Råcksta Träsk ( Swedish: " Råcksta Swamp") is a small

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much lar ...

in the western suburbs of Stockholm, Sweden. Notwithstanding its location in the vicinity of the Swedish capital and high levels of

lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...

and

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...

, the lake is considered as an important breeding ground for

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...

s, of moderate interest to pleasure fishing, and of minor interest for birds.Råcksta träsk There are three other small lakes located nearby:

Judarn Judarn is a small lake in Bromma, a western suburb of Stockholm, Sweden. Surrounded by forest and the Judarskogen nature reserve, it stretches between Åkeshov and Södra Ängby. Three other lakes are found nearby: Kyrksjön, Lillsjön, and ...

Kyrksjön Kyrksjön ( sv, Church Lake) is a small lake in Bromma, a western suburb in Stockholm, Sweden. Named after its vicinity to the old Bromma Church, the lake was made part of the nature reserve Kyrksjölöten in 1997. Three other lakes are locate ...

, and Lillsjön.

Catchment area

The catchment area is mostly composed of forest and open terrain part of the Grimsta nature reserve, with several minor wetlands. 20 percent of the catchment area is composed of residential buildings and 10 per cent of roads. 300 metres downstream is a historical mill administrated by a society devoted to local culture and history (''Vällingby hembygdsförening'') with limited means to regulate the water level. West of the lake is a grass-grown peak composed of excavated material from the construction of the suburbs

Vällingby Vällingby () is a suburban district in Västerort in the western part of Stockholm Municipality, Sweden. History The agricultural land where the modern suburb now stands, has a history stretching some 2,000 years back (i.e. at least twic ...

and

Hässelby Hässelby is a Swedish town that is a part of Hässelby-Vällingby in the city of Stockholm, Sweden, comprising the suburban areas Hässelby Gård, Hässelby Strand and Hässelby Villastad. The territory also corresponds to Hässelby paris ...

. Several heavily trafficked roads and a metro track passes above ground through the catchment area. 7 hectares of the area is occupied by the

Råcksta Crematorium Råcksta is a district of Västerort, Stockholm, in Hässelby-Vällingby. It is next to the suburbs of Grimsta, Vällingby, Nälsta, Flysta, Beckomberga, Norra Ängby and Blackeberg Blackeberg is a suburb of Stockholm built in the 1950s, and is ...

and its cemetery.Vattenprogram, p 5.3-5.5 The lake and the surrounding area is regarded as of great recreational value. Pathways were arranged around the lake in the 1970s, angling is popular, and, occasionally, a skating-rink is ploughed on the lake during winters.Vattenprogram, p 5.5-5.7

Environmental influence

Local

storm water Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed land ...

pipes, occasionally fouled with

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

of unknown origin, produces most of the affluent, with remaining contributions coming from local roads and run-off from residential areas, the latter bringing mostly

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excr ...

s to the lake with minor contributions of

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic t ...

and

(from roofs). High levels of

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...

have been recorded during late winters and summer. Reports in 1991-1997 of metal content in lake sediments noted moderate levels of

, the highest levels of

in any lake in Stockholm, and raised levels of

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

s such as PAHs and

PCB PCB may refer to: Science and technology * Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant * Printed circuit board, a board used in electronics * ...

in lower sediments. Levels of copper in the

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. Th ...

were reported as 50 times national median value.

Flora and fauna

Phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. P ...

content in August is mostly composed of

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

, with minor populations of diatom and

golden algae The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, '' Prymnesium parvum'', whic ...

, and no presence of cyanobacteria. Among

Zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

the most common is various species of

rotifer The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John H ...

s, with occurrence of

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have p ...

s, bosminidae, and

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a differen ...

s. The number of

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

s is relatively small, with the lake floor dominated by

rigid hornwort ''Ceratophyllum demersum'', commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of '' Ceratophyllum''. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents excep ...

, and free-floating plants including '' Lemna minor'',

yellow water-lily Yellow waterlily is a common name for several plants and may refer to: * ''Nymphaea'' species, especially: ** ''Nymphaea mexicana ''Nymphaea mexicana'' is a species of aquatic plant that is native to the Southern United States and Mexico as far ...

