[Coral-List] Coral reefs could be restored with rope nursery 'gardening' methods

[Artur Gil]

Coral reefs could be restored with rope nursery 'gardening' methods 
 	1. This study was supported by the European Commission under the INCO-DEV (International Cooperation with Developing Countries) programme. For more information on the EU's activities in international scientific cooperation, see: http://ec.europa.eu/research/iscp/index.cfm 
Source: Levy, G., Shaish, L., Haim, A., Rinkevich, B. (2010). Mid-water rope nursery -Testing design and performance of a novel reef restoration instrument. Ecological Engineering. 36: 560-569.
Contact: gidi.levi at gmail.com and buki at ocean.org..il 
Theme(s):Marine ecosystems 
 
Using 'gardening' techniques to actively restore endangered coral reefs is ecologically sound and economically feasible, according to recent research.
Coral reefs have been called the rainforests of the oceans and are home to an exceptionally diverse range of living organisms. In addition, coral reefs around the world provide a living for hundreds of millions of people through fishing and tourism. However, coral reefs are being damaged by destructive human practices, pollution and natural disasters, and in many cases have little prospect of recovery.
Traditional restoration of coral reefs has primarily used transplanted fragments of coral or entire coral colonies from nearby reefs. However, this potentially causes stress to the source reef, making this an ecologically unsound practice, and it has been found that the transplanted coral does not always survive the stress of being moved.
This study, partly conducted under the EU's INCO-DEV programme1, sought to overcome these problems and reduce the costs of traditional methods by using the 'gardening concept'.. This approach adapts the techniques of silviculture, or the restoration of forests on land, through the controlled establishment, composition and growth of forests. The 'gardening concept' is a two-phase process. In the first phase, large numbers of coral fragments are cultured in underwater nurseries, and in the second phase, the farmed coral is transplanted onto damaged reef areas.
In this study, conducted off the north-western Philippine coast, the researchers tested the design and performance of different prototypes of 'rope nurseries', a type of underwater nursery constructed from pieces of rope. Two mid-water designs, the 'floating rope nursery' which had ropes floating loosely under surface buoys, and the 'tied to bottom' nursery, which had ropes attached to cables stretched between anchors and buoys were used to assess suitable depths, types of coral and construction practicalities. Lessons learnt from these prototypes were used to design a larger 'fixed to bottom' rope nursery.
In all of the nurseries, small fragments of coral, each about 2-4cm long, were inserted into the coils of the rope without the use of adhesives. Four species of coral were tested in total in the three designs of rope nurseries. The rope assemblies were easily constructed and inserting the coral fragments was simple and fast, with the fragments successfully developing into grown colonies.
Compared with previous types of coral nurseries, survival rates of coral in the rope nurseries were high, detachment of the coral fragments was low and the growth rate was fast. For example, in the 'fixed to bottom' design, over 95 per cent of the two branching species survived. Survival rates of the two leaf-like species were lower, due to the small size of the fragments and the relatively large area of contact between the rope and coral. Using larger fragment sizes should improve these results.
The relatively large design, 'fixed to bottom', holding 1200 pieces of coral, was very economical, costing just US$0.11 (€0.08) per coral fragment, including material and labour. Other advantages of this method include the absence of adhesives to hold the coral fragments in place and the low-tech nature of the process and materials, making the construction of large rope nurseries feasible in remote areas with limited finances.