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Maroubra Rock Platform

When I was a little kid, I spent tons time on our family beach trips pottering around in rockpools. I loved finding tiny starfish well-camouflaged against the rocks. I’d probe anemones with my finger just to watch them shrink away. And I could spend hours chasing crabs around the water’s edge.

One of my most exciting memories was when I poked a piece of driftwood into a pool and felt something grab the other end. I was completely surprised to find a huge Common Sydney Octopus that had decided to wrestle with me!

These rockpool investigations turned my trips to the beach into a learning experience about the incredible biodiversity of our oceans. They also filled me with a love for the sea that I have been lucky enough to turn into a career in marine science.

Rocky shorelines provide the perfect playground for budding scientists to begin exploring the fantastic diversity of species on our planet. This playground atmosphere makes them a perfect location for a homeschooling science field trip. In fact, kids may not even realise they’re learning! They can even act as a “natural laboratory” where primary and high school kids can run experiments and learn about science.

Best of all, rocky shores are a marine environment that’s easily accessible without getting wet (as long as you time your trip well)!

Getting to know rocky shorelines and the intertidal zone

Although they may seem barren at first glance, rocky shorelines are amazingly biodiverse and are home to many different species. Rocky shorelines fall within the intertidal zone, which is the area of land along the shoreline that is submerged underwater during the high tide and exposed to the air when the tide recedes.

The extreme changes experienced in intertidal ecosystems forms a strong environmental gradient over a short distance. To put it simply, an environmental gradient is a change in the physical aspects of an ecosystem. This strong environmental gradient makes rocky shorelines unique, as it allows scientists to explore the relationships between the physical environment and a species’ adaptations. Let’s take a look at why.

The intertidal zone can be broken into three main areas (or littoral zones) that are based on the tidal levels. These are known as the lower, middle, and upper littoral zones. Each of these areas provide different challenges for the animals and plants that live within them. Because of these different challenges, each area contains different communities of organisms that have cleverly adapted to survive within them.

Intertidal Species

Little blue periwinkle

Animals living in the upper littoral zone are the furthest from the water’s edge. Because of this, they have to stay comfortable during long periods out of the water and under the hot sun. The little blue periwinkle (Austrolittorina unifasciata) is one of the only creatures found here, as they can survive losing an astounding 70% of their body’s water content! These tiny snails conserve moisture by secreting mucous to seal their shells and clustering tightly together in small rocky depressions.

The middle littoral zone is submerged around twice a day as the tides change. The organisms that live here have a variety of adaptations to cope with big changes in temperature, salinity, and exposure. For example, barnacles have a small set of plates atop their calcium shell that they can seal shut when the tides are low to stay cool and wet. As the tide returns and the barnacles are resubmerged, they reopen these plates and poke out their feather-like appendages. Barnacles use these appendages, called cirri, to grab food from the water.

Rockpool

Some organisms that can’t handle drying out at low tide can still survive in the mid-littoral zone by living in rockpools. The cushion sea star (Patiriella calcar) and red waratah anemone (Actinia tenebrosa) are two of the most common rockpool inhabitants around Sydney.

Meanwhile, organisms found in the lower littoral zone need to cope with the pounding waves. Many seaweed species, such as Neptune’s necklace (Hormosira banksii), have developed strong, root-like structures called holdfasts to prevent them from being washed off the rocks. The bubble-like fronds that make Neptune’s necklace so distinctive also help it survive. These bubbles secrete mucus to stop the algae dehydrating and are buoyant to help catch the best rays of sun at the surface.

By understanding the different challenges in these zones, we can make predictions about how the different organisms that live in each zone should look and behave. This gives kids a great opportunity to improve their critical thinking and observation skills.

Let’s explore some intertidal communities!

Now that you’ve learned a little about the rocky shoreline, you can transform your next family visit to the beach into a fantastic learning experience in a few easy steps!

Step One: Plan your trip

The first thing to do when planning any rocky exploration is to check the tides. Low tide is the safest time to explore any rock platform and means you can observe creatures within the lower tidal zones. I like checking out the Bureau of Meteorology’s tidal predictions and weather warnings to time my trips perfectly.

Step Two: Build a Quadrat

A quadrat is a simple tool that helps biologists select random sample areas on a rock platform and assess species within them.

Quadrats don’t need to look perfect, so you can use anything vaguely stick-like that you already have at home to make their “frame”. Try taping together skewers, garden stakes, paddle-pop sticks, plastic straws, or just use sticks from your garden! I made mine out of aluminium foil by measuring out 50cm sheets and rolling/scrunching them into “sticks”.

Quadrat closeup

How to make a Quadrat

Materials

  • Four 0.5m sticks
  • Scissors
  • Tape
  • Ruler
  • String
  1. Measure your sticks and make sure they are half a meter (50cm) long – cut off any excess length if necessary.
  2. Place two of the sticks together to form a right angle with the ends of both sticks just overlapping.  Wrap the tape around the point where the two sticks cross over several times.
  3. Repeat step 2 with all four sticks to form a square frame
  4. Divide the quadrat into quarters by tying a piece of string across the halfway point of two of the parallel edges.

Step Three: What to bring

The beauty of intertidal exploration is that you can do it with almost no gear. Nevertheless, there are still a few essentials you should take on any trip, including:

  • Sunscreen and a hat
  • Enclosed shoes (Rock platforms can be quite slippery and sharp. Avoid wearing thongs as they won’t protect your toes and are easy to slip over in!)
  • Your quadrat
  • A printout of our worksheet with a clipboard and pencil
  • Optional: A phone or tablet to take photos and look up unknown critters. (Top tip: Chuck your phone in a Ziploc bag to prevent water damage!)

Step Four: What to do once you get there

Be safe and watch the waves: It’s important to keep an eye on the ocean whenever you’re on the rocks. Make sure one person is always watching the waves when you’re conducting fieldwork.

Quadrat on rocks

Use our worksheet: Place the quadrat at three different intervals along the rock platform. Start close to the water in the lower littoral zone and finish up past the high tide mark at the upper/sublittoral zone. Each time you place the quadrat, use our list of common intertidal organisms to try and identify any species that you can find within the quadrat. Count the number of each species that you find and record your observations on the worksheet.

Take a ton of cool pics: If your kids find an organism that they can’t identify or that they think looks super cool, encourage them to take a picture! There are some great online resources they can use to identify plant, algae, and animal species once they get back home. I personally love the Australian Museum’s Animal Factsheets. This comprehensive identification guide published by Avondale University College is another great resource.

Photographing marine life can also give kids a first taste of citizen science. Websites like iNaturalist allow you to contribute to the scientific community by recording and sharing your observations. Fellow citizen scientists can even help you to crowdsource identifications.

Our worksheets are a great way to get kids thinking scientifically and exploring the natural world. This activity is an excellent addition to any homeschool program. By exploring our beautiful Aussie coastlines and the creatures living within them, I hope that more kids can fall in love with the incredible biodiversity of the ocean!