Recovery of Sydney corals following bleaching serves as natures warning shot!
You may have seen me and my team on ABC 7pm news recently talking about the Sydney Harbour corals! This story was to report that after the Sydney Harbour coral bleaching event in April this year, almost all individually tracked corals are now, 5 months later, showing signs of renewed health!
If you missed this story please check out these links below!
http://www.abc.net.au/news/201...
http://www.gizmodo.com.au/2016...
http://www.huffingtonpost.com....
After the bleaching event in April (see lab note #1), where up to 45% of corals at selected sites were bleached, we monitored the corals at Middle Head and Fairlight weekly to collect data on coral recovery/mortality.
What we found was that following return to typical water temperatures, there is a strong aptitude for recovery in the harbour corals. Like their tropical counterparts, the Sydney harbour corals appear sensitive to temperatures above normal. However when temperatures returned to normal, the widespread coral recovery observed suggests these corals may also have some unique mechanism within their biology that makes them incredibly hardy. Their condition is even more impressive given that the recovery period also included a significant storm event for Sydney Harbour, which would have limited light availability for some time and altered environmental conditions significantly.
What we are trying to unravel are the factors at play that determine the winners and losers in corals populations and reefs during extreme events, such as this bleaching event. We can learn a lot from the Sydney corals who have bounced back from this stressful event!
Our methods include:
- Photograph all tagged colonies with colour standard to determine recovery
- Collect photo-physiology data to indicate coral health using the diving PAM.
- Collect tissue samples for microbial analysis. With this we can tell if there have been any shifts in the bacterial or algal communities during the bleaching event.
- Determine the unique biology of these corals by measuring metabolic properties such as calcification and photosynthesis- see lab note #3.
Continued monitoring is required to understand if this has occurred in isolation or is something we can expect to see repeated on a yearly basis. We know that coral ecosystems and populations can bounce-back from disturbances, but this is highly dependent on a sufficient disturbance-free window of time. The Sydney corals were lucky in that temperatures returned to normal relatively quickly. This does show us that cooler water organisms are not immune to the effects of warming sea surface temperatures.
With the global coral bleaching event into the second consecutive year, we can only see this as natures warning shot. The recovery mechanism following stress for these corals is yet to be identified, but this is important if we are to understand coral resilience into the future.
During bleaching and post bleaching recovery. Photo: Matthew Nitschke
