The Antarctic Brachiopod <i>Liothyrella uva</i> As A Proxy For Ambient Oceanographic Conditions At McMurdo Sound
Bibliographic record
Abstract
Abstract Brachiopods have been widely used as proxies to reconstruct ancient oceanographic conditions based on the assumption that their shell calcite is precipitated in near isotopic equilibrium with ambient seawater. Few studies, however, have tested the presumption of equilibrium precipitation for specimens from extreme polar environments. Furthermore, reported isotopic values for polar specimens are largely indicative of disequilibrium precipitation, leading to the conclusion that brachiopods living in extreme environments may be poor recorders of ambient oceanography. The results of shell chemistry of the Antarctic brachiopod Liothyrella uva (L. uva) are compared to the local oceanographic data at Cape Armitage, McMurdo Sound, to assess the suitability of extreme environment brachiopods as environmental proxies. Results reveal that significant kinetic fractionation occurs during primary-layer shell secretion, resulting in whole-shell isotopic compositions that do not reflect equilibrium with ambient seawater. Secondary-layer shell calcite, however, is less affected by biological fractionation and exhibits isotopic compositions that fall within the range of predicted equilibrium values. Additionally, whole-shell concentrations of elements including Ba, Cd, Cr, Fe, Mn, Na, Sr, and Zn exhibit trends that are interpreted to reflect their relative concentrations in ambient seawater. Concentrations of Mg and B, however, are found to be largely controlled by physiological processes related to brachiopod growth rate. While this study concludes that the shell chemistry of L. uva does reflect the local oceanographic conditions at McMurdo Sound, the reliability of extreme-environment brachiopods should be assessed on a species basis as differences in brachiopod physiology and microstructure can significantly influence the degree of equilibrium reflected in shell calcite.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.001 | 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".