Långsjön
Encyclopedia
Långsjön is a lake
in southern Stockholm
, Sweden
.
The lake is situated in an old residential neighbourhood located between the municipalities of Stockholm
and Huddinge and most of the shoreline is private property. Water level is controlled by a sluice
in the north-western end of the lake where the lake empties into Lake Mälaren
through a system of dikes and culverts. Polluted waste water was poured directly into the lake during the early 20th century which caused up to two third of the lake to be choked-up until the 1940s. It was subsequently one of the first lakes in Stockholm to be subject for various attempts to restorations. The northern shores are waterlogged whilst the bedrock surfaces along the southern. The lake has no major feeders, the inflow instead coming from local stormwater
and surface runoff
.
. Surface runoff
adds some 70 kg of phosphorus and 1,000 kg of nitrogen annually and more than half of phosphorus added through surface water is produced by the surrounding one-family houses and their gardens.
is dominated by cyanobacteria and green algae
, of which several are potentially poisonous and caused major algae blooms during the 1990s. The community of zooplankton
is representative for lakes rich in nutrients with medium-sized taxa
dominating in late spring and June, while minor taxa are otherwise prevailing. Larger zooplankton, such as Cyclopoid
Copepod
s, are rare and reaches about 40 per cent in July and August.
No inventory of aquatic plant
s has been done since the mid-1970s, but White Waterlily
is common in the minor bays. Yellow Water-lily
occur in minor numbers but Reed bed
s are missing.
Lake bed fauna includes more than 50 species dominated by freshwater gastropods
(Hippeutis complanatus
), Caddisflies
(Somatochlora metallica), beetle
s, and leech
es (Alboglossiphonia heteroclita). Additionally, in 1969 a freshwater jellyfish
(Craspedacusta sowerbii) was documented in the lake, a continental species then new to Sweden but not found in the lake since.
Fishes natural to Långsjön include Perch
, Northern Pike
, Roach
, Rudd
, Carp Bream
, Crucian Carp
, Tench
, and Ruffe
; extraneous species are Common Carp
and Mirror Carp
. Pike and Zander
are planted-out carnivorous species while Roach and Crucian carp have been decimated by trawling. Sample catches in 1999 showed the number Perch, Roach,and Carps had increased far beyond expected levels. Crayfish plague
hit the lake in 1984, but Signal Crayfish
was reintroduced within a few years.
The lake is a breeding ground for most birds common to the Stockholm-area — such as Mute Swan
, Mallard
, and Eurasian Coot
— and some less common — such as Common Moorhen
and Great Crested Grebe
. Other bird sightings include Heron
, Tufted Duck
, Common Tern
, Pochard
, and Spotted Crake
.
The lake is one of th most important breeding grounds for amphibians, with a documented presence of Common Frog
, Common Toad
and Smooth Newt
.
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
in southern Stockholm
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
.
The lake is situated in an old residential neighbourhood located between the municipalities of Stockholm
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
and Huddinge and most of the shoreline is private property. Water level is controlled by a sluice
Sluice
A sluice is a water channel that is controlled at its head by a gate . For example, a millrace is a sluice that channels water toward a water mill...
in the north-western end of the lake where the lake empties into Lake Mälaren
Mälaren
Lake Mälaren is the third-largest lake in Sweden, after Lakes Vänern and Vättern. Its area is 1,140 km² and its greatest depth is 64 m. Mälaren spans 120 kilometers from east to west...
through a system of dikes and culverts. Polluted waste water was poured directly into the lake during the early 20th century which caused up to two third of the lake to be choked-up until the 1940s. It was subsequently one of the first lakes in Stockholm to be subject for various attempts to restorations. The northern shores are waterlogged whilst the bedrock surfaces along the southern. The lake has no major feeders, the inflow instead coming from local stormwater
Stormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...
and surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
.
Catchment area
Some 60 per cent of the lake catchment area is occupied by settlements, mostly one-family houses but several minor green spaces are scattered around the lake. South-wester of the lake is a small area forming part of the Gömmaren nature reserve. The lake has two bathes.Environmental influence
The number of polluting operations in the catchment area is limited to a petrol station and an engineering workshop. In the end of the 1930s sewers were built in the area and the waste water fed into the lake during the 1920s and 1930s is today brought to the wastewater treatment works at Henriksdal, but old sewers still leak into the lake and the water was considered unfit for bathing at several occasions during the 1990s. Långsjön is one of few lakes in Stockholm where spillway overflow adds appreciable amounts of phosphorusPhosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
. Surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
adds some 70 kg of phosphorus and 1,000 kg of nitrogen annually and more than half of phosphorus added through surface water is produced by the surrounding one-family houses and their gardens.
