Particulate trace metals & iron availability to phytoplankton in a changing Arctic Ocean
Bibliographic record
Abstract
This thesis, focusing on the Canadian Arctic Ocean, investigates the cycling of particulate trace metals, and the bioavailability of iron to phytoplankton in this rapidly changing ocean. Full depth profiles of particulate Al, Cd, Pb, P, V, Mn, Fe, Co, Cu, Zn and Ba were determined. Trace elements displayed various vertical distributions. Firstly, some elements had a strong lithogenic component (Al, Fe and V), and were characterized by a maximum at the surface. Indeed, their concentrations strongly correlated with each other across basins. Secondly, elements with a significant biogenic component (Cd and Cu) were characterized by a decrease in concentration with depth. Furthermore, preferential remineralization of P over Cd at shallow depths in numerous stations is reported. In some stations across basins, the molar ratio of particulate Cu and P approached a plateau at the meso- or bathy-pelagic zone, suggesting the presence of ammonium oxidizing archaea, which require Cu-dependent enzymes. Thirdly, Mn, a trace metal with a predominant redox cycle, showed a spike in concentration between 100-200 m, as well as a bottom enrichment. In the Canada Basin, we suggest interactions between the production of manganese oxide, cobalt oxide and barite by manganese oxidizing bacteria. \n The Arctic Ocean is experiencing the greatest decrease in seawater pH, as well as rapid ice melting which elevates light intensity in surface waters. To examine changes in Fe bioavailability to Arctic phytoplankton under a varying environment, two incubation experiments were conducted. After natural phytoplankton assemblages were acclimated to different light/CO2 treatments for one week, short-term Fe uptake assays were performed to assess the capability of phytoplankton to access Fe. Generally, Fe uptake capability was positively influenced by CO₂ level, and negatively impacted by light level in the incubations. These observations imply that high CO₂ has a significant negative effect on Fe bioavailability, while high light has a positive effect. Furthermore, when comparing future scenario (higher atmospheric CO₂ and underwater irradiance) with present-day conditions, the bioavailability of Fe to phytoplankton appeared to be similar.
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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 | 0.000 | 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 | 0.000 |
| 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 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".