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Macroinvertebrate Bioassessment Tools. Aquatic Life/Nutrient Workgroup August 11, 2008. Discussion Topics. Reference and stressed site status O/E (RIVPACS) preliminary results MMI (multimetric index) preliminary results Bioclasses. Reference Site Review. Two part process:

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Macroinvertebrate bioassessment tools

Macroinvertebrate Bioassessment Tools

Aquatic Life/Nutrient Workgroup

August 11, 2008

Discussion topics
Discussion Topics

  • Reference and stressed site status

  • O/E (RIVPACS) preliminary results

  • MMI (multimetric index) preliminary results

  • Bioclasses

Reference site review
Reference Site Review

  • Two part process:

    • Calculated GIS-based human disturbance values and established criteria cutoffs

    • Reviewed and critiqued aerial images at EPA using Global Explorer

  • 11 additional ref sites added to fill obvious spatial gaps and large rivers in plains and xeric bioregions

Reference sites
Reference Sites

  • 168 reference sites finalized in April (90 mnts, 39 plains, 39 xeric)

  • 4 xeric, 4 plains and 1 mnts sites removed later

  • All USFS sites (n=16) retained – midges ID’ed down to genus

  • 12 additional sites w/ low taxa counts could be removed (USU and TT testing)

Stressed site review
Stressed Site Review

  • Flagged human disturbance values (GIS derived) that exceeded “acceptable” conditions and further reviewed with Google Earth images

  • Sites exhibiting clear characteristics of stressed condition retained after image review

Stressed sites
Stressed Sites

  • Goal: identify unquestionably stressed sites – no marginal ones

  • 74 stressed sites finalized in June

  • 31 mnts, 23 plains & 20 xeric

O e model progress
O/E Model Progress

  • Predictor variables calculated

  • OTU’s assignments redefined

    • Improved resolution

  • Replicate #’s organized & sample IDs selected

  • Reference sites reviewed by Utah St staff

    • 6 sites suggested for removal based on additional aerial image review – WQCD agreed

O e preliminary modeling
O/E Preliminary Modeling

  • USU modeling based on 143 ref sites and 282 taxa (OTU's)

  • Rare taxa not used (106 taxa remained)

  • Cluster analysis/ordination

    • Used presence/absence of taxa among sites

  • Investigating 2 alternate groupings:

    • 3 classes – Ecoregions

    • 13 classes – Bioclasses

O e preliminary modeling1
O/E Preliminary Modeling

  • Spatial distribution of samples coded by 3 bug-defined classes

Performance plot
Performance Plot

  • Sites coded by bioregion

  • Good agreement between what the model predicts at a site and what is observed

O e preliminary modeling2
O/E Preliminary Modeling

  • Spatial dist. of samples coded by 13 bug-defined classes

Performance plot1
Performance Plot

  • Sites are coded by the group assignments

  • Different types of streams vary in predicted and observed richness

  • r2 = 0.85

Mmi preliminary modeling
MMI Preliminary Modeling

  • Tetra Tech keeping in sync with Utah State work

    • Same OTU designations, predictor variables, reference sites and samples used

  • Retained rare taxa – Tetra Tech investigating further

Preliminary findings
Preliminary Findings

  • Tetra Tech’s ordination similar to Utah State’s

    • Geographic ecoregions not a perfect fit

  • Biology is sensitive to the natural gradients in temp. and water amount across the landscape

  • Bioclasses may work better than ecoregions


  • Not defined by geographic regions

  • Defined more by broad habitat characteristics

  • Doesn’t lend itself to drawing lines on a map

Bioclass example
Bioclass Example

  • Primary predictors appear to be summer water temperature and amount of water

  • Amt of water = ƒ (watershed area, precipitation)

  • Stream temp = ƒ (amount of water, elevation, latitude)


  • Two sites, close together geographically, can be in two very different bioclasses

    • Mainstem (large watershed) vs. tributary (small)

  • We do some of that already with mainstems separated from “all tribs,” but not consistently


  • How we might identify bioclass membership

Upcoming work
Upcoming Work

  • Tetra Tech will try further classifications by removing rare taxa

  • Critically reviewing how to standardize analysis & treatment of data

  • Move deeper into the modeling processes

    • O/E – predictive modeling

    • O/E – estimating probability of capture (pc) & E

    • MMI – metric calculations


Drunella doddsi


Baetis tricaudatus



  • Utah State website on Predictive Models:


  • Bioassessment tool info and PowerPoint presentations: