Effects of fish on plankton dynamics: a theoretical analysis
Bibliographic record
Abstract
We present an expansion of a classical minimal Daphnia-algae model to account for effects of fish as a top predator. Our analyses suggest that in most situations, the plankton should show hysteresis in response to predation pressure by fish. Thus, there exist two distinct regimes, one in which Daphnia is controlled (overexploited) by fish and phytoplankton biomass is high and another in which Daphnia is relatively unaffected (underexploited) by planktivores and algae are controlled by Daphnia. Switches from one regime to the other occur abruptly at a critical fish density. This is in line with field observations and experimental results. Our model predicts that the critical fish density for Daphnia collapse is higher in systems with higher ambient nutrient concentrations. The model also shows how intrinsic predator-prey oscillations in the planktonic system can facilitate the switch to the algal-dominated regime where Daphnia is controlled by fish. In terms of dynamical systems theory, this switch happens through a homoclinic bifurcation. In biological terms, Daphnia collapses due to food limitation and is subsequently overexploited by fish. This is indeed the sequence of mechanisms observed at the end of the spring clearwater phase in lakes where Daphnia is absent during the summer when the biomass of young-of-the-year planktivorous fish becomes high.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".