DIY experiment: the filtering power of kūtai (mussels)

Investigate the filtering power of mussels! This simple experiment was developed in conjunction with SeaWeek and supported by Auckland Council.

You will need:

- Fresh green lipped mussels from your local supermarket
- 5 litres of murky sea water from a local beach (the murkier the better)*
- 2 x 1000mL beakers or clear containers with wide necks like preserving jars
- Watch or timer
- Cellphone or device with timelapse video recording capability

If you can’t visit a beach to collect murky sea water, you can make your own at home by adding 35 grams (about 6 teaspoons) of salt to 1 litre of tap water. To make it cloudy/murky, add 1 teaspoon of flour or 2-3 teaspoons of moist soil or mud.

Let's get started!

- Fill your two clear containers with equal amounts of cloudy sea water. Keep the water below 20°C.
- Place one green-lipped mussel into one of the containers. This will be the test sample. Leave the other container with no mussel in it as the control.
- Time the experiment and abserve the mussel in action as it filters the sea water. Stop the experiment when the sea water becomes clear. Take photos throughout the experiment or take a time lapse movie.

Express your results as time taken for sea water to clear / 1 litre for 1 mussel. This is your filtration rate.

Further experiments you might like to try:

- Increase the number of mussels sequentially and record their filtration times. Predict what might happen first.
- Collect your data and present it in a table. You can also express your results as a graph. What does the information in your table or graph tell you? Does it differ from your prediction? Explain why.
- Repeat this experiment, but this time weigh the mussels and express your results by weight instead of number.
- Try a different type of shellfish (like cockles and pipis).