Could worms save the world?

Lesson overview

This lesson focuses on marine sediment as a habitat as a whole, with an introduction to the habitat of the continental shelf, the subject of the Convex Seascape Survey. Students will visit the Isle of Arran off the south-west coast of Scotland to find out more about the marine sediment. Students can also get hands-on with worms to see how they help to make this muddy bottom suitable for other forms of life.

Learning outcomes
  • Describe features and location of continental shelf habitats
  • Explain how ocean sediment forms
  • Understand how human activity affects the seabed
  • Analyse the role of worms in creating and restoring a healthy seabed

See the Fact Sheet All about the continental shelf for background information on the continental shelf. The wormcrete activity needs five days for the worms to do their ‘thing’. This can either be done by the teacher or with students as a shorter preparation activity. See the Activity Overview Wormcrete activity for further details.

Lesson steps

1. Introduction to the Isle of Arran and the continental shelf (10 mins)

Use slides 2 to 5 to connect to the previous lesson’s learning if you have taught this, then­ introduce the learning objectives to the class. This section then moves on to an overview of the continental shelf. While the continental shelf is not a traditional blue carbon habitat as it does not directly absorb large amounts of carbon dioxide, it is a critical store of carbon contained in the sediment.

Use slide 8 to gather a quick emoji view of how the class views worms. This activity will be repeated at the end of the lesson to see how views may have changed. Slides 9 to 11 give a basic overview of the continental shelf as well as its global range shown as the paler blue area on the map. Slides 12 to 14 introduce the location for this lesson, the Isle of Arran in the UK, and some teachers may wish to reinforce students’ use of geographical descriptions using compass points. An atlas or map of the UK may be needed to show the location of the Solent in the context of the UK in more detail.

2. Marine sediment (15 mins)

This section focuses on the marine sediment. It will be useful if students have already studied soil as a comparison to this land-based equivalent will make it simpler for students to work through this section.

Depending on the ability of your class, you can start this section with the quote on slide 16 from the groundbreaking marine biologist and environmentalist Rachel Carson. Alongside her work in getting DEET pesticides banned from use in agriculture in the USA and beyond, she is renowned for her study of the ocean and her lyrical descriptions of the marine world.

The next step is to use slide 17 to have your students imagine that they are standing on the seashore. This is the beginning of the continental shelf, the gentle slope towards the deep that can extend for tens of metres or hundreds of kilometres depending on where you are in the world.

Then hand out the cloze exercise on the Student Sheet and have students work through this independently or in pairs to show the sheer variety of different ways in which the sediment is formed. Slide 19 summarises this information. Although most of the sediment comes from land sources and through the shells, bodies, and poo of living things, it is fun to consider that a sandy or muddy shore can also be made up of cosmic dust and volcanic eruptions centuries and millennia ago.

3. The Convex Seascape Survey goes to Arran (10 mins)

This section of the lesson focuses on the impact of human activity on the continental shelf habitat. This is the area where most fishing happens and through a series of three videos, students can see how bottom trawling can change the seabed from abundance to scoured mud in a matter of minutes. The Convex Seascape Survey team were focused on how much carbon is stored in the sediment as well as how different animals can affect its health. However, as different areas around Arran have been impacted by human activity such as fishing, their work also shows how seabed health can be affected.

The first video shows a cup coral nestling in amongst a strange (here pink) colonial animal known as bryozoans. The aim of this video is to show the beauty and strangeness of the seafloor around Arran.

The second embedded video clip is an animation from Greenpeace that shows how fishing techniques can damage the life found on the seafloor.

The final embedded video contrasts the view of a healthy seafloor with a view of the seafloor after trawling.

Students may be shocked by this change, and the next section of the lesson shows how through protecting areas of the ocean, the seabed can be restored and it all starts with the wonderful worm.

4. Wormcrete activity (15 mins)

Slide 26 shows how marine protected areas work. In this case, it is a community area developed by Arran COAST. A marine protected area means that certain activities are banned and gives nature a chance to restore itself.

Remind students of the scoured seabed video and the nature of the sediment. Much life on the seabed requires a hard seafloor to grow back rather than soft mud or sand that may move around a lot with waves, tides, and currents. This is where worms come in. Hand out the Activity Sheet Wormcrete activity record sheet.

The activity sheet takes students through three steps of investigation skills: predicting, observing, and concluding. Follow the steps on the Activity Overview and record sheet.

In terms of setting up this investigation, there are a few issues to consider. Worms will need to be removed carefully before the ‘crumble test’. This should be done by an adult, and worms can be placed in a suitable area outdoors, or in a container with soil as an interim step. It would be wonderful for students to have the samples of soil per small group, and to remember that this will require the careful removal of 20 to 30 worms by staff. A simpler method would be to have a single set-up and select students to come up to test the soil. It may mean that fewer students have the chance to have a sensory experience, and this is balanced with your worm removal patience and skills.

At all times during the investigation connect the work with earthworms and soil to the marine worms and sediment.

5. Wonderful worms writing (10 mins)

This final stage emphasises the importance of worms to the marine environment. Slide 31 summarises the role of worms, while the embedded video on slide 32 shows how worms allow for a wider range of life to thrive. Students will be able to see a forest of brittle stars waving their arms/legs in the water. There is also a pair of edible crabs, and in background, students will be able to see transparent sea squirts and pink whorls of bryozoans and algae.

Conclude the lesson by revisiting the emoji view of worms and a writing exercise to consolidate the importance of wonderful worms to a healthy seascape.

Alternative activities

For some students and contexts the wormcrete activity may be too complex. There are a range of craft-based activities exploring seabed life that could be used as alternatives. These include making models of a catworm, sea potato, brittle star, or cockle.