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

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differences attributable to a larger quadrat sampling area and the
greater variability between the 35 stations. It is felt that these results
merely reflect the fact that, in general, a fairly large quadrat will mask
patterns of microassociations and those regions within the lake that are
preferred by Pontoporeia are also selected by the other macrobenthic
groups.
ENVIRONMENTAL RELATIONSHIPS
Environmental Parameters Treated Individually
Depth: Eggleton (1937), in a study of the Lake Michigan macrobenthos, also found a concentration of Pontoporeia at the 30-40 m depth
zone. The density increased from 10 to 30 m, and beyond 40 m the density sharply decreased. Merna (1960), also in an investigation of the
Lake Michigan macrobenthos, did not find the 30 m concentration zone
of Pontoporeia, however, his shallowest sampling depth was approximately 20 m, Mar-zolf (1963) found no correlation with depth in a study
of Grand Traverse Bay, but his sampling depths began at 20 m.
Bottom Temperature: Gordeev (1952) reported that the optimum
temperature range for Pontoporeia, as determined through laboratory
studies, is 8.0 to 12. 0~C. The upper limit of tolerance according to
field observations is 14. 0 to 20. 0~C as reported by Samter and Weltner
1904; Ekman 1915; Thienemann 1928; Segerstrale 1937; and Bousfield
1958. It is evident from the present Lake Michigan field observations
that this amphipod can tolerate an extreme range of bottom temperatures