Characterization of alkaline phosphatase activity in the North and South Pacific Subtropical Gyres: Implications for phosphorus cycling
Bibliographic record
Abstract
We characterized alkaline phosphatase (AP) activity (APA) and report AP kinetic parameters in the North and South Pacific Subtropical Gyres (NPSG and SPSG, respectively) to evaluate the relative importance of APA in dissolved organic P (DOP) remineralization. APA potential hydrolysis rates were low but measurable (0.10 ± 0.06 nmol L−1 h−1, n = 12, and 0.13 ± 0.08 nmol L−1 h−1, n = 6) in surface samples from the NPSG and central SPSG, respectively. When compared to dissolved inorganic P (DIP) uptake rates, the potential utilization of DOP by APA may be important for microbial communities in these oligotrophic habitats. Assuming an upper (80%) and a lower (10%) fraction of the DOP to be AP‐hydrolyzable, APA could represent 25% ± 18% (n = 11) and 4% ± 3% (n = 11) of the DIP uptake, respectively, in surface waters of the NPSG and 147% ± 86% (n = 6) and 20% ± 12% (n = 6), respectively, in surface waters of the central SPSG. The ratio of APA to DIP uptake was significantly larger in the SPSG compared to the NPSG despite having higher DIP and lower DOP. The half‐saturation constant (Km) was in the range of DOP concentrations measured in the two gyres, meaning that microorganisms can adjust their DOP utilization according to DOP availability. Dissolved APA was a large fraction of total APA in the NPSG, contributing between 12% and 100% (41 ± 23%, n = 23) of total APA at Sta. ALOHA. Utilization of the AP‐hydrolyzable fraction of the DOP probably contributes to production in the extensive Pacific oligotrophic gyres.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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".