Algae and Pest Aquatic Plants TA12 Scope Aquatic (Freshwater) - - PowerPoint PPT Presentation

Algae and Pest Aquatic Plants

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Scope

• Aquatic (Freshwater) Systems
• The plants and plant like organisms which live

there

• What stresses these systems?
• The outcomes of these stresses
• What we can do?

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Aquatic systems

• Aquatic systems (lakes, wetlands, and rivers)

generally exist in a ‘balanced’ state

– Tomato Lake – Freshwater Lake – The Swan River

• The aquatic organisms which live there are

sensitive to changes in their physical environment

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Aquatic systems

• Any changes in their physical environment results

in a direct change to specie presence/diversity and abundance

– e.g. Most aquatic organisms have a limited range in salt and temperature tolerance – a major increase or decrease results in their death – Increased sunlight on aquatic plants or “plant like”

• rganisms can enable favourable environments

resulting in population growth

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Aquatic systems

• Aquatic organisms in these systems?

– Plants and algae (primary producers) – Macro-invertebrates – Fish – Turtles – Birdlife

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Algae

• Algae and Cyanobacteria (blue-green algae) exist

in the environment at all times and are important life forms

– “feed” off nutrients in the water – Provide food and habitat for macro-invertebrates and fish – Can grow exponentially when the environment permits – “Good” and “bad” species

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Aquatic Plants

• Native aquatic plants are critical components of

freshwater systems

– Provide food and habitat for macro-invertebrates and fish – Reduce nutrient levels in the system – less nutrients can result in reduced algal blooms – Exist as “true plants” or floating plants – Can grow exponentially when the environment permits – Can be opportunistic – grow during a particular time of year

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Aquatic Plants

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Stresses

• Excess nutrients results in eutrophication

– a state of the environment where the aquatic system is “saturated” with nutrients – results in an exponential growth of primary producers (plants and algae blooms)

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Stresses

• Algal and plant blooms can

– Outcompete other organisms – smother the environment (risk to aquaculture) – Cause bad odours – Result in fish kills

• Directly - toxic
• Indirectly - deplete oxygen

– Toxic algal blooms can result in the closure of recreational waterways due to public health concerns (SRT, DoH)

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Can we manage it?

• Various methods

– Direct and indirect chemical or biological controls

• Direct: algaecides (i.e. Alum dosing) – non-selective and

kill other freshwater organisms

– Not commonly used in “natural” environments

• Indirect: Phoslock or soilzyme which help reduce

nutrient availability

– Soilzyme currently applied to City lakes -Tomato Lake, Freshwater Lake, Centenary Park Lake

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Can we manage it?

• Various methods

– Physical management

• Manual removal: only possible with filamentous plants and

algae

– Expensive, labour intensive and can disturb “stored” nutrients in sediment

• Aeration/ oxygenation: using aerators, mix the water column

and prevent stratification

– Increases the amount of oxygen available to all organisms = increase natural uptake of nutrients – Reduces risk of bad odours and fish kills

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Best Practice

• Reduce nutrient loads going to aquatic systems

– Community awareness (i.e. washing cars on the lawn, not putting grey water to the drain) – Monitor land uses (i.e. Belmont Environmental Assessment Program, Stormwater monitoring) – Vegetated buffers between irrigated and fertilised areas surrounding water bodies – fertiliser wise low/no Phosphorus fertilisers or fertiliser wise gardens – Encourage native aquatic/ wetland flora (keep the balance)

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Thank you. Q&A?

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