Objectives
>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
Duration
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
>Pipettes
>Spoons
>Tweezers
>Field guides
>Butcher’s paper, pad or whiteboard
>Macroinvertebrate poster
>Macro-Modelling Deck (see below)
>Water Bug Worksheet
Water Mite. Photograph: Rhonda Butcher
Background
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.
Vocabulary
Macroinvertebrate
Gill
Larvae
Sensitivity
Food web
Riffles
Runs
Pools
Glides
Pollution
Water quality
Nymph
Adaptation
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.
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