page_title: Canning River
section_title: Algae bloom
hierarchical_section_title: Canning River / Algae bloom
caption_attribution_description: Azolla on the Canning River, Western Australia
context_page_description: The Canning River is a major tributary of the Swan River in south western Western Australia.
context_section_description: Algal blooms occur naturally in the Canning River system, they are caused by a buildup of nutrients in the river. Human activities including farming, residential gardens and parklands are the major causes of increases in levels, the blooms are potentially toxic to both mammal and marine life. The Swan River Trust monitors the levels of nutrients and growth of the algae issuing warnings and closing sections of the river to all activities. The Trust also operates cleanup programs to reduce the amount of nutrients reaching the river, as well phosphorus removal and oxygenation in areas were blooms have been identified.
  The Trust is encouraged by the appearance of Azolla carpets on sections of the Canning River as this fern is known to reduce the amount of sunlight available to the algae as well as absorbing large amounts of phosphorus and other nutrients from the water. However, it is possible that Azolla carpets can cause deoxygenation and emit a strong sulfur smell.
caption: Same location covered in a carpet of Azolla March 2007.
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