Cook Plant preoperational studies, 1969 / John C. Ayers ... [et al.].

In the zooplankton data there was a decrease in total numbers between intake and outfall (22.89 organisms per liter to 7.98), and many dead or broken
organisms were observed in the outfall sample (see Table 6). Beyond the outfall
channel mouth there is a rise of total organisms per liter to 42.61 but this
increase is due solely to the rotifer, Asplanchna sp. At Station MCP-8 at the
edge of the plume the population was composed of three organism groups all of
which were in lower numbers than in the intake, with a total population of I.61
organisms per liter. Perhaps more significant is the condition at Station MCP-13
at the far end of the demonstrable plume where, with population composition
differing only slightly from the intake, the total numbers of organisms per liter
was down to 6.90 with only the cladoceran, Bosmina sp., and the copepod, Diap)tomus
sp., showing any rise above intake levels. As in the phvtoplankton, we are unslre
whether drifting in of other water masses affected the results.
The benthos data are presented in Table 7. In the analysis of ti- c- dita
particular attention has been paid to the number of clean-water-lloin amphipods
and to the number of pollution tolerant oligochaetes. In thie shall.-I: stations,
MCP-1 through MCP-8, no amphipods or oligochaetes were collected. These stations
are subject to both wave action, refracted around the outer breakwall, and the
scouring action of the plant's cooling water discharge. At Stations '1CP-13 and
14, where both the heated plant plume and the organic contribution from t'he
river outflow might be expected to be most consistently present under the prevailing southwest winds, there were abundant amphipods and modest numbers o(oligochaetes (as oligochaetes numbers go). It should be pointed out here that
Stations MCP-12, 13, and 14 were the only stations in the survey area where the
bottom was of the silty fine sand that in Lake Michigan is typified by abundant
benthic organisms. Except for Station MCP-10 which was on hard grey clay, every
other station in the area was bottomed by clean (not silty) sand. The higher
benthic populations at Stations 12, 13, and 14 are much more apt to be explained

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