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Title: Water-Quality Variables across Sekisei Reef, A Large Reef Complex in Southwestern Japan. 
Author: Morimoto, Naoko; Furushima, Yasuo; Nagao, Masayuki; Irie, Takahiro; Iguchi, Akira; Suzuki, Atsushi; Sakai, Kazuhiko
Date: 2010-01
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.
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
Series/Report No.: vol. 64, no. 1
Description: v. ill. 23 cm. Quarterly
Pages/Duration: 12 p.
ISSN: 0030-8870
URI: http://hdl.handle.net/10125/23094
LC Subject Headings: Natural history--Periodicals.
Science--Periodicals
Natural history--Pacific Area--Periodicals.

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