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Seasonal and bleaching‐induced changes in coral reef metabolism and CO 2 flux
Author(s) -
Kayanne Hajime,
Hata Hiroshi,
Kudo Setsuko,
Yamano Hiroya,
Watanabe Atsushi,
Ikeda Yutaka,
Nozaki Ken,
Kato Ken,
Negishi Akira,
Saito Hiroshi
Publication year - 2005
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2004gb002400
Subject(s) - diel vertical migration , reef , seawater , seasonality , coral reef , coral , oceanography , environmental science , flux (metallurgy) , zoology , biology , ecology , chemistry , geology , organic chemistry
Monitoring seawater CO 2 for a full year with seasonal observations of community metabolism in Ishigaki Island, Japan, revealed seasonal variation and anomalous values owing to the bleaching event in 1998. The daily average p CO 2 showed a seasonal pattern on an annual scale, 280 to 320 μatm in winter and 360 to 400 μatm in summer, which was determined primarily by the seasonal change in seawater temperature. By contrast, the range in the diel variation in p CO 2 , 400 to 500 μatm in summer 200 to 300 μatm in winter, was attributed to the seasonal variation in community metabolism: Gross primary production ( P g ) and respiration ( R ) were high in summer and low in winter. During the 1998 bleaching event, although P g and R increased, community excess organic production ( E ) decreased by three quarters compared with the same month in 1999, when the coral community showed high recovery. This change in metabolism led to large diel range and increased average value of p CO 2 levels in the seawater on the reef flat. The decrease in the range and increase in the average value of p CO 2 were observed by monitoring the Palau barrier reef flat, where overall mortality of corals occurred after the bleaching. All the metabolic parameters, P g , R , E and calcification ( G ) were reduced by half after the bleaching, which increased the average p CO 2 value by 10 μatm and decreased its diel range from 200–400 μatm to 100–200 μatm. Bleaching and resultant mortality of coral reefs led to degradation of their metabolic performance, and thus resulted in the loss of their active interaction with the carbon cycle.