Healthy Reef on Holbourne Island

Much of the reef around Holbourne Island has been badly damaged, either by Cyclone Debbie or by crown-of-thorns sea star grazing. On a trip to this island in August I explored the NE face of the Island where we have not dived for a few years. I found that this side of the island had not been badly damaged by Cyclone Debbie. On the south end of this face was an extensive bay that supported a rich and almost undamaged reef.

Drone view of the NE face of Holbourne Island. The bay on the left end, between the islet and the main island had very lush growth of healthy coral in August 2020.

This bay had very lush coral growth with more than 50% cover of healthy corals. Many species were represented but Acropora and Montipora corals were most common. The slide show below has a number of photos taken throughout this bay showing the amazing growth of corals.

Central GBR Coral Bleaching Update

I reported earlier on the impact of the 2020 coral bleaching event on our local Whitsunday reefs. We have since found that reefs have also been badly bleached in the Bowen/Cape Upstart region and in the Mackay region. When we did our April surveys on four islands near Mackay we found that between 40-70% of corals were badly bleached with some mortality already happening. During May we found bad bleaching on our survey sites around Bowen with substantial mortality of some coral groups. Bleaching had reduced coral cover on Camp Island reefs, near Cape Upstart, from 25% down to 17% with mortality still ongoing.

When we checked on our local reefs again in July and August we found that some corals had died, some had recovered but others were still badly bleached more than three months since the bleaching event began. Fully bleached corals are not meant to survive more than three weeks but that has not been the case here. It has been found that corals on inshore reefs can get food by absorbing organic detritus that falls on their surface and it may be that this is enabling corals on these fringing reefs to survive for many months even when badly bleached.

Most bleached Millepora or fire coral colonies have died as have many pocilloporid corals and some acroporid corals. In many cases only part of a colony has died with some parts managing to survive. The full extent of reef damage that has been caused by this widespread bleaching event will not be clear for some months. The good news is that when we drove north to resurvey reefs around Snapper Island near Port Douglas we found no evidence of coral bleaching around that island.

Drone view of the Saddleback Island reef in early April 2020 showing the extensive stands of white bleached corals along the shallow reef edge.

Drone view of the same section (but reversed) of Saddleback Island reef in late July 2020 showing most of the shallow water bleached corals have either recovered or died. Look closely and a few white spots, indicating bleached corals, can still be seen.

Partly bleached, partly dead Porites colony on Saddleback in late July

Mostly dead Montipora colony on Saddleback in late July

This previously bleached Acropora plate has completely died

This clump of previously bleached Acropora corals on Saddleback have recovered

Pachyseris coral colony still badly bleached on Saddleback in late July

Most of this Acropora staghorn clump has died but small patches have recovered

This Montipora colony was still completely bleached in late July

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Bleached corals on Keswick Island off Mackay in late April 2020

Drone view of the Camp Island reef in May 2020 showing the numerous bleached Montipora colonies along the shallow fringing reef

Bleached Acropora staghorn corals on St Bees Island off Mackay in late April 2020

Bleached corals on Slade Islet off Mackay in late April 2020

Bleached Montipora corals surrounding healthy Psammocora coral on Victor Islet off Hay Point

Bleached Acropora staghorn at Camp Island near Cape Upstart in May 2020

Healthy Acropora staghorn at Camp Island

Part bleached, part dead, part recovered Acropora staghorn at Camp Island

Bleached Montipora corals at Camp Island in May 2020

Widespread Coral Bleaching in Whitsunday Region and Elsewhere on the GBR

During the first few months of 2020 clear skies and calm weather led to very warm water temperatures throughout most of the Great Barrier Reef region. Water temperatures exceeded 30°C for many weeks. It is now becoming clear that this warm water has caused another mass coral bleaching event even more widespread than the catastrophic bleaching events of 2016 and 2017. Inshore reefs the entire length of the Great Barrier Reef have been affected as have offshore reefs between Cairns and Mackay.

This widespread coral bleaching event has impacted reefs in our area of the Whitsundays. Recent surveys on Rattray and Saddleback Islands reveal the extent of the problem.

Drones-eye view of the fringing reef at Saddleback Island showing the pale bleached corals on the reef slope and outer reef flat

All the acroporid and pocilloporid corals in shallow water were completely bleached but a range of other coral species were also bleached down to over 10 metres depth. Many of the soft corals were also bleached as were most fire corals. Many of the corals were fluorescing bright colours, a common occurrence during bleaching events. Although most of the corals were still alive some colonies were partially dead. Water temperatures a few days ago were 28°C, down several degrees from the summer peak. It is possible that many of the bleached corals will be able to recover their zooxanthellae and survive but this is going to be a slow process.

