Pom Pom Island has a steep slope from the reef crest to the deep water dropoff at a depth of around 50m. All this slope has been seriously blasted in the past by bomb fishermen. All that is left of the original reef are the rubble fragments on a seriously sloping reef. The reef conservation efforts of TRACC volunteers has increased the biodiversity but the structures are difficult to stabilise.
The TRACC reef conservation for 2015 was generally excellent with amazing successes. Our coral growth techniques which work well on flat areas of seabed (Bottle & Ribbon reefs) were modified to create step reefs aimed to create small reefs on the steep slopes. These look great initially but too many of them are unstable and deteriorate rapidly. While the corals grow and the fish live on the step reefs we create, unfortunately the slope continues to win and changes all the reefs we create. A beautiful series of steps fixed solidly to the seabed, becomes a tumbled mess after turtles scratch and fish dig.
We have tried spikes into the seabed to hold the structure in place but the rubble flows down from above and covers the steps. We have tried interlocking the steps and the whole structure moves down the slope as a unit. We have tried creating curved amphitheatres but after 12 months the structure looks like an ancient roman ruin.
After much trial and error, we are gradually refining a coral rubble reef conservation system which seems to be stable. We are stabilising the rubble with soft coral nets which slows the rubble movement and the turtles do not destroy. We are then creating Basket reefs which are more stable than the step reefs and have not yet been tumbled by the turtles. The Basket reefs attract a lot of small fish and are stable enough to remain in place for the long time that it takes to grow hard corals.
Lots of our reef conservation for 2015 techniques work well, hopefully by the end of 2016, we will have also found the best system to stabilise steep rubble slopes. Wish us luck 🙂
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