|Yule Reef, with Captain Cook Highway visible at Yule Point in lower right (Photo 1996, Beach Protection Authority)|
|One of the channels between old coral platforms (July 2012) - click to zoom in|
|Closer to the reef edge there is respectable coral in the channels (June 2009)|
|Another coral view in a channel at Pretty Beach (about 50 m off the beach and 3 km further south)|
|Dense soft corals at the head of the shallow channel where people enter the reef from the sand flats (July 2009)|
|Coral platforms that appear as a dark fringe near the seaward edge of the reef on the aerial photo.|
Now I use a GPS (Garmin 64s) and an underwater camera and on my last day trip to the area, captured almost 700 photos. Geotagging software is used to geotag the photos with the GPS trail, which results in a better than 3 m geographic precision. In-camera GPS units are far inferior to hand held GPS units so I overwrite any coordinates recorded by the camera. Now, I have a record that rivals the environmental monitoring undertaken by some scientific organisations.
Starting with my old memories from the time before the first coral bleaching in 1998, the reef edge near the mouth of the Mowbray River was a slightly threatening place. Swells would swash between exposed dark brown living heads of coral that rose up approximately a metre from the bottom and stood more than half a metre exposed between waves. These coral heads, which were shaped like tiny mountain peaks formed an irregular row with roughly 10 m spacings. With care I could navigate around them with my 12 foot boat and motor. The heads of living coral may in part be maintained by the splash of waves allowing the coral to grow taller than water levels usually permit. I wonder if these tall raised coral colonies are still a feature of today’s reef.
|A coral head on Little Reef, which is near Yule Reef (June 2009)|
|Typical underwater view on Wentworth Reef (August 2013)|
|A tiny patch of continuous coral cover showing how there is no space between colonies (July 2012)|
I have looked for mono-culture brown reef a few times since the 1998 coral bleaching but finding even large reefs that are close to shore can be difficult. On a day with a mirror-like surface I once failed to find a reef that was less than 1000 m from shore, even though I briefly saw the reef under my boat, the reflective surface defeated my attempts to relocate the reef and the next day, I bought my first GPS out of frustration. When I searched Alexandra reef for the live coral surface, I found a thick forest of Sargassum which was over 2 m tall. There was almost no live coral below the sargassum, just an irregular dead coral surface covered with a film of mud. Very small massive corals were here and there and I put the survival of these corals down to being on vertical surfaces which resist the settlement of sediment. Now with aerial photography, I have located a small, slightly deeper reef just the east of Alexandra Reef, I need to check that reef as it may be the reef with the living coral surface I once observed.
|Sargassum dominates the shallows between the coral platforms near the reef edge and the green seagrass beds on the landward margin of the reef|
|Sargassum laying down in a shallow lagoon at low tide (April 2016)|
|Did this coral survive due to its wig of Sargassum?|
|After Cyclone Yasi destroy feeding grounds, many exhausted Green Turtles would beach when the tide retreated (July 2012)|
Well before the event, the 2016 coral bleaching was predicted. Satellites had identified a vast pool of hot water in the eastern pacific ocean and from past experience, it was known that this pool of water would stream across the pacific to affect the Great Barrier Reef. The 2015-6 wet season was poor and the skies often crystal clear. On kayaking my wet hands would be cooled by the breeze but when they dipped into the water, the water was as hot as bath and beyond anything I had experienced. I heard from others that Yule Reef had gone white so I missed the onset of the event and perhaps have only captured the tail end.
On walking out onto the reef flat, the most obvious change were large patches of white coral. White coral is dying coral which will either die or if conditions suddenly change for the better, recover.
|One of the first corals I saw was completely bleached with more exposed parts already dead|
|In April 2016, Yule Reef was dominated by patches of stark white in a brown Sargassum matrix|
|The stark white corals are eye-catching however a second view shows than some corals were not bleached|
|Living coral grew like a lawn up to the upper limit of growth (July 2012)|
|A close up of the coral lawn showing two species of branching coral|
|The coral is still standing but is dead|
|A close-up view shows brown slime rather than star shaped coral polyps|
|Corals in areas with better water flow survived at a least in part|
|Stressed massive corals were an abnormal pink colour|
|Same species of coral bleached to a florescent light green shade|