2015-2017 Global Coral Bleach Event

You’ve probably heard in the media about coral bleaching and may be wondering if it will affect your visit to the reef. Since April 2016 we’ve been providing updates on the areas we visit. The latest update is at the top of the page.

17th March 2017 Update  Please also read the information further below from April, May, June and August 2016 which has been left here unchanged, as a record of last year.

Opal Reef March 2017

The last 6 weeks have seen the start of mass bleaching following on from last year’s event. This is a huge blow to those people concerned about the reef’s health. In the winter months cooler temperatures saw corals that survived last year’s bleaching recover their normal colour. Just since the beginning of February however, warmer than normal seawater and calm, sunny weather have combined to initiate more mass bleaching. It’s likely that corals have not fully recovered their reserves yet from last year and may be more vulnerable to bleaching now. The annual coral spawning last year was also weak, most likely also due to weakened coral having a reduced ability to form gametes. This is obviously bad news for reef recovery.

                                                                                                                         Opal Reef March 2017

During the past month our passengers have witnessed the bright fluorescent colours of coral that is the early sign of heat stress. The reef looks more colourful than it should, but this is actually a bad sign. Many of these fluorescing corals will turn paler and eventually go white, and this has started in some areas, though not much at Opal Reef so far.

Last year sea surface temperatures on some Far North parts of the reef were up to 32 degrees Celsius for up to 2 months. Our measurements have recorded temperatures of 30.8 degrees recently. Whilst it’s not quite as hot as last year, we still have a very widespread sea surface temperature anomaly of around +1.5 degrees in the Southern Pacific. At this stage it’s not possible to say how severe the bleaching will become and what mortality will result, but the expectation at the moment is that it will likely include areas further south than last year. The ongoing weather forecast is for more calm and sunny conditions.

This event is a highly visible reminder that greenhouse gas emissions are changing the environment that we depend upon in many different ways, including economically. Irrespective of one’s own political leanings this has to be addressed by community oversight of our leaders to follow through on the commitments made at the Paris Agreement.

20th August 2016 Update

We haven’t posted a bleaching update for a while because there’s been very little change since the last one; however we’ve had lots of requests for an update, so here it is.  For those interested, we’ve also given a little bit of personal interpretation of the political background to the news coverage that occurred during the bleaching event.

In this area the bleaching event finished with the arrival of cooler conditions by June. The 2015/2016 global event is still continuing though, and now badly affecting coral reefs in the northern hemisphere coinciding with the northern summer. Some of the links on our website give more information about this.

In our region, most of the coral has recovered but some shallow fast growing coral has died. We’ve spent a couple of weeks travelling around the local region by boat comparing different reefs and the amount of mortality has been patchy and very much as described by GBRMPA. At Opal Reef we were at the edge of the area further north where bleaching was worse (described below in previous month’s updates). The southern reefs of the Cairns area like Moore Reef have pretty much escaped the impacts of bleaching, as have inner reefs like Low Isles, Fitzroy Island and Michaelmas Cay.

After a couple of days any dead coral is covered with turfing algae and then becomes a grazing area for herbivorous fish. In any given spot, where the proportion of live coral is still high, as at most of Opal Reef , it’s hard to notice much difference unless you knew the site pretty well before February, and any recently dead coral is indistinguishable from older coral rock. This is the current status. Based on our passenger feedback, and the positive visitor comments on Tripadvisor from over the region, people are still having a great experience visiting the reef here. Of course, we still think Opal Reef is one of the best reefs on the GBR to snorkel at, even though it’s had a knock since last year.

From our point of view, the problem has now changed. Crown of Thorns Starfish (COTS) and Drupella snails both eat significant amounts of coral and are attracted to weakened coral that has suffered disease or bleaching. Since June we’ve seen a dramatic increase in these coral predators and are actively removing them, not just at our sites but all over Opal Reef. AMPTO operate a dedicated vessel which is continuing to look for, and deal with, COTS in the region.

Another worry is how well the coral will spawn this year in November. Coral recovering from bleaching has fewer body resources to produce eggs and spawn, yet we need good spawning to help replace coral that has died before the next bleaching event comes along.

1st June 2016 Update    Please also read the information further below from April and May.

Recently recovered polyps

Recently recovered polyps

This week we’ve had two scientists from James Cook University who’ve been involved in the coral bleaching monitoring program out on Wavelength at Opal Reef. The encouraging thing was that they found the condition of the coral at the sites visited much better than expected and lower coral mortality than expected. They confirmed the bleaching has been very serious further north with the area around Lizard Island particularly bad.

There’s been a lot of information in the media where “percentage mortality” is mentioned. This is only a part of the story. For example, a reef can have 80% live coral cover and 20% mortality and be left with 64% live coral. Another reef may start with 40% live coral and have only 5% mortality, and so be left with 38% live coral. So the first reef will still look healthier. The southern part of the reef has had very little coral mortality from this bleaching event, but that’s also the area that’s seen the largest prolonged loss of coral cover over the last 30 years.

