|
Data:
Data downstream from the Site A were used to characterize the stressor-response relationship. Sediment levels are characterized with a qualitative substrate score.
Analysis:
Mean substrate scores were plotted against the three specific variables. Where appropriate a curve was fit to the observations as a visualization aid. The point corresponding to observed substrate score and the biological response at Site A was overlaid on the plot (shown in red).
Figure W1-8. Comparisons of site conditions to stressor-response curves.
Discussion:
None of the observed biological responses exhibited definitive trends across the observed range of substrate. However, uncertainty in the assessment of these trends is large, given that only six data points were available.
Evidence Scoring Table:
| Finding |
Interpretation |
Score |
| A strong effect gradient is observed relative to exposure to the candidate cause, at spatially linked sites, and the gradient is in the expected direction. |
This finding strongly supports the case for the candidate cause, but is not convincing due to potential confounding. |
++ |
| A weak effect gradient is observed relative to expsoure to the candidate cause, at spatially linked sites, OR a strong effect gradient is observed relative to exposure to the candidate cause, at non-spatially linked sites, and the gradient is in the expected direction. |
This finding somewhat supports the case for the candidate cause, but is not strongly supportive due to potential confounding or random error. |
+ |
| An uncertain effect gradient is observed relative to exposure to the candidate cause. |
This finding neither supports nor weakens the case for the candidate cause, because the evidence is ambiguous. |
0 |
| An inconsistent effect gradient is observed relative to exposure to the candidate cause, at spatially linked sites, OR a strong effect gradient is observed relative to exposure to the candidate cause, at non-spatially linked sites, but the gradient is not in the expected direction. |
This finding somewhat weakens the case for the candidate cause, but is not strongly weakening due to potential confounding or random error. |
- |
| A strong effect gradient is observed relative to exposure to the candidate cause, at spatially linked sites, but the relationship is not in the expected direction. |
This finding strongly weakens the case for the candidate cause, but is not convincing due to potential confounding. |
-- |
Table W1-13. Stressor-response from the field scores for candidate causes.
| Candidate Cause |
Specific Effect |
Result |
Score |
| Sediment |
Relative weight |
No apparent gradient |
0 |
| Proportion DELT |
No apparent gradient |
0 |
| Proportion mayflies |
No apparent gradient |
0 |
|