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ENVIRONMENTAL FEATURE

of a coral colony and planting those fragments elsewhere with
limited threats, the colony can be given a new living environment in
which to multiply and grow.
On the reefs, the Zanzibar team looks for pieces of coral that have broken
off naturally by waves, storms etc. Known as ‘corals of opportunity’, these
corals are cut into smaller coral fragments and placed on a cement plug
which is put onto a table on the sea floor. There are about 22 tables in
the nursery.
After approximately three to eight months, the corals in the nursery
have grown sufficiently. During the entire nursing process, the
community and conservation rangers regularly clean the juvenile corals
by removing algae, sediment and predators such as the Drupella snail
and Crown of Thorns starfish. A substrate is then selected to plant the
coral plugs, either in existing reefs that have (partly) lost their corals, or
by using different materials to plant the plugs, for example on limestone,
reef balls etc.

The juvenile corals are moved carefully to the area where the restoration
is planned and the plugs with juvenile corals are inserted into holes
drilled in the substrate. They are firmly fixed with adhesive. During the
first weeks, checks are done to see whether the plugs remain fixed in the Coral tables
substrate, and the corals are cleaned. Some grow fairly quickly, others
more slowly, and the aim is to make a natural reflection of the coral
ecosystem in the area.

Outplanting a mixture of coral genotypes is critical for ensuring cross-
fertilisation of corals within a reef site. Outplanting several genotypes
in close proximity will increase the chances of successful reproduction,
helping to enhance genetic diversity and coral population recovery. It is
recommended to outplant at least ten genotypes per coral species in a
site, with at least three replicate coral colonies.

Pratley Putty used in rehabilitation of coral reefs
In celebration of Earth Day on 22 April, Pratley Putty showed
how its product is assisting Oceans Without Borders to preserve
Mnemba Island coral reef restoration project the coral reefs around Mnemba Island. It is being used to
secure coral fragments in the nursery and to outplant the coral
colonies onto the reefs.
The establishment of the Oceans Without Borders Coral
Nursery Project has been led by their team of community
and conservation marine rangers who also maintain, nurture
and expand the coral nursery. Broken pieces of parent coral
are collected from around the reefs, and fragments are grown Diver cleaning corals
into new coral colonies. Each fragment is secured to a special
cement disc with Pratley Putty and added to the underwater
coral nursery tables.

Algae is scrubbed off every disc, along with its coral fragment,
to ensure healthy growth. It takes about six to nine months for
the coral fragments to grow into new colonies, at which point
they are ready to be transplanted back into the reef.

Dr Tessa Hempson, Principal Scientist on the restoration project,
says that the putty is a high-performance adhesive, ideal for
underwater use, and longer lasting than any other putty that
was tested. This gives the transplanted coral the best chance of
survival.

Information sources
www.oceanswb.org/projects/coral-reef-diversity
www.crc.world/why-restoration
www.marinecultures.org/en/projects/coralreef

Photos courtesy of Dr. Tessa Hempson, Oceans Without Borders Programme
Manager and Principal Scientist
A diver holds coral fragments n

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