Mapping the Capricorn-Bunker reefs on the Great Barrier Reef

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Doing ground truthing surveys with the underwater camera (photo credit: Matt Smith)

After 150 nautical miles, 42 high tides, 17 coral reefs, 14 islands and three stuck anchors, I have just returned from the Capricorn Bunker Group at the southern end of the Great Barrier Reef.

I was leading the Joint Benthic Field and Remote Sensing Survey, a collaboration with the University of Sydney and University of Queensland to accurately map this group of islands and associated reef platforms using satellite imagery.

We visited >1500 sites across 20 islands from the 40-foot Velella catamaran to carry out ‘ground truthing’ surveys to support the mapping, which included revisiting 1407 sites that were surveyed in 2002 to ascertain whether changes were apparent in the seafloor communities.

You can get the lowdown on what we were doing at this documentary made by Matt Smith here: 

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The Velella catamaran used for the Capricorn Bunker fieldtrip (photo credit: Matt Smith)

This was no sailing holiday. Relaxation was replaced by a sort of sixth sense, a constant alertness to our surroundings and an unrelenting voice in my head asking, “What are the processes at work here? Can we model them? How do they fit with what we already know and what we have set out to accomplish?”.

Conditions weren’t ideal for my first big leadership role. At times I felt like mother hen, keeping a close eye on what the team were up to and asking myself why my risk assessment hadn’t anticipated duck-diving down to 10m to unwedge the anchor on the exposed side of the reef, several miles from the catamaran, with sunset fast approaching.

Accurately locating repeat survey sites sometimes proved a challenge from a six-foot dingy in swells of around 2m. My back ached from bending over as I barked orders to various field assistants with my head deep in equipment, squinting at laptop screens while also trying to drive the boat to the correct location.

The physical graft of sailing between sites each day was tiring, but it was lovely to see the sun rise and set, work to the rhythm of the tides and feel a sense of accomplishment upon completing a different site.

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Skippering the Vellela catamaran (photo credit: Matt Smith)

In spite of getting off to a slow start (six days marooned at Lady Musgrave Island, with two broken engines and 25-knot winds), morale stayed high and we were able to complete all the major tasks that were planned, becoming fairly proficient sailors along the way (well, our skipper Russell seemed to think that our rope work has improved – which may just indicate that it was ropey to begin with).

All in all, I am happy to chalk up this trip as a rousing success. This unique survey represents the largest high-resolution satellite mapping campaign undertaken to characterise the seafloor on the Great Barrier Reef.

It will enable a realistic estimate of regional scale calcification to be obtained for 100> km2shallow water reef. Such valuable information underpins environmental management of the Great Barrier Reef, enabling analysis to be undertaken at a scale that represents a realistic way forward for breaking down and further understanding the key functions of calcification across its >2000km length.

 

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