A palaeolimnological record of diatom-community dynamics and late-Holocene climatic changes from Prescott Island, Nunavut, central Canadian Arctic
Bibliographic record
Abstract
Palaeolimnological analyses from Lake PW03, a small, dilute lake on crystalline bedrock on Prescott Island, Nunavut, Canada (73°07′ N, 96°41′ W, 243 m a.s.l.), provide a sensitive record of the impacts of Holocene climatic change on diatom communities. A high-resolution sequence from 3500 cal. BP to present indicates that a significant change in diatom assemblages takes place at 2300 cal. BP, when alkaliphilous fragilarioids and planktonic taxa are replaced by benthic, epiphytic and acidophilous diatoms. These changes coincide with the onset of neoglacial cooling and likely reflect more persistent ice-cover and associated acidification of lake water. Maximum diatom species richness occurs during this period of transition. Dense bryophyte communities in the littoral zone provide habitats to sustain diatom production even under the cooler conditions following 2300 cal. BP. The concentration of diatom valves declines at 500 cal. BP, coincident with cooling at the time of the `Little Ice Age', and minor changes in species composition take place at that time. The sediments deposited over the past 150 years show modest increases in fragilarioids and planktonic diatoms, in response to a longer ice-free season under a warmer climate. Diatom valve production increases significantly in these recent sediments but increases in diversity are relatively small. Diatom diversity, production and the species composition of diatom communities do not change simultaneously in response to climatic changes.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".