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MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?
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The Ryukyu Archipelago in Japan (Figure 1) hosts a large coral
diversity, with species numbers comparable to those found in
the Great Barrier Reef (Spalding et al. 2001). This diversity
results directly from the influence of the Kuroshio Current,
which brings warm tropical water from the Philippines and
equatorial Pacific to the archipelago.
In the late 1960s, MCEs were reported in several locations
off the Archipelago at depths of 30–102 m (Yamazato 1972).
Although only limited samples were obtained and most coral
identification relied on in situ visual observations, specimens
of
Acropora longicyathus
(as
A. syringodes
),
Porites rus
(as
P.
hawaiiensis
),
Dipsastrea
speciosa
(formerly
Favia speciosa
),
Goniastrea
sp. and
Pachyseris speciosa
were collected in the
depth zone of 70–100 m.
Leptoseris scabra
and
Leptoseris
spp. were reported between 50 m to 100 m, with
L. scabra
extending no deeper than 70 m.
Recent studies indicate that several MCEs at the upper edge of
the mesophotic zone (around 30 m depth) are characterized
by high coral cover and the dominance of a single/few species.
For example, a community dominated by
Acropora horrida
was found in Kume Island, while
Pachyseris foliosa
was
dominant at an MCE in Okinawa Island (Kimura
et al. 2011,
White et al. 2013).
Low diversity and high cover examples can also be found in
other depth ranges. For example, at 45–50 m depth in Amitori
3.9.
Ryukyu Archipelago, Japan
Frederic Sinniger
, University of Ryukyus, Japan
Land area
Depth contours
0 30 60 90
30 metre
Known MCEs
150 metre
Kilometre
Sakishima
Islands
Okinawa
Islands
Figure 1.
Location of MCEs of the Ryukyu Archipelago, Japan (source GRID-Arendal).
Figure 2.
Dominant corals in Amitori Bay, Japan. (a)
Leptoseris amitoriensis
at 48 m (photo Giovanni Casari). (b)
Leptoseris papyracea
at
30 m (photo Frederic Sinniger).
(a)
(b)