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Mussels on a rocky coastline

Mussels on a rocky coastline (nattrass, iStockphoto)

STEM in Context

Using Mussels to Monitor the Environment

Courtney McDermid

Summary

Mussels are a kind of invertebrate that filter food out of the water they live in. This makes them a great tool for monitoring environmental water quality and tracking bioaccumulation in aquatic food webs.

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.

Cluster of mussels on rocks at low tide
Cluster of mussels on rocks at low tide (Source: esp2k via iStockphoto).

 

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.

Mussel showing the locations of the valves, adductor and foot
Mussel showing the locations of the valves, adductor and foot (Let’s Talk Science using an image by Rainer Zenz [CC BY-SA] via Wikimedia Commons).

 

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.
Mussel showing the locations of the siphons, gills, mantle and foot
Mussel showing the locations of the siphons, gills, mantle and foot (Let’s Talk Science using an image by Rainer Zenz [CC BY-SA] via Wikimedia Commons).

 

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. 

Mussel Clearing (2011) Eric Heupel (1:00 min.)

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.

Illustration of how contaminants, like trace metals, move up the food chain
Illustration of how contaminants, like trace metals, move up the food chain (Let’s Talk Science using iStockphoto images by RUSSELLTATEdotCOM and athykonkle).

 

Image Labels

1. Contaminants, like trace metals, are washed into the water.
2. Mussels take in the water and concentrate the contaminants in their tissues.
3. Mussels are eaten by small fish. The fish also concentrate the contaminants in their tissues.
4. Small fish are eaten by larger fish.
5. The larger fish have accumulated the contaminants from the smaller fish. These fish may be eaten by humans.

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. 

Artificial mussel
Artificial mussel (Let’s Talk Science based on an image in Innovative ‘Artificial Mussels’ technology for assessing spatial and temporal distribution of metals in Goulburn–Murray catchments waterways, Victoria, Australia: Effects of climate variability (dry vs. wet years).

 

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!

 

Starting Points

Connecting and Relating
  • Have you ever eaten mussels? Did you like them? Why or why not?
  • Do you ever think about the contaminants or toxins may be present in seafood, like mussels and fish? Why/why not?
  • What steps can you take to make sure that you do not consume too many toxins in your diet? Explain.
Connecting and Relating
  • Have you ever eaten mussels? Did you like them? Why or why not?
  • Do you ever think about the contaminants or toxins may be present in seafood, like mussels and fish? Why/why not?
  • What steps can you take to make sure that you do not consume too many toxins in your diet? Explain.
Relating Science and Technology to Society and the Environment
  • Is it right (ethical) to use living organisms in biomonitoring? Why or why not?
  • Who should pay for biomonitoring – governments or industry? Explain.
  • How might the information collected from biomonitoring programs be used to protect people and the environment? Explain.
Relating Science and Technology to Society and the Environment
  • Is it right (ethical) to use living organisms in biomonitoring? Why or why not?
  • Who should pay for biomonitoring – governments or industry? Explain.
  • How might the information collected from biomonitoring programs be used to protect people and the environment? Explain.
Exploring Concepts
  • What is biomonitoring? Why is it important?
  • Why are filter feeders such as mussels useful for identifying possible contaminants in water bodies?
  • What toxins can be detected when mussels are used as biomonitors?
  • Using zebra mussels as an example, explain the concept of bioaccumulation in a food chain.
  • Draw a picture of a mussel that shows its key body parts. Label the body parts in your diagram.
Exploring Concepts
  • What is biomonitoring? Why is it important?
  • Why are filter feeders such as mussels useful for identifying possible contaminants in water bodies?
  • What toxins can be detected when mussels are used as biomonitors?
  • Using zebra mussels as an example, explain the concept of bioaccumulation in a food chain.
  • Draw a picture of a mussel that shows its key body parts. Label the body parts in your diagram.
Nature of Science/Nature of Technology
  • What new technology is being used instead of live mussels for monitoring aquatic environments? What are the advantages of this technology?
Nature of Science/Nature of Technology
  • What new technology is being used instead of live mussels for monitoring aquatic environments? What are the advantages of this technology?
Teaching Suggestions
  • This article supports teaching and learning of Biology, the Environment and Pollution related to the topics of bioaccumulation, environmental monitoring, filtration & distillation, invertebrates, trophic levels and water quality. Concepts introduced include invertebrates, phylum, bivalves, gills, respiration, plankton, siphon, trace metals, bioaccumulation, food chains and biomonitoring. 
  • Before reading the article, teachers could have students conduct a Vocabulary Preview to identify key terminology and activate prior knowledge they may have encountered before. Ready-to-use reproducibles for this article are available to download in [Google doc] and [PDF] formats.
  • After students have read the article, teachers could have students use a Key Ideas Round Robin learning strategy to identify the key ideas in the article through individual thinking time and working collaboratively in small group discussions. Ready-to-use reproducibles for this article are available to download in [Google doc] and [PDF] formats.
  • To conclude the lesson, have student groups share their conclusions from the Key Ideas Round Robin.
Teaching Suggestions
  • This article supports teaching and learning of Biology, the Environment and Pollution related to the topics of bioaccumulation, environmental monitoring, filtration & distillation, invertebrates, trophic levels and water quality. Concepts introduced include invertebrates, phylum, bivalves, gills, respiration, plankton, siphon, trace metals, bioaccumulation, food chains and biomonitoring. 
  • Before reading the article, teachers could have students conduct a Vocabulary Preview to identify key terminology and activate prior knowledge they may have encountered before. Ready-to-use reproducibles for this article are available to download in [Google doc] and [PDF] formats.
  • After students have read the article, teachers could have students use a Key Ideas Round Robin learning strategy to identify the key ideas in the article through individual thinking time and working collaboratively in small group discussions. Ready-to-use reproducibles for this article are available to download in [Google doc] and [PDF] formats.
  • To conclude the lesson, have student groups share their conclusions from the Key Ideas Round Robin.

