Dr. Doug Fenner studies
corals on the Undersea Explorer
Dr. Doug Fenner, a visitor at the Australian Institute of Marine Science
(AIMS), joined two Undersea Explorer expeditions in late October. Doug
is a coral taxonomist, who studies the species and biodiversity of hard
corals on reefs.
He was eager to compare
the corals on the Great Barrier Reef and Osprey Reef in the Coral Sea
with corals he has studied in Southeast Asia. He recorded the species of
corals he saw, and took photos and collected a few samples of species of
particular interest. He found the diversity higher than he expected,
close to the very high diversity found on Southeast Asian coral reefs.
Osprey Reef had a high diversity, well deserving of protected status.
Dr. Fenner found 11
species of coral which were known from other countries but had never
been reported from Australia before. In addition, he found one species
of coral which may prove to be
a new species.
Hard Coral Species Diversity
on Great Barrier Reef and Osprey Reef Sites
Visited by the Undersea Explorer
Douglas Fenner, Ph.D. November, 2003
Abstract
Hard coral species diversity was recorded at 11 outer reef sites on the
Cairns Section of the Great Barrier Reef, and 9 sites on Osprey and
Shark Reefs, Coral Sea visited by the Undersea Explorer in October,
2003, in a total of 31 dives. A total of 257 species were found. An
average of 71 species were found per dive. At sites on the Great Barrier
Reef an average of 82 species were found per dive, and at Osprey and
Shark reefs, 66 species per dive, which was a significant difference.
Osprey and Shark reefs had an average of 76% of the number of species as
the GBR sites for the same number of dives. The number of coral species
found in this study for the equal number of dives is less than that
found in "Coral Triangle" area of highest diversity (Philippines,
Indonesia, and PNG), but not much less, averaging 92% for GBR outer
reefs, and the whole data set average 87% of that of the Coral Triangle.
Thus, Eastern Australian reefs have very high coral diversity, higher
than the present total number of species known suggests. This is
consistent with the finding of 11 species not previously reported from
Australia before. Further, Osprey Reef has a high coral diversity,
nearly that of the outer GBR reefs, and likely higher than inner GBR
reefs and perhaps middle GBR reefs as well. The total coral diversity at
Osprey Reef is certainly higher than the counts in this study, as the
lagoon was not investigated, and because of the very different
conditions there will have corals that are not found on the outer reef
front. The high diversity of corals found on Osprey Reef, plus their
healthy state, supports the view that Osprey Reef deserves protected
status.
The coral species of Australia have been the subject of major studies by
leading taxonomists (e.g., Wallace 1978; Veron and Pichon 1976; 1980;
1982; Veron, Pichon and Wijsman-Best 1977; Veron and Wallace 1984; Veron
1985; Veron 1986). There have been studies of coral diversity on the
Great Barrier Reef as well (e.g., Done, 1982). However, few if any
taxonomic studies of Australian reef corals have been published since
1986, and there is little data on the coral diversity of the reefs of
the Coral Sea. The present study aimed to make a rapid assessment of
coral diversity on outer barrier reef sites visited by the Undersea
Explorer in the Cairns Section of the Great Barrier Reef, and an atoll
in the Coral Sea, Osprey Reef. The method used was the same the author
has used on a variety of Southeast Asia sites, and thus allows a
comparison of the coral diversity with those sites, in the area
generally agreed to be the most diverse area for coral reefs.
Methods
Coral presence or absence was recorded during dives of approximately one
hour at 11 outer barrier reef sites in the Cairn Section of the Great
Barrier Reef, and 8 reef front sites at Osprey Reef in the Coral Sea and
one site on nearby Shark Reef. Dives began at about 25 m depth and
involved a haphazard search toward shallower water over the course of
about one hour, and ended in water as shallow as possible. Photographs
were taken of some species, and samples of a few species, with an
attempt to photograph and/or collect any species not previously reported
from Australia. Dive sites are given in Tables 1 and 2. All dives were
on coral reefs, except dive 22 at Lizard Island, which was on a sandy
bottom. Dives 13a and 13b were on the same reef (Steve's Bommie), and
while all corals were recorded on 13a, only corals that appeared to be
additional were recorded on 13b, so the total number on 13b is not
comparable with other dives. On dive 28, Rapid Horn, corals were only
recorded for about 30 minutes, with the second half of the dive spent
observing fish spawning, thus the total for this dive is not comparable
with other dives.
There is a very strong effect in data sets of the effect of amount of
search effort, time, or area searched. The more time, effort or area
searched, the more species found. Because it is a very strong effect,
sites can only be compared based on the same amount of search effort,
such as after one dive, or five dives, etc.
