Increasing coral cover in rubble using nursery ropes
Coral reef restoration projects often have the challenge of needing to grow coral on an area that has become dead rubble. These rubble fields usually do not recover naturally, but rather expand and erode neighbouring areas of healthy coral because the broken coral skeletons are unstable and move around in currents. Any attempts for young corals to try to establish themselves in these areas are unsuccessful - as the small corals quickly become smothered and buried in the rubble.
Using Active Coral Restoration Methods
In our restoration project we are using a few different methods to try to stabilize the rubble substrate in order to allow natural settlement of corals. As well as using low-lying structures to transplant corals upon above the rubble.
In an attempt to increase the amount of hard coral coverage across the rubble, we tested a new technique one year ago. We used mature ropes from our nursery (8 months old) in which the attached corals had grown to about football-sized. With these ropes we pinned them along the bottom across areas of rubble (between some of our coral-frames).
Improving Techniques for Increasing Coral Cover
After one year, our trial plot using this technique showed decent results. Although the colonies had only about 50% survivorship, the rope had acted as a barrier for rubble erosion and allowed for natural settlement of new corals. This technique had promising results, as long as we were able to improve the survivorship of the corals upon the ropes. We attributed the relatively low coral survivorship to the constant moving action of the coral colonies across rubble. To improve this technique we started using shorter ropes so that the span between anchors was not as far. In March 2020 we anchored several more mature nursery ropes out across the rubble, so we hope after a few months we can see some growth and stabilization - which will increase the coral coverage at the site.
