Sydney Harbour Coral Bleaching

 

Collecting photophysiological data using the Diving PAM

Samples that will be sequenced as part of this project have been collected during and are still being collected following the Sydney Harbour Bleaching event earlier this year. 

In April, during routine monitoring, we found corals in Sydney Harbor bleached for the first time on record. This followed the intense El Niño which occurred over the 2015/2016 summer, where harbour temperatures reached a staggering 26°C, a few degrees above average. At specific locations up to 45% of the corals bleached. This was at a time when the Great Barrier Reef was undergoing a mass bleaching event surpassing previous records. 

The corals in Sydney Harbour are definitely cooler water specialists, surviving winter temperatures of as low as 15°C and summer maximums of 24°C, which represents a large thermal range for coral survival. The fact that they bleached at these higher temperatures is not so surprising, but what we didn't expect to see was such a rapid change in their physiology, they paled in a matter of weeks. 

Bleaching is often the result of a synergistic effect of extreme water temperatures combined with high light levels, which further intensifies the stress. We believe that this combination of stressors tipped these otherwise resilient species into a state of bleaching. 

We reported this bleaching event and got considerable attention from the media...did you see us on TV? Check out these links to some articles!

 http://www.smh.com.au/environm...

 http://www.abc.net.au/news/201...

Also I was interviewed on ABC News 24- here is the link http://www.snappytv.com/tc/174... 

We have been monitoring this bleaching event since April and will have an update of how the corals are going soon! Stay Tuned!

So how are we monitoring this bleaching event?

1) Video transects of the coral populations over time at 2 Sydney Harbour sites

2) We have permanently tagged 60+ colonies at Middle Head and are taking photographic evidence of their recovery/mortality (see pictures)

3) Photophysiological data collection using the diving PAM underwater fluorometer which will help us determine coral health. See the picture of me above with the diving PAM. 

4) Taking coral samples from bleached and healthy colonies to look at the microbial communities present during such an event. It is these samples that are part of this project proposal. These samples will have the DNA extracted and sequenced using next generation sequencing. 

 

An example of a permanently tagged coral colony which has paled, photographed with a colour standard- Matt Nitschke

 

A permanently tagged coral colony which has bleached, photographed with a colour standard- Matt Nitschke