Iowa DNR
BioNet
River & Stream Biological Monitoring
Fish and Benthic Macroinvertebrate Surveys
Physical Habitat Assessments

Big Muddy Creek Spencer

Analysis Summary for Series #1542

Benthic Macroinvertebrate Index of Biotic Integrity (BMIBI)

Metric Name Value Score
MH Total Taxa 20 3.92
SH Total Taxa 8.33 4.1
MH EPT Taxa 7 2.93
SH EPT Taxa 5.33 3.84
MH Sensitive Taxa 2 1.85
SH Ephem % 15.2 1.94
SH EPT % 27.56 2.89
SH Chiron % 68.59 3.17
SH Scraper % 6.77 1.51
SH Top3Dom % 88.06 1.94
SH Dom FFG % 80.23 3.29
MHBI 5.62 5.11
*Mouse-over metric for full name
**Final IBI is sum of scores multiplied by 0.8333

Analysis Factors

Factor Value
BMIBI Type Warm Water
Sample Date 8/27/2013
Sampling Series Series #1542
Drainage Area (mi2) 63.018
Log(DA) 1.79946461586834
Calculation Last Updated 7/22/2025 3:36:28 PM
Sampling Gear ArtSub
BMIBI Score
30
Warm Water
Poor
Series Analysis Notes

Artficial substrates were poor in quality due to little to no flow. A beaver dam was present downstream of the reach, and compounded the issue.

BMIBI Score Explained

This site was analyzed using the BMIBI-Warm Water assessment methodology.

Sites that score between 0 - 30 are considered poor. Severely impaired macroinvertebrate community. Low numbers of taxa present, sensitive species not present, EPT taxa are rare or not present; community extremely unbalanced; dominated by a few pollution tolerant organisms; some trophic functional feeding groups are not represented. Total numbers of organisms may be low. Total taxa richness and EPT taxa richness are noticeably reduced from optimum levels; sensitive species and habitat specialists are rare; EPT taxa no longer dominate the macroinvertebrate community. Taxa that are tolerant of organic enrichment and/or excessive sediment loads are dominant; the community is unbalanced; a few generalist taxa make up a high percentage of the organisms present; collector-gatherers or collector-filterers are very dominant.

This location has been classified as a Reference Site. Reference sites represent natural stream qualities that are least disturbed by human activities within the watershed. These sites are then grouped by ecoregion to establish a benchmark against which other streams in the same ecoregion are compared.

EcoRegion Comparison

Scores for a sampling session are compared against reference sites within the same ecoregion:

Des Moines Lobe

This site is in the Des Moines Lobe ecoregion.

Ecoregion Map
Max 84
75th Percentile 67
Median 59
25th Percentile 50
Min 10
This Session's Score 30
Total Reference Site Samples 173
Mean 57.64
Standard Deviation 13.14