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Water-Quality Variables across Sekisei Reef, A Large Reef Complex in Southwestern Japan.

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Title:Water-Quality Variables across Sekisei Reef, A Large Reef Complex in Southwestern Japan.
Authors:Morimoto, Naoko
Furushima, Yasuo
Nagao, Masayuki
Irie, Takahiro
Iguchi, Akira
show 2 moreSuzuki, Atsushi
Sakai, Kazuhiko
show less
LC Subject Headings:Natural history--Periodicals.
Natural history--Pacific Area--Periodicals.
Date Issued:Jan 2010
Publisher:Honolulu, University of Hawaii Press
Citation:Morimoto N, Furushima Y, Nagao M, Irie T, Iguchi A, Suzuki A, Sakai K. Water-Quality Variables across Sekisei Reef, A Large Reef Complex in Southwestern Japan. Pac Sci 64(1): 113-124.
Series:vol. 64, no. 1
Abstract:At Sekisei Reef in southwestern Japan (24_ N), coral cover dramatically decreased in the mid-1980s, probably due to a population outbreak of the coral predator Acanthaster planci. Coral communities subsequently recovered well outside the semiclosed lagoon, but recovery has been poor inside it. Hence, water-quality degradation including eutrophication has been a concern inside the lagoon. In addition, temporal variation in eutrophication parameters is common among high-latitude coral reefs, resulting in difficulties in evaluating them. Therefore, to address these issues, we monitored temperature, salinity, turbidity, chlorophyll-a, NOx -N (NO3-N þ NO2-N), and NH4-N concentrations year-round across the lagoon at Sekisei Reef. Turbidity and NOx-N concentration increased with increasing wind velocity, suggesting that variation in turbidity and NOx-N concentrations was attributed to resuspension of bottom sediments, and NOx-N release through regeneration processes of microorganisms from the sediments and reef frameworks, respectively. In contrast, variation in chlorophyll-a and NH4-N concentrations appears to be mainly controlled by the seasonality of temperature and irradiance. Long retention time of seawater inside the lagoon seems to have enhanced NH4-N assimilation and increase of phytoplankton during summer. Inside the lagoon, turbidity, NOx-N, and summer chlorophyll-a concentrations were higher, and variation in temperature was larger than outside it. Although water quality appears not to be seriously degraded, multiple effects of these water-quality variables might have negatively affected recovery of coral communities inside the lagoon. Recent expansion
Description:v. ill. 23 cm.
Pages/Duration:12 p.
Appears in Collections: Pacific Science, Volume 64, Number 1, 2010

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