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

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Feltham 1938) established that a variety of marine organisms can utilize
bacteria as an energy source. Baier (1935) suggested that most detritus
feeders are nourished by the bacteria which decompose the detritus rather
than by the detritus upon which they appear to be feeding. Marzolf found
that in the laboratory Pontoporeia actively selected the sediments that had
been "conditioned" by the growth of bacteria.
The gut contents of several Pontoporeia collected from the lake and
of several maintained in the laboratory were examined in the present
study. Aliquots of cultured algae were added weekly to the aquaria of the
laboratory reared amphipods. The foregut of the lake samples contained
sediments coated with a layer of organic material and an occassional
diatom frustule, while the hindgut contained only sediment and diatom
frustules. The foregut of the laboratory reared amphipods contained
sediment coated with organic matter and intact algal cells. The hindgut
contained only the sediments and intact algal cells. While the organic
matter on the sediment appeared to be digested, the cellulose walls of
the algal cells appeared to be little affected by the passage through the
digestive system.
Stepwise Multiple Regression Analysis of the Environmental Parameters
Perhaps the greatest single problem confronting the analysis of a
biological system is the confounding effects that can occur between
environmental parameters. Within Lake Michigan, depth is ultimately
related to all the physical parameters measured (with day of year being