 5. Rich fens are not always very productive; at high calcium concentrations, calcium ions bind to phosphate anions, reducing the availability of phosphorus and decreasing primary production. Rich bogs with limited primary production can stabilize with

896-470: Is a more potent greenhouse gas than carbon dioxide. Methanogenic archaea that reside in the anaerobic layers of peat combine carbon dioxide and hydrogen gas to form methane and water. This methane can then escape into the atmosphere and exert its warming effects. Peatlands dominated by brown mosses and sedges such as fens have been found to emit a greater amount of methane than Sphagnum -dominated peatlands such as bogs. Fens play an important role in

952-607: Is a natural habitat found in floodplains , waterlogged depressions and estuaries . Reedbeds are part of a succession from young reeds colonising open water or wet ground through a gradation of increasingly dry ground. As reedbeds age, they build up a considerable litter layer that eventually rises above the water level and that ultimately provides opportunities in the form of new areas for larger terrestrial plants such as shrubs and trees to colonise. Artificial reedbeds are used to remove pollutants from greywater , and are also called constructed wetlands . Reedbeds vary in

1008-408: Is a result of the ground or surface water input. Typically, this input results in higher mineral concentrations and a more basic pH than found in bogs. As peat accumulates in a fen, groundwater input can be reduced or cut off, making the fen ombrotrophic rather than minerotrophic . In this way, fens can become more acidic and transition to bogs over time. Fens can be found around the world, but

1064-419: Is abundant in peat. When the organic matter in peat is decomposed in the absence of oxygen, ammonium is produced via ammonification . In the oxidized surface layer of the wetland, this ammonium is oxidized to nitrite and nitrate by nitrification . The production of ammonium in the reduced layer and its consumption in the top oxidized layer drives upward diffusion of ammonium. Likewise, nitrate production in

1120-1663: Is characteristic of reedbeds. It also commonly occurs in unmanaged, damp grassland and as an understorey in certain types of damp woodland . Most European reedbeds mainly comprise common reed ( Phragmites australis ) but also include many other tall monocotyledons adapted to growing in wet conditions – other grasses such as reed sweet-grass ( Glyceria maxima ), Canary reed-grass ( Phalaris arundinacea ) and small-reed ( Calamagrostis species ), large sedges (species of Carex , Scirpus , Schoenoplectus , Cladium and related genera ), yellow flag iris ( Iris pseudacorus ), reed-mace ("bulrush" – Typha species), water-plantains ( Alisma species), and flowering rush ( Butomus umbellatus ). Many dicotyledons also occur, such as water mint ( Mentha aquatica ), gipsywort ( Lycopus europaeus ), skull-cap ( Scutellaria species), touch-me-not balsam ( Impatiens noli-tangere ), brooklime ( Veronica beccabunga ) and water forget-me-nots ( Myosotis species). Many animals are adapted to living in and around reedbeds. These include mammals such as Eurasian otter , European beaver , water vole , Eurasian harvest mouse and water shrew , and birds such as great bittern , purple heron , European spoonbill , water rail (and other rails ), purple gallinule , marsh harrier , various warblers ( reed warbler , sedge warbler etc.), bearded reedling and reed bunting . Constructed wetlands are artificial swamps (sometimes called reed fields ) using reed or other marshland plants to form part of small-scale sewage treatment systems. Water trickling through

1176-458: Is difficult for a number of reasons. First, wetlands are diverse and varied ecosystems that are not easily categorized according to inflexible definitions. They are often described as a transition between terrestrial and aquatic ecosystems with characteristics of both. This makes it difficult to delineate the exact extent of a wetland. Second, terms used to describe wetland types vary greatly by region. The term bayou , for example, describes

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1232-478: Is estimated that there are approximately 1.1 million square kilometers of fens worldwide, but quantifying the extent of fens is difficult. Because wetland definitions vary regionally, not all countries define fens the same way. In addition, wetland data is not always available or of high quality. Fens are also difficult to rigidly delineate and measure, as they are located between terrestrial and aquatic ecosystems. Rigidly defining types of wetlands, including fens,

1288-420: Is greater than decomposition, which results in the accumulation of organic matter as peat. Resident mosses usually carry out decomposition within the fen, and temperate fens are often driven by plant roots' decomposition. These peat stores sequester an enormous amount of carbon. Nevertheless, it is difficult to determine whether fens net take up or emit greenhouse gases . This is because fens emit methane, which

