Algal blooms
There are different kinds of algae, and some can make people and animals sick. Symptoms can include:
- eye or skin irritation
- sore throat
- gastroenteritis.
Algal blooms happen when there’s too many algae growing in the water. This happens in fresh and marine waters and are a normal part of the seasons. They can change the smell, appearance and colour of the water. Algal blooms can last anywhere between days or even months.
There are many reasons that algal blooms occur in Canberra’s lakes. This makes it hard to manage and stop how often they appear.
Risks of algal blooms
Algae grows faster in warm water with lots of light and nutrients. When it grows too much, and they die they can use up too much the oxygen in the water that fish need to live. Fish and other organisms need oxygen in the water to live and thrive.
Cyanobacteria or ‘blue-green algae’ is one of the most common causes of potentially toxic blooms in freshwater systems. The toxins that they can produce are known to cause damage the tissues of fish or poison shellfish and people who eat them. Accidentally eating algae can cause liver damage and disease, nerve damage and even death.
Causes of algal blooms
To grow and bloom, algae need the right combination of factors, including:
- water above 25 degrees Celsius
- light
- still water that’s not mixed by winds or rain
- increased nutrients.
When water separates into layers based on temperature, the bottom layer is cold and doesn’t mix with the surface layer. The oxygen is consumed by bacteria in the sediments, because there is no oxygen nutrients can be released into the water from the sediments.
High levels of nitrogen and phosphorus also help algal to bloom. Some algae get nitrogen and phosphorous from water. But most blue-green algae can get nitrogen gas from the air. This is an advantage when algae are trying grow.
As our city grows, there is extra dirt and leaves in our water. This releases more nutrients into the water, which means there may be more algal blooms.
Algal blooms in our lakes
Lakes are great for having fun and helping to keep our water clean.
When it rains, water flows from the concrete stormwater drains and away from our homes and into our lakes. The lakes then trap the harmful materials like dirt and nutrients. This keeps it from going downstream into the Murrumbidgee River and Murray-Darling Basin.
Our lakes help to protect the river, especially when there’s been a lot of rainfall. Lakes will sometimes close after heavy rain, find out more about lake closure and alerts in the ACT.
Algal blooms and climate change
With climate change, the ACT has recently experienced some of the hottest years on record and lots of rain. We can expect summers to get even hotter and have more severe storms. Algal blooms can lead to lakes closing more often and for longer.
Strong summer storms make the water flow faster. This carries the dirt and nutrients from into our lakes and rivers, which helps algae to grow.
To help our climate in the ACT, we can:
- stop leaves, fertilisers, and soil getting into our waterways
- plant more local native plants near lakes and rivers
- build wetlands, ponds and rain gardens to clean water before it gets into lakes and rivers