In response to a massive outbreak of spruce budworm (Choristoneura fumiferana) in northern Maine, the Maine Forest Service contracted for aerial application of DDT (one pound per acre) over vast acreages in 1958. Quantitative pretreatment surveys of the benthic insect fauna of several fast-flowing streams, both inside and outside of the proposed treatment area, revealed robust populations of aquatic stages of midges, black flies, mayflies, stoneflies, and caddis-flies, all important as food resources for brook trout (Salvelinus fontinalis). Immediately after the spray application, midge populations dropped by 62%, black flies 49%, mayflies 65%, stoneflies 47%, and caddisflies 60%. Populations of midges, black flies, and mayflies recovered to prespray levels by mid-August of 1959. The recovery of populations in the other taxa varied from minimal to complete in the summer of

1959. Before spraying, most trout stomachs examined contained caddisfly larvae, and after spraying, none. Before spraying, no dead trout were found in blocking nets, and after spraying, only 2% of the dead fish in blocking nets were trout. Trout populations, mainly consisting of larger fish and young-of-the-year, dropped sharply immediately after spraying, but recovered completely during the following two summers. All trout collected from the sprayed area three months after spraying contained residues of DDT (2.9-198.0 ppm).

The greater parts of the boreal forest and tundra biomes lie outside the regions of intensive agricultural production and therefore largely escape the direct effects (especially by dissolved inorganic nitrogen and phosphorus) of fertilizer and pesticide runoff into freshwater ecosystems. However, agricultural enterprises have been carved out of the taiga in Alaska (e.g., near Fairbanks, Palmer, and Delta Junction), Canada, and northern Europe. These farming operations utilize pesticides and inorganic fertilizers to some extent, and the dairy and swine operations generate quantities of manure. But these are relatively minor impacts on northern freshwater ecosystems when compared to the industrial pollutants, smog, dioxins, black carbon aerosols, acid rain, and radioactive contaminants that have made their way to the taiga and tundra regions of the world, mainly by atmospheric transport. Arctic rivers may also receive direct discharges of industrial waste (e.g., the rivers Ob' and Yenisey in the Russian Arctic), and also transport runoff from mining and agricultural areas (see Local and Transboundary Pollution).

For long eons in the past, the taiga and tundra remained largely undisturbed and seemingly constant, subject only to the natural cycles of the seasons, of fire, and of predator-prey interactions and their reciprocal population oscillations. This long-running state of equilibrium is now being disturbed by the exploitation of resources (timber, fish, fur, minerals, and oil), by pollution both from without and from within the North, and by a warming trend that is inexorably impacting the most basic rhythms and parameters of Arctic ecosystems. The changes are so great and so pervasive that the North of 50 years hence may be quite different from the North that was known 50 years ago, or even different from the North as described in this overview essay (see Global Change Effects).

J. Richard Gorham

See also Fish; Peatlands and Bogs; Wet Tundra Further Reading

Arctic Monitoring and Assessment Programme, Arctic

Pollution Issues: A State of the Arctic Environment Report,

Oslo: AMAP, 1997

Bliss, L.C. (editor), Truelove Lowland, Devon Island, Canada: A High Arctic Ecosystem, Edmonton: University of Alberta Press, 1977

-, "Arctic ecosystems of North America." In Polar and

Alpine Tundra, edited by F.E. Wielgolaski, Amsterdam: Elsevier, 1997, pp. 551-683 Brown, Jerry, Philip C. Miller, Larry L. Tieszen & Fred L. Bunnell (editors), An Arctic Ecosystem: The Coastal Tundra at Barrow, Alaska, Stroudsburg, Pennsylvania: Dowden, Hutchinson and Ross, 1980 Chapin III, F. Stuart, Robert L. Jefferies, James F. Reynolds, Gaius R. Shaver, Josef Svoboda & Ellen W. Chu (editors), Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective, San Diego: Academic Press, 1992 Chernov, Yu.I., The Living Tundra, Cambridge: Cambridge

University Press, 1985 Currie, Douglas C., Donna Giberson & Brian V. Brown, "Insects of Keewatin and Mackenzie." Newsletter of the Biological Survey of Canada (Terrestrial Arthropods), 19(2) (2000): 48-51

Danks, H. V., "Overwintering of some north temperate and arctic Chironomidae. I. The winter environment." Canadian Entomologist, 103(4) (1971): 589-604

