Cultivate coral larvae in an artificial nursery located in a natural habitat
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Overall effectiveness category Awaiting assessment
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Number of studies: 15
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Supporting evidence from individual studies
A replicated study in 1994–1995 on an artificial nursery on a coral reef at Orpheus Island, Great Barrier Reef, Australia (Mundy & Babcock 2000) found that some transplanted nursery-grown stony coral Goniastrea aspera, Oxypora lacera and Platygyra daedalea spat (settled larvae) on settlement tiles at different depths survived and survival rates were broadly similar between species and depths. Three months after transplanting, less than 15% of spat had survived. Twelve months after transplanting, there was no significant difference in average survival between species or depth transplanted at different depths (Goniastrea aspera: shallow 1.4%, mid 0.3%, lower3.1%; Oxypora lacera: shallow 1.1%, mid 2.4%, lower 1.6%; Platygyra daedalea: shallow2.1%, mid 1.4%, lower 1.6%). In December 1994, egg/sperm bundles were collected from 810 mature colonies of three species of stony coral and transferred to settlement jars for four days to develop. Larvae were transferred to PVC trays for five days to settle onto terracotta tiles (11 × 11 × 1 cm). Ten replicate settlement tiles/species were transferred to the reef and bolted to the substrate at each of three depths (shallow: 0 m; mid: 5 m; lower: 10 m). Survival and number of juvenile corals were counted after three and six months when tiles were retrieved for examination and returned to the reef within 24 hours. Tiles were then collected and examined at the end of the 12-month experiment. Tiles at the second site were retrieved and examined after three months but not returned.
Study and other actions testedA replicated, controlled study in 2004–2005 at an artificial coral nursery in a natural habitat at Akajima Island, Okinawa, Japan (Omori 2005) reported that stony coral Acropora tenuis polyps cultivated on settlement tiles in cages containing juvenile top shell snails Trochus niloticus survived longer than polyps cultivated in cages without top shells. Nine months after settlement, 10–39 polyps on each settlement tile in cages with juvenile top shells had grown to ~40 mm diameter whereas all polyps in cages without top shells died within four months of settlement (no statistical analysis carried out). Settlement plates in the cages without top shells were observed covered in algae, sponges, hydroids and sea squirts. In June 2004, stony coral Acropora tenuis polyps were attached to concrete 10 cm2 settlement tiles. Tiles were placed into plastic cages (number not reported) that also contained juvenile top shell snails. A control cage was prepared containing stony coral polyps on settlement tiles without top shells. Cages were suspended 2 m above the seafloor at a depth of 3.4 m. No information on sample sizes, sampling method and frequency was reported.
Study and other actions testedA replicated, randomized study in 2006–2007 at an artificial nursery in a natural habitat at Nichidomari, southwestern Japan (Nozawa 2008) found that when cultivating wild-grown stony coral Echinophyllia aspera, Favites pentagona and Platygyra contorta spat (settled larvae), survival was higher for spat growing in artificial crevices on slate tiles compared to spat growing on the tile surface. After four months, all larvae that settled on the surface of the tile between crevices had died, whereas after one year, survival rate for coral spat in the crevices ranged from 1.5% (Favites pentagona) to 12% (Platygyra contorta) (data presented as a figure). In August 2006, larvae collected from wild-growing colonies of Echinophyllia aspera, Favites pentagona and Platygyra contorta corals were taken to a laboratory and placed into settlement containers (five/species) each containing four 10 × 9 × 0.5 cm slate tiles with 70 artificial crevices drilled into the surface. Larvae settled on the tiles for two to three weeks before tiles were moved to a nearby bay and randomly fixed horizontally (8 or 10/species) or vertically (10/species) to rocky substrate 2 m above the sea floor, 5 m deep. Tiles were retrieved every month for 12 or 13 months and survival and position of each spat was recorded using a dissecting microscope before tiles were returned to the site. Growth was measured using photographs.
