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

et al. (1971) list the species taken in the July survey of 1970.
Over time, the master lists provide a means of watching for changes in
the phytoplankton community. The master lists of 1972 (when the
settle-freeze method was adopted) through 1977 have been put to this use in
the section that follows.
Continued Increase of a New Diatom Species
The centric diatom, Cvclotella comensis, first appeared in Cook
Plalt phytoplankton collections in October 1975 and has been taken with
increasing regularity in the seasonal surveys since then. The record on
occurrences of C. comensis now stands:
1975 1976 1977
Jul. Oct. Apr. Jul. Oct. Apr. Jul. Oct
Number of
occurrences 0 24 13 6 35* 29 38** 3!

t.
9

Percent of
samples
containing it 0 66 33 15
Range of %
of sample 0- 0- 0 -populations 0 1.77 0.59 0.24
Mean % of
sample
populations 0 0.58 0.06 0.02
Number of
dominant or
codominant
occurrences 0 0 0 0
* Four stations omitted due to high seas.
-i Station SDC-4-1 was accidentally omitted

100
0.60 -25.80
6.52

74 100

100

0- 1.25- 0.27 -0.65 36.75 3.35
0.16 15.20 1.29

5

0 15

0

in this survey.

Cvclotella comensis is known from alpine lakes, Lake Superior, Lake
Huron and Saginaw Bay, as well as northern and central Lake Michigan. Aside
from the fact that it blooms in late summer or early fall, nothing is known
of the requirements or preferenda of this diatom. Previous collections of

26