Learn more

Check Out These Mussels: Minneapolis Using Mollusks To Monitor Water Quality (2019) 

Video (2:02 min.) from WCCO News shows mussels at work monitoring water quality in the city.

Can One Billion Oysters Clean NYC's Harbor? (2015)

Video (3:20 min.) from the Wall Street Journal of New York City students reintroducing oysters (bivalve molluscs) to their harbour to help clean the water and learn many other things along the way.

Mussels (2016)

Article by Marine Stewardship Council for kids describing mussels, their food and habitat.

Bivalve Anatomy (freshwater mussel)

Video (9:51 min.) dissection of a mussel.

References

Kelly, B. C., Ikonomou, M. G., Blair, J. D., Morin, A. E. & Gobas, F. A. P. C. (2007) Food web-specific biomagnification of persistent organic pollutants. Science, 317(5835), 236-239. DOI: 10.1126/science.1138275

Kibria, G., Lau, T.C. & Wu, R. (2012) Innovative ‘artificial mussels’ technology for assessing spatial and temporal distribution of metals in Goulburn–Murray catchments waterways, Victoria, Australia: Effects of climate variability (dry vs. wet years). Environmental International, 50, 38-46. DOI: 10.1016/j.envint.2012.09.006>

Nordsieck, R. (n.d.). The blue or common mussel (mytilus edulis) The Living World of Mollucs.

The Oxford Pocket Dictionary of Current English. (2020) Mussel.

Richman, L. and Somers, K. (2005) Can we use zebra and quagga mussels for biomonitoring Contaminants in the Niagara River? Water, Air, and Soil Pollution, 167, 155-178. DOI: 10.1007/s11270-005-0083-6

Wu, R.S.S., Leung, K.M.Y., Lau, T.C., Fung, W.K.M. and Ko, P.H. (2007). An 'artificial mussel' for monitoring heavy metals in marine environments. Environmental Pollution, 145(1), 104-110. DOI: 10.1016/j.envpol.2006.03.053