General studies : November, 1967 / by John C. Ayers, Joseph C. K. Huang.

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in the sandy silt region extending a mile off the mouth of the
St. Joseph River.
High quantities of organism-tissue were in most cases correlated with bottom areas of silty fine sand. The two areas of
maximum biological mass lay in silty fine sand two and three miles
off the mouth of the river, and at the second and third miles offshore south of the property. An area of less organism mass lay
in silty medium sand and in loam west of Grand Marais Lakes.
Northwest of Grand Marais Lakes there was an extensive region
that yielded less than one gram of organisms per square meter and
which reached offshore through the three-mile grid of sampling
stations.
There was no evident relation between the mass of benthicorganism tissue and the presence of organic material in the
surface sediment.
In all but one case the presence of speckled sand correlated
with low quantities of biological mass. The meaning of this
relation is not clear.
In general, the distribution of the quantities of the whole
benthic population appears to be typical of the clean-water
portions of Lake Michigan. The low population in the first mile
off the beach is normal. There is, in the present natural condition, no unusual concentration of benthic organisms near shore
that would attract fish in unusual numbers.
The distribution of the amphipod, Pontoporeia affinis, over
the survey area is shown in Figure 7B.
High numbers of this organism coincide with areas of silty