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A Volunteer Community Awareness
Program for Louisa Creek


Prior to settlement Louisa Creek would have flowed through a variety of habitats such as riparian forest, open and melaleuca woodland to coastal wetland communities. Today a significant portion of the catchment has been urbanised with land use now ranging from residential through to industrial and special purposes. The urbanisation has resulted in the vegetation communities becoming fragmented and degraded through the growth of weed species. However, despite these pressures the creek retains very high environmental values including:
  • Remnant vegetation habitat for diversity of birdlife, small mammals and reptiles.
  • High fish habitat values due to its connection with Town Common, Bohle River and Great Barrier Reef Marine Park.
  • Buffer between industry and housing

The two most important vegetation communities for the health of the creek are its riparian and instream communities. Riparian vegetation is the vegetation that grows along the creek banks such as;

    • Melaleuca leucadendron (Weeping Paperbark)
    • Millettia pinnata (Indian Beech)
    • Eucalyptus tereticornis (Blue Gum)
    • Corymbia tessellaris (Moreton Bay Ash)
    • Glochidion disparipes (Cheese Tree)

Riparian vegetation has some very important functions in the health of Louisa Creek including:

  • Bank Stabilisation and Water Quality Protection: The roots of riparian trees and shrubs help hold stream banks in place, preventing erosion. Furthermore, riparian vegetation also traps sediment and pollutants improving water quality.

  • Fish Habitat: Both large and small snags create fish habitat by providing cover and forming pools and riffles in the stream. Riffles are shallow gravelly sections of the stream where water runs faster. Many of the aquatic insects live in these riffles.

  • Wildlife Habitat: Riparian vegetation provides food, nesting and hiding places for many animals. These areas also provide valuable wildlife corridors particularly in urban areas. These corridors allow animals to move from one area of woodland to another.

  • Thermal Cover: Riparian vegetation shields streams and rivers from summer temperature extremes that may be very stressful, or even fatal, to fish and other aquatic life. The cover of leaves and branches brings welcome shade, ensuring that the stream temperature remains cool in summer and moderate in winter. Cooler, shaded streams have less algae and are able to hold more dissolved oxygen, which fish need to breathe.


Instream aquatic plants are also a very important element of a healthy waterway. Instream plants found in Louisa Creek include:
  • Hydrilla verticillate (Hydrilla, Water Thyme)
  • Nymphaea gigantea (Giant Waterlily)
  • Persicaria attenuata (Water Pepper)
  • Potamogeton javanicus (Pondweed)
Hydrilla verticillate found in Louisa Creek

Native instream vegetation is very important to the health of the creek ecosystem. Plants, being producers, form the basis for most food webs that are functional in the creek. Instream aquatic plants play many important roles in the creek, including:

  • Oxygen production – through the process of photosynthesis, aquatic plants consume CO2 and produce O2 making this available in the water columns for aquatic animals to breath.
  • Providing food for foragers.
  • Providing habitat for aquatic animals.

Healthy streams support a variety of instream plants and animals.


Introduced Plants:

Many of our streams in the coastal dry tropics are impacted by the introduction of invasive environmental weeds. These weeds have been introduced through many pathways including: use as a cattle fodder, ornamental garden plants and by accident. The weeds found along Louisa Creek can be put into two groups, riparian or terrestrial weeds and aquatic or floating macrophytes.

The terrestrial weeds include plants such as: Rubber Vine, Siratro vine, Chinee Apple, Leucaena and Guinea Grass.

The main impact of the terrestrial weeds upon the riparian zone is the loss of biodiversity they cause. This is caused in several different ways including,

  • Competition: most weed species grow very rapidly, produce lots of seed and several species can smother native vegetation. Weed species are able to out compete native plants for available resources and space.

  • Changed environmental conditions: some species change the conditions in the riparian zone so native plants struggle to survive. A good example is fire, guinea grass produces a fire that is much hotter and with a much higher flame height. This type of fire kills native trees and allows more weeds to become established.
Guinea grass can have major impacts on native vegetation communities


The proliferation of aquatic weeds, particularly floating macrophytes also has a negative effect on creek health. The two most detrimental weeds present are: Para Grass and Salvinia. These weeds affect the creek in many ways including.
  • Blocking sunlight from entering the water column, therefore preventing primary production in native aquatic plants reducing dissolved oxygen.
  • Smothering native vegetation.
  • Altering flow conditions in the creek by, physical blockage, trapping sediment.
  • Reducing habitat for native aquatic animals.

These two weeds are very difficult to control, the best way being the establishment of closed canopy riparian vegetation.

Para grass can significantly affect in-stream values

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