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MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?
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Figure 3.
(a)
Seriatopora hystrix
in Amitori Bay, Japan at 30m. (b)
Seriatopora hystrix
off Okinawa Island, Japan at 45m (photos Frederic Sinniger).
Figure 4.
A diverse MCE off Okinawa Island, Japan was recently discovered (Sinniger et al. 2013). (a)
Acropora tenella
at 40 m. (b)
Porites
sp. along with
S. hystrix
,
P. speciosa
,
Dipsastrea
sp. and the zoantharian
Zoanthus sansibaricus
at 40 m (photos Frederic Sinniger).
(a)
(a)
(b)
(b)
Bay (Iriomote Island in the southern part of the Ryukyu
Archipelago),
Leptoseris amitoriensis
is dominant (Veron
1990, Nishihira and Veron 1995), with only a few other species
present
(Figure 2a). This community also corresponds to the
deepest edge of this MCE, as below 55 m sediment blankets
the bottom and no coral communities have been observed.
Above the
Leptoseris amitoriensis
stand, the upper edge of
the mesophotic zone is dominated by
Leptoseris papyracea
(Figure 2b) and a transition towards
Seriatopora hystrix
and a
more diverse shallow coral community (Figure 3a).
The recent discovery of a diverse MCE (Sinniger
et al. 2013),
dominated by species such as
Acropora tenella
,
Seriatopora
hystrix
,
Pachyseris speciosa
and
Porites
sp. (Figure 4),
contrasts with other less diverse MCEs described from the
area (Kimura et al. 2011, White et al. 2013). This finding
of a deep healthy population of
S. hystrix
(Figure 3b), near
a location where this species had disappeared from the
shallow reefs following bleaching events (Sinniger et al.
2013), motivated further studies on the similarities between
upper mesophotic and shallow reef coral fauna, as well as
on the reproductive biology of corals found in local upper
MCEs (e.g. Prasetia et al. 2015). Although the connectivity
between shallow and mesophotic populations of most
species remains to be investigated, this finding is a good
illustration of the potential of MCEs to serve as refugia in
this location (see Chapter 5). Overall, MCEs in the region not
only harbour a high diversity of coral species, but also a wide
diversity of different ecosystems (i.e., ecosystems dominated
by
Leptoseris, Acropora
, or
Pachyseris
). However, little is
known about the factors influencing the coral diversity of
specific MCEs and the distribution of these ecosystems.