Eurobodalla Estuarine Species

Estuaries


Eurobodalla Marine Species Eurobodalla Marine Species Eurobodalla Marine Species Eurobodalla Marine Species

SOME COMMON ANIMALS AND PLANTS OF EUROBODALLA’S
ESTUARIES

There are numerous coastal lakes, saltmarshes and tidal estuaries along the Eurobodalla coast – Eurobodalla means land of many waters. The coastal lakes are often closed to the sea. Like saltmarshes they can become excessively salty during droughts and almost freshwater in rainy times. Fewer species can survive these extreme conditions.

Tomaga River

Animals and plants of tidal estuaries also face difficulties. For example, the sandy or muddy bottom habitats can be moved by currents, floods bring fresh muddy water, and fine mud beneath mangroves lacks oxygen.

Mangroves

You can get a closer look at examples of tidal estuarine habitats at Cullendulla Nature Reserve, Batemans Bay; foreshore reserves near the mouths of Tomaga and Moruya Rivers; and Narooma boardwalk and foreshore reserves.

SOME COMMON PLANTS OF OUR TIDAL ESTUARIES

ALGAE Some of the common algae of nearby coastal waters also occur in the lower reaches of tidal estuaries.


Neptune’s Necklace *Hormosira banksii* A form of this alga that grows near mangroves does not attach itself. It can tolerate wide changes in salinity and exposure at low tide.	Sargassum Sargassum species Several species are common on coastal rocky reefs. Some also grow attached to hard surfaces near the mouths of open estuaries. Their floats are small round balls.

SEAGRASSES are flowering plants with leaves and roots rising from horizontal buried stems (rhizomes). They help hold the bottom sediment in place. The leaves support growths of epiphytic algae and micro organisms and are very important habitats for juvenile fish and invertebrates.


Eel Grass Zostera species Eel Grass leaves are up to 5mm wide. It occurs in shallow waters in most estuaries and lakes and in some sheltered bays. It is able to withstand some exposure at low tide.	Strap Weed *Posidonia australis* Strap Weed has a broader, longer leaf than Zostera and prefers deeper, clearer water. It is widespread in Wagonga Inlet, parts of the Clyde estuary and is also found on the northern side of Broulee Island.


Paddlegrass Halophila species Paddlegrass has a small oval leaf. It is often found near Zostera.

MANGROVES occur in most of Eurobodalla’s estuaries, often in waterlogged mud. Their seeds are dispersed by the tides and their decaying leaves form the basis of most estuarine food webs.

Grey Mangrove
Avicennia marina
This is the main mangrove in Eurobodalla’s estuaries. Its aerial roots take oxygen below the surface.

Grey Mangrove Fruit

The round seed pods begin growing before dropping from the tree.

River Mangrove
Aegiceras corniculatum
The River Mangrove is not as common as the Grey Mangrove, lacks aerial roots, and is usually found further upstream.

River Mangrove Flower

Its leaves are brighter green, rounder and shinier than the Grey Mangrove’s and its fruits are crescent shaped.

SALT MARSHES

SALTMARSHES are covered by very high tides and the plants are adapted to resist high salt levels and drying out. The surface of the mud is stabilized by a film of algae and bacteria – food for many small invertebrates. Conditions are harsh and saltmarshes are slow to recover from damage such as trampling.


Beaded Glasswort or Samphire Sarcocornia quinqueflora Samphire is a common saltmarsh plant. It has no leaves but the stems have swollen segments that hold water. In colder months Samphire and other succulent saltmarsh plants are often coloured red or orange.	Austral seablite *Sueda australis* A small shrub with succulent, almost-cylindrical leaves found in patches in saltmarshes and along the edges of estuaries.	Swamp weed *Selliera radicans* A creeping plant with fleshy oval leaves and small white fan flowers in the warmer months.


Creeping Brookweed Samolus repens A low-growing plant often found in moist salty locations. Its small white to pale pink flowers have 5 petals.	Sea lavender *Limonium australe* The long dark leaves grow in rosettes and in summer the plant has clusters of small yellow flowers held higher on branched stems.	Sea Rush Juncus species Reeds and rushes often grow in the water if it is not too salty.


Common Reed Phragmites australis Found in less salty conditions. Its leaves often turn yellow in winter.

SOME COMMON ANIMALS OF SALTMARSHES AND MANGROVES

Air breathing snails of the saltmarshes graze on microscopic algae. They are hermaphrodites, alternating between male and female with the changes in the phases of the moon. Egg laying is timed for spring tides to carry eggs to the estuary and settling larvae back.


*Salinator sp* < 18mm	*Ophiocardelus* snails < 13mm Can survive 80% dehydration.

“Shipworms” These are molluscs that use their reduced shells to grind a tube in decaying wood. They digest the wood and grow to fill the tube, lining it with a thin hard white lining but remain connected to the surface to obtain oxygen and to release their larvae.


Teredo species Here shown out of its shell	*Teredo* species The hard white tube lining.