Opal Reef started with a high coverage of live coral and lots of live coral remains. This is looking considerably healthier than last month. Clams also bleach but luckily all have survived and are a normal healthy colour. Anemones bleach too and they remain very pale, but have survived. The coral at the Low Isles off Port Douglas has coped well.

Opal Reef May 2016

Opal Reef May 2016

Sadly in April and May, large staghorn coral over shallow sand, small branching coral colonies on the reef crescent and, to a lesser extent, some plate corals, have had significant levels of mortality due to bleaching. In areas dominated by this sort of coral the percentage of mortality is high. Some of our sites include this sort of coral on parts of the site but other parts of the same site are much less affected. Sites without much of that sort of coral are hardly affected at all and, contrasting with further north, we haven’t had mortality of slow growing corals.

The other encouraging thing is the impact on the fish population. Herbivorous fish and plankton eating fish can even benefit with an increase in fish like parrotfish and surgeonfish after a year. As long as remaining live coral cover stays above 10% (it’s still well above this) specialist coralivores like the lovely Harlequin Filefish, which feeds exclusively on coral polyps, should maintain a viable population until coral cover improves. Longer term, after about four years, the structure of the reef can have broken down enough to significantly remove shelter and habitat leading to a drop in fish numbers. After more time passes the reef structure can be so worn down to rubble that fish numbers are severely reduced. With clear ocean water at Opal Reef we’re optimistic though that the combination of surviving coral, and fast growing species, will maintain good habitat over the coming years unless we have another big bleaching event soon.

We’ve heard the effect of bleaching being likened to cyclone damage, but it’s very different. The nooks and crannies the fish need for homes are still there following mortality from bleaching. We did have a site destroyed by Cyclone Ita in 2014 which we no longer visit. That demonstrated how the reef can be flattened and all fish habitat removed and how a cyclone has a much larger local impact on the fish than coral bleaching.

So this page gets longer! But how much coral bleaching effects visitors to this area is complicated. It is absolutely wrong to cancel a visit to the reef due to the news coverage. However, on a reef trip it’s also likely you’ll notice that bleaching has occurred. If you know what to look for you’ll be able to find dead coral. You won’t notice any difference in the fish or reef creatures. Experiencing less than ideal weather, or getting a day when the turtles or sharks don’t show up will have a bigger impact on your day. So we hope people keep visiting and we get the opportunity to show the reef’s beauty, and the story of what’s happening and why it’s important. Coral reefs all around the world are deteriorating but this reef still boasts some of the best coral and fish life anywhere.

Opal Reef May 2016

Opal Reef May 2016

May 2016 Update          Firstly, please read the information further below from April.

Since April we have strong signs of recovery, but it’s also become much clearer how much coral mortality has occurred. The bleaching has been patchy and subsequently there’s higher mortality in areas where the bleaching was more severe. Boulder corals have been affected very little in the areas we visit, and also soft corals have been little impacted and are regaining colour well.  Plate corals and staghorn corals have been impacted the most, with higher mortality in shallow areas, especially where the reef topography creates areas that get extra warming on hot days and slack water. Bleached staghorn corals that are recovering have regained their normal colour on the underside of branches first.

We’re very fortunate in having a broad range of sites so we can still visit areas where the reef appears little affected. However, there are places offshore this coastline where the level of coral mortality that’s occurred in the last month is shocking – and it’s worse further north over a vast area to the northern tip of the GBR. Our passengers are still having a great experience and impressed with the coral, but that shouldn’t confuse how serious this bleaching event has been. Coral reefs worldwide have been badly impacted, following the same pattern as the previous strongest recorded El Nino event in 1998, except more severely. Very strong evidence indicates that these events will become more frequent, reducing the ability of coral to recover in between.

Opal reef May 2016

Opal reef May 2016

There is no question that the ultimate cause of this global bleaching is greenhouse gas emissions, amplified by El Nino conditions. The GBRMPA, which is a Commonwealth Government organisation, is very clear on this, as are the numerous other organisations involved in reef research and monitoring. Coral reefs are very able to recover from catastrophic damage as long as the correct management policies are in place. The coral cover in this region should still be able to survive longer term, (albeit with reduced diversity) up to a point where the high amount of carbon dioxide in the ocean and atmosphere will eventually result in an algal dominated reef which has much less ecological and economic value. That would most likely be below, or up to, an atmospheric  carbon dioxide concentration of about 500 ppm, projected to occur by 2050, or soon after, on our current track.

This global bleaching event must be taken seriously as the strongest possible reminder that we have to reduce fossil fuel use faster, and we have to develop and implement the technology of the clean energy revolution faster. Good legislation to put the Paris Agreement into effect and create genuine emission reductions is vital.


April 2016

You may have heard about coral bleaching on the Great Barrier Reef. Just now, with cooling seawater temperatures, we are coming out of a major bleaching event after the ocean and weather conditions that can induce bleaching peaked in February.

What does coral bleaching look like?

During a bleaching event much of the coral is more colourful than normal, particularly with more vivid pinks, blues and purples. This is a sign that the coral is struggling before it may eventually go white. If conditions then last more than a few weeks the coral will eventually starve and die. If it dies it’s a very short time before the coral rock is covered in algae, and the result is a degraded reef. Some staghorn corals grow as fast as 15cm a year so after several years the affected reef can substantially recover if the water quality is good.