Study and other actions testedA replicated study in 2006–2007 at an artificial nursery in a natural habitat at Nichidomari, southwestern Japan (Nozawa 2008) found cultivating stony coral Echinophyllia aspera, Favites pentagona and Platygyra contorta spat (settled larvae) led to mixed results for survival and growth on slate tiles fixed vertically compared to horizontally. After approximately one year, coral spat survival rate was higher on tiles fixed vertically compared to horizontally for Echinophyllia aspera (10% vs 1.5%) and Favites pentagona (7.3% vs 1.5%) but lower for Platygyra contorta (5% vs 12%). Growth of Echinophyllia aspera spat on vertical tiles was higher (3.3 mm2) compared to horizontal (1.1 mm2) but there was no difference for Favites pentagona (vertical: 3.7 mm2, horizontal: 2.9 mm2) or Platygyra contorta (vertical: 4.4 mm2, horizontal: 3.3 mm2). In August 2006, larvae collected from wild-growing colonies of Echinophyllia aspera, Favites pentagona and Platygyra contorta corals were taken to a laboratory and placed into settlement containers (five / species) each containing four 10 × 9 × 0.5 cm slate tiles each with 70 artificial crevices drilled into the surface. Larvae settled on the tiles for two to three weeks before tiles were removed to a nearby bay and randomly fixed horizontally (8 or 10/species) or vertically (10/species) to rocky substrate 2 m above the sea floor, 5 m deep. Tiles were retrieved every month for 12 or 13 months and survival and position of each spat was recorded using a dissecting microscope before tiles were returned to the site. Growth was measured using photographs.
Study and other actions testedA replicated, controlled study in 2007 at two depths at an artificial nursery on a coral reef in Malilnep channel, Philippines, (Baria et al. 2010) found that using full or partial caging to exclude predators from transplanted stony coral Acropora tenuis spat (settled larvae) resulted in higher survival compared to uncaged spat. After three months, average survival rate at two depths of caged spat (4 m: 17%, 9 m: 33%) and partially caged spat (4 m: 19%, 9 m: 23%) was higher than uncaged spat (4 m: 5%, 9 m: 11%). There was no difference in survival between caged and partially caged spat. In June 2007, sixty pairs of fibre-cement settlement tiles each with 20 coral spat (>1 cm apart) were attached 20 cm apart on a metal rod suspended 10 cm above the substrate on two metal posts. Forty structures were fully covered by 1 cm2 PVC mesh cage, 40 were partially covered (open-sided cage) and 40 were left uncaged. Structures were placed at 4 m and 9 m (60 structures/depth). Survival of spat was recorded after three months in September 2007.
Study and other actions testedA replicated study in 2008 at an artificial nursery on a coral reef in South Water Cay, Belize (Ritson-Williams et al. 2010) found that some elkhorn coral Acropora palmata and staghorn coral Acropora cervicornis spat (settled larvae) transplanted onto coralline algae fragments attached to tiles survived, but survival of staghorn coral depended on the coralline algae species used. After six weeks, on average, similar percentages of elkhorn coral spat survived on fragments of Hydrolithon boergesenii (17%) and Titanoderma prototypum (19%). For staghorn coral, 13% of spat survived on Titanoderma prototypum fragments and no spat survived on Hydrolithon boergesenii fragments. In August 2008, wild-collected elkhorn and staghorn coral egg/sperm bundles were cross-fertilized in a laboratory. Larvae were settled on fragments (1 × 1 cm) of two coralline algae species. For each coral species, 1–2 fragments of Hydrolithon boergesenii and Titanoderma prototypum, each with 1–5 spat, were attached to 14–15 terracotta tiles (10 × 10 cm) using underwater epoxy. Tiles were bolted face down on a reef (3-m deep), with a 2-cm gap between the tile and reef. After six weeks, all tiles were retrieved, and proportions of surviving spat recorded using a dissecting microscope.
