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Blue-green algae

Blue-green algae are found in aquatic habitats such as rivers, lakes and watercourses where conditions permit.

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Blue-green algae

Blue-green algae are a type of bacteria known as cyanobacteria. Despite being called algae they only have some things in common - they photosynthesise to produce oxygen and they need sunlight to grow. Cyanobacteria are a micro-organism generally blue-green in colour. Cyanobacteria occur in rivers, lakes and watercourses where conditions permit. Common algal species found in Gold Coast waters are Trichodesmium and Lyngbya majuscule.

Cyanobacteria bloom

Blue-green algae can exist in both salt and freshwater and are part of a healthy ecosystem. In normal conditions the cyanobacteria exist in low numbers in waterways.

Thick dense colonies called  ‘cyanobacteria bloom’ can grow quickly under certain conditions. Blooms can be ‘harmful algal blooms’ or ‘nuisance algal blooms’. A harmful algal bloom is one where the alga species produces toxins that pose a threat to humans, animals and the environment. Nuisance algal blooms are not known to produce toxins. See examples of the bloom's appearance in the image gallery below.

Causes

Cyanobacteria blooms can occur under the right conditions. These conditions include:

  • an increase in nutrient levels (for example, nitrogen and phosphorous)
  • high sunlight
  • warm water temperatures
  • stagnant and drought conditions.

Risks

Cyanobacteria generally live near the water surface. They accumulate in certain areas of waterways due to wind and currents, which can cause cyanobacteria to clump near the water's edge. Toxins can produce certain species especially when they are dying. In some situations cyanobacteria uses the sunlight, nutrients and dissolved oxygen. These blooms can have a detrimental impact upon aquatic ecosystems. Cyanobacteria blooms also discolour the water and create a smelly scum on the surface near the shoreline.

Reducing the risks of cyanobacteria

To reduce the risk, residents and visitors should refrain from:

  • activities that result in contact with the water (including swimming)
  • consuming seafood obtained from the lake (including shellfish, oysters, mussels, crabs and fish)
  • allowing pets to enter the water.

If you have any symptoms after contact with lake water or eating fish from the lake please see your doctor or call 13 HEALTH (13 43 25 84).

Prevention

You can help prevent blooms by limiting the amount of nutrients in the water. Detergents and fertilisers have a high concentration of nitrogen and phosphorus. Being mindful when using detergents and fertilisers can reduce the blooms. The proper disposal and use of fertilisers will limit nutrient levels in waterways. Washing your car on the lawn rather than the road or driveway can minimise the levels in local waterways.

Reducing sediment runoff and soil washing into the waterway can reduce cyanobacteria blooms. Responsible stormwater management in developing areas also helps to reduce levels of nutrients entering waterways.

The City monitors cyanobacteria levels and provides advice when elevated levels are identified.

Report Cyanobacteria

To report a cyanobacteria bloom online visit our Report a problem - Pollution page. Alternatively, please contact the City on 1300 GOLDCOAST (1300 465 326) or 07 5582 8211.

Click to enlarge

Cyanobacteria algal bloom
Cyanobacteria algal bloom
Cyanobacteria algal bloom

Trichodesmium

Trichodesmium are cyanobacteria (blue−green algae) that appear naturally in tropical and subtropical ocean waters and are commonly known as sea sawdust, whale food and sea scum.

Trichodesmium is a member of the phytoplankton family. It plays an important role in the aquatic food chain.

How does Trichodesmium form?

Normally, Trichodesmium are barely visible to the naked eye, but in water that has been calm for long periods it begins to float like sawdust. The algal cells can join up to each other in strings and clumps.

As the cells age, they become positively buoyant and rise to the surface. During calm conditions, northerly currents and warm water temperatures, these cells can aggregate into huge slicks that are sometimes so vast they are visible from space.

What does Trichodesmium look like?

Trichodesmium blooms are most common between August and December. You may have noticed a bloom washed up on a beach, in an estuary area or in the Broadwater. There may also be an unpleasant ‘fishy’ smell.

Prevailing wind direction and current conditions often cause large amounts of Trichodesmium to group together. Trichodesmium blooms can cause water to appear rust−coloured but traces of grey, green and purple streaks can also be visible.

