| Coral reefs, one of the most productive and diverse ecosystems on earth, not only protect adjacent costal areas from erosion, but also serve as an economical assess for human populations, providing as well a major source of protein to hundreds of million of people. Anthropogenic activities have greatly reduced the reefs' ability to cope with natural disturbances and have led to a severe degradation of this ecosystem during the past few decades. The failure of traditional acts have clarified that active restoration measures are now crucial to impede the reefs' further decline and to ensure the persistence of this habitat. With the aim of improving active restoration practices and overcoming disadvantages of the traditional methods, a new concept, "Gardening Coral Reefs", has been proposed. Inspired from silviculture, this concept consists of two steps: (1) generating and culturing of large pool of minute coral fragments or coral larvae in a coral nursery, (2) transplanting these colonies, when grown up, in degraded reef sites. In order to test the applicability of the Gardening concept the first step of the method was applied successfully in Eilat (Red Sea, Israel) and has resulted in the generation of a new coral stock for the purposes of restoration. This has permitted to initiate the second step of the method in Eilat. By transplanting 554 nursery-grown Stylophora pistillata and Pocillopora damicornis colonies onto five denuded knolls in Eilat's reef, we evaluate the feasibility of using nursery-grown coral colonies for coral transplantation. The transplantation act was divided into two major activities, in-nursery preparation of the transplants and transfer and attachment of the colonies at the study site. The preparation phase was carried out with the help of 13 volunteers and lasted one week. The transfer of the farmed corals to the restoration site and their attachment on the knolls by 5 SCUBA divers were completed within two weeks. Seventeen months of monitoring revealed that both species have the capacity to acclimate to the new environment in a degraded reef. The nursery phase prior to transplantation was successful in diminishing any initial stress to the transplants due to their transfer or to the transplantation act. P. damicornis transplants showed high adaptability to the harsh conditions at the natural habitat. Their survival, 77.8+/-2.9% after 17 months, did not differ significantly from naturally growing colonies. The proportion of colonies suffering from partial tissue death and the average magnitude of the tissue loss per colony were comparable with local colonies. The fish predation on P. damicornis transplants did not exceed that of the natural colonies. S. pistillata transplants showed lower performance than P. damicornis transplants once faced with the harsh conditions of the natural habitat. Their survival, 52.2+/-5.7% after 17 months, was significantly lower than that of the naturally-growing colonies. Partial tissue death was common for S. pistillata colonies at the restored site, though the average proportion of transplants suffering from this syndrome was higher than natural colonies as well as the magnitude of tissue loss per colony. During the first months after transplantation, the nursed S. pistillata colonies were heavily attacked by fish, attacks that decreased with time and became comparable to the control levels after 4 months. After 16 months at the natural reef, transplanted S. pistillata colonies had lower numbers of zooxanthellae per area unit than the nursery-control colonies. Total chlorophyll concentrations per zooxanthella cell, however, showed no change. In contrast to the naturally-growing colonies at the restored site, the S. pistillata transplants contributed to the local coral reproduction by liberating significant numbers of planula larvae. A 3 and 10 fold higher detachment was recorded during this study for S. pistillata and P. damicornis transplants respectively, in comparison to the natural controls. The growth rates of both transplanted species were not impacted by the transplantation act as they remained identical to the high growth rates of colonies kept at the coral nursery. Both species created new living space at the reef, ecological niches that were used by coral associated invertebrates. (Abstract shortened by UMI.)... |
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