Primary production in a kettle lake (Canada) was not driven by effective moisture over the last ~900 years
Bibliographic record
Abstract
Globally, lakes and reservoirs are vital sources of fresh water. In temperate zones like the Great Lakes region, Canada, it is not known if climate warming will increase or decrease effective moisture, or affect water availability. The links between effective moisture and primary production are also unclear. To test for possible linkages, we have reconstructed the ~900-year history of effective moisture and primary production in a small, kettle lake (Barry Lake, Ontario, Canada). To reconstruct the history of effective moisture at Barry Lake, we measured the carbon (δ13C) and oxygen (δ18O) isotope ratios of marl and shelly fauna in two ~900-year sediment core records, tightly constrained by radiocarbon and lead-210 dates. To reconstruct primary production, we analyzed the carbon (δ13CTOC) and nitrogen (δ15NTN) isotope ratios, total organic carbon to total nitrogen (TOC:TN) ratios and chlorophyll-a concentrations of the sediments. Analyses of n-alkane relative abundances further refined our understanding of the history of primary production in Barry Lake and confirmed the predominately autochthonous origin of the sediment organic matter. Relative to present conditions, we determined that effective moisture was lower during the Medieval Warm Period (MWP: AD 1000- 1300) and higher during the Little Ice Age (LIA: AD 1450- 1650). Despite these differences, primary production remained unchanged until AD ~1917. After AD ~1917, primary production accelerated, reaching levels unprecedented across the entire record. A 4 ‰ increase in δ15NTN is coincident with this rise in primary production. This change may be related to the introduction of organic fertilizer from nearby agricultural fields. A rise in the relative abundance of nC17 at AD ~1917 suggests that the proliferation of algae was responsible for the increase in primary production. Our findings suggest that primary production was insensitive to climate change on the scale of the LIA and MWP, but highly sensitive to nutrient loading. The fact that modern indicators of effective moisture are within the natural range of variation observed over the last ~900 years suggests that modern climate warming has not altered the hydrologic regime of Barry Lake beyond baseline conditions. Comparisons of our hydroclimatic record with similar records from the region confirm this finding. In short, our research demonstrates that, in small lakes like Barry Lake, primary production is primarily driven by nutrient loading rather than changes in effective moisture related to moderate oscillations in hydroclimate.
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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 | 0.001 |
| 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) | 0.002 | 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".