, white waterlily, broad-leaved pondweed, and

amphibious bistort ''Persicaria amphibia'' (syn. ''Polygonum amphibium'') is a species of flowering plant in the knotweed family known by several common names, including longroot smartweed, water knotweed, water smartweed, and amphibious bistort. It is native to ...

. Along the shores are ''

Alisma ''Alisma'' is a genus of flowering plants in the family Alismataceae, members of which are commonly known as water-plantains. The genus consists of aquatic plants with leaves either floating or submerged, found in a variety of still water habi ...

'', slender tufted-sedge, cyperus-like sedge, reed sweet-grass,

yellow iris ''Iris pseudacorus'', the yellow flag, yellow iris, or water flag, is a species of flowering plant in the family Iridaceae. It is native to Europe, western Asia and northwest Africa. Its specific epithet ''pseudacorus'' means "false acorus", ref ...

purple loosestrife ''Lythrum salicaria'' or purple loosestrifeFlora of NW Europe''Lythrum salicaria'' is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the family Pr ...

, ''

Phragmites ''Phragmites'' () is a genus of four species of large perennial reed grasses found in wetlands throughout temperate and tropical regions of the world. Taxonomy The World Checklist of Selected Plant Families, maintained by Kew Garden in Lon ...

'', ''

Rorippa amphibia ''Rorippa amphibia'' is a plant species in the genus '' Rorippa''. It is called great yellowcress. The flowers are visited by many types of insects, and can be characterized by a generalized pollination syndrome. References amphibia ...

'', and many others. Common trees found around the lake include

black alder Black alder is a common name for several plants and may refer to: *''Alnus glutinosa'', native to Europe and widely naturalized *''Ilex verticillata ''Ilex verticillata'', the winterberry, is a species of holly native to eastern North America i ...

and grey sallow. An examination in 1996 showed the

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...

stock is dominated by

crucian carp The crucian carp (''Carassius carassius'') is a medium-sized member of the common carp family Cyprinidae. It occurs widely in northern European regions. Its name derives from the Low German ''karusse'' or ''karutze'', possibly from Medieval Lati ...

accompanied by populations of

perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Per ...

, roach,

tench The tench or doctor fish (''Tinca tinca'') is a fresh- and brackish-water fish of the order Cypriniformes found throughout Eurasia from Western Europe including the British Isles east into Asia as far as the Ob and Yenisei Rivers. It is als ...

, and

common carp The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...

. Introduction of

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-sa ...

and

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coast ...

was made in 1992. The

signal crayfish The signal crayfish (''Pacifastacus leniusculus'') is a North American species of crayfish. It was introduced to Europe in the 1960s to supplement the North European '' Astacus astacus'' fisheries, which were being damaged by crayfish plague, b ...

is known to exist in the lake. Bird life at the lake was abundant before the lake was dredged in 1973. Since then it has been reduced but has a stable population of

mute swan The mute swan (''Cygnus olor'') is a species of swan and a member of the waterfowl family Anatidae. It is native to much of Eurosiberia, and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, ho ...

mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...

reed bunting The common reed bunting (''Emberiza schoeniclus'') is a passerine bird in the bunting family Emberizidae, a group now separated by most modern authors from the finches, Fringillidae. The genus name ''Emberiza'' is from Old German ''Embritz'', a ...

, and

common moorhen The common moorhen (''Gallinula chloropus''), also known as the waterhen or swamp chicken, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World. The common moorhen lives around well-vegetated mar ...

. The area is an important breeding locale for

common frog The common frog or grass frog (''Rana temporaria''), also known as the European common frog, European common brown frog, European grass frog, European Holarctic true frog, European pond frog or European brown frog, is a semi-aquatic amphibian ...

and

common toad The common toad, European toad, or in Anglophone parts of Europe, simply the toad (''Bufo bufo'', from Latin ''bufo'' "toad"), is a frog found throughout most of Europe (with the exception of Ireland, Iceland, and some Mediterranean islands), in ...

, both species being protected and classified as of local and regional interest.

Visiting

Guided tours in the area by foot or bike are frequently arranged by the city and the Society for Nature Conservation.SNF Nearest metro station is Råcksta.

Notes

References