The brown parts of this bleached Acropora staghorn colony have already died. It is too early yet to tell how extensive coral mortality will be due to this bleaching event.

Drone shot of the fringing reef on the east side of Saddleback Island showing the fringe of white, bleached corals.

Band of bleached corals in Bommie Bay on Saddleback Island

Badly bleached Seriatopora colony at 10m depth on Saddleback Island

Partially bleached corals at 10m depth

Goniopora corals rarely bleach but this small colony at 10m depth is badly bleached

Badly bleached Lobophyllia coral (right) with other partially bleached corals

Totally bleached Millepora fire coral

This huge Leptoria coral colony is completely bleached but still alive

Bleached and florescent soft corals

Partially bleached Sinularia soft corals

A variety of bleached corals on the shallow reef slope at Saddleback Island

Bleached and florescent corals in shallow water

Partially bleached Acropora and Montipora corals

Most of the shallow water Acropora staghorn fields were badly bleached

Totally bleached Acropora plate coral on a large Porites bommie

This bleached Acropora colony is still brown tinged in places and may recover.

Parts of this Acropora staghorn colony are still brown and will probably survive

Large, partially bleached Sinularia soft coral

Tubinaria corals are usually resistant to bleaching but this large colony has been partially bleached

A variety of bleached corals in shallow water

Badly bleached encrusting Montipora coral colony

Most of the huge Goniopora colonies along the deeper parts of the reef slope were not bleached

More Bad News: Rattray Island Bleaching Impacts.

I’ve posted previously about the slow recovery of reefs on Rattray Island after being severely damaged by Cyclone Debbie. Recovery is still almost non-existent over three years after the cyclone and now the remaining corals have suffered a further setback with bad coral bleaching caused by the warm summer water temperatures. Most of the bleached corals are still surviving but some have partially died. The water temperatures have now dropped but are still 28°C. Those corals that are still alive may slowly recover but their health will be affected for some time to come.

Very few new corals are growing on the damaged reefs around Rattray Is.

Most of the damaged reef is still bare with only one or two new corals appearing after more than three years.

A single new Acropora coral is growing on this dead coral colony

A damaged Porites coral colony has now been badly bleached

This Porites colony was toppled and damaged by Cyclone Debbie and is now partially bleached

The huge Porites colony that was turned on its side by Debbie has fortunately only been slightly bleached

This Diploastrea colony has been partially bleached and is pale orange instead of dark brown

Most of the Millepora fire corals that were starting to regrow after the cyclone have been badly bleached

Another badly bleached Porites colony. These white colonies are still alive and may recover

Our New Drone: Useful Tool or Frivolous Toy?

We recently purchased a DJI Mavic 2 Pro drone to take images of our local environment. This is a small folding drone that has a 20 megapixel 1” sensor camera with a 28mm lens. It is remarkably capable and has a flight time of about 30 minutes on a full charge. I initially wondered whether it would be useful in our work and after 6 months of regular flying in our local Whitsunday region I’ve decided that it is actually quite a useful tool for marine surveys. Looking at aerial views of reefs gives a unique overview that can help with site selection for surveys. The drone can also be used to fly transects searching for megafauna such as manta rays, dolphins, dugongs and turtles. The long flight time means I can fly two 2000 x 50m transects on a charge, recording a video from a height of 50m that can be searched for target species. With three batteries I was able to record six 2 kilometre long megafauna transects in just a few hours. I’ve seen lots of turtles and one dugong so far! The drone can also be used to take aerials of the reef flat to count numbers of holothurians or to measure the extent of corals such as Porites micro-atolls.

So I’d have to conclude that this drone can be a useful tool for marine biological surveys as well as providing lots of fun!