Three stages of bleaching

Three stages of bleaching

What’s it like off Port Douglas?

Luckily, during most of March a monsoon trough sat right over this region bringing cloudy weather. Although this wasn’t enough to stop coral bleaching it helped and bleaching on the reefs off Port Douglas appears to be patchy and mainly limited to minor below one or two metres, and moderate in the very shallow areas. This means that the coral here can be expected to recover over the next few months, with hopefully minimal mortality. Ironically, healthy coral is mostly yellowy-brown due to its symbiotic photosynthetic algae, so it’s normal for some visitors to assume healthy coral is bleached or even dead. We don’t know of any of our passengers that have noticed coral bleaching until it’s pointed out to them, and more passengers than usual in the past two months have commented on amazing reef colours. The fish life is just as normal. The visitor’s experience is not impacted by events so far. We were lucky here with local weather conditions. As of April the story is still unfolding. More surveys are discovering the severe level of damage done in the past couple of months further north, yet the extent of eventual mortality or recovery is yet to be seen. Fortunately the water quality on the reef is best in northern waters which will be a help for recovery.

Does this mean that everything is ok?

No, definitely not. Reef scientists do a vital role to monitor and report on the reef’s health and they are shocked by the extent of bleaching in the very far north. The area northwards from Cooktown is where coral was previously considered the most likely to be resistant to bleaching. More bad news is likely to emerge as they do in-water surveys to follow up the aerial surveys recently publicised.

Evidence from coral growth rings suggests that mass coral bleaching was not normal during at least the last 400 years, with the first record of global bleaching being 1998, another in 2010 and this being the third. Mass bleaching events on the Great Barrier Reef have occurred in 1998, 2002, and 2006. The combination of a warming trend and also a strong El Nino seems to have made this years event the most serious bleaching yet recorded on the reef. Predictions are that coral bleaching events will become so regular that the reef won’t be able to recover in-between. Consider that, although the coral animal has been around for millions of years, the Great Barrier Reef as we know it is only 6,000 to 8,000 years old and has been in its current form just since the end of the last ice age, during which time it has experienced stable conditions.

Coral reefs are one of the most vulnerable ecosystems to climate change. Reef scientists are expressing justified frustration at the slowness of collective global policymakers to move to a low carbon economy. The timing is particularly relevant too, with the warmest February and March ever recorded, and the largest ever annual jump in the atmospheric CO2 level. Just in my lifetime atmospheric CO2 has jumped from 320 to 400 ppm, with vast quantities of extra CO2 dissolving in the ocean. Separate from warming, on this track, by 2050, ocean acidification will mean all coral reefs worldwide will be eroding and dissolving faster than organisms can build them.

Is this bleaching event important?

On a geological time scale the reef has recovered from major traumas, including major sea level changes in the last 500,000 years with the continental shelf being repeatedly exposed then flooded. Coral reefs in the past have also recovered and adapted from changes in atmospheric CO2 and sea surface temperature.

The difference today is that the rate of change of atmospheric CO2 is very fast, which creates a problem for organisms to acclimate or adapt. In addition, the reef is affected by human pressures like fishing and agricultural runoff. These factors are thought to dramatically reduce the ability of the reef to recover from damage. For example, over-fishing of herbivorous fish will reduce the grazing of algal turf making it harder for new coral larvae to settle. Excess nutrients from agricultural run-off make it easier for algae to remain dominant on a degraded reef and harder for coral to recolonise.

Studies show that between 1985 and 2012 half the coral cover on the reef was lost, with 48% of the loss due to storms, 42% due to Crown of Thorns starfish outbreaks and 10% due to bleaching. In the absence of these impacts the estimated recovery in coral coverage would be 2.8% per year. The reef will not disappear but it’s health and diversity over a timescale that affects us and the next generations is on a poor trajectory. It is sadly a similar, or worse, story on coral reefs worldwide. It’s not all bad news though, because the potential of reefs to recover shows that good policy decisions can turn things around.

What’s being done?

Currently reef scientists are doing extensive surveying to monitor the bleaching event. Overall, reef managers have been aware of the risks of climate change already and have been working to improve the ability of the reef to resist damage, and recover from it. GBRMPA have been working for a considerable time to best manage the fishing on the reef. A program has been in place for a while to attempt to monitor and control Crown of Thorns starfish numbers. There is currently a renewed focus (and funding) on improving water quality, particularly in agriculture runoff but also with recent laws to reduce the amount of dredge spoil from ports which can be disposed of at sea. These things are aimed at making the reef more resilient to climate change. GBRMPA are also very active, along with other scientific and government institutions, in long term monitoring of the reef. In Queensland we are in a better position for our reefs to recover from bleaching than most other coral reef locations.

What can WE do?

What should we do though on a personal level? Apart from support the efforts to improve the reef’s resilience, the only thing we really can do is use our buying and voting powers, and what voice we have, to help speed the move to a low carbon economy. Also, visiting the reef is still a fantastic experience and tourism contributes to the economic case to protect it, as well as making for a better informed public when it’s seen in person.

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