Compositional and interlake variability of zooplankton affect baseline stable isotope signatures
Bibliographic record
Abstract
Zooplankton are commonly used to establish a baseline isotopic signature for pelagic production in lakes. Our objective was to evaluate this approach by quantifying among‐lake and within‐lake variability of δ 13 C and d15N for different taxa of pelagic zooplankton. We measured the δ 13 C and δ 15 N of Daphnia , Holopedium , and calanoid copepods from four lakes sampled from June to November 2001 and from eight additional lakes sampled once in midsummer. In the four lakes with temporal sampling, within‐lake differences due to taxonomic grouping accounted for 36.7% of the variance in δ 15 N and 41.7% of the variance in δ 13 C. Among all lakes, the δ 15 N of calanoid copepods was on average 2.55‰ and 2.44‰ higher than Daphnia or Holopedium , respectively, whereas the δ 13 C of calanoid copepods was 2.19‰ and 2.23‰ lower than Daphnia or Holopedium , respectively. If 15N fractionation is similar among species, the differences in δ 15 N suggest that calanoid copepods either feed at a higher trophic position in the food web or they have a consistently higher baseline δ 15 N signature than Daphnia or Holopedium among lakes. Differences in δ 13 C suggest that zooplankton taxa in the pelagia of lakes have different food sources. We conclude that species composition and feeding behaviors of the zooplankton community should be considered before making among‐lake comparisons of food web structure. We show that Daphnia is a useful isotopic baseline for organisms that rely on primary production in lakes.
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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) | 0.001 | 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 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".