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CADDIS Volume 3: Examples & Applications

Worksheets: Little Scioto River, OH

Stressor-Response Relationships from the Field

Sediment | Riffle/pool | Dissolved oxygen | Ammonia | Metals


Sediment

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).

Comparisons of site conditions
Figure 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 13. Stressor-response from the field scores for sediment.
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

View results in: Summary of Scores from the Case:


Riffle/pool

Data

Data downstream from the Site A were used to characterize the stressor-response relationship. Riffle quality is characterized with a qualitative riffle score.

Analysis

Mean riffle 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 channel score and the biological response at Site A was overlaid on the plot (shown in red).

Comparisons of site conditions
Figure 9. Comparisons of site conditions to stressor-response curves.

Discussion

None of the observed biological responses exhibited definitive trends across the observed range of channel scores. 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 14. Stressor-response from the field scores for candidate causes.
Candidate Cause Specific Effect Result Score
Riffle/pool Relative weight No apparent gradient 0
Proportion DELT No apparent gradient 0
Proportion mayflies No apparent gradient 0

View results in: Summary of Scores from the Case.


Dissolved oxygen

Data

Data downstream from the Site A were used to characterize the stressor-response relationship. Dissolved oxygen was measured continuously at each location over a 3-d period with Datasonde continuous monitors.

Analysis

Observed minimum DO 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 minimum DO and the biological response at Site A was overlaid on the plot (shown in red).

Comparisons of site conditions
Figure 10. Comparisons of site conditions to stressor-response curves.

Discussion

The observed proportion of mayflies and DELT seem reasonably consistent with the trends exhibited across the observed range of minimum DO values. However, uncertainty in the position of the fitted curve is large, given that only six data points were available. The observed value of relative weight is much larger than observed at other sites, and falls in the middle of the observed range of DO values.

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 15. Stressor-response from the field scores for dissolved oxygen.
Candidate Cause Specific Effect Result Score
Dissolved oxygen Relative weight No apparent gradient 0
Proportion DELT Consistent with gradient +
Proportion mayflies Consistent with gradient +

View results in: Summary of Scores from the Case.


Ammonia

Data

Data downstream from the Site A were used to characterize the stressor-response relationship.

Analysis

Ammonia concentrations 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 ammonia concentration and the biological response at Site A was overlaid on the plot (shown in red).

Comparisons of site conditions
Figure 11. Comparisons of site conditions to stressor-response curves.

Discussion

All of the biological responses exhibited definitive trends across the observed range of ammonia concentration. However, ammonia concentration was lower at the site than at other locations without the biological impairment (i.e., spatial co-occurrence was scored negatively).

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 16. Stressor-response from the field scores for ammonia.
Candidate Cause Specific Effect Result Score
Ammonia Relative weight Field stressor-response not applicable because of negative spatial co-occurrence score NA
Proportion DELT Field stressor-response not applicable because of negative spatial co-occurrence score NA
Proportion mayflies Field stressor-response not applicable because of negative spatial co-occurrence score NA

View results in: Summary of Scores from the Case.


Metals

Data

Data downstream from the Site A were used to characterize the stressor-response relationship. Metals concentrations were characterized with Zn concentration.

Analysis

Mean Zn concentrations 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 Zn concentrations and the biological response at Site A was overlaid on the plot (shown in red).

Comparisons of site conditions
Figure 12. Comparisons of site conditions to stressor-response curves.

Discussion

The proportion of mayflies exhibited a strong response to Zn. The change in percent DELT and relative weight also seemed correlated with Zn concentration, but observations at the site did not seem consistent with the overall gradient.

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 17. Stressor-response from the field scores for metals.
Candidate Cause Specific Effect Result Score
Metals Relative weight No apparent gradient 0
Proportion DELT No apparent gradient 0
Proportion mayflies No apparent gradient +

View results in: Summary of Scores from the Case.

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