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Identify and Define

The first phase of the design process will see you learn about Codium fragile and the challenges facing the intertidal zone.

Codium fragile is a unique, native, branching form of seaweed, which is commonly known as Dead Man's Fingers!

Found along the Greater Sydney Coastlines, Codium fragile is extraordinary in its ability to produce oxygen and is an amazing ocean cleaner, absorbing nutrients and heavy metals helping our oceans stay healthy. Codium is an important part of the intertidal zone, where the ocean meets the land. It provides habitat for many different sea animals and is an integral part of the ocean food web. Watch this video to find out more!


Why does Codium fragile need our help?

Billions of people rely on the ocean for their livelihoods. Our oceans, seas and marine resources are under continual threat from pollution, warming and acidification which disrupts marine ecosystems and the communities they support. Marine environments need our protection. 

Classifying Codium

The science of naming living things is called Taxonomy. It involves finding living things, studying them, describing them and giving them a correct scientific name. 

Scientists give each organism (living thing) a unique name by grouping them according to how similar they are, and each group (genus) is given a name (sort of like a family). A family has a shared last name, and each person has a unique first name, put together they give you your name.  

Scientific naming ensures that every living thing has its own unique name, so there are no mix-ups!  

[Scientific Name = Genus + Species]

In this case, Codium is the genus, and fragile is the species so its scientific name is Codium fragile.

To make things a little easier for people that are not scientists, livings things often have a common name. The common name for Codium fragile is Dead Man's Fingers

Can you guess why?...... 

Seaweeds are algae that live in the salt water of the oceans. They come in all shapes and sizes, including microscopic plankton to kelps taller than your house! 

There are three main algae divisions, and they are divided by the colour of their chlorophylls - the pigments that soak up the sun's energy for photosynthesis. These divisions are green, red and brown and every seaweed you see can be put into one of these groups. 

What division does Codium belong to?  GREEN     (Known as Charophyta) 

Features and adaptations of Codium fragile

Seaweed parts are named differently than land plants. We're used to saying "leaf" and "roots" and "stem", but with seaweeds we use other words.  

Seaweeds are still called a plant but unlike land plants the entire plant photosynthesizes. What we call leaves on a land plant we call "blades" on seaweeds.  Some seaweeds have floats which are filled with gas to help them stay upright under water. A stipe is the part that attaches the plant to the holdfast. These can also be called branches. The holdfast actually holds the plant down. It doesn't act like roots; its purpose is to grip the plant to the surface. 

Not every seaweed will have all the parts. Seaweeds are highly variable, meaning they can be very different from each other. Let's take a closer look...what parts can we see? 

Find out more about Codium adaptations here!

Preparing a Herbarium specimen for research 

​The National Herbarium of NSW is a giant library of 1.43 million dried plant specimens (including seaweeds), and just like a library – these plants are constantly being ‘checked out’ for research. Watch the movie below to see how to create a Herbarium sample, so you can continue your research! Try this with seaweed if you can, otherwise another plant sample would allow you to learn this scientific skill. It is VERY important to only take the amount you need so as not to impact on the health of the plant.

If you choose to use seaweed, remember it is a water plant and you will need to; 

  • Use Watercolor Paper to press your seaweeds onto 
  • Change your newspaper every day for the first 3 days (if it is wet) 
  • Put you seaweed specimen in a warm dry place while it is drying out 

Codium fragile life cycle

Take a look at the fascinating life cycle of Codium fragile! Can you think of ways that this is similar to a plant you might find on land? Can you think of ways that it might be different? What are some of the structural and behavioural features of Codium fragile that help support its survival? Click on below to listen to a description of the life cycle.

Life in the rockpool

Learn more about the interconnections of the intertidal zone. 

Introduce yourself to five of Codium fragile’s rockpool neighbours! Guess what the animal is then click on the image to learn more.

Threats to the Intertidal Ocean Zone and Codium fragile 


Intertidal zones are areas of the shore that are above the water at low tide and below at high tide, such as rock pools. These areas are important habitat for many living things along coasts.  

Coasts and intertidal zones are facing a barrage of threats caused by people. These include;
1. Pollution 

  • When storms rip through coastal areas, they destroy important habitat and deposit silt and debris across the coast.  
  • Tons of plastic pollution is clogging our oceans, drowning and choking marine mammals and bumping into Codium Germling, so they cannot fasten onto the rocks below. 

2. Climate change-related impacts such as -

  • Rising sea levels and increased erosion 
  • Strengthening storms 
  • Ocean acidification (too much Carbon Dioxide and not enough oxygen for living things grow) 
  • Rising temperatures 

“Our actions can have a huge effect on the survival of species like Codium. Let’s work together to protect these important seaweed species and in protecting them we are protecting the incredible life beneath our ocean.” Dr Yola Metti, Phycologist  

Activities - Identify and Define

1. Read and write!

Read the story Codi and the Striped Pyjama Squid by Dr Stephen Skinner. Rewrite the story in your own words.

2. The life cycle of Codium fragile

Listen to the life cycle audio above and examine the life cycle diagram. Complete this matching activity to identify parts of Codium fragile's life cycle. 


3. Codium STEM journal

Download the Project Codium STEM Journal found HERE and record three ways Codium fragile helps us and the other living things in the Intertidal Zone and three reasons why Codium fragile needs our help.

4. Be a Citizen Scientist!

Take a walk along the rocks at your nearest beach and see if you can find any Codium fragile! Record your siting on the Citizen Science app inaturalist