J. Jpn. Soc. Soil Phys.
»?>¼No. 33, p. // 0- ,**/ῌ

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Physical and Chemical Properties of the Nest-site Beach of the Horseshoe Crab
Rehabilitated by Sand Placement
Masami OHTSUBO*, Hidekazu ISHIDA**, Hisakatsu MINEI*, Shinya YAMAOKA***and Takahiro HIGASHI** Faculty of Agriculture, Kyushu University, Hakozaki 0ῌ+*ῌ+, Higashi-ku, Fukuoka-shi, Japan** Faculty of Agriculture, Kyushu University (Fukuoka Prefecture at present)*** Graduate School of Bioresource and Environmetal Sciences
AbstractTidal ﬂats in Imazu and Kafuri Bay in Fukuoka Prefecture, Japan, were well known as thenest-sites of horseshoe crabs, but their nesting has declined because of water and sediment
pollution of the bay.

To rehabilitate the polluted beach in the tidal ﬂat, placement of fresh sandon the beach was performed by Fukuoka City, resulting in an increase of nesting of the horseshoe
crab.

We compared the factors that potentially a#ect nesting at Imazu and Kafuri beach :morphology, exposed time, grain-size distribution, water content, oxygen concentration, andredox potential. The elevation of the beach was higher at Imazu than at Kafuri, leading to alonger exposed time at Imazu than Kafuri. This induced low water content, and high oxygen
concentration and redox potential at Imazu compared with Kafuri though the grain-size distribution and organic matter were almost the same at both beaches.

We suggest that sand placement

is an e#ective procedure to rehabilitate nesting sites of the horseshoe crab in terms of exposed
time of the sites, water content, oxygen concentration, and temperature.
Key words : horseshoe crab, nesting, rehabilitation, tidal ﬂat, elevation, dissolved oxygen, redox
potential+    

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concentration in beach and mud ground.

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Soil pH and salt concentration in pore water%

&

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,-421

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*4*+

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+33.

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