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

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early spring period for reproduction; in other depth zones they breed
year round.
The greatest environmental stresses for Pontoporeia also occur
within the sublittoral. Later visits to the sublittoral short-term study
area (in August and November) showed that molar action attributable to
storms and bottom currents had caused considerable shifting of the bottom
sediments and had resuspended the detrital material. The greater variability in the amphipod counts of the sublittoral zone found throughout
our studies probably reflects the disrupting forces attributable to ambient
meteorological and limnological conditions and to the general environmental heterogeneity of this region.
Pontoporeia reaches its maximum density at the junction of the
sublittoral and profundal zones. This region corresponds roughly to the
lower limit of the thermocline. The surficial sediments within this area
are little affected by turbulence, and the range of bottom temperatures is
not so extreme as in the shallower inshore waters. In this area and the
adjacent profundal zone, Pontoporeia matures and breeds intermittently
throughout the year. There appears to be a greater proportion of breeding females in the amphipod population that inhabits this area and the
contiguous profundal areas.
The junction of the sublittoral and profundal zones represents a
reasonably stable environment where Pontoporeia can effectively utilize
the rain of suspended particulate:matter that is created through the enrich