selectivity in the estuarine transition zone
Bibliographic record
Abstract
The freshwater–saltwater transition zones of upper estuaries often contain high concentrations of particulate organic matter (POM) that could potentially support their productive food webs. Our objectives were to define the carbon and nitrogen isotopic characteristics of POM across the estuarine transition zone (ETZ) of the St. Lawrence River, Canada, and to determine the availability of this material to primary consumers. The d13C of seston from upstream freshwater samples (226.3 6 0.9‰) indicated a large contribution of terrestrially derived organic material, whereas downstream sites had higher values (224.8 6 0.5‰) attributable to dilution with marine phytoplankton. The ETZ turbidity maximum had more negative values (227.0 6 1.6‰), especially the,5-mm fraction (230.0 6 1.3‰) that contributed 56–86 % of the POM. The d13C of the dominant consumer species in the ETZ (Bosmina longirostris, Keratella sp., Eurytemora affinis, and adult Dreissena polymorpha) averaged 221.0 6 0.9‰, well above the seston values. The d15N of the three animals of lowest trophic position averaged 7.3 6 0.8‰, less than 2 ‰ above the seston d15N (5.7 6 0.2 ‰ for all sites). Our results imply that the bulk POM is largely detrital and unavailable to the ETZ food web and that the primary consumers feed selectively on phytoplankton despite its low contribution (,10%) to total POM. A cross-system comparison of isotopic data shows that the large enrichment of 13C in consumers relative to POM is unusual, underscoring the distinctive character of turbid, upper estuarine
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 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 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".