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31 .
Map-a-bommie scuba project
3 hr +
FROM PROJECT REEF ED
Concepts
Aim
ei Great Barrier Reef Marine Park Authority
Ecology
• To investigate the ecology of a submerged coral mass (bommie). This is a
Distribution
project requiring the use of scuba. it is recommended for a group of three or
Habitat
four divers.
Population
Environment
You will need
Skills
Organisational
skills
Orientation
skills
Using compass
Observing and
recording
underwater
Mapping
Cooperation
Attitudes
Appreciation
of
natural
environment
Perseverence
Enjoyment of
outdoor
experience
•
Diving gear (scuba)
•
Underwater slate and pencil
•
Underwater camera and torch (optional)
•
Submersible compass
You will need to make three scuba dives at less than
10
metres.
What to do
1. To understand the ecology of a bommie, it is
first necessary to analyse the
physical features of the
bommie and to
assess the physical factors to which it is
exposed. Choose a bommie which has appealed to you while snorkelling
along the reef slope. Try to choose a bommie no larger
than 5m
in diameter
and no smaller than 2 m in diameter. Your bommie should also be in less than
10m of water (to reduce your
air consumption and avoid
decompression
problems).
First dive
2. (a) Record the position of your bommie on an outline map of the reef. You
will need to take compass bearings from the bommie to prominent
features of the island (end of vegetation, towers, etc.).
(b) Record the size of your bommie.
3. Record the depth of the bommie at low
tide. Hover above the bommie and
make an outline
sketch of the bommie on your slate.
Now descend to the
base of your bommie
and make a sketch of its western side. Move through
90° (naturally, using your compass) and make a sketch of its northern side.
Continue this procedure so that you obtain sketches of the eastern and
southern aspects also.
As
you make these sketches, pencil in any prominent
features, e.g. masses of brain coral, caves.
4. Make relevant notes on such things as currents in the area, slope of the
bottom, proximity of other bommies and any other physical factors which you
think may have an influence on your bommie.
Second dive
5. Slowly
circle your bommie and, on the sketch you made on the first
dive,
record the locations of resident fish on your map (e.g., cod in caves, painted
sweetlip, flutemouths under coral overhangs). Take
particular note of
territorial species such as moray eels, clownfish, etc. Try to find any cleaner
stations. As you
record the different fish species, jot down
their approximate
numbers as shown in the example in figure 77.1.
Third dive
6. Now move in close to your bommie and record the interesting and noticeable
invertebrate life. By this time, you may have to use fresh outline drawings of
your bommie. Try to find and mark on your map the location of nudibranchs,
stinging hydroids, soft corals, etc. Look for sponges and ascidians under
overhangs.
What kind of hard corals are predominant on your bommie? (perhaps you can
enlist the aid of students who have done activity
43,
"Coral Colonies".) Make
sketches of some of the corals so
that you can identify them later.