Tony with the compact DJI Mavic 2 Pro drone

Fringing reefs in Hydeaway Bay

Gumbrell Island showing the extent and arrangement of the fringing reefs

Saddleback Island fringing reefs

Saddleback Island spit showing the rubble bank pushed up by Cyclone Debbie (pale tongue on left)

Middle Reef off Hydeaway Bay

Hydeaway Bay reef flat showing holothurians (black squiggles)

Large Porites corals on the Hydeaway reef flat

Dugong off the Hydeaway reef flat

Two turtles on the Hydeaway fringing reef

More Bad News on Cyclone Debbie Recovery

We recently dived in the bay on the north side of Rattray Island. This was previously another of our favoured dive sites but was badly damaged by Cyclone Debbie (see post from March 2018). Although it is now two years since the cyclone this reef is still devastated; some of the corals have suffered further mortality since the cyclone, succumbing to cyclone inflicted damage. This island is about 15km offshore with underwater visibility of between 5 and 15m but during our recent visit vis was less than 2m and there was lots of fine silt lying all over the bottom. We are at a loss to explain why there is so much silt here now and why the water was so dirty. Conditions were so bad that I couldn’t find the huge Porites bommie that had been turned on its side during the cyclone so I’m unable to report whether this has survived! Hopefully I’ll have better news on coral survival and recovery when next we visit this island.

Our boat is anchored in the bay on the north side of Rattray Island where the reef has not recovered at all from Cyclone Debbie damage

I have been amazed, both by the speed of recovery at some reef sites and by the slow recovery at others. So far I have not been able to figure out what is the major determinant of recovery time for badly damaged reefs where more than 90% of the corals have been destroyed.

Most of the reef still had no coral cover

Damaged corals still looked unhealthy

Fine silt covered much of the bottom

This is the only new coral recruit I saw

This damaged Porites still looked unhealthy

This is the same Porites colony 12 months ago: no recovery seems to have happened

An Amazing Reef: Fringing Reef Super-Site

We often dive on Saddleback Island, only a few kilometres from our home here in Hydeaway Bay, but have only once briefly visited the reef on the south side of the spit. Last week I did two long dives on this reef and was amazed at the healthy state of the fringing reef. It looks like the reef was only slightly damaged by Cyclone Debbie along the shallow reef edge and the reef slope coral is lush and healthy.

A drones-eye view of Saddleback Island fringing reefs showing South Spit Reef and the amazing super-site

On the shallow slope were huge stands of staghorn Acropora corals but the deeper slope, from about three down to eight metres depth, was dominated by continuous, undulating colonies of Goniopora. There were at least five different species of Goniopora but all mixed together into what looked like a single colony over 100 metres along the reef and 20-30 metres across. There were a mixture of other corals along the upper edge of the Goniopora stand and some soft corals but most of the slope was dominated by this single genus of coral. I have often seen large colonies of Goniopora on fringing reefs but this was much bigger than I have seen before and I didn’t explore it’s full extent. It always amazes me what we find when exploring coral reefs especially on fringing reefs that are often very turbid. The reefs on Saddleback Island often have less than two metres underwater visibility and only reach ten metres visibility very occasionally and yet they support wonderful coral reefs.

It is hard to convey the size of the coral colonies when the water vis is only about four metres but I’ve attached a few pictures here to give you some idea of this amazing fringing reef super-site.

Extensive staghorn Acropora colonies on the shallow slope

Huge Acropora valenciennesi colony on a shallow coral head

Several Acropora species formed huge colonies on the shallow slope

From about 3m depth Goniopora colonies dominated the slope

Undulating fields of Goniopora extended over 100m along the slope

Several different Goniopora species were growing together on the slope

There are five different species of Goniopora in this photo

Gorgonians and crinoids amongst the Goniopora

Closeup of the extended polyps of Goniopora coral

Soft corals and Pectinia corals along the upper edge of the Goniopora stand

A few large faviid coral colonies were also present

Colourful Scolymia australis on the lower edge of the reef

A few Fungia corals were present on the rare open patches of reef not covered by Acropora or Goniopora

Cyclone Debbie Recovery: the Good News and the Bad News

Over the past week we have dived on five local reefs to check out cyclone Debbie recovery. Most reefs in this northern Whitsunday region were badly damaged during the slow passage of Cyclone Debbie almost two years ago. Reefs on the South face of Gumbrell Island and on the north side of Saddleback Island previously had very high coral cover but had been devastated by the cyclone (see previous news item on March 2018). These reefs are only recovering very slowly, especially in shallow water where corals have been completely stripped off by the cyclone. These areas were covered in algae with only the occasional small coral colony appearing two years after the cyclone. North spit reef was still mostly devastated in deeper water as well, although there were a few corals starting to regrow in patches and a few new coral recruits. The deeper parts of Gumbrell Island, on the other hand, had started to recover, with many of the larger corals repairing themselves and surviving Acropora and Montipora coral fragments starting to grow rapidly.

The reef off the northern side of the Saddleback Island spit had been turned into a rubble bank by Cyclone Debbie and coral recovery has been very slow after two years.