1344-615: Is hoped that Eurasian bittern and otter will find themselves a new home here with time. In everyday parlance, "Brabrand Lake" is a general term including the surroundings as well, indicating a total area of around 560 hectares (1,400 acres) with 253 hectares (630 acres) for the lake alone. A special Natura2000 protected area under the European Union , Brabrand Lake is home to a large variety of birds and an important resting place for migrating birds, with several towers built to facilitate bird-watching. A public hiking trail surrounds

1400-576: Is produced by the dissolution of carbon dioxide in water. In fens, the bicarbonate anion produced in this equilibrium acts as a pH buffer, which keeps the pH of the fen relatively stable. Fens supplied by groundwater that doesn't flow through minerals and act as a buffer when dissolved tend to be more acidic. The same effect is observed when groundwater flows through minerals with low solubility, such as sand. In extreme rich fens, calcium carbonate can precipitate out of solution to form marl deposits. Calcium carbonate precipitates out of solution when

1456-404: Is that a significant portion of their water supply is derived from groundwater (minerotrophy). Because hydrology is the dominant factor in wetlands, the chemistry of the groundwater has an enormous effect on the characteristics of the fen it supplies. Groundwater chemistry, in turn, is largely determined by the geology of the rocks that the groundwater flows through. Thus, the characteristics of

1512-719: The Okavango Delta in Botswana and the highland slopes in Lesotho . Fens can also be found at the colder latitudes of the Southern Hemisphere. They are found in New Zealand and southwest Argentina, but the extent is much less than that of the northern latitudes. Locally, fens are most often found at the intersection of terrestrial and aquatic ecosystems, such as the headwaters of streams and rivers. It

1568-430: The cycling of nutrients such as carbon, nitrogen, and phosphorus due to the lack of oxygen (anaerobic conditions) in waterlogged organic fen soils. Fens have historically been converted to agricultural land. Aside from such conversion, fens face a number of other threats, including peat cutting, pollution, invasive species, and nearby disturbances that lower the water table in the fen, such as quarrying. Interrupting

1624-432: The partial pressure of carbon dioxide in the solution falls. The decrease in carbon dioxide partial pressure is caused by uptake by plants for photosynthesis or direct loss to the atmosphere. This reduces the availability of carbonic acid in solution, shifting the above equilibrium back towards the formation of calcium carbonate. The result is the precipitation of calcium carbonate and the formation of marl. Fen, being

1680-582: The Danish Red List (under IUCN Red List ). Some also are protected under different habitat directives of the EU. Here are a few examples: Apart from these rarer species, the Brabrand Lake area is characterized by many common species living here, mostly birds, insects and aquatic plants. The area around Brabrand Lake has been populated for at least 6,000 years. In prehistoric times, Brabrand Lake

1736-545: The WRC for seniors in a team of four. The lake is not very deep and has suffered from eutrophication for many years. The excessive nutrients originate from waste water and agricultural activities and pose a constant environmental threat to the surrounding ecology and the Bay of Aarhus. Eutrophication is a common problem all over the developed world. Starting in 1959 with 158 hectares, several environmental projects have aimed to alleviate

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1792-811: The accumulation of mosses and mycorrhiza , which promote phosphorus cycling and can support the growth of new vegetation and bacteria. Brown mosses (family Amblystegiaceae ) and sedges (genus Carex ) are the dominant vegetation. However, an accumulation of mosses such as Sphagnum can lead to the acidification of the rich fen, potentially converting it into a poor fen. Compared to poor fens, rich fens have higher concentrations of bicarbonate, base cations (Na , Ca , K , Mg ), and sulfate . Poor fens are, in many ways, an intermediate between rich fens and bogs. Hydrologically, they are more similar to rich fens than to bogs, but regarding vegetation composition and chemistry, they are more similar to bogs than rich fens. They are much more acidic than their rich counterparts, with

1848-541: The addition of Årslev Engsø, the pathway grew another 8 km. A large part of Brabrandstien is asphalted and is popular for cycling , rollerskating and jogging . Some of the graveled western parts are used for horseback riding. Cars are not allowed and motor vehicles are restricted. Brabrandstien is part of the Aarhus-Silkeborg hiking trail. On the northern bank of Brabrand Lake lies the facilities of Brabrand Rostadion (Brabrand Rowing Stadium). The stadium

1904-592: The area publicly accessible and attractive to the public. Brabrandstien (lit.: the Brabrand pathway), which runs along the Aarhus river from the inner city and around both Brabrand Sø and Årslev Engsø, was established by the City Council in 1956 as a labor project for the unemployed, to give the public better access to green space. The pathway is c. 26 km long, with 9.5 km for Brabrand Lake alone. With

