Phytoplankton of the seasonal surveys of 1976, of September 1970, and pre- vs. post-operational comparisons at Cook Nuclear Plant / John C. Ayers.

and 1976. Coccoid blue-greens showed increased numbers in 1975 and 1976, but
the increase first appeared in preoperational 1974 and has not been
particularly higher since.
The changes in mean abundances of the other major groups in both station
groups and all three depth zones have been:
Desmids essentially no change
Filamentous greens " " "I
Other algae " "t
Coccoid greens " " "
Flagellates increasing trend since 1970
Pennate diatoms " " " "
Centric diatoms i" " " "i *
Total algae i" " " "i
* Very high values in zone 0 in 1972 and 1973 and in zone 1 in 1973.
On the whole, the trends toward higher abundances are attributable to
the lake's eutrophication since 1970, rather than to effects of plant
operations.
Two-sample t-tests of significance of differences between seasonal
mean abundances of total algae at treatment and control station groups in
shallow (zone 0) and deeper (zone 2) water, showed significant differences
(at the.05 level) between treatment and control station group means only in
the spring of 1972 when significant differences occurred in both depth zones.
The Wilhm and Dorris diversity indices of phytoplankton collections
taken during the seasonal surveys of 1970 - 1976 have tended to become higher
since 1972. The increases have taken place in both inner and outer station
groups and in all three depth zones. The higher indices indicate a more
diverse phytoplankton community now than in the earlier preoperational years.
The increased diversity is attributed to the eutrophication of the lake,
rather than to plant operation.
Values of phytoplankton redundancy for the seasonal surveys of 1970 -

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