ABSTRACT

The majority of reef corals, as well as other reef-dwelling cnidarians, are inhabited by symbiotic dinoflagellates of the genus Symbiodinium (Muscatine 1990)� The gorgonian soft corals (Isis) also have Symbiodinium in their tissue (Fabricius and Alderslade 2001)� The dependence of the coral animals upon the photosynthetic activities of endosymbiotic Symbiodinium living within their endodermis tissue (Barnes and Chalker 1990) restricts the distribution of these coral animals to sunlit waters (Veron 1993)� The photobionts supply nutrients to their hosts, which allow them to colonize habitats they normally could not because of limited supplies of food (Paracer and Ahmadjian 2000)�

Gorgonian soft corals, Isis (Isididae), are relatively new to the list of reared marine species under controlled environment� The present work focuses on the enhancement of growth and survival of gorgonians in raceway tanks by comparing the growth in electrical fields and uncharged controls�

Isis hippuris has been exploited to the extent of a thousand tons from the reefs of the Eastern Indonesia Archipelagos for their skeletal materials, which have been exported to Singapore, Malaysia, and Hong Kong�

Highly bioactive compounds have been extracted from I. hippuris known as “hippuristanol�” The kind of Isis grown contains Hippuristerone A, polyoxygenated steroids, hippuristerones J-L,

CONTENTS

Introduction ������������������������������������������������������������������������������������������������������������������������������������ 105 Materials and Methods ������������������������������������������������������������������������������������������������������������������ 106

Biorock Design and Setting ������������������������������������������������������������������������������������������������������ 106 Maintenance of Animals ����������������������������������������������������������������������������������������������������������� 106 Growth and Survival ����������������������������������������������������������������������������������������������������������������� 107 Physical Parameters ������������������������������������������������������������������������������������������������������������������ 107

Results �������������������������������������������������������������������������������������������������������������������������������������������� 108 Discussion �������������������������������������������������������������������������������������������������������������������������������������� 109 Conclusion �������������������������������������������������������������������������������������������������������������������������������������� 110 Acknowledgments �������������������������������������������������������������������������������������������������������������������������� 110 References �������������������������������������������������������������������������������������������������������������������������������������� 110

and hippuristerols E-F (Chao et al� 2005; Sheu et al� 2000)� Their medical applications have been found to exhibit antitiviral activity (Chen et al� 2011)�

They would appear to have great potential for mariculture and to be well suited for restoration of depleted reefs� The purpose of this study is to document the changes in growth and survival of the gorgonian, I. hippuris, in electrical fields�

MATERIALS AND METHODS

Biorock Design and Setting

The Biorock design and setting are illustrated in Figure 9�1a� The cathode compartments consisted of three trapezoidal structures constructed from steel bars (8 mm diameter) and a plate iron (3 mm thick) as frame� Chicken-wire mesh of 4 cm mesh size and rectangular cement plates were attached (alternately) to both sides of structures� Each trapezoid length was 2 m, base width 0�85 m, and height 0�50 m with 45° side slope� The cathodes were placed in flow-through concrete raceway tanks (8 × 1�5 × 1�2 m)� Anodes were made of coated titanium wire meshes and were installed inside the outlet polyvinyl pipe (size 2 in� diameter and 0� 95 m long)� The anode pipes were inserted into the outflow polyvinyl pipe (size 3 in� diameter and 1 m long)� A DC power supply (RTVC, Volta Electronic) was placed on the upper supporting woods of building above the Biorock tank� An electric current of 5 V and 5 A was applied for about 12 hours during the day� At night, the electric current was turned off� Biorock design and construction was advised by T� J� Goreau�

Maintenance of Animals

These experiments were conducted at Barrang Lompo Island Marine Field Station of Hasanuddin University, Makassar, South Sulawesi, Indonesia� Three colonies of the gorgonian (I. hippuris) were collected from their natural habitats, at a depth of 6 m on the reef of Bonetambung, western Barrang Lompo Island, and transported in containers of seawater to the islands of Barrang Lompo� These colonies were growing in close proximity and all appeared to be of the same phenotype (Figure 9�2)� All were kept in running seawater raceways (~1 m deep) for 1 week before being used in experiments� Only healthy-looking colonies with normal polyps expanded were used by carefully cutting the branch (approximately 6-7 cm in length) with a sterile stainless scissor and then attaching it directly to the artificial substrate� All of the transplantation processes were done underwater to

prevent stress to the animals, because the gorgonians must be carefully handled� As it is very sensitive to handling� Height measurements were made only at the start of 8 weeks, to minimize handling stress� A total of 40 nubbins were placed on the cathode wire mesh and on the control uncharged wire-mesh structure� Two concrete raceway tanks (8 × 1�5 × 1�2 m) were used for this experiment� Sunlight transmission was reduced to about 85% under a translucent fiberglass roof canopy� The flow-through system was used with the flow rate of about 60 L/min� Water overflowed from inlet PVC pipe by gravity into the experimental tanks, with water height maintained with a moveable outlet PVC pipe for the outflow� Aeration was provided inside the experiment tanks� A vernier caliper (0�05 mm) was used to measure gorgonian body lengths, and the measurement was held underwater� A light meter (Lutron LX101) and thermometer were used to measure light intensity and temperatures during the experiment�

