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 season to season were the same in both sets of stations. Parallelism of
the curves for inner and outer station groups in the operational years 1975
through 1977 has been as good as or better than in the preoperational years.
The placement of annual curves on the 7graphs shows in all zones either a
trend toward increasing diversity from 1972 through 1976 with no increase from
1976 to 1977 or (alternatively) an increase from 1972 through 1974 with a
horizontal trend since that year.
The meaning of these two trend possibilities is not now clear. Stoermer
and Yang (1969, p. 212) point out that in Lake Michigan there has been a trend
for diversity to increase with increasing eutrophication, rather than to
decrease as might be expected from theory; if the lower data from 1977 are
within normal annual variation, then increase due to eutrophication may be
continuing. Alternatively, if the efforts toward reduction of phosphorus input
to the lake are beginning to have effect, the upward trend due to
eutrophication may be being halted. Data from additional years will be needed
to clarify the question.
There is no evidence from our diversity studies thus far that operation of
the Cook Plant has adversely affected (lowered the diversity of) the local
phytoplankton community in the operational years 1975 through 1977. Instead,
the phytoplankton community has in the operational years continued to be more
diverse than it was in the preoperational years prior to 1974.
Inner-Outer Graphical Comparisons: Phytoplankton Redundancies
Redundancy values are derived from the diversity index of Wilhm and
Dorris (1968):
S
d = - Z (ni/n) log2 (ni/n)
i=1

42