Author Archives: Geraldine



Engaewa (3) (600x402)

Engaewa mounds at the edge of a creek.

Engaewa (2) (640x443)

Engaewa are small burrowing crayfish that occur in the south west corner of Western Australia. There are five species, each with a restricted distribution and with one species critically endangered.

River power 1

Pallinup River at the Chillinup Road crossing

The concrete slab shown in this image, weighing ten to fifteen tonnes was stripped from a road crossing during a flood in the Pallinup River. The replacement crossing can be seen in the background. It is common for the power of flowing water to be underestimated when weighing the cost of construction against the risk of damage.

Macroinvertebrates of south Western Australia’s salt rivers 6

Hydrophilidae Berosus discolor

There are several species of water scavenger beetles that are able to tolerate extremes of salinity. The larvae obtain their oxygen through abdominal gills and crawl on the stream bottom feeding on small midge larvae and crustaceans. The adults have heads that bend downward (deflexed) and club shaped antennae tucked under their eyes that help to break the surface film of the water when replenishing their air supply. The hairs on their hind legs assist the beetles to swim. The adults eat plants and organic debris.

Macroinvertebrates of south Western Australia’s salt rivers 5

Aedes (Ochlerotatus) camptorhynchus is a mosquito species that breeds in the brackish and saline water of estuaries, inland rivers and wetlands. The larvae have been collected from water over twice as salty as sea water (90 ppt). The pupae are short lived, hatching quickly into adults. The adults can travel quite long distances and are found throughout the year, however they are most common from March to December. They are capable of transmitting the Ross River virus.

Macroinvertebrates of south Western Australia’s salt rivers 4

The caterpillar from the moth Hygraula nitens lives and feeds on the aquatic plant, Ruppia sp. and has been found in saline water up to 50 ppt. It belongs to the family Crambidae which are a poorly known group of moths whose larvae live underwater. They construct a cylindrical case of plant material that can reach two centimetres in length. The adults are small triangular moths with cream, grey and brown markings. The grid squares are 1mm2.

Macroinvertebrates of south Western Australia’s salt rivers 3

Cyprididae Mytilocypris mytiloides

The SW is home to a high diversity of seed shrimps (Ostracoda) with over 200 species known. Sixty-five known species live in naturally saline inland waters, however many of them are not found in systems impacted by rising salty groundwater (secondary salinisation). Some species are only found in one or two wetlands and there are still many undescribed species. This makes it difficult to develop protection plans. The eggs of seed shrimps can survive in dried sediments for several years. This species occurs in brackish to saline water and is common in swards of the aquatic flowering plant Ruppia sp. The grid squares are 1mm2.


Macroinvertebrates of south Western Australia’s salt rivers 2

The larval caddisfly, Symphitoneuria wheeleri  shown here is a halophile, i.e. it lives only in saline water. It utilises both sand grains and/or plant material to make its case, depending on what is readily available. The larvae feed on both plant material and small invertebrates and are the longest living stage of its life cycle. The grid squares are 1mm2. The second photo shows the head of a larval Symphitoneuria wheeleri with the head of a midge larvae protruding from its mouth. The adults superficially look like moths, are nocturnal and short lived.

Macroinvertebrates of south Western Australia’s salt rivers 1

Dytiscidae Necterosoma penicillatus

Necterosoma penicillatus is a predatory diving beetle endemic to southern Australia. The adults are able to tolerate extremes of salinity and have been collected in salinities of 130 ppt (over 3 times saltier than the sea), however the larvae require lower salinities to survive. The larvae have long swimming hairs on their legs and feed on their prey by piercing then pumping into them digestive juices with their long mandibles. They then suck up the liquefied food. The adults have long fringes of hair on their hind legs which act as paddles. They feed on their prey by pulling them apart with their strong fore legs and mandibles. 


The saltwater paperbark (Melaleuca cuticularis) is a common feature along the fringes of south coast estuaries. Here the interplay of light and water produces pleasing reflections  in the Wellstead Estuary at Bremer Bay.

Estuarine dynamics

The foreshores of estuaries are ever changing as water levels control the dynamic processes of erosion, sedimentation and colonisation by vegetation. Bank erosion, (Stokes Inlet, September 2009) in one location, due to high water levels and strong wave action, has built a nearby sand spit. Young Saltwater Paperbark trees (Melaleuca cuticularis) have successfully colonised the new ‘dune’ edge while old dead paperbark trees can be seen in the developing ‘inter-dune wetland’.