Arctic Zooplankton Community Structure: Exceptions to Some General Rules

Abstract

Commonly accepted theories of zooplankton species distribution hold that: 1) large-bodied zooplankton species are excluded by fish predation and so are found only in lakes and ponds without fish; and 2) because small-bodied species are unable to compete successfully against large ones and also are preyed upon heavily by invertebrate predators, they exist primarily in lakes with fish. This pattern is not followed in a group of lakes and ponds in arctic Alaska. Some of these lakes were found to support both large and small zooplankton species along with populations of facultative planktivorous fish. Other lakes that had no fish had a small-bodied zooplankton species co-existing with a more typical large-bodied community. Close analysis of these unusual distributions reveals that the mechanisms affecting zooplankton community dynamics are more subtle and complex than generally recognized, particularly in such harsh environments as the Arctic.