Growth and Survival

All of the gorgonian lengths were measured at the start and the end of the experiments� Survival was recorded at weeks two, four, six, and eight by determining the proportion of live and dead animals from a total of 40 animals� Growth increments were analyzed using t-test, with the probability of type 1 error set at p = 0�05�

Physical Parameters

Temperatures were recorded every two weeks with thermometers in two concrete raceways tanks� Light readings (lux) were taken every two weeks, around midday, in two concrete raceways tanks at the surface of seawater�

RESULTS

Growth of gorgonians in Biorock and control tanks are shown in Table 9�1 and Figure 9�3� The growth increment of gorgonians in Biorock and control tanks were 0�59 cm and 0�25 cm, respectively� Growth of gorgonians on Biorock was significantly (t-test, p < �01) higher than controls, with the growth on Biorock 2�68 times higher than control�

Survival of the gorgonians in Biorock and control tanks are given in Table 9�2 and mortality in Figure 9�4� The mortality in the control tank was 1�88 times higher than in the Biorock tank after the end of the experiment� Mortality in the Biorock tank was slightly higher than controls at week two, but at weeks four, six, and eight consistently higher in the control tank compared to the Biorock gorgonians� The Biorock gorgonian mortality stopped after six weeks, but controls continued to die�

Light intensity values are given in Figure 9�5� Light intensity ranged from 8,000 to 20,000 lux both in Biorock and in control tank from October to December (rainy season)� The temperatures in Biorock and control tank ranged from 26 to 30�5°C and 26-29�5°C, respectively, over the experiment, with temperatures in Biorock slightly higher than control tank (Figure 9�6)�

DISCUSSION

These differences in growth and survival of the gorgonians correlated with and may be attributed to the electric-field effects from the Biorock process� Goreau and Hilbertz (Chapter 4) stated that average hard-coral growth on Biorock structures is faster than controls�

The Biorock process increases calcification by providing alkalinity for skeletal growth and metabolic energy for proton and calcium pumping, growth, reproduction, and resisting environmental stresses (Goreau et al� 2004; Goreau and Hilbertz, unpublished data)� Soft corals, including

gorgonians (Isis, Rumphella, and Anthogorgia) grew on Biorock with normal appearance, but with faster basal growth and more new budding (branches)�

It is difficult to isolate the importance of any single factor in the ecophysiology of corals (Falkowski et al� 1990)� The variation in size and shape between colonies of I. hippuris from different environments and geographic regions is very large (Fabricius and Alderslade 2001)�

Although temperatures were slightly higher in the Biorock tank than the controls, both showed a normal polyp extension, but polyp color was darker on Biorock compared to controls� High temperatures could cause Symbiodinium expulsion from the coral hosts, and then corals become bleached (Tomascik et al� 1997)� Corals on Biorock nurseries in the sea bleached, but had 16-50 times greater survival after severe bleaching (Goreau et al� 2000)�

Tissues from two dead corals prior to falling off the skeletons from Biorock and control structures were examined under a microscope� Pale-colored Symbiodinium were still intact in the host, but Symbiodinium became smaller as if cysts developed and were not normal yellow-brown in appearance� Rachman and Fitri (2011) found that Symbiodinium isolated from I� hippuris showed a normal germination and grew when recultured under laboratory condition after being stressed with extreme temperatures (0 and 80°C)�

CONCLUSION

The electrical fields from Biorock lead to 2�68 times increased gorgonian soft-coral growth compared to controls in the raceway tank conditions� The controls had 1�88 times higher mortality than electrified corals� These results suggest that Biorock will result in superior growth and survival for mariculture of these species� Based on the pilot project results reported here, more detailed work is currently under way to find the optimum conditions for I. hippuris and other species�

ACKNOWLEDGMENTS

We especially thank Dr� Tom Goreau for kind support with experimental setup and editing this chapter; Dr� Noel Janetski, Dr� Sven Blankenhorn (Mars Symbioscience), and Dr� Idrus Patturusi (Rector of Hasanuddin University) for facilitating this experiment; and all the staff of Barrang Lompo Marine Station for their help during experiments�

REFERENCES

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