Lots o’ flotsam

If you wander along Cottesloe’s beaches in winter a fascinating feast of flotsam will greet you – an amazing array of marine creatures and plants washes up after the storms. Coastcare member Mike Gregson took a walk along the beach and describes some of the wonders you may find. Robyn took the pictures.

Many thanks to Loisette Marsh for checking the information. Click here to see her paper on Animals of the Cottesloe Reef Fish Habitat Protection Area (PDF 20KB, opens in new window).

Click on an image for a bigger picture (opens in new window).

Seaweeds are many-celled marine algae and are classified according to their pigment type - green, brown or red. Examples of green algae are Sea Lettuce (Ulva lactuca) and Sea Grapes (Caulerpa racemosa). Familiar types of brown algae are Kelp (Ecklonia radiata) and the many species of Sargassum with their bubble-floats.
Read more about seaweeds.
Seagrasses are flowering plants that have adapted to living in the sea. They are vascular plants with roots, stems, leaves, pollen and seeds, and have creeping stems like couch grass. They can be roughly classified as paddle-weeds (Halophila), wire-weeds (Amphibolis) and ribbon-weeds (Posidonia).
Read more about seagrasses.
Corals (and their kin) includes corals, hydroids and sea anemones, all representing the polyp form of the phylum Cnidaria.
Read more about corals.
Jellyfish are also cnidarians, like corals, but we usually see them in the free-swimming medusa stage of their life cycle. Commonly stranded after a storm is the balloon-like bluebottle (Physalia) which is related to the Portuguese Man-o-War.
Read more about jellyfish.
Lace Corals are not true corals. They are the skeletons of a different group of tiny animals called bryozoans.
Read more about lace corals.
Sponges are usually found on the beach after their soft parts have decomposed, leaving only the skeleton which is usually made of a brown horny material. This contrasts with the brilliant colours that characterise many of the living sponges.
Read more about sponges.
Molluscs come in many diverse forms including bivalves such as as cockles and mussels which have two shells hinged together , while the sea snails have a single spiraled shell. The hard remains of cephalopod molluscs can be found in the form of cuttle-bones.
Read more about molluscs.
Crustaceans. Sand crabs dig holes in the beach and rock crabs hide in crevices. Barnacles may not look like typical crustaceans but they are highly modified versions of the crustacean body plan. Goose barnacles are the ones often seen attached by a flexible stalk to cuttle bones and wireweed.
Read more about crustaceans.
Sea Stars (or Starfish) and Sea Urchins both belong to the group of spiny-skinned animals called echinoderms. They move using their many hydraulically operated tube-feet, and have a mouth in the middle of the underside of their radially symmetrical body. Often the sea urchins found on the beach have lost their spines.
Read more about sea stars and sea urchins.
Sea Squirts (ascidians or tunicates) are sedentary animals that live attached to rocks. Most commonly found washed up is the orange-red Sea Tulip with its stalk and two openings. Often found also are the colonial sea squirts – squashy objects with many small openings.
Read more about sea squirts.
Fish or their bones are sometimes found as well as the leathery egg-cases of Port Jackson sharks and those of dogfish, which look like a purse with horns.
Read more about fish.
Sea Reptiles. Being air-breathers, marine reptiles must come to the surface to breathe. One species of sea snake occurs in our local waters and turtles are occasionally washed down the coast from their usual tropical habitat.
Read more about sea reptiles.