1960-556: The continuous input of groundwater stimulates production. Bogs , which lack this input of groundwater , have much lower primary production. Carbon from all types of wetlands, including fens, arrives mostly as organic carbon from either adjacent upland ecosystems or by photosynthesis in the wetland itself. Once in the wetland, organic carbon generally has three main fates: oxidation to CO 2 by aerobic respiration , burial as organic matter in peat, or decomposition to methane . In peatlands, including fens, primary production by plants

2016-405: The environmental burdens and at the same time maintain the aesthetic value of the lake and surrounding areas. These projects includes mud pumping of the lakebed and willow afforestations. Also, the local water company Aarhus Vand A/S began extracting phosphor from wastewater in 2013 at a water treatment plant in Åby close to the lake. Phosphor is a key element in the eutrophication process but

2072-406: The exact criteria that define a fen, there are common characteristics that describe fens generally and imprecisely. A general definition provided by the textbook Wetlands describes a fen as "a peat-accumulating wetland that receives some drainage from surrounding mineral soil and usually supports marsh like vegetation." Three examples are presented below to illustrate more specific definitions for

2128-756: The fen. This can make the fen more ombrotrophic (dependent on precipitation), which results in acidification and a change in water chemistry. This directly impacts the habitat of these species, and many signature fen species disappear. Fens are also threatened by invasive species , fragmentation , peat cutting, and pollution. Non-native invasive species, such as the common buckthorn in North America, can invade fens and outcompete rare fen species, reducing biodiversity. Habitat fragmentation threatens fen species, especially rare or endangered species that are unable to move to nearby fens due to fragmentation. Peat cutting, while much more common in bogs, does happen in fens. Peat cut from fens has many uses, including burning as

2184-549: The flow of mineral-rich water into a fen changes the water chemistry, which can alter species richness and dry out the peat. Drier peat is more easily decomposed and can even burn. Fens are distributed around the world, but are most frequently found at the mid-high latitudes of the Northern Hemisphere. They are found throughout the temperate zone and boreal regions, but are also present in tundra and in specific environmental conditions in other regions around

2240-459: The global nitrogen cycle due to the anaerobic conditions found in their soils, which facilitate the oxidation or reduction of one form of nitrogen to another. Most nitrogen arrives in wetlands as nitrate from runoff , in organic matter from other areas, or by nitrogen fixation in the wetland. There are three main forms of nitrogen found in wetlands: nitrogen in organic matter, oxidized nitrogen ( nitrate or nitrite ), and ammonium . Nitrogen

2296-656: The greater Aarhus area. Acting partly on this fact, the lake water was also included in a large water treatment project led by Aarhus Vand A/S from 2006 to 2013. The project involved the Brabrand Lake, the Aarhus River and the Aarhus harbour, budgeted at € 45 million. As a result, the waters in Brabrand Lake and the Aarhus River attained bathing quality in September 2012. Many species of flora and fauna at Brabrand Lake are either rare or relatively rare in Denmark and on

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2352-554: The groundwater supplying the fen flows through sediments that don't dissolve well or have low buffering capacity when dissolved. Species richness tends to be lower than that of rich fens but higher than that of bogs. Poor fens, like bogs, are dominated by Sphagnum mosses, which acidify the fen and decrease nutrient availability. One of the many threats that fens face is conversion to agricultural lands. Where climates are suitable, fens have been drained for agricultural use alongside crop production, grazing , and hay making . Draining

2408-470: The lake, whose landscape varies from wide meadows and reed beds to dense woods. Privately owned pastures almost completely surround the lake and are not publicly accessible, but public paths leading to the lake are scattered in between. There are several garden allotments ("kolonihaver" in Danish) near Brabrand Lake and it is a popular recreational spot. It is a statutory goal of the Aarhus municipality to make

2464-410: The moss cover. Helophytes have been shown to bolster phosphorus cycling within fens, especially in fen reestablishment, due to their ability to act as a phosphorus sink, which prevents residual phosphorus in the fen from being transferred away from the it. Under normal conditions, phosphorus is held within soil as dissolved inorganic phosphorus, or phosphate , which leaves trace amounts of phosphorus in

2520-429: The oxidized layer and nitrate consumption in the reduced layer by denitrification drives downward diffusion of nitrate. Denitrification in the reduced layer produces nitrogen gas and some nitrous oxide , which then exit the wetland to the atmosphere. Nitrous oxide is a potent greenhouse gas whose production is limited by nitrate and nitrite concentrations in fens. Nitrogen, along with phosphorus, controls how fertile

