Table 1. Winter nitrification rates and associated data for this study (under ice cover) and for Lake St. George (near surface at 2 m depth, under ice cover; [21]); for surface nitrification rates in Lake Croche (ice-covered; [38]); and for surface estimates of nitrate accumulation in Wisconsin lakes part of the North Temperate Lakes Long-Term Ecological Research (NTL- LTER) study (ice-covered, 30 years of accumulated data; [19]).
Values below limits of quantitation (LOQ) for nitrification rates are reported, including negative values (following [40]) and sample-specific LOQ (as described in Methods and calculated as per [43,44]) are reported.
| Location | Nitrification Rate | Nitrification Rate LOQ | Ammonium | Nitrate | Oxygen | pH | Specific Conductance | N2O | CH4 | Date |
|---|---|---|---|---|---|---|---|---|---|---|
| (μg N L-1d-1) | (μg N L-1d-1) | (μg N L-1) | (μg N L-1) | (mg L-1) | (μS cm-1) | (% Saturation) | (% Saturation) | |||
| Winter Ice Cover | ||||||||||
| Blackstrap Reservoir | -1.7* | 4.9 x 10−3 | <86** | <57** | 7.6 | 5.7 | 1237 | 134.8 | 97.6 | 05-Mar-15 |
| Buffalo Pound Lake | -4.0* | 4.0 x 10−3 | <86** | <57** | 12.5 | 7.6 | 1185 | 184.8 | 246.1 | 10-Mar-15 |
| Echo Lake | 1.2 | 7.0 x 10−2 | 366 | 171 | 8.3 | 8.6 | 1726 | 213.7 | 241.5 | 02-Feb-16 |
| Katepwa Lake | 32 | 2.7 x 10−2 | <86** | 620 | 9.9 | 6.8 | 1566 | 636.2 | 414.9 | 10-Mar-15 |
| Lenore Lake | -1.7* | 6.8 x 10−3 | 263 | 200 | 7.5 | 8.4 | 3758 | 253 | 259.3 | 25-Mar-15 |
| Mission Lake | 2.1 | 1.1 x 10−1 | 452 | 129 | 7.6 | 8.5 | 1790 | 195.4 | 282.1 | 02-Feb-16 |
| Pasqua Lake | 870.7 | 3.2 x 10−3 | 1650 | 532 | 8.6 | 7.3 | 2180 | 671 | 178 | 10-Mar-15 |
| St. Denis Pond 1 | -0.042* | 3.2 x 10−3 | <86 | <57** | 10 | 6.9 | 1536 | 132.9 | 1109.3 | 16-Apr-15 |
| St. Denis Pond 5338 | -0.044* | 3.1 x 10−3 | <86** | <57** | 15 | 8.2 | 2963 | 135.7 | 1027.6 | 16-Apr-15 |
| St. Denis Pond 90 | -0.1* | 3.6 x 10−3 | <86** | <57** | 14.5 | 8.6 | 1648 | 109.1 | 1650.2 | 16-Apr-15 |
| St. Brieux Lake | 110 | 1.8 x 10−3 | 528 | 310 | 2 | 7.8 | 3589 | 515.6 | 579.8 | 25-Mar-15 |
| ELA Lake 227 | 0.14 | 4.6 x 10−5 | 516 | 314 | 5.84 | 6 | 26 | NA | NA | 14-Mar-16 |
| ELA Lake 239 | 0.022 | 1.2 x 10−4 | 636 | 145 | 13.7 | 6.6 | 30 | NA | NA | 14-Mar-16 |
| Lake St. George, Ontario | 22.8 | NA | 467 | 540 | 9.3 | NA | NA | NA | NA | 27-Feb-80 |
| Lake St. George, Ontario | 12.2 | NA | 390 | 550 | 8.1 | NA | NA | NA | NA | 06-Mar-80 |
| Lake St. George, Ontario | 4.5 | NA | 65 | 1230 | 1.3 | NA | NA | NA | NA | 24-Feb-82 |
| Lake St. George, Ontario | 1.3 | NA | 39 | 1191 | 0.8 | NA | NA | NA | NA | 0Mar-82 |
| Lake St. George, Ontario | 10.5 | NA | 490 | 210 | 10.2 | NA | NA | NA | NA | 09-Feb-83 |
| Lake Croche | 4.7 | NA | 38 | 19 | NA | NA | NA | NA | NA | 01-Feb-12 |
| Lake Croche | 2.6 | NA | 38 | 27 | NA | NA | NA | NA | NA | 01-Mar-12 |
| Allequash Lake, Wisconsin | 0.58ƒ | NA | NA | NA | NA | NA | NA | NA | NA | 30 years of data |
| Big Musky Lake, Wisconsin | 0.55ƒ | NA | NA | NA | NA | NA | NA | NA | NA | 30 years of data |
| Crystal Lake, Wisconsin | 0.39ƒ | NA | NA | NA | NA | NA | NA | NA | NA | 30 years of data |
| Sparkling Lake, Wisconsin | 0.45ƒ | NA | NA | NA | NA | NA | NA | NA | NA | 30 years of data |
| Trout Lake, Wisconsin | 0.87ƒ | NA | NA | NA | NA | NA | NA | NA | NA | 30 years of data |
*Indicates less than associated Limits of Quantitation for that sample.
**Indicates that sample concentrations were below method detection limits of 86 and 57 μg N L-1 for NH4+ and NO3–, respectively. NA indicates data were not reported.
ƒIndicates data from [6] are estimated from winter nitrate accumulation and likely underestimated.