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

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living at greater depths. Raymont (1963) indicated that although large
quantities of organic matter are present in bottom muds, this richness
is misleading because the benthos is very much dependent on plankton
supply. This is particularly interesting because no association was
found between percent carbon in the sediment and the abundance of
Pontoporeia.
It is particularly difficult to interpret the significance of the positive statistical associations that occurred between this amphipod and the
other macrobenthic groups unless they indicate that the taxonomic groups,
and especially the sphaeriids, respond to environmental changes in the
same manner as Pontoporeia. The Sphaeriidae were positively associated with Pontoporeia both at the four depth zones and when all depths
were combined, while the oligochaetes showed a positive relationship
with Pontoporeia beyond 65 m and no apparent association when the lake
was treated as a unit. The Chironomidae showed a positive association
with this amphipod only at the 66-105 m depth zone. However, the
chironomids did show a positive relationship when all depths were combined.
Robertson (1967) reported that 12 species of the Sphaeriidae were
found at our sampling stations. Eight of these species, Sphaerium
striatinum form acuminatum, Pisidium casertanum, P. compressum,
P. nitidum form pauperculum, P. fallax, P. henslowanum, P. idahoense,
and P. amnicum occurred between 10 and 20 m. Pisidium lilljeborgi and