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Algal blooms

An algal bloom is the thick greenish-brown layer of algae that sometimes forms on top of ponds and still water bodies.

What causes an algal bloom?

Algae occur naturally and are present in healthy aquatic ecosystems; however when nutrients like phosphorus and nitrogen are at excessive levels, and other environmental conditions are favourable, algae can multiply at a tremendous rate causing a bloom. This process is called eutrophication.  

While algal blooms tend to grow more quickly in warmer months when there is more light and temperatures are higher, they can occur at any time, and sometimes they even occur naturally.  

So what’s the big deal?  

When it rains, the stormwater runoff will collect anything that is in its path, including sediments from construction and development works, fertilisers and pesticides from agriculture and household gardens, decomposing plant matter and soil, animal waste, detergents, and just about any organic source and delivers them to our waterways.  

All of this organic material then has the potential to cause an algal bloom. These algal blooms can form into a thick layer that limit sunlight, making it hard for aquatic plants to photosynthesise, causing them to die. As the plants die they soak up a huge amount of oxygen which then chokes out the remaining wildlife.  

What can I do?

You can help in a big way, just by doing small things around your home:  

  • keep your use of fertilisers and detergents to a minimum
  • clean up after your pets
  • wash your car on the lawn
  • capture garden and organic waste, like soil and grass clippings, before they reach the drains
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