Interactive effects of copper and calcium in Daphnia pulex
Bibliographic record
Abstract
Many freshwater habitats around the world suffered dramatic water chemistry changes over the last century mostly due to anthropogenic activities, including an overall reduction in pH due to high sulfur emissions and unsustainable forestry practices. One consequence of this change in water chemistry is a drop in available calcium concentration, which creates problems for aquatic organisms that rely on dissolved calcium to build their exo- or endoskeletons and reinforce their carapace during regular molts. Daphnia populations in shield lakes in northern Ontario are also exposed to other stressors, including copper, which persists at high concentrations in many of these freshwater lakes and ponds due to mining and other human activities. Copper toxicity on animals is influenced by the availability of other competing ions, such as calcium. Using our newly developed high throughput toxicity screening system, we show that mortality of Daphnia pulex increases with exposure to low calcium (0.05 mg L-1) and high copper (300 µg L-1). When these two stressors were combined, we found that copper was less toxic at high calcium concentrations, indicating a protective effect of calcium against copper toxicity. We then established basic calcium uptake kinetics in D. pulex using radioactive tracer 45Ca and provide evidence that copper, at environmentally relevant concentrations, competes with calcium uptake based on Km and Vmax. Our data show that both calcium decline and copper increase in aquatic ecosystems may negatively impact natural Daphnia populations, and that interactions between these two metals may occur in natural environments that result in fitness consequences for zooplankton.
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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 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".