2576-442: The presence of peat. In The Biology of Peatlands fens are defined by the following criteria: A further distinction is made between open and wooded fens, where open fens have canopy cover less than 10% and wooded fens have 10–25% canopy cover. If tall shrubs or trees dominate, the wetland is instead classified as a wooded bog or swamp forest , depending on other criteria. Hydrological conditions, as seen in other wetlands, are

2632-520: The reduced layer below, undergoing oxidation and reduction reactions by the microbial communities adapted to each layer. Many important reactions take place in the reduced layer, including denitrification , manganese reduction, iron reduction, sulfate reduction, and methanogenesis . Because wetlands are hotspots for nutrient transformations and often serve as nutrient sinks, they may be constructed to treat nutrient-rich waters created by human activities. Fens are also hotspots for primary production , as

2688-567: The reedbed is cleaned by microorganisms living on the root system and in the litter. These organisms utilize the sewage for growth nutrients , resulting in a clean effluent . The process is very similar to aerobic conventional sewage treatment, as the same organisms are used, except that conventional treatment systems require artificial aeration. Treatment ponds are small versions of constructed wetlands which uses reedbeds or other marshland plants to form an even smaller water treatment system . Similar to constructed wetlands, water trickling through

2744-497: The reedbed is cleaned by microorganisms living on the root system and in the litter. Treatment ponds are used for the water treatment of a single house or a small neighbourhood. Rich fen A fen is a type of peat -accumulating wetland fed by mineral-rich ground or surface water . It is one of the main types of wetland along with marshes , swamps , and bogs . Bogs and fens, both peat-forming ecosystems , are also known as mires . The unique water chemistry of fens

2800-573: The rest of the ecosystem. Iron is important in phosphorus cycling within fens. Iron can bind to high levels of inorganic phosphate within the fen, leading to a toxic environment and inhibition of plant growth. In iron-rich fens, the area can become vulnerable to acidification, excess nitrogen and potassium, and low water levels. Peat soils play a role in preventing the bonding of irons to phosphate by providing high levels of organic anions for iron to bind to instead of inorganic anions such as phosphate. Bogs and fens can be thought of as two ecosystems on

2856-666: The species that they can support, depending upon water levels within the wetland system, climate, seasonal variations, and the nutrient status and salinity of the water. Reed swamps have 20 cm or more of surface water during the summer and often have high invertebrate and bird species use. Reed fens have water levels at or below the surface during the summer and are often more botanically complex. Reeds and similar plants do not generally grow in very acidic water. In these situations, reedbeds are replaced by bogs and vegetation such as poor fen . Although common reeds are characteristic of reedbeds, not all vegetation dominated by this species

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2912-553: The term fen . In the Canadian Wetland Classification System, fens are defined by six characteristics: In the textbook Wetland Ecology: Principles and Conservation , Paul A. Keddy offers a somewhat simpler definition of a fen as "a wetland that is usually dominated by sedges and grasses rooted in shallow peat, often with considerable groundwater movement, and with pH greater than 6." This definition differentiates fens from swamps and marshes by

2968-430: The vast majority are located at the mid to high latitudes of the Northern Hemisphere. They are dominated by sedges and mosses , particularly graminoids that may be rarely found elsewhere, such as the sedge species Carex exilis . Fens are highly biodiverse ecosystems and often serve as habitats for endangered or rare species, with species composition changing with water chemistry. They also play important roles in

3024-648: The world. In the United States, fens are most common in the Midwest and Northeast, but can be found across the country. In Canada, fens are most frequent in the lowlands near Hudson Bay and James Bay , but can also be found across the country. Fens are also spread across the northern latitudes of Eurasia, including Britain and Ireland, as well as Japan, but east-central Europe is especially rich in fens. Further south, fens are much rarer, but do exist under specific conditions. In Africa, fens have been found in

3080-510: Was established in 1952 and was heavily renovated and rebuilt in the year 2010. C. F. Møller Architects was the architectural firm behind the new buildings. Local rowing and kayaking clubs have used the lake for practice and larger regattas for many years. Rocenter Aarhus RCA (Aarhus Rowing Center) is located here, offering qualified training for rowers and clubs in East and South Jutland on all levels (including elite) and for all ages. There

3136-596: Was part of a deep brackish water fjord , offering natural protection and food in abundance. There were archaeological excavations here as early as 1903, revealing early Stone Age settlements and activities from the Ertebølle Culture . The Brabrand Lake area is still an active archaeological site today and has revealed Bronze Age settlements and Viking activities such as a large shipbuilding yard. [REDACTED] Media related to Brabrand Lake at Wikimedia Commons Reed bed A reedbed or reed bed

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