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How does the acidity of lake water affect the hardness of Zebra mussel shells? Featured science projectScience project video


This science fair project was conducted to determine how the acidity of lake water affects the hardness of Zebra mussel shells. It would be interesting to know if the higher levels of acidity have the effect of softening or weakening the exoskeletons of aquatic invertebrates. s.This science fair project was done using Zebra mussels that were obtained from lakes with different levels of water acidity.


A lake with more acidic water will produce Zebra mussels with softer shells.

Scientific Terms

Zebra mussels, clams, asymmetry, pH, siphon, branchial chambers, gills


Zebra Mussels

Zebra mussels belong to a family of clams that have hard, elongated and asymmetrical shells. They are marked by alternating light and dark bands and normally live in slow moving or still fresh water. Zebra mussels will locate any hard surface under water and attach themselves to it. They are often found attached to rocks, buoys, boat hulls and submerged woods.

Zebra mussels usually require a small concentration of calcium in the water to grow their shells. They grow best and most quickly  in waters of pH values between 7.4 and 8.4. Waters with pH levels below 6.8 is thought not to be conducive for their growth because the acidic waters may dissolve the shell. Although Zebra mussels can survive for a short while at temperatures below freezing, they thrive at temperatures between 20°C to 25°C. Apart from temperature, Zebra mussels are also sensitive to chemicals that are dissolved in the water and they can also  detect touch and gravity.

Zebra mussels are filter feeders. They draw water into their incurrent siphon and then into the branchial chambers where their gills filter food from the water. The waste water  then exit through the excurrent siphon. Their diet consists mainly of single-cell organisms such as bacteria, protozoa, plankton and algae.

There are many factors that determine the acidity of  a lake, such as the amount of acid rain that the lake receives, whether livestock is found nearby, and whether nitrogen-based fertilizers are used in the vicinity. Also, the soil type in the surrounding catchment area plays a part in determining the acidity of lake water. If the soil is very alkaline in nature, it will neutralize the acid rain as the rain water seeps through the soil, on its way into the lake.

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Complexity level:
Project cost ($):
Time required:
1 day to prepare, 1 day for observation
Material availability:
You will need access to a hardness tester. You will also require transportation to travel to the lakes to gather mussel samples
Safety concerns:

Basic safety requirements