Yael Horoszowski

Gardening Coral Reefs – Testing the Applicability of Using Nursery-Grown Coral Transplantation for Coral Reef Restoration

Nursery grown corals at the coral nursery.

Preliminary transplantation taken by Shai Shafir.

Town/RegionCountryCategoriesDate
Gulf of Eilat, Red SeaIsraelCoral, Middle East15 Dec 2006

The current state of coral reefs worldwide is alarming. Anthropogenic activities have significantly weakened the reefs' ability to cope with natural disturbances and to maintain themselves. Active restoration is now crucial to preserving this highly diversified and productive ecosystem. In the past, whole coral colonies or coral ramets were taken from healthy localities and transplanted into denuded areas. However, low survival rates of the transplants and the stress caused to donor colonies proved this method to be ineffective. In response, we suggest the "gardening coral reefs concept," a new method that adopts forest restoration techniques in the field of coral reef restoration. This method consists of two steps:

1) generating and culturing minute coral fragments in an in situ nursery,

2) transplanting these colonies, when adult, in the degraded reef.

The transplantation of whole colonies instead of coral fragments substantially increases their ability to acclimate to the new environment. The nursery phase allows the initiation of the colony rearing from nubbins (1-10 polyps), which greatly reduces the stress caused to the donor colonies. It also enables the generation of thousands of new colonies which restore large zones in a short period of time.

This project consists of carrying out this revolutionary technique of transplanting nursery-grown colonies in a degraded reef in order to restore the reef of Eilat (Red Sea, Israel). Eilat’s coral reef is the world’s most northern reef. This reef, which was classified in the past among the richest and most biodiversed reefs, has been in decline for the past forty years. New colonies generated in the coral nursery will be transferred by boat to the degraded site and transplanted on selected knolls. The transplanted corals will reinforce the poor local coral community, creating new spatial and ecological niches for marine invertebrates and fish, and thus, should simulate a whole coral reef associated fauna. Furthermore, they may also contribute and enhance the local larval pool by participating in the local coral reproduction. The settlement of new coral colonies could also increase due to the presence of the transplanted colonies since larvae tend to settle in areas where adult colonies already exist or on exposed coral skeleton.

The research will examine the survival rates of the transplants, their acclimatization in the new environment as well as the transplantation's influence on the local invertebrates and fish community.

For more information contact yaelh@ocean.org.il

Project Update: August 2007

A restored knoll immediately following the transplantation.

During May 2007, four hundred coral colonies were prepared at the nursery for transplantation. The plastic tips and the plastic anchors on which the corals are attached were cleaned of settling algae, other sessile organisms, and coral predators (Drupella snail etc). They were arranged on trays according to their destination.

Some of the colonies were incubated for 12 hours (from sunrise to sunset) with Alizarin Red, an inert calcium competitor precipitated by the coral along with calcium molecules in the process of skeleton formation, in order to follow the future corals’ growth. Once cleaned, the coral trays were placed in large recipients filled with seawater and transferred by boat from the coral nursery to the restoration site.

The colonies were then transplanted on two knolls by divers. Holes were drilled in the knolls in regular distances of 10 cm using an underwater drill. The tips and anchors were inserted in the holes, permitting a good attachment of the corals to the rock. Each colony was marked with a plastic tag in order to follow the corals’ acclimation and survival during the next months.

Project Update: March 2008

Nursery-grown colonies that were transplanted onto a denuded knoll.

Since May 2007 we are following closely every month the nursery-grown coral colonies that were transplanted onto the two denuded knolls of the degraded zone of Eilat's reef.

The first question asked was if coral colonies that were maintained under ideal conditions in the nursery, can adapt to the harsh conditions in the natural reef (the transplanted area is located in front of a busy diving center, and there is fish and coral-predators activity at the natural reef). We therefore decided to look very closely on survivorship, detachment, bleaching and the general health of transplanted colonies during the first 4 months following their transplantation.

This analyze revealed a very low mortality rate of the new transplants (less than 5%) during those months. This survivorship is similar to the natural colonies monitored at the site, serving as controls. In addition, soon after the transplantation the colonies, especially the Acropora ones, started spreading on the knolls. These results indicate that the transfer from the nursery back to the reef does not lead to a severe stress (likely to cause a massive mortality) and the colonies are adapting to the new environmental conditions.

Project Update: April 2008

A Parrotfish grazing on a newly transplanted favia colony.

Transplantation of coral colonies can result with unexpected outcomes.

Transplanted colonies of Stylophora and Favia were surprisingly attacked by local fish (i.e. butterfly fish grazed on polyps, parrotfish broke branches or scrapped tissue) immediately following their attachment to the new sites. Those attacks led to tissue damage, loss of branches, and in extreme cases to the detachment of the colony from the substrate. While at first, we worried about the fate of damaged corals, a surprising fast recovery of most of the attacked colonies was evident. This further indicates for the good physiological condition of the nursery-grown colonies that were raised in the coral nursery under idyllic condition, permitting them to cope with the biological disturbances encountered at the natural reef.

In addition, our transplants were quickly colonized by invertebrates including Trapezia crabs, Spirobranchus worms and Alpheus shrimps. The spatial and ecological niches created by the presence of the reef-building corals were filled by those coral obligatory invertebrates. Thus, the transplants not only reinforce the local coral population, but also stimulate coral reef in-fauna.

Project Update: May 2008

Planulae collection.

In order to analyze the transplants’ reproduction we placed planulae collection devices on several Stylophora colonies from sunset till sunrise. We then analyzed the plastic cups attached to the plankton nets for planulae presence.

We counted the collected planulae under a binocular in the field and then released them back at the experimental site. All of the examined colonies liberated larvae in big numbers.

Thus, the nursery-grown transplants’ contribution is threesome: reinforcement of the poor local coral community, creation of new niches for fish and invertebrates to colonize and enhancement of the local larval pool by participating in the local coral reproduction.

Final Report

Read more about the activities undertaken and findings of this project in the final report below.

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Final Report.doc724.5 KB

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