Home' Partners : Partners: The Philippines – the power of multi-disciplinary research Contents PARTNERS ISSUE THREE 2017
undergo sexual reproduction.
In the 1980s, Professor Harrison was involved in
the discovery of something unusual about coral
sexual biology. To maximise opportunities for
novel genetic recombinations, many corals spawn
en masse, releasing vast quantities of egg and
sperm bundles that form slicks on the surface of
Once fertilised, the eggs grow into millimetre-
long, maggot-like larvae over several days. If the
larvae can find a suitable spot to settle on the reef,
they metamorphose into juvenile polyps, grow
tentacles and start feeding. After six weeks, the
polyps are big enough to start dividing and the
colony-producing process gets under way.
"Colonies can be many decades old and grow
into areas that are over 10 metres wide," Professor
Harrison says. "But they all start as tiny larvae, with
only a minuscule percentage surviving to form
large coral structures."
HOW TO FOSTER BABY CORAL
The Philippines lies within the Coral Triangle
that includes 35% of the world's coral reefs and
more than 75% of all coral species---a degree of
biodiversity greater than the Great Barrier Reef.
The Philippines' reefs are worth more than US$2
billion annually from fishing, tourism and the
storm protection services they provide. Despite
their environmental, social and economic value,
about 98% of the Philippines' reefs are classified as
ACIAR's reef restoration work is being
undertaken in the reefs of northern Luzon. The
method involves raising millions of coral larvae
and then assisting their settlement into damaged
areas using underwater enclosures or tents
made of fine mesh. To obtain coral larvae, two
techniques have been developed.
The first involves temporarily relocating mature
coral colonies to a laboratory tank with flow-
through seawater at the aquaculture facility of
the Bolinao Marine Laboratory. The controlled
environment makes it possible to experimentally
maximise fertilisation rates (currently at close to
100% efficiency) and larval survival rates.
The team is also developing protocols for the
wild capture of egg-sperm bundles during mass
spawning events. The capture involves using
protective mesh enclosures on the reef's surface
before larvae are transferred to the underwater
tents for five to seven days for settlement. The
mesh tents are then removed and the settlement
"To scale up this kind of restoration work for
larger reef areas, it will be essential to have reliable
methods to rear larvae at sea," Professor Harrison
says. "Our first successful spawn capture took place
in 2016 and each time we do it we refine our
ability to do the rearing work at sea."
are then scooped up as they float to the surface.
Professor Harrison considers the practice a
sign of poverty and desperation, an easy way to
harvest the last of dwindling fish stocks to feed
The blasts, however, are so damaging that they
convert complex underwater coral forests into
rubble. Paradoxically, in the search for alternative
and more profitable income streams, coral reefs
and their conservation and restoration stand to
play pivotal roles in the Philippines and around
Corals are unusual organisms. They are animals, yet
they host photosynthesising, single-cell algae and
they also secrete a calcium carbonate exoskeleton,
which is responsible for the rock-like appearance
The animal part of a coral colony is made up
of genetically identical polyps that can reproduce
asexually by simply splitting into two. Polyps,
however, can generate new genetic identities---
the grist for the mill of adaptation and evolution---
by releasing eggs and sperm bundles that
Mesh curtain deployed on a coral reef restoration site.
Dexter dela Cruz and Peter Harrison adding coral (A.
tenuis) larvae into a resealable portal of the mesh
enclosure to seed restoration of corals on a damaged
reef in the Philippines.
PHOTO: KERRY CAMERON
PHOTO: PETER HARRISON
PHOTO: PETER HARRISON
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