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Figure 4
Set-up:
Changes in both phosphorus and algal chlorophyll (an estimate of the total amount of algae - more info) are shown for the four lake sites in this graph. Phosphorus is scaled along the bottom of the graph while chlorophyll is scaled on the left axis. Both are shown in micrograms per liter (same as parts per billion). The solid circles represent the median values from prior to and after treatment plant upgrade, with arrows indicating the direction of change (a shift to the left means less phosphorus, while a shift downward equates to less chlorophyll). The open circles are phosphorus and chlorophyll data from 18 sites across the lake. The diagonal line reflects the overall relation between phosphorus and chlorophyll based on lake-wide data.
Interpretation:
Phosphorus decreased at all four lake sites as indicated by the arrows pointing towards the left. Reductions in algal chlorophyll were evident at three of four sites, though changes were small. The average reduction for sites IV, VI and VII was around 12%. Only the decrease at Site VI was statistically significant.
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