Kelp Forests poster
Kelp are a special group of large brown algae that attach themselves to solid structures to form forests. They extend their leaf-like fronds into the waters above them reaching towards the sunlight. These larger algae in turn create a habitat for smaller algae and a wealth of animals that can either live attached to the rocks beneath the kelp, on the kelp itself, or in the sheltered waters between the kelp.
Strong structures at the base of kelp (holdfasts) hold the kelp firmly to rocks, so that even when currents are at their strongest, kelp is in no danger of being swept away. On Victoria's coast kelp forests grow on most rocky reefs in waters to a depth of around 30 metres, although most are found in shallower waters.
In the same way that trees provide shelter and food for many different species, kelp are the true forests of the sea. Kelp forests have a dense canopy of blades, blocking out light which results in shading of the rock surface, providing an ideal environment for an understorey of encrusting algae and non-moving animals.
Black lipped Abalone
This large grazing snail is relatively common on rocky reefs and under kelp forests. Abalone have a large muscular foot and membranous black lip and feed largely on drift algae as adults. Highly sought after by commercial and recreational fishers there are restrictions on collecting to ensure survival of this valuable species.
Purple spined sea urchin
Living under reefs during the day, these large nocturnal urchins feed on large algae on rocky reefs. Under their bodies five sharp teeth, called 'Aristotle's lantern', can efficiently remove seaweeds from rocks. In areas where predators such as large fish are removed, urchin numbers can increase, leading to a sudden loss of large areas of kelp forest.
Common in kelp forests this colourful carnivorous fish has an interesting life cycle. All wrasse are born as females and join a school dominated by a single male. When the male dies a large female will 'change sex' and colour to become the dominant male. Male wrasse are brightly coloured compared with females.
Southern Rock lobster, crayfish
Living for many years and growing to 700mm, these shy scavengers live on the rocky kelp forest floor. Rock lobsters have a complex lifecycle where larvae spend over a year floating as a part of the zooplankton before settling to the bottom. Restrictions on collection and protection of juveniles is important to maintain the future of the rock lobster industry.
The largest species in the world, Giant Cuttles are cunning predators with an amazing ability to change colour. Cuttles feed by stalking prey then capturing them using two spear-like feeding tentacles. Cuttles are largely nocturnal but may be seen cruising the kelp forest during the day seeking prey or mates, often displaying a curious interest in any visitors to their territory.
Decorator crab or Seaweed crab (Naxia spp.)
Masters of camouflage, these crabs are often difficult to observe amongst the algae. Using their claws, they cut pieces of algae or small animals from their surroundings and stick them between hooked hairs and spines on their back using saliva as a type of glue. These crabs are scavengers.
Giant kelp or String kelp
Forming a dense forest, the long narrow fronds of this kelp grow to over 10m in length. Small air floats help to hold it towards the light. A tangle of stems (stipes) connect the strap like blades to the holdfast secured to the rocky bottom. Many animals shelter amongst this forest of kelp.
This group of red algae consists of both branched and encrusting species. In the low light under the kelp forest these crusty pink algae grow over rocks, playing a vital role in producing food for grazing animals like juvenile abalone. Calcium carbonate found in their structure assists in the building of rocky reefs.
Habitat Close Up
Syngnathids - seahorses, sea dragons and pipe fishes
One of the most spectacular family of fish is the group that includes seahorses and their close relatives the sea dragons and pipefish. Within and around the kelp forests these slow moving and graceful fish go about their daily lives relatively unnoticed.
All of these fish possess long tubular mouths through which they 'suck' in unsuspecting small crustaceans like mysid shrimp and amphipods. The name of this group of fish is the Family Syngnathidae, a name that refers to the jaws of these fish that are fused together.
Seahorses hold their bodies upright and move by using an undulating dorsal fin plus two small pectoral fins on the side of the head to steer. Seahorses use their long tails to cling to pieces of kelp. Male seahorses have a brood pouch in which females lay their eggs. It is within this pouch that fertilisation occurs. After a month or so the young are born alive as miniature versions of their parents, already active in seeking out food.
The world's two species of sea dragons are found only in southern Australia and both species, the Weedy seadragon and the even more ornate Leafy seadragon, have been recorded on the Victorian coast. Male sea dragons carry the developing young under their long tails. While relatively common in some areas sea dragons often go unnoticed because of their shape and drifting habits.
Pipe fish are a third group within the family and resemble pipe cleaners after which they have been named. These fish are rarely observed despite being numerous in kelp forests and seagrass habitats, hiding their slender bodies amongst the seaweeds. Like other members of this group male pipefish play the major role in reproduction. Patience and careful observation while snorkelling or diving in kelp forests will often reward divers with a chance to see these beautiful fish.
For more information or to visit some of these magnificent marine habitats, please contact the:
Marine and Freshwater Discovery Centre, Queenscliff
Ph: 03 5258 3344