Adaptive response of a marine «Chlamydomonas sp». to phosphorus limitation
Bibliographic record
Abstract
Global warming is predicted to increase stratification of the surface ocean and enhance nutrient-limitation of phytoplankton production by reducing vertical mixing.How phytoplankton might react to such increased resource deficiency is not well understood.This thesis reports the results of a long-term experimental study of the impact of phosphorus limitation on a model phytoplankton species.Four chemostat cultures of a marine Chlamydomonas (CCMP 222) were grown under phosphorus limiting conditions at steady state for 260 generations to assess adaptive responses to resource deficiency.Adapted populations derived from the chemostats had significantly faster rates of growth in low P medium, but grew more slowly on average than the ancestral population in the presence of high P concentrations.The adapted populations contained less phosphorus per unit of cell volume (mol P L -1 cell volume) as a result of two distinct strategies: in the first, cells increased in size and kept cellular phosphorus quota (mol P cell -1 ) constant, and in the second, cells decreased cellular phosphorus quota and kept cell size constant.Reduction in amount of phosphorus per unit of cell volume of all of the adapted populations caused a significant increase in cell surface area per unit of phosphorus (p < 0.05) compared to the ancestor, potentially allowing for faster uptake rates of the limiting resource relative to requirements and faster growth.The cellular C:P ratio of the adapted cells changed only very little relative to the ancestor.The results suggest that adaptation may partially offset increases in nutrient deficiency by altering phytoplankton elemental requirements and growth.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.003 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
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 teacher head, 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".