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

waters, rather than to plant operation.
Coccoid blue-greens showed notable fall increase in preoperational 1974
(due at least in part to the counting change then) and this pattern has
continued since in both inner and outer station groups. There is no clear
evidence of any plant operation effect.
The changes in mean abundances of the other catagories have been:
Flagellates Increasing trend since 1970
Pennate diatoms " " TI It
Centric diatoms " " i
Total algae VI VI t v
Desmids Essentially no change
Filamentous greens " " "
Other algae V I it
Coccoid greens t " "t
The trends toward increasing abundances show in both station sets and
all three depth zones and are attributable to the lake's eutrophication,
rather than to effects of Cook Plant operation.
T-tests of significance of difference between seasonal mean densities of
nine algal categories and total algae at inner and outer stations in each of
the three depth zones during the years 1970 through 1977 have been
performed. Of 591 paired comparisons, significant differences between mean
densities at inner and outer stations were found in only 36 cases; these
amount to 6% of the comparisons.
Summarizing by categories, with the numbers of significant differences
in operational years underlined, gives: filamentous greens 0 + Q.; coccoid
blue-greens 0 + J; desmids 2 + Q.; filamentous blue-greens 0 + 4; coccoid
greens 2 + j; centric diatoms 2 +.; pennate diatoms 3 + J; total algae 2 +
Z; other algae 5 + i; and flagellates 4 + 3. Only in the filamentous
blue-greens were all the significant differences in the operational years;
however, three of the four cases were in offshore Zone 2. There is no

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