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

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regression equation indicated that the relationship between Pontoporeia
and depth is not simple or linear. This second order polynomial term
probably implies that, in this shallow region of the lake, depth is ulti-.
mately associated with the abundance of amphipods, but is also associated
to some extent with the other environmental parameters.
At first glance it is surprising that surface temperature should be
so important for explaining amphipod abundance in the shallower portions
of the lake. Within this area of the lake the thermocline is usually either
absent or not well established, so bottom temperature is usually a function of surface temperature. The positive effect of water temperature
on the abundance of this amphipod is probably attributable to the effect
that temperature has on growth rate. As the amphipods increase in size
they are probably better able to survive in this environment.
Beyond 36 m there was little interrelationship between Pontoporeia
and the physical environment, At the 36-65 m depth zone, sediment
showed the same inverse relationship as it did in the shallower regions
and had about the same influence on amphipod abundance. Depth had a
slight inverse effect on amphipod counts, and beyond 105 m depth had a
very strong negative influence on amphipod density.
Within the deeper portions of the lake the rain of particulate matter
is slowed considerably by the water column. Bruun (1957), in an investigation of the ocean, indicated that over great depths this rain of particles,
which is mainly derived from plankton, is rapidly consumed by the animals