Råcksta Träsk (

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

: "

Råcksta Råcksta is a district of Västerort, Stockholm, in Hässelby-Vällingby. It is next to the suburbs of Grimsta (Stockholm), Grimsta, Vällingby, Nälsta, Flysta, Beckomberga, Norra Ängby and Blackeberg. It had 4,484 inhabitants in 2005 and is 1.42& ...

Swamp") is a small

lake 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 ...

in the western suburbs of

Stockholm Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

. Notwithstanding its location in the vicinity of the Swedish capital and high levels of

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

and

copper Copper is a chemical element; it has symbol Cu (from Latin ) 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-orang ...

, the lake is considered as an important breeding ground for

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

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 R� ...

Kyrksjön Kyrksjön () 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 located near Kyrksjön: ...

, and Lillsjön.

Catchment area

The catchment area is mostly composed of forest and open terrain part of the

Grimsta nature reserve Grimsta Nature Reserve (or Grimstaskogen), is a nature reserve in Västerort, in the municipality of Stockholm, Sweden. Grimsta Nature Reserve is surrounded by Södra Ängby, Blackeberg, Grimsta, Hässelby and Lake Mälaren. It is located in th ...

, 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, the western part of Stockholm Municipality, Sweden. It is notable for being one of the first modern planned suburbs in Sweden. Vällingby was inaugurated in 1954 as part of Stockholm's post-war ...

and

Hässelby Hässelby is a Swedish town that is a part of Hässelby-Vällingby in the city of Stockholm, Sweden. It contains the suburban areas of Hässelby Gård, Hässelby Strand and Hässelby Villastad, and its territory also corresponds to Hässelb ...

. 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 i ...

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 written 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 lan ...

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) and 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 excret ...

s to the lake with minor contributions of

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It 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 tabl ...

and

(from roofs). High levels of

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

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 Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

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 * P ...

in lower sediments. Levels of copper in the

water table The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...

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 Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

content in August is mostly composed of

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

, with minor populations of

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

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'', wh ...

, and no presence of

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

. Among

Zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

the most common is various species of

rotifer The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic Coelom#Pseudocoelomates, pseudocoelomate animals. They were first describ ...

s, with occurrence of

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

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 flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

s. The number of

aquatic plant Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...

s is relatively small, with the lake floor dominated by rigid hornwort, and free-floating plants including ''

Lemna minor ''Lemna minor'', the common duckweed or lesser duckweed, is a species of aquatic freshwater plant in the subfamily Lemnoideae of the arum family Araceae. ''L. minor'' is used as animal fodder, bioremediator, for wastewater nutrient recovery, and ...

'', yellow water-lily, 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 habit ...

'', slender tufted-sedge, cyperus-like sedge,

reed sweet-grass ''Glyceria maxima'' (syn. ''G. aquatica'' (L.) Wahlenb.; ''G. spectabilis'' Mert. & W.D.J. Koch; ''Molinia maxima'' Hartm.; ''Poa aquatica'' L.), ''imfe Nd'' commonly known as great manna grass, reed mannagrass, reed sweet-grass, and greater swee ...

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", ...

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 plant, perennial reed (plant), reed Poaceae, grasses found in wetlands throughout temperate and tropical regions of the world. Taxonomy The World Checklist of Selected Plant Famili ...

'', ''

Rorippa amphibia ''Rorippa amphibia'', also known as great yellow-cress, is a plant species in the family Brassicaceae. The flowers are visited by many types of insects, and can be characterized by a generalized pollination syndrome. References

Rorippa, ...

'', 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 in ...

and grey sallow. An examination in 1996 showed the

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

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 Lat ...

accompanied by populations of

perch Perch is a common name for freshwater fish from the genus ''Perca'', which belongs to the family Percidae of the large order Perciformes. The name comes from , meaning the type species of this genus, the European perch (''P. fluviatilis'') ...

roach Roach or The Roach may refer to: Animals * Cockroach, various insect species of the order Blattodea * Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae ** ''Rutilus'' or roaches, a genus of fishes * Cal ...

tench The tench or doctor fish (''Tinca tinca'') is a freshwater, fresh- and brackish water, brackish-water fish of the order Cypriniformes found throughout Eurasia from Western Europe including Great Britain, Britain and Ireland east into Asia as far ...

, and

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

. Introduction of

trout Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...

and

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...

was made in 1992. The

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

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 Eurasia, and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, home to ...

mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It 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 Emberiza, bunting family Emberizidae, a group now separated by most modern authors from the finches, Fringillidae. The genus name ''Emberiza'' is from Old High German, ...

, and

common moorhen The common moorhen (''Gallinula chloropus''), also known as the waterhen, is a bird species in the Rail (bird), rail family (Rallidae). It is distributed across many parts of the Old World, across Africa, Europe, and Asia. It lives around well-ve ...

. 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 or simply the frog, is a semi ...

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 toad found throughout most of Europe (with the exception of Ireland, Iceland, parts of Scandinavia, and some List ...

, 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

Notes

References