Seasonal dynamics of autotrophic and heterotrophic plankton metabolism and P<sub>CO2</sub> in a subarctic Greenland fjord
Bibliographic record
Abstract
We measured net planktonic community production (NCP), community respiration (CR), and gross primary production (GPP) in September, February, and May in a subarctic Greenland fjord influenced by glacial meltwater and terrestrial runoff. Potential controls of pelagic carbon cycling, including the role of terrestrial carbon, were investigated by relating surface‐water partial pressure of CO2 (PCO2), NCP, GPP, and CR to physicochemical conditions, chlorophyll a (Chl a) concentration, phytoplankton production, inventories of particulate (POC) and dissolved organic carbon (DOC) and vertical flux of POC. The planktonic community was net heterotrophic in the photic zone in September (NCP 5 ‒21 ± 45 mmol O2 m‒2 d‒1) and February (NCP 5 ‒17 mmol O2 m‒2 d‒1) but net autotrophic during a developing spring bloom in May (NCP 5 129 ± 102 mmol O2 m‒2 d‒1). In September, higher temperatures, shorter day lengths, and lower Chl a concentrations compared with May caused increased rates of CR, lower GPP rates, and net heterotrophy in the photic zone. The GPP required to exceed CR and where NCP becomes positive was low (in May: 1.58 ± 0.48 µmol O2 L‒1 d‒1 and September: 3.06 ± 0.82 µmol O2 L‒1 d‒1) and in the range of open ocean values, indicating that allochtonous carbon did not stimulate CR. The PCO2 in the surface water was below atmospheric levels (September average 25.0 ± 0.71 Pa, February 35.4 ± 0.40 Pa, and May 19.8 ± 1.21 Pa), rendering the ecosystem a sink of atmospheric CO2. NCP was identified as an important driver of surface PCO2 , with high rates of autotrophy and vertical export of POC reducing surface PCO2 during summer. In winter, net heterotrophy added CO2 to the water column, but this postive effect on PCO2 was balanced by simultaneous cooling of the water column, which decreased PCO2 because of increased solubility of CO2. High autochthonous production implies a relatively limited influence of allochthonous carbon on pelagic carbon balance and CO2 dynamics in the fjord.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".