June 22, 2016

Bleaching Update from Reef Check Australia

Submitted by Reef Check Australia

Since February, Reef Check Australia teams have been out to more than 40 sites along the Queensland Coast and on Ningaloo Reef, Western Australia. You can see what our teams witnessed out in the field throughout Queensland with our field photo album.

In the midst of a whirlwind of fieldwork, we also finalized the report for our 2015/16 South East Queensland survey season. South East Queensland is home to numerous subtropical reefs, home to tropical, subtropical and temperate marine species. Results from 33 surveys conducted from September 2015 to May 2016 on sites from the Sunshine Coast to Gold Coast showed average hard coral cover of 20%, a reminder that these often over-looked reefs host important coral communities! Almost every survey recorded some evidence of coral bleaching (90% of surveys), but only affecting on average a small portion of the population (7%). Follow-up surveys on sites with higher levels of bleaching later in the year will help capture any evidence of coral mortality.

Our Great Barrier Reef survey season is still underway and we'll be sharing more detailed updates later this year.

Reports on the largest recorded global coral bleaching event continue to pour in around Australia and around the world. On the Great Barrier Reef (GBR), results from surveys conducted by the Great Barrier Reef Marine Park Authority and partners indicate that the overall coral mortality on the Great Barrier Reef is 22 percent. Much of that die-off (85% of observed mortality) has occurred between the tip of Cape York and just north of Lizard Island, 250 kilometres north of Cairns. Impacts vary widely across different reefs.

We've been getting lots of questions about what the “real” story is about bleaching on the GBR… but as you've probably noticed, it is a complicated story to tell. The GBR is the size of 70 million football fields, with depths from 1 to 2000+ metres, including 3000 reefs, and 600+ species of coral. The impacts of coral bleaching vary across this matrix of different regions and habitat types. Some areas will fare OK and some areas are/will be devastated.

Reefs are complex ecosystems and coral bleaching impacts can be considered at the colony, site and reef level. Different types of coral have different sensitivities to heat stress and even corals of the same species in a small area can demonstrate different responses to bleaching. At a single research site, surveys document the impact of bleaching at the population level (e.g. if 10 out of 100 corals are impacted, that's 10% of the population). Even within a reef, some shallow areas may be heavily impacted and other deeper or highly-flushed areas may show lower levels of bleaching. Therefore surveying many different areas on the reef can provide a representative sample for overall impact at the reef level. This explains why you might hear about some varying numbers for the level of bleaching impact.

But the resounding message is clear–this is our call to action. It's not too late, but decisive progress in how we work together to look after reefs is critical. We need to relieve immediate reef pressures such as water quality issues or localised overfishing. We need to support investment in the systems, policies and collaborations that manage reefs. We need to help find better ways to quickly document and understand major events that impact reef health (citizen science can help!)

We are dedicated to reefs and we challenge you to look for ways to transform your love for reefs into tangible actions in your life. Instead of pointing fingers, now is time for people to unite and work together.