Learn Benthics

Participants of the EcoSpark’s Changing Currents program sample and collect up to 27 different groups of freshwater benthic macroinvertebrates (BMIs): bottom-dwelling aquatic organisms that lack a backbone, can be seen with the naked eye, and dwells at the bottom of streams and rivers.

Scroll through the page below to learn how these BMIs act as vital indicators of water quality and watershed health, based on their tolerance to pollution. Ranked by their tolerance level to sources of pollution in their habitat and varying water conditions, they fall into three categories: least tolerant, moderately tolerant and most tolerant.

Click on each images below to learn more about each BMI’s life cycle, feeding habits and other unique facts.


Confident about your id skills? Test your knowledge with our BMI ID activity!


LEAST TOLERANT of Pollution
Values between 1-4 on the Hilsenhoff Biotic Index

 
 

MODERATLY TOLERANT of Pollution
Values between 5-6 on the Hilsenhoff Biotic Index

 
 

MOST TOLERANT of Pollution
Values between 7-8 on the Hilsenhoff Biotic Index