Algae and weeds
Managing algal blooms and aquatic weeds is important for improving the health of our waterways. Algal blooms and invasive weed growth arise from a decline in water quality and ecosystem health.
In normal conditions algae exists in low numbers in the waterways at no detriment to the environment or to human health. However under favourable conditions native plant species can be out competed and weed and algal colonies can overgrow natural habitats. In large numbers this harms waterways attacking native aquatic plants and animals.
Blue-green algae are tiny micro-organisms that belong to the ‘cyanobacteria’ family. The algae are found in habitats such as rivers, lakes and any watercourses where conditions are favourable. They are an important part of a healthy ecosystem. Unlike the name suggests they are not algae, but photosynthetic bacteria. Although quite rare, some species have the potential to produce toxins in low quantities.
To report an algae problem in our waterways, contact the City on 1300 GOLDCOAST (1300 465 326) or 07 5582 8211.
Aquatic plants are often mistaken for weeds. They form the foundation of a healthy flourishing lake by:
- producing oxygen through photosynthesis
- absorbing nutrients that would otherwise fuel toxic algal blooms
- providing food and shelter for predators of algae and mosquito larvae
- providing invaluable habitat for native birds, fish and other wildlife
- creating a buffer around the lake edge that can help limit erosion.
In essence, aquatic plants are a good thing.
Without plants, the condition of our lakes can rapidly deteriorate to the point where they are uninhabitable for animals, and may present a health risk to humans. To keep our lakes healthy, lakeside residents are encouraged to maintain aquatic plants.
Water quality, environmental values, and navigational requirements are considered when determining whether or not to physically remove or trim aquatic plants.
Learn about aquatic vegetation harvesting.
Invasive weeds have the potential to destroy native habitats by outcompeting aquatic ecosystems, restricting water flow, depleting oxygen in water bodies, and degrading the waterways to the point that fish kills may result.
Aquatic weeds can spread easily, for example; weeds can be carried downstream or spread by birds and humans in the form of seeds or as a broken or torn weed. Parts of weeds that have broken off often regrow in a new location. The majority of aquatic weeds in the Gold Coast are aquarium or ornamental plants dumped into the waterway with unwanted fish. The following is a list of declared aquatic weed species commonly found in the Gold Coast:
Residents can help to stop the spread of these aquatic weeds by disposing of unwanted aquatic plants thoughtfully, keeping weeds under control and working towards getting rid of them completely. For more information about these weeds, click on the following link or contact the City on 1300 130 854 and ask to talk to the Pest Management Unit.
Marine algal blooms occur when favourable conditions allow them to rapidly grow and dominate the aquatic ecosystem. Environmental conditions influencing algae growth include:
- elevated nutrient levels
- availability of trace elements such as iron
- exposure to increased light levels
- reduced water flow and circulation
- warmer water temperatures
- season – warmer months and stable weather conditions.
Algal 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, whereas nuisance algal blooms are not known to produce toxins. Common algal bloom species in Queensland include Lyngbya majuscula, Hinksia sordida and Trichodesmium.
To learn more about marine algal blooms visit the Queensland Government website or the Healthy Land & Water website.
Managing algae and the environment
We need to be particularly aware of how our activities can impact the health of our water environments. Activities such as sedimentation, development, boat wash, dredging, weeds, high nutrient loads, loss of riparian habitat, pest fauna, and livestock grazing by streams all have the potential to cause a decline in water quality and ecosystem health and produce favourable conditions for algae and aquatic weed growth.
City carries out maintenance on the city’s lakes in respect of undesirable aquatic plants to ensure the safety of residents and users. Aquatic habitats such as the Robina Lakes are being preserved and restored under the City management plan. The plan introduces a range of new initiatives aiming to alleviate recurring problems such as occasional blue-green algae blooms and controlling water weed growth for ecological health and aesthetic appeal.
You can help maintain water quality in water environments with simple steps, such as ensuring pollutants like litter, animal waste, fertilisers, detergents and grass clippings don’t enter the stormwater and waterways. Keep boat wash to a minimum to reduce bank erosion and sediment disturbance and adopt best land management practices to minimise run-off into our waterways. Get involved with community catchment groups to help preserve and improve the health of our catchments.
To find out more about what you can do to help improve the health of our catchments and waterways visit our Environmental volunteering page.
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