Beachcombing Guide – What am I looking at?
Beachcombing Guide – What am I looking at?
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Ever felt the urge to sift through the seaweed to see what’s there or dabble in a tidal pool?
We all seem to be fascinated with pottering about in rock pools, and being in Western Australia with its long and beautiful coastline is an excellent place to do it! The south coast of WA is rugged and wild, with changeable ocean and weather conditions. This combination of open coast and wild weather can leave some interesting flotsam and jetsam on the shore. On the Cape to Cape track and Cape Le Grand tours we walk along numerous beaches, allowing plenty of opportunity to scavenge.
The piles of algae and seagrasses found on the beach are known as sea wrack. It is made up of an assortment of seagrasses, algae, shells, and the remains of animals such as sponges and sea urchins. This detritus provides a prime feeding place for swarms of amphipods, insects, larvae and other fauna. These tiny creatures play a large role in breaking down organic matter and recycling nutrients – and are an important food source for fish and birds. If you’re willing to carefully dig through it you could be rewarded with a sea horse, urchin or a mermaid’s purse – the egg case of Port Jackson or catsharks.
A common sight along the beaches, especially those frequented by recreational fishers, is the weeping toadfish, commonly referred to as a blowie. As an inedible fish, frustrated fishermen tend to discard them when caught. However, blowies play an important role in marine ecosystems, as they feed on almost anything they can scavenge, thereby helping to keep our coastal waters clean. Cuttlebones are also frequently seen. The ‘bone’ is the internal shell of cuttles (or cuttlefish), a relative of squid and octopus, and it is often given to caged birds to supplement their diet.
Walking along the tideline is the best place to look as this is where everything is deposited. Other animals and shells you might come across include sponges or coral, both actually animals, what you find is the skeleton; bluebottles and other jellyfish, turban snails, abalone, clam, scallop, ram’s horn and cowry shells. Both cowries and abalone are easily recognisable due to their shape and shiny, colourful shells. The ear-shaped shell of an abalone is smooth and shiny on the inside to protect the soft body from damage. There are more than 60 species of cowries living along the Western Australian coast, providing lots of variety in shape, size and colour.
Urchins, sea hearts (heart urchins) and sand dollar skeletons can all be found amongst the seaweed. Along with their more familiar relatives, the starfish and brittle stars. As a rule urchins are round, sea hearts are oval and sand dollars are rather flat. When alive, the urchins and sea hearts are covered with spines, although they eventually break off when they die leaving the familiar mauve ball shape.
Closer to the water’s edge can be pipis; small, wedge-shaped and colourful bivalves that live just below the sand surface in the surf zone. As the waves go out, you may see them burrowing back into the sand. On the rocks you can find limpets, chiton and periwinkles. These hardy animals are adapted for life on rocky surfaces in the wave washed intertidal zone but can be dislodged and end up on the beach. Chiton have a distinct set of eight separate shell plates overlapping on their backs, while limpets are the simple inverted cone shell. Both these animals rasp away at the limestone rocks, eating the algae on them. They are believed to be responsible for about 2 cm of erosion along the coast each year.
Sometimes dark slimy blobs wash up onto beaches during late summer and throughout autumn. These blobs are actually sea hares, a type of mollusc. They have a similar defence system to squid being able to squirt a purple secretion when threatened. They also produce a toxic slime which can be harmful to dogs. Occasionally, something larger will end up on the beach or be uncovered by the waves, particularly after storms, including whale bones, juvenile turtles, seals or sea snakes.
It is important to remember to use caution when lifting shells or moving seaweed as animals may still be alive. Please do not to remove anything from the beach besides rubbish; shells, weed and bones all contribute to the coastal ecosystem. Take photos, leave only footprints.
Imogen Webster – IO Guide and Marine Biologist
