Delta15N Trophic Level Scale

Evaluate caller nitrogen-enrichment trophic proxy with independent measurement/baseline uncertainty; signed relative positions remain and baseline/enrichment differences are not dietary diagnosis.

Description

Nitrogen isotope enrichment can be interpreted through a supplied baseline and per-level increment.

Nitrogen isotope enrichment can be interpreted through a supplied baseline and per-level increment. Standardizing a sample relative to that baseline gives a model trophic position rather than a direct dietary diagnosis.^[1]

Evaluate caller nitrogen-enrichment trophic proxy with independent measurement/baseline uncertainty; signed relative positions remain and baseline/enrichment differences are not dietary diagnosis.

When to use Delta15N Trophic Level Scale

Use this tool to evaluate caller nitrogen-enrichment trophic proxy with independent measurement/baseline uncertainty; signed relative positions remain and baseline/enrichment differences are not dietary diagnosis.

Prepare the artifact, site or survey measurements and any independently established calibration or model choices. Keep paired observations aligned and confirm units and coordinate conventions.

How to use Delta15N Trophic Level Scale and understand its results

Prepare the artifact, site or survey measurements and any independently established calibration or model choices. Keep paired observations aligned and confirm units and coordinate conventions.
Enter sampleDelta15N, baselineDelta15N, baselineTrophicLevel, enrichmentPerTrophicLevel, sampleSigmaPerMil, baselineSigmaPerMil using the field table and calculation rules, then run the tool.
Read modelTrophicLevel, independentLevelSigma. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
sampleDelta15N	Sample delta15 n	number	Required
baselineDelta15N	Baseline delta15 n	number	Required
baselineTrophicLevel	Baseline trophic level	number	Required
enrichmentPerTrophicLevel	Enrichment per trophic level	number	Required
sampleSigmaPerMil	Sample sigma per mil	number	Required
baselineSigmaPerMil	Baseline sigma per mil	number	Required

Enter finite isotope values in per mil, positive baseline level and enrichment per trophic level, and nonnegative sample/baseline sigmas. Calculate the signed relative position and independent combined sigma. The resulting level is not clipped to the baseline or forced positive.

level = baselineLevel + (sampleδ15N−baselineδ15N)/enrichment; sigma = hypot(sampleSigma,baselineSigma)/enrichment

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
modelTrophicLevel	Model trophic level	number
independentLevelSigma	Independent level sigma	number

json

{
  "input": {
    "sampleDelta15N": 10,
    "baselineDelta15N": 4,
    "baselineTrophicLevel": 1,
    "enrichmentPerTrophicLevel": 3,
    "sampleSigmaPerMil": 0.3,
    "baselineSigmaPerMil": 0.4
  },
  "output": {
    "modelTrophicLevel": 3,
    "independentLevelSigma": 0.16666666666666666
  }
}

Limitations and assumptions

Enrichment and baseline are supplied calibration. Correlation, environmental variation and uncertainty in enrichment are omitted. The output does not uniquely identify foods or trophic behavior.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use C:N Ratio Diet Indicator: Convert measured C/N mass percentages to atomic ratio and caller collagen-preservation screen; this ratio is not a diet determination. For a complementary task, use Delta13C C3/C4 Diet Mix: Solve a caller two-endmember linear delta13C diet scenario with explicit tissue offset; assumes equal carbon routing and consistent isotope basis, not identified foods or an actual diet diagnosis.

References

Delta15N Trophic Level Scale — tool.io

Similar or alternative tools

C:N Ratio Diet Indicator
Convert measured C/N mass percentages to atomic ratio and caller collagen-preservation screen; this ratio is not a diet determination.
Delta13C C3/C4 Diet Mix
Solve a caller two-endmember linear delta13C diet scenario with explicit tissue offset; assumes equal carbon routing and consistent isotope basis, not identified foods or an actual diet diagnosis.