UNDERWATER CORAL NURSERIES IN THE NORTHERN GULF OF EILAT/AQABA: A NOVEL APPROACH FOR CORAL REEF RESTORATION

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1 UNDERWATER CORAL NURSERIES IN THE NORTHERN GULF OF EILAT/AQABA: A NOVEL APPROACH FOR CORAL REEF RESTORATION B. Rinkevich and S. Shafir National Institute of Oceanography The coral reef in Eilat, northern Red Sea, was considered as one of the most diverse reefs in the world. Although difficult to quantify, this most intensively studied coral reef has been gradually degrading for nearly four decades. Of the 12 km Israeli coastline, the assigned Nature Reserve takes up ca. 3.5 km, of which 1.2 km are fenced and designated as a Coral Beach Reserve. Reef degradation in this part of the northern Red Sea reef system (resulting from heedless development of the city of Eilat, intermittent municipal sewage outflow, industrial installations, tourist activities and others) has been in the scientific spotlight for about 40 years, led by studies that evaluated independently impacts of human activities as well as impacts of natural catastrophes on reef coral assemblages. Reef degradation in Eilat is probably further enhanced by globally related phenomena. In addition, it is also possible that the failure of corals to recover in denuded reef areas in Eilat is due to post-settlement mortality, unrelated to water pollution and to long term and permanent changes in substrate conditions. Management policies used in the coral reef at Eilat, even those management schemes aiming at the ecological sustainability of tourism (such as the no-use zone act), have proved to be ineffective in ameliorating long-term impairments. The traditional conservation approaches carry, therefore, default merits as sustainable tools for this reef management. As traditional management approaches have failed to cope with Eilat reef degradation the reef reached the point (sensu several local scientists) where efforts should be concentrated, less on how to conserve remnants of previous reef populations, or how to prevent further habitat degradation (although these acts are of great importance and should not be ignored), and rather be actively engaged in how to restore and consolidate reef communities, using current state of reef health as the background level. Eilat s reef is not a unique case. The phenomenon of coral reefs decline worldwide has raised the need for urgent development of adequate restoration methodologies. The act of restoration has also been drawing increasing attention because, as in Eilat, most efforts to conserve degrading reefs have failed to yield significant results, and traditional rehabilitation measures did not successfully compensate for the fast decline. However, restoration efforts of the coral reefs were characterized by the lack of state-of-the-art remediation protocols, e.g., established theories and approved restoration techniques specifically developed for the marine environment. As a result, the principles underlined past remediation measures in the reef became part of the many ill-defined issues of reef biology. It is also evident that restoring any type of degraded reef area is a complex biological and ecological procedure. Furthermore, until recently most studies on coral reef restoration have been based on small-scale, short-term experimental protocols, testing only some ecological/biological attributes. In spite of these difficulties, during the last decade, worldwide coral reef restoration operations have been more frequently employed and tested in various reef localities, and the concept of active restoration has been acknowledged as an important approach for reef rehabilitation. 1

2 One of the most commonly used methodologies for restoration is direct transplantation of coral material (whole colonies, fragments, nubbins). However, while the techniques used for removal of coral material, their transportation and reattachment are straightforward and smilingly simple, varying degrees of success that have been reported revealed significant limitations of the direct transplantation methodology. This stems from the development of stress in the transplanted coral material, the use of insufficient donor colonies and/or too small fragments and the disturbances inflicted on the donor coral populations. In other cases, the failure of corals to recover denuded reef areas also reflects post settlement mortalities To alleviate these problems, we suggested, a decade ago, the strategy of gardening coral reefs, a two-step restoration protocol which central concept is the mariculture of coral recruits (spats, nubbins, coral fragments and small coral colonies) in nurseries. Instead of direct transplantation measure, at first, large in situ (in the field) pools of farmed corals and spats are constructed. In situ nurseries are installed in sheltered zones, where the different types of coral recruits are maricultured there to the adequate sizes for transplantation. This practice also helps in using minute size coral fragments that otherwise would die when directly transplanted. In the second step, nursery-grown coral colonies are transplanted to degraded reef sites. This approach is theoretically associated with ideas of silvics and silviculture. The above suggestion was already tested by several scientists, in different localities worldwide and revealed promising outcomes. However, up to date, most in situ coral nurseries were developed in reef areas at or near sea bottom in shallow water Following preliminary studies, we recently further developed a novel approach for in situ coral nursery, which is based on the establishment of large mid-water nursery in a protected site, away from major natural reef areas. This floating nursery, situated away from impacts inflicted to the reefs by tourist's activities and by corallivorous organisms, showed to be superior to all former approaches. The mid-water floating nursery was established at a depth of 6 m (14 m above the sea bottom). The nursery was situated at the Ardag fish farm facility, located at the northern shore of the Gulf of Eilat, Red Sea (29º32.45 N, 34º58.40 E). The nursery consisted of a flexible rope net (10X10 meter size, 100 cm 2 hole size, Figs. 1,2) tied to cables, anchoring a large fish cage (containing gilthead seabream, Sparus aurata). Ramets from coral branching forms were pruned to small size fragments (0.5-2 cm high) and nubbins by the use of an electrician s wire cutter. Old and recently developed parts of each colony as well as tip and mid-branch zones were used as source material for fragment preparation. Coral colonies from 11 branching species were completely fragmented into small ramets. In addition, 21 small colonies (< 5 cm diameter) of the massive coral Favia favus were transplanted to the nursery. All colonies and colony fragments were collected from artificial substrates at the northern part of the Gulf and transported, submerged in seawater, to the nursery site. Favia colonies were glued, one colony per plastic pin, without any experimental manipulation. In attempt to minimize stress conditions, the isolated fragments of the branching species were instantaneously immersed upon separation in a tank of fresh seawater. Then, the exposed skeletal surface area of each individual fragment was dried with a paper towel and the ramet was glued with a drop of cyanoacrylate glue (Super Glue) to the flat surface of a plastic pin (9 cm long, cm wide leg with a 2 cm diameter "head, Fig. 3). After less then 1 min exposure to air the glued fragment was immersed in fresh seawater. Whole Favia colonies were glued directly to the pins without fragmentation. The plastic pins carrying the glued coral ramets and colonies were positioned within plastic nets (0.25 cm 2 mesh size) that were stretched over PVC 2

