Table 1.
Mean values for most abundant Cyanophyta genera, as well as several biological, chemical, and physical parameters measured from the Lake Mendota Deep Hole location between the years 1995–2010.
| Pre-toxic | Toxic | Post-toxic | K-W | |
|---|---|---|---|---|
| CYANOPHYTA | ||||
| Total biovolume (μm3 mL−1) | 110,000 | 26,00,000 | 920,000 | a, b, c |
| Aphanizomenon (μm3 mL−1) | 85,000 | 17,00,000 | 560,000 | a, b, c |
| Microcystis (μm3 mL−1) | 4600 | 440,000 | 150,000 | a, b, c |
| Oscillatoria (μm3 mL−1) | 1100 | 110,000 | 68,000 | a, b, c |
| Aphanothece (μm3 mL−1) | 3900 | 100,000 | 17,000 | a, b, c |
| Synechococcus (μm3 mL−1) | 1900 | 4400 | 3500 | a, c |
| Synechocystis (μm3 mL−1) | 1600 | 1200 | 1700 | |
| NUTRIENTS | ||||
| TC (mg L−1) | 52.2 | 45.9 | 50.3 | a, b, c |
| TN (μg L−1) | 1470 | 980 | 1060 | a, b, c |
| TP (μg L−1) | 110 | 50 | 110 | a, b |
| TC:TN (by mass) | 37 | 51 | 49 | a, c |
| TC:TP (by mass) | 515 | 1230 | 543 | a, b |
| TN:TP (by mass) | 15 | 23 | 12 | a, b, c |
| DOC (mg L−1) | 5.9 | 6.1 | 5.8 | |
| DIC (mg L−1) | 46.4 | 40.1 | 44.2 | a, b, c |
| N + N (μg L−1) | 600 | 160 | 60 | a, b, c |
| NH+4 (μg L−1) | 210 | 20 | 340 | a, b, c |
| DRP (μg L−1) | 80 | 10 | 80 | a, b |
| DIC:DIN (by mass) | 61 | 1331 | 222 | a, b, c |
| DIC:DRP (by mass) | 808 | 17260 | 1811 | a, b, c |
| DIN:DRP (by mass) | 14 | 30 | 7 | b, c |
| DRSi (μg L−1) | 1190 | 1560 | 2000 | a, b, c |
| PHYSICAL | ||||
| Water temp (°C) | 8.8 | 23.1 | 12.9 | a, b, c |
| Dissolved oxygen (mg L−1) | 12.0 | 8.6 | 9.0 | a, c |
| pH (–log [H+]) | 8.4 | 8.9 | 8.4 | a, b |
| Secchi (m) | 5.2 | 2.4 | 3.3 | a, b, c |
| Lake number (unitless) | 0.57 | 3.08 | 0.38 | a, b |
| Wedderburn number (unitless) | 1.23 | 5.54 | 1.80 | a, b |
| Schmidt stability (J m−2) | 66 | 537 | 72 | a, b |
| u* (m s−1) | 0.015 | 0.015 | 0.016 | |
| Boyancy frequency (N2, s−2) | 0.001 | 0.005 | 0.002 | a, b |
| Mixed layer depth (Zmix, m) | 12.3 | 7.5 | 16.3 | a, b, c |
All of the data were split into three time periods (phases) based on the 2009–2011 microcystin data. The toxic phase represents the period when mean microcystin concentrations were significantly greater than 1 μg L−1 (days 170–250). Significance between the phases was tested using a Kruskal–Wallis test (K–W; p < 0.05). a, significant difference between pre-toxic and toxic phases; b, significant difference between toxic and post-toxic phases; c, ignificant difference between pre-toxic and post-toxic phases.