Benthic Macroinvertebrate and Pollution Tolerance

Questions from reading1. Describe the environment in which you would

find organisms from Group 1.2. Describe the environment in which you would

find organisms from Group 4.2. What organism is considered to be the canary of

clean water and why?3. What factors in a relatively polluted environment

may actually support pollution-tolerant organisms?

4. In what portion of the stream do most benthic macroinvertebrates live?

What is benthic?

• Means bottom dweller

Benthic Macroinverts and Water Quality

• Used as indicators of water quality• Separated into four groups• We count the number of species per group• Most pollution tolerant group is weighted

heavily (multiply by a larger number)• Least tolerant weighted most lightly

(multiply by a smaller number)• The greater the number the more polluted

the river

• Pollution tolerant organisms like clean water as well as intolerant organisms, but tolerant organisms can also survive in polluted places while those others can’t.

• Example: You will find leeches and other worms (group 4) in clean water as well as polluted but stoneflies (group 1) are only found in clean water.

Group I: Pollution Intolerant

• Need high levels of D.O.• Cannot survive in habitats affected by

nutrient pollution• Mostly shredders or predators• Live in clean, cold stream. Found in riffles,

why?• Canary of clean water: stonefly• Dobsonfly, alderfly and snipefly

Group II: Moderately Intolerant

• More tolerant of nutrient enrichment and drops in D.O.

• As algae increase, scrapers increase (water pennies and mayflies)

• Greatest number of organisms, most diverse.

Group III: Fairly Tolerant

• Organisms can accept low levels of D.O.• Mostly scavengers and collectors• Includes sow bugs, scuds, and right

handed snail (gilled).

Group IV: Pollution Tolerant• Very tolerant of low D.O. and severe

nutrient pollution.• Most have special adaptations for

breathing oxygen at surface• left handed snail: breathes air from a

pouch• Bloodworms (midge larva) have

hemoglobin type blood to help them move oxygen through their body