RESULTS AND DISCUSSION

The results of the three-factor Pareto analysis for the three arcellaceans and the foraminifera are included as Figure 2. This graph indicates that in the case of Centropyxis aculeata, oxygen is the most important variable, while increasing salinity would have decreased the population abundance. This is similar to results obtained in previous research, using multi-variate analysis, where C. aculeata was found to be tolerant of salinities up to about 5‰. In addition, past research has shown that Centropyxids are excellent indicators of stressed environments with neutral pH conditions (5.5 - 7.5), and this is mirrored by Pareto analysis results, indicating that when pH is changed beyond this range, Centropyxis aculeata does less well, especially in combination with changes in salinity above 5‰.

Difflugia corona decreased in abundance when salinity increased and was tolerant of changes in pH. Previous research indicated that Difflugids in general are intolerant of much salinity, but certain of these arcellaceans have the ability to indicate their environments with respect to pH. Research in Lake Winnipegosis has shown that D. corona tends to dominate assemblages in an environment with raised pH (8.0) and low salinity (0 - 3‰), which is again mirrored by the results of the Pareto analysis.

Populations of Cribroelphidium gunteri, a euryhaline foraminifera, were abundant under conditions of high oxygen content and high salinity, and found to be able to adapt to changing conditions of salinity in northern Lake Winnipegosis. This is also indicated by the results of the three factor Pareto analysis, where C. gunteri is tolerant of changes in oxygen and salinity, but not pH.

The arcellacean, Lagenodifflugia vas, was not sensitive to an increase in the three variables tested by Pareto analysis. This is what was expected, as previous research in Lake Winnipegosis indicated that L. vas was able to discriminate its environment under high pH (8.3), brackish (0 - 3‰) and variable oxygen conditions.

The Excel™ macro has the capability of analyzing three, four and five variable systems. Updates will also be available at: http://www.carleton.ca/~jcheetha/pareto. [PE Note: To get the macro, click on the file name. The Internet browser (Netscape, Explorer, etc.) will save the file (MACRO.XLS) or open it in a specified application.]

In order to use the macro, set up a number of test runs with variable information set as high (H) or low (L), and enter the data as indicated in Table 3. For instance, in the three variable Pareto Analysis, eight runs need to be set up with run #1 having high values for all variables.