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Bloomin’ algal blooms
  |  First Published: October 2011



Last month I spoke about September being a month that all Teewah Beach anglers tend to associate with greenback tailor. And up until 2001, we all would have been thinking about another month of more greenback tailor. But since then, things have drastically changed.

Regular readers of this column would be aware that I have written many an article about coastal algal blooms and in particular the affects these blooms have on Cooloola and Fraser Island. Although it would be much more fun for me to write about fish being caught and the promise that the month ahead offers, I'm afraid that there would be very little for me to write about at this time of year. Just as is the case when netting is occurring between May and August.

I believe that to offer false hope to anglers by writing unrealistic articles about fish that haven't and won't be here, is simply unethical. I would rather leave fictitious writing to the authors of novels and for me to provide accurate assessments to my readers who can then decide where best to spend their time and money.

October is the month that Anaulus australis makes its now annual appearance in the surf zone of Cooloola and at Fraser Island. The last decade has seen this algae consistently occur in conjunction with a sequence of warm sunny days and I have little doubt that this year will be any different.

Adding to my certainty is the fact that Anaulus australis has been present in small quantities throughout this winter which has never occurred before. Usually, the onset of winter and the reduction in water temperatures causes the algae to die off in April/May, which provides clean surf conditions. The fact that the algae did not die off completely in winter, means that the first sunny and warm days that arrive this month are guaranteed to cause a bloom.

A bloom in itself does not prevent fishing, as Anaulus australis is a microscopic algae that doesn't foul the line like Hincksia sordida or Lingbya. What it does do however is deplete oxygen levels of the water, which makes affected areas very uncomfortable for the fish to be in. Therefore the fish tend to avoid affected areas and stay in water where breathing is easier.

Given that an Anaulus australis bloom last summer extended from Ballina in the south to Yeppoon in the north, there can be an awful lot of water for the fish to avoid. But due to the fact that Anaulus australis is an algae that proliferates in the surf zone, it is generally only the surf which becomes almost devoid of fish. This, of course, is of little value to the land-based beach angler.

All I can suggest for those who wish to persist irrespective of the algae, is to fish from rocky headlands such as Double Island Point or Noosa Heads or to fish at night. The reasons for this is the nature of the algae and the environment in which it exists.

Anaulus australis cells survive almost exclusively in sandy environments. At night, the cells attach themselves to sand particles on the seabed. When the sun comes up in the mornings, the cells then detach from the sand particle and attach themselves to air bubbles created by the action of the surf. The air bubbles rise through the water column with the cell attached and the cells undergo mitosis and divide into two cells, which each divide into another two cells and so on. As the sun sets, the cells detach from the air bubbles and sink to the seabed again.

In ideal conditions, an Anaulus australis bloom can grow at the rate of hundreds of hectares per hour due to the efficient method of cell division. Similarly a bloom can disappear within hours of a cool southerly wind change, which brings cloudy conditions and causes the cells to stay on the seabed or to die off as they need sun to energise photosynthesis to create their energy and food. However, as soon as the sun comes out again, then the algal cells rise with the air bubbles, photosynthesise, divide and the bloom is once again in full swing.

Ideal growing conditions for coastal algae are warm to hot sunny days following spring or summer storms that cause nutrient carrying run-off. If, as often occurs in South East Queensland, there is a sequence of particularly hot days of over 30ºC, with or without storms, the surf zone invariably turns brown with algae.

Several inches of rain at any time between September and April will also cause a bloom to occur when the sun comes out following the rain event. Nutrient run-off from the land is flushed out into our bays which feeds the algae as fertiliser feeds our terrestrial plants.

Phosphate has been identified as a nutrient that causes coastal algal blooms which has led to most of the states of the United States banning phosphate use. The Western Australian government is in the process of doing the same due to the increasing incidence of blooms there.

The Queensland Labor government is said to be working closely with agricultural farmers adjacent to the Great Barrier Reef in order to address algal issues that are a very significant problem along its full length. Though banning phosphates has yet to be considered here, it would seem that such a measure could be worth adopting, particularly so as our soils do not require the addition of phosphates like some other countries.

Although the state government is said to be trying to address algal blooms on the Great Barrier Reef, there is no evidence that any effort is being put into addressing blooms here. There is no testing in this region of water either in the estuaries or the ocean to determine nutrient levels or which algae are present. Some testing did occur in 2006 when Main Beach Noosa was badly affected by Hinckisa sordida between 2001 and 2006, but nothing has been derived from that and no efforts of any kind have occurred otherwise.

To be realistic however, I'm not sure that this problem is fixable. As our human population grows and more and more nutrients are used and flushed into our estuaries and lakes, blooms are only more likely to occur. It will certainly take a radical stance by government in reducing nutrient outfalls before there is any prospect of reducing the incidence of algal blooms. Warming of the oceans however could nullify any actions taken.

While current or increasing nutrient outfalls are allowed to continue, along with rising water temperatures, we really have no chance of effectively addressing the problem at all. Exacerbating this further is the continued unsustainable commercial harvesting of fish and shellfish, which are the natural predators of the algaes.

As far as I know, there is only one thing that can temporarily kill off an algal bloom altogether and that is a cyclone or low pressure system that pulverises the algae in the big seas. This occurred once in February 2004 which gave us more than months of good fishing in clean water before the pros arrived in May and shut the whole thing down, as always. While I doubt that many would wish for a cyclone to hit our shores, I am.

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