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

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Milwaukee Harbor and the adjacent embayment. Inside the breakwater
they found a high density of oligochaetes, no amphipods, and considerable
environmental degradation. The embayment immediately outside the
breakwaters also showed environmental degradation, high densities of
oligochaetes, and occasionally Pontoporeia.
The low density Pontoporeia, as a criterion for water pollution, is
very unsatisfactory because the abundance of this amphipod is dependent
on many environmental conditions, some of which bear no relation to
water pollution. This study showed that bottom sediments can strongly
affect the density of Pontoporeia. High water temperatures and low
oxygen tensions, which were previously considered limiting environmental
factors for this amphipod, are not necessarily a deterrent for their habitation. Before an area can be classified as polluted, by using the low
levels of Pontoporeia as the indicator of pollution, a very careful examination must be made of the environment to determine if low densities are
attributable to pollution or the disrupting effects of an environmental
factor.