Study and other actions testedA study (years not given) at an artificial coral nursery in a natural habitat in Eilat, Israel (Linden & Rinkevich 2011) reported that the majority of stony coral Stylophora pistillata spat (settled larvae) cultivated in artificial nurseries in a natural habitat survived. Four months after being placed in artificial nurseries, 428 of 480 spat (89%) survived and began to form 3D structures. Larvae collected from wild-growing colonies of Stylophora pistillata were taken to a laboratory and placed in settlement containers (petri dishes containing paper discs). At the age of 1–2 months, 480 spat were individually glued onto plastic pins placed in trays (45 × 32 cm) made of PVC pipes and plastic netting (0.5-cm2 mesh). Trays were attached to the coral nursery, located ith cable ties and covered with white plastic nets (1-cm2 mesh). Algae and encrusting invertebrates were removed from trays monthly. Each tray was photographed monthly (dates not given) to monitor spat mortality and growth.
Study and other actions testedA replicated study in 2004 at an artificial nursery in a natural habitat off the coast of Moorea, French Polynesia (Penin et al. 2011) found that transplanting nursery-grown stony coral Acropora striata recruits on tiles covered in cages led to similar survival to those on uncaged tiles. After one week, the average proportion of surviving Acropora striata recruits did not differ significantly between caged (48%) and uncaged tiles (44%). On average, caged tiles had a higher proportion of intact dead recruits (47%), a lower proportion of removed or damaged recruits (5%) and greater algae cover (82%) than uncaged tiles (intact dead recruits: 28%; removed/damaged recruits: 28%; algae cover: 24%). In 2004, Acropora striata larvae reared in the laboratory were placed in tanks and settled on 18 terracotta tiles (11 × 11 × 1 cm). After one week, 1-mm coral recruits on six tiles (average 35 recruits/tile) were placed at each of three depths in the sea (6, 12 and 18 m). Half of the tiles at each depth were covered with 1.2-cm wire cages, and the other half were left uncovered. Coral survival and algae cover were assessed after one week using photographs.
Study and other actions testedA replicated, randomized, before-and-after study in 2010 at an artificial nursery on two coral reefs off Ishigaki Island, Japan (Suzuki et al. 2011) found that 72 h after stony coral Acropora spp. larvae were deposited on artificial reefs there was higher settlement on reefs at 3.5 m than 2 m depth, but no difference related to grid size or plate arrangement, whereas after seven months there was higher survival on plates with narrower grids, but no difference related to plate arrangement or depth. After 72 h, more juvenile corals settled on settlement plates at 3.5 m (0.5–0.9 corals/cm2) than 2 m depth (0.1–0.2 corals/cm2). After seven months, survival was higher on plates with narrower grids than wider grids (average corals/plate: 2.5 cm grid = 52; two stacked 4 cm grids = 8; a single 4 cm grid = 1; 8 cm grid = 0). See original paper for non-statistically significant results. In February 2010, experimental plates (comprising fibreglass-reinforced plastic/polycarbonate) with different grid sizes were set up at two sites (one 2 m deep and one 3.5 m deep), and plates arranged to create different structures (see paper for designs) were also set up at the 3.5 m depth site. Plates were 50 cm2 with a grid size of 2.5 cm, 4 cm, two 4 cm plates stacked, or 8 cm (three replicates at each site). Different grid sizes and arrangements were placed randomly, >2 m apart. Mature stony coral colonies were collected from the reef and taken to an artificial nursery to spawn. Egg/sperm bundles were collected and placed into tanks to enable larvae to develop. Larvae were introduced to the plates four days later (see paper for methods). Coral spat were surveyed 72 h after larvae were introduced and survival was surveyed one, three, six and seven months later.