Coral recovery on other reefs that were not completely devastated by Cyclone Debbie has been much more rapid. I’ve already reported that the reef in Bommie Bay on Saddleback has recovered rapidly and we confirmed that on this recent trip. It is now hard to tell that there has been a cyclone on this reef! Recovery has also been very rapid on Middle Reef, an isolated, long, narrow reef that is about 1,300 metres off Hydeaway Bay. This reef now has lush cover of Acropora staghorn corals and whorl-forming Montipora corals that have all regrown from fragments within two years. It appears that the reef on the south side of the Saddleback Island spit had only light cyclone damage on the shallow sections of the reef and this has almost completely recovered (I’ll be making another post on the condition of this amazing reef).

Algae still covers shallow sections of North Spit Reef

Macroalgae, including Sargassum, on North Spit Reef

A small coral colony growing amongst the algae

On deeper parts of North Spit Reef larger corals are dislodged and dead

A few larger corals have survived and are slowly regrowing

A few patches of this reef show regrowth of Acropora fragments

Shallow sections of Gumbrell Island reef were also covered in algae

Montipora in shallow water regrowing from small surviving fragments

On deeper parts of the Gumbrell Island reefs corals were recovering well

Large corals have survived and are recovering on Gumbrell Island

Large Pachyseris colony recovering on Gumbrell Island

Acropora thickets recovering on Gumbrell Island

Saddleback Island fringing reef positions

Healthy Acropora and Montipora corals on Middle Reef off Hydeaway Bay

Rich Acropora thickets on Middle Reef two years after Debbie

Montipora whorls on Middle Reef

Fast growing Acropora and Montipora corals on Middle Reef

Camp Island Again

We revisited Camp Island in November. This inshore island is just north of the Abbott Point coal terminal. The water was dirty around Bowen and around the coal terminal but just before we reached the island we got into blue water and vis was around 10m again. The reefs were very similar to when we surveyed them 6 months ago except that lots of Sargassum algae were tangled amongst the stag horn corals at one of the sites. These reefs are very shallow and waves often break or turn over corals even in ordinary rough weather.

One thrill during this visit was seeing a huge shovelnose ray. We don’t often encounter these unusual fishes, especially one about 2.5m long!

Large colony of Montipora digitata in shallow water at Camp Island

Rich patch of reef with diverse corals

Large colony of Goniopora coral

Large colonies of Pavona decussata are a feature of the Camp Island reefs

Galaxea coral colony amongst staghorn Acropora corals

Large stand of staghorn Acropora corals with feeding damselfish school

Some patches of the Camp Island reefs were covered with Sargassum algal forest

Large patch of disease on a Montipora coral colony

This Montipora colony has been turned over but is regrowing from the edges

Broken corals in shallow water on Camp Island

Sargassum algae tangled amongst staghorn Acropora corals

Siphonodictium sponges growing amongst corals

Giant shovelnose ray Rhinobatos typus

Return to Holbourne Island

We re-surveyed the reefs on Holbourne Island offshore from Bowen and the Abbott Point Coral Terminal recently. Cyclone Debbie had devastated the reefs around much of this island and we were looking forward to see how recovery was going. It had been 20 months since the cyclone tore these reefs apart and some of the broken and damaged corals were recovering well, especially the branching Millepora fire corals. There were also still some good corals on the deeper parts of the reef at about 10 metres depth and a few hardy corals in shallow water that had miraculously survived the cyclone. However, we were surprised to see that parts of the reef that had been stripped bare by the force of the cyclone waves did not yet have any new coral recruits on them. Normally we would expect to see many new recruits on such bare reef substratum within a year or so of the cyclone but nothing was visible.

The work was lightened by visits from several groups of large manta rays. One group of three mantas swimming nose to tail made about four visits over about 15 minutes, swooping close around us before going off about their business. It is always such a huge thrill to see manta rays when we are diving. As usual there were a few beautiful nudibranchs that temporarily distracted us from our work!

Meadow of bottlebrush Acropora corals that have survived the cyclone and recovered from mild damage at about 10m depth.

These Acropora corals were damaged by the cyclone but have recovered and are growing strongly

Staghorn Acropora and fire corals that have recovered since the cyclone

Many corals in shallow water died during the cyclone and have not recovered at all

No new corals are yet showing on devastated patches of reef

Blue-green algae growing on dead coral rubble

Fire coral or Millepora colony that has recovered quickly following the cyclone

This large Acropora coral colony miraculously survived the cyclone even though only in a few metres of water

Close approach from a large manta ray!

A beautiful Halgerda nudibranch