Abstract Summary
The fringing reefs of the Andaman Islands have, in the recent past, been subject to overfishing, siltation, and El-Nino related mass bleaching events. Reefs here have been in decline with reports showing decreasing live coral cover from 80% in 1998 to 41.9% in 2011. The project started in November 2016, as a combination of structural and biological restoration, 2 structures made of iron rebar were sunk into the water adjacent to a reef with low structural diversity. Naturally broken coral fragments (due to boat, anchor, storm or fish damage) were then collected from the adjoining reef area and transplanted onto these structures, with care taken to maintain the depth range from which they were collected. During the first year of the project we tested different materials to determine what method worked best for coral attachment. Polyurethane cableties were more effective than nylon or cotton based threads. Additionally, species of corals were not differentiated from, with fragments of all species found being collected. The structures were then left underwater for the monsoon period – July to October, when the sea is the most rough – to see how well they withstood turbulence. In the post monsoon monitoring we found that corals on one structure had survived better than on the other due to structure design differences. We concluded that for a coral fragment to be stable enough to grow around the metal structure, a grid is required, without which the fragment slides down the iron rods. 2 more structures were designed and sunk at the site correcting for this error, this time increasing the range area of coral fragment collection, thus diversifying the genetic pool on the structures. In 2018, we collaborated with Coral Aid to connect all 4 structures to mineral accretion devices. The difference in these devices to traditional ones connected to a local power grid is the source of electricity comes from 2 6-volt solar panels floating on the surface above the structures. The addition of this device has visually shown an increased growth rate in coral fragments. However, we are yet to quantify its value.
