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

preoperational 1974 (due in part to a change in counting method that year) and
this pattern has been characteristic in the years since, not so pronounced in
1976, and very pronounced in 1977. It is to be noted that the increases in
October 1977 were greater in the outer stations of Zones 1 and 2. Beginning in
preoperational 1974 and continuing since, these fall increases are attributed
to lake eutrophication, rather than to plant operation.
Coccoid green algae (Fig. 8F) have been present in variable abundances of
a few hundred cells per ml in each survey of the study area. In all but one of
the operational surveys the abundances of these algae were at levels which had
been observed in the preoperational years; the exception was at the inner
station group of Zone 2 in July 1977 when abundances were somewhat higher than
previously seen. These being offshore stations where the plant plume is not
expected, the high of that month is attributed to some lake effect, not plant
operation.
Flagellates (Fig. 8G) in both station groups and all three depth zones
continued in 1977 the trends of steadily increasing abundances that had been
going on since 1971. The trends show no evident relationship to the startup of
Cook Plant. We consider them to be effects of eutrophication, and note with
interest that Stoermer, Bowman, Kingston, and Schaedel (1974, p. 366)
hypothesize that the great abundances of flagellates in Lake Ontario may be
related to elevated organic loadings.
Pennate diatoms (Fig. 8H), like the flagellates, have shown in all depth
zones and in both station groups steadily rising trends in their abundances.
Their spring abundances have been generally increasing since 1973; their summer
"crashes" in numbers have not been lower than they attained in preoperational
years; and their fall abundances have been generally increasing since 1973. In
these conditions among the pennates we see no effect of Cook Plant operation,

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