1.2 The importance of macro-invertebrates
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Curriculum Alignment

1, 2, 10, 14, 18, 19, 25, 26

Years K-6: Science and Technology, HSIE, Creative Arts
Years 7-10: Science, Geography 
Years 11-12: Biology, Community and Family Studies, Science, Agriculture, Earth and Environmental Science, Society and Culture

SOSE, Science, Geography 

Futures, Interdependence, Thinking

Science, Thinking Processes, Geography

>Students will identify macroinvertebrates and describe what their presence indicates
>Students will use macroinvertebrates to investigate the health of their catchment
>Students will discuss threats to water quality in their catchment
>Students will create a poster (in class) or discuss (in the field) ways humans can improve water quality in their catchment

1 hour

Materials required
>Buckets of recently captured macroinvertebrates from a range of waterbodies (for in class-room adaptation)
>Nets, boots and buckets (for outdoor option only)
>Litter trays
>Ice cube containers
>Field guides
>Butcher’s paper, pad or whiteboard
>Macroinvertebrate poster 
>Macro-Modelling Deck (see below) 
>Water Bug Worksheet 

Water Mite. Photograph: Rhonda Butcher
Water Mite. Photograph: Rhonda Butcher

Physical and chemical analyses gives scientists a lot of answers about water quality, but it can’t answer them all. Long-term monitoring of plants and animals along a waterway adds a time-based aspect to our understanding that cannot be easily gained by monthly testing. Even using volunteers, physical and chemical analysis of water is time consuming and costly.

However, macroinvertebrates are always in the water, always using the water, and thus constantly affected by its quality.

This is particularly true in rivers. For, as the old saying goes, a river is never the same twice. They are in constant motion. A pollution incident on land poisons the soil and sinks in. A pollution incident in a waterway kills and then moves on to kill somewhere else.

It is possible to take a water sample on a Friday afternoon, find the quality good, go home, return Monday morning and also find a good sample and miss a major pollution incident that took place in between. 

Chemical and physical analyses can only ever tell us about how the waterway is at THAT TIME. They say nothing about how it was, an hour, a day, a week, or a month ago. 
However, animals living in the waterway are the historians of the place. If the water quality is good now, but only very pollution-tolerant animals are found, it is sensible to conclude that something happened at this site. 

Similarly, after a heavy rain, a river might be very turbid (muddy), yet the presence of sensitive macroinvertebrates informs us that the waterway is generally clean.
As macroinvertebrates form the bottom of the aquatic food chain, what affects them changes the whole system. Further, their needs reflect the needs of many larger animals that are not so common nor easily captured, such as the larger native fish species.

Macroinvertebrates have specific needs that tell us about particular physical and chemical parameters, as one gets more familiar with them. Stone flies for instance require high levels of oxygen, while dragon flies and damsel flies indicate good levels of emergent vegetation. These factors have a huge impact on the type and quality of fish and frog species that can be expected in the habitat.

Mudeye. Photos: Rhonda Butcher.
Mudeye. Photos: Rhonda Butcher.

Food web
Water quality

Lesson plan
1. Ask the students to attempt to define macroinvertebrates and express their importance to the ecosystems in which they are found.

2. Have the students outline why they think monitoring macroinvertebrates is important as well as measuring water chemistry parameters.

3. At your nearby river or stream identify different microhabitats within the stream area, such as riffles, pools and vegetation-fringed edges.

4. Discuss ways that macroinvertebrates can be affected by human and non-human events in the catchment.

5. Get the students to consider what needs different animals could be expected to have in differing habitats. 

6. Ask the students to theorise on the sorts of animals that might live in each habitat. How might they be adapted to their environment?

Maybe compare the 
habitat and food
needs of a platypus
or Murray cod with a 
frog, turtle or yabby.

Midges. Photos: Rhonda Butcher.
Midges. Photos: Rhonda Butcher.

7. Write these theories down to revisit after further investigations.

8. Work with the students to set macroinvertebrate handling rules. 

9. Have the students develop their own ideas about appropriate behaviour around a body of water.

10. Demonstrate the use of the equipment to the students. Caution them that not everyone will be getting in the water or using the nets.

11. Instruct the students on how to capture, pick out of nets, sort and identify macroinvertebrates. (Younger students will need more assistance).

12. Break the students into 4-6 groups, each with a net, litter tray and selection of tweezers, spoons and pipettes as well as an ice cube tray.

13. Move between the groups offering help on capture techniques and assisting with identification.

14. Instruct the students to each focus on one macroinvertebrate, then: 

> Draw it
> Identify it, if possible
> Identify its habitat
> Indicate its sensitivity to pollution
> Indicate its adaptations to its habitat.

15. List all the creatures discovered and note their sensitivity to pollution.

16. Get the students to make judgements about water quality based on their discoveries.

17. Ask students to extrapolate from their water quality assessment, issues associated with the water body and how the body of water might be improved.

18. Ask students how humans might affect the water quality of their catchments.

19. Challenge the students to think of ways they themselves could improve aquatic habitats along their waterway.

In-class room adaptation
Break the students up into 4-6 groups giving each a litter tray of macroinvertebrates and water, various tweezers, pipettes and spoons. Ideally these have been collected from a range of different waterbodies.

Follow steps 14 onwards in the Lesson plan. 
Finally, ask the students to try to work out the likely sources of the macroinvertebrates and water they sampled. For example is one from a farm dam, a pristine stream or an urban waterway.

Diving Beetle Larvae. Photographs: Rhonda Butcher
Diving Beetle Larvae. Photographs: Rhonda Butcher

Back Swimmers. Photographs: Rhonda Butcher
Back Swimmers. Photographs: Rhonda Butcher


Create a critter
Give each student a “Habitat”, “Food” and “Protection” card from the Macro-Modelling Deck.
Get them to build a macroinvertebrate that fits their cards using craft and found objects.
Invite students to describe their creations, the parameters they were asked to meet and allow the class to comment on the animals’ features.

The macro movie
Have the students write and produce a film or play showcasing the adventures of several macroinvertebrates.

This could involve
costumed children, or
even stop-action

Our patch
Have students take on the macro-invertebrate monitoring at a local body of water. 

Macro media
Have the students create and display posters to explain the importance and role of macro-invertebrates in their catchment.

Secondary pathway
Have the students expand on the questions found in step 7 of the Lesson plan into independent research. These questions can be targeted specifically to sites near the school or student’s home.
Their findings can be presented via Powerpoint presentation or in terms of GIS mapping (if available).

Water Bug Worksheet (see download)
This illustration shows the correct colouring-in of the 
water bug worksheet.