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The Arctic is an Ecosystem
by Bill Heal
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Snow, Ice And Water
The golden fish of the arctic
  In much of the Arctic the waters are oligotrophic (literally 'little nourishment') because they are derived from ice and snow and the hard rocks provide few nutrients. Despite the lack of nutrients algae grow well even below the ice in frozen lakes and provide the basis for the food chain in the High Arctic. The algae are grazed by a variety of crustaceans (water fleas and fairy shrimps) and insect larvae which are preyed on by the Arctic char - the Golden Fish of the Arctic - which is the only fish living naturally in the High Arctic lakes. It is extremely successful, living to 25 years or more, growing up to 15-16 kg and distributed throughout the circumpolar region. This one species illustrates many of the key features of freshwater biology, and of Human ecology, in the North.
  The Arctic char is genetically adapted to survive low temperatures and its distribution extends up into the islands of the far North such as Svalbard (or Spitspergen as it used to be called). It lives for most of the year in the rivers and lakes but migrates to coastal waters for 1-2 months in summer to feed on the rich food supply before returning to breed. The age of maturity varies widely and spawning may take place every year, every two years or less frequently, depending on environmental conditions. But some populations also live year round in landlocked lakes and may develop particular characteristics different from those in distant lakes. Populations sometimes show two distinct size groups, a smaller group feeding on the bottom fauna and zooplankton while a larger group feeds on the smaller group - cannibalism. They resemble two different species. Thus, at the northern edge of its range where it is the only fish species, the Arctic char shows a highly flexible life style.
  Further South, or at lower altitudes, the Arctic char overlaps with other fish species which cannot withstand very low temperatures but are competitors in warmer waters. Where it lives with the brown trout in northern Sweden, the Arctic char tends to feed on zooplankton in the surface waters while the trout utilises the bottom fauna. But in winter the char continues to feed and moves to the bottom while the trout tends to stop feeding because it is less well adapted to low temperatures. A similar pattern of co-existence through seasonal partitioning of resources occurs between the Arctic char and the brook trout (sometimes known as brook char) in eastern Canada. As the number of fish species sharing the habitat increases even further, the diet of the char becomes even more limited until eventually it cannot survive.
  Thus the ecological 'niche' of the Arctic char, and its variation in size and other biological features, are very wide at the northern edge of its range. The niche and life history are more restricted by competition from less cold-tolerant species when biodiversity increases towards the southern edge of its range (environmental gradients again!).
  The ecological features shown by the Arctic char illustrate the flexibility that is probably widespread, but not so obvious, amongst northern animals and plants. Further, the Arctic char can also interbreed with closely related species such as brook trout. Interbreeding is a feature of many northern fish species, suggesting that evolution is still in progress in this young region.
  Human ecology has also had a great influence on the ecology of the Arctic char. The following catalogue of local and general influences, illustrate the general role of Humans in the North:
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Fishing on Kamchatka River, Russian Federation. The Association of Native People of Bystrinsky District catches fish to distribute to poor and elderly native people in the districts. Photo:Emma Wilson, 1998
For hundreds of years, the Inuit people in Greenland and Arctic Canada chose sites for permanent settlement to harvest sea-run fish. Sami people traditionally stocked alpine freshwaters with char to establish larders along reindeer migration paths.

Long-term selective fishing with gillnets removes larger fish, affecting population structure and life history traits. Use of poison and dynamite has eliminated populations on Svalbard. Repeated total removal of migrating fish using stone weirs ('saputit') has led to elimination of local populations Greenland.

Widespread construction of hydroelectric reservoirs has changed water levels, reduced shoreline spawning, increased open water and limited feeding options.

Overfishing of important prey species (capelin, Arctic cod) has reduced food supplies during important periods at sea for migrating char.

  Introduction of other fish species and freshwater shrimps to 'improve' fishing has reduced char through competition, caused genetic changes through interbreeding, and affected food chains. Other unexpected results have been, for example, reduction or loss of populations of oldsquaw and longtail ducks and predators of fish (loons, mergansers and ospreys).
  Acidification by atmospheric contaminants from southern regions, accumulated in snow over the long winter, are released as an acid pulse by the spring thaw. This has eliminated fish from many northern Scandinavian lakes, enhancing zooplankton and insect feeding birds but reducing fish feeders.
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Persistent organic pollutants (POPs), including many pesticides, are transported to the North, accumulate in fatty tissues and are concentrated up the food chain (biomagnification). Arctic char are at an intermediate stage in the chain and many populations have levels which are above national guidelines (see figure 10)

Climate warming is going to enable competitors to survive better where they are already at their northern margins change of their range. The previous advantage of winter feeding by char will be reduced because warming is expected to be greatest in winter. Char will tend to increase their range in the far North but loose ground in the South.

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The Arctic is an Ecosystem, by Bill Heal.
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