Sensational Seas: Educator Resource

The ocean covers more than 70% of the Earth's surface and plays an important role in sustaining life on our planet. By providing children with opportunities to learn about the sea, including its inhabitants, we can support a connection to the natural world at an early age.

We have collated some information below to help support you in implementing these activities and to extend our science inquiry skills in investigating the seas.

Seashells as a home

Seashells are more than just beautiful treasures found along the shore. They are made by marine molluscs, and the shells grow as the animal does. Some animals, like seasnails or the nautilus, have spiral-shaped shells that grow as the animal builds new layers of shell around the mouth. Bi-valves, like pipis or clams, have two shells that they hold together, and the new layers of shell build up on each shell along the opening. Cuttlefish have an internal shell with a hard protective layer on top and a soft underside.

If you look carefully at a shell you can see the story of its life. Like tree rings, you can tell good years by wide spacing between lines and tough years by small growth increments. You can also find places where the shell was damaged or cracked, and new shell grew over the spot to repair it. On a cuttlefish shell you can sometimes see the black lines which mark a point in its life where it squirted ink to escape a dangerous situation. This takes a lot of energy, and most animals only squirt ink a few times (or not at all!).

When the animal dies, its shell is left behind. Sometimes, other creatures, like an octopus or a hermit crab, will take up residence in the shell. Eventually, the shell will break down into small parts and help form the sand on our beaches. Sand is also made up of crushed corals, rocks, and bones. Sand made mostly from granite will refract the light and make the water look a beautiful aqua colour.

Seaweed and marine plants

Marine plants are split into two categories, true plants (seagrasses and mangroves), and algae (kelp, seaweed and phytoplankton). All of these photosynthesise just like land-based plants do and require sunlight to live. Because of this, you can tell roughly where a seaweed grows based on its colour. Bright green seaweeds and seagrasses live in the shallowest places, closest to the sun. Some of these are even completely out of water at low tide. Brown seaweeds live a little further down and are submerged their whole lives. Think of the tall kelp forests. Red seaweeds live the furthest from the sun, and their red colour lets them absorb the sunlight that makes it that far down.

On the beach, you might also find pink or white seaweed. This is just seaweed that has died and been bleached by the sun. It makes some beautiful colours! On the beach, you might also find a holdfast. This looks like a small, twisted lump of wood with a single stem rising from the middle. This is the part that the seaweed uses to attach to the rock. If you flip it over, you might even find a small piece of rock glued to the bottom. The glue that seaweed makes to attach itself to a rock is stronger than the strongest superglue we have.

There are a lot of animals in the ocean that could be mistaken for plants. Anemones latch onto rocks (although there are free-floating anemones!), and look like bright flowers. Coral is an animal, and the rigid structure we find washed up on the beach is the skeleton. However, coral lives in a symbiotic relationship with algae. The algae grows inside the coral and uses photosynthesis to create energy. This energy is passed on to the coral, allowing it to live in low-nutrient waters. Other animals that look like plants include sea tulips, sea lilies, feather stars, and nudibranchs.

Camouflage in the ocean

Why do so many marine animals look like plants? The answer is camouflage! One beautiful example of this is the leafy sea dragon. Living on the south coast of Australia from just west of Melbourne to just north of Perth, these fascinating creatures use their protrusions to blend in with the seaweeds of their habitat.

Other animals use counter-colour camouflage to hide in their environment. Many animals, including dolphins, sharks, whales, and penguins, have light-coloured

tummies and darker backs. The dark colour is thought to help them blend into the dark ocean when seen from above, and the lighter tummy is thought to make them harder to spot against the sunshine on the water’s surface.

Our seas really are sensational! By connecting with our oceans and building their awareness and understanding, our children will be able to help us protect these amazing places.

Sensational Seas: Seashells by the Seashore

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