Diel patterns of suspended sediment flux and the zoogeomorphic agency of invasive crayfish
Bibliographic record
Abstract
The role of biotic forcing in fluvial geomorphology is understudied.This paper investigates the suggestion that the activities of signal crayfish(Pacifastacus leniusculus) can increase suspended sediment fluxes in rivers.Previous field work, supported by mesocosm experiments, suggests that crayfish nocturnalism can cause night time increases in turbidity, but field data are limited to a 16-hour period from a single site where suspended sediment time-series are not available. Here, field data collected over a 28-day period on the Brampton Branch of the River Nene, UK, are used to quantify the impact of diel fluctuations in suspended sediment concentration on sediment fluxes. Field observations and laboratory experiments are used to evaluate the likelihood that crayfish, whichare abundant in this river, are responsible for the diel patterns. Turbidity and water stage were measured at 2-minute intervals at a single site. Water was sampled for suspended sediment concentration on a diel cycle and during storm events. A relation between suspended sediment concentration and turbidity, along with a local discharge time-series, permitted calculation of sediment flux and sediment loads. Aquarium experiments with one or two crayfish were used to directly observe the relative impacts of crayfish activity and conspecific interactions on sediment suspension. Over the 28-day period, turbidity and suspended sediment exhibited a strong diel pattern, characterised by night-time increases in the frequency and magnitude of spikes in the turbidity data and by increases in ambient suspended sediment concentrations. Small diel fluctuations in stage were also measured, but the rises in stage were out of phase with turbidity and there was no correlation between stage and turbidity at any frequency. In the absence of a credible hydraulic explanation for the increases in night-time suspended sediment concentration, several lines of evidence, including results from the aquarium experiments, strongly suggest that crayfish are the mostlikely cause. We estimate that crayfish activity contributed at least 20% of the suspended sediment load over the 28-day period (which included two moderate floods) and this proportion was 47% during the days when baseflow conditions prevailed. This work extends and strengthens the argument that crayfish are important zoogeomorphic agents with potential implications for managing fine sediment pressures. It also highlights the need to better understand the link between crayfish activity, sediment suspension and downstream dispersal, particularly the catchment-scale distribution and seasonality of such impacts.
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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 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".