slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Problem: Which aquatic stressors are important in a region’s streams? PowerPoint Presentation
Download Presentation
Problem: Which aquatic stressors are important in a region’s streams?

Loading in 2 Seconds...

play fullscreen
1 / 12

Problem: Which aquatic stressors are important in a region’s streams? - PowerPoint PPT Presentation


  • 110 Views
  • Uploaded on

Evaluating the Extent and Relative Risk of Aquatic Stressors in Wadeable Streams throughout the U.S.A. John Van Sickle, John L. Stoddard, Steven G. Paulsen U.S. Environmental Protection Agency National Health and Environmental Effects Research Laboratory Western Ecology Division Corvallis, OR.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Problem: Which aquatic stressors are important in a region’s streams?' - JasminFlorian


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Evaluating the Extent and Relative Risk of Aquatic Stressors in Wadeable Streams throughout the U.S.A.John Van Sickle, John L. Stoddard, Steven G. PaulsenU.S. Environmental Protection AgencyNational Health and Environmental Effects Research Laboratory Western Ecology Division Corvallis, OR

slide2

Problem:Which aquatic stressors are important in a region’s streams?

(“Stressors”-- Nutrients,excessfinesediment, degraded instream habitat, lack of ripariancover, toxicity, flow alteration, acidification, etc.)

Partial Answer:-- Compare the regional extents of stressors.

-- U.S. EPA’s Environmental Monitoring and Assessment

Program (EMAP) designs sample surveys to estimate

stressor extent.

-- Stressor extent can be measured by the percent of

total regional stream length in “Poor” condition

for that stressor.

slide3

Example: Wadeable Stream Assessment (WSA)

sampling locations, 2000-2004

slide4
Stressor extent forWSA Western region:Percent of total stream length in “Poor” conditionfor each of 8 stressors
slide5

Defining “Poor” (Most disturbed) and “Good” (Least disturbed) condition classes from stressor or response index scores at reference sites

Reference-sitedistribution

slide6

However, stressor importance does not depend only on “extent”.

-- We worry less about a widespread stressor,

if its occurrence has little effect on biota.

-- Need to also assess the size of a stressor’s effect on biota.

To assess stressor effects across a region:

-- Will use Index of Biotic Integrity (IBI) for stream macroinvertebrates

as an example measure of stream biota condition (Good or Poor).

-- If a stressor has a strong effect on stream macroinvertebrates,

then “Poor” IBI conditions will tend to occur wherever stressor

condition is also “Poor”.

-- Use relativerisk to measure co-occurrence of Poor IBI

and Poor stressor conditions.

slide7
Example: Relative risk of Poor macroinvertebrate IBI when the excess-sediment (ExSed) stressor is also Poor.

Percent of stream length

(Risk of Poor IBI, given Poor ExSed) =

19/23=0.83

Also --

(Risk of Poor IBI, given Good ExSed) =

18/77=0.23

Result: The risk of Poor IBI when ExSed is Poor is higher than the risk when ExSed is Good.

( Note – “Risk” is just another word for “Probability” )

slide8

Relative Risk (RR) is the ratio of these 2 risks

So: “The risk of Poor IBI is 3.6 times greater in streams

with Poor ExSed than in streams with Good ExSed.”

Notes –

-- If stressor has no effect then RR = 1.

-- Use a confidence interval to express uncertainty in RR.

(EMAPsoftware for the R language calculates RR and

its confidence interval. Free, at www.epa.gov/nheerl/arm/ .

Also, see Van Sickle et al., Environmental Management, in press).

slide9
WSA Western region: Extent of Poor condition for 8 stressors, and relative risk of stressors for Poor macroinvertebrate IBI

Extent

Relative Risk

% of Stream Length

Relative Risk ratio

summary
Summary

Challenges in using relative risk –

--- May not capture joint effects of correlated stressors.

--- Employs condition classes (‘Poor’ vs. ‘Good’).

Advantages of using relative risk –

-- Familiar language for general public.

-- Employs condition classes (‘Poor’ vs. ‘Good’).

-- Combines with stressor extent to assess the

relative importances of different stressors.