Arctic Research Prudhoe Bay and Sagwon

The general appearance of the tundra at Prudhoe Bay (70.28° N 148.37° W), Alaska, a center for oil extraction and distribution at the northern end of the Trans-Alaska Pipeline, is little different from the tundra 100 km south at Sagwon (69.22° N 148.54° W) (although at Sagwon, the Sagavanirktok River, fast and cold from its origin in the snows and glaciers of the Brooks Range, flows at the foot of high and steep cliffs; nothing of the sort occurs at Prudhoe Bay). Both sites have myriads of shallow puddles and ponds and occasional sizeable lakes that are typical of wet tundra. The major difference in the two localities is the summer weather. At Prudhoe Bay, there is a nearly continuous thick cloud cover that blocks the summer sun and keeps the temperatures low. A brisk cold wind off the Beaufort Sea is the daily norm. This cloudbank is often clearly visible to the north from Sagwon where the 24-h sun shines brightly in a sky that is clear or partly filled with cumulus clouds. There is often a cool breeze here, too, but the sun at its zenith warms the air to 15-25°C. Sometimes the sea wind drives the cloud-bank so far south that it wraps Sagwon in a misty fog and the temperature at noon drops to c. 5°C.

At 4.5°C mosquitoes are on the wing at Sagwon, but at a High Arctic site in Canada, it was reported that mosquitoes stopped flying when the temperature dropped below 7.2°C. At Prudhoe, there are two common species of mosquitoes—Ochlerotatus (Aedes) nigripes and O. (A.) impiger—and their numbers are small. Caribou retire to this cold, windy coast, where they find some relief from the torment of mosquitoes. In contrast, at Sagwon, mosquitoes of at least six species, including the two just mentioned, gather in great swarms around any warm body—wolves, Arctic foxes, grizzly bears, caribou, people—all are surrounded by a writhing, whining envelope of mosquitoes seeking blood (however, here and commonly elsewhere in the North, there are autogenous strains of mosquitoes whose females do not seek blood; the mosquitoes take nectar, as do also the hematophagous strains, and thus become involved in pollination, but most of the energy resources they need to produce eggs are carried over from the larval stage). Black flies (Simuliidae) also join in the blood seeking; for their immature stages, they require moving water, of which there is no lack in the North. That mosquito larvae are thick in every pond and puddle and that numerous other kinds of aquatic insects and crustaceans abound suggests that sunny tundra is far more productive of aquatic invertebrates than the cold, cloudy tundra of the seacoast. Mosquitoes occur in such enormous numbers that there is no possible check upon their populations. But they do have predators and parasites. Larvae, pupae, and adults fall prey to birds of various kinds. Predatory aquatic insects—phantom midge larvae, Mochlonyx velutinus; predaceous diving beetles; water scavenger beetles (Hydrophilidae)—feed on mosquito larvae and pupae. Dragonflies (active aquatic stages also preda-ceous)—variable darner, Aeschna interrupta lineata; treeline emerald, Somatochlora sahlbergi)—take mosquitoes on the wing. Mermithid nematodes parasitize larvae of O. impiger and O. pullatus, and parasitic protozoans (Thelohania sp., Microsporidia) multiply in the larvae of O. communis, O. punctor, O. pullatus, and

O. cataphylla. Some pond sediments at Sagwon and at several other localities in Alaska are contaminated with spores of Clostridium botulinum type E.

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