In stagnant conditions, Trichodesmium blooms can release a clear toxin that changes the blooms’ colour from rust brown to green and also releases a pigment that colours the water pink.

See the image gallery below for examples of the bloom's appearance.

What should I do if come into contact with Trichodesmium?

The concentration of the toxin in a natural system, like the ocean, is generally not high enough to be harmful to human health.

Trichodesmium has the potential to cause irritation. It is recommended that contact with areas that are visibly affected is avoided. This includes avoiding swimming or wading in areas where Trichodesmium is visible in the water and avoiding direct contact with material washed up onto the beach.

If you come into contact with Trichodesmium, it is advisable to wash with soap and clean water as soon as possible.

How do I report Trichodesmium?

Report occurrences of Trichodesmium blooms online by visiting our Report a problem - Pollution page. Alternatively, please call the City on 1300 GOLDCOAST (1300 465 326) or 07 5582 8211.

Click to enlarge

Trichodesmium algal bloom
Trichodesmium algal bloom
Trichodesmium algal bloom

Lyngbya

Source: Nick Dos Santos

Lyngbya (Lyngbya majuscule) is commonly referred to as “mermaids hair” or “fireweed”. It is an unbranched filamentous cyanobacteria that is often found in tropical and subtropical coastal environments worldwide.

The species can grow 30 metres below the water surface whilst attached to rocks, sand or seagrass. Rough seas can disturb the bottom-growing lyngbya, creating large floating mats on the water surface. These floating mats drift with the currents, winds and tides, becoming stranded on beaches and foreshores.

Although lyngbya blooms may occur naturally, they can impact environmental and personal health.

What causes a lyngbya bloom?

Lyngbya blooms in recent years appear to be increasing in frequency and size within south-east Queensland. Climate change may influence the frequency or geographical distribution of blooms. It is found in sheltered estuaries and bays, commonly within seagrass communities. It grows either as mats, on seagrass leaves or detaching and rafting in the water column, or in unvegetated areas. Blooms can occur at any time of the year but are most common in south-east Queensland between the months of October and March. Blooms can rapidly occur under the right conditions. These conditions include:

  • an increase in nutrient levels (for example, nitrogen and phosphorus)
  • high sunlight
  • warm water temperatures.

Impacts and risks associated with lyngbya

Lyngbya contains chemicals that can cause skin, eye and respiratory irritation. For example, blooms were first reported in Moreton Bay by fishermen who experienced dermatitis and asthma-like symptoms after coming in contact with the cyanobacterium.

Fish tend to avoid areas affected by lyngbya. Such blooms can reduce available catch for the fishing industry and recreational fishermen.

Lyngbya are also known to smother seagrass, coral and other aquatic habitats.

How can I avoid these risks?

To avoid being affected by Lyngbya, residents and visitors should refrain from:

  • activities that result in contact with the water (including swimming and wading) in areas where lyngbya are growing or floating in the water
  • touching material washed onto the beach or water’s edge
  • consuming seafood obtained from the waterway (including shellfish, oysters, mussels, crabs and fish)
  • allowing pets to enter the water.

Please see your local doctor or call 13 Health (13 43 25 84) if you experience any of the above-mentioned symptoms after coming into contact with Lyngbya or eating fish / other marine species from the waterway.

What is the City doing?

The City monitors the cyanobacteria levels in accordance with National Guidelines and will provide advice should elevated levels be identified.

Responsible stormwater management in developing areas is an effective way to reduce levels of nutrients entering waterways.

How do I report Lyngbya?

Report occurrences of Lyngbya blooms online by visiting our Report a problem - Pollution page. Alternatively, please call the City on 1300 GOLDCOAST (1300 465 326) or 07 5582 8211.

References

Queensland Government 2019, Algae and algae blooms, accessed online at https://www.qld.gov.au/environment/coasts-waterways/marine-habitats/algae-blooms

Taylor, M.S., Stahl-Timmins, W., Redshaw, C. H. and Osborne, N.J. (2014), Toxic alkaloids in Lyngbya majuscula and related tropical marine cyanobacteria. Harmful Algae, Volume 31, Pages 1-8 accessed online at https://www.sciencedirect.com/science/article/pii/S156898831300125X

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