Freshwater Quality
Benthic Index of Biotic Integrity
The Benthic Index of Biotic Integrity (B-IBI) describes the biological condition of stream sites and their surrounding habitat based on the diversity and relative abundance of the benthic (bottom dwelling) macroinvertebrates found at the site. Ten measures of biological condition are scored and summarized as the B-IBI, which ranges from a score of 0, indicating a very poor stream condition, to 100, indicating excellent condition.
Benthic Index of Biotic Integrity
By: Change in Biological Condition
Change in the biological condition of Puget Sound streams, based on the Benthic Index of Biotic Integrity (B-IBI), that were classified as "excellent" and "fair" in 2006-2009 and resampled in 2015-2018. Source: Puget Sound Stream Benthos.

Key Messages

  • Progress toward the 2020 freshwater quality targets was mixed. Overall, biological condition at some sites is declining, improving at others, and not changing at most.
  • Since 2006, the B-IBI scores of some streams have dropped from “excellent” to “good” or “fair”, indicating not all of the “excellent” sites have remained in excellent condition. In contrast, there has been net improvement in the biological condition of streams previously ranked fair by the B-IBI.

Contributing Partners

Recovery Target

1. Protect: 100 percent of Puget Sound lowland stream drainage areas ranked as excellent retain excellent scores for the Benthic Index of Biotic Integrity for biological condition.

2. Restore: Improve and restore at least 30 streams ranked fair so their scores become good. 

Indicator Lead
Last Updated
4/23/2019