Long-term decline in stream total phosphorus concentrations: A pervasive pattern in all watershed types in Ontario
Bibliographic record
Abstract
Cultural eutrophication of the Great Lakes resulted in actions to reduce phosphorus loading beginning in the 1970′s. Despite these measures, a resurgence of harmful algae blooms began in the 1990s. Non-point sources and changing agricultural practices are frequently cited as contributing to this resurgence. We examined changes in total phosphorus concentrations ([TP]) and several other water quality parameters from April through November from 1979 to 2011 using 56 streams throughout Ontario, including agricultural, undeveloped, urban, and mixed-use watersheds. Growing season median [TP] was not significantly different among stream types, but decreased in 32 of the 56 sites; only one urban site increased. There were weak differences among land uses; mixed sites typically had the highest [TP] and steepest declines. Soluble reactive P concentration [SRP] decreased at 12 sites, and increased at one agricultural and three urban sites. Where trends were significant, suspended solids typically decreased, while [Cl−] and alkalinity typically increased. As adequate winter data were not available and there may have been changes in the seasonal distribution of high flow during the period we studied, the changes we observed in median growing season [TP] may not reflect changes in loading. However, seasonal discharge trends were not significant except for one site with a decreasing trend in spring discharge. Possible mechanisms for pervasive downward trends in TP include improved rural and urban land use practices, reduced acid precipitation, increased nitrogen availability in terrestrial ecosystems, and ongoing forest regrowth after initial clear-cutting.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".