Gwendoline
Bell
NPA member and volunteer at Head
Office
|
Life on the seashore
Gwendoline
Bell |
|
Gwen was inspired to write this after participating |
"Australia’s rocky coastline has a variety of ancient life forms," Professor Underwood said. "These intertidal creatures, including rare fossil species, have survived on our shores till now, and we must cherish and conserve this natural heritage."
We have an enormously diverse coastline. However, at least 80% of Australia's population lives within 30 km of the coast, which means huge pressures are being put on coastal wildlife by development and recreation. Our present perception of the ocean as an unlimited resource works against our needs for marine stewardship.
Marine life still abounds on Sydney’s rocky shores, even within the heavily used Botany Bay National Park. Some of the creatures that live there include:
Cunjevoi processes stolonifera is an ancient life form, 80–150 mm long. It has a tough leather casing and attaches itself to the seaward side of a rock platform. It feeds by pumping large amounts of water through its body where a large sieve collects food from the water.
Algae are very simple in structure and many types consist of only one cell.
Seaweeds are multi-cellular, attaching themselves to rocks using a "holdfast"; if removed from rocks they cannot reattach. They derive their nutrients directly from seawater and use sunlight for photosynthesis.
Sea anemones are "sit and wait" predators. They are tubular, jelly-like animals with a mouth at the top which is surrounded by tentacles covered in stinging cells with tiny sticky threads inside. Prey is caught by the threads, paralysed by the stinging cells, then drawn into its mouth where it is digested.
Sea hare, or Aplysia, regularly visits our shores during spring and early summer. The clue to its name is provided by four tentacles on the head which have folds resembling a rabbit’s ear. It is a member of the mollusc family and lays large quantities of yellow egg strings. Often found in rock pools, it feeds on sea lettuce or Ulva.
Chitons are ancient molluscs with eight shell plates and a broad foot with which they cling onto the surface of the rocks. Chitons are algal feeders, on both microscopic and larger plants.
Octopus are highly intelligent predatory molluscs. The animal can propel itself quickly backwards with a water jet - it expands the muscular sac surrounding the body to suck in water and then squirts it out through the tubular siphon above the head. Octopi have eight sucker-bearing arms and feed on various crustaceans and molluscs.
Sponges are classified as the simplest group of multi-cellular animals. They are made up of a number of different types of cells, with the structure being held together by particles of lime or silica.
Sea urchins are usually roughly spherical in shape and have close- fitting plates covered with a delicate skin. The plates bear moveable spines. The animal walks aided by retractable tube feet. The suckers on the ends of the feet also help the animal to turn itself over, and hold onto the rocks.
Abalone shells have an ear-like appearance. At night they move about, rasping algae off the rocks with a powerful radula (tongue). Water is drawn in under the front of the shell, passed over the gills and then pumped out of holes on the edge of the shell.
Black nerites are some of the most numerous and easily identified shells. These snails, a glistening black when wet, can be found in crevices, rock pools or under rocks during low tide.
Galeolaria are filter-feeding worms that live in densely packed calcareous tubes. The worms stay permanently in the tubes, living on the nutrient particles from the water around them. Their black feeding tentacles pop out when covered with water. They are commonly incorrectly called "Sydney coral".
Sea stars come in many shapes and sizes and are masters of disguise, blending superbly into their surroundings. Some sea stars graze on seaweed, though they can be opportunistic feeders, eating decaying organisms. Generally starfish protrude their stomachs outside their mouths, envelope their food and begin to digest their food outside their bodies.
Beach worms spend all of their time under the sand, with only the head protruding occasionally to forage. They are carnivorous, using strong horny jaws to catch their prey. The giant beach worms (up to 2.5 m long) are relatively common, but are seldom seen as they live completely hidden in the sand where the surf breaks.
Reference:
Project
Aware (~1997) Sydney's
Rocky Shores. Sydney
Coastal Councils, Sydney Northern Beaches Total Catchment Committee, Pittwater
Municipal Council.
* Gwendoline Bell is a long-time NPA member and volunteer at Head Office.