Geochemical records in Canadian bamboo corals, potentials and pitfalls
Bibliographic record
Abstract
Deep-sea gorgonian octocorals of the families Primnoidae and Isididae exhibit centennial-scale lifespans and in some species annually-secreted growth rings, which potentially provide high-resolution long term paleoceanographic records. We examined trace element and stable carbon (d13C) and oxygen (d18O) isotope variability in a live-collected 140 year old specimen of Keratoisis ornata (Isididae) from the southern Grand Banks of Newfoundland (700 m water depth) and in a late Holocene K. ornata form the Hudson Strait dated at ~1.1 ka BP (~200 yr life-span). Skeletal chronology was previously established through a combination of AMS-14C, 210Pb and bomb-14C dating and revealed a growth rate of 76 µm/yr. Hydrographic records from the Southern Grand Bank extend back to the early 20th century, overlapping with the coral record almost continuously over a period of 96 years. Focusing on the skeletal calcite fraction, trace elements were measured along parallel radii of axial sections using laser ablation ICP-MS, while d13C and d18O were measured on micromilled samples acquired at a spatial resolution of 100 µm. Trace elements and stable isotopes turned out to be strongly linked to microstructure, with strong differences between the juvenile and the adult skeletal portions. Isotopic values were relatively depleted in juvenile calcite bands, while trace elements were strongly enriched in Li, Mg and B. Only the heaviest d18O-values from the adult phase are in equilibrium with seawater d18O-composition and temperature, inhibiting the extraction of temperature time-series from ontogenetic transects. Bulk adult Mg/Ca-values at 4°C fit the temperature calibration for P. resedaeformis by Sherwood et al. (2005), as well as with the calibration for Lepidisis sp. by Thresher et al. (2010). Long-term temperature series are at present difficult to extract, because Mg/Ca show a similar systematic ontogenetic decrease in the Recent and the late Holocene K. ornata specimens. This leads to a reconstruction of an apparent 1°C drop across the last 96 years, which is opposite to the measured 1°C rise. Overall, our results demonstrate that further development is required to interpret geochemical patterns in gorgonian calcites as reliable environmental proxies.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".