Ecology of the burrowing amphipod, Pontoporeia affinis, in Lake Michigan / by Wayne Paul Alley.

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squared, chironomids, and oligochaetes in that order of importance.
These four variables accounted for approximately 46 percent of the
fluctuation of Pontoporeia abundance.
At depths greater than 105 m, depth became the most important
factor in determining the variability in amphipod abundance followed by
ologochaetes and sphaeriids, in that order. These three parameters
accounted for 68 percent of the fluctuations in amphipod density.
When the lake was treated as a single unit, additional parameters
became important in determining the fluctuations of Pontoporeia density.
The sphaeriids were the most important, followed by depth squared,
chironomids, depth, distance from shore, day of the year, sediment
type, and bottom temperature. These eight variables accounted for
approximately 63 percent of the changes in the amphipod counts. However, the last seven of these eight parameters contributed only eight
percent of the coefficient of determination.
When the lake was subdivided into four depth zones, three environmental parameters, day of year, percent carbon in the sediment, and
bottom temperature had no influencing effects on the amphipod populations. When the lake was treated as a single system, surface temperature, percent carbon in the sediments and oligochaetes did not significantly affect amphipod abundance. Multiple regression analysis indicated that the density of these organisms is not influenced by the percent
carbon in the sediment.