Bloom development and phytoplankton succession in Lake Winnipeg: a comparison of historical records with recent data
Bibliographic record
Abstract
Over the past 40 years, hydroelectric, agricultural and urban watershed development and changing hydrology have transformed Lake Winnipeg into a highly eutrophic reservoir with annual outbreaks of widespread surface algal blooms, shoreline and net fouling, and concerns with intermittent cyanotoxin production. To provide a better understanding of the magnitude of these changes and the major causes, we examine long-term increases in phytoplankton biomass and shifts in phytoplankton species dominance in the context of both in-lake and watershed processes. We compare phytoplankton and water quality data from early (1969) and recent (1994–2007) lake-wide surveys, and information from paleolimnological analysis of sediment cores and satellite remote sensing. Our results demonstrate a recent and dramatic rise in severe algal blooms and increased dominance of cyanobacteria beginning in the mid-1990s, coincident with a large increase in phosphorous loading to the lake. Distinct increases in sediment core accumulation of nutrients and chlorophyll, cyanobacteria and diatom microfossils coincided with hydroelectric and agricultural development, increased Red R discharge and shifts in water transparency patterns across the lake. There has been a dramatic increase in phytoplankton biomass, accompanied by marked shifts in seasonal community composition. Spring diatoms blooms are of shorter duration and increasingly dominated by more eutrophic diatom taxa while summer blooms show reduced taxonomic diversity and an increased predominance of nitrogen-fixing cyanobacteria. Satellite images showed annual development of vast summer surface blooms, mainly in the north basin, with chlorophyll highest in regions of relatively low suspended sediment concentration and high transparency. There is an increasing dominance of potentially toxic cyanobacteria taxa and high levels of microcystins in nearshore samples of surface blooms. The combined effects of nutrient increases, algal species shifts and toxin production represent a potential threat to the sustainability of ecosystem function and productivity.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".