Coral reef restoration
Started on February 10, 2017
Start: April 2016
The pilot study that had been performed from August till December 2015 showed that it is feasible to have a coral reef restoration project in the Shimoni area. The corals that were used (Porites cylindrica, Acropora aff. formosa, Pocillopora aff. verrucosa and hydrozoan Millepora aff. tenera) showed good growth in all three nursery designs (Table, Floater and Tree) and only small differences between two nursery locations were found. It is important to continue monitoring these nursery structures to evaluate the efficiency of the nursery structures for the growth of corals over longer periods of time. In April 2016, another master student from Wageningen University (Rianne Laan) travelled to Shimoni to continue monitoring the growth of the corals and to investigate the possible use of bottle reefs as an artificial reef.
The Floater nursery design appeared to be non-durable. Either the Floater floated away and got lost or the structure was breaking down due to the continuous forces of waves and current acting upon it. Thus it was decided to keep only the Table and Tree nursery designs. For the nursery location in Kisite Marine Park insufficient data could be collected, but in Wasini Channel no clear differences were found in coral growth between the Table and Tree nursery structures. Combined with its low costs, easy construction and durability, it was therefore decided that the Tree design was the preferred design to expand the nurseries in the Wasini Channel.
When the corals have grown sufficiently large, they can be outplanted on degraded reef patches or on artificial reefs. REEFolution developed bottle reefs, consisting of a concrete base in which 16 empty wine bottles are standing. These bottle reef units serve as an inert substrate to form an artificial reef and coral fragments can be placed in the openings of the bottles to give them a solid base. Nearly 70 percent of the coral fragments that were placed in the bottle openings fell out, showing that a strong fixation of the coral fragment in the bottle is very important for a practical use of the bottle reefs. The fragments that remained stuck in the bottles performed well. Although the actual growth of the corals was less compared to the growth observed in the nursery structures, 80% of the fragments showed growth over and attachment to the surface of the bottle, indicating that the coral can indeed use the bottle as a substrate to grow on. The depth at which the bottle reefs were placed seemed to influence the growth and success of the coral fragments. Coral fragments in the shallow placed bottle reefs (<6 meters) seemed to perform better than the deeper bottle reefs (>6 meters), both in terms of loss and growth, indicating less optimal conditions at the deeper bottle reefs compared to the shallow bottle reefs. However, also at the deeper bottle reefs, growth and attachment to the bottle surface was observed. When a solution is found to fixate the coral fragments properly in the bottles, the use of bottle reefs to create an artificial reef seems to be promising.
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