PCO2 method for measuring photosynthesis and respiration in freshwater lakes
Bibliographic record
Abstract
A method for measuring net community photosynthesis and respiration based on changes in PCO2 is described. Samples were incubated in serum stoppered bottles and successive pCO2 measurements taken from the bottle headspace. At the end of the incubation, samples were acidified with concentrated phosphoric acid and total dissolved inorganic carbon (DIC) was determined. Alkalinity was calculated from PCO2 and DIC. Alkalinity was assumed to remain constant for the duration of the experiment so that DIC could be calculated from PCO2 and alkalinity for each measurement. Uptake rates were calculated from the slope of Δ DIC over time. The assumption of alkalinity change being <15% of photosynthesis was tested using axenic chemostat cultures of Chlamydomonas reinhardtii at different nitrogen:phosphorus ratios. For all cultures, alkalinity change represented <10% of particulate carbon turnover. Alkalinity-adjusted rates were found to be not significantly different from non-alkalinity-adjusted rates. Incubations from Lakes 227 and 240 in the Experimental Lakes Area and from Station 928 in Lake Malawi typified photosynthesis–irradiance curves. 14C uptake in Lake Malawi was found to be closer to gross community photosynthesis than to net photosynthesis. Field incubations using this method were 6–11 h and required the constant presence of a researcher; however, the method can be automated.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.004 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.012 | 0.008 |
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".