Study and other actions testedA replicated study in 2007–2009 at an artificial nursery in a bay in Otsuki, Japan (Nozawa 2012) found that transplanting stony coral Echinophyllia aspera and Favites abdita spat (settled larvae) on plates with smaller refuge structures led to greater survival compared to those on plates with larger structures. Two years after transplantation, 16% of Echinophyllia aspera spat survived on plates with 5-mm refuge structures, whereas all spat on plates with 15- and 25-mm structures died within 3 and 12 months respectively. For Favites abdita, 12% of spat survived on plates with 5-mm refuge structures, 2.5% survived on plates with 15-mm structures, and all spat on plates with 25-mm structures died within two years. In July–August 2007, eggs and sperm were collected from wild-growing Echinophyllia aspera and Favites abdita colonies and cross-fertilized. Larvae were placed in tanks containing cement slate plates (10 × 9 × 0.5 cm) with each of three sizes of refuge structure (5, 15 and 25 mm wide) created from 4-mm projections of underwater epoxy. After three weeks, plates with spat of each species (175–325 plates/refuge size) were randomly selected and bolted vertically to rocky substrate (10-30 cm apart, 5 m deep) with refuge structures facing outwards. Plates were retrieved at one, two, three, six, 12 and 24 months after transplantation and spat survival assessed using a dissecting microscope.
Study and other actions testedA study in 2008 at a laboratory and artificial nursery on a natural coral reef in Luzon, Philippines (Guest et al. 2014) reported that nursery-reared stony coral Acropora millepora spat (settled larvae) settled onto cement and plastic ‘plug-ins’ and then cultivated in an artificial nursery on a reef survived and grew. One month after ~102,500 larvae were placed in settlement tanks, there were 1,390 (1.4%) surviving coral spat (settled larvae) on 531/840 artificial settlement plug-ins (range: 141 corals/plug). Plug-ins supporting at least one coral were transferred to an in-situ nursery for a further six months, with 200 (14.4%) corals surviving on 153 plugs (14 corals/plug). Approximately seven months after fertilization, the average diameter of surviving corals was 4.4 mm. In March 2008, three wild-growing colonies of Acropora millepora were collected from the reef and taken to a laboratory where they spawned. Egg/sperm bundles were collected and allowed to fertilize. Four days after spawning, ~102,500 larvae had developed from ~120,000 eggs (85.4%). Larvae were placed in tanks for seven days to settle onto plug-ins (comprising a cylindrical 20 × 15 mm cement head with a plastic screw plug attached) on racks made from sections of PVC pipe. Racks were transferred to rearing tanks in the laboratory for one month then live coral was counted and any plugs supporting live coral were transferred to an artificial nursery on a nearby reef. Coral survival and growth were measured after six months in the in-situ nursery (seven months after fertilization)
Study and other actions testedA replicated study in 2012 - 2014 at an artificial nursery in a natural habitat in Curaçao, Southern Caribbean (Chamberland et al. 2015) found a higher survival rate for elkhorn coral Acropora palmata larvae outplanted on clay tripods in the wild compared to larvae reared in a land-based nursery, but no difference in size. Overall survival rate after 31 months was 6.8 times higher for outplanted (3.4%) compared to nursery-grown corals (0.5%). After 31 months, 32% of substrate structures in the wild supported at least one settler compared to 3% of structures in the nursery. There was no difference in average size of corals between outplanted (17 cm2) and nursery-grown coral (13 cm2) after 31 months. In August 2012, approximately 4,000 egg-sperm bundles were collected from four colonies of Elkhorn coral at 1–5 m deep. These were transferred to an ex-situ nursery and allowed to settle onto 320 clay pottery tripods (see paper for methods). After two weeks, 30 tripods each hosting an average of 11.1 settled larvae were transferred back to the reef and fixed to the substrate. Larvae on the other 30 tripods (average 11.1/tripod) were grown in the nursery. Survival (number of live settlers) was recorded after 1, 6, 11, 17 and 31 months. Size was measured after 17 and 31 months by photographing colonies against a ruler for scale. Costs reported in 2015: Nursery maintenance (including labour and utilities) = US$12,875/year. Larval rearing costs (including labour and materials) = US$8,814. Outplanting and monitoring (including labour and materials) = US$6,284. See paper for full cost breakdown.
