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Puget Sound Stream Benthos

Benthic Index of Biotic Integrity (B-IBI, BIBI) Variations

This website supports several types of B-IBI scoring systems. These different versions were developed to match the different ways in which projects analyze their sample taxa – what taxa are resolved to species, genus or family, etc. These variations are described below using formulas and bracket notation where applicable.

B-IBI 0-100 (Recommended)

Unlike the other score types, this one is based on formulas. There is one set of formulas for each of the 3 taxonomic resolutions, although, as seen below, only the Taxa Richness, Clinger Richness, and Percent Dominant formulas vary between taxonomic resolutions.

If an equation's result is less than 0, 0 is used; if it is greater than 10, 10 is used. This limits the B-IBI to the 0-100 range. Also shown are the 10th and 90th percentiles used to define the formulas.

For details on how and why this index was created, see the B-IBI Recalibration page.

MeasureTaxonomic Resolutions/EffortsFormula10th Percentile90th Percentile
Taxa RichnessCoarse10 x (<Observed Value> - 16)/(37 - 16)1637
Taxa RichnessMedium10 x (<Observed Value> - 20)/(43 - 20)2043
Taxa RichnessFine10 x (<Observed Value> - 27)/(56 - 27)2756
Ephemeroptera RichnessCoarse, Medium, Fine10 x (<Observed Value> - 1)/(8 - 1)18
Plecoptera RichnessCoarse, Medium, Fine10 x (<Observed Value> - 1)/(8 - 1)18
Trichoptera RichnessCoarse, Medium, Fine10 x (<Observed Value> - 1)/(9 - 1)19
Clinger RichnessCoarse10 x (<Observed Value> - 5)/(22 - 5)522
Clinger RichnessMedium10 x (<Observed Value> - 7)/(23 - 7)723
Clinger RichnessFine10 x (<Observed Value> - 7)/(24 - 7)724
Long-Lived RichnessCoarse, Medium, Fine10 x (<Observed Value> - 2)/(10 - 2)210
Intolerant RichnessCoarse, Medium, Fine10 x (<Observed Value> - 0)/(7 - 0)07
Percent DominantCoarse10 - [10 x (<Observed Percent> - 44)/(82 - 44)]4482
Percent DominantMedium10 - [10 x (<Observed Percent> - 39)/(75 - 39)]3975
Percent DominantFine10 - [10 x (<Observed Percent> - 32)/(69 - 32)]3269
Predator PercentCoarse, Medium, Fine10 x (<Observed Percent> - 1)/(21 - 1)121
Tolerant PercentCoarse, Medium, Fine10 - [10 x (<Observed Percent> - 0)/(43 - 0)]043

10-50 B-IBI: Medium, Coarse Resolution (Species-Genus)

Score1
Very Poor		3
Fair		5
Excellent
Taxa Richness[0, 20)[20, 40](40, ∞)
Ephemeroptera Richness[0, 4](4, 8](8, ∞)
Plecoptera Richness[0, 3](3, 7](7, ∞)
Trichoptera Richness[0, 5)[5, 10)[10, ∞)
Clinger Richness[0, 10](10, 20](20, ∞)
Long-Lived Richness[0, 2](2, 4](4, ∞)
Intolerant Richness[0, 2](2, 3](3, ∞)
Percent Dominant[75, 100][50, 75)[0, 50)
Predator Percent[0, 10)[10, 20)[20, 100]
Tolerant Percent[50, 100](19, 50)[0, 19]
Very Poor
Very Poor		Poor/​Very Poor
Poor/Very Poor		Poor
Poor		Fair/​Poor
Fair/Poor		Fair
Fair		Good/​Fair
Good/Fair		Good
Good		Excellent/​Good
Excellent/Good		Excellent
Excellent
Overall Score[10, 16](16, 18)[18, 26](26, 28)[28, 36](36, 38)[38, 44](44, 46)[46, 50]
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10-50 B-IBI: Fine Resolution (Species-Family)

Score1
Very Poor		3
Fair		5
Excellent
Taxa Richness[0, 15)[15, 28](28, ∞)
Ephemeroptera Richness[0, 4](4, 8](8, ∞)
Plecoptera Richness[0, 3](3, 7](7, ∞)
Trichoptera Richness[0, 5)[5, 10)[10, ∞)
Clinger Richness[0, 8](8, 18](18, ∞)
Long-Lived Richness[0, 2](2, 4](4, ∞)
Intolerant Richness[0, 2](2, 3](3, ∞)
Percent Dominant[80, 100][60, 80)[0, 60)
Predator Percent[0, 10)[10, 20)[20, 100]
Tolerant Percent[50, 100](19, 50)[0, 19]
Very Poor
Very Poor		Poor/​Very Poor
Poor/Very Poor		Poor
Poor		Fair/​Poor
Fair/Poor		Fair
Fair		Good/​Fair
Good/Fair		Good
Good		Excellent/​Good
Excellent/Good		Excellent
Excellent
Overall Score[10, 16](16, 18)[18, 26](26, 28)[28, 36](36, 38)[38, 44](44, 46)[46, 50]
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Ecology MMI

Wash. State Dept. of Ecology Multi-Metric Index
Score1
Poor		3
Fair		5
Good
Taxa Richness[0, 24)[24, 33](33, ∞)
Ephemeroptera Richness[0, 4](4, 6](6, ∞)
Plecoptera Richness[0, 3)[3, 5](5, ∞)
Trichoptera Richness[0, 4)[4, 6](6, ∞)
Clinger Percent[0, 26)[26, 47](47, 100]
Long-Lived Richness[0, 3)[3, 5](5, ∞)
Intolerant Richness[0, 2)[2, 2](2, ∞)
Percent Dominant(70, 100][54, 70][0, 54)
Predator Percent[0, 11)[11, 19](19, 100]
Tolerant Percent(19, 100][11, 19][0, 11)
Poor
Poor		Fair
Fair		Good
Good
Overall Score[10, 20)[20, 30](30, 50]
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