Sources and transport of terrestrial organic matter in Vancouver Island fjords and the Vancouver‐Washington Margin: A multiproxy approach using d13Corg, lignin phenols, and the ether lipid BIT index
Bibliographic record
Abstract
The Branched and Isoprenoid Tetraether (BIT) index (a ratio of marine and terrestrial glycerol dialkyl glycerol tetraether [GDGT] membrane lipids) was recently introduced as a proxy for the fraction of fluvially derived organic carbon (OC) buried in marine sediments. We investigate the source and distribution of terrestrial OC in marine sediments in a large spatial data set that encompasses the Washington‐Vancouver Island Margin, Vancouver Island fjords, and Puget Sound with the goal of comparing the BIT index to other traditional measures of terrestrial OC (δ 13 C of OC [δ 13 C org ] and lignin phenols). δ 13 C org values and lignin concentrations indicate that the fjords are a significant trap for undegraded, wood‐derived terrestrial material, with surface sediments containing up to 76% terrestrial OC. These proxies also show significant terrestrial OC contributions to margin sediments (up to 54%), with most likely an angiosperm source from the Columbia River. In contrast to δ 13 C org values and lignin concentrations, BIT index values indicate extremely low terrestrial carbon throughout the study area (BIT index values range from 0 to 0.28) and are uncorrelated with the other proxies. Though the BIT index did not correlate with other proxies, margin GDGT concentrations varied offshore similarly to other terrestrially derived OC and are well‐correlated with other proxies. We suggest that the BIT index is best interpreted as a proxy for soil‐ or peat‐derived OC. The majority of terrestrially derived OC delivered to sediment in this area has a lignin‐rich, nonsoil source. The disparity between the BIT index and other proxies implies that the BIT index significantly underestimates terrestrial relative to marine OC input to sediments in areas in which riverine OC input is not soil or peat derived.
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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 | 0.001 | 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 | 0.001 |
| 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".