Flora and fauna
In August, the stock of phytoplanktonPhytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
is dominated by cyanobacteria and green algae
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
, of which several are potentially poisonous and caused major algae blooms during the 1990s. The community of zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
is representative for lakes rich in nutrients with medium-sized taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
dominating in late spring and June, while minor taxa are otherwise prevailing. Larger zooplankton, such as Cyclopoid
Cyclopoida
Cyclopoida is an order of small crustaceans from the subclass Copepoda. Like many other copepods, members of Cyclopoida are small, planktonic animals living both in the sea and in freshwater habitats. They are capable of rapid movement...
Copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, are rare and reaches about 40 per cent in July and August.
No inventory of aquatic plant
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...
s has been done since the mid-1970s, but White Waterlily
Nymphaea alba
Nymphaea alba, also known as the European White Waterlily, White Lotus, or Nenuphar, is an aquatic flowering plant of the family Nymphaeaceae....
is common in the minor bays. Yellow Water-lily
Nuphar lutea
Nuphar lutea is an aquatic plant of the family Nymphaeaceae, native to temperate regions of Europe, northwest Africa, and western Asia.-Growth:...
occur in minor numbers but Reed bed
Reed bed
Reed beds are natural habitats found in floodplains, waterlogged depressions andestuaries. Reed beds are part of a succession from young reed colonising open water or wet ground through a gradation of increasingly dry ground...
s are missing.
Lake bed fauna includes more than 50 species dominated by freshwater gastropods
Gastropoda
The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to quite large...
(Hippeutis complanatus
Hippeutis complanatus
Hippeutis complanatus, or the flat ram's-horn snail, is a species of minute air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk or micromollusk in the family Planorbidae, the ram's horn snails....
), Caddisflies
Trichoptera
The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
(Somatochlora metallica), beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, and leech
Leech
Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like other oligochaetes such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from other oligochaetes in significant ways...
es (Alboglossiphonia heteroclita). Additionally, in 1969 a freshwater jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
(Craspedacusta sowerbii) was documented in the lake, a continental species then new to Sweden but not found in the lake since.
Fishes natural to Långsjön include Perch
Perch
Perch is a common name for fish of the genus Perca, freshwater gamefish belonging to the family Percidae. The perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning spotted, and the...
, Northern Pike
Northern Pike
The northern pike , is a species of carnivorous fish of the genus Esox...
, Roach
Rutilus
Rutilus is a genus of fishes in the family Cyprinidae, commonly called roaches. Locally, the name "roach" without any further qualifiers is also used for particular species, particularly the Common Roach Rutilus (Latin for "shining, red, golden, auburn") is a genus of fishes in the family...
, Rudd
Rudd
The common rudd Scardinius erythropthalmus is a bentho-pelagic freshwater fish, widely spread in Europe and middle Asia, around the basins of the North, Baltic, Black, Caspian and Aral seas.-Artificially introduced:...
, Carp Bream
Carp bream
The common bream, freshwater bream, bream, bronze bream or carp bream, Abramis brama, is a European species of freshwater fish in the family Cyprinidae....
, Crucian Carp
Crucian carp
The crucian carp is a member of the family Cyprinidae, which includes many other fish, such as the common carp, or the smaller minnows. They inhabit lakes, ponds, and slow-moving rivers throughout Europe and Asia. The crucian is a medium-sized cyprinid, which rarely exceeds a weight of over 3.3...
, Tench
Tench
The tench or doctor fish is a freshwater and brackish water fish of the cyprinid family found throughout Eurasia from Western Europe including the British Isles east into Asia as far as the Ob and Yenisei Rivers. It is also found in Lake Baikal...
, and Ruffe
Ruffe
The Eurasian Ruffe or simply Ruffe is a freshwater fish found in temperate regions of Europe and northern Asia. It has been introduced into the Great Lakes of North America, reportedly with unfortunate results...