Study and other actions testedA replicated study in 2014–2016 at artificial nurseries at five natural sites of mixed substrate in Sekisei Lagoon, Japan (Suzuki et al. 2018), found that some nursery-grown stony coral Acropora tenuis and Acropora selago larvae cultivated in plastic trays in a natural habitat survived and grew. After 72 h, there were approximately 2,5–30 settled larvae/100 cm2 at four of five sites (fifth site: ~150/100 cm2). After one month, survival ranged from ~2080% falling to 115% after 15 months. The average number of juvenile corals/plate decreased from 489/plate 15 months after settlement to 448/plate after 26 months. Average juvenile colony size grew from 814 mm 15 months after settlement to 1328 mm after 26 months. In May 2014, ten colonies each of Acropora tenuis and Acropora selago were collected from the wild and taken to a laboratory where spawning was induced. After four days, 1,000 larvae from each species were placed into 40 bags each containing a fiber-reinforced plastic settlement plate with thirty-six 4 × 4 × 4 cm cells in a 6 × 6 grid. Eight plates were attached to the substrates using anchoring bolts and cable ties or, on sandy substrate, using an iron rod. Survival and settlement numbers were recorded after 72 h, and 1, 3, 6, and 15 months by removing and examining the plates under a microscope. Juvenile corals were counted in-situ 15 and 26 months after settlement.
Study and other actions testedA study in 2019–2020 at an artificial nursery in a natural habitat off southeastern Dominican Republic (Villalpando et al. 2021) reported that transplanting nursery-grown coral Dendrogyra cylindrus spat (settled larvae) on tiles hung 1 m above the sea floor resulted in very low survival. A year after settled larvae were transplanted only one had survived (of an estimated 380 larvae). In August 2019 (after sunset, three nights after full moon), sperm and eggs were collected in-situ from two male and two female coral colonies. Sperm and eggs were mixed in the laboratory (83% fertilization rate) and larvae were fully developed within 24 hours. Twenty star-shaped ceramic tiles were added and left for 10 days for larvae to settle and the number of settlers on two tiles were counted. A month later, tiles were transferred to an in-situ nursery (12 m deep) and hung 1 m above the seafloor. Survival was assessed in May 2020 and September 2020.
Study and other actions testedA replicated, controlled study in 2017–2018 at an artificial nursery in a natural coral reef off Palau (Evensen et al. 2021) found that cultivating coral Acropora digitifera larvae in a natural habitat with a protective cage resulted in higher survival than when a partial cage or no cage was used in one of two experiments. One experiment using ‘clean’ settlement tiles found higher survival for corals on caged tiles (24–34%) than for corals on partially caged or open tiles (1–12%). The other experiment using settlement tiles ’conditioned’ on the reef found similar low survival for corals on caged (1 of 121 larvae) and uncaged tiles (3 of 215 larvae). In 2018, settlement tiles (10 × 10 cm) comprising a checkerboard arrangement of 1 cm × 1 cm raised squares were placed on the reef in 12 plots of three tiles each (one caged tile, one partially caged and one open). After four weeks, the tiles were retrieved and any algae removed. A second set of tiles of the same design was left (caged or uncaged) to ‘condition’ on the reef for six months before being returned to the aquarium. In April 2018, coral larvae were collected from eight adult colonies, transferred to ex-situ aquaria and settled on to the ‘clean’ or ‘conditioned’ tiles (10 × 10 cm) In the first experiment, clean tiles with coral spat (settled larvae) were returned to the reef. Tiles were arranged in 12 plots with one each of caged, partially caged and open tile. Survival was assessed after 28 days, then every 14 days until 70 days had passed. In the second experiment, the tiles with coral spat were returned to the reef and placed, caged or uncaged, in 12 plots on the reef. Survival for corals in the second experiment was assessed after 70 days.
Study and other actions tested
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This Action forms part of the Action Synopsis:
Coral ConservationRelated Actions
| Actions | Effectiveness | Studies | Category | |
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Cultivate corals in an ex-situ nursery Action Link |
Awaiting assessment | 36 |
Synopsis Link |
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Cultivate coral larvae in an artificial nursery located in a natural habitat Action Link |
Awaiting assessment | 15 |
Synopsis Link |
Coral Conservation - Published 2024
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