Page 100 - Danir_Arsbok2024_ENG_Digital

DANIR 2024 | Our involvement
“ Over the years, several different forms of artificial
reefs have been experimented with. The first to be
deployed around Shungimbili were bottle reefs.”
nurseries, and three table nurseries. Together, they
harbour over 9,000 coral fragments.
TIME TO GRADUATE FROM NURSERY SCHOOL
AND GO TO “WORK”
When the corals have grown large enough in the
nurseries, it is time for them to be moved out onto
the reefs. Corals have no roots but attach them-
selves to the substrate by secreting a calcareous
skeleton. For the corals to be able to take hold, it is
important that they are planted on a stable surface
and secured properly. If there is the slightest move-
ment in the substrate, the coral will not be able to
attach itself and will have difficulties surviving.
To secure the corals, several different methods
are used depending on which substrate is available
at the site. If there is enough stable ground, the
corals can be planted directly on the reef.
When reefs are severely degraded, as in the case
of Shungimbili, where dynamite fishing and drag
netting had pulverised them, the stable substrates
needed to plant corals are unavailable. Artificial reefs
are then used to create a stable base.
Over the years, several different forms of artificial
reefs have been experimented with. The first to be
Artificial reef made of concrete foundations with embedded glass bottles.
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deployed around Shungimbili were bottle reefs. They
consist of a concrete foundation with embedded
glass bottles that are perfect for placing corals in
between. Several of these bottle reefs were created
and laid out in the way that reefs spread naturally.
Another solution are the hollow concrete pyra-
mids. As well as providing a firm base, they have
proven to be very popular hiding places for reef fish
and all kinds of marine invertebrates.
But the construction most used to create artificial
reefs are “reef stars”. They are very easy to handle,
cover larger areas and are therefore more efficient.
Reef stars are used successfully all over the world
and consist of iron frames that are covered with
a painted layer of cement and sand. This prevents
rust and helps the corals to attach. The corals from
the nurseries are attached to the frames with zip
ties and even if you want to use as little plastic as
possible this is the most successful method so far. A
better alternative has not been found.
Creativity plays a large part in the construction
of artificial coral reefs. Creativity and recycling
were the keywords when the largest artificial reef
structure to date was created from an old telephone
tower. The tower was cut into sections, treated with
the same concrete slab as the reef stars and placed
at a depth of about 10 meters on the Villa Reef just
south of the island. The corals that were planted on
the structure have already grown a lot and many
different fish live a better and more protected exis-
tence in and around the old telephone tower.
A VISION FOR LONG-TERM
NATURE CONSERVATION
As Thanda Island is situated in the heart of the
Shungimbili Island Marine Reserve, the care of
marine life means a lot to Thanda as a business, but