Results
A total of 247 species of hard corals were recorded, including 234
zooxanthellate scleractinia, 5 azooxanthellate scleractinia (genera
Tubastraea, Dendrophyllia and Rhizopsammia), and 8 non-scleractinian
hard corals (genera Millepora, Stylaster, Distichopora, Tubipora, and
Heliopora). These proportions are typical of Indo-Pacific reefs.
The number of coral species found at each dive site are shown in Tables
1 and 2. The average number of species found per dive site is comparable
between sites, but the total number of species found per site is not,
since the number of dives at a site varied from 1 to 4, and will
strongly affect the result.
Table 3 shows average numbers of corals for 1, 5, 10, and 15 dives for
the outer Great Barrier Reef sites, Osprey Reef sites, all Eastern
Australia sites (the outer GBR sites plus Osprey sites), and 7 sites in
the Coral Triangle area of highest diversity (3 in the Philippines (Veron
and Fenner, 2000), 2 in Indonesia (Fenner, 2001, 2002), 1 in Papua New
Guinea (Fenner, 2003), and 1 in Sabah (Malaysia). Osprey Reef sites had
an average of 76% as many species as the outer GBR sites. The difference
was significant (t test, p < .003). Both Osprey and GBR sites were less
than the average Coral Triangle sites, but the GBR sites in particular
were quite close to those in the Coral Triangle, averaging 92% of the
Coral Triangle numbers. East Australia as a whole averaged 87% of the
Coral Triangle numbers. Osprey Reef averaged 76% of the number of corals
at GBR sites for the same number of dives.
Table 4 presents the 11 species found for the first time in Australia.
All of these species are known from elsewhere in the Indo-Pacific, but
had not been reported from Australia (Veron, 1993; Wallace, 1999; Veron,
2000). Each was photographed and/or a sample collected. One of these
species, Pavona bipartita, is quite common, and even is the most common
coral on one of the reefs (Steve's Bommie). In addition, a coral that
may represent an undescribed species of Anacropora, was collected at
Osprey Reef. Considerable additional study will be required to determine
if it is in fact a new species.
Conclusions
This study represents the first study of the biodiversity of corals on
Osprey Reef, and the first study of Australian corals which controls for
the amount of search effort, time, or area. The amount of search time is
a powerful variable, with the number of species found increasing with
additional effort. The present method is a rapid method that can compare
the biodiversity of corals in different areas without having to find all
species in that area.
No study finds all the species of coral in an area, including this
study. The amount of search time and effort to find nearly all species
is very large and requires a major expenditure of time and money. The
present method is far more cost effective. The present results suggest
that the reefs of Eastern Australia have a good number of coral species
left to find, because the total known (about 391) is less than the
number predicted by considering the number known from the Coral Triangle
(a total of about 600, or 581 in Indonesia, and 512 in the Philippines).
The fact that 11 species were found that had not been previously
reported from Australia, and that taxonomic studies of Australian hard
corals have not been published since 1985. In the time since 1985, many
additional species have been recognized by leading coral taxonomists
outside Australia (Wallace, 1999; Veron, 2000), and some of them are
likely to be eventually found in Australia. The 11 additional species
found it this study raise the number of corals known from eastern
Australia from 391 to 402, and the number for all of Australia from 416
to 427 (Veron, 2000).
Osprey Reef has healthy abundant coral (with few or no dead corals,
Crown-of-Thorns starfish or coral diseases sighted), and a high species
diversity. Although the diversity is less than on outer Great Barrier
Reef sites, the diversity is likely to be greater than that on inner
barrier reefs, and perhaps middle reefs as well. In addition, only sites
on the outer reef slopes of Osprey Reef were visited. Osprey is an
atoll, with a large lagoon and having just one entrance. The lagoon is
large and deep, and has coral communities that are likely to be quite
different from those on the outer slopes of the atoll. This is because
the water enclosed in the lagoon is quite different from that on the
outside of the reef due to its almost complete enclosure. It is likely
that there are fewer species inside the lagoon, but many species inside
the lagoon are likely to be different and not found on the outside
slopes. Thus, the total coral diversity of Osprey is almost certainly
higher than that found in this study. For perspective, the entire
Caribbean has only about 55 species of coral (Fenner, 1999), fewer than
found on almost every single dive in this study, and all of Hawaii has
only 65 (Fenner, in press). Diversity is only one of several different
desirable attributes for reefs that can be evaluated for considering
desirability for protection. Health and abundance of corals may also be
considered. The pristine nature of the area is an important. The
abundance of large fish (sharks, grouper) on Osprey indicates that it
has had little or no fishing pressure, as these large fish are usually
the first to be removed. At a time when some shark species in Australia
are endangered, this is one of the few places left in Eastern Australia
where abundant natural populations of reef sharks remain. There is a
unique opportunity at Osprey Reef to protect a pristine coral reef, and
maintain its strong attraction for dive tourism.
