Let's talk about those mysterious macros... 
Macroinvertebrates are organisms that do not have internal skeletons. This means they do not have a backbone. They can be seen with the unaided eye.
Would you want to eat fish from a dirty river? Would
you like to go on a picnic beside a smelly creek? Aquatic macroinvertebrates can tell you a lot about the health of your waterway. Aquatic macroinvertebrates include mayfly nymphs, stonefly nymphs, dragonfly larvae, midge larvae, crayfish, leeches, aquatic worms, and water beetles. All life stages of arthropods, mollusks, and worms are included. These little creatures can be harmed when toxic substances dissolve, lie on top or in the water, or are deposited in the stream bed. This means the water quality becomes poorer. When the water quality is not good, aquatic life is affected.
Aquatic macroinvertebrates live in the bottom parts of waters. They are also called benthic macroinvertebrates.
The benthic macroinvertebrates are aquatic insects or they can be in the aquatic stage of an insect’s life. |
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Benthic macroinvertebrate monitoring is a simple tool to monitor water quality. Aquatic macroinvertebrates are a very important part of a river’s ecosystem.
An ecosystem is a group of living organisms (plants, animals, and microrganisms) that work together with each other and with the nonliving environment (air, water, rocks, and energy).
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Drawing by Sarah
When the water becomes unhealthy, or polluted, these aquatic creatures are sensitive to the changes. Some can tolerate pollution better than others. The amount of pollution or changes in the water can be measured by the different types of organisms that live there. Sensitive creatures will not survive in a polluted stream, but the ones that are more tolerant to pollution will survive.
Why Should the Water Be Monitored?
Monitoring the water can help us understand it and make plans to manage it better.
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Most aquatic macroinvertebrates live in the same place during every season of the year and some of them live in the same waterway for years. When the number and type of macroinvertebrates are monitored a lot of information can be found about a waterway’s health. The organisms live in, crawl, or attach themselves to the bottom of a river or stream. Some aquatic organisms do not always stay on the bottom. Some swim through the water or live on the surface.
Macroinvertebrates are good indicators of water quality.
An indicator is a value assigned from measurement. When macroinvertebrates are monitored the number and type found in the water are the indicator and are charted on a data sheet. The numbers are assigned a special value and used to determine water quality. An indicator can be an early sign of pollution or show that an ecosystem may be in trouble. |
Why use this method to monitor water quality?
There are many ways to monitor water quality, but benthic macroinvertebrate monitoring is easy for kids because no training is needed.
1. It is easy to collect data without expensive equipment.
2. It is a good way to see what the water quality is and has been over a long period of time.
If there is not much pollution, the water usually has lots of oxygen for the benthic macroinvertebrates. High oxygen amounts are one indicator of good water quality. Since the organisms do not move when a stream becomes polluted the species could die out if the water does not have enough oxygen. This is why the kind and number of macroinvertebrates found in the water show what the water quality is now and has been in the past.
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3. There is aquatic biodiversity in a healthy stream. This means that a healthy stream will have a variety of ALL of the pollution-sensitive macroinvertebrates. An unhealthy stream will have only a few types of non-sensitive macroinvertebrates.
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