Tokyo
: sep 2003, 11th International Symposium on Phototrophic
Prokaryotes : Phototrophic
prokaryotes in
Bora
Bay, Miyako
Island
, Okinawa
, Japan
)
*Beatriz
E. Casareto ; **Loic Charpy; ***Jean Blanchot and ****Yoshimi
Suzuki.
*
Laboratory of Aquatic Science and Consultant Co., LTD, Meishin
BLDG., Kamiikedai
1-14-1
, Ota-ku,
Tokyo
145-0064,
Japan
. e-mail: CASARETOBE@aol.com
**IRD CO Marseille, France
*** IRD La Réunion, France
**** Department of Biology and Geosciences, Faculty of
Sciences, Shizuoka University, Oya 836, Shizuoka, 422-9529,
Japan
High
contributions of phototrophic prokaryotes were reported in
different coral reef ecosystems:
French Polynesia
atoll lagoons, Great Astrolabe reef (
Fiji
),
Great Barrier Reef
(
Australia
),
New Caledonia
lagoon. In these oligotrophic ecosystems,
contrary to the open ocean, Synechococcus largely
dominate Prochlorococcus. The questions are:
Are
phototrophic prokaryotes every where dominant in coral reef
ecosystems?
What
is the influence of coral reef environment onto prokaryotes
composition and dominance?
Are
prokaryotes grazed by coral reef communities?
To
try to answer these questions, we studied the phytoplankton of
Bora
Bay
(
Miyako
Island
,
Okinawa
,
Japan
). Indeed, this ecosystem is located in the
North hemisphere and it can be considered as mesotrophic
thanks to nutrient rich ground waters input in the lagoon. In
addition, the lagoon area is small compared to the reef area.
|
In
Miyako, we found a phytoplankton community structure
very similar to other coral reef lagoon, with 60% of
cells with a size less than 3 µm. Lagoonal waters
were dominated by Synechococcus, meanwhile in
the open ocean waters the smallest coccoid
cyanobacteia Prochlorococcus reach the same
abundance as that of Synechococcus. A
significant decrease in coccoid cyanobacteria
abundance was observed close to the barrier reef. The
hypothesis that coral reef communities are able to
graze on picoplankton was confirmed during dome
experiments. |
|
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