The high diversity and good health of the corals on the outer slopes of
Osprey Reef and its likely higher total diversity support the effort to
protect this reef. Further, the finding of species not previously found
in Australia at this site, and the finding of what may prove to be a new
species, all support the need to protect this reef.
Acknowledgements
This study was supported by a grant in kind by the Undersea Explorer. I
wish to thank all the staff and crew of the Undersea Explorer for all
there assistance in making this study possible.
References
Done, TJ. 1982. Patterns in the distribution of coral communities across
the central Great Barrier Reef. Coral Reefs 1: 95-107.
Fenner, D. 1999. New Observations on the Stony Coral Species (Scleractinia,
Milliporidae, Stylaseridae) of Belize (Central America) and Cozumel
(Mexico). Bulletin of Marine Science 64: 143-154.
Fenner, D. 2001. Reef corals of the Togian and Banggai Islands, Sulawesi,
Indonesia. P. 18-25 and 63-71 in Allen, G. R. and S. A. McKenna (Eds.),
A marine rapid assessment of the Togean and Banggai Islands, Sulawesi,
Indonesia. RAP Bulletin of Biological Assessment 20, Conservation
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Indonesia. Part II. Comparison of individual survey sites. Appendix 2.
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of the Calamianes Islands, Palawan Province, Philippines. Pages 24-26 in
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Table 1
Great Barrier Reef sites
|
Site |
Dive no’s |
No. species |
Av. No.
sp/dive |
Total Species |
|
Pixie Gardens |
1, 16 |
71, 75 |
73 |
109 |
|
Pixie
Pinnacle |
2, 18 |
88, 87 |
87.5 |
122 |
|
Eagle Rock |
3, 17 |
65, 95 |
80 |
114 |
|
Tracy’s
Wonderland |
12 |
101 |
101 |
101 |
|
Steve’s
Bommie |
13a, 13b |
102 |
102 |
113 |
|
Twin Bommies |
14 |
96 |
96 |
96 |
|
G Spot |
15, 31 |
88, 87 |
87.5 |
117 |
|
Lizard
Island, resort |
22 |
10 |
10 |
10 |
|
Cormorant
Reef |
23 |
53 |
53 |
53 |
|
Cod Hole |
24 |
67 |
67 |
67 |
|
Nursery
Bommie |
30 |
70 |
70 |
70 |
Table 2 Osprey
and Shark Reef sites
|
Site |
Dive No.’s |
No. species |
Av. No.
sp/dive |
Total Species |
|
Admiralty
Anchor |
4, 19 |
66, 68 |
67 |
88 |
|
North Horn |
5, 6, 9, 20 |
56, 54, 72,
60 |
60.5 |
110 |
|
False
Entrance |
7, 21 |
67, 66 |
66.5 |
90 |
|
Raging Horn |
8, 25 |
63, 62 |
62.5 |
93 |
|
West side, N.
Horn |
10, 11 |
85, 77 |
81 |
107 |
|
South Horn |
26 |
80 |
80 |
80 |
|
Shark Reef |
27 |
59 |
59 |
59 |
|
Rapid Horn |
28 |
54 |
54 |
54 |
|
Unnamed Horn |
29 |
48 |
48 |
48 |
Table 3
Comparison of East Australian Reefs with the Coral Triangle
|
Area |
1 dive |
5 dives |
10 dives |
15 dives |
|
Outer GRR |
81.8 |
177 |
205 |
234 |
|
Osprey Reef |
65.9 |
128 |
155 |
172 |
|
E. Australia |
71 |
156 |
213 |
233 |
|
Coral
Triangle |
86 |
189 |
233 |
252 |
Table 4 Corals
found which were not previously reported from Australia
Photo Sample
1. Acanthastrea
brevis x x
2. Acropora brevis x x
3. Acropora globiceps x x
4. Acropora insignis x
5. Echinomorpha nishihirai x
6. Goniastrea minuta x x
7. Leptoseris striata x
8. Montipora verruculosus x
9. Pavona bipartita x x
10. Pocillopora ligulata x x
11. Seriatopora aculeata x x