-, "Overwintering of some north temperate and arctic

Chironomidae. II. Chironomid biology." Canadian Entomologist, 103(12) (1971): 1875-1910 Danks, H.V. & R.G. Foottit, "Insects of the boreal zone of Canada." Canadian Entomologist, 121(8) (1989): 625-690 Fogg, G.E., The Biology of Polar Habitats, Oxford: Oxford

University Press, 1998 Gorham, J. Richard, "Aquatic insects and DDT forest spraying in Maine." Maine Forest Service Bulletin, 19 (1961): 1-49

-, "Orchid pollination by Aedes mosquitoes in Alaska."

American Midland Naturalist, 95(1) (1975): 208-210 Harden, Deborah, Peter Barnes & Erk Reimnitz, "Distribution and character of naleds in northeastern Alaska." Arctic 30(1) (1977): 28-40

Heal, Bill, The Arctic is an Ecosystem, 2002, website:

http://www.thearctic.is Hershey, A.E., R.W. Merritt & M.C. Miller, "Insect Diversity, Life History, and Trophic Dynamics in Arctic Streams, with Particular Emphasis on Black Flies (Diptera: Simuliidae)." In Arctic and Alpine Biodiversity: Patterns, Causes and Ecosystem Consequences, edited by F. Stuart Chapin III and Christian Körner, Berlin: Springer-Verlag, 1995, pp. 283-295 Hobbie, John E. (editor), Limnology of Tundra Ponds, Barrow, Alaska, Stroudsburg, Pennsylvania: Dowden, Hutchinson and Ross, 1980

Kaufmann, Tohko, "Studies on the biology and ecology of Pyrrhalta nymphaea (Col. Chrysomelidae) in Alaska with special reference to population dynamics." American Midland Naturalist, 83(2) (1970): 496-509 Klein, David R., David F. Murray, Robert H. Armstrong & Betty A. Anderson, Alaska, 2002, website: http://biology.usgs.gov/ s+t/SNT/noframe/ak177.htm Kling, G.W., "Land-Water Interactions: The Influence of Terrestrial Diversity on Aquatic Ecosystems." In Arctic and Alpine Biodiversity: Patterns, Causes and Ecosystem Consequences, edited by F. Stuart Chapin III and Christian Körner, Berlin: Springer 1995, pp. 297-310 Morrow, J.E., The Freshwater Fishes of Alaska, Anchorage:

Alaska Northwest Publishing Company, 1980 Reynolds, James B., Fish Ecology in Arctic North America, Symposium 19, Bethesda, Maryland: American Fisheries Society, 1997

Sahanatien, Vicki, Jim Reist & John Babaluk, "How do we protect Arctic char?." Research Links, 6(2) (1998): 1, 6, 7, 12 Sailer, R. I., "Circumpolar distribution of water boatmen (Hemiptera: Corixidae)." Canadian Entomologist, 84(8) (1952): 280

Salt, R. W., "The survival of insects at low temperatures," Symposium of the Society for Experimental Biology, 23 (1970): 331-350 Tash, Jerry C., "The Zooplankton of fresh and brackish waters of the Cape Thompson area, northern Alaska." Hydrobiologia 38(1) (1971): 93-121 Walker, Ian R. & Glen M. MacDonald, "Distribution of Chironomidae (Insecta: Diptera) and other freshwater midges with respect to treeline, Northwest Territories, Canada." Arctic and Alpine Research, 27(3) (1995): 258-263 Warwick, F. Vincent & John E. Hobbie, "Ecology of Arctic Lakes and Rivers." In The Arctic: Environment, People, Policy, edited by Mark Nuttall and Terry V. Callaghan, Amsterdam: Harwood Academic Publishers, 2000, pp. 197-232 Wilimovsky, Norman J. & John N. Wolfe (editors), Environment of the Cape Thompson Region, Alaska, Washington, District of Columbia:, US Atomic Energy Commission, 1966 Young, O.R. & F.S. Chapin III, "Anthropogenic Impacts on Biodiversity in the Arctic." In Arctic and Alpine Biodiversity: Patterns, Causes and Ecosystem Consequences, edited by F. Stuart Chapin III and Christian Körner, Berlin: SpringerVerlag, 1995, pp. 183-196

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