Phytoplankton of the seasonal surveys of 1977, and further pre- vs. post-operational comparisons at Cook Nuclear Plant / John C. Ayers, Susan J. Wiley.

from year to year by a solid line for inner stations and a dashed line for
outer stations. Such averages for 1970 are not given because only summer and
fall were surveyed.
The three-seasonal averages of numbers of forms in 1977 are: Zone 0,
inner 60.3, outer 56.2; Zone 1, inner 56.1, outer 57.8; Zone 2, inner 54.8,
outer 44.3. Ayers (1978) gives the values for 1971 through 1976.
The annual curves of mean numbers of forms in Figure 5 show substantial
degrees of parallelism, indicating that the numbers of forms in inner and outer
station groups have in general varied in the same directions from season to
season in each year.
In Zone 0 the positions of the annual curves on the graphs and the
three-seasonal averages indicate steadily rising tendencies from 1971 through
1976 with a small decrease in 1977. In Zone 1 the curve positions and averages
show a tendency to plateau in 1973 through 1975 with increases in 1976 and
1977. In Zone 2 the curve positions and averages for the outer stations show a
slow increase in numbers of forms; the inner stations of this zone well off
shore show an overall tendency for increase and for there to be more forms at
these stations than at the outer ones, conditions which have been true since
1971.
The tendency for increase in numbers of phytoplankton forms in Cook Plant
collections since 1971 is consistent with the observations of Stoermer and Yang
(1969, pp. 209 and 211) that phytoplankters have been introduced into Lake
Michigan in recent decades and that one of the effects of nutrient enrichment
from man's activities has been to make the planktonic environment more
accessible to forms that find their primary habitat in benthic assemblages.
There is no convincing evidence from this analysis that operation of the
Cook Plant since 1975 has had any effect on the local phytoplankton community,

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