Abundance of Antarctic picophytoplankton and their response to light and nutrient manipulation
Bibliographic record
Abstract
The response of Antarctic picophytoplankton to experimental light and nutrient manipulation was tested in a large-scale mesocosm experiment in an iron-rich coastal location in the Bransfield Strait (Johnson Cove) during the austral summer of 2000.The experiment consisted of 8 mesocosm units (25 m 3 ), shaded with screens to provide a light gradient (target irradiance 100, 50, 25 and 10% of the ambient light field).A set of 4 mesocosms encompassing the different light treatments was initially run with the ambient nutrient concentrations and in the remaining 4 mesocosms, ammonium (NH 4 Cl) was added together with phosphate (KH 2 PO 4 ) and silicate (Na 2 SiF 6 ) for the first 11 d of the experiment (Phase I).A second manipulation of light and nutrient (Phase II) was done to confirm the results obtained on Day 16 of the experiment, when the mesocosms shaded to 25% of the ambient light were exposed to full ambient light, and ammonium, was added to both of the mesocosms already receiving 100% ambient light.The importance of light availability was evident in the increased abundance of picophytoplankton with increased irradiance, the response being non linear, with the abundance at full ambient irradiance being comparable, or lower, than that at 50% of the ambient irradiance.There was, in addition, an interaction between light availability and nutrient supply as evidenced by the increased picophytoplankton abundance during the early part of the experiment, with increased nutrient availability in mesocosms exposed to 50 and 100% ambient light, and not in those shaded to 10 and 25% ambient light.The response of photosynthesis to irradiance (P-I curves) showed a strong response to nutrient additions, with extremely high specific photosynthesis rates in the mesocosm with increased nutrient availability and exposed to full ambient light.The response was close to the theoretical maximum possible and provides ample evidence that nutrient additions, particularly ammonium, contribute to the optimum photosynthesis by picophytoplankton in the iron-rich Antarctic coastal waters studied here.
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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 | 0.001 |
| 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".