Documenting the History of Oxygen Depletion in Lake St. Croix, Minnesota, Using Chironomidae Remains in the Sedimentary Record
Bibliographic record
Abstract
Lake St. Croix is a natural impoundment located at the southern end of the St. Croix River. Land use changes since European settlement (c. 1850) have resulted in nutrient runoff, eutrophication, and periodic oxygen depletion in the hypolimnion of Lake St. Croix. Establishing sound lake management practices requires knowledge of historical conditions obtained through paleoecological studies. Remains of non-biting midges (Insecta: Diptera Chironomidae) in lake sediments have been shown to be reliable indicators of past hypolimnetic oxygen conditions. Cores from two sub-basins in the lake were collected in 2006. Midge analysis indicated that shifts in species assemblages correspond to the times of land use change. Chironomus and Procladius, which are tolerant of low oxygen levels, increased in relative abundance as land use changes adversely impacted the St. Croix River’s watershed. Volume-weighted hypolimnetic oxygen concentrations were estimated using a transfer function developed for southern Ontario. Mean post-settlement chironomid reconstructed average volume-weighted hypolimnetic oxygen values were 0.73 mg/L lower than mean pre-settlement values for sub-basin 1, near Prescott, WI and 0.45 mg/L lower for sub-basin 3, near Lakeland, MN. These results indicate that oxygen depletion has occurred in the lake since the time of European settlement, and are supported by increases in the relative abundance of eutrophic midge bioindicators and the decrease in relative abundance of bioindicators of less productive conditions since the 1850s. This study, in conjunction with other historical and paleoecological studies of Lake St. Croix, provides historical data for setting management goals and strategies for Lake St. Croix.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".