Closing the circle: is it feasible to rehabilitate reefs with sexually propagated corals?

Published source details Guest J.R., Baria M.V., Gomez E.D., Heyward A.J. & Edwards A.J. (2014) Closing the circle: is it feasible to rehabilitate reefs with sexually propagated corals?. Coral Reefs, 33, 45-55.
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This study is summarised as evidence for the following.

	Action	Category
	Cultivate coral larvae in an artificial nursery located in a natural habitat Action Link
	Transplant nursery-grown coral fragments onto artificial substrate Action Link

Cultivate coral larvae in an artificial nursery located in a natural habitat

A 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)

(Summarised by: Ann Thornton)
Transplant nursery-grown coral fragments onto artificial substrate

A replicated, randomized study in 2008–2010 at an in-situ nursery and natural reef in Malinep, Philippines (Guest et al. 2014) found that growing fragments of stony coral Acropora millepora on cement ‘plug-ins’ for longer in a nursery before transplanting led to a higher survival rate compared to fragments transplanted after less time in the nursery. After 31 months, survival rate was higher for fragments transplanted after 19 months in the nursery (47%) compared to fragments transplanted after 14 (12%) or seven months in the nursery (8%). In April 2008, PVC-pipe racks with 200 coral ‘plug-ins’ (comprising a cylindrical 20 × 15 mm cement head with a plastic screw plug attached) each supporting at least one juvenile stony coral, were taken from an ex-situ rearing tank to an artificial nursery on a nearby reef. After seven months, sixty plugs were randomly selected and transplanted to a natural reef and attached using holes drilled into the substrate. After 14 months, a further 60 plug-ins were transplanted, with the final 30 plug-ins transplanted after 19 months. Survival was monitored approximately monthly from October 2008–October 2010, and size (average diameter) every six months. Cost (US$)/surviving 2.5-year-old coral was estimated by dividing the total project cost by the number of plug-ins supporting one juvenile coral transplanted at each stage. Cost for corals transplanted at seven months (US$284), 14 months (US$217), 19 months (US$61). Full details in the original paper.

(Summarised by: Ann Thornton)