3 frames (each 50X30 cm). Frames with the pins were tied to the rope net (Fig. 2). Each plastic frame carried pins with coral ramets or colonies. In the nursery, almost 8000 coral fragments and colonies, positioned on ca. 80 plastic frames, were maricultured. The prototype mid-water, floating coral nursery studied here, provides improved environmental conditions for colonies when compared to more common sea floor nurseries as minimal (less than 10%) mortality was recorded. Many fragments grew very fast, forming large colonies to the size of 8-10 cm in diameter (Figs. 4-10) while others reached the size of 15 cm in diameter and more within about only 13 months (Fig. 10). The Favia colonies (Fig.8) showed an exceeding growth rates, never recorded in their natal sites (160% increase in size within 9 months). Recently we started to use the maturing colonies as a source material for the development of additional fragments. Specimens of various invertebrate species, originating from the plankton, settled on the new coral colonies and on the plastic frames. A number of characteristics can be identified when comparing floating nurseries with bottom nurseries: 1. Water flow: supplies the mid-water nursery system with large quantities of plankton particles, probably enhances the dissolved oxygen flow around the coral tissue and helps in removing mucus secreted by the coral tissue in a more efficient way; 2. Movement of the nursery: in sea bottom nurseries attached to the reef floor, water movement around the corals results strictly from currents or wave actions. In a mid-water floating nursery, the complete nursery moves in the seawater column to all directions. This flexibility enables the nursery to further increase water exchange around the corals tissue and promotes a better elimination of debris, sedimentation particles and other settling material that might accumulate on developing coral colonies; 3. Sedimentation: one of the obstacles of raising coral colonies at attached to the substrate nurseries is the detrimental effects of sedimentation of the corals that may negatively influenced the health and growth of corals. In the current mid-water nursery, the sea floor was 14 m down so that sedimentation was significantly reduced; 4. Photosynthesis activities: mid-water nurseries can be depth adjusted according to the needs of each specific coral species. For example, frames with Millepora colonies (Fig. 4) that thrive in shallow depths (more light, more water movement) can be placed in the floating nursery at shallower depths (1-3 m) while other species may thrive at deeper depths. The flexibility of the mid-water nursery enables a gradual adjustment to irradiation conditions similar to those at the final transplantation site; 5. Reduction in coral predators and other stressors: shallow water sea bottom nurseries are usually situated near natural reefs. This exposes them to corallivorous fish and invertebrates as well as to divers' impacts in tourist areas. Installing the nursery at a distance from the reef may reduce harmful impacts of predators and recreational activities. However it will not protect from corallivorous invertebrates in the plankton, such as the snail Drupella cornus. In summary, mid-water coral nursery is an improved nursery type dedicated for the mariculturing of coral colonies. As in the development of silviculture methodologies, active restoration of denuded coral reefs requires the development of specific techniques and protocols. This study describes the first simple prototype of floating, mid-water coral nursery and the feasibility of culturing thousands of new coral colonies amenable for transplantation back into the reef. Although there are still many unknowns (e.g., multi-layer nursery, optimal nursery time and seasonality, optimal fragments size, number of ramets per genet, active maintenance), it is evident that the ability to produce and develop numerous coral colonies by means of this method may change the way end-users manage denuded reef areas. 3

4 The next step in the research will be the evaluations of the second phase in the gardening concept- the transplantation of nursery grown coral colonies into denuded reef areas and the closed long term follow up study of their fate under real reef conditions. Furthermore, this prototype coral nursery is now established and tested in additional reef sites worldwide (Bolinao, the Philippines; Phuket, Thailand; Singapore; Jamaica- supported by grants from the World Bank, the European Community and the USA-AID programs) for the development of ubiquitous restoration protocols. Fig. 1. General view of the coral nursery Fig. 2. Transposition of trays of coral colonies in the nursery Fig. 3 (right). Coral fragments placed at the nursery. Fig. 4 (left): A colony of Millepora developed from a small fragment place at the nursery 4

5 Fig. 5. Dense growth of coral colonies at the nursery. Fig. 6. Colonies of Acropora that grew in the nursery for a year and a half (from 1 2 cm fragments to colonies with ca. 15 cm diameter). 5

6 Fig. 7. Colonies of Stylophora developed at the nursery from small fragments. Fig. 8. Colonies of Favia developed at the nursery. 6

7 Fig. 9. A tray of Pocillopora colonies showing the fast growth rate at the nursery. Fig. 10. Growth of an Acropora colony in the nursery in 400 days (length of the white line at the top is 2 cm). 7