Table 24-4. Comparisons of Phytoplankton in the Microcosms and in 
Narragansett Bay at the GSO Dock During 
the Replicability Experiment. 
NOTE: Similarity indices for the comparison of bay with all microcosms and 
for microcosm 3 with all other microcosms. Shannon index of diversity (H) for 
the microcosms and the bay. 
Similarity Index (S) 
Shannon Index (H) 
Bay-Tank 
Comparison 
Tank 3-Tanks 
Comparison 
Tank 
Bay 
Date 
Mean 
Range 
Mean 
Range 
Mean 
Aug. 
16 
0.379 
0.267-0.485 
0.608 
0.533-0.710 
0.263 
0.248 
30 
0.289 
0.143- 0.944 
0.617 
0.500-0.800 
0.021 
0.270 
Sept. 
13 
0.442 
0.267-0.640 
0.445 
0.261-0.593 
0.247 
0.270 
20 
0.325 
0.111-0.552 
0.398 
0.222-0.552 
0.327 
0.424 
27 
0.185 
0.074-0.333 
0.328 
0.231-0.581 
0.288 
0.093 
Oct. 
12 
0.373 
0.200-0.500 
0.171 
— 
18 
0.262 
0.133-0.429 
0.308 
0.125-0.571 
0.048 
0.520 
27 
0.286 
0.190-0.545 
0.458 
0.316-0.667 
0.209 
0.391 
Nov. 
8 
0.584 
0.421-0.696 
0.683 
0.452-0.824 
0.524 
0.695 
15 
0.642 
0.571-0.727 
0.612 
0.516-0.769 
0.441 
0.525 
22 
0.584 
0.457-0.667 
0.671 
0.545-0.824 
0.586 
0.795 
29 
0.639 
0.208-0.757 
0.678 
0.345-0.762 
0.471 
0.769 
Dec. 
6 
0.660 
0.467-0.788 
0.669 
0.588-0.757 
0.558 
0.810 
14 
0.549 
0.483-0.628 
0.584 
0.455-0.714 
0.592 
0.933 
22 
0.530 
0.414-0.648 
0.584 
0.455-0.709 
0.599 
0.807 
28 
0.620 
0.480-0.743 
0.536 
0.428-0.667 
0.607 
0.890 
Mean 
0.465 
0.535 
0.372 
0.563 
Std. Dev. 
±0.163 
±0.130 
±0.201 
±0.270 
While we do not have concurrent data on nutrients and chlorophyll from 
more than one station in Narragansett Bay, the results of a year-long survey at 
13 stations in the bay taken in 1972-73 are available. Data from three of these 
in the lower west passage of the bay are shown in Figure 24-5. The data set 
from the bay is in most respects similar to that from the MERL microcosms. 
Chlorophyll concentrations indicated a bloom in November in both the tanks 
and the bay which did not occur in 1972. Ammonia concentrations in the 
microcosms tended to be higher than in the bay, but mean values generally fell 
369 
