Stream Macroinvertebrates

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Stream Macroinvertebrates by Debby Edmonds
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Can you figure out what a stream or aquatic
macroinvertebrate is?

• What does a vertebrate have?
• What would an invertebrate not have?
• Microscopic organisms can only be seen through
  a microscope so what would be true of macro
  organisms?
• Where do these macro invertebrates live?

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A hundred years ago miners used to take canaries
into the mines. The little canaries were more
sensitive to air quality than the humans. If a
canary lost consciousness, that could indicate
that there might be changes for the worse in air
quality.
Likewise, today the presence of living
macroinvertebrates can indicate good, fair, or
poor water quality depending on the sensitivity
of a particular critter.
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Chemical and physical changes can affect any
living thing. Changes in pH, sediment from
erosion, fertilizer run-off often affect the
critters that live in streams because they
cant pack up and move away.
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Only the stream macro invertebrates which need
dissolved oxygen are good indicators.

• Some snails can crawl out on land, for instance,
  so they can survive in poor water quality. The
  lunged snail with opening on the left is not
  sensitive about living in polluted water.
• Gilled snails, on the other hand, must have good
  water quality in order to live since they depend
  on dissolved oxygen. They have a shell opening on
  the right.

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Adult mayfly
Some macroinvertebrates spend their whole lives
under water, but many only live there as baby
insects in the nymph or larval stage. They
emerge to become flyers like dragonflies and
mayflies.
Baby mayfly or nymph
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These emerging adult insects are an important
food source for birds and fish and are a vital
part of the ecosystem.
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Before emerging, these macroinvertebrates are,
also, important to the ecosystem. While some like
hellgramites (later called dobsonflies) are
predators, many eat algae and decaying leaves,
and then larger organisms eat them.
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If you are looking at an aquatic
macroinvertebrate, how can you tell what you
have? A key contains the answer. First a series
of questions are asked each of which have two
possible answers. You proceed according to which
answer you choose. Eventually you will see a
picture of your critter.
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• These are places you can visit to see
• the macroinvertebrates and find out more
• about them.
• Save Our Streams
• (Select Identification Key.)