Why Australian mountain wildfires in 2006 caused these lakes to glow in 2008

Phil Hart works every summer in the Gippsland Lakes area of Australia, and three years ago he observed a bizarre, blue glow in the lakes at night - but only when the water was disturbed.

He took several haunting pictures of the phenomenon, which have been passed around online without much explanation. The light show was caused by an enormous bloom of bioluminescent bacteria in the water, but there's a lot more to it than that. Why was there suddenly be so much of this unusual bacteria in a region where nobody had seen it before? Had pollution caused it? Nope. Without any intervention from humans and our environment-munching devices, the planet created this bizarre and seemingly unnatural event. Hart explains that it all started with wildfires back in 2006:

The story begins with alpine bushfires in Victoria, which started on 1st December 2006 when over 70 fires were started by a band of thunderstorms and lightning strikes which moved across the state . . . The fires burnt for 69 days, merging to become the ‘Great Divide Complex' and ultimately covering an area of well over a million hectares.

Such a large and in places severe fire through the catchment areas was always going to have an impact on the lakes themselves but a lot would depend on the intensity of rain events that followed the fires . . . A deep east coast low pressure system dumped more than 100mm of rain over many locations across Gippsland on 27th June 2007. The result was a 1 in a 100 year flood in the days and weeks that followed.

The effect of the torrential rain over the over the vast area of recently burnt alpine forest was to wash ash and soil rich in nitrogen and other nutrients into the Gippsland Lakes. Counter intuitively, the rain and floods also increased salinity in the Lakes as the higher water level facilitated greater mixing with seawater at Lakes Entrance.

As a result, the lakes were filled with the kinds of nutrients beloved by algae.

Hart continues:

The growth of algae in the lakes is affected by a number of factors, including the availability of nitrogen, phosphorous and other nutrients in the water as well as the temperature and salinity of the water. Growth of Synechococcus was favoured by higher nitrogen and salinity levels while the classic blue-green algae (which are actually bacteria) required lower salinity levels and higher phosphorous levels. As summer took hold at the end of 2008, what happened surprised everyone – a new species called Noctiluca Scintillans began to prosper, by feeding on the Synechococcus.

In contrast to the widespread bright green of the Synechococcus, Noctiluca Scintillans was visible during the day as localised murky red patches, often building up on sections of shoreline facing the wind during the day. At night though, Noctiluca Scintillans produced a remarkable form of bioluminescence (popularly referred to as ‘phosphorescence') – the water glowing brightly wherever there was movement – in the waves breaking on the shore, in ripples in the water and wherever people played in the water.

So what you're seeing here is a second generation of algae (Noctiluca Scintillans) which grew by eating the first generation of algae (Synechococcus), which itself bloomed by feeding on the runoff from the floods, which had been filled with nutrients from wildfires. Basically, this event was two years and two disasters in the making - and it was also completely harmless. The glowing algae are not toxic, and did not wind up choking off other life forms in the lakes. In fact, they died back naturally in the next couple of years as they consumed the food supply that had caused them to bloom in the first place. Read more about the phenomenon, and check out more of Hart's amazing pictures, on his blog.

Why Australian mountain wildfires in 2006 caused these lakes to glow in 2008S

Why Australian mountain wildfires in 2006 caused these lakes to glow in 2008S

Why Australian mountain wildfires in 2006 caused these lakes to glow in 2008S

Why Australian mountain wildfires in 2006 caused these lakes to glow in 2008S