Using CSIA-AA of Paleo Cod Bone Collagen to Uncover Changes in Basal Nitrogen Sources and Trophic Position in the Gulf of Maine Over the Past 4,400 Years
Bibliographic record
Abstract
The ecosystem found within Gulf of Maine is both economically valuable, and rapidly changing. It is important to study past hydrographic and ecosystem changes to understanding how the system may behave in the future. This can be done by utilizing stable nitrogen isotopes from paleomarine organism’s tissue. Previous nitrogen isotope studies of bulk proteins extracted from ancient Atlantic cod (Gadus morhua) tissues document a 1-2‰ decrease in δ15N values over the last couple of centuries (Harris et al., unpub; Lueders-Dumont et al., 2018). Due to the nature of the nitrogen isotope signal in bulk proteins, this isotopic shift may be attributed to a decrease in trophic level and/or a change in baseline nitrogen in the Gulf of Maine over this time period. Here, we analyze the δ15N value of individual amino acids (AA) from ancient cod bone collagen to tease out the relative importance of shifts in trophic level vs baseline nitrogen sources to cod diets through time. The δ15N values of phenylalanine (minimally-fractionating “source” amino acid) extracted from cod bone collagen fluctuated between 4.8±0.9‰ to 9.4±1.3‰ over the last 4,400 years with a peak at 500 yr BP. This peak in δ15NPhe suggests a shift in basal nitrogen sources, potentially linked to changes in hydrographic conditions, such as an increased influence of Labrador Slope Water during this period. The calculated trophic position (TP) shows a significant decline at 500 years BP, which may be associated with the pulse of Labrador Slope Water (LSW). This pulse of LSW could have impacted the ecosystem by shortening the food web or by triggering changes in indigenous fishing practices that favored smaller cod.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 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".