The phytoplankton of the Cook Plant monthly minimal surveys during the preoperational years 1972, 1973, and 1974 / by John C. Ayers.

both temporally and spatially, in total numbers of cells collected. For
each month, the abundances measured at the inshore stations were compared to
those at the reference stations using a two-sample t-test. The resulting
t-statistics are given in Table 10. None of the differences were significant
at the 5% level. Both reference stations showed in 1974 a tenfold variation
in total cells while the greatest variation observed in the Cook inshore
stations was fivefold at station DC-O.
The number of forms collected ranged from 23 to 70 but most were in the
forties and fifties.
If the relation of number of forms to mean number of cells per form is
considered a measure of diversity, the data of Table 10 indicate that fairly
diverse populations were sampled (relatively large numbers of forms with
relatively few individuals per form). Poorly diverse populations, indicated
by few forms with many cells per form, were not observed.
CONCLUSIONS
During the field season of 1974, 256 phytoplanktonic forms were collected
from the main group of monthly survey stations directly in front of the Cook
Plant, and 49 additional forms were recorded from the two inshore reference
stations added in 1974.
There were 66 forms from the main monthly survey stations that attained
to the arbitrary "abundant" category in 1974, compared to 50 in 1973 and 32 in
1972. The increase in abundant forms was investigated to see if it represented a progressive increase in the size of phytoplankton populations in the
Cook Plant region; no clearly defined increase in population sizes could be
found. The increased numbers of abundant forms are attributed to increased
skills of our phytoplankton analysts as evidenced by a decrease in numbers of
unidentified "sp." and "spp." categories from 48 in 1973 to 38 in 1974.
Forms which were numerically dominant in at least one month of 1974 were:
flagellates, FragiZaria crotonensis, Synedra fiZiformis, and the blue-green
alga Gomphosphaeria lacustris which was dominant in August through October.
The latter, a non-nuisance-forming species common in offshore waters, was
apparently brought inshore by onshore winds that preceded the last three
surveys.

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