Using Mussels to Monitor the Environment

Have you ever been at a restaurant and eaten steamed mussels? Mussels are more than just a tasty appetizer. They are also a great tool for testing water quality!

Mussels are aquatic invertebrates that have a hard outer shell. Members of this group are called molluscs because they are part of the phylum mollusca. Around 85 000 different species of molluscs are believed to exist. 

Did you know?

Molluscs are the second largest group of invertebrates on Earth. The largest group of invertebrates are arthropods, which include insects, spiders and crabs.

Mussels can live in both saltwater and freshwater. They attach themselves to hard surfaces, so you can sometimes see them on rocks and boat docks.

Mussel body parts and functions

Mussels have soft inner bodies and hard outer shells called valves. Because mussels have two shells, they are known as bivalves (“bi” meaning two). Clams, oysters and scallops are also bivalves.

Outside the shell you may see the mussel’s foot. This is a muscular organ that helps the mussel move from place to place. Large muscles called adductor muscles keep the shells tightly closed.

Did you know?

You also have adductor muscles. They are in your inner thighs.

Just inside each shell is an organ called the mantle. The mantle is what makes the shells. Another important organ is the gills. Mussels have two pairs of gills. Gills have three functions:

1. Get oxygen out of water (respiration). This is like the gills on fish.
2. Filter food out of water and move it to the mussel’s mouth.
3. Provide a place for baby mussels to develop.

Mussels eat microscopic plants called plankton. They also eat other microscopic animals. They get the food by sucking in water through a tube called a siphon. It then passes by the gills which filter out bits of food. Then the mussel gets rid of the leftover water through another siphon. 

Did you know? 

A single mussel can filter 38 litres of water a day!

Mussels filter a lot of water when they eat, so they can be a great tool for testing water quality. Scientists can learn about the types of chemicals where the mussel lives by looking at what mussels take into their bodies. 

Scientists have even created artificial mussels that can measure trace metals in water. Trace metals are things like cobalt, copper and iron. They are normally at very low levels in the environment. When high levels of trace metals build up in water, they can harm both wildlife and humans.

The problem of bioaccumulation

If water has trace metals in it, animals like mussels will take those metals into their bodies. Over time, the metals can build up or accumulate in the mussel’s tissues. This process is called bioaccumulation.

Bioaccumulation is very dangerous because animals like mussels are at the bottom of many food chains. In other words, many different animals eat mussels, even humans! And any animal that eats a mussel will also take in the trace metals in the mussel’s tissue.

How mussels help with environmental monitoring

It is important to keep an eye on pollution in food chains. To do this, scientists use biomonitoring. Biomonitoring is when scientists use living things to measure the health of the environment.

Living mussels are often used as biomonitors. Scientists collect them from the water and measure the levels of trace metals in their tissue. This helps them find out how much metal is in the water and the environment around it.

Artificial Mussels

In 2007, researchers in Hong Kong created the Artificial Mussel (AM). Since then, scientists have been able to use AMs as biomonitors instead of living mussels.

AMs are small plastic tubes containing a gel. Researchers place the AMs in baskets and lower them into the water. Water enters the AM through openings at the end of the tube. A gel inside traps trace metals. Metals accumulate in the gel in much the same way they would inside a living mussel. 

AMs were tested in Australia between 2009 and 2011. Scientists placed them in ten locations they thought were at risk for metal accumulation. The gel inside the AMs contained many trace metals after four weeks in a river. The metals included cadmium, copper, lead, mercury and zinc. Tests like these help scientists find out what areas might be a health risk for wildlife and humans.

As you can see, mussels are important in many ways. They are part of food chains that sustain life in the water and on land. They also help us find pollution in rivers and oceans. They are so popular that scientists now make artificial mussels to help with all the work. Not bad for an animal that spends so much time hiding in its shell!