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

A concentration of Pontoporeia exists around the 35 m depth contour,
which usually coincides with the junction of the profundal and sublittoral
zones. The low density of amphipods in the sublittoral is due to the
environmental extremes of this area, while the profundal has a more
uniform environment and fewer amphipods, which is here attributed to
a slower growth rate and less available food.
The lake was divided into four depth zones: 10-35 m, 36-65 m,
66-105 m, and greater than 105 m, and the effects of the environment on
the abundance of Pontoporeia were examined by stepwise multiple regression analysis for these depth zones. The multiple correlation coefficients
for these zones were: 0. 756 at 10-35 m, 0. 599 at 36-65 m, 0. 677 at
66-105 m, and 0.826 at the greater than 105 m depth zone. When all
depths were combined the multiple correlation coefficient was 0. 796.
These high correlation coefficients indicate that the environmental variables statistically contributed a considerable amount of information about
changes in amphipod abundance.
The average standing crop of Pontoporeia was examined for the
individual depth zones and all depths combined; and, in general, there
did not appear to be any major deviations among the average standing
crops for the three sampling seasons.
The patterns of seasonal amphipod abundance were examined at six
profundal stations of one transect, and these patterns appeared to be
quite similar, particularly for adjacent pairs of stations.

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