2006/16 – Candowie Reservoir (Victoria) – Anabaena solitaria, Anabaena circinalis, Anabaena perturbata, Microcystis aeruginosa, Aphanizomenon gracile, Microcystis flos-aquae

Candowie Reservoir – Victoria
2006/7: An increase from about 240 cells/mL in early July 2006 to 4,000 cells/ml in early August of Anabaena solitaria , a potentially toxic blue-green algae, was detected and a bloom was predicted. Approximately 1.5 kL of Cupricide was dosed into the reservoir on the 25th
of August. Algicide was not used for the rest of the 06/07 reporting period…
Little algal growth was detected over the summer period (December to February). Low levels (<30 cells/mL) of the potentially toxic blue-green Microcystis aeruginosa were present at all storage depths in January 2007. However, constant oxygenation of the bottom waters has prevented the development of conditions favourable to algal growth.
https://www.westernportwater.com.au/wp-content/uploads/WebFiles/Services/DHS%20annual%20water%20quality%20report%202006-07.pdf
2007/8: Low levels of the potentially toxic blue-green Microcystis aeruginosa were present between August and October, but only at shallow depths to one metre. Microcosm Consulting determined that these colonies were old and had probably remained in the water column since
last autumn, no new growth was detected….
An increase from approximately 100 cells/mL in late February 2008 to 2,200 cells/mL in March of Anabaena solitaria was abundant at all depths. Aphanizomenon gracile also bloomed during the same period. As both species are listed as non-toxic, copper treatment of the reservoir was not required.
https://www.westernportwater.com.au/wp-content/uploads/WebFiles/Services/DHS%20annual%20water%20quality%20report%202007-08.pdf

2008/9: A significant increase in potentially toxic blue-green Anabaena circinalis occurred in April and the reservoir was treated with Cupricide on the 5th of May, 2009. Sampling on the 13th of May,…https://www.westernportwater.com.au/wp-content/uploads/WebFiles/Services/DHS%20annual%20water%20quality%20report%202008-09.pdf

2009/10: Nevertheless, blooms of taste and odour causing Ceratium, a large dinoflagellate, were detected throughout the reporting period. The behaviour of this Ceratiumbloom was totally unpredictable even though the nitrogen to phosphorus ratio was not ideal for its growth. However, the Ceratium bloom may have helped suppress Anabaena growth over the summer period. A significant increase in potentially toxic blue-green Anabaena circinalisoccurred in December and the reservoir was treated with Cupricide on the 20th December 2009. Sampling on the 23rd of December, 2009 showed that the treatment was successful.

2010/11: An increase in the potentially toxic blue-green Anabaena circinalis occurred in February and the reservoir was treated with Cupricide on 1 March 2011. Sampling on 3 March 2011 showed that the treatment was successful.

2011/12: The Candowie Reservoir experienced three algal blooms between December 2011 and March 2012. An increase in the potentially toxic blue-green Anabaena circinalis occurred on 7 December 2011 and the reservoir was treated with cupricide on 9 December 2012. Sampling on 11 December 2011 showed that the treatment was successful. An increase in the potentially toxic blue-green Microcystis Aeruginosa occurred on 7 March 2012. Cupricide treatment was applied to the reservoir on 16 March 2012. Sampling on 19 March 2012 showed that the treatment was successful with no Microcystis Aeruginosa detected . It was almost immediately replaced by a bloom of the potentially toxic blue-green Microcystis flos-aquae. Following discussions with Dr Barbara Bowles, DH and the Department of Sustainability and Environment, the potentially toxic bloom was left to evolve and die out naturally. Sampling on 28 March showed that the Microcystis flos-aquae numbers had peaked and were on the way down.

2012/13: … an algal bloom was identified on Wednesday 19th December 2012, which contained toxic species Anabaena circinalis and Microcystis spp…

2013/14: 2013-14 was no exception, and an algal bloom was identified on Friday 27th December 2013, which was dominated by non-toxic species Anabena Perturbata and contained traces of potentially toxic Anabaena circinalis… The bloom continued to prosper with favourable conditions throughout all summer and lasted until May 2014. At its peak, cell counts of Anabena Perturbata were approximately 7.78 million cells/mL with a biovolume of 2,100 mm3/L (the highest ever witnessed in Candowie Reservoir) and the potentially toxic Anabaena circinalis 170, 000 cells/mL (with a biovolume of 42.5 mm3/L). Toxicity testing indicated the present Anabaena circinalis to be non- toxic. Throughout the entire bloom cycle, integritytesting of the clear water storage indicated no presence of cyanobacteria (blue green algae) in the treated water. However, cyanobacteria have the ability to produce a compound called Geosmin which carries an earthy taste. The structure of these compounds are not susceptible to oxidation and other conventional treatment methods making them difficult to detect and remove. Geosmin wassampled at high levels throughout the bloom period…

2014/15: An algal bloom was identified around Christmas Day with potentially toxic species evident in the profile samples. The bloom reached its peak in early February. Toxicity testing indicated a small amount of microcystin toxin in the raw water but was below the guideline limit for public health. Sampling of the clear water storage proved that the treatment process was successful in removing algae and associated metabolites. There were no taste and odour complaints related to algal blooms throughout 2014-15. Sampling in the clear water storage in late February indicated the presence of algal cells of a non toxic species (Anabaena Perturbata).Breakthrough of algae through thefiltration process was a concern of WPW due to widespread complaint of taste and odour (associated with the algal species) in 2013-14…

2015/16: Candowie Reservoir experienced a seasonal blue algal bloom throughout 2015-
16. Algae species reaching bloom levels were identified in January and persistent until May 2016.