Long Term Options Report Released to the Public

The “Study of Management Options to Mitigate Algal Blooms” in Lake Hugh Muntz has been made available to the public.

The report from the Griffith Uni Experts released to GCCC in August last year can be viewed on GCCC website on the Lake Hugh Muntz page through the link below.

http://www.goldcoast.qld.gov.au/documents/bf/study-of-management-options-for-lake-hugh-muntz.pdf

In Summary, the short term solution is to manage the blooms through treatments such as Phoslock and hydrogen peroxide. Unfortunately GCCC do not currently have equipment to treat with hydrogen peroxide. Computer modelling has indicated that the installation of Aerators would give the best result in reducing algal blooms.

Some Statements Taken from the Report  

Our report does not provide any additional information on catchment management options because its purpose is to review and propose in-lake options for managing algal blooms. However, we note that ongoing evaluation of stormwater volumes and nutrient loads is required and that the success of these will determine the longevity of in-lake management options.

Conceptual models showing the state of the lake in 2008 (Management Plan), and a scenario of a transition to a eutrophic system highlighted the potential outcomes that could occur with continued excess nutrient inputs, such as algal blooms and fish kills. It is clear that some of the anticipated issues identified in 2008 have come to eventuate in 2018 and that more active management intervention actions are required.

Computer Modelling showing aeration giving the best result in Algae reduction. (green Line)

Water quality of Lake Hugh Muntz has deteriorated markedly over the past 15 years.

Once management actions are adopted at the whole lake scale, an idealised scientific approach of a single action followed by observation(s) is not generally possible or desirable, and the approach should be to adopt multiple management actions concurrently. For example, if a geoengineering material (Phoslock etc) was applied within the lake, then catchment management actions should be adopted concurrently, to maximise the duration on which the geoengineering treatment was effective.

Conclusions:

  • In the shorter term, managing blooms using interventions within the lake is likely to be the most cost-effective option. Our lab analyses showed positive effects, both for the application of hydrogen peroxide and PhoslockTM but other chemicals (e.g., PAC) may have complementary effects related to additional inactivation of phosphorus.
  • It is important to note that the application of hydrogen peroxide is only an intermediate solution and will not solve the underlying cause of cyanobacteria blooms (i.e., the combination of high nutrients and the shallow freshwater lens in the lake). Simulation scenarios indicated that complete overturn of the water column through installation of a bottom aerator (i.e., artificial destratification) was the most effective remediation method but it is very expensive and would elevate nutrients and salinity in the surface water layer as well as maintaining particulate material in the water column for longer periods of time. This technique may result in little change in water quality although it would reduce the incidence of surface blooms.

For immediate action, we recommend:

  •  initiating mesocosm experiments in the field, trialling the effectiveness of hydrogen peroxide and PhoslockTM under natural conditions. This will then demonstrate whether hydrogen peroxide is effective for C. ovalisporum at concentrations tested in the laboratory and minimising the effect on other algae and animals. Additionally, Phoslock trials will test how effectively the compounds reduces phosphorus concentrations in the water column, and caps the sediment.
  • water quality model runs to test adequate dosages and timing of application to avoid spending unnecessary resources and/or achieving sub-optimal results.
  • laboratory measurements to better understand the growth requirements and toxin production of C. ovalisporum isolated from Lake Hugh Muntz. This is a poorly studied species so the literature is not helpful for the modelling questions. Additionally, the isolates Lake Hugh Muntz will be locally adapted to specific salinity, temperature, light and other conditions. This information is crucial to effective modelling.