Gold-mouth Conniwink Bembicium auratum <20mm This Conniwink is a grazing snail that lays eggs mainly from Aug to Jan in small "jelly beans".	Zebra Top Shell *Austrocochlea porcata* <25mm Found near the mouths of open estuaries, it is also common on rock platforms. It scrapes microscopic algae from hard surfaces.	Black Nerite *Nerita atramentosa* <30mm Another grazer that is also common on rock platforms. It lays eggs in white capsules.


Small limpet *Patelloida mimula* Usually found on oyster shells where it grazes on microscopic algae.	Sydney Rock Oyster *Saccostrea glomerata* < 100mm Is cultivated locally. Although valued for its better taste, it grows more slowly than the Pacific Oyster.


Pacific Oyster *Crassostrea gigas* < 250mm Has a flakier shell. Attempts are being made to eradicate it from local estuaries.	Estuary slug *Onchidella patelloides* An air-breathing mollusc without a shell that lives under rocks and wood, especially near oyster beds. It grazes on microscopic algae.	Pill Bugs *Sphaeroma* Are crustaceans related to garden slaters. They bore into wood. Eggs are held under the female and brooded until hatched. Here shown curled up (left), and boring into wood (right)

Crabs are the most noticeable invertebrates in saltmarshes and mangroves. Most spend part of their lives as larvae in the lower reaches of their estuary.


Haswells Shore Crab *Helograpsus haswellianus* < 30mm across carapace Lives highest on the shore in burrows or under rocks or wood.	Red-nippered marsh Crab *Parasesarma erythrodactyla* < 25mm across carapace Is a predator and scavenger that lives under rocks or wood nearer the water. It will use burrows if they are available. Females and juveniles are less colourful.	Semaphore crab *Heloecius cordiformis* < 25mm across carapace Eats decaying matter. It burrows in saltmarsh and mangrove zones and seals its hole with mud at high tide. Males signal to attract females to the burrow to mate. Adult males have larger mauve claws.

Shore Crabs *Cyclograpsus* species < 40mm across carapace Are omnivores that live under wood or rocks. This one is a male.	Female Shore Crab Like most crabs, females hold the eggs under their abdomen until they are ready to be released.	Mud Crab *Scylla serrata* < 300mm across carapace Adults live in burrows near mangroves where they mate and moult. The egg-bearing females go to sea to release them.


Pistol Shrimp *Alpheus* species Is a predator on small animals. It lives hidden near the low tide mark but is heard more often than seen. It makes loud clicks by snapping the finger of its large claw into a socket.

MUDFLATS AND SAND FLATS


Sydney Mud Whelk *Pyrazus ebeninus* < 110mm Both mud whelks digest edible material from the mud.	Little Mud Whelk *Batillaria (= Velacumantus) australis* < 45mm Not quite as common as the Sydney Mud Whelk. It carries the parasite which causes swimmers itch.	Estuarine Bubble-shell *Bulla quoyii* The live animal is rarely seen as it hides in the sediment during the day and comes out at night to feed on algae. Fleshy lobes extend beyond the animal’s shell and help it move through the mud.

Moon or Sand Snail *Polinices* species < 40mm Is a predator on bivalves, drilling a hole in the shell by softening it with acid, then rasping with its tongue-like radula. It lays its eggs in a large kidney shaped jelly	Small bivalves There are many species of bivalve that live hidden in the sediment of our estuaries. The photo shows a sample of some washed up in Batemans Bay. Those with a round hole in the shell have been eaten by Moon Snails.	Hairy Mussel *Trichomya hirsute*< 60mm Often found attached in dense clumps to rocks and other hard surfaces.


Sydney Cockle *Anadara trapezia* < 75mm Just one of the numerous bivalves that bury in the sediment. Most use siphons to filter out food and obtain oxygen from the water.	Mud Oyster *Ostrea angassi* < 180mm Juveniles of this large flat oyster attach to stones or shells but adult live free on soft sediment. It is the most common shell found in middens around Wagonga Inlet.	Soldier Crabs *Myctris* species <15mm across the carapace Sift edible particles from the sediment. They can walk forward and spiral into the sand if threatened.

Blue Swimmer Crab *Portunus pelagicus* <210mm across carapace Like mud crabs, after mating the females travel to sea to release their eggs.	School Prawns eg Metapenaeus species Young school prawns grow rapidly in seagrass beds. Adults go to sea to spawn and the larval stages develop there before re-entering the estuaries as minute prawns.	Yabby *Callianassa sp* Lives in a branching burrow down to 30cm or more. It makes a current through the burrow with its tail and traps microscopic food with bristles. Males have a large claw.


Polychaete worms eg Bait Worms There are many species and together they are the most numerous bottom dwelling animals. They vary in size and feeding methods. Some build tubes. All release eggs or sperm into the water and have planktonic larval stages.

Prepared by Jenny Edwards.

All photos by Jenny unless otherwise credited.

Index to this page

TIDAL PLANTS
SALT MARSH PLANTS
SALT MARSH ANIMALS
MUDFLAT ANIMALS

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