; extraneous species are Common Carp
Common carp
The Common carp is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia. The wild populations are considered vulnerable to extinction, but the species has also been domesticated and introduced into environments worldwide, and is often considered an invasive...
and Mirror Carp
Mirror carp
Mirror carp are a type of fish, commonly found in the United Kingdom and Europe. The name "Mirror Carp" originates from their scales' resemblance to mirrors. They can grow in excess of 60lb - the last few British record fish have all been mirror carp....
. Pike and Zander
Zander
Zander is a species of fish. The scientific name is Sander lucioperca , and it is closely allied to perch. Zander are often called pike-perch as they resemble the pike with their elongated body and head, and the perch with their spiny dorsal fin. Zander are not, as is commonly believed, a pike and...
are planted-out carnivorous species while Roach and Crucian carp have been decimated by trawling. Sample catches in 1999 showed the number Perch, Roach,and Carps had increased far beyond expected levels. Crayfish plague
Crayfish plague
Crayfish plague, Aphanomyces astaci, is a water mould that infects crayfish, most notably the European Astacus which dies within a few weeks of being infected...
hit the lake in 1984, but Signal Crayfish
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 Scandinavian Astacus astacus fisheries, which were being damaged by crayfish plague, but the imports turned out to be a carrier of that disease...
was reintroduced within a few years.
The lake is a breeding ground for most birds common to the Stockholm-area — such as Mute Swan
Mute Swan
The Mute Swan is a species of swan, and thus a member of the duck, goose and swan family Anatidae. It is native to much of Europe and Asia, and the far north of Africa. It is also an introduced species in North America, Australasia and southern Africa. The name 'mute' derives from it being less...
, Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
, and Eurasian Coot
Eurasian Coot
The Eurasian Coot, Fulica atra, also known as Coot, is a member of the rail and crake bird family, the Rallidae. The Australian subspecies is known as the Australian Coot.-Distribution:...
— and some less common — such as Common Moorhen
Common Moorhen
The Common Moorhen is a bird in the Rallidae family with an almost worldwide distribution. The North and South American Committees of the AOU and the IOC have voted on or before July 2011 to split the American forms into a new species Common Gallinule, however, no other committee has voted to...
and Great Crested Grebe
Great Crested Grebe
The Great Crested Grebe is a member of the grebe family of water birds.- Description :The Great Crested Grebe is long with a wingspan. It is an excellent swimmer and diver, and pursues its fish prey underwater. The adults are unmistakable in summer with head and neck decorations...
. Other bird sightings include Heron
Ardea (genus)
Ardea is a genus of herons. Linnaeus named this genus as the Great Herons, referring to the generally large size of these birds, typically 80–100 cm or more in length....
, Tufted Duck
Tufted Duck
The Tufted Duck, Aythya fuligula, is a medium-sized diving duck with a population of close to one million birds.- Description :The adult male is all black except for white flanks and a blue-grey bill. It has an obvious head tuft that gives the species its name.The adult female is brown with paler...
, Common Tern
Common Tern
The Common Tern is a seabird of the tern family Sternidae. This bird has a circumpolar distribution, breeding in temperate and sub-Arctic regions of Europe, Asia and east and central North America. It is strongly migratory, wintering in coastal tropical and subtropical regions. It is sometimes...
, Pochard
Pochard
The Common Pochard, Aythya ferina, is a medium-sized diving duck.The adult male has a long dark bill with a grey band, a red head and neck, a black breast, red eyes and a grey back. The adult female has a brown head and body and a narrower grey bill band. The triangular head shape is distinctive...
, and Spotted Crake
Spotted Crake
The Spotted Crake is a small waterbird, of the family Rallidae.Their breeding habitat is marshes and sedge beds across temperate Europe into western Asia. They nest in a dry location in marsh vegetation, laying 6-15 eggs...
.
The lake is one of th most important breeding grounds for amphibians, with a documented presence of Common Frog
Common Frog
The Common Frog, Rana temporaria also known as the European Common Frog or European Common Brown Frog is found throughout much of Europe as far north as well north of the Arctic Circle in Scandinavia and as far east as the Urals, except for most of Iberia, southern Italy, and the southern Balkans...
, Common Toad
Common Toad
The common toad or European toad is an amphibian widespread throughout Europe, with the exception of Iceland, Ireland and some Mediterranean islands...
and Smooth Newt
Smooth Newt
The Smooth Newt, also known as the Common Newt, Lissotriton vulgaris is the most common newt species of the Lissotriton genus of amphibians. L...
.