It's a good thing that severely hypoxic salmon (<i>Salmo salar</i>) have a limited capacity to increase heart rate when warmed
Bibliographic record
Abstract
With climate change, fish are facing rising temperatures, an increase in the frequency and severity of heat waves and hypoxia, sometimes concurrently. However, only limited studies have examined the combined effects of increases in temperature and hypoxia on fish physiology and survival. We measured the cardiorespiratory physiology of 12°C-acclimated Atlantic salmon when exposed acutely to normoxia [100% air saturation (sat.)] versus 75 and 50% air sat., and then warmed to their critical thermal maximum (CTmax) at 2°C h-1. Fish exposed to 50% air sat. became bradycardic, were unable to increase heart rate (fH) when warmed, and had lower values for metabolic scope and CTmax (21.3 vs 26.1°C in normoxic fish). The effects of 75% air sat. on cardiorespiratory parameters and CTmax were intermediate. We then used atropine (1.2 mg kg-1) and 8-cyclopentyltheophylline (CPT; 50 nmol kg-1) to investigate what role(s) cholinergic tone on the heart and cardiac adenosinergic effects, respectively, play in preventing severely hypoxic salmon (40% air sat.) from increasing fH when warmed. CPT had no/limited effects on salmon cardiorespiratory parameters and thermal tolerance. However, atropine increased fH in hypoxic fish and allowed it to rise with temperature, and this resulted in salmon that were much less tolerant to warming. Collectively, these results: (1) show that fish in severely hypoxic environments will be very susceptible to climate change-associated heat waves; and (2) suggest that cholinergic tone on the heart is not removed when severely hypoxic fish are exposed to rising temperatures to